The radiocephalic arteriovenous fistula remains the method of choice for haemodialysis access. In order to assess their suitability for fistula formation, the radial arteries and cephalic veins were examined preoperatively by ultrasound colour flow scanner in conjunction with a pulse-generated run-off system. Intraoperative blood flow was measured after construction of the fistulae. Post-operative follow-up was performed at various intervals to monitor the development of the fistulae. Radial artery and cephalic vein diameter less than 1.6 mm was associated with early fistula failure. The intraoperative fistula blood flow did not correlate with the outcome of the operation probably due to vessel spasm from manipulation. However, blood flow velocities measured non-invasively 1 day after the operation were significantly lower in fistulae that failed early compared with those that were adequate for haemodialysis. Most of the increase in fistula diameter and blood flow occur within the first 2 weeks of surgery.

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The purpose of this study was to test the hypothesis that decreasing liver perfusion in rabbits results in an increase in thermal lesion size and that these effects can be accurately monitored using magnetic resonance imaging (MRI). We additionally tested the hypothesis that the increase in thermal lesion size would depend on the particular vessel or vessels occluded (hepatic artery, portal vein, or both). Using an Institutional Animal Care and Use Committee approved protocol, 20 New Zealand white rabbits were randomly assigned to four treatment groups (five in each group): control and ligation of portal vein (PV), hepatic artery (HA), or both PV and HA (HAPV). Surgical ligation of the appropriate vessel was performed under general anesthesia. Immediately after ligation, the rabbits were placed in a 0.2‐T open MR system, and an 18‐G copper radiofrequency (RF) electrode with a 2‐cm exposed tip was inserted into the liver. RF was applied for 10 minutes with the tip temperature maintained at 90° ± 2°C. Before and after ablation, perfusion data were obtained for 90 seconds using 30 3‐second sequential single oblique‐slice fast imaging with steady‐state progression (FISP) acquisitions after injection of gadolinium‐diethylene triamine pentaacetic acid (Gd‐DTPA) via the inferior vena cava. Postablation scanning included axial and oblique turbo spin‐echo (TSE) T2‐weighted (T2w), STIR, and Gd‐enhanced T1w sequences. Lesion size was determined perpendicular to the RF electrode using software calipers on the imager. The rabbits were sacrificed after completion of the post‐therapy scans, and their livers were harvested for histologic analysis. The liver showed a mean increase in signal amplitude (SA) of 76% 24 seconds after Gd contrast injection in the control group. After contrast injection, the SA increased to a mean of only 66% in the group with ligated hepatic arteries, with no difference in the time to peak compared with the control group. No significant SA increase over baseline could be found in the groups with ligated PV or ligated PV and HA. T2‐weighted images demonstrated the highest lesion‐to‐liver contrast‐to‐noise ratios (CNRs; mean −5.5) on postprocedure images, followed by STIR images (mean −2.2) in the control group. The lesions were poorly delineated on the Gd‐enhanced images. Average maximum lesion sizes (mean ± 95% confidence interval) were 22 ± 4.3 mm after ligation of PV, 22 ± 2.6 mm after ligation of both PV and HA, 14 ± 2.0 mm after ligation of HA, and 13 ± 1.9 mm in the control group. We accept the hypothesis that the diameter of the region of coagulation necrosis achieved by standardized RF ablation in the liver increases with reduced organ perfusion and that this effect can be accurately monitored using MRI. The major factor influencing the size of the coagulation area is the portal venous flow. Occlusion of the hepatic artery alone does not significantly increase lesion size. T2w sequences are best suited for postprocedure imaging due to the high lesion‐to‐liver CNR in rabbits with normal ...