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W Barnhart

Publications and source records attributed to W Barnhart.

8 recordsLinked to original sources
PubMed1999

Carbon dioxide angiography: effect of injection parameters on bolus configuration.

PURPOSE: Predict the intravascular distribution of carbon dioxide during angiography. MATERIALS AND METHODS: Mathematical modeling was used to predict the flow pattern of CO2 in a pulsatile system as a function of the CO2 flow rate. Findings were validated in an in vitro pulsatile circuit. RESULTS: The annular flow pattern with filling of nearly the entire lumen with CO2 is the most desirable, followed by intermittent bubble flow (provided individual bubbles are large). Stratified flow relates to a continuous floating CO2 bubble. Configuration of the CO2 bolus depends on fluid properties, fluid velocity, flow rates, mean intraluminal pressure, pressure amplitude, pulse rate, and vessel diameter. In vessels with less than 10-mm inner diameter, annular flow can be achieved relatively easily with injection rates above 20-30 mL/sec. Higher rates are not expected to produce superior results. When imaging a 2-cm artery, the best that can be realized clinically is intermittent flow with large bubbles. Bubbles size increases with increasing CO2 flow rate. In aneurysms, only stratified flow can be achieved with reasonable injection rates. Periodicity of the flow patterns is determined by the pulsatile circuit and can produce indentations in the CO2 bolus, which can be mistaken for stenoses. CONCLUSIONS: Flow regime maps can be used to optimize bolus configuration during CO2 angiography.

Algorithms↗
PubMed1999

Sharp recanalization of central venous occlusions.

PURPOSE: To describe a sharp puncture technique for recanalization of chronic central venous occlusions that could not be traversed by a guide wire. MATERIALS AND METHODS: Five patients presented with six longstanding central venous occlusions that could not be traversed with a guide wire after thrombolysis. The occlusions occurred following radiation for lung carcinoma (n = 2) and indwelling venous catheters (n = 4). The length of venous occlusion was determined by simultaneously advancing transbrachial and transfemoral catheters to the site of occlusion. Initially, a curved guiding catheter with a Rosch-Uchida needle and, in subsequent patients, a coaxial sheathed needle with a 21-gauge stylet were used for recanalization. The recanalized veins were then balloon dilated and stents were placed. RESULTS: With use of this technique, recanalization was successful in five of the six occlusions. One occlusion was too long to traverse safely in one patient. Two patients were asymptomatic 16-18 months after the recanalization. CONCLUSION: This new technique offers an effective alternative to surgery in the treatment of central venous occlusion.

Aged↗
PubMed1999

Lung nodules: improved wire for CT-guided localization.

The authors designed three localization wires that increase the utility of percutaneous localization of lung nodules performed in conjunction with video-assisted thorascopic resection. In 17 patients, the custom-made wires dislodged less frequently than did commercially available wires (two of 11 vs three of six, respectively) while allowing the surgeon to apply gentle retraction pressure, which aided the resection.

Equipment Design↗
PubMed1996

1996 AUR Memorial Award. Densitometric analysis of eccentric vascular stenoses: comparison of CO2 and iodinated contrast media.

RATIONALE AND OBJECTIVES: The authors compared the accuracies of CO2 and iodinated contrast material in the densitometric quantification of eccentric vascular stenoses. METHODS: Five precision-machined eccentric phantom stenoses of 50%, 60%, 70%, 80%, and 90% cross-sectional area narrowing were integrated into a pulsatile ex vivo flow model, imaged with digital subtraction angiography (DSA), and analyzed with densitometry. Relationships between the actual and measured (densitometric) degree of cross-sectional area narrowing were evaluated by using linear regression analysis and paired Student t tests. Comparison measurements were obtained in en face and profile projections. In addition, the effect of iodinated contrast material concentration was evaluated over a range of dilutions (47-282 mg iodine per milliliter). RESULTS: CO2 yielded significantly more accurate results than did iodinated contrast material (282 mg iodine per milliliter) in the 50%, 60%, and 70% stenosis models when imaging was performed en face (P < .005). The best overall correlation was observed with CO2 DSA when imaging in profile (slope = 0.91, intercept = 2.42% actual stenosis, r = .99). The accuracy of densitometric stenosis estimation was inversely related to the concentration of iodinated contrast material. CONCLUSION: CO2 DSA densitometry, under the conditions of these experiments, yields quantitative measures of relative cross-sectional area narrowing that are comparable with, and under some circumstances surpass, those obtained with iodinated contrast material-based DSA. In this model, CO2 was more useful than iodinated contrast material in 50%-70% stenosis when imaging in the least-optimal plane of stenosis quantification, the en face projection.

Absorptiometry, Photon↗
PubMed1990

New guide wire for high-flow infusion.

A new open-ended guide wire with a large internal diameter was compared with two other open-ended guide-wire and catheter infusion systems. Simple experiments were performed to compare flow rates and ability to track. The larger internal diameter of the new wire allowed higher flow rates and accepted an 0.025-inch (0.64-mm) guide wire. The flexibility of the new infusion wire was shown to be equivalent to that of the catheter system. The authors conclude that the new wire has advantages in terms of flow rates and ability to track, compared with presently available infusion systems.

Catheterization↗
PubMedDate not supplied

Six-month follow-up after thermal balloon angioplasty in canine iliac arteries.

We performed thermal balloon angioplasty in 10 iliac arteries in 5 mongrel dogs. By perfusing a modified angioplasty balloon with hot (100 degrees C) saline, a mean balloon temperature of 84 degrees C was obtained. Angiographic and histologic follow-up at 6 months revealed no thrombosis or aneurysm formation but it did reveal fibrotic transformation of the media. Initial overdilatation was maintained in 9 of 10 arteries. We conclude that medial sclerosis induced by thermal balloon angioplasty does not result in aneurysm or thrombosis in dogs.

Aneurysm↗
PubMedDate not supplied

Percutaneous ureteral clipping: long-term results and complications.

PURPOSE: The authors present their experience with ureteral clipping in patients with urinary fistulas. MATERIALS AND METHODS: The authors retrospectively reviewed records from eight patients in whom 14 ureters were ligated with use of a percutaneously applied stainless steel clip as treatment for urinary fistulas. All patients were female and had undergone pelvic radiation for treatment of cervical carcinoma (n = 7) or endometrial carcinoma (n = 1). Permanent urinary diversion was via percutaneous nephrostomy, which required routine change, at which time recurrence of symptoms and ureteral leakage were determined. Duration of follow-up (patient survival) ranged from 2 weeks to 17 months (mean, 7.1 months). RESULTS: All patients had significant improvement in their symptoms, with seven patients achieving complete perineal dryness. Two patients had recurrence of perineal symptoms due to nephrostomy tube blockage, which was successfully managed by means of interventional techniques. CONCLUSIONS: The authors believe that ureteral clipping is a safe and effective technique in the management of ureteral fistulas due to pelvic neoplasm and its treatment, despite the short life expectancy of these patients.

Female↗