Abdominal CT at the 2010 European Congress of Radiology

The twenty-second European Congress of Radiology offered its attendees another high-quality program, covering radiological topics in a three hundred sixty degree fashion. CT and, especially, its abdominal applications were central topics of this year's venue, giving participants much food for thought on the way back to their home countries.
During Friday's New Horizons session, Dr. Stolzmann from Zurich gave an interesting lecture on multi-energy CT and its relation to functional imaging. In the coming future, this novel imaging modality may offer new diagnostic possibilities in the abdominal district.
The mini-course entitled “Organs from A–Z: Liver” offered both radiological trainees and experts new insight into the clinical and radiological aspects of this organ. Different lectures, focusing on basic and advanced topics, followed one after the other. The program, divided into four parts, started with an introductory session on anatomy and imaging techniques, including talks on liver anatomy and the multimodality display approach (Dr. Schima, Vienna), CT and MRI protocols, (Dr. Marincek, Zurich), and imaging of liver function and structure (Dr. Menu, Paris). This was then followed by three sessions, each with three lectures, on the assesment of diffuse liver diseases, the description of primary liver tumors, and treatment strategies. In particular, vascular diseases of the liver, their detection and role in transplantation, especially in the context of CT imaging, were addressed in a memorable lecture by Dr. Vilgrain from Clichy.
Scientific sessions also dedicated much attention to abdominal CT, especially regarding new techniques offered by the latest CT technology, i.e. perfusion and dual-energy approaches. Liver perfusion, in particular, permits the evaluation of liver fibrosis in cirrhotic patients (as discussed by Dr. Ronot, Clichy) and the investigation of the response to anti-angiogenic treatment in patients with multifocal liver lesions (as explained by Dr. Menichini, Rome). Dr. Graser (Munich) presented an interesting paper on image quality and radiation exposure offered by second-generation dual-energy CT scanners for abdominal examinations. The quantification of liver fat, compound analysis of gallstones, and quantitative analysis of virtual noncontrast images as a possible means of dose reduction in cirrhotic patients were other hot topics in the field of dual-energy CT imaging of the liver.
Considering the exquisite program that ECR provided its participants this year, it seems truly that 2010 has started with a “radiological virtuosity”.

Dramatic reduction of radiation dose with new cardiac CT scanners: first results presented at ECR 2010

At the 2010 European Congress in Radiology (ECR), radiation dose associated with cardiac CT was again highlighted as an important topic, with a special session on Thursday. Recently, new technological developments such as high-pitch scanning and prospectively triggered acquisition have raised new expectations for the possibility of reducing radiation dose in cardiac CT. Indeed, these two different techniques both permit a significant reduction in the exposure time and, consequently, also in the radiation burden to patients.
The first clinical studies with these new techniques were presented at this year's ECR, confirming the dramatic reduction in radiation dose that had been expected by these technological developments. For example, high-pitch spiral data acquisition with prospective ECG triggering was associated with a radiation dose of only 3 mGy compared to 27 mGy in a comparable low-pitch spiral CT group. This translates to a 9-fold reduction in radiation dose without substantial loss in image quality.
In addition, for the first time, the biological effects of X-rays have been assessed by evaluating DNA double strand breaks (DSB) in lymphocytes. Researchers found a linear relationship between the number of DSB and the dose length product (expressed in mGy*cm). Another presentation described how sub-millisievert acquisition can be achieved using large detector technology with prospectively triggered acquisition and low kilovoltage settings.
On Saturday, a session dedicated to the assessment of atherosclerosis by cardiac CT underlined the potential of this technique to detect non-calcified as well as calcified plaques. The researchers pointed out that the evaluation of coronary arteries with MDCT may be predictive of major adverse cardiac events.
Advanced research in cardiac CT was also the subject of an interesting session on Sunday. The evaluation of cardiac perfusion now appears as feasible with MDCT, especially after correction for beam hardening artefacts. Dual-energy acquisition was also suggested to be a helpful tool for detecting acute and chronic myocardial infarction.
In summary, cardiac CT presentations at ECR were numerous and at a very high scientific level. The newest generation of CT scanners can overcome the main limitations of cardiac CT (i.e. radiation dose) and offers new possibilities for deeper analysis of cardiac structure and function.

Report from the ECR:  Advances in CT neuroimaging

At this year's European Congress of Radiology, session SS 511b, called “Neuro – Advances in CT”, took place on Friday, 5 March 2010 in the Austria Center.  The session reported new trends in CT neuroimaging with a special focus on MDCT.
In the first presentation, D. Morhard from Munich gave a presentation entitled “Stroke CT: CTA or perfusion CT? Which should be done first?” and described a study that had evaluated which order of CT imaging exams is advantageous in a comprehensive stroke work-up. The study underscored the point that contrast medium administration prior to perfusion CT did not have a significant effect on the perfusion parameters. When perfusion CT was performed first, however, there was contrast agent preloading in the veins. Morhard therefore recommended a reversal of the traditional order of exams, with CT angiography being performed first, followed by perfusion CT.
The second presentation by E. Smit from Utrecht was called “Arterial input function characteristics for CT-perfusion in normal patients and patients with carotid stenosis or occlusion".  The background of this study is that the arterial input function (AIF) may result in incorrect regional perfusion measurements, when dispersion or delay occurs due to pathology or a higher distance between the region of the AIF and the measured region. This research group found that TPP and MTT vary between different cerebral arteries especially in patients with unilateral pathology of the internal carotid artery. Smit therefore concluded that a single AIF may not be suitable for regional brain perfusion measurements especially in patients with carotid stenoses.
In the next presentation, L. Saba from Cagliari gave a talk entitled “Carotid artery wall thickness and leukoariosis: Evaluation using multi-detector CT angiography”. This presentation described a study that retrospectively evaluated carotid artery wall thickness (CAWT) in 98 patients and correlated it to the presence and severity of leukoariosis. The researchers found a significant correlation between CAWT and the presence of leukoariosis when a threshold value of 0.9 mm for CAWT was chosen.
In the fourth presentation, D. Maintz from Muenster reported on a study entitled “Evaluation of collateral flow in cerebral vessel occlusion using 4D CT-angiography: impact on the outcome after multi-modal recanalization therapy” (the first author was V. Hesselmann). In this study, researchers evaluated volume-rendered 4D-CT angiography-like datasets from  perfusion CT to assess the degree of collateralization and to correlate it to the patients' outcomes. The group demonstrated that collateral flow could be estimated from the 4D-CT angiography datasets.  In the study population, good collateralization was associated with a significantly better outcome. Maintz, however, mentioned that a limitation of the study was that the patient population was comparatively heterogeneous.
The next paper, “Lower radiation dose adaptive statistical iterative reconstruction head CT examinations match quality of prior conventional dose studies”, was given by L.N. Tanenbaum (first author, E.G. Stein).  In this study, 16 patients were scanned on a Discovery CT750 HD CT scanner and images were reconstructed with adaptive statistical iterative reconstruction. The data were compared to prior CT scans with conventional radiation doses and filtered back projection. The group found the average radiation dose to be significantly reduced by 29% from 1.5 mSv to 1.1 mSv. At the same time, noise levels were comparable and diagnostic image quality was preserved, as assessed by blinded reviewers.
Another presentation was given by F.E. Ebner from Graz on the topic “Digital subtraction volume 4D CT angiography of the brain: reducing radiation dose using a mathematical model for bolus timing”. This study aimed to find an optimal time window for 4D-CT angiography and to limit radiation dose accordingly with 320-row volume CT technology.  Overall, 46 patients were included and received a 10 ml test bolus, followed by a 50 ml regular bolus of contrast medium with an iodine concentration of 370 mg/ml, injected at 6 ml/s. The researchers found the cross-over point between arterial and venous time-density curves to be the most reliable time point to start the regular bolus injection. The radiation dose amounted to 460.8 mGy*cm, which is well below the reference level of 544 mGy*cm for diagnostic head CT.
The subsequent presentation, entitled “Brain perfusion CT using a 256-slice CT: Improvement of diagnostic information by large volume coverage”, was given by F. Dorn from Munich. Her group assessed the feasibility and diagnostic value of CT perfusion with an 8-cm detector. A total of 29 patients with signs of cerebral ischemia were included in the study. The data were compared to those from simulated standard detector CT perfusion at the level of the basal ganglia by two independent readers. Of the 19 lesions identified in this study, 6 would have been missed by standard detector CT perfusion and 10 hypoperfused regions would have only partially been covered.
The last three presentations were given by Z. Jiawen from Shanghai. The first paper,  “ Experimental studies on functional response in normal rat brain to hypercarbia using perfusion CT”, described investigations into changes in CT perfusion values in normal rat brain at hypercarbia and compared these changes to results from immunohistochemical staining. The group found that changes in CBV and CBF correlated well with the number of vessels staining positively for SMA.
The second presentation by Jiawen was called “Experimental studies on functional response of tumoral vasculature to hypercarbia in rat brain C6 glioma model using perfusion CT”. This talk described a study that investigated CT perfusion changes in a rat in vivo glioma model and that found that CT perfusion can reflect angiogenesis in this model. CBV and CBF values under hypercarbia, however, did not correlate well with the number of mature vessels nor with the tumoral vascular maturity index.
Jiawen's third presentation, entitled “Using 64-slice CT perfusion imaging to evaluate the histopathological grade of intracranial gliomas”, described a study that assessed the role of CT perfusion with a 64-slice system in the preoperative grading of cerebral gliomas. The study group included 31 patients with intracranial gliomas who underwent preoperative CT perfusion.  CBV and CBF values correlated well with the grade of the glioma.
In summary, session SS511b provided many insights into the latest advances in neuro-MDCT with a special focus on CT perfusion and 4D-CT angiography.