Sonography of Arteriovenous Fistulas and Grafts.

Arteriovenous fistulas (AVFs) and arteriovenous grafts (AVGs) are the vascular accesses of choice for long-term hemodialysis. Strategies to establish and maintain functioning AVFs and AVGs are essential. In addition to clinical evaluation, ultrasound plays a critical role in the evaluation and maintenance of AVFs and AVGs. AVFs have a high rate of failure to mature which can be reliably diagnosed with ultrasound. Treatable etiologies of the failure to mature can often be diagnosed with ultrasound. Causes of secondary AVG failure can also be diagnosed with ultrasound and treated. AVGs have a relatively short functional life expectancy due to a high rate of AVG thrombosis. Ultrasound is a safe, noninvasive way to diagnose vascular stenosis in both AVFs and AVGs prior to thrombosis, potentially saving the access. Routine surveillance ultrasound of asymptomatic AVFs and AVGs is controversial with conflicting studies on its benefit. Routine surveillance ultrasound of AVFs and AVGs is not common practice.

Risk Evaluation of Immediate Surgical Failure During Thigh Hemodialysis Graft Placement by Sonographic Screening.

OBJECTIVES: The purpose of this study was to determine whether preoperative sonographic evaluation of vascular diameters and calcification identifies patients at risk for immediate technical failure of thigh hemodialysis grafts. METHODS: A retrospective analysis of 143 chronic hemodialysis patients who underwent thigh graft placement was performed. All patients underwent preoperative sonography to assess arterial and venous waveforms and vascular diameters. The degree of arterial calcification was assessed retrospectively. Patient characteristics and graft outcomes were examined. Statistical analyses were performed, with P< .05 considered clinically significant. RESULTS: Sonography identified no or mild arterial calcification in 113 of 143 patients (79%) and moderate to severe calcification in 30 of 143 patients (21%). Primary surgical technical failure occurred in 23% of patients (7 of 30) with moderate to severe calcification, compared to 3.5% (4 of 113) of those with no or mild calcification (hazard ratio, 6.59; 95% confidence interval, 2.06-21.05; P = .002). Cumulative graft survival (time to permanent failure) was shorter in patients with moderate to severe arterial calcification (3-year graft survival, 37% versus 56%; hazard ratio, 2.32; 95% confidence interval, 1.48-6.69; P= .003) but was not significantly associated with venous (P= .82) or arterial (P = .43) diameters. CONCLUSIONS: Preoperative sonographic assessment of thigh vessel diameters and calcification can identify patients who may be at risk for immediate technical graft failure and decreased cumulative graft survival. The use of sonography as a screening examination may improve preoperative assessment and surgical planning of hemodialysis thigh grafts.

Changes in Lower Facial Height and Facial Esthetics with Incremental Increases in Occlusal Vertical Dimension in Dentate Subjects.

PURPOSE: To determine if there are objective changes in lower facial height and subjective changes in facial esthetics with incremental increases in occlusal vertical dimension in dentate subjects. MATERIALS AND METHODS: Twenty subjects of four different races and both sexes with a Class I dental occlusion had custom diagnostic occlusal prostheses (mandibular overlays) fabricated on casts mounted on a semi-adjustable articulator. The overlays were fabricated at 2-mm, 3-mm, 4-mm, and 5-mm openings of the anterior guide pin of a semi-adjustable articulator. Direct facial measurements were made between pronasale and menton on each subject while wearing the four different overlays. Thereafter, two digital photographs (frontal and profile) were taken for each subject at maximum intercuspation (baseline) and wearing each of the four mandibular overlays. The photographs of eight subjects were standardized and displayed in a random order to 60 judges comprising 30 laypeople, 15 general dentists, and 15 prosthodontists. Using a visual analog scale, each judge was asked to rate the facial esthetics twice for each of the 80 images. RESULTS: For objective changes, although an anterior guide pin-lower facial height relationship of 1:0.63 mm was observed, the findings were not correlated (P>.20). For subjective changes, the visual analog scale ratings of judges were uncorrelated with increases in anterior guide pin opening up to 5 mm, irrespective of the judge's background status or the sexes of the judges or the subjects (P>.80). CONCLUSIONS: Incremental increases in anterior guide pin opening up to 5 mm did not correlate to similar increases in lower facial height. Additionally, it made no difference in a judge's evaluation of facial esthetics irrespective of the judge's background status (layperson, general dentist, or prosthodontist) or sex.

Abdominal rapid-kVp-switching dual-energy MDCT with reduced IV contrast compared to conventional MDCT with standard weight-based IV contrast: an intra-patient comparison.

PURPOSE: Perform intra-patient comparison of attenuation values on lower keV dual-energy abdominal CT images using reduced IV contrast dose compared to conventional single energy polychromatic beam abdominal MDCT images using standard IV contrast dose. METHODS: IRB approved retrospective evaluation of consecutive adults who had both standard IV contrast dosage conventional multiphasic MDCT (SECT) and reduced IV contrast dosage rapid kV-switching dual-energy multiphasic MDCT (rsDECT) of the abdomen. Arterial phase dual-energy 52, 70 and 78 keV simulated monoenergetic HU were compared (t test) to arterial phase SECT HU for: aorta, liver, pancreas, psoas, and hepatic/pancreatic tumors. Contrast to noise ratios (CNR), IV contrast dose reduction and dose-length product (DLP) were recorded. Two blinded independent readers evaluated the CT datasets for subjective image quality based on a five point scale. RESULTS: Twenty-nine scan pairs in 24 subjects (13 M, mean age 64, weight 76.7 kg) were evaluated. Mean reduction in IV contrast dose was 37 %. Mean ± SD HU on 52 keV rsDECT vs. SECT were: aorta 534 ± 138 vs. 271 ± 69; liver 88 ± 24 vs. 67 ± 16; pancreas 140 ± 60 vs. 89 ± 40; psoas 63 ± 15 vs. 50 ± 12 (all p < 0.001). Noise was higher for 52 keV compared to SECT (p < 0.001); CNRs were not significantly different. Mean ± SD DLP for rsDECT was 1421 ± 563 and SECT 1335 ± 562 mGy·cm (p = 0.640). For tumor vs. nontumoral parenchyma, mean absolute contrast difference was 58.4 HU on 52 keV, and 29.0 HU on SECT. Nearly all images were rated as good or excellent and there were no statistically significant differences in image quality between the DECT and SECT images. CONCLUSION: Statistically significant gains in vascular and parenchymal enhancement without adverse effect on CNR or lesion contrast were observed in this intra-patient comparison using reduced IV contrast dose rsDECT compared to standard weight-based IV dose conventional SECT.

Multireader evaluation of lesion conspicuity in small pancreatic adenocarcinomas: complimentary value of iodine material density and low keV simulated monoenergetic images using multiphasic rapid kVp-switching dual energy CT.

OBJECTIVE: Perform multireader analysis of objective and subjective lesion conspicuity for small pancreatic adenocarcinomas using rapid switching dual energy CT (rsDECT). MATERIALS AND METHODS: With IRB approval, 51 abdominal multiphasic rsDECT scans in 46 subjects with small (<3 cm) pancreatic adenocarcinomas were retrospectively reviewed by three independent readers for objective and subjective lesion conspicuity. Measured variables during individual, blinded interpretive sessions of separate low (52) keV, PACS-equivalent (70) keV, and iodine material density (MD) image sets included Hounsfield units (HU) and mg/cc iodine for tumor, nontumoral pancreas, and subcutaneous fat. Objective measures included absolute lesion contrast (LC) and contrast to noise ratios (CNR). Subjective measures included image quality, lesion conspicuity, and reader confidence. Reader agreement was measured with kappa statistic; correlation with truth by Pearson coefficient, CNR with repeated mANOVA; subjective quality measures utilized Tukey-Cramer corrections for multiple testing, p < 0.05 considered significant. RESULTS: Demographics: 26 F, 20 M, mean age 68 years, weight 75 kg, tumor size of 2.3 cm. LC was highest on 52 keV images for all three readers (mean 90.1 HU). Mean CNR for iodine MD images (4.87) was significantly higher than 52 keV (4.13) or 70 keV (3.9). Very high to near-perfect kappa values were observed for all individual measured objective variables but were best for 52 keV images (52 keV 0.89-0.95, 70 keV 0.76-0.83, iodine 0.87-0.92). 70 keV images scored best for subjective image quality; iodine MD images scored best for lesion conspicuity and reader confidence. CONCLUSION: We observed very high reader agreement for independent objective rsDECT image variables and subjective rsDECT image scores in patients with small pancreatic adenocarcinomas. Maximal objective tumor to nontumoral LC was depicted on 52 keV and highest CNR on iodine MD images; readers scored the iodine MD images best for lesion conspicuity and confidence.

Postoperative doppler evaluation of liver transplants.

Doppler ultrasound plays an important role in the postoperative management of hepatic transplantation, by enabling early detection and treatment of various vascular complications. This article describes the normal Doppler findings following liver transplantation and reviews the imaging appearances of various vascular complications associated with it. The article also discusses transient waveform abnormalities, often seen on a post-transplant Doppler examination, and the importance of differentiating them from findings suggestive of ominous vascular complications.