B-flow sonographic evaluation of hemodialysis fistulas: a comparison with low- and high-pulse repetition frequency color and power Doppler sonography.

OBJECTIVE: The purpose of this study was to determine the effectiveness of B-flow sonography in the evaluation of hemodialysis fistulas and to compare this new technique with color and power Doppler sonography. METHODS: In this study, 32 randomly selected patients (mean age, 46 years; age range, 18-87 years) with normally functioning hemodialysis fistulas were evaluated with low- and high-pulse repetition frequency (PRF) color and power Doppler sonography (PRF values of 3 and 10 kHz) and B-flow sonography. All images were reviewed and graded independently by 2 observers for luminal filling with flow signals, visibility of the intimal layer, and overall image quality. The study was approved by the Institutional Review Board, and informed consent was obtained from all patients. RESULTS: Statistical analysis with Friedman and Wilcoxon signed rank tests revealed that B-flow sonography was superior to other techniques for luminal filling and visibility of the intimal layer (P = .000). For overall image quality, B-flow sonography was also the best method according to the Friedman test (P = .000). However, the Wilcoxon test showed no significant difference between B-flow and high-PRF (10-kHz) color and power Doppler sonography (P = .131). The kappa scores reflected moderate to good interobserver agreement (kappa = 0.285-0.784). CONCLUSIONS: B-flow sonography is a relatively new and superior imaging technique that provides direct visualization of the blood echoes and the morphologic characteristics of the surrounding vessel wall simultaneously. During the evaluation of hemodialysis shunts, the major advantage of this technique is its ability to avoid artifacts such as aliasing and overwriting.

Evaluation of the normal appendix at low-dose non-enhanced spiral CT.

PURPOSE: To evaluate the frequency of visualization, thickness and location of the normal appendix at non-enhanced spiral computed tomography (CT). MATERIALS AND METHODS: Low-dose spiral CT scans obtained for renal colic assessment in 243 patients were retrospectively reviewed. The frequency of visualization, thickness and location of normal appendices were recorded without knowledge of the patients' history for the appendectomy. RESULTS: Forty of 234 patients had a past history of appendectomy (17%). Sensitivity, specificity, positive and negative predictive values, and accuracy of visualization of the normal appendix were 71%, 85%, 96%, 37% and 73%, respectively. When no intraluminal content was visualized, this area was excluded from the measurement and the mean thickness was 3.4 mm+/-0.66. CONCLUSION: The normal appendix is frequently seen at nonenhanced spiral CT. Knowing the normal thickness of the appendix can help reduce false positive and false negative diagnoses of acute appendicitis when reviewing non-enhanced spiral CT.