Single-source dual-energy spectral multidetector CT of pancreatic adenocarcinoma: optimization of energy level viewing significantly increases lesion contrast.

AIM: To evaluate lesion contrast in pancreatic adenocarcinoma patients using spectral multidetector computed tomography (MDCT) analysis. MATERIALS AND METHODS: The present institutional review board-approved, Health Insurance Portability and Accountability Act of 1996 (HIPAA)-compliant retrospective study evaluated 64 consecutive adults with pancreatic adenocarcinoma examined using a standardized, multiphasic protocol on a single-source, dual-energy MDCT system. Pancreatic phase images (35 s) were acquired in dual-energy mode; unenhanced and portal venous phases used standard MDCT. Lesion contrast was evaluated on an independent workstation using dual-energy analysis software, comparing tumour to non-tumoural pancreas attenuation (HU) differences and tumour diameter at three energy levels: 70 keV; individual subject-optimized viewing energy level (based on the maximum contrast-to-noise ratio, CNR); and 45 keV. The image noise was measured for the same three energies. Differences in lesion contrast, diameter, and noise between the different energy levels were analysed using analysis of variance (ANOVA). Quantitative differences in contrast gain between 70 keV and CNR-optimized viewing energies, and between CNR-optimized and 45 keV were compared using the paired t-test. RESULTS: Thirty-four women and 30 men (mean age 68 years) had a mean tumour diameter of 3.6 cm. The median optimized energy level was 50 keV (range 40-77). The mean ± SD lesion contrast values (non-tumoural pancreas - tumour attenuation) were: 57 ± 29, 115 ± 70, and 146 ± 74 HU (p = 0.0005); the lengths of the tumours were: 3.6, 3.3, and 3.1 cm, respectively (p = 0.026); and the contrast to noise ratios were: 24 ± 7, 39 ± 12, and 59 ± 17 (p = 0.0005) for 70 keV, the optimized energy level, and 45 keV, respectively. For individuals, the mean ± SD contrast gain from 70 keV to the optimized energy level was 59 ± 45 HU; and the mean ± SD contrast gain from the optimized energy level to 45 keV was 31 ± 25 HU (p = 0.007). CONCLUSION: Significantly increased pancreatic lesion contrast was noted at lower viewing energies using spectral MDCT. Individual patient CNR-optimized energy level images have the potential to improve lesion conspicuity.

Pseudoephedrine and guaifenesin urolithiasis: widening the differential diagnosis of radiolucent calculi on abdominal radiograph.

Unenhanced helical computed tomography has played an increasingly important role in the management of urinary tract stones, guiding diagnosis and control of calculus disease. We report computed tomographic and radiographic appearances of a renal calculus composed of pseudoephedrine and guaifenesin in a patient who abused over-the-counter allergy medication.

Effect of preoperative sonographic mapping on vascular access outcomes in hemodialysis patients.

BACKGROUND: Current DOQI guidelines encourage placing arteriovenous (AV) fistulas in more hemodialysis patients. However, many new fistulas fail to mature sufficiently to be usable for hemodialysis. Preoperative vascular mapping to identify suitable vessels may improve vascular access outcomes. The present study prospectively evaluated the effect of routine preoperative vascular mapping on the type of vascular accesses placed and their outcomes. METHODS: During a 17-month period, preoperative sonographic evaluation of the upper extremity arteries and veins was obtained routinely. The surgeons used the information obtained to plan the vascular access procedure. The types of access placed, their initial adequacy for dialysis, and their long-term outcomes were compared to institutional historical controls placed on the basis of physical examination alone. RESULTS: The proportion of fistulas placed increased from 34% during the historical control period to 64% with preoperative vascular mapping (P < 0.001). When all fistulas were assessed, the initial adequacy rate for dialysis increased mildly from 46 to 54% (P = 0.34). For the subset of forearm fistulas, the initial adequacy increased substantially from 34 to 54% (P = 0.06); the greatest improvement occurred among women (from 7 to 36%, P = 0.06) and diabetic patients (from 21 to 50%, P = 0.055). In contrast, the initial adequacy rate of upper arm fistulas was not improved by preoperative vascular mapping (59 vs. 56%, P = 0.75). Primary access failure was higher for fistulas than grafts (46.4 vs. 20.6%, P = 0.001), but the subsequent long-term failure rate was higher for grafts than fistulas (P < 0.05). Moreover, grafts required a threefold higher intervention rate (1.67 vs. 0.57 per year, P < 0.001) to maintain their patency. The overall effect of this strategy was to double the proportion of patients dialyzing with a fistula in our population from 16 to 34% (P < 0.001). CONCLUSIONS: Routine preoperative vascular mapping results in a marked increase in placement of AV fistulas, as well as an improvement in the adequacy of forearm fistulas for dialysis. This approach resulted in a substantial increase in the proportion of patients dialyzing with a fistula in our patient population. Fistulas have a higher primary failure rate than grafts, but have a lower subsequent failure rate and require fewer procedures to maintain their long-term patency.

Hemodialysis access ultrasound.

Maintenance of hemodialysis graft and fistula patency is becoming even more important as the number of patients with end-stage renal disease increases. There are two major categories of dialysis access: native arteriovenous fistula (AVF) and synthetic arteriovenous graft. Arteriovenous fistulas have superior longevity after maturation and are the recommended type of hemodialysis access, if possible. However, AVFs have a higher rate of primary failure as compared with grafts. Close monitoring has been shown to prolong access survival. Ultrasound is a noninvasive means of imaging for access complications. Ultrasound is sensitive in detection of access or draining vein stenosis. Ultrasound is also useful in the evaluation of other graft or fistula abnormalities, such as pseudoaneurysm, steal, or infection. Careful attention to technical detail is required, and avoidance of several diagnostic pitfalls is necessary.

Carotid artery stents: early and intermediate follow-up with Doppler US.

PURPOSE: To determine whether ultrasound (US) is a sensitive follow-up method after placement of a carotid artery stent for the detection of significant stenosis, occlusion, and other complications at early and intermediate follow-up. MATERIALS AND METHODS: Doppler US examinations were performed after stent placement in 170 carotid arteries in 119 patients with angiographic correlation. Prospective diagnostic US criteria for stenosis were peak-systolic velocity greater than 1.25 m/sec, internal carotid artery (ICA) to common carotid artery (CCA) peak-systolic velocity ratio of greater than or equal to 3:1, and intrastent doubling of peak-systolic velocity. Retrospective criteria for stenosis were also applied: peak-systolic velocity greater than 1.7 m/sec, ICA end-diastolic velocity greater than 0.4 m/sec, ICA/CCA peak-systolic velocity ratio greater than 2.0, and ICA/CCA end-diastolic velocity ratio greater than 2.4. RESULTS: Eighty-seven immediate and 83 intermediate (average, 7.3 months) follow-up US examinations were performed. Two stent occlusions were detected. One or more prospective US criteria were abnormal in 26 arteries with a stent. One or more retrospective criteria were positive in 47 arteries. Angiography showed corresponding findings, with only one significant stenosis (63%) in the ICA stents. Moderate collapse of a CCA stent was depicted at US. CONCLUSION: Only one significant recurrent stenosis was detected, and no significant stenoses were missed at US. US successfully depicted carotid artery stent occlusion and a moderate stent collapse. Sensitivity in the detection of intrastent stenosis is promising. Further study to refine US criteria in a study with longer term follow-up is needed owing to the lack of significant recurrent stenosis in the intermediate follow-up group.