Stefaan Gryspeerdt

Determination of scan delay time in spiral CT-angiography: utility of a test bolus injection

Objective The usefulness of a test bolus of contrast medium for predicting the optimal scan delay time in spiral CT-angiography (CTA) was determined. Materials and Methods Two axial single level CT studies were performed at the level of the pancreas in 20 patients, first after injection of a 12 ml “test” bolus, second after administration of a 90 ml bolus. The titne interval between the start of the test bolus injection and peak aortic enhancement (T-peak) was measured and compared with the time required to reach a 50, 100, and 150 HU level of aortic enhancement after 90 ml bolus injection. Results The time required to reach 50, 100, and 150 HU enhancement during the 90 ml bolus was largely variable (tnean SD 4.9 s). The T-peak varied between 11 and 32 s (mean 20, SD 6.1 s). There was a strong correlation between the T-peak and the titne to the different levels of enhancement during the 90 ml bolus (R2 ± 0.83). The mean titne to 50, 100, and 150 HU enhancement was T-peak - 3.3 s (SD 2.5 s), T-peak - 1.2 s (SD 2.4 s), and T-peak + 1.3 s (SD 2.4 s). Conclusion The injection of a test bolus improves the timing of a spiral CTA acquisition. Index Terms Contrast media—Computed totnography, techniques—Computed tomography, spiral.

Supine/left decubitus scanning: a valuable alternative to supine/prone scanning in CT colonography

The purpose was to evaluate supine/left decubitus as an alternative to supine/prone scanning in computed tomographic colonography (CT colonography). Fifty patients were randomised to supine/prone, another 50 to supine/left decubitus scanning. Patients were scanned using a single-slice CT scanner. The colon was divided into eight segments. Comparisons of distension, breathing artefacts, residus and polyp detection were made between the two groups as well as between the different positions. Adequate distension was found in approximately 85, 97 and 95% of segments in the supine, prone and left decubitus positions, respectively. Combined scanning increased the percentage of adequate distension to 98.5% for prone-supine and 97.7% for left decubitus-supine scanning (P<0.0005 compared to supine, P=0.001 compared to left decubitus and P=0.046 compared to prone scanning). Absence of residual material was found in approximately 62.7, 69.7 and 64% of segments in the supine, prone and left decubitus positions, respectively. Combined scanning increased this percentage to approximately 99% for both groups. No significant differences towards distension or residual material were found between combined supine-prone or supine-left decubitus scanning. In the supine-prone group, combined scanning additionally revealed four lesions and improved conspicuity in two cases of stalked polyps. In the supine-left decubitus group, combined scanning additionally revealed two lesions and improved conspicuity in one stalked polyp. There were significantly fewer breathing artefacts with left decubitus scanning than prone scanning (P=0.005). A strong positive correlation was found between breathing artefacts and the age of patients in both patient groups. Colonic distension and preparation is improved by using supine and prone or supine and left decubitus scanning in combination, with a subsequent improved polyp detection. There were no significant differences between the two scanning protocols. Prone scanning, however, is hampered by breathing artefacts, especially in the elderly. Therefore, supine-left decubitus scanning is considered a valuable alternative to supine-prone scanning for the elderly.

CT colonography with fecal tagging after incomplete colonoscopy

The objective of this study was to evaluate dietary fecal tagging (FT) as a cleansing method prior to CT colonography (CTC) in patients with incomplete conventional colonoscopy (CC). After written informed consent was obtained, 24 patients had standard colonoscopic preparation (ScCl), and 25 patients had FT as cleansing method. Segmental distention, fluid levels, fecal residues, tagged appearance of fluid levels, and residual stool were evaluated. Mann–Whitney U test was used to test for significant differences between FT and ScCl groups. Compared with ScCl, FT improved distention (p=0.001), reduced the amount of fluid (p=0.043), but suffered from residual stool (p=0.046). A clear correlation was found between distention and fluid. No differences were found in stool size between FT and ScCl. FT showed a good labeling of fecal residues, and acceptable labeling of fluid levels. Compared with ScCl, FT reduces fluid, favors distention, but suffers from fecal residues. The tagged nature of these residues, however, allows differentiation from polyps.

Spiral CT of intracranial aneurysms : correlation with digital subtraction and magnetic resonance angiography

Spiral CT and magnetic resonance angiography (MRA) were performed in ten patients with 14 intracranial aneurysms known from conventional angiography. All lesions, the smallest 3 mm in diameter, were visible on spiral CT and MRA. The neck of the aneurysm and its anatomical relations could very accurately be determined in all cases. Advantages of spiral CT over MRA are: a short acquisition time with reduction of motion artefacts, no dependence on flow rate or cardiac output, and excellent visualisation of calcification, thrombus and bony landmarks. Disadvantages are the necessity for iodinated contrast medium, long postprocessing and reconstruction time and the possibility of overlap of bone and venous blood.

Assessment of accuracy of renal artery stenosis grading in helical CT angiography using maximum intensity projections

The purpose of the study was to investigate whether visual inspection of maximum intensity projection (MIP) images is a reliable method for assessment of the severity of renal artery stenoses (RAS). Therefore, 20 RAS were investigated with helical CT. Native axial images and MIP images were analysed separately or in combination (“two-step method”). A phanton study was performed to investigate the influence of window setting on apparent stenosis severity. Accuracy for diagnosis of 50–69% and 70–99% RAS and the mean inter-observer agreement were 82.5%, 77.5% and 82.5% respectively, using study of MIP images alone, and 100%, 97.5% and 95% using the “two-step method”. The phantom study showed that the apparent severity of vascular stenoses on MIP images depends on the selected window centre values. It is concluded that combined evaluation of both MIP images and native axial images is more reliable than study of MIP images alone for assessing the severity of RAS.

Diagnosis and treatment of expanding haematoma of the lateral abdominal wall after blunt abdominal trauma

Abstract. We report a rare case of an expanding post-traumatic lateral abdominal wall haematoma. A superselective arteriogram of the deep circumflex iliac artery showed extravasation from the ascending branch, urging emergency therapy. Microcoil and Gelfoam embolisation was successfully performed. Haematomas of the abdominal wall can be divided in the common rectus sheath haematomas and the rare haematomas of the lateral abdominal wall. Differentiating both entities is essential, since there is a strong difference in their vascular supply. The typical vascular supply of the lateral abdominal wall is discussed, with emphasis on the ascending branch of the deep circumflex iliac artery.

Case report: pseudotumoral pelvic retroperitoneal fibrosis associated with orbital fibrosis

We report the case of a man with bilateral orbital fibrous pseudotumours and a large pelvic mass which was initially thought to be malignant. Sonographically guided transrectal core biopsies showed it to be a fibrotic retroperitoneal pseudotumour. The mass decreased after steroid therapy. The computed tomography and magnetic resonance imaging features of this unusual form of pelvic fibrosis as well as the association with heterotopic fibrosis are discussed.

Bowel preparation for CT colonography

Bowel preparation represents an essential part of CT colonography, as the accuracy of the exam is strongly related to the adequacy of colonic cleansing, and a poor bowel preparation may compromise the diagnostic quality even despite optimization of all other acquisition parameters. Residual stool and fluid in the large bowel may affect the interpretation of the exam and may increase the number of false positives and false negatives. In this regard, the majority of patients having undergone CT colonography state that bowel preparation is the most unpleasant part. Unfortunately, to date no definite consensus has been reached about the ideal bowel preparation technique, and there is great variability in preparation strategies across diagnostic centers. The purpose of this review article is to describe the development and evolution of bowel preparation techniques in order to choose the best approach for optimizing the diagnostic quality of CT colonography in each patient.

Computed tomographic colonography: clinical value.

Computed tomographic colonography (CTC) has the potential to reliably detect polyps in the colon. Its clinical value is accepted for several indications. The main target is screening asymptomatic people for colorectal cancer (CRC). As in large multi-centre trials controversial results were obtained, acceptance of this indication on a large scale is still pending. Agreement exists that in experienced hands screening can be performed with CTC. This emphasizes the importance of adequate and intensive training. Besides this, other problems have to be solved. A low complication profile is mandatory. Perforation rate is very low. Ultra-low dose radiation should be used. When screening large patient cohorts, CTC will need a time-efficient and cost-effective management without too many false positives and additional exploration. Can therefore a cut-off size of polyp detection safely be installed? Is the flat lesion an issue? Can extra-colonic findings be treated efficiently? A positive relationship with the gastro-enterologists will improve the act of screening. Improvements of scanning technique and software with dose reduction, improved 3D visualisation methods and CAD are steps in the good direction. Finally, optimisation of laxative-free CTC could be invaluable in the development of CTC as a screening tool for CRC.

Teleradiology based CT colonography to screen a population group of a remote island; at average risk for colorectal cancer

PURPOSE To prospectively assess the performance of teleradiology-based CT colonography to screen a population group of an island, at average risk for colorectal cancer. MATERIALS AND METHODS A cohort of 514 patients living in Madeira, Portugal, was enrolled in the study. Institutional review board approval was obtained and all patients signed an informed consent. All patients underwent both CT colonography and optical colonoscopy. CT colonography was interpreted by an experienced radiologist at a remote centre using tele-radiology. Per-patient sensitivity, specificity, positive (PPV) and negative (NPV) predictive values with 95% confidence intervals (95%CI) were calculated for colorectal adenomas and advanced neoplasia ≥6 mm. RESULTS 510 patients were included in the study. CT colonography obtained a per-patient sensitivity, specificity, PPV and, NPV for adenomas ≥6 mm of 98.11% (88.6-99.9% 95% CI), 90.97% (87.8-93.4% 95% CI), 56.52% (45.8-66.7% 95% CI), 99.75% (98.4-99.9% 95% CI). For advanced neoplasia ≥6 mm per-patient sensitivity, specificity, PPV and, NPV were 100% (86.7-100% 95% CI), 87.07% (83.6-89.9% 95% CI), 34.78% (25.3-45.5% 95% CI) and 100% (98.8-100% 95% CI), respectively. CONCLUSION In this prospective trial, teleradiology-based CT colonography was accurate to screen a patient cohort of a remote island, at average risk for colorectal cancer.