Robert G. Sheiman

PERCUTANEOUS RADIOFREQUENCY TISSUE ABLATION : OPTIMIZATION OF PULSED-RADIOFREQUENCY TECHNIQUE TO INCREASE COAGULATION NECROSIS

PURPOSE To develop a computerized algorithm for pulsed, high-current percutaneous radiofrequency (RF) ablation, which maximally increases the extent of induced coagulation necrosis. MATERIALS AND METHODS An automated, programmable algorithm for pulsed-RF deposition was designed to permit high-current deposition by periodically reducing current for 5-30 seconds during RF application. Two strategies for pulsed-RF deposition were evaluated: (i) constant peak current (900-1,800 mA) of variable duration and (ii) variable peak current (1,200-2,000 mA) for a specified minimum duration. The extent of induced coagulation was compared to results obtained with continuous (lower current) RF application. Trials were performed in ex vivo calf liver (n = 115) and in vivo porcine liver (n = 30) and muscle (n = 18) with use of 2-4-cm tip, internally cooled electrodes. RESULTS For 3-cm electrodes in ex vivo liver, applying pulsed-RF with constant peak current for 12 minutes produced 3.5 cm +/- 0.2 of necrosis. Greater necrosis was produced with use of the variable current strategy, in which 4.5 cm +/- 0.2 of coagulation was achieved with use of an initial current > or =1,500 mA (minimum peak-RF duration of 10 sec, with 15 sec of reduced current to 100 mA between peaks; P < .01). This variable peak current algorithm also produced 3.7 cm +/- 0.6 of necrosis in in vivo liver, and 6.5 cm +/- 0.9 in in vivo muscle. Without pulsing, a maximum of 750 mA, 1,100 mA, and 1,500 mA could be applied in ex vivo liver, in vivo liver, and in vivo muscle, respectively, which resulted in 2.9 cm +/- 0.2, 2.4 cm +/- 0.2, and 5.1 cm +/- 0.4 of coagulation (P < .05, all comparisons). CONCLUSIONS A variable peak current algorithm for pulsed-RF deposition can increase coagulation necrosis diameter over other ablation strategies. This innovation may ultimately enable the percutaneous treatment of larger tumors.

Restoration of Patency in Failing Tunneled Hemodialysis Catheters: A Comparison of Catheter Exchange, Exchange and Balloon Disruption of the Fibrin Sheath, and Femoral Stripping

PURPOSE To compare median patency times after treatment of malfunctioning tunneled hemodialysis catheters by one of three techniques: over-the-wire catheter exchange (CE), fibrin sheath stripping (FSS) from a femoral vein approach, and over-the-wire catheter removal with balloon dilation of fibrin sheath (DFS) followed by catheter replacement with use of the same tract. MATERIALS AND METHODS Retrospective study was conducted of 66 consecutive procedures performed over a period of 47 months for poor flow through tunneled hemodialysis catheters despite tissue plasminogen activator infusion trials (CE, n=33; FSS, n=18; DFS, n=15). Baseline parameters (time since initial catheter placement, number of previous catheter interventions, catheter access site, and patient age and sex) were recorded to identify possible pretreatment differences among groups. Outcome comparison was based on duration of adequate catheter function on dialysis during follow-up. RESULTS No significant differences in baseline parameters were identified among the three groups (P>.05). Mean follow-up duration (67+/-89 days; range, 0-398 d) was similar among the three groups. The immediate technical success rate was 100%, and there were no complications. Cumulative catheter patency rates were 73% (CE), 72% (FSS), and 65% (DFS) at 1 month; 43% (CE), 60% (FSS), and 39% (DFS) at 3 months; and 28% (CE), 45% (FSS), and 39% (DFS) at 6 months. Median duration of patency was similar among groups (P=.60). CONCLUSIONS All three therapies were equivalent in terms of immediate technical success, complication rates, and durability of catheter function during later follow-up. Hence, when one technique is chosen over another, factors other than the period of secondary patency should be considered, such as cost and patient and physician preference.

Transhepatic Mechanical Thrombectomy Followed by Infusion of TPA into the Superior Mesenteric Artery to Treat Acute Mesenteric Vein Thrombosis

Abbreviations: SMA superior mesenteric artery, SMV superior mesenteric vein, TPA plasminogen activator ACUTE mesenteric vein thrombosis can be caused by a variety of factors including cirrhosis, neoplastic disease, intra-abdominal inflammatory diseases (most commonly pancreatitis), and hypercoagulable states (1). The clinical presentation can be varied and includes abdominal pain, nausea, vomiting, melena, or diarrhea (2). Recent advances in mechanical thrombectomy devices, such as the AngioJet catheter (3), have produced a new set of therapeutic options for treatment of vascular thrombosis. We present our experience using the AngioJet catheter to achieve rapid restoration of portal venous flow in a patient with acute thrombosis of the portal and superior mesenteric veins.

Efficacy of Radiofrequency Ablation in the Treatment of Small Functional Adrenal Neoplasms

PURPOSE To evaluate the use of radiofrequency (RF) ablation as a primary treatment for symptomatic primary functional adrenal neoplasms and determine the efficacy of treatment with use of clinical and biochemical follow-up. MATERIALS AND METHODS After obtaining institutional review board approval, the authors retrospectively evaluated images and medical records from 13 consecutive patients with symptomatic functional adrenal neoplasms (<3.2 cm in diameter) who underwent RF ablation during a 7-year period. There were six men and seven women with a mean age of 54.1 years (range, 42-71 years). Cross-sectional images, findings from clinical examination, and adrenal biochemical markers were available for all patients. Ten of the 13 patients (77%) had an aldosteronoma and one patient each had a cortisol-secreting tumor, testosterone-secreting tumor, and pheochromocytoma. RF ablation was performed by two radiologists using an internally cooled electrode and a pulsed technique according to manufacturers specifications. Clinical and laboratory follow-up was performed for all patients. Three patients underwent imaging follow-up for other reasons. RESULTS All patients demonstrated resolution of abnormal biochemical markers after ablation (mean biochemical follow-up, 21.2 months). In addition, all patients experienced resolution of clinical symptoms or syndromes, including hypertension and hypokalemia (in patients with aldosteronoma), Cushing syndrome (in the patient with cortisol-secreting tumor), virilizing symptoms (in the patient with testosterone-secreting tumor), and hypertension (in the patient with pheochromocytoma). For the patients with aldosteronoma, improvements in hypertension management were noted. The mean blood pressure before ablation was 149/90 mm Hg with a mean (±standard deviation) of 3.1 ± 0.6 blood pressure medications, and this decreased to 122/77 mm Hg at a mean of 2.8 months after ablation with 1.3 ± 0.9 medications (P < .001) and 124/75 mm Hg at a mean of 41.4 months. There were two minor complications: one small pneumothorax and one limited hemothorax, neither of which required overnight admission. There were two episodes of transient self-remitting procedural hypertension-one in a patient with aldosteronoma and one in the patient with a cortisol-secreting tumor; however, none of these patients required further therapy during overnight observation. CONCLUSION RF ablation may be an effective, minimally invasive method for treating small functional primary adrenal tumors.

Screening Carotid Sonography Before Elective Coronary Artery Bypass Graft Surgery: Who Needs It

OBJECTIVE The purpose of this study was to determine whether selection criteria for performing carotid sonographic screening before elective coronary artery bypass graft surgery can decrease the number of negative examinations without overlooking patients with significant carotid disease. SUBJECTS AND METHODS A history of peripheral vascular disease, a prior cerebrovascular event, smoking, diabetes, hypertension, cervical carotid disease, left main coronary disease, and patient sex were criteria prospectively gathered for 295 consecutive patients undergoing screening carotid sonography before elective coronary artery bypass surgery. Logistic regression modeling was used to determine if any single criterion or combination of criteria could be applied to decrease the number of screening examinations without sacrificing detection of significant (> or = 50% cross-sectional narrowing) carotid stenosis. RESULTS Smoking, diabetes, hypertension, a previous cerebrovascular event, peripheral vascular disease, left main coronary artery disease, and a history of cervical carotid disease were associated with significant carotid disease (chi-square test) in our subject population. Logistic modeling showed that the probability of detecting significant carotid disease increases 2.98 times for each additional selection criterion present. Possessing at least one selection criterion would still yield 100% examination sensitivity while increasing specificity to 30.0%. CONCLUSION Selection criteria should be applied when choosing patients for carotid sonographic screening before elective coronary artery bypass surgery. This approach would decrease the number of noncontributory examinations but would have little effect on the detection of significant carotid stenosis in this target population.

Feasibility of Measurement of Pancreatic Perfusion Parameters with Single-Compartment Kinetic Model Applied to Dynamic Contrast-enhanced CT Images

PURPOSE To examine the feasibility of measuring pancreatic perfusion parameters by using a single-compartment kinetic model applied to contrast material-enhanced computed tomographic (CT) images. MATERIALS AND METHODS This study received institutional review board approval and was HIPAA compliant. Informed consent was waived. Eight subjects (four men, four women; median age, 40 years; range, 35-57 years), all potential renal donors with no pancreatic pathologic abnormalities, underwent abdominal CT imaging, which resulted in 30 10-mm-thick sections obtained at a single level. Imaging was a direct result of bolus timing employed for standard renal donor protocol; no additional imaging beyond what was clinically warranted was performed. Images were obtained every 3 seconds; scanning was initiated at the onset of contrast material administration. Region-of-interest measurements were obtained for the pancreatic body and the aorta to generate time-enhancement curves (TECs). A one-compartment model was applied by using the aortic and pancreatic TECs as the input and output functions, respectively. Pancreatic volumetric blood flow F(V), volume of distribution V(D), and blood transit time tau were determined. Modeled pancreatic TECs were generated and were compared with actual TECs for wellness of fit. RESULTS Pancreatic F(V) values from the single-compartment model ranged from 0.961 to 6.405 min(-1) (mean, 3.560 min(-1) +/- 1.900 [standard deviation]). Volume of distribution V(D) ranged from 1.491 to 3.080 (mean, 2.383 +/- 0.638), while values of tau ranged from -3.090 to 6.436 seconds (mean, 0.481 second +/- 3.000). Modeled pancreatic TECs closely matched true pancreatic TECs for each subject, with R(2) values ranging from 0.840 to 0.959. CONCLUSION A simple one-compartment kinetic model can be applied to contrast-enhanced images of normal pancreas to yield accurate pancreatic TECs, which attest to the perfusion parameters obtained. In addition to yielding volumetric blood flow similar to that of other models of tissue perfusion, two additional pancreatic perfusion parameters can be obtained. SUPPLEMENTAL MATERIAL http://radiology.rsnajnls.org/cgi/content/full/2492080026/DC1.

Quality Initiatives: Strategies for Anticipating and Reducing Complications and Treatment Failures in Hepatic Radiofrequency Ablation

Radiofrequency (RF) ablation is one of several local treatment strategies that can be used for the destruction of a variety of primary and secondary liver tumors. As experience with RF ablation grows, it becomes increasingly evident that successful ablation requires meticulous technique. In addition, knowledge of potential complications is critical for both the interventionalist and the radiologist, whose postablation interpretation can facilitate identification of complications and treatment failures. Hepatic RF ablation offers significant advantages in that it is less invasive than surgery and carries a low risk of major complications. Successful prevention of complications and treatment failures begins at initial consultation and continues with preablation evaluation of specific patient factors such as coagulation profiles, use of medications, and risk factors for infection. Other predisposing factors include background liver cirrhosis, prior hepatectomy, and portal hypertension. During ablation, careful attention must be given to tumor size, number, and location. For large or multiple ablations, separate ablation sessions can help reduce the prevalence of postablation syndrome, and clustered electrodes and multiple overlapping treatment zones may be used to reduce the risk of treatment failure. It is critical to reevaluate tumors during ablation to determine the best approach and to compensate for changes in size and relative location due to patient positioning. With use of these strategies, hepatic RF ablation can be performed with greater safety, better patient tolerance, and a reduced risk of complications and treatment failures.

Can Doppler Sonography Discern Between Hemodynamically Significant and Insignificant Portal Vein Stenosis After Adult Liver Transplantation

OBJECTIVE The purpose of our study was to determine whether Doppler sonography, using a strict reference standard, can specifically identify hemodynamically significant portal vein anastomotic stenosis after liver transplantation in adults. MATERIALS AND METHODS The duplex and color Doppler examinations of 13 consecutive adult patients who underwent portal venography for suspected portal vein stenosis after liver transplantation were retrospectively examined. Peak systolic velocity (PSV) and change in PSV (ΔPSV) along the portal vein were correlated with portal venography. Stenoses above 50% on the basis of strict venographic criteria were considered hemodynamically significant. The Doppler studies before and after intervention were also assessed. Fourteen randomly chosen subjects with transplants without suspicion of portal anastomotic stenosis acted as controls. RESULTS Six patients had significant portal vein stenosis (> 50%) and seven had stenosis below 50%. PSV and ΔPSV were significantly greater for patients with > 50% stenosis in comparison with those with ≤ 50% stenosis and control subjects. Optimal threshold values for PSV and ΔPSV were 80 and 60 cm/s, respectively, with either value alone yielding sensitivity of 100% and specificity of 84% for significant stenosis. Threshold values also included cases of stenosis below 50%. Five of six patients with > 50% stenosis underwent stenting, with poststent PSV and ΔPSV significantly declining to match that of control subjects. Three of seven with stenosis below 50% had stents placed but no significant change in the Doppler examination. CONCLUSION Doppler threshold criteria reliably exclude those without posttransplantation portal vein stenosis and have high sensitivity for detecting portal stenosis. However, these criteria cannot discern the extent of stenosis.

Percutaneous treatment of a gastrocutaneous fistula after gastrostomy tube removal.

Gastrocutaneous fistula formation is a potential complication resulting from nonsurgical gastrostomy or gastrojejunostomy tube removal. Limited success in conservative treatment has been achieved with either mechanical obstruction of the tract or pharmacologically based increase in gastric pH and improvement of gastric emptying. A case of successful conservative percutaneous treatment of a gastrocutaneous fistula with use of the sequence of initial tract de-epithelialization followed by direct tract sclerosis and mechanical obstruction is presented in this article.

Percutaneous treatment of a pancreatic fistula after pancreaticoduodenectomy.

Breakdown of the pancreaticojejunal anastomosis after a Whipple procedure is reported to occur in as many as 15% of cases. Intraoperative placement of a drain adjacent to the anastomosis is performed to allow the creation of a controlled pancreaticocutaneous fistula in the event of an anastomotic disruption. The authors present a case of successful percutaneous treatment of a disrupted pancreaticojejunal anastomosis. This was achieved with use of the resulting pancreaticocutaneous fistula for access to restore internal drainage, followed by fistula occlusion with use of gelatin pledgets.