Marc Keberle

Chronic thromboembolic pulmonary hypertension: Evaluation with 64-detector row CT versus digital substraction angiography

The aim of the study was to evaluate the role of 64-row CT in the diagnostic workup of patients with chronic thromboembolic pulmonary hypertension (CTEPH) using digital substraction angiography (DSA) as the method of diagnostic reference. CT and DSA studies of 27 patients (54 main, 162 lobar and 540 segmental arteries) with a clinical suspicion of CTEPH were included in this retrospective and blinded analysis. Axial images and multiplanar thin maximum intensity projections (MIPs) (3mm) were consequently used for exact image interpretation whereas additional reconstructed thick MIPs gave an overview of the entire vascular tree comparable to DSA. Sensitivity and specificity of CT regarding CTEPH-related pathological changes in general were 98.3% and 94.8% at main/lobar level and 94.1% and 92.9% at segmental level, respectively. Sensitivity and specificity of CT regarding the different pathological criteria of CTEPH (complete obstruction, intimal irregularities, bands and webs, indirect signs) were 88.9-100% and 96.1-100% at main/lobar level and 84.3-90.5% and 92-98.7% at segmental level, respectively. Our results show that CT is an accurate and reliable non-invasive alternative to conventional DSA in the diagnostic workup in patients with CTEPH.

Transhepatic Preoperative Portal Vein Embolization Using the Amplatzer Vascular Plug: Report of Four Cases

The Amplatzer Vascular Plug (AVP) is a device originally intended for arterial and venous embolization in peripheral vessels. From December 2004 to March 2007 we implanted a total of 8 AVPs in the portal venous system in our institution for preoperative portal vein embolization in 4 patients (55–71 years) prior to right hemihepatectomy. AVP implantation was successful in all patients. Total occlusion of the embolized portal vein branches was achieved in all patients. There were no major complications associated with the embolization.

Comparison of the image quality of various fixed and dose modulated protocols for soft tissue neck CT on a GE Lightspeed scanner

PURPOSE Up-to-date CT scanners provide high quality soft tissue imaging of the neck, but scanning protocols often are not optimized regarding radiation dose. Thus, we tried to find a dose-optimized protocol for soft tissue imaging of the neck. MATERIAL AND METHODS 70 patients were scanned with a 16-row CT-scanner (Lightspeed, GE) with seven different protocols. We used four fixed tube current settings (225, 200, 175 and 150 mA; corresponding CTDI(vol)=10.6, 9.5, 8.3 and 7.1 mGy) and three z-axis dose modulations with a relatively high, moderate and low dose (calculated CTDI(vol)=10.5, 9.1, 7.7 mGy). Representative slices of seven anatomical regions (from the nasopharynx to the aortic arch) were subjectively judged by two radiologists with respect to image quality (five-point rating scale for noise and sharpness). For each protocol and for each judged anatomical region we determined and compared mean values regarding image quality and local tube current. For each protocol, mean values regarding the volume CT dose index (CTDI(vol)) and the dose-length product (DLP) were statistically compared. Moreover, using the software CT-Expo the respective effective doses and the cumulative organ doses of the thyroid gland were compared. RESULTS For a fixed tube current of at least 200 mA (CTDI(vol)=9.5 mGy) and for dose modulations with a moderate or high dose adjustment (calculated CTDI(vol)=9.1 and 10.5 mGy) the image quality was sufficient to excellent. As compared to a fixed tube current of 200 mA, dose modulation with a moderate dose adjustment improved the image quality in regions more vulnerable to noise-related artifacts such as at the level of the shoulder, without a noteworthy difference regarding the DLP. However, the cumulative organ dose of the thyroid gland was 17% lower using dose modulation with a moderate dose adjustment as compared to the fixed tube current of 200 mA. Thus, for a comparison with other scanners, we recommend dose modulation and an averaged CTDI(vol)<9 mGy (or a DLP<250 mGycm). CONCLUSION A combination of dose modulation and an averaged CTDI(vol)<9 mGy or a DLP<250 mGycm yields sufficient image quality for soft tissue CT-imaging of the neck.