Effects of Arsenic Trioxide on Radiofrequency Ablation of VX2 Liver Tumor: Intraarterial versus Intravenous Administration

OBJECTIVE: Arsenic trioxide (As2O3) can be used as a possible pharmaceutical alternative that augments radiofrequency (RF) ablation by reducing tumor blood flow. The aim of this study was to assess the effect of intraarterial and intravenous administration of As2O3 on RF-induced ablation in an experimentally induced liver tumor. MATERIALS AND METHODS: VX2 carcinoma was grown in the livers of 30 rabbits. As2O3 (1 mg/kg) was administered through the hepatic artery (n = 10, group A) or ear vein (n = 10, group B), 30 minutes before RF ablation (125 mA +/- 35; 90 +/- 5degrees C). As a control group, 10 rabbits were treated with RF ablation alone (group C). RF was intentionally applied to the peripheral margin of the tumor so that ablation can cover the tumor and adjacent hepatic parenchyma. Ablation areas of the tumor and adjacent parenchymal changes among three groups were compared by the Kruskal-Wallis and Mann-Whitney U test. RESULTS: The overall ablation areas were 156 +/- 28.9 mm2 (group A), 119 +/- 31.7 (group B), and 92 +/- 17.4 (group C, p < 0.04). The ablation area of the tumor was significantly larger in group A (73 +/- 19.7 mm2) than both group B (50 +/- 19.4, p = 0.02) and group C (28 +/- 2.2, p < 0.01). The ratios of the tumoral ablation area to the overall ablation area were larger in group A (47 +/- 10.5%) than that of the other groups (42 +/- 7.3% in group B and 32 +/- 5.6% in group C) (p < 0.03). CONCLUSION: Radiofrequency-induced ablation area can be increased with intraarterial or intravenous administration of As2O3. The intraarterial administration of As2O3 seems to be helpful for the selective ablation of the tumor.

Efficacy and Safety of Hepatic Arterial Infusion of Fluorouracil with Leucovorin as Salvage Treatment for Refractory Liver Metastases from Colorectal Cancer

BACKGROUND/AIMS: Limited options remain for patients with metastatic colorectal cancer (CRC) after failure of standard systemic chemotherapy. Readministration of chemotherapeutic agents by hepatic arterial infusion (HAI) has the rationale of providing higher concentrations of chemotherapeutic agents to hepatic metastases. The present study was conducted to evaluate the efficacy and safety of HAI of fluorouracil with leucovorin (HAI 5-FU/LV) for patients with liver metastases from CRC. METHODS: Fourteen patients with liver metastases from CRC who received HAI 5-FU/LV after failure of systemic chemotherapy containing fluorouracil and leucovorin were identified and their medical records were reviewed. RESULTS: Of 10 patients evaluable for response, one partial response, six stable disease, and three progressive disease were reported. Additionally, the overall response and disease control rates were 7% and 50%, respectively. The median time to progression was 4.3 months (range, 2.9 to 5.6), to hepatic progression was 5.8 months (range, 4.7 to 6.9), and to extrahepatic progression was 5.8 months (range, 2.3 to 9.2). No grade 3/4 hematologic toxicities occurred and one case of abdominal pain and two cases of oral mucositis were the only grade 3 nonhematologic toxicities. Catheter-related complications occurred in three patients: one thrombosis, one infection, and one displacement. CONCLUSIONS: HAI 5-FU/LV was well tolerated and showed modest efficacy for patients with liver metastases from refractory CRC. Readministration of previously used chemotherapeutic agents via the hepatic artery could be an effective salvage option and warrants further investigation in a prospective trial.

Gastrointestinal Stent Update

The use of self-expanding metallic stents in the upper gastrointestinal tract, placed under radiologic imaging or endoscopic guidance, is the current treatment of choice for the palliation of malignant gastrointestinal outlet obstructions. Advances in metallic stent design and delivery systems have progressed to the stage where this treatment is now considered a minimally invasive therapy. Metallic stent placement will broaden further into the field of nonsurgical therapy for the gastrointestinal tract. To date, metallic stents placed in the esophagus, gastric outlet, colorectum, and bile ducts are not intended to be curative, but rather to provide a palliative treatment for obstructions. The evolution of metallic stent technology will render such procedures not only palliative but also therapeutic, by enabling local drug delivery, and the use of biodegradable materials will reduce procedure-related complications.

Congenital Angiodysplasia in a Woman Presenting with Idiopathic Jejunal Varicosis on Angiography

Angiography is a useful diagnostic tool in cases with massive gastrointestinal bleeding such as angiodysplasia and varicosis when endoscopy is not available. Angiodysplasia and varicosis have distinguishable characteristic features on angiography, such as the presence of a nidus, visible late-draining veins, and the typical vascular tuft. We recently treated a rare case of congenital angiodysplasia without the characteristic angiodysplasia features on angiography. Instead, the patient presented with a very rare case of idiopathic jejunal varicosis. A 42-year-old woman visited the emergency room with the chief complaint of melena for three days and a hemoglobin level of 5.9 g/dL. An abdominal CT angiogram showed varicosis at the jejunal mesentery. Angiography of the superior and inferior mesenteric arteries showed tortuous and dilated jejunal and ileal branches during the venous phase, suggesting a vascular malformation such as varicosis of the jejunum. Surgical exploration with intraoperative endoscopy revealed diffuse engorged veins and a 1.0-cm-diameter superficial ulcer covered with a blood clot that was 70 cm from the ligament of Treitz. A 100-cm segment of jejunum was resected. Histological examination revealed that the lesion was angiodysplasia, not varicosis. The final diagnosis was congenital angiodysplasia.

Renal Hypoperfusion Associated with Splenorenal Shunts in Liver Cirrhosis

PURPOSE: To determine whether spontaneous a splenorenal shunt can be used as an imaging predictor of early renal hemodynamic changes in patients with cirrhosis. MATERIALS AND METHODS: The study included 82 cirrhotic patients and 41 control subjects. Three-phase CT was performed and CT attenuation values (Hounsfield units) of the renal cortex in three phases were measured to evaluate renal perfusion. Likelihood ratio tests for trend were conducted for age, presence of ascites, and Child's grade. RESULTS: The mean CT attenuation values of the renal cortex in cirrhotic patients were significantly lower than the values of control subjects in three phases: 153.3 +/- 37.9 versus 173.3 +/-25.2 in the arterial phase, 172.6 +/- 41.0 versus 197.6 +/- 26.5 in the portal phase and 136.9 +/- 26.0 versus 152.7 +/- 20.0 in the delayed phase, respectively. The mean CT attenuation value of cortices in patients with renal hypoperfusion was 119.9 +/- 11.8 in the portal phase. Child's class C (aOR: 58.4, 95% CI: 3.6-956.2; p < 0.01) and the presence of a renal shunt (aOR: 7.5, 95% CI: 1.8-30.5; p < 0.01) were associated with renal hypoperfusion. The incidence of renal hypoperfusion was associated with Child's grade (trend: p < 0.01), and not with the grade of ascites or age. CONCLUSION: A dilated spontaneous splenorenal shunt may be a risk factor for renal hypoperfusion in cirrhosis.

Percutaneous Endovascular Stent-graft Treatment for Aortic Disease in High Risk Patients: The Early and Mid-term Results / 대한흉부외과학회지

BACKGROUND: Aortic surgery for high risk patients has high mortality and morbidity rates, and the necessity of performing aortic surgery in cancer patients is questionable because of their short life expectancy. Endovascular repair of aneurysm repair can be considered for high risk patients and cancer patients because it has relatively lower invasiveness and shorter recovery times than aortic surgery does. Especially, percutaneous endovascular stent graft treatment is more useful for high risk patients because it does not require general anesthesia. MATERIAL AND METHOD: From July 2003 to September 2007, twelve patients who had inoperable malignancy or who had a high risk of complication because of their combined diseases during aortic surgery underwent endovascular aortic aneurysm repair. The indications for endovascular repair were abdominal aortic aneurysm in 5 patients, descending thoracic aortic aneurysm in 6 patients and acute type B aortic dissection in one patient. The underlying combined disease of these patients were malignancy in 3 patients, respiratory disease in 6 patients, old age with neurologic disease in 6 patients, Behcet's diseae in one patient and chronic renal failure in one patient. RESULT: Stent grafts were inserted percutaneously in all cases. There were 4 hospital deaths and there were 3 delayed deaths during the follow-up periods. There were no deaths from aortic disease, except one hospital death. There were several complications: a mild cerebrovascular accident occurred in one patient, acute renal failure occurred in 2 patients and ischemic bowel necrosis occurred in one patient. Mild type I endoleak was observed in 2 patients and type II endoleak was observed in a patient after stent graft implantation. Newly developed type I endoleak was observed in a patient during the follow-up period. CONCLUSION: Percutaneous endovascular stent graft insertion is relatively safe procedure for high risk patients and cancer patients. Yet it seems that its indications and its long term results need to be further researched.

A New and Simple Practical Plane Dividing Hepatic Segment 2 and 3 of the Liver: Evaluation of Its Validity

OBJECTIVE: The conventional method of dividing hepatic segment 2 (S2) and 3 (S3) is subjective and CT interpretation is unclear. The purpose of our study was to test the validity of our hypothesis that the actual plane dividing S2 and S3 is a vertical plane of equal distance from the S2 and S3 portal veins in clinical situations. MATERIALS AND METHODS: We prospectively performed thin-section iodized-oil CT immediately after segmental chemoembolization of S2 or S3 in 27 consecutive patients and measured the angle of intersegmental plane on sagittal multiplanar reformation (MPR) images to verify its vertical nature. Our hypothetical plane dividing S2 and S3 is vertical and equidistant from the S2 and S3 portal veins (vertical method). To clinically validate this, we retrospectively collected 102 patients with small solitary hepatocellular carcinomas (HCC) on S2 or S3 the segmental location of which was confirmed angiographically. Two reviewers predicted the segmental location of each tumor at CT using the vertical method independently in blind trials. The agreement between CT interpretation and angiographic results was analyzed with Kappa values. We also compared the vertical method with the horizontal one. RESULTS: In MPR images, the average angle of the intersegmental plane was slanted 15 degrees anteriorly from the vertical plane. In predicting the segmental location of small HCC with the vertical method, the Kappa value between CT interpretation and angiographic result was 0.838 for reviewer 1 and 0.756 for reviewer 2. Inter-observer agreement was 0.918. The vertical method was superior to the horizontal method for localization of HCC in the left lobe (p < 0.0001 for reviewers 1 and 2). CONCLUSION: The proposed vertical plane equidistant from S2 and S3 portal vein is simple to use and useful for dividing S2 and S3 of the liver.

Ambulatory Phlebectomy at Radiologic Outpatient Clinic

PURPOSE: To evaluate safety, efficacy, and patient's satisfaction of an ambulatory phlebectomy, performed at a radiology outpatient clinic. MATERIALS AND METHODS: Between 2003 and 2006, an ambulatory phlebectomy was performed in 12 patients. Endovenous radiofrequency ablation was performed through a venotomy. The venotomy was ligated after RF ablation, and the ambulatory phlebectomy was performed. The patients visited the radiology outpatient clinic one day, one week, and 2 months after the procedure. The improvement in the clinical symptoms, cosmetic change in varicosity, and the procedure related complications were evaluated. The patient's satisfaction was evaluated using a 5-grade scale. RESULTS: RF ablation through a venotomy was performed successfully in all 12 patients. On average, 4.5 incisions were made, and 12.5 cm of varicosity had been removed. The mean procedure time was one hour and forty minutes. The complications of the ambulatory phlebectomy were bruising in one patient, and skin pigmentation in another. The complications associated with RF ablation were a hard palpable vein in 7 patients, numbness in 7 patients, and skin pigmentation along the vein in 2 patients. Follow-up duplex sonography was performed at 2 months after the procedure, showed complete occlusion in all 12 patients. The clinical symptoms had improved in 11 patients, and the varicosity disappeared cosmetically in 11 patients. CONCLUSION: An ambulatory phlebectomy, combined with RF ablation of the greater saphenous vein, can be performed safely and effectively at a radiology outpatient clinic.

Evaluation of the Release Behavior of the Dexamethasone Embedded in Polycarbonate Polyurethane Membranes: An In Vitro Study

PURPOSE: To evaluate the release behavior of dexamethasone embedded in a polycarbonate polyurethane membrane. MATERIALS AND METHODS: Both water-soluble and water-insoluble dexamethasone were tested, and the release behavior of five water-insoluble dexamethasone films of different thickness (78 to 211 micrometer) was also evaluated. The amount of Dexamethasone used was 10% of the total weight of the polyurethane film mass. Each film was placed in a centrifuge tube containing 25 ml of 0.1-M neutral phosphate buffer, and the tubes were placed in a shaking incubator to quantify the amount of drug released into the buffer, absorption spectroscopy (lambda max=242 nm) was employed. RESULTS: In the test involving water-soluble dexamethasone, 60% of the drug was released during the first two hours of the study. Films containing water-insoluble Dexamethasone, on the other hand, released 40%, 60% and 75% of the dexamethasone in one, three and seven days, respectively. Both types of film maintained low-dose drug release for 28 days. When release behavior was compared between water-insoluble films of different thickness, thicker film showed less initial burst and more sustained release. CONCLUSION: Dexamethasone release behavior varies according to drug solubility and membrane thickness, and may thus be conrolled.

Percutaneous Endovascular Stent-Graft Treatment of Aortic Aneurysms and Dissections: New Techniques and Initial Experience

PURPOSE: To evaluate the feasibility, safety and effectiveness of a newly designed percutaneously implanted separate stent-graft (SSG) for the treatment of aortic aneurysms and dissections. MATERIALS AND METHODS: Using a percutaneous technique, SSG placement (in the descending thoracic aorta in 26 cases and infrarenal abdominal aorta in 24) was attempted in 50 patients with aortic aneurysms (n=27) or dissection (n=23). All SSGs were individually constructed using self-expandable nitinol stents and a Dacron graft, and were introduced through a 12 F sheath and expanded to a diameter of 20-34 mm. In all cases, vascular access was through the femoral artery. The clinical status of each patient was monitored, and postoperative CT was performed within one week of the procedure and at 3-6 month intervals afterwards. RESULTS: Endovascular stent-graft deployment was technically successful in 49 of 50 patients (98%). The one failure was due to torsion of the unsupported graft during deployment. Successful exclusion of aneurysms and the primary entry tears of dissections was achieved in all but three patients with aortic dissection. All patients in whom technical success was achieved showed complete thrombosis of the thoracic false lumen or aneurysmal sac, and the overall technical success rate was 92%. In addition, sixteen patients demonstrated complete resolution of the dissected thoracic false lumen (n=9) or aneurysmal sac (n=7). Immediate post-operative complications occurred at the femoral puncture site in one patient with an arteriovenous fistula, and in two, a new saccular aneurysm developed at the distal margin of the stent. No patient died, and there was no instance of paraplegia, stroke, side-branch occlusion or infection during the subsequent mean follow-up period of 9.4 (range, 2 to 26) months. CONCLUSION: In patients with aortic aneurysm and dissection, treatment with a separate percutaneously inserted stent-graft is technically feasible, safe, and effective.

Radiofrequency Ablation of the Gastrointestinal Tract with a Stent-Like Electrode: Experimental Study

OBJECTIVE: To assess the technical feasibility of a newly designed stent-like electrode in rabbits. MATERIALS AND METHODS: A stent-like electrode was knitted from a single thread of nitinol wire and interconnected to a generator using similar wire. In order to gauge the extent of radiofrequency ablation (RFA), we measured the depth of the ablated area in cow liver using a combination of 180-sec time intervals and 20-watt power increments. For data processing, Cox regression analysis was used. RFA was also applied to the small intestine of rabbits using this stent-like electrode under six different sets of conditions: 10 watts for 1 min, 10 watts for 2 mins, 20 watts for 1 min, 20 watts for 2 mins, 30 watts for 1 min, and 30 watts for 2 mins. To determine the gross and microscopic findings, six animals were sacrificed immediately after the procedure and the results obtained under the different sets of conditions were correlated. Eight rabbits were monitored for 4 weeks prior to sacrifice. RESULTS: For both ex-vivo and in-vivo ablations, the depth of the thermal lesion showed linear correlation with both the duration of RFA and the power applied. RFA of the duodenum was technically successful in all 14 rabbits. The acute changes occurring in the rabbits' small intestine included color change, cytoplasmic denaturation, fibrin deposition and hemorrhage, among which hemorrhage of the mucosal layer was the earliest finding. RF ablation for 2 mins at 30 watts caused serosal hemorrhage. The gross and histologic changes occurring showed close correlation under all six sets of conditions. CONCLUSION: Use of the stent-like electrode proves technically feasible but to determine the nature of the chronic change occurring in the gastrointestinal tract after RF ablation, further investigation and long-term follow-up in animals are required.

Evaluation of the Pedal Artery: Comparison of Three-dimensional Gadolinium-Enhanced MR Angiography with Digital Subtraction Angiography

PURPOSE: To compare the three-dimensional gadolinium-enhanced MR angiography with digital subtraction angiography (DSA) for evaluation of the pedal artery. MATERIALS AND METHODS: In 12 extremities of 11 patients, both digital subtraction angiography (DSA) and contrast-enhanced MR angiography (CE-MR angiography) were performed during the same week. Among ten of the 11 patients, the following conditions were present: atherosclerosis (n=4), diabetic foot (n=3), Buerger's disease (n=1), calciphylactic arteriopathy (n=1) and arteriovenous malformation of the foot (n=1). The remaining patient underwent angiography prior to flap surgery. For MR angiography, a 1.5T system using an extremity or head coil was used. A three-dimensional FISP (fast imaging with steady state precession) sequence was obtained before enhancement, followed by four sequential acquisitions (scan time, 20 secs; scan interval time, 10 secs) 10 seconds after intravenous bolus injection of normal saline (total 10 cc), following intravenous adminstration of gadolinium (0.02 mmol/kg, 3 ml/sec). Arterial segments of the ankle and foot were classified as the anterior or posterior tibial artery, the distal peroneal artery, the medial or lateral plantar artery, the pedal arch, and the dorsalis pedis artery. Two radiologists independently analysed visualization of each arteraial segment and the mean of visible arterial segments in one extreminty using CE-MR angiography and DSA. RESULTS: Among 84 arterial segments, 16 were invisible at both CE-MR angiography and DSA, while 39 were demonstrated by both modalities. Twenty-six segments were visible only at CE-MR angiography and three only at DSA. CE-MR angiography displayed a higher number of arterial segments than DSA (mean, 5.42 vs. mean 3.50, respectively), a difference which was statistically significant (p<0.000). The difference between each arterial segment was not statistically significant, except for the dorsalis pedis artery (t test, p<0.000). CONCLUSION: In that it provides additional information for the planning of treatment of lower-extremity arterial disease, three-dimensional CE-MR angiography is superior to DSA for evaluation of the pedal artery.

The Efficacy of Metallic Stent Placement in the Treatment of Colorectal Obstruction

DBJECTIVE: To evaluate the efficacy of newly designed covered and non-covered coated colorectal stents for colonic decompression. MATERIALS AND METHODS: Twenty-six patients, (15 palliative cases and 11 preoperative) underwent treatment for the relief of colorectal obstruction using metallic stents positioned under fluoroscopic guidance. In 24 of the 26, primary colorectal carcinoma was diagnosed, and in the remaining two, recurrent colorectal carcinoma. Twenty-one patients were randomly selected to receive either a type A or type B stent; for the remaining five, type C was used. Type A, an uncovered nitinol wire stent, was lightly coated to ensure structural integrity. Type B (flare type) and C (shoulder type) stents were polyurethane covered and their diameter was 24 and 26mm, respectively. The rates of technical success, clinical success, and complications were analyzed using the chi-square test, and to analyse the mean period of patency, the Kaplan-Meier method was used. RESULTS: Thirty of 31 attempted placements in 26 patients were successful, with a technical success rate of 96.8% (30/31) and a clinical success rate of 80.0% (24/30). After clinically successful stent placement, bowel decompression occurred within 1-4 (mean, 1.58+/-0.9) days. Five of six clinical failures involved stent migration and one stent did not expand after successful placement. In the preoperative group, 11 stents, one of which migrated, were placed in ten patients, in all of whom bowel preparation was successful. In the palliative group, 19 stents were placed in 15 patients. The mean period of patency was 96.25+/-105.12 days: 146.25+/-112.93 for type-A, 78.82+/-112.26 for type-B, and 94.25+/-84.21 for type-C. Complications associated with this procedure were migration (n=6, 20%), pain (n=4, 13.3%), minor bleeding (n=5, 16.7%), incomplete expansion (n=1, 3.3%), and tumor ingrowth (n=1, 3.3%). The migration rate was significantly higher in the type-B group than in other groups (p=0.038). CONCLUSION: Newly designed covered and non-covered metallic stents of a larger diameter are effective for the treatment of colorectal obstruction. The migration rate of covered stents with flaring is higher than that of other types. For evaluation of the ideal stent configuration for the relief of colorectal obstruction, a clinical study involving a larger patient group is warranted.

Radiofrequency Ablation of Lung Cancer: Preliminary Report

PURPOSE: Radiofrequency ablation (RFA) of lung cancer in animals and humans has been described in previously published reports. The aim of this study was to present our preliminary experience of treatment of lung cancer involving this approach. MATERIALS AND METHODS: Eight patients with lung malignancies [stage IIIB or IV bronchogenic adenocarcinoma (n=6), metastatic squamous cell carcinoma (n=1), metastatic hepatocellular carcinoma (n=1)] underwent RFA treatment. In all cases LeVeen-type electrodes were employed and CT was used to monitor the procedure. One-day and one-month follow-up CT scans were obtained and analyzed. RESULTS: Prior to treatment, tumor diameter ranged from 2.5 to 5 cm; afterwards, low attenuation consistent with coagulative necrosis was observed. Complications included a small amount of pneumothorax (n=4), pleural effusion (n=8), and subcutaneous emphysema (n=1). Tumor size decreased in five patients, was unchanged in two, and increased in one. CONCLUSION: Radiofrequency ablation of lung cancer is safe and may result in a reduced tumor burden.

The Usefulness of Three-Dimensional Gadolinium-Enhanced MR Venography for the Evaluation of Varices in Lower Extremities

PURPOSE: To assess the performance of contrast-enhanced three-dimensional(3-D) magnetic resonance venography (MRV) of the pelvis and lower extremities in patients with varicose veins. MATERIALS AND METHODS: Ascending and MR venography were performed in seven legs of seven patients, and duplex Doppler sonography and MR venography in 15 legs of 12 patients, all referred for evaluation of varicose veins. For analysis, the venous system as revealed by ascending and MR venographic images was divided into 13 segments. For detection of reflux to the great saphenous vein, duplex Doppler sonography and MRV were performed. RESULTS: In ascending venography and MRV, 91 venous segments were potentially visible; both modalities depicted 78 of these, but failed to detect four. Ascending venography and MRV detected 17 and 19 varices, respectively. When two tourniquets were placed around the ankle and knee using the Valsalva maneuver, MRV and duplex Doppler sonography detected reflux in 8 of 11 and 13 of 15 legs, respectively. CONCLUSION: Contrast-enhanced 3-D MRV comprehensively displays the venous system of the lower extremities and permits assessment of varicose veins. MRV using the Valsalva maneuver allows assessment of reflux to the great saphenous vein.

Benign and Malignant Tracheobronchial Strictures:Long Term Follow-up of Treatment with Polyurethane-Covered Retrievable Expandable Nitinol Stents strictures

PURPOSE: To assess the safety and long term effectiveness of polyurethane-covered retrievable expandable nitinol stents in the treatment of benign and malignant tracheobronchial strictures. MATERIALS AND METHODS: Under fluoroscopic guidance, the stents were placed in 32 patients with dyspnea whose strictures were malignant in 15 cases and benign in 17. A stent was removed when complications occurred,or -electively- 2-6 months after placement in patients with benign strictures. The range of follow-up period was 1 -98 weeks (median, 47; range, 50) weeks. RESULTS: Stent placement was well tolerated in 30 patients. After placement, all 32 showed immediate symptom improvement and in none were complications such as ingrowth of a tumor or granulation tissue observed during the follow up period. Stent migration occurred in six patients. In one of six and four of five patients from whom, respectively, stents had been electively removed two and six months after placement, tracheo-bronchial restenosis did not occur during follow up. Second stents were placed in six patients in whom dyspnea recurred due to restenosis after elective stent removal. In two of these six, stents were removed six months after placement and dyspnea did not recur during follow up. CONCLUSION: The use of covered retrievable tracheobronchial stents is safe and feasible in the conservative treatment of patients with malignant tracheobronchial strictures as well as for selected patients with benign strictures.

Influence of Dexamethasone: Coated Nitinol Stent on Neointimal Formation in the Canine Great Vessel Model

PURPOSE: To evaluate the effect of dexamethasone(DM) and polyurethane(PU)-coated nitinol stent on neointimal formation in the canine great vessels. MATERIALS AND METHODS: Thirty-six nitinol wire stents were implanted in the abdominal aorta and inferior vena cava(IVC) of six dogs. In each animal, six different types of stent (NC, non-coated; PU, polyurethane coated; DM, DM and polyurethane coated) were serially positioned in permutationally possible order in the aorta below the renal arteries and in the IVC below the renal veins. For DM stent an in-vitro drug release test was performed to determine the stability of DM release. The thickness of the intima and media of the aorta and of the intima of the IVC were measured three (n=3) or six months (n=3) after stent placement at and between the wires. RESULTS: In the in-vitro study, 25% of DM was released during the first week, and the subsequent release rate was 3 microgram/day for 6 months. The intima-to-media ratio of DM-stented aorta was less than in aortas where PU or NC stents were used (p0.05). CONCLUSION: In this canine great vessel model, newly designed DM-coated nitinol stent decreased neointimal formation.

Intraluminal Brachytherapy after Metallic Stent Placement in Primary Bile Duct Carcinoma

PURPOSE: To determine the effect of intraluminal brachytherapy on stent patency and survival after metallic stent placement in patients with primary bile duct carcinoma. MATERIALS AND METHODS: Twenty-seven patients with primary bile duct carcinoma underwent metallic stent placement; in 16 of the 27 intraluminal brachytherapy with an iridium-192 source (dose, 25 Gy) was the performed. Obstruction was due to either hilar (n=14) or non-hilar involvement (n=13). For statistical comparison of patients who underwent/did not undergo intraluminal brachytherapy, stent patency and survival were calculated using the Kaplan-Meier method and an independent t test. RESULTS: The mean durations of stent patency and survival were 9.1 and 10.0 months respectively in patients who underwent intraluminal brachytherapy, and 4.2 and 5.0 months in those who did not undergo this procedure (p<0.05). The mean durations of stent patency and survival among the 22 patients who died were 7.6 (range, 0.8 -16.1) and 8.3 (range, 0.8-17.3) months, respectively, in the eleven patients who underwent intraluminal brachytherapy, and 4.2 (range, 0.9-8.0) and 5.0 (range, 0.9-8.4) months in those whom the procedure was not performed (p<0.05). CONCLUSION: Intraluminal brachytherapy after stent placement extended both stent patency and survival in patients with primary bile duct carcinoma.

Evaluation of the Biodurability of Polyurethane-Covered Stent Using a Flow Phantom

OBJECTIVE:To evaluate the biodurability of the covering material in retrievable metallic stents covered with polycarbonate polyurethane. MATERIALS AND METHODS: Using a peristaltic pump at a constant rate of 1ml/min, bile was recirculated from a reservoir through a long tube containing four stents. Each of these was removed from the system every two weeks and a radial tensile strength test and scanning electron microscopy (SEM) were performed. Each stent, removed at 2, 4, 6 and 8 weeks, was compared with a control stent not exposed to bile juice. RESULTS: Gross examination showed that stents were intact at 2 weeks, but at 4, 6 and 8 weeks cracks were observed. The size of these increased gradually in accordance with the duration of exposure, and at 8 weeks several large holes in the polyurethane membrane were evident. With regard to radial tensile strength, extension and peak load at break were 84.47% and 10.030 N/mm, 54.90% and 6.769 N/mm, 16.55% and 2.452 N/mm, 11.21% and 1.373 N/mm at 0, 2, 4 and 6 weeks, respectively. Scanning electron microscopy at 2 weeks revealed intermittent pitting and cracking, and examination at 4, 6 and 8 weeks showed that the size of these defects was gradually increasing. CONCLUSION: When the polyurethane membrane was exposed to bile, biodegradation was first observed at week two and increased gradually according to the duration of exposure.

The Efficacy of Intraluminal Radiotherapy after Metallie Stent Insertion in Malignant Biliary Tract Obstruction / 대한소화기내시경학회지

BACKGROUND/AIMS: Inoperable malignant biliary tract obstructions (MBTO) are best palliated by drainage procedures followed by radiation therapy. In order to administer high doses in a short time to the central part of the tumor, internal radiotherapy has been proposed for a palliative goa1. The aim of this study is to investigate the effect of intraluminal radiotherapy (ILRT) to the stent patency and patients survival time after expandable metallic stent insertion in MBTO. METHODS: Between August 1996 and July 1998, 28 patients (17 females, 11 males, average age 61.4 years) with inoperable MBTO were provided with percutaneous transhepatic biliary drainage (12 patients; bile duct cancer, 8 patients; pancreatic head cancer, 4 patients; gallbladder cancer; 4 patients; lymph node metastasis from stomach cancer). The 14 patients were treated by only metallic stent. The other 14 patients were treated by metallic stent insertion and followed by ILRT. The ILRT was done by iridium-192 (mean dosage 23.3 Gray, 5 fractions). RESULTS: There were no significant differences in the two groups regarding age, sex, type of disease, and location of the obstruction. The patients tolerated ILRT well. CONCLUSIONS: The ILRT after expandable metallic stent was safe and effective in stent patency and the patient's surviva1 time in inopcrable MBTO.