Innovative color CT scanner with European particle detection technology
Researchers from New Zealand have developed an almost space-age color CT scanner called MARS
(Medipix all resolution system). The MARS scanner carries a Medipix X-ray detector chip that counts
photons and classifies them by energy level, thereby permitting spectroscopic (or spectral) imaging
and the creation of color images. The detector chip, developed in a collaboration between the
European Organization for Nuclear Research (CERN) and 18 research groups worldwide, is based on
CERN particle detector technology used for high-energy physics. Prototype MARS scanners are now
available in North American laboratories for clinical testing.
Preliminary results with the MARS scanner, tested on phantoms and small animals, were
presented at this year's annual meeting of the Radiological Society of North America (A.P.H. Butler
et al., conference presentation code SSC16-01). The “multi-energy” scanner was shown to distinguish
contrast agents of different compositions (e.g. iodine, barium, gadolinium). The scanner can also
apparently distinguish contrast agents from diverse biological tissues. The researchers predict
that this innovative color CT scanner will improve diagnostic imaging, facilitate the development
of new applications, and make CT scanning faster and safer. More information about the MARS-CT
project is available at
wiki.canterbury.ac.nz.
by V. Matarese
Selected literature update
Seminal 2006 MDCT book now available in updated forms
The book
MDCT: A Practical Approach, edited by distinguished radiologists Saini, Rubin and Kalra
and published by Springer in 2006, was reissued in 2008 in a revised and expanded version. The
original volume was organized in five sections, beginning with “Physics and techniques of MDCT” and
then progressing through the major areas of clinical application: abdomen, cardiovascular system,
head and neck, and trauma.
The new volume, called
MDCT: From Protocols to Practice, has the same editors and maintains the same structure.
However, the original chapters have been updated, several sections have been expanded with new
chapters, and a small section on pediatric MDCT has been added. The new volume, like its
predecessor, ends with an appendix reporting state-of-the-art imaging protocols.
by V. Matarese
New U.S. FDA recommendations for avoiding accidental radiation overdose during MDCT
perfusion examinations
In early December 2009, the US Food and Drug Administration (FDA) issued interim practice
recommendations for MDCT facilities performing perfusion imaging [
1]. The initiative was prompted by the notification of over 250 cases
of radiation overdose during brain perfusion examinations. According to a safety alert released in
October 2009 [
2 ], 206 patients at one Californian hospital received about 8-times
the normal radiation dose (maximum, 0.5 Gy to the head). The error came to the attention of
physicians when patients complained of alopecia and erythema. Through FDA investigations, an
additional 50 cases have been identified in California, and other states have reported possible
cases of radiation overdose.
The medical error does not seem to be linked to the scanner, as patients had been imaged
with instruments produced by two manufacturers. Although the exact cause is currently unknown, one
may surmise from the FDA recommendations and from reporting in the general press that the error was
operator-dependent, due to the use of incorrect scanner settings.
The FDA recommendations, which apply to all CT perfusion studies, emphasize quality
assurance. In particular, the FDA recommends that CT facilities review imaging protocols to check
that the radiation doses are correct and that they implement quality control procedures to
guarantee that protocols are followed. Moreover, technologists are cautioned to check scanner
settings before each study, while manufacturers are encouraged to improve user training.
CT expert honored as the 2009 RSNA Outstanding Educator
The presentation of two prestigious radiology awards marked the opening of the 95th annual
meeting of the Radiological Society of North America (RSNA), recently held in Chicago. During the
opening session, the RSNA honored two senior radiologists who have made significant contributions
throughout their careers in the fields of radiological education and research.
The 2009 RNSA Outstanding Researcher award was given to Sanjiv Sam Gambhir, professor of
radiology and bioengineering at Stanford University. Dr. Gambhir is a world leader in molecular
imaging, especially for his development of a Raman nanomolecular imaging approach.
The recipient of the RSNA Outstanding Educator award this year was Dr. Elliot K. Fishman,
professor of radiology at Johns Hopkins University and director of diagnostic imaging and body CT
at the Johns Hopkins Hospital. Also at Johns Hopkins, Fishman heads the Advanced Medical Imaging
Laboratory (AMIL), which aims to improve patient care through research and educational activities,
especially regarding spiral CT and 3D imaging technologies. Of the over 800 papers in Medline
authored by Dr. Fishman, more than two dozen address the training of radiologists, especially
regarding the use of web-based tools.
MDCT scoring systems for interstitial lung diseases: possible use in primary graft
dysfunction in lung transplant recipients
The high resolution of 64-slice MDCT has permitted the development of semiquantitative scales
for grading the severity of lung pathologies. Most work thus far has focused on the grading of
cystic fibrosis, adult respiratory distress syndrome and idiopathic pulmonary fibrosis. There is
presently no CT-based scoring system for primary graft dysfunction (PGD), a common early
complication of lung transplantation that adversely affects graft success and long-term clinical
outcomes. A diagnosis of PGD is currently based on the results of plain radiography and lung
function tests. A sensitive imaging test to grade and localize PGD could positively impact the care
of lung transplant recipients.
Recognizing the need for a PGD scoring system, researchers at Copenhagen University Hospital
systematically reviewed existing CT-based scales for interstitial lung diseases. Their paper,
published in
Interactive Cardiovascular and Thoracic Surgery [
1], summarized each scale's parameters and reported values of
sensitivity, inter- and intraobserver variability, and reproducibility. From this analysis, they
devised a 9-parameter MDCT scoring system for PGD, to be applied to each pulmonary lobe in central
and peripheral zones; four additional CT findings outside the lung are also scored. The new scale
will be tested clinically in 70 consecutive lung transplant recipients at Rigshospitalets in
Copenhagen.
Selected literature update
Diagnostic performance of MDCT for gastrointestinal diseases
Two papers selected in October for MDCT.net's literature database examined the performance of
MDCT in diagnosing gastrointestinal (GI) pathology. Both papers were contributed by researchers
from Sapienza University in Rome.
Frattaroli and colleagues [
1] examined the use of MDCT in determining the site and etiology of
acute GI bleeding in 29 patients with suspected bleeding. Patients underwent both contrast-enhanced
16-slice MDCT and endoscopy (upper endoscopy or colonoscopy, depending on clinical signs). For
MDCT, bleeding was defined as extravasation of contrast material into the GI tract. Sensitivity was
calculated by accepting as true diagnosis either: (i) the diagnosis made during surgery or autopsy,
or (ii) the diagnoses given by the two investigated methods when they were in agreement. In 11
patients with upper GI disease, MDCT had a sensitivity of 100% and 90.9%, respectively, in
identifying the site and etiology of the bleeding. In 17 cases with lower GI disease, these values
were 100% and 88.2%. Based on these encouraging results, the authors proposed a diagnostic protocol
in which these patients first undergo MDCT and then, only if findings are negative despite
persistent bleeding, also endoscopy.
Anzidei and coworkers [
2 ] compared the diagnostic performance of contrast-enhanced 64-slice
MDCT and 1.5 T MRI in 40 patients with an endoscopic diagnosis of gastric cancer, using as final
diagnosis the results from histopathological analysis of surgical specimens. The study confirmed
the high accuracy and sensitivity of MDCT (both 89.4%) in the local staging of advanced tumors (T3
and T4) and demonstrated that MRI has an equivalent diagnostic performance.
ACR position statement: CT colonography is ready for community practice
Last month, the American College of Radiology (ACR) issued revised practice guidelines on the
use of CT colonography in adults [
1]. This was accompanied by a position statement [
2 ] from the ACR Colon Cancer Committee, author of the guidelines, in
which state-of-the-art knowledge on CT colonography was reviewed and the scientific rationale for
the guidelines was explained.
Briefly, based on current evidence, the ACR Colon Cancer Committee has determined that CT
colonography – when performed according to the latest technical standards – is equivalent to
optical colonoscopy in detecting advanced neoplasia. Given continuing technological improvements in
CT, the diagnostic performance of this examination is expected to improve further. Based on its
safety profile, the authors considered this diagnostic method as both an “effective adjunct to
colonoscopy” and a “frontline option” for screening adults with average risk for colorectal cancer,
starting at age 50 years. Persons in whom polyps ≥6 mm are found should have colonoscopy and
polypectomy, and may benefit from surveillance with CT colonography.
The ACR's position is that CT colonography is now ready for routine use in the community.
Critical issues for its effective implementation outside of the controlled research environment
include the training of radiologists and the development of reliable quality control measures.
Inclusion of CT colonography in public and private healthcare plans will depend on the
demonstration of cost-effectiveness in different national settings together with a better
understanding of the health risks from radiation exposure during the examination.
CT technologies rank high among 2009 Minnies awards
CT technologies and applications placed well in the 2009 Minnies awards for radiological
excellence. In particular, coronary CT angiography was considered the hottest clinical procedure,
and Siemens Healthcare's Somatom Definition Flash CT scanner was deemed the best new radiological
device (with Toshiba's Aquilion Premium CT scanner in second place). A report on 64-slice CT
angiography in patients with chest pain (Fazel et al., Am J Cardiol) took second place in the best scientific
paper category. CT was also behind the best new radiological software, with Vitrea Enterprise Suite
(Vital Images) and ASIR dose reduction software (GE Healthcare) in first and second places,
respectively.
The Minnies is a series of awards for radiological excellence given by Auntminnie.com, an
online community for radiologists and medical imaging professionals. Candidates for the Minnies are
nominated by the website's registered visitors, while winners are chosen by an expert panel. Awards
are given in 13 categories that recognize influential persons, new technologies, current
radiological issues, leading institutes, the hottest clinical procedure and the best scientific
paper of the year. This year's Minnies winners were announced at the end of October.
320-slice MDCT for coronary stent analysis: ongoing trial
Patients with coronary artery stents require follow-up angiography so that the long-term
outcomes of the procedure can be assessed and that re-stenosis and disease progression in other
coronary segments can be monitored. Despite the great interest in developing a noninvasive imaging
method to assess coronary stents, a meta-analysis published in 2008 concluded that 16- to 64-slice
MDCT angiography was insufficiently sensitive (82%) for this clinical indication (
see MDCT.net news of August 2008 ) [
1 ]. Recent studies using 64-slice MDCT have achieved greater
sensitivity values, but problems due to blooming and motion artifacts remain [
2 ].
Researchers at Charité University in Berlin, Germany, led by Dr. Marc Dewey, are undertaking
a prospective clinical study to determine if 320-slice MDCT angiography has sufficient diagnostic
accuracy to be used in the evaluation of coronary artery stents. The Coronary Artery Stent
Evaluation with 320-slice Computed Tomography (CARS 320) study began in April 2009 and is currently
recruiting 90 patients aged 40 years or older who require conventional coronary angiography for
suspected in-stent restenosis. The trial has been registered at the US National Institutes of
Health's clinical trial registry (clinicaltrials.gov).
Within Europe and the Mediterranean area, the professional meeting point for pediatric
radiologists is the European Society of Paediatric Radiology (ESPR,
www.espr.org). This association aims to promote excellence in pediatric
imaging by offering opportunities for continued learning in clinical and scientific areas.
The ESPR organizes an annual meeting and postgraduate course which, in 2009, was held in
Istanbul; next year's meeting will be in Bordeaux. At these meetings, ESPR acknowledges its
leading members with a series of awards, including a gold medal for life-long service to the field
as well as several research awards. ESPR also hold an annual course in pediatric radiology: this
year's course in Amsterdam was devoted to gastrointestinal and urogenital imaging, while next
year's course in Florence will focus on heart and chest imaging. The ESPR and the US-based Society
of Pediatric Radiology hold a joint international meeting every 5 years; the next such
meeting is planned for 2011 in the UK. These two societies, plus similar associations from
Asia and Latin America, work with Springer to produce the journal Pediatric Radiology (see also
MDCT.net selected literature archive).
by V. Matarese
Selected literature update
LV function analysis in patients with mitral valve regurgitation: value of 64-slice
MDCT
In primary mitral regurgitation, valvular abnormalities cause the valve to leak, leading to
stress on the left ventricle (LV) that may result in permanent damage. Accurate assessment of LV
function is essential to determine a patient's prognosis and to guide decision-making about surgery
to repair or replace the value. LV function has typically been studied with echocardiography,
although the reference method today is cardiac MRI. Early studies using 4- and 16-slice MDCT did
not achieve a satisfactory level of accuracy for this purpose. Therefore, researchers from Sichuan
University in China tested the possibility of using 64-slice MDCT to evaluate LV function in
patients with mitral regurgitation.
In the study, 51 consecutive patients with mitral regurgitation, often with other heart
conditions, underwent trans-thoracic echocardiography (2DTTE) and, a few days later, both 64-slice
MDCT and MRI. MDCT was performed with retrospective ECG gating and contrast enhancement,
during a single breath hold. Myocardial mass and LV function parameters were calculated
and compared between MRI and the two other diagnostic methods. In particular, MRI and
MDCT gave similar values of end-diastolic and end-systolic volumes, stroke volume, ejection
fraction and myocardial mass, with a high intrapatient correlation between the two techniques
(Pearson's r, 0.89-0.96). The authors concluded that 64-MDCT can be used to accurately assess
LV function and is especially useful in those patients with limited breath-holding ability or in
whom MRI is contraindicated (see also MDCT.net selected literature archive).
MDCT for measuring aortic valve area: meta-analysis
Stenosis of the aortic valve is a degenerative condition often associated with coronary artery
disease. The severity of this condition is typically assessed from the aortic valve area measured
using transesophageal echocardiography (TEE) or cardiac catheterization, although recently several
studies have described the use of electrocardiography-gated MDCT for this purpose. Researchers from
the Cleveland Clinic Florida did a meta-analysis to determine the diagnostic accuracy of MDCT for
aortic valve area measurements [
1 ].
The meta-analysis included 9 studies that assessed aortic valve area using 16-slice or
higher MDCT and also TEE as the reference standard. Altogether, the studies included 437 patients,
most of whom had known aortic stenosis. These patients had aortic valve areas that ranged from 0.1
to 2.0 cm2 (normal value, about 3 cm2) irrespective of the diagnostic technique. The mean value
obtained with MDCT was 1.0 cm2 while that with TEE was 0.9 cm2. There was a strong correlation in
the intra-individual results between the two methods (Pearson's r=0.89). The authors concluded that
MDCT is “feasible and reasonably accurate” for measuring aortic stenosis and therefore recommended
it as a supplementary method, especially when TEE is not diagnostic.
Selected literature update
MDCT for abdominal emergencies
Two retrospective studies published in August 2009 and selected for inclusion in MDCT.net's
literature archive addressed the use of abdominal 4- or 16-slice MDCT in emergency situations.
Researchers from Bari assessed the prognostic value of contrast-enhanced MDCT in 27 patients
with bowel infarction due to arterial or venous occlusive ischemia [
1 ]. Mortality was significantly higher among patients with arterial
infarctions (88% vs. 11%). MDCT permitted a correct diagnosis of the arterial or venous nature of
the infarction in all cases. Moreover, specific CT findings were associated with prognosis, e.g.
pneumoperitoneum and intramural pneumatosis were predictive of a fatal outcome whereas wall
thickening was more commonly seen in patients with good outcomes. The authors recommended MDCT for
all patients with acute abdomen due to its high diagnostic and prognostic value.
Researchers from Baltimore studied the diagnostic accuracy of triple-contrast-enhanced MDCT
in 136 patients with a suspicion of penetrating trauma to the diaphragm [
2 ]. MDCT was performed at admission to a trauma center, and
diaphragmatic injury was confirmed during surgery in 47 cases. Blinded radiologists evaluated CT
images for six signs; they accurately identified diaphragmatic injury in 41 patients (sensitivity,
87%) and excluded such injury in 71 cases (specificity, 72%). Considering individual CT findings,
the sign of contiguous injury on either side of the diaphragm had the best diagnostic accuracy.
The next European Congress of Radiology (ECR) will be held in Vienna on 4-8 March 2010. It will
be presided by Dr. Małgorzata Szczerbo-Trojanowska (Lublin, Poland), who discussed the key topics
of ECR 2010 earlier this year in an interview with ECR Today [
1 ].
According to Szczerbo-Trojanowska, the thematic focus of ECR 2010 will be on imaging in
oncology and in clinical emergencies. The coming meeting will introduce a new type of session,
called “Organs from A to Z”, which will debut by focusing on the liver. Another innovation is the
introduction of multidisciplinary symposia designed to help radiologists update their clinical
knowledge; at ECR 2010, there will be four such sessions in which pulmonary, colorectal, prostatic
and uterine-cervical cancer are each discussed from the viewpoints of a surgeon, an oncologist and
a radiologist. Several sessions will address state-of-the-art applications of computed tomography,
such as functional CT, cardiothoracic CT, volumetric CT and CT colonography.
The programming committee is still accepting abstracts for presentations and posters
(deadline, 18 September). Online registration is now possible, and the discounted fee for early
registration is available until 10 November. The preliminary program, replete with interviews and
special topic articles, is now online:
www.myesr.org.
Founded in 1906, the Royal Belgian Radiological Society has three main objectives: to promote
basic and clinical research in radiology, to disseminate scientific knowledge about radiology, and
to support the education of its members. The association is currently presided by Dr. G. Villiers
and is structurally organized into nine thematic sections. Each year, the association holds an
annual symposium and several meetings organized by the individual sections. This year's symposium
is dedicated to genitourinary radiology and will be held in Ghent in November; an honorary lecture
on emergency imaging in pregnant women will be given by S. Goldman of Houston.
The society publishes a bimonthly journal
JBR-BTR (formerly, the
Journal Belge de Radiologie - Belgisch Tijdschrift voor Radiologie), in English, French
and Dutch languages. The journal is indexed in Medline and freely available in full text since 2001
through the society's website
www.rbrs.org.
Acute chest pain: towards development of a diagnostic and prognostic algorithm
Acute chest pain requires a rapid and reliable diagnosis to determine if a patient is at risk
for myocardial ischemia or infarction. For this purpose, there are numerous tests based on specific
signs and symptoms, laboratory determinations and diagnostic images, although the best combination
of these methods is unknown. Researchers at the University Medical Center of Groningen, The
Netherlands, are conducting a 3-year prospective study to evaluate a diagnostic algorithm for the
quick identification of high-risk patients among those who present with acute chest pain [
1 ].
The algorithm begins with a clinical workup, including electrocardiography and 21 standard
laboratory tests, which permits classification of patients into 4 groups: myocardial infarction,
chest pain with high probability of acute coronary syndrome (ACS), chest pain with low ACS
probability, and non-cardiac chest pain. Patients with infarction are treated in hospital, while
those with chest pain of a presumed cardiac origin undergo electron beam tomography and, in case of
high calcium score, also 64-slice contrast-enhanced CT angiography. Blood samples are taken for
determination of ACS biomarkers.
The primary objective of the study is to determine if myocardial ischemia or a future
cardiac event can be ruled out based on the calcium score, biomarker profile or imaging findings;
the secondary objective is to identify the combination of clinical signs and symptoms, biomarkers
and imaging findings that best predicts the prognosis of patients with acute chest pain. The
methods and rationale for the study have been reported [
1 ]; the first results are expected later this year.
Among articles selected this month for inclusion in MDCT.net's literature archive are two
reports of studies that compared MDCT to standard methods for assessing respiratory pathology.
Italian researchers focused on quantifying the fibrotic damage from chronic obstructive
pulmonary disease in 30 patients [
1 ]. They prospectively compared automated whole-lung densitometry to
visual assessment of 16-row MDCT images, elaborated according to two different post-processing
algorithms. In particular, densitometry was done on 5-mm slices taken at 5-mm increments over the
entire lung and reconstructed with a smooth filter; visual assessment used a 1-mm thickness but
considered one of every ten slices taken at 1-mm increments and reconstructed with a sharp filter.
Automated densitometry took longer but was more reproducible than visual assessment. Both methods
correlated moderately but significantly with a respiratory function test. The authors recommended
the automated method for its greater reproducibility.
Researchers from South Africa studied airway compression due to tuberculosis in 26 children
aged 4-84 months [
2 ]. They retrospectively assessed the ability to identify and grade
sites of compression using 4-slice contrast-enhanced MDCT with three-dimensional visual rendering.
MDCT permitted the identification of almost 60% more sites than did flexible bronchoscopy, the
reference method. For sites identified by both tests, agreement on the degree of narrowing was
moderate (k=0.39). Compared to bronchoscopy, MDCT had a 92% sensitivity and an 85% specificity for
identifying airway compression. The authors concluded that MDCT is complementary to bronchoscopy in
evaluating airway obstruction in children.
Diagnostic imaging and pregnancy: revised UK guidelines
The UK Health Protection Agency, together with the Royal College of Radiologists and the College
of Radiographers, has recently updated its 1998 guidelines on the use of diagnostic imaging
involving ionizing radiation in women of childbearing age. The 24-page document, entitled “
Protection of Pregnant Patients during Diagnostic Medical Exposures to Ionising Radiation” [
1 ], is targeted to hospital physicians working in radiology and
nuclear medicine.
The first part of the report summarizes scientific evidence on the fetal health effects of
in utero exposure to radiation. During normal imaging procedures, an embryo or fetus is unlikely to
suffer direct tissue damage resulting in death or malformation (deterministic effects), as long as
the exposure remains below a 100 mGy threshold. Low levels of radiation, however, may cause gene
mutations leading to childhood cancer or hereditary diseases. For these stochastic effects, there
is no recognized safety threshold and the risk is directly associated with the radiation dose. To
illustrate this fact for childhood cancer, the authors grouped common diagnostic imaging procedures
that pregnant women may undergo into 5 categories ranging from low-exposure examinations with low
fetal risk (e.g. dental X-ray and mammography) to high-exposure examinations with high fetal risk
(e.g. pelvic CT and whole body 18F-PET-CT). Examinations in the higher exposure categories may
double the risk of childhood cancer and thus should be avoided whenever possible. Compared to the
risk of cancer, the risk of heritable effects from an in utero exposure to radiation was so low as
to be considered negligible.
The second part of the document offers guidance on the safe use of diagnostic imaging in
pregnant women and in women who could have an as yet unrecognized pregnancy. The report also
briefly addresses the medical-professional issues raised when a fetus is inadvertently exposed to
radiation.
Head and neck radiology: a conference and course in Verona
The European Society of Head and Neck Radiology (ESHNR) will hold is twenty-second annual
meeting and refresher course on 1-3 October 2009 at Palazzo della Gran Guardia, in Verona, Italy.
The meeting has been organized by Dr. Roberto Maroldi (Brescia) together with an international
scientific committee and with the support of the European Society of Neuroradiology and six Italian
medical associations.
The three-day program will address the pathology, treatment and imaging of head and neck
diseases, including lymph node metastases, nose and sinus tumors, squamous cell carcinoma of
larynx, inner ear disease, temporomandibular joint and facial pain, bone tumors, salivary and
orbital lesions, neurogenic tumors, and trauma. The afternoon of the third day will be dedicated to
a refresher course on head and neck anatomy and pathology. Almost 50 speakers from all of Europe
and Australia have been invited to give the plenary and parallel sessions. A full program and
registration information are available at
www.eshnr2009.org.
Radiation dose reduction in cardiac CT angiography: impact of a best-practice imaging
program
Cardiac CT angiography can expose a patient to a substantial amount of radiation but, as
revealed by the PROTECTION I study [
1 ], the actual dose varies widely and depends on the choice of scanning
parameters and on each patient's characteristics. Dose-reduction techniques are available but are
not used consistently, possibly for lack of awareness or for concerns about image quality.
The Advanced Cardiovascular Imaging Consortium, comprising imaging centers in Michigan,
devised a best-practice program to train radiologists in dose-reduction techniques and investigated
the impact of this program on patients' radiation exposures [
2]. The year-long study had three phases: (i) a 2-month run-in period in
which scanning practices and radiation doses were monitored, (ii) an 8-month intervention period in
which participants were trained to apply an evidence-based best-practice model for CT angiography
acquisition, and (iii) a 2-month follow-up period. Overall, 15 centers participated and data from
4862 patients were analyzed, including 620 during the run-in and 835 in the follow-up.
In the run-in period, median dose-length product was 1493 mGy · cm (interquartile range
(IQR), 855-1823) and effective dose was 21 mSv (IQR,12-26). During the training program these
values fell by more than 50%, to 697 mGy · cm (IQR, 407-1163) and 10 mSv (IQR, 6-16), respectively,
in the follow-up period (p<0.001). The rate of diagnostic-quality exams increased slightly (from
89% to 92%, p=0.07) while the median scan quality score remained the same. The most important
factor in reducing radiation dose was use of low tube voltage (100 kVp) in patients ≤85 kg with a
body mass index <30 kg/m
2.
This prospective study confirmed that patients who undergo cardiac CT angiography are
exposed to a high but variable radiation dose and that this exposure can be modulated by an
accurate choice of scanning parameters. The study also demonstrated that an evidence-based
best-practice algorithm for choosing scan parameters is effective and that a collaborative quality
improvement program, offered to small and large imaging centers over a large geographical area, can
be successful.
CT colonography: technical improvement and new application
Among the articles added this month to MDCT.net's literature database, two describe developments
in CT of the colon.
Juchems and colleagues from Ulm, Germany, together with researchers at Philips Medical
Systems, tested an electronic colon cleansing software for digital subtraction of opacified fluid
and barium-tagged feces in the colon [
1 ]. Using optical colonoscopy as the gold standard, the researchers
compared the diagnostic accuracy of 4- or 8-slice MDCT colonography without and with the cleansing
algorithm, on an archive of 79 datasets from patients with colonic polyps. The software favorably
impacted on the sensitivity of detecting polyps by two blinded readers.
Researchers from the Mayo Clinic in Arizona investigated the accuracy of diagnosing colitis
with 8-slice MDCT enterography and both oral and intravenous contrast agents [
2 ]. This retrospective study evaluated data from 35 patients without and
35 with colonoscopy-confirmed ulcerative or Crohn's colitis. Overall sensitivity was 74%, but this
increased to 89% in the subgroup of patients with excellent colon distension and to 93% in patients
with moderate-severe disease. Accuracy in classifying disease activity as mild, moderate or severe
was limited, suggesting the need to improve imaging protocols for this application.
Clinical guidelines for the emergency management of chest pain call for the use of coronary MDCT
angiography as a supplemental test, after an observation period, for individuals with a low
probability of acute coronary syndrome [
1 ]. Researchers from Tel Aviv, Israel, reported their experience with
64-slice CT angiography in the workup of patients with chest pain [2]. In their practice, patients
are monitored in a chest pain unit for 12 h with electrocardiography and cardiac troponin
determinations, and then are directly hospitalized or discharged or undergo noninvasive testing
with myocardial perfusion scintigraphy (MPS) or CT angiography, depending on clinical
characteristics and instrumental availability.
The report describes the evaluation of 785 patients with acute chest pain who, after
observation, were hospitalized (42 cases) or discharged (44 cases), or underwent further imaging
with MPS (359 cases) or CT angiography (340 cases). Patients in the MPS group were older and had
worse clinical conditions, because this group included persons with contraindications to CT
angiography. However, similar proportions of patients (89% and 90%, respectively) were discharged
after imaging due to absence of major disease. In the follow-up period, a similar proportion of the
discharged patients experienced repeat chest pain (33% and 28%, respectively) and a few patients
were readmitted for suspected cardiovascular chest pain (3 and 15, p=0.01). The authors suggested
that MDCT angiography could be part of the emergency investigation of acute chest pain in
accurately selected patients.
The International Cancer Imaging Society will hold its ninth annual teaching course and annual
meeting in Salzburg, Austria, on 1-3 October 2009. The program is focused on the multidisciplinary
management of cancer. A first keynote lecture on the use of CT colonography for cancer screening
will be given by J.P. Heiken of Washington University School of Medicine. Another keynote lecture
on the development of practice guidelines for cancer will be given by L. Ollivier from the Institut
Curie. Scientific sessions will address imaging applications for tumors of the brain, spine and
lung, pediatric imaging, the management of incidental lesions, imaging applications for oncological
emergencies, and tumor ablation. Two hands-on workshops will be given on CT colonography and
diffusion-weighted MRI, while other workshops will focus on the female pelvis, pancreatic cancer,
molecular imaging, and the diagnosis of abdominal tumors. A full program and registration
information are available at
www.icimagingsociety.org.uk
A study on 294 patients administered with either ipopamidol or iodixanol and followed up for 1
year or longer showed a higher rate of long term cardiovascular adverse events (AEs) in patients
experiencing CIN [1]. Randomization to iopamidol reduced both the incidence of CIN and the rate of
major AEs.
The seventh European Course of Cardiac CT and MR (CardioCTMR) was held on 11-12 June 2009, in
the center of Paris at the Maison de la Chimie. Over one and a half days, experienced radiologists
and cardiologists from five European countries and the United States gave high quality lectures on
the state-of-the-art in both cardiac CT and MRI. This was a refresher course for getting up to date
in a friendly atmosphere.
The first half-day of the course focused on coronary artery imaging, mainly with CT.
Although the complimentary role between cardiac CT and cardiac MRI is now obvious, CT at the
present time seems to be the more reliable technique for visualizing the coronary arteries in a
noninvasive fashion. The next morning concerned the myocardium, valves and aorta, and included an
outstanding presentation on imaging for percutaneous treatment of aortic stenosis by Prof. J.N.
Dacher from the University Hospital of Rouen, a pioneering center for this new technique. Finally,
the last afternoon of the course dealt with technical issues and included a manufacturers' session
which showed the near future beyond 64-slice CT technology and 1.5 T MR imaging.
This successful meeting was highly appreciated by 250 attendees specialized in this field,
from 15 countries in Europe and even beyond. The next course will be held in the same location, on
3-4 June 2010, in parallel with a new international meeting on radiation protection and safety
issues for patients. Presentations from CardioCTMR 2009, and from CardioCTMR 2008, will soon be
available at
www.cardioctmr.com.
by JF Paul, Paris, France
Coronary CT angiography performance guidelines
This year, the Society of Cardiovascular Computed Tomography (SCCT) published two practice
guidelines in its official publication, the
Journal of Cardiovascular Computed Tomography. The first report focused on interpreting
and reporting the results of coronary CT angiograms (see MDCT.net news from
May of this year) [
1 ]. The second report, now freely available online, sets standards for
image acquisition and data processing, and suggests approaches for optimizing image quality and
diagnostic yield [
2 ].
The 15-page document is organized in six main sections, each with a set of recommendations.
The first part addresses competencies for physicians and technicians, as well as technical
standards for CT scanners. In particular, scanners must have at least 16 detector rows, but 32 or
more detector rows are recommended. Moreover, radiation dose should be recorded using the
dose-length product for every patient, as recommended in the earlier report. Successive sections
focus on screening for contraindications, providing preprocedural instructions and medications, and
positioning patients for the examination. Another section describes the administration of contrast
medium and recommends using contrast agents with high iodine concentration, injection flow rates of
4-7 ml/s, and bi- or triphasic injection protocols. Regarding image acquisition, the document
describes techniques for reducing radiation exposure and discusses the main scanning parameters,
including when to use prospective ECG triggering or retrospective ECG gating and how to adjust the
imaging protocol to a patient's heart rate and body weight. Finally, the document addresses image
reconstruction and editing.
The authors conclude by noting that successful imaging is only possible with a thorough
understanding of the advantages and limitations of CT angiography, combined with the proper
selection and preparation of patients and the correct scanning and image processing. They call for
both expertise and vigilance to ensure an accurate and safe execution of the examination.
Selected literature update
Automated MDCT measurements: new applications
Two methodological papers on automated MDCT measurements have been included in the literature
library of MDCT.net. The papers were published last month in
European Radiology.
Researchers from Germany tested the accuracy of different CT protocols in measuring the
diameter and volume of lymph nodes in a phantom model [
1 ]. The phantom had 17 different lesions, which were imaged with 16
scanning protocols that varied in tube current, reconstruction kernel, or slice thickness; data
were analyzed using the lymph node algorithm provided with SyngoOncology software. Concordance
between actual and MDCT values of diameter and volume, expressed as correlation coefficients,
ranged from 0.94 to 1.00. This high concordance achieved in a phantom model suggests that automated
MDCT lymph node sizing may be possible in the clinical setting.
Researchers from three French cities tested the reproducibility of automated measurements of
airway dimensions [
2 ]. In the study, 5 women with breast cancer underwent 64-slice MDCT
twice on the same day. Image reconstruction and 3D modelling of the bronchial tree were done using
BronCare software, developed by the same authors. A strong correlation (r>0.96) was found
between the first and second measurements of both lumen area and wall area; this was achieved using
either a semi-automated or a fully automated method. The authors also looked at serial changes in
bronchial dimensions along 10 successive slices, expressed as the coefficient of variation (CV10);
the correlation between CV10 values from the first and second acquisitions was good (r=0.89 for
lumen area; r=0.72 for wall area). The authors propose using CD10 values in longitudinal studies of
bronchial remodelling.
Accuracy of CT colonography screening in high-risk persons
Guidelines published in 2008 by three US medical associations concluded that CT colonography was
a valid method for screening the general population for colorectal cancer (CRC) (see MDCT.net news
of
April 2008) [
1 ]. However, the accuracy of CT colonography in high-risk individuals
had not been reported.
The diagnostic accuracy of CT colonography as a CRC screening method in high-risk persons
was evaluated in a multicenter, cross-sectional study, recently published in
JAMA [
2 ]. The study involved 1 Belgian and 11 Italian centers that enrolled
persons at increased risk of advanced neoplasia due to a family history of CRC, a previous
polypectomy for colorectal adenoma, or a positive fecal occult blood test (FOBT) result. Each
individual underwent non-contrasted CT colonography (on 16-slice scanners in over 70% of cases),
followed by colonoscopy within 3 hours.
Overall, 937 persons underwent both diagnostic examinations and 177 (18.9%) were found to
have advanced adenoma or carcinoma. CT colonography had a specificity of 85.3% and a sensitivity of
87.8% for lesions at least 6 mm in diameter; the negative predictive value was 96.3% overall but
84.9% in the group of subjects with a positive FOBT result. The authors concluded that CT
colonography may be considered an alternative screening method also in subjects at high risk for
CRC.
The Société Française de Radiologie (SFR,
www.sfrnet.org) is the leading French professional association for
radiologists. The association's aims are to promote radiology through advancing knowledge,
validating scientific information, and training physicians. SFR celebrated 100 years of activity
this year and has more than 7000 members in 21 regional groups.
SFR achieves its goals by publishing the monthly
Journal de Radiologie, as well as a society bulletin and the French edition of Imaging
Management. In addition, each year it holds the
Journées Françaises de Radiologie, an annual conference in Paris. This year's meeting will
be held on 16-20 October and is expected to have 17 000 participants, 100 scientific sessions and
500 posters.
SFR encompasses several specialty imaging associations dedicated to otorhinolaryngology,
neuroradiology, pediatrics, cardiovascular medicine and to the pathologies of skeletal muscle,
breast, thorax, abdomen and genitourinary tract. Moreover, it has about 30 working groups that set
SFR policy and suggest topics for the annual conference. The working group on contrast agents
(CIRTACI) has prepared a set of practice guides, available online, and has established an
observatory for monitoring allergic reactions.
Interpreting and reporting the results of CT angiography
The Society of Cardiovascular Computed Tomography (SCCT) recently published its first guidelines
on CT coronary angiography. The 15-page document, authored by 10 physicians from the US and
Germany, was developed as an “educational tool” for practitioners and is offered as a contribution
towards the establishment of practice standards.
The first part of the document addresses the interpretation of CT angiograms: it begins by
reviewing fundamental concepts, such as post-processing image formats and coronary calcium scoring,
discusses in detail how to evaluate coronary artery anatomy and pathology, and closes with comments
on non-coronary findings. The second part set standards for reporting CT angiography findings, so
that referring physicians receive rigorous, clear documentation; for this purpose, the writing
committee proposed a structured report, with sections on the patient's clinical status, the imaging
procedure (e.g. equipment, patient preparation, acquisition, reconstruction), the results
(including technical quality and all clinical findings), and the radiologist's interpretation.
Selected literature update
64-slice CT coronary angiography: latest research
The use of multislice CT angiography to study the coronary arteries has been much discussed in
the scientific literature and in MDCT.net's news column (see, for example, stories from
March 2009 and
December 2008) . Three new reports on
64-slice CT coronary angiography have been included in MDCT.net's literature database this month.
The April issue of European Radiology contains a report describing the objectives and
methodology of the CORE-64 trial [
1 ]. This multicenter trial, conducted in nine centers in North and South
America, Europe and Asia, aimed to determine the diagnostic accuracy of 64-slice CT angiography in
detecting stenosis in patients with coronary artery disease. Patients underwent contrast-enhanced
imaging on 64 scanners and then conventional coronary angiography within 30 days. The authors
emphasized that the large size and multicentric nature of CORE-64 should overcome limitations of
earlier studies that highlighted an inadequate specificity of 16- to 64-slice CT angiography. It is
unknown when the trial's result will be published.
In La Radiologia Medica, Italian and Dutch researchers reported the use of 64-slice CT
coronary angiography to investigate aspects of atherosclerotic plaque composition that lead to
vulnerability [
2 ]. They focused on the left main coronary artery, which infrequently has
vulnerable plaques, and found that the presence of plaque was associated with increased artery
diameter; there also was a moderate correlation between diameter and plaque area.
Finally, researchers at the Medical University of South Carolina tested a prototype
instrument that combined 64-slice CT with SPECT for simultaneous assessment of coronary anatomy and
myocardial perfusion [
3 ]. Such a system would obviate the need for image fusion algorithms to
combine separate CT and SPECT results and should facilitate assessment of the hemodynamic impact of
coronary artery disease.
Despite the increasing use of MDCT angiography worldwide, there is inadequate knowledge of the
magnitude of radiation exposure during an examination, the factors that contribute to this
exposure, and the effectiveness of dose-reduction protocols. Researchers from the US and Germany,
funded by the German Heart Center in Munich, did an observational study to determine radiation dose
in daily practice.
The PROTECTION I study, published in JAMA [
1 ], involved 50 university and community CT centers in 26 countries and
enrolled 1965 unselected patients who underwent cardiac CT angiography for various clinical
indications with different CT protocols and scanners. Radiation dose was measured as the
dose-length product (DLP) while the effective dose was calculated using a conversion factor given
in the
2004 CT quality criteria.
Median DLP was 885 mGy · cm per scan (corresponding to 12 mSv effective dose), but there was
wide variability in the median value per site, ranging from 331 mGy · cm (5 mSv) to 2146 mGy · cm
(30 mSv). There also was wide variability among sites using the same CT scanner, which was
attributed to incomplete use of dose-reduction strategies. Multivariable linear regression analysis
revealed that DLP increased with scan length (5% per centimeter), yet decreased when sequential
scanning was used (-78% vs. spiral scanning), tube voltage was reduced to 100 kV (-46% vs. 120 kV)
and tube current was modulated by ECG (-25%); automated exposure control did not reduce radiation
dose. A diagnostic reference DLP of 1200 mGy · cm was proposed based on the 75th percentile of
values in the study.
The authors concluded that, although CT angiography can exposure patients to a high level of
radiation, dose-reduction techniques – in particular ECG modulation of tube current – are effective
and should be more widely used. They proposed that DLP be recorded in every CT report to help CT
centers monitor radiation dose, and called for better training on the use of dose-reduction
strategies.
Profile: Society of Cardiovascular Computed Tomography
The Society of Cardiovascular Computed Tomography (SCCT,
www.scct.org) is an international professional association whose mission is
to promote research, education and clinical practice regarding cardiovascular applications of CT.
Members are medical physicians, administrators, scientists and technologists actively engaged in
the practice or management of cardiovascular CT.
SCCT produces the
Journal of Cardiovascular Computed Tomography, a bimonthly that began in 2007. This July,
the association will hold its fourth annual meeting in Orlando; the nearly 400 submitted abstracts
will be published in the association's journal. The meeting will be preceded by a 2-day cardiac CT
review board course. The SCCT also organizes refresher courses in CT angiography in different US
locations.
Since 2005, the association has worked with other professional societies to establish
clinical competence guidelines and appropriateness criteria regarding cardiovascular imaging.
US court decides in favor of Bracco Diagnostics in comparative advertising case against GE
Healthcare
The NEPHRIC study, published in the New England Journal of Medicine in 2003 [
1 ], investigated two contrast media produced by GE Healthcare and found that the safety
profile of the iso-osmolar iodixanol was superior to that of iohexol, a low osmolar contrast
medium.
Although the trial did not investigate other low osmolar agents, subsequent advertisements
by GE Healthcare led to misinterpretation of the study by extending the results to other low
osmolar contrast agents, such as iopamidol, produced by Bracco Diagnostics.
On 25 March 2009, a US federal court decided that generalizing to all low osmolar contrast
agents was scientifically unjustified. The court ordered GE Healthcare to cease from making further
false claims, to issue corrective advertisements in order to ensure that healthcare providers are
informed about the false claims, and to compensate Bracco Diagnostics for its own expenses in
corrective advertising, amounting to US$ 11.4 million.
CT colonography endorsed as “alternative cancer prevention test” in ACG guidelines
The American College of Gastroenterology (ACG) recently issued an update to their guidelines on
colorectal cancer screening [
1 ]. One of the innovations of the revised guidelines is the distinction of screening
methods into cancer prevention and cancer detection tests: cancer prevention tests can detect both
polyps and cancer and thus are preferred to cancer detection tests, which are ineffective in
detecting polyps.
The recommended cancer prevention test is colonoscopy (every 10 years starting at age 50 in
average-risk persons). Persons who refuse colonoscopy and those in whom colonoscopy is not feasible
should be offered an alternative test. Two alternative cancer prevention tests are recommended:
flexible sigmoidoscopy (every 5-10 years) and CT colonography (every 5 years). CT colonography,
which replaced double contrast barium enema in the revised guidelines, was endorsed because of its
90% sensitivity for polyps 1 cm or larger [
2 ]. Other attractive features of this method, according to the report, are the ability
to detect extracolonic pathology, patients' preference and – subsequently – the possibility that
more persons adhere to screening programs using this technology. Current limitations to CT
colonography, for which it was not chosen as the first-line method, include the inability to detect
small polyps, frequent false positives (86% specificity), and radiation exposure. Thus, until new
studies show improved specificity or clinical impact, CT colonography should be used as an
alternative cancer prevention test when colonoscopy is not possible.
This month's update to MDCT.net's literature archive includes reviews on two important clinical
applications of MDCT. Writing in
Current Atherosclerosis Reports, clinicians from the Cardioangiologisches Centrum
Bethanien (Frankfurt) review evidence supporting the use of MDCT angiography in the assessment of
atherosclerosis [
1]. Their report discusses the effectiveness of CT angiography in diagnosing and
characterizing calcified and non-calcified plaques, in ruling out severe stenosis in symptomatic
patients in the emergency setting, and in predicting the prognosis of patients with
atherosclerosis. Although it remains to be demonstrated that CT angiography is superior to
conventional methods of risk stratification for atherosclerosis, the authors conclude that the
current evidence is encouraging.
On the pages of
European Radiology, radiologists from Beth Israel Deaconess Medical Center (Boston) review
the state of the art in the CT evaluation of pulmonary emphysema [
2]. Their report describes the use of CT to visualize this pathology and to objectively
quantify the extent of disease based on attenuation values and complex textural analyses. It
discusses how clinical parameters (e.g. patient's age and lung size) and scanning parameters (e.g.
imaging during inspiration vs. expiration) impact upon the quantitative evaluation. Finally, it
predicts that new-generation MDCT scanners will open new avenues of clinical investigation, such as
evaluating lung ventilation and perfusion and studying the evolution of emphysema into chronic
obstructive pulmonary disease.
The uses of medical imaging in the diagnosis and treatment of diseases of the chest are the
topics of a truly international congress to be held in Valencia, Spain, between 30 May and 2 June
2009. The Second World Congress on Thoracic Imaging and Diagnosis of Chest Disease has been
organized by the Fleischner Society, the Society of Thoracic Radiology, the European Society of
Thoracic Imaging, the Japanese Society of Thoracic Radiology and the Korean Society of Thoracic
Radiology; it is being hosted in Valencia by three Spanish medical associations.
The meeting will offer plenary sessions on interstitial lung disease, chronic obstructive
pulmonary disease, cardiac imaging, lung cancer, and pulmonary embolism and hypertension. Numerous
scientific sessions will deal with CT applications such as MDCT in the emergency setting, low dose
CT, computer-aided diagnosis in chest CT, and CT angiography. The congress will offer 17
instructional courses, an image interpretation session and several manufacturers' symposia. The
full program and an online registration form are available at
www.2wcti.org.
AHA recommendations on the safe use of cardiac imaging
Decisions regarding the use of ionizing radiation in medical imaging – to keep the radiation
dose as low as reasonably achievable – are the responsibility of individual radiologists, who must
be up to date on technical issues and understand the risk:benefit balance. To assist radiologists
in this important decisional role, the American Heart Association (AHA) prepared a science advisory
entitled “Ionizing radiation in cardiac imaging”. AHA science advisories are position statements
written and peer-reviewed by AHA members. This report, written by a group of 13 physicians and
researchers from the USA, was recently published in
Circulation [
1 ].
The AHA report addresses three main issues: estimating radiation dose, understanding the
risks of radiation exposure, and understanding the risks of not performing diagnostic imaging.
First, the paper summarizes the parameters by which radiation dose is measured in CT, fluorography
and radionuclide studies, and discusses how to interpret and report these parameters. It then
reviews the risk of carcinogenesis from radiation exposure and relates this risk to the chances of
dying from activities of daily life. It briefly deals with potential risks of not performing needed
imaging studies, but acknowledges that there is no evidence of a survival benefit in patients
exposed to ionizing radiation. The report concludes with a summary and list of recommendations
rated according to the evidence schema of the American College of Cardiology Foundation/AHA.
The recommendations of this AHA science advisory include: (i) a statement against
surveillance imaging in asymptomatic patients at low risk for heart disease, (ii) a comment that
longitudinal monitoring of patients' cumulative exposures is currently not feasible, (iii) a call
for the development of better radiation dose metrics, and (iv) a proposal that radiologists
establish references levels for radiation exposure in different diagnostic examinations, to use in
international benchmarking studies.
International exchange program for young radiologists
The European School of Radiology is continuing, for the third consecutive year, its
international exchange program for radiologists in training. The Visiting Scholarship program
supports a 3-month focused training period in radiology centers of excellence throughout Europe
and, for the first time, in New York City.
Topics of study for 2009 are abdominal radiology, breast imaging, cardiac imaging, chest
imaging, musculoskeletal radiology, neuroradiology, oncologic imaging, urogenital radiology, PET-CT
protocols and MRI protocols. The 2009 edition will provide 29 trainees with scholarship funding to
cover living expenses and travel costs. Funding is provided by Bracco together with the Memorial
Sloan-Kettering Cancer Center and the European Society of Radiology (ESR). Information regarding
eligibility and how to apply is available from the education section of the
ESR website. The application deadline is 1 April 2009.
by V. Matarese
Coronary atherosclerosis investigated with MDCT
The diagnosis – or exclusion – of coronary atherosclerosis in patients with cardiovascular risk
factors can help predict the probability of future cardiac events. Two studies addressing this
issue in the
International Journal of Cardiovascular Imaging have been included in the literature
archive of MDCT.net.
Researchers at the University Hospital of Ulm, Germany, investigated if coronary
atherosclerosis can be predicted from the thickness of the mid-descending aortic wall, since
atherosclerosis is a “diffuse condition” that can simultaneously affect coronary, cerebral, carotid
and peripheral arteries [
1 ]. They retrospectively evaluated contrast-enhanced 40-slice CT coronary angiograms
from 58 patients without and 102 patients with coronary atherosclerosis (diagnosed when coronary
plaques were seen with CT). Aortic wall thickness increased with age (confirming previous
knowledge) and was higher in patients with coronary atherosclerosis (particularly in those with
calcified plaques). Thus, the authors hypothesized that coronary atherosclerosis can be predicted
from aortic wall thickness measured on routine chest CT studies, without the need for specific
cardiac imaging.
The second study, contributed by researchers in Turkey, used 16-slice MDCT calcium scoring
to assess cardiovascular risk in 31 patients with subclinical primary hyperparathyroidism (PHP) and
in 19 healthy controls. Median calcium score was zero in both groups, but there was wide
interpatient variability in the PHP group. When this group was subdivided according to the absence
or presence of hypertension, normotensives were found to have calcium scores similar to those of
controls whereas hypertensives had significantly higher scores (and were older with a greater
prevalence of obesity and hyperlipidemia). The authors concluded that asymptomatic PHP is not a
risk factor for coronary atherosclerosis, so these patients can be treated conservatively.
Each year, the European Society of Radiology acknowledges individuals who have made important
contributions to the field of radiology. This year, ten radiologists were named as dignitaries.
Gold medals were given to Helen M.L. Carty (Liverpool) and Antonio Chiesa (Vicenza). Dr.
Carty was recognized for outstanding advances in pediatric and orthopaedic radiology. Among her
numerous professional roles, she was director of radiological services at Royal Liverpool Children‘
s NHS Trust and professor of pediatric radiology at Liverpool University. She is one of the
innovators of a radiological intervention for aneurysmal bone cysts in children. Dr. Chiesa was
awarded for exceptional contributions in head and neck radiology and for outstanding leadership in
advancing Italian and European radiology. His recent professional roles were as director of the
Radiology Department and as professor of radiology in the Schools of Medicine and Odontology, all
at the University of Brescia.
The honor of giving the ECR opening lecture was awarded to Hedvig Hricak (New York), whose
experience with anatomic and molecular imaging of genitourinary cancer formed the basis for a talk
entitled 'Imaging in oncology: endless horizons'. Other honorary lecturers at ECR 2009 were Carlo
Bartolozzi (Pisa), Dieter R. Enzmann (Los Angeles) and Anton Valavanis (Zurich).
Honorary membership in the European Society of Radiology, awarded for outstanding scientific
contributions to the field of radiology, was given to Jürgen Hennig (Freiburg), Theresa C. McLoud
(Boston), Ho-Young Song (Seoul) and James H. Thrall (Boston).
Biographies of these distinguished radiologists are available at
www.myesr.org.
by V. Matarese
ECR 2009: Abdominal imaging
This year's European Congress of Radiology (ECR) has been a tremendous success again, with many
excellent talks covering all aspects of radiology. Although the weather was wet during much of the
meeting, most - if not all - participants seemed to have greatly enjoyed the opportunity to get up
to date with today's topics in radiology. Abdominal imaging was present in the ECR program,
although I did not encounter any particularly important advances.
Abdominal topics were not specifically addressed in the "new horizon" sessions, which dealt
with cell and plaque imaging and which pointed into the future. This was also the case in the
"state of the art" symposia, which centered on stroke management, lung cancer screening, and the
interaction of the radiologist with the computer.
Of the 20 "special focus" sessions, one stressed the value of PET-CT in monitoring tumor
responses. In the session on dual energy CT, potential applications for this novel technique within
the abdomen were presented, but they do not seem ready for widespread clinical use. An excellent
session - and the only one that dealt primarily with the abdomen - was named "Portal hypertension,
an update". This session stressed the need for multimodality imaging in the work-up of pre-,
intra-, and post-hepatic causes of portal hypertension. Both CT and MRI have their specific
advantages, but MDCT is well established in this application.
Dedicated "categorical courses" were offered in the fields of spinal imaging and
intervention, cardiac imaging, and breast imaging. "Mini courses" were organized on advances in CT
and MRI for trauma imaging, and on extremity joint MRI. Again, these sessions offered nothing of
specific interest for an abdominal radiologist.
Fortunately, the refresher courses dealt with many interesting topics from the abdominal
field, including, for example, the growing role of PET-CT for esophageal cancer, imaging of
hepatocellular carcinoma (still strong for MDCT), and the discussion of MRI versus CT in Crohn's
disease. There was also a session on imaging and intervention in gastrointestinal bleeding that I
was supposed to present myself, but unfortunately I was unable to do so because of acute food
poisoning the night before.
In conclusion, this year's ECR did not have abdominal radiology in its primary focus, but
both MDCT and abdominal radiology were well represented in many areas.
by Andrik J. Aschoff, Kempten, Germany
ECR 2009 : Cardiac CT
Radiation exposure is always an important topic in CT, especially in cardiac CT which delivers a
substantial radiation dose. However, as documented by a study published in the February 4th issue
of
JAMA [
1 ], the radiation dose from cardiac CT is highly variable among centers. This study,
which surveyed 21 academic and 29 community hospitals in Europe, USA, Asia and South America, found
that the median radiation dose to patients varied from 5 to 35 mSv depending on the center. Thus,
every new technological improvement which may help reduce radiation dose is welcomed.
New strategies for radiation dose reduction in cardiac CT were shown at this year's European
Congress of Radiology (ECR), held on 6-10 March in Vienna. In particular, CT manufacturers have
introduced several new technological features:
Sequential scanning protocols, prospectively triggered by ECG recordings, are now
routinely proposed by all manufacturers. This technique blocks radiation exposure outside a
specific time window, thereby reducing dose by about 75% without impairing image quality for the
chosen time window. The applicability of this method is becoming more robust by automatic detection
of arrhythmia, avoiding acquisition in an inappropriate temporal window. Acquisition using only one
rotation (Toshiba Aquilion One), now possible with very large detector rows, has also improved
robustness in sequential scanning. This technique is now routinely applicable in patients with low
and regular heart rates. Broad adoption of sequential scanning, however, will take time since only
a few centers are currently equipped with the necessary instrumentation: in the study published in
JAMA [1], sequential scanning was used in only 6% of cases.
Enhancement of the quality of detection is another way to reduce dose for a given image quality.
This approach was chosen by GE, using new detectors based on Gemstone technology that enhances the
detection of X-rays. In addition, new reconstruction algorithms (so-called iterative algorithms,
coming from nuclear medicine imaging technology) improve the signal-to-noise ratio without
increasing radiation dose. GE claims lower radiation doses with improved image quality. Cardiac
images shown in Vienna, obtained with this technique together with the sequential mode, were
associated with an exposure of 2 or 3 mSv to the patient, depending on the kilovoltage
settings.
Siemens showed the first cardiac images using the
flash mode on the new dual source CT (Flash Definition). This new acquisition technique is
based on fast spiral acquisitions (pitch of 3.2, using both tubes). Acquisition is triggered by
ECG. The cardiac images are acquired in the diastolic phase in patients with very low and regular
heart rates, to avoid motion during this fast acquisition (about 300 ms are required to scan the
whole heart, so a long period without heart motion is required). This allows a one-beat acquisition
based on speed instead of large coverage, which is the strategy used by Toshiba’s Aquilion One.
One-beat acquisition avoids the step artifacts usually seen when acquisition is performed over
several heart beats. Because exposition time is short, radiation dose is also low: Siemens claims
that by using this new concept for acquiring cardiac images, the exposures will be in the
sub-millisievert range. Of note, as for the sequential mode, this low-dose protocol is only suited
for use in patients with low heart rate, which remains an important limitation.
Research into new technological solutions to reduce radiation dose is going in various
directions. The most efficient radiation dose-sparing strategies will be adopted by manufacturers
for the benefit of patients. These new solutions must be evaluated by radiologists, but it is
reasonable to anticipate that the mean radiation dose to patients during cardiac CT will soon be
lower than that associated with coronary angiography (5 mSv). Alongside better image quality, one
can also expect a huge increase in the use of coronary CT in the near future, opening new frontiers
such as screening for coronary artery disease, which is still one of the major causes of mortality
in developed countries.
MDCT angiography and peripheral arterial disease: a meta-analysis
In patients with intermittent claudication or critical limb ischemia from peripheral arterial
disease, treatment planning requires accurate diagnostic information regarding stenosis and
occlusion. This information is provided by intra-arterial angiography or by noninvasive imaging
modalities, such as duplex ultrasonography, magnetic resonance angiography and computed tomography
angiography. In particular, MDCT angiography permits high-resolution visualization of the entire
vascular tree of the lower extremities. Researchers in Amsterdam did a meta-analysis to assess the
diagnostic performance of MDCT angiography; they published their findings in
JAMA [
1 ].
The meta-analysis included 20 diagnostic cohort studies that compared MDCT angiography to
digital subtraction angiography in patients with intermittent claudication or critical limb
ischemia; 12 similar studies were excluded for not having reported data in a format suitable for
meta-analysis. Most included studies used 4- or 16-slice scanners, while two used 64-slice imaging.
Overall, the methodological quality of the studies was moderate according to the QUADAS tool for
assessing diagnostic accuracy studies [
2 ].
This analysis found that MDCT angiography is highly accurate for diagnosing clinically
significant (>50%) stenosis and occlusion throughout the lower vasculature. For the aortoiliac
arteries, combined sensitivity was 96% and combined specificity was 98%. For the femoropopliteal
arteries these values were 97% and 94%, while for the tibial arteries they were 95% and 91%,
respectively. Sensitivity and specificity values were higher with 16- and 64-slice scanners than
with 2- or 4-slice scanners, but did not vary according to disease severity or methodological
aspects of the studies. Despite these good results, the authors noted that definitive conclusions
cannot be drawn due to methodological limitations of the included papers; they emphasized that
future studies on this topic adhere to the STARD checklist for reporting diagnostic accuracy
studies [
3 ].
Today, most articles indexed in Medline are available electronically and so can be found with a
general search engine like Google. However, comprehensive, sensitive and specific searching is only
possible by invoking the controlled vocabulary and search fields available on PubMed and commercial
literature databases. In the same manner, general search engines permit searching of radiographic
images in medical journals, but the simple search algorithms give unsatisfying results. Two online
tools – GoldMiner and Yottalook Images – now permit accurate searching of radiographic images
within the electronic texts of peer-reviewed journals.
GoldMiner (
goldminer.arrs.org ), provided by the American Roentgen Ray
Society, provides access to 200 000 freely available images from 261 peer-reviewed journals. A
user's terms are searched both as free text keywords and as medical concepts after matching to
three controlled vocabularies: Systematized Nomenclature of Medicine (SNOMED) clinical terms, the
Foundational Model of Anatomy, and NLM's medical subheadings (MeSH). Quality search results are
guaranteed by this dual keyword-context search function and by limiting results to a certain
anatomical region, imaging finding, age class, gender, and type of image (CT, MRI, PET, US, X-ray,
nuclear medicine, photograph, graph).
Yottalook Images (
www.yottalook.com ) is part of the radiological search engine offered by
iVirtuoso. This tool permits searching among 750 000 radiographic images from free and
subscription-based peer-reviewed journals. Effective searching is guaranteed by natural query
analysis of the search terms and by sematic matching against a medical thesaurus based on RadLex
(of the Radiology Society of North America). Search results may be limited to one imaging technique
(plain radiography, CT, MRI, nuclear medicine, US) or to only freely available sources.
Both Goldminer and Yottalook Images are free to search, but the retrieved images must be
used in accordance with each journal's copyright policies. Both tools are now testing multilingual
search capabilities.
by V. Matarese
Profile: European Society of Neuroradiology
The European Society of Neuroradiology (ESNR,
www.esnr.org ) is a professional association whose aim is to
promote the speciality of clinical neuroradiology, including diagnostic, interventional, head and
neck, and pediatric neuroradiology. Legally based in Switzerland, the ESNR's central office is in
Milan and its current president is Prof. Marco Leonardi of Bellaria Hospital in Bologna.
The society's 34th congress and 18th advanced course will be held this year in September in
Athens, while a joint symposium with the American Society of Spine Radiology (ASSR) will be held in
July in Rome. Since 1984, the association has organized neuroradiology courses that permit
participants to become certified in neuroradiology at a European level. Moreover, the association
annually awards a young neuroradiologist the Lucien Appel Prize of the ESNR, worth eur. 4000. The
ESNR's official publication is
Neuroradiology, a journal published by Springer (
www.springer.com ).
by V. Matarese
Three-dimensional imaging with MDCT
Three-dimensional (3D) anatomical visualization with CT is a diagnostic imaging advance made
possible by technological developments in both instrumentation and image processing software.
Multidetector CT datasets can now be “reconstructed” to show particular imaging planes, tubular
structures, fine vascular trees and specific anatomical surfaces. The resulting detailed and
accurate images provide excellent support to surgical planning and permit a more precise diagnosis
of a pathology and its impact on neighboring structures. To Morton A. Meyers, editor of
Abdominal Imaging, these innovations represent a “new imaging paradigm” [1]. Thus, this
journal dedicated the first issue of 2009 to 3D CT imaging.
Reports in this issue focus on novel imaging methods for a range of clinical topics,
including esophageal pathology, gastric cancer, small bowel obstruction, appendicitis, peritoneal
carcinomatosis, pancreatic and biliary pathologies, adrenal tumors, and urinary tract cancer. A
number of virtual imaging techniques are described: virtual angioscopy, virtual endoscopy, virtual
simulation, and virtual hysterosalpingography. In the words of Dr. Meyers, “read on and share the
excitement”.
This coming June, the European Society of Musculoskeletal Radiology (ESSR) will meet in Genoa,
Italy, for a 2-day scientific conference and a refresher course entitled “Hip & Bone Pelvis”.
The conference will be preceded by a meeting of the Italian Society of Medical Radiology. This
one-day national event will offer scientific sessions, workstation sessions and imaging workshops,
and keynote lectures will be given by Daniel Vanel on imaging soft-tissue tumors and by Folco Rossi
on radiology in sports medicine. Participants of the joint meeting may also attend a course on
ultrasonography of the hip.
The ESSR is accepting abstracts for scientific and educational presentations until 20
February 2009. Accepted abstracts will be published in
Skeletal Radiology. More information about the joint conference is available at
www.essr-sirm2009.it
by V. Matarese
Left ventricular dysfunction: comparative study of MDCT vs. MRI plus coronary
angiography
Left ventricular dysfunction (LVD) may be due to myocardial ischemia or non-ischemic dilated
cardiomyopathy. Defining the etiology of LVD in individual patients is therefore important for
prognosis and treatment; this requires examination of both myocardial viability and coronary
anatomy. Differentiation between ischemic and non-ischemic etiologies is possible with
gadolinium-enhanced MRI: patients with ischemic disease typically have delayed enhancement (DE) in
transmural or subendocardial segments, whereas DE is absent or atypical in those with non-ischemic
disease. A full diagnosis, however, requires angiography to search for coronary artery disease
(CAD).
Researchers from Belgium investigated the possibility of diagnosing LVD with
contrast-enhanced MDCT, by combining information from both coronary (immediate) and delayed imaging
[1]. They prospectively studied 71 patients who underwent angiography, MRI, and 40- or 64-slice
MDCT with iomeprol (400 mg/ml iodine; Iomeron 400, Bracco, Milan, Italy) in a 1-month period.
Findings from angiography and MRI were used to classify patients into four groups according to the
presence or absence of CAD and of DE characteristic of LVD. Similarly, patients were classified
according to the combined MDCT findings, and the results were compared.
Overall, there was good agreement in patient classification between the angiography-MRI
protocol and the combined MDCT protocol (κ=0.89), with only 5 patients misclassified. Thus,
combined coronary and delayed MDCT was found to have 97% sensitivity, 92% specificity, and 94%
accuracy for diagnosing patients with definite or probable ischemic LVD. The authors discussed the
advantages and limitations of using contrast-enhanced MDCT to diagnose LVD.
Biomarkers with potential to identify patients at risk of CIN
Understanding a patient's risk of contrast-induced nephropathy (CIN) is essential for weighing
risks against benefits of a diagnostic or therapeutic procedure, and for choosing a prophylactic
measure. Of the known risk factors for CIN, reduced kidney function is considered the most
predictive.
Kidney function is usually estimated from serum creatinine levels, although other serum and
urinary biomarkers have been proposed. Researchers in Japan monitored a series of potential
biomarkers to find those that predict the occurrence or onset of CIN [1]. They prospectively
studied 87 patients scheduled for coronary angiography, and found that serum levels of cystatin C
prior to catheterization were higher in patients who developed CIN. Using a cutoff of >1.2 mg/l,
cystatin C had 94.7% sensitivity and 84.8% specificity for predicting CIN. Moreover, in patients
who experienced CIN, urinary levels of liver fatty acid binding protein were elevated in the 2 days
following catheterization.
In the search for biomarkers, proteomics is considered state of the art. Applying this
approach, researchers in the USA investigated 90 children with congenital heart disease who
required cardiac catheterization and angiography [2]. Urine samples were analyzed before the
procedure and in the subsequent 24 h using SELDI-TOF mass spectrometry and protein chromatographic
microarrays (ProteinChips). This identified two small proteins whose pre-procedural urinary levels
were significantly different between subgroups of patients who did and did not experience CIN. In
particular, a variant of beta-defensin-1 was significantly lower in patients who had CIN, while an
unknown 4.6 kDa protein was significantly higher in these patients.
These interesting results, if confirmed, may help avoid CIN by identifying predisposed
patients.
Selected literature update
MDCT and chronic lung diseases: three methodological advances
Three papers from a recent issue of
European Radiology have proposed new methods for quantifying lung disease. Researchers
from the University of Lille tested the prototype software in quantifying the extent of emphysema
[1]. The software offers automatic and semi-automatic scoring, which compared favorably with visual
assessment in 47 patients with severe chronic obstructive pulmonary disease (COPD).
Researchers from Germany and Sweden focused on airway-wall remodelling in COPD [2]. They
illustrated the capabilities of YACTA, a software programmed by members of their own group and
previously shown to quantify emphysema and facilitate lung segmentation. In this new study using
YACTA, airway wall thickness was higher in COPD patients who smoked than in non-smoker controls;
moreover, wall thickness correlated with forced expiratory volume.
Finally, researchers in Germany devised an algorithm to automatically classify lung tissue
as normal or pathological [3]. Their tool determines the topology of CT attenuation values based on
Minkowski functionals. This information, when combined with densitometric data, permitted the
accurate identification of diseased lung tissue in patients with emphysema or fibrosis.
These papers are among the full text articles added this month to the database of selected
literature in MDCT.net.
