State-of-the-science conference on colorectal cancer screening

The US National Institutes of Health (NIH), within its consensus development program, recently held a “state-of-the-science” conference on colorectal cancer screening.  These NIH conferences are organized on emerging healthcare topics for which the evidence may be limited or contradictory, with the aims to illustrate the state of knowledge and to set priorities for future research. During these conferences, the results of a systematic review on the subject are presented, researchers discuss their work, independent panelists (without financial or career interests in the matter) present objective views, and a public debate ensues. The result is the production of a “panel statement” that summarizes current knowledge, without determining a specific healthcare policy.
The most recent NIH state-of-the-science conference was entitled “Enhancing Use and Quality of Colorectal Cancer Screening”.  The speakers, predominantly from the US, addressed topics such as trends in the use and quality of colorectal cancer screening, factors influencing the choice to screen, strategies that increase compliance, medical centers' capacity for screening, and monitoring of screening progress and quality. Two presentations specifically addressed CT colonography: one provided data on the ability of US hospitals to offer CT colonography, and another discussed the training and certification of physicians as well as quality control.  Summaries of these and other presentations are available at consensus.nih.gov.
In the final panel statement, the panelists concluded that the extent of colorectal cancer screening in the US is low and that screening does not reach all population subgroups. To improve this situation, they made several recommendations, including the elimination of "financial barriers" to screening, research on how to tailor screening programs to the needs of particular population subgroups, and cost-benefit analysis of different screening methods. The panel statement is available at consensus.nih.gov.

Toshiba explains its dose- and noise-reducing tools

Maintaining radiation exposure as low as reasonably achievable during CT examinations can be achieved by reducing tube current, but this also reduces image resolution due to a concomitant increase in both quantum noise (random pixel fluctuations) and structured noise (artifacts, such as streaking, due to local areas of high attenuation). Noise can be removed from final images by applying smoothing filters, but if not done accurately resolution and texture can be lost. Manufacturers of CT scanners have made major efforts to develop sophisticated algorithms to reduce noise without losing resolution. For users of Aquilion CT scanners, Toshiba has recently published a white paper describing its two noise-reducing, dose-saving tools.
Quantum Denoising Software (QDS) eliminates quantum noise by selectively applying smoothing and sharpening filters to specific parts of an image, resulting in an enhanced image with preserved contrast.  QDS works together with Aquilion's ^SUREExposure mA modulation system, so that tube current is optimized to both the patient's body constitution and the desired image quality. The second tool, called Boost 3D, eliminates quantum as well as structured noise by searching within the raw data set for areas of low photon count.  Together, these two tools permits radiologists to either improve image quality with a fixed radiation dose, or reduce radiation dose with a fixed image quality. 

References

1. Boedeker K. (2010)   Noise reduction tools:  saving dose with QDS and Boost3D. Toshiba America Medical Systems, Tustin, USA
   

Selected literature update
MDCT for gastrointestinal diseases

Researchers from Bari tested the accuracy of 16-slice MDCT with vessel probe (VP) reconstruction in the preoperative T staging of gastric carcinoma [ 1]. VP software permits reconstruction of gastric wall layers through 3D visualization of arterial vessels during contrast-enhanced imaging. Their study enrolled 53 patients with a diagnosis of gastric adenocarcinoma who underwent MDCT prior to partial or total gastrectomy. Compared to the histological diagnosis made on resected specimens, MDCT with VP reconstruction detected 98% of all lesions (missing one early cancer) and accurately determined T stage in 94% of cases. In contrast, without VP analysis, 90% of lesions were identified but accurately staged in 68%. The authors suggested that incorporation of VP reconstruction in the MDCT workup of these patients is a fast and easy way to improve accuracy.
Pediatric Crohn's disease was the focus of a review offered by researchers working in Ann Arbor (Michigan) [ 2]. Radiological evaluation of Crohn's disease is possible by numerous methods, including CT enterography which reveals both intestinal and extraintestinal manifestations of the disease. The paper describes the CT enterography examination, especially regarding contrast medium administration, image acquisition and radiation exposure control. It then illustrates, with numerous cases, the wide range of CT enterography findings, including bowel and mesentery involvement, penetrating disease, intra-abdominal fluid, bone and urinary tract disease, and finally cholelithiasis.

References

1. Moschetta M., Stabile Ianora AA, Anglani A. et al. (2010)     Preoperative T staging of gastric carcinoma obtained by MDCT vessel probe reconstructions and correlations with histological findings . Eur Radiol 20(1):138-145
   
2. Dillman JR, Adler J., Zimmermann EM, Strouse PJ (2010)     CT enterography of pediatric Crohn disease . Pediatr Radiol 40(1):97-105
   

A catchy rule to guide decisions about CT for minor head trauma in children

Minor pediatric head trauma is a common occurrence that rarely requires neurosurgical intervention. Still, given the fear of intracranial hematoma, emergency physicians often request a CT examination, despite concerns about costs and radiation exposure. Recognizing the need for evidence-based guidelines to support decision-making in this difficult situation, a head injury study group was formed within Pediatric Emergency Research Canada.
The group organized a prospective, 10-center study [ 1 ] to collect clinical and outcome data on children (<17 years of age) who presented with blunt head trauma causing loss of consciousness, amnesia, disorientation or other symptoms and who had a Glasgow Coma Score ≥13. Children underwent a standardized clinical and neurological examination, and CT was performed at the physician's discretion. Clinically important brain injury was defined from CT findings;  in cases in which CT was not done immediately, children were followed up at 14 days and were classified as not having brain injury unless there were signs or symptoms necessitating recall for CT. Univariate analysis was used to identify variables associated with the primary outcome (neurological intervention), and then recursive partitioning was done to find a combination of variables that was both sensitive and specific in predicting this outcome.
Over more than 4 years, the study enrolled 3866 patients of which 24 (0.6%) had neurosurgery. CT was performed in 2043 children (52.8%) and brain injury was diagnosed in 159 cases (4.1%). Recursive partitioning analysis identified seven criteria predictive of brain injury, including four that defined patients at high risk: Glasgow Coma Score <15 two hours after injury, evidence of open or depressed skull fracture, worsening headache and irritability. These four criteria had 100% sensitivity and 70.2% specificity, and implied that about 30% of children with minor head trauma should have a CT examination. The clinical decision rule based on all seven criteria, termed Canadian Assessment of Tomography for Childhood Head Injury (CATCH), is expected to help standardize – and minimize – the use of CT for minor pediatric head trauma.

References

1. Osmond MH, Klassen TP, Wells GA et al. (2010)   CATCH: a clinical decision rule for the use of computed tomography in children with minor head injury. CMAJ Feb 8. [Epub ahead of print]