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Andrew S Wright

Publications and source records attributed to Andrew S Wright.

11 recordsLinked to original sources
PubMed2005

Radiofrequency versus microwave ablation in a hepatic porcine model.

PURPOSE: To compare microwave (MW) and radiofrequency (RF) ablation in a hepatic porcine model. MATERIALS AND METHODS: Institutional animal research committee approval was obtained. Nineteen pigs were divided into groups based on time of sacrifice (group A, immediate; group B, 2 days; group C, 28 days; group D, 28 days). Groups A, B, and C each underwent a combination of RF and MW ablation. Group D underwent either four MW or four RF ablations. Ablation was performed with a prototype MW device (915 Mhz, 40 W, 10 minutes) and a commercial RF system (150 W, 10 minutes, 3-cm deployment). Computed tomography (CT) was performed in groups B and C at 2 days and in group C at 28 days. Group D underwent serial laboratory testing. Specimens were serially sectioned, and short-axis diameter and length of each were measured. The percentage deflection caused by local blood vessels (heat-sink effect) was also measured in group A. Likelihood ratio tests and unpaired t tests were used for statistical analyses as appropriate. RESULTS: MW ablation zones were longer at days 0, 2, and 28 (P < .05), but short-axis diameter was not different from that with RF ablation at any time point (P > .05). Local blood vessels caused 3.5% +/- 5.3 (standard deviation) deflection at MW ablation compared with 26.2% +/- 27.9 at RF ablation (P < .05). MW and RF ablation zones were indistinguishable at CT or pathologic evaluation. Laboratory test results were similar between RF ablation-only animals and MW ablation-only animals, with the exception of a slightly higher alkaline phosphatase levels at day 2 in RF ablation-only animals (P < .02). CONCLUSION: MW and RF ablation zones are similar in pathologic appearance and imaging characteristics. Increased length with MW ablation is likely caused by the length of the radiating segment of the antenna. MW ablation may be less affected by the heat-sink effect that is thought to contribute to local recurrence after RF ablation.

Animals↗
PubMed2005

Computer-assisted cognitive therapy for depression: maintaining efficacy while reducing therapist time.

OBJECTIVE: The aim of this investigation was to compare the efficacy of computer-assisted cognitive therapy against standard cognitive therapy and a control group without treatment for outpatients with nonpsychotic major depressive disorder. METHOD: Medication-free participants (N=45) with major depressive disorder were randomly assigned to cognitive therapy (N=15), computer-assisted cognitive therapy (N=15), or a wait list (N=15). Both active treatments consisted of nine sessions over 8 weeks. Therapist time was reduced after the first visit for computer-assisted cognitive therapy, with 25-minute sessions rather than 50-minute sessions. Assessments were completed pretreatment, after 4 and 8 weeks of therapy, and 3 and 6 months posttreatment. RESULTS: Computer-assisted cognitive therapy and standard cognitive therapy were superior to the wait list control group for treatment of depression and did not differ from each other on the primary outcome variables. Very large between-group effect sizes were observed. Improvement in depression for both computer-assisted cognitive therapy and standard cognitive therapy was maintained at the 3- and 6-month follow-up evaluations. Computer-assisted cognitive therapy had more robust effects, relative to being wait-listed, than standard cognitive therapy in reducing measures of cognitive distortion and in improving knowledge about cognitive therapy. CONCLUSIONS: A multimedia, computer-assisted form of cognitive therapy with reduced therapist contact was as efficacious as standard cognitive therapy. Computer-assisted therapy could decrease costs and improve access to cognitive therapy for depression.

Adolescent↗
PubMed2004

Microwave ablation with loop antenna: in vivo porcine liver model.

PURPOSE: To determine the effectiveness of tissue ablation with a loop microwave antenna in various configurations in porcine liver tissue. MATERIALS AND METHODS: Microwave energy was applied for 7 minutes at 60 W in six porcine livers (mean weight, 68.2 kg) by using single (n = 7) or dual 2.7-cm loop microwave probes in parallel (n = 9) or orthogonal (n = 9) configurations. Volume, diameter, shape, and temperature of the zone of necrosis and the presence of viable tissue inside the loop were determined and compared by means of factorial analysis of variance. RESULTS: Mean lesion volume and maximum diameter, respectively, were 32.2 cm(3) +/- 14.4 (SD) and 4.6 cm +/- 1.4 for lesions ablated with parallel probes (parallel lesions), 29.5 cm(3) +/- 8.1 and 4.3 cm +/- 0.6 for lesions ablated with orthogonal probes (orthogonal lesions), and 6.4 cm(3) +/- 1.9 and 3.4 cm +/- 0.62 for lesions ablated with single probes (single lesions) (P <.05, single vs parallel and orthogonal lesions). Mean minimum diameter was greatest for orthogonal lesions (3.5 cm +/- 0.53; P =.017, parallel vs orthogonal lesions). Orthogonal lesions had the highest mean internal temperature (97.2 degrees C) versus parallel (91.9 degrees C) and single (60.0 degrees C) lesions. All orthogonal lesions heated to 60 degrees C in comparison to eight of nine parallel and four of seven single lesions. The mean time to reach 60 degrees C was shortest for orthogonal lesions (93.3 seconds) versus parallel (123.8 seconds) and single (263.0 seconds) lesions. Orthogonal lesions were the most spherical. Viable tissue was present in the center of five of seven single, six of nine parallel, and zero of nine orthogonal lesions. CONCLUSION: Loop microwave antennas allow precise control and effective ablation of targeted tissue, particularly in the orthogonal configuration.

Animals↗
PubMed2003

Bipolar radiofrequency ablation of the kidney: comparison with monopolar radiofrequency ablation.

PURPOSE: We report initial ex vivo and in vivo studies using bipolar radiofrequency (RF) ablation of porcine kidneys. An internal ground electrode is positioned in the kidney opposite the RF electrode, resulting in ablation of all the intervening renal tissue. MATERIALS AND METHODS: Ex vivo preparations of 10 porcine kidneys were perfused continuously with Ringer's solution and treated with either standard external grounded RF (N = 3) or bipolar RF ablation with 1 (N = 2), 2 (N = 3), or 3 (N = 2) cm of separation between the ground probe and the RF probe using a Model 30 RITA generator (RITA, Mountain View, CA). Target temperatures were 90 degrees C for 8 minutes. Gross and histologic assessments were made acutely. Four domestic pigs were treated with monopolar RF ablation of the lower pole of one kidney and bipolar RF with a 12-mm separation between the probes of the contralateral lower pole. Animals were harvested 48 hours later to maximize tissue damage for gross measurements and histologic evaluation. RESULTS: Ex vivo studies revealed grossly monopolar lesions 1.5 cm in maximum diameter and 1.75 cm(3) in volume. In comparison, bipolar lesions were 2.8 cm in maximum diameter and 10.3 cm(3) in volume using 3 cm of electrode separation. There was histologic evidence of cell death in all specimens. In vivo studies showed two distinct gross lesions with RF: one blanched and one hemorrhagic. Using bipolar RF, larger blanched lesions were achievable than with monopolar RF (2.80 cm(3) v 1.63 cm(3)). Overall, the combinations of blanched and hemorrhagic lesions were similar with monopolar and bipolar RF (5.01 v 5.31 cm(3)). Histologic evaluation verified cell death in the blanched lesions and rare areas of normal tissue in the hemorrhagic lesions. CONCLUSIONS: As shown by ex vivo data, bipolar RF can create larger lesions than does monopolar RF. In vivo, at 48 hours, both blanched and hemorrhagic gross lesions were seen using RF. In this model, blanched lesions predominated when performing bipolar RF.

Animals↗
PubMed2003

Multiple probe radiofrequency ablation: pilot study in an animal model.

PURPOSE: Radiofrequency ablation (RFA) is becoming increasingly popular for the minimally invasive treatment of benign and malignant tumors. Currently available systems are limited to the use of a single probe because of electrical interactions between probes. The purpose of this study was to test a new prototype multiple probe generator with a built-in switching mechanism to determine if multiple zones of necrosis could be formed simultaneously without a significant penalty in terms of lesion size and procedure time. MATERIALS AND METHODS: A dual probe generator was created by modifying a commercially available system into an alternating monopolar system with an external electronic switch controlled by a temperature feedback loop. A total of 20 radiofrequency (RF) lesions (conventional single probe, n = 10; switched dual probe, n = 10) were created in the livers of six adult pigs (temperature, 100 degrees C; 10-minute ablation). Lesions were excised and examined for volume, minimum diameter, and maximum diameter. RESULTS: The time to target temperature was slightly greater for dual (3.5 minutes) versus single ablations (2.7 minutes). However, this resulted in only a 48 second (6.5%) longer total ablation time. There was no significant difference between conventional single and dual lesions for lesion volume (13.6 +/- 9.3 cm(3) versus 13.7 +/- 7.0 cm(3); P >.05), minimum diameter (1.63 +/- 0.56 cm(3) versus 1.61 +/- 0.53; P >.05) or maximum diameter (3.3 +/- 0.84 versus 3.4 +/- 0.55, P >.05). CONCLUSION: A multiple probe RFA system that can simultaneously ablate multiple areas in the liver is feasible. If multiple probe units become clinically available, large or irregularly shaped lesions could be treated more effectively than with conventional single probe units, and multiple tumors could be ablated simultaneously, thus potentially decreasing procedure time and anesthetic complications.

Animals↗
PubMed2003

Hepatic radiofrequency ablation with internally cooled probes: effect of coolant temperature on lesion size.

Radiofrequency (RF) ablation is a minimally invasive method for treatment of primary and metastatic liver tumors. One of the currently commercially available devices employs an internally cooled 17-gauge needle probe. Within the probe, cool water is circulated during ablation, which cools tissue close to the probe resulting in larger lesions. We evaluated the effect of different cooling water temperatures on lesion size. We created a finite-element method model, simulated 12 min impedance-controlled ablation and determined temperature distribution for three water temperatures. Lesion diameters in the model were 33.8, 33.4, and 32.8 mm for water temperatures of 5 degrees C, 15 degrees C, and 25 degrees C, respectively. We solved a simplified model geometry analytically and present dependence of lesion diameter on cooling temperature. We further performed ex vivo experiments in fresh bovine liver. We created four lesions for each water temperature, with the same water temperatures as used in the finite-element method (FEM) model. Average lesion diameters were 28.3, 30, and 29.5 mm for water temperatures of 5 degrees C, 15 degrees C, and 25 degrees C, respectively. Water temperature did not have a significant effect on lesion size in the ex vivo experiments (p = 0.76), the FEM model, and the analytical solution.

Animals↗
PubMed2003

Hepatic microwave ablation with multiple antennae results in synergistically larger zones of coagulation necrosis.

BACKGROUND: Microwave ablation is a promising treatment for unresectable liver tumors. Unlike radiofrequency ablation, microwave ablation may be performed with multiple simultaneously active antennae. METHODS: Microwave ablation was performed in an in vivo porcine liver model by using a single antenna (n = 11) or three antennae in a triangular array, activated either sequentially (n = 11) or simultaneously (n = 13). Lesions were measured and assigned a qualitative shape score. RESULTS: Single-antenna microwave lesions had a mean volume of 7.4 +/- 3.9 cm(3), compared with 14.6 +/- 5.2 cm(3) and 43.1 +/- 4.3 cm(3) for sequential and simultaneous multiple-probe ablations, respectively (P <.001; analysis of variance). Simultaneous lesions were rounder than sequential ablations and were more effective near blood vessels. Simultaneous lesions created with probe separation of < or =1.7 cm were round and confluent, whereas clefts were present with distances >1.7 cm (P <.001). CONCLUSIONS: Microwave ablation has several theoretical advantages over currently available radiofrequency devices. Simultaneous three-probe microwave ablation lesions were three times larger than sequential lesions and nearly six times greater in volume than single-probe lesions. Additionally, simultaneous multiple-probe ablation results in qualitatively better lesions, with more uniform coagulation and better performance near blood vessels. Simultaneous multiple-probe ablation may decrease inadequate treatment of large tumors and decrease recurrence rates after tumor ablation.

Animals↗
PubMed2003

Minimally invasive approaches in management of hepatic tumors.

Traditionally, the only curative option for patients with liver tumors has been hepatic resection. Unfortunately, only 10%-20% of patients with liver tumors can undergo surgical resection due to limited hepatic reserve, high surgical risk, or unfavorable tumor location. Ablation of liver tumors is currently the main alternative to formal liver resection. Tumor cell death is achieved through a number of technologies, which may be separated into three categories: chemical (percutaneous ethanol injection), cold-based (cryotherapy), and heat-based (radiofrequency and microwave ablation or laser hyperthermia). Although long-term data are limited, ablation may be curative in some patients with a three- and five-year survival rate approaching that of resection. The main factors to success include proper patient selection, excellent diagnostic and procedural imaging, and careful post-procedure management and follow up. Long-term success following tumor ablation will be most dependent on the underlying tumor biology and the ability to achieve a negative margin. Future directions in ablation will include the use of adjunctive agents such as chemotherapeutics, further advances in energy delivery, improved imaging and lesion targeting, and continued refinements of current technology and technique.

Carcinoma, Hepatocellular↗
PubMed2002

Development and initial testing of a multimedia program for computer-assisted cognitive therapy.

A multimedia program for computer-assisted psychotherapy has been developed to help patients learn cognitive therapy skills. The program is designed to provide psychoeducation, teach self-help methods, and give information to clinicians on the patient's progress in using the software. Multimedia technology is utilized to engage users in the learning process and to make the program accessible for persons who do not have computer or keyboard skills. A preliminary study with 96 subjects who used the software along with treatment as usual found that 75 (78.1%) completed the entire program. Users indicated a high rate of acceptance of this form of computer-assisted therapy, and mean scores on a measure of cognitive therapy knowledge were significantly improved.

Adult↗
PubMedDate not supplied

Current management of portal hypertension.

Portal hypertension can lead to life-threatening hemorrhage, ascites, and encephalopathy. This paper reviews the pathophysiology and multidisciplinary management of portal hypertension and its complications, including the indications for and techniques of the various surgical shunts. Variceal bleeding is the most dreaded complication of portal hypertension. It may occur once the portal-systemic gradient increases above 12 mm Hg, occurs in 30% of patients with cirrhosis, and carries a 30-day mortality of 20%. Treatment of acute variceal bleeding includes resuscitation followed by upper endoscopy for sclerosis or band ligation of varices, which can control bleeding in up to 85% of patients. Medical therapies such as vasopressin and somatostatin can also be useful adjuncts. Shunt therapy, preferably the placement of a TIPS, is indicated for refractory acute variceal bleeding. Recurrent variceal bleeding is common and is associated with a high mortality. Therapies to prevent recurrent variceal bleeding include chronic endoscopic therapy, nonselective beta-blockade, operative or nonoperative (TIPS) shunts, devascularization operations, and liver transplantation. Recommendations and a treatment algorithm are provided, taking into account both the etiology and the manifestations of portal hypertension.

Endoscopy, Gastrointestinal↗