[Evaluation of image quality of two different three-dimensional cone-beam-scanners used for orthopedic surgery in the bony structures of the pelvis in comparison with standard CT scans]. / Vergleich der Bildqualität zweier unterschiedlicher mobiler 3-dimensionaler Röntgen-C-Bögen mit einem konventionellen CT bei der Darstellung relevanter Strukturen am knöchernen Becken.

AIM: This study evaluated the image quality of two different cone beam CT scanners used in the operation theatre in pelvic trauma surgery in relation to their radiation dosage. Furthermore, the assumption that a higher dosage would result in better image quality was analysed by using the different acquisition scanner modes. MATERIAL AND METHODS: We scanned the acetabulum (n=4) and iliosacral joints (n=4) of two human cadavers with a conventional CT and with two mobile cone beam CT scanners (Siemens Arcadis Orbic 3D and Ziehm Vision Vario 3D). With the two cone beam CT scanners (3D-BV), we used 6 different acquisition modes with different radiation dosages. The axial views of all scans were exported and blinded. Subsequently, the images were evaluated by 7 medical doctors with regard to identifiability of cortical structures (acetabular joint, fovea capitis femoris, cortical bone of the femur head, iliosacral joint, and sacral foramina), and the quality of the cancellous structure of the femur head. The evaluation was performed on axial views by using a defined five-point score. The interrater quality was statistically analysed according to Cohen with the kappa coefficient. In addition, the Wilcoxon test was used to identify significances between the 21 paired results of the evaluators. For determination of the signal-to-noise ratio, a Catphan 600 reference block with two different test elements (Teflon, PMP) was used. RESULTS: Overall, the image quality of the conventional CT scans received the best score. Comparing the two 3D cone beams, the image quality of the Siemens Arcadis Orbic 3D in high-dosage mode received the best score (median: 2.40), the Ziehm Vision Vario 3D in low-dose mode without large patient key received the lowest score (median: 3.16). The differences in the 21 paired results of the two different acquisition modes were significant in 17 cases (p < 0.05) but the size of difference when comparing the different acquisition modes was almost always small. The interobserver agreement in one acquisition mode was low (kappa 0.008-0.134). The overall evaluation results of the same acquisition mode diverged by up to 2 score points. We noted a higher signal-to-noise ratio in the high dosage mode than in the low dosage mode. DISCUSSION: When using intraoperative 3D imaging with the cone beam CT technique for pelvic injury, image acquisition in low-dose mode is adequate in terms of signal-to-noise ratio and image quality. The image quality does not correlate linearly with a higher radiation dosage. Therefore, the pelvic trauma surgeon using this technique is encouraged to gather his own experience with low dose modes thereby reducing patient radiation exposure.

Covered stents are better than uncovered stents for transjugular intrahepatic portosystemic shunts in cirrhotic patients with refractory ascites: a retrospective cohort study.

BACKGROUND AND STUDY AIMS: Transjugular intrahepatic portosystemic shunt (TIPS) is an accepted interventional technique to treat refractory ascites in cirrhotic patients with severe portal hypertension. The expanded-polytetrafluoroethylene (e-PTFE) covered stent-graft (cs-TIPS) gives a better shunt patency rate than uncovered stents (ncs-TIPS). Our aim was to retrospectively evaluate whether cs-TIPS indeed improves refractory ascites and overall survival in a more effective way than ncs-TIPS in patients with cirrhosis. PATIENTS AND METHODS: From 1992 to 2006, 222 cirrhotic patients with refractory ascites underwent a TIPS-procedure. In 126 patients a ncs-TIPS was inserted, in the remaining 96 patients a csTIPS was inserted. Liver transplantation and/or death were the end points of the follow-up. RESULTS: The baseline characteristics of both groups were similar: age (55 +/- 11 years, ncs-TIPS/56 +/- 10 years, cs-TIPS), alcoholic cirrhosis (73% ncs-TIPS/80% cs-TIPS), Child-Pugh (9 +/- 2.0 ncs-TIPS/9.2 +/- 1.3 cs-TIPS) and MELD (15 +/- 6 ncs-TIPS/15 +/- 4.9 cs-TIPS), except that the bilirubin level was higher in the cs-TIPS group (2.5 +/- 2.7 mg/dL in cs-TIPS vs. 1.5 +/- 3.6 mg/dL in ncs-TIPS). One year shunt dysfunction occurred in 49% (n=63) of the ncs-TIPS vs. 19% (n = 18) of the cs-TIPS (P < 0.0001) and post TIPS encephalopathy in 56% (n=70) of the ncs-TIPS vs. 22% (n = 22) in the cs-TIPS group. Ascites control and overall survival were better in the cs-TIPS (P = 0.0071). The gain in survival in the cs-TIPS patients occurred especially in patients with a baseline MELD score <16 (P < 0.0001). Post TIPS encephalopathy and ncs-TIPS were independently related with poor survival (P < 0.0001, P = 0.0150; respectively). CONCLUSIONS: In cirrhotic patients with refractory ascites cs-TIPS offers better symptomatic control of the ascites at one year follow-up and a better overall survival, especially in patients with a MELD score of <16 at baseline.