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Biomedical subjects

W Grundfest

Publications and source records attributed to W Grundfest.

At least 19 recordsLinked to original sources
PubMed2001

Ablation spectra of the human cornea.

Ablation of human corneal tissue with 193 nm excimer laser energy generates fluorescence in the near ultraviolet and visible regions of the spectrum. The fluorescence spectra from five human corneas were collected during ablation in vitro. We find that the fluorescence spectrum changes continuously as the cornea is ablated from the epithelial surface towards the endothelium. We reduced the dimensionality of the large data set resulting from each cornea by a principal components analysis. The three most significant principal component eigenvectors suffice to describe the observed spectral evolution, and independent analysis of each tissue sample produces a similar set of eigenvectors. The evolution of the calculated eigenvector weighting factors during ablation then corresponds to the observed spectral evolution. In fact, this evolution is qualitatively consistent between corneas. We suggest that this spectral evolution offers promise as a real-time surgical feedback tool.

Algorithms↗
PubMed1991

Biliary calculi fragmentation by a 308 nm excimer laser: a preliminary study.

The use of a 308-nm XeCl excimer laser for biliary stone fragmentation is reported. The 130-nsec laser pulses are delivered via UV grade fused silica fibers to the target stones immersed in normal saline solution and placed in direct contact with the fiber. Sixty biliary calculi, 20 cholesterol and 40 pigment, were fragmented in vitro. The energy delivered per unit mass of the stone is kept constant at 50 mJ/mg. The effect of laser repetition rate, energy fluence, and fiber core size on stone fragmentation was studied. Fragmentation thresholds for a variety of biliary calculi of known composition were measured. It was found that higher fragmentation efficiency was obtained with larger fluence, lower repetition rate, and fiber of larger core. Our study indicates that the 308-nm excimer laser may be effective as a laser lithotriptor with low threshold and good efficiency for biliary stone fragmentation.

Evaluation Studies as Topic↗
PubMed1991

Laparoscopic exploration of the common bile duct: experience in 16 selected patients.

The authors' initial experience with transcystic duct and direct laparoscopic approaches to the exploration of the common bile duct is reported. The technique requires standard laparoscopic equipment, specialized endoscopes, and instruments developed for urologic stone manipulations. After cholangiography confirmed the presence of common bile duct stones, common duct stone extraction was performed in 16 selected patients age 20-88 years. Stones ranged in size from 1 mm to 30 mm and they were unsuspected in 60% of the patients. Five patients had normal liver function tests and only 3 had clinical evidence of jaundice. Ductal exploration and stone extraction was successful in all 16 patients. One patient required a direct laparoscopic ductal exploration due to the presence of a common hepatic duct stone and the anatomy of the cystic duct. No major complications or deaths were observed in this series. Appropriately trained surgeons can safely and effectively perform laparoscopic common bile duct exploration and stone extraction in selected patients.

Adult↗
PubMed1991

Initiating events of acute coronary arterial occlusion.

Acute myocardial infarction is caused by coronary thrombosis on an ulcerated atheroma. We now believe that the predominant cause of this intimal disruption is the rupture of the atheroma through the intimal surface, caused by enzymes released by activated macrophages. The subsequent clinical course following atheroma disruption is determined by the rate and size of thrombus formation. Partially occlusive thrombi produce unstable angina; completely occlusive thrombi produce myocardial infarction; clot embolization can produce sudden death. The localized thrombus lyses within days. The healing process, however, is frequently accompanied by rapid local progression of the size of the atheroma at the site of intimal disruption. With healing of the intimal surface, the patient's clinical status stabilizes. Thus coronary disease is a cyclical phenomenon driven by cellular events within the atheroma and by the interaction of the atheroma with circulating blood elements.

Angina Pectoris↗
PubMed1991

Development of laparoscopic anterior seromyotomy and right posterior truncal vagotomy for ulcer prophylaxis.

This study investigated the feasibility of a laparoscopic antiulcer procedure. The following antiulcer operations were performed laparoscopically in 20 pigs: truncal vagotomy and pyloroplasty (n = 5), highly selective vagotomy (n = 5), right truncal vagotomy and left highly selective vagotomy (n = 5), and anterior seromyotomy and posterior truncal vagotomy (n = 5). Each procedure was videotaped and assessed in terms of ease of access, need for additional trocars, requirements for suturing, and complexity of the procedure. The anterior seromyotomy and posterior truncal vagotomy provided the optimal combination of antiulcer prophylaxis and adaptivity to the laparoscopic approach. We employed a Nd:YAG laser operating at 20 W delivered via a 600 micron sculpted tip which simplified the anterior seromyotomy. Anterior seromyotomy-posterior truncal vagotomy was then performed in three cadavers without evidence of perforation of the stomach. Our initial experience in a 46-year-old male demonstrates that the procedure can be performed with relative ease in humans. Thus, an effective antiulcer operation, anterior seromyotomy-posterior truncal vagotomy can be performed laparoscopically and may be a reasonable alternative for treating those patients who had a poor response to medical therapy.

Animals↗
PubMed1990

Percutaneous endoscopic laser lithotripsy of retained stones in the left hepatic duct. The role of the surgeon.

A 35-year-old woman with a retained stone in a branch of the left hepatic duct was referred to us. The stone was discovered on the postoperative T-tube cholangiogram. A flexible ureteroscope was introduced into the duct, under fluoroscopic and direct endoscopic vision and the pulse dye laser was used successfully to disintegrate the calculus. The postoperative course was uneventful. We suggest that in certain selected cases, the pulsed dye laser might be useful in disintegrating stones sited in difficult positions.

Adult↗
PubMed1990

Falloposcopy: a microendoscopic technique for visual exploration of the human fallopian tube from the uterotubal ostium to the fimbria using a transvaginal approach.

A transvaginal microendoscopic technique has been developed for safely exploring the human fallopian tube from the utero tubal ostium to the fimbria and adjacent peritoneal cavity. Falloposcopy was performed without complication or evidence of endotubal damage in 44 women, 38 of whom also underwent a concurrent laparoscopy. Eight women with normal tubes served as controls and 36 women with tubal damage underwent falloposcopy in an attempt to document endotubal defects. Previous salpingectomy in 13 women and ostial obstruction in 4 cases left 71 tubes available for falloposcopy. Technical failures, defined as an inability to negotiate the tubal lumen in the absence of obstructive disease occurred in 8 of 71 (11%) procedures. In 63 successful procedures, the tubal lumen was considered to be falloposcopically normal in 28 cases (44%) and contained defects ranging from partial to total obstruction secondary to intraluminal fibrosis within the intramural, isthmic, and ampullary segments in the remaining 35 tubes (56%). Falloposcopy provides a nonincisional modality for defining the normal and abnormal surface anatomy of the tubal epithelium.

Endothelium↗
PubMed1990

Excimer laser coronary angioplasty: American multicenter experience.

Second generation angioplasty devices remove rather than displace atherosclerotic plaque. For such devices to be useful they must be capable of addressing the major problems not solved by balloon catheters: difficult anatomy, abrupt reclosure, and restenosis. Laser angioplasty systems have proven difficult to adapt to treatment of coronary artery disease, because of heat generation, problems with perforation, and inflexibility of optical fibers. The AIS excimer laser coronary angioplasty system couples a 308 nm pulsed excimer laser to multifiber over-the-wire catheters of 1.3 mm, 1.6 mm, and 2.0 mm diameters. The laser's uniquely long pulse width (250 ns) allows delivery of higher energies through smaller fibers. Because the catheter system is front firing, risk of perforation is reduced. The Excimer Laser Coronary Angioplasty Registry involves six institutions investigating the AIS excimer system. This report deals with 255 lesions in the first 210 patients in the registry. The study cohort resembles a standard angioplasty population in terms of demographics, symptomatology, vessels dilated, and complications. Unlike a standard PTCA cohort, the ELCA patients had a higher prevalence of chronic total occlusions, calcified lesions, long lesions and diffuse disease. Both very distal lesions and those that had previously failed PTCA were successfully treated with ELCA. The laser was successful in 85% of cases, but adjunctive balloon angioplasty was required in the majority. There were no instances of perforation.

Adult↗
PubMed1990

Falloposcopy. A microendoscopic transvaginal technique for diagnosing and treating endotubal disease incorporating guide wire cannulation and direct balloon tuboplasty.

Direct visualization of the entire length of the fallopian tube lumen, from the uterotubal ostium to the fimbria, using a transvaginal approach, has been achieved. Small, flexible hysteroscopes with outside diameters (ODs) ranging from 3.3 to 4.5 mm and operating channel diameters of 1.5 to 1.8 mm were used to pass guide wires, over-the-wire catheters and a falloposcope with an OD of 0.5 mm safely along the fallopian tube lumen. Forty-three falloscopy procedures were performed. The normal falloposcopic appearance of the fimbrial, ampullary, isthmic and intramural tubal epithelium was characterized in eight cases. In 35 falloposcopies, endotubal lesions were found and characterized. They included 5 cases of intramural stenosis; 10 of isthmic stenosis; 5 of isthmic obstruction; 2 of salpingitis isthmica nodosa; 10 of nonobstructive endotubal disease from intraluminal adhesions, associated devascularization and epithelial atrophy in the intramural, isthmic and ampullary segments; 2 of hydrosalpinx; and 1 of an intratubal polyp. A technique of guide wire cannulation and balloon tuboplasty under hysteroscopic-falloposcopic-laparoscopic control was developed for attempting to dilate a stenotic tube, open up an obstruction or break down intraluminal adhesions. A combination of 32 guide wire cannulation and direct balloon tuboplasty (DBT) procedures was performed. Guide wire cannulation and DBT were effective in breaking down non-obstructive intraluminal adhesions in 6/10 cases (60%), dilating intramural or isthmic stenoses in 6/15 cases (40%) and negotiating an isthmic stricture secondary to salpingitis isthmica nodosa in 1/2 cases (50%). Those procedures failed to bypass complete fibrotic obstructions in 5/5 cases.(ABSTRACT TRUNCATED AT 250 WORDS)

Catheterization↗
PubMed1989

Excimer ablation of human intervertebral disc at 308 nanometers.

Excimer laser energy, which has been shown to photoablate tissue at a precisely controllable rate with minimal thermal damage, was applied to human intervertebral disc in an effort to develop a technique for percutaneous discectomy. Cadaveric samples of human disc were used. Excimer laser energy was produced by a XeCl, magnetically switched, long-pulse laser working at 308 nm, 20 Hz. Annulus tissue of approximately 1 mm thickness was placed in contact with the output tip of a 400 microns core diameter quartz fiber, and measurements of ablation rate were made at different radiant exposures. Ablation rates were found to vary linearly with radiant exposure, from 0.7 micron/pulse at 10 mJ/mm2 to 11.0 microns/pulse at 55 mJ/mm2, with a correlation coefficient of 0.984. Threshold radiant exposure, calculated by extrapolation, was found to be about 7 mJ/mm2. Histologic analysis showed a minimum of thermal damage in these specimens, and when ablated with modification to maintain constant fiber-tissue contact, thermal injury was nearly absent, as compared to samples ablated with Nd:YAG through a contact probe. Thermographic analysis, performed using the AGA 782 Digital Thermography system, showed increasing temperature with increasing radiant exposure, with a maximum temperature of 47.2 degrees C at 55 mJ/mm2. In that precise tissue ablation was demonstrated with minimal generated heat, and excimer energy at 308 nm is transmissible through fiber optics, excimer holds great promise for the development of a percutaneous discectomy technique.

Humans↗
PubMed1989

Thermal coronary angiography: a method for assessing graft patency and coronary anatomy in coronary bypass surgery.

Thermal coronary angiography was evaluated in 50 patients undergoing 137 saphenous vein and 48 internal mammary artery bypass grafts. A total of 177 thermal coronary angiograms were performed after completion of the distal anastomoses by injection of cold cardioplegia into the vein or by reperfusion with warmer blood in the internal mammary artery grafts. These angiograms provided details of graft and anastomosis patency, flow directions, and presence of native coronary stenoses. Temperature differences between the injectant and the epimyocardium of greater than 4 degrees C resulted in high-contrast images. Thermal coronary angiograms were obtained in 173 of the 177 studied bypass grafts; 172 grafts were patent, and 1 internal mammary artery graft was occluded. Unsuspected stenoses were detected at the site of four distal anastomoses. Subsequently, two anastomoses were successfully revised and three additional grafts performed. Ninety-six native coronary stenoses were located in the recipient coronary arteries. In ten instances, the thermal coronary angiograms were obscured by excess fat or myocardium, thereby impeding correct image analysis. We conclude that thermal coronary angiography can be clinically relevant and helps improve decision making during coronary artery bypass operations.

Adult↗
PubMed1989

Excimer laser ablation of the human lens at 308 nm with a fiber delivery system.

A 308 nm excimer laser has been used with a fiber delivery system to perform ablation of the human lens. Preliminary results demonstrate the system's ability to ablate lens nucleus and cortex selectively, preserving the anterior and posterior capsules. The total delivered energy necessary to ablate a human lens ranged from 35 to 63 joules. Laser tissue interaction and ablation rates were computed for the different components of the human lens (capsule, cortex, nucleus) for the operatively useful energy densities (fluences). Operative experience suggests that cortex and nucleus can be ablated while preserving the capsule if an adequate irrigation and aspiration system is developed. These results also suggest that this modality may be adequate for performing endocapsular cataract extraction. Laser tissue interactions were also computed at variable distances between the fiber tip and tissue. As this distance increased, the spread of the beam increased and a significant increase in energy was necessary to induce tissue ablation. This was due to the decrease in fluence with increasing distance to the target tissue and/or the absorption and scattering of the delivered energy within a short distance from the fiber tip by the ablated material. Evidence of a sonic effect was also present.

Aged↗
PubMed1989

Enterotomy fusion with laser energy: preliminary results in rabbit ileum.

The utility of enterotomy closure with the argon and CO2 lasers was examined in New Zealand white rabbit ileum. Thermal properties of 10 argon (0.5 W power for 30 s, energy fluence 230 J/cm2) and 10 CO2 (1.0 W power for 30 s, energy fluence 2700 J/cm2) laser-fused enterotomies were determined during acute fusion experiments using an AGA 782 digital thermographic camera. Healing of the fusions created by the two lasers was subsequently assessed in an additional group of 28 rabbits by comparing three 1.0-cm longitudinal ileal enterotomies, with each rabbit having both types of laser-welded closures and a sutured control. Thermal measurements made from the 10 closures with each laser revealed that the CO2 fusions generated significantly higher temperatures (max. 198 degrees C, mean 106 +/- 37 degrees C, n = 100) than argon (max. 85.2 degrees C, mean 60.5 + 8.1 degrees C, n = 100) p less than 0.001. In the healing studies, four rabbits died from weld failures (one argon and one CO2 disruption, two rabbits with both welds disrupted). Two additional rabbits died at 1 day and one at 10 days for undetermined reasons. The remainder of the animals were sacrificed at 1 (n = 11), 2 (n = 2) and 4 (n = 9) weeks postoperatively. Sutured closures exhibited more granulation tissue and adhesions surrounding the wounds than did welded closures and seven microabscesses were noted adjacent to sutured repairs. One of the CO2 repairs had an abscess at 4 weeks and none of the argon laser fusions had evidence of disruption or abscess.(ABSTRACT TRUNCATED AT 250 WORDS)

Abscess↗
PubMed1989

[Digital thermo-coronary angiography--development and validation of the method in comparison with conventional cine-coronary angiography].

We describe the technique-thermal coronary angiography (TCA)-for real-time assessment of coronary anatomy and flow. The goal of this study was to compare thermal coronary angiography to cine coronary angiography and to validate its value for detecting stenoses. We studied the exposed LAD both in beating and arrested hearts in 11 open-chest pigs by TCA and cine angiography. We used an AGA 782 Thermovision system combined with a TIC 8000 digital image processor providing coronary images with 0.1-0.2 mm spatial and 0.1 degrees C thermal resolution, and a CFR x-ray system. The coronary arteries were catheterized via the right carotid artery, using standard 5F catheters. The thermal camera was focused at a 1m-distance to the heart surface and the x-ray was angled to LAO position. We performed simultaneous thermal and cine angiography using Angiovist 370 at different temperatures (10-40 degrees C) and injection rates (1-2.5 ml/s). Different grades of stenoses were created by snares. Thermistor probe readings of the epimyocardium and the left atrial blood were performed to reference the thermal camera measurements. We obtained high resolution TCA images of both the coronaries and of the myocardial perfusion beds whenever there was greater than 4 degrees C difference between injectate and epicardial temperature. The TCA detection of stenoses as compared to cine angiography was 29/30 (96.6%) in arrested and 36/42 (85.7%) in beating hearts. Coronary occlusion produced immediate and dramatic perfusion defects as detected by TCA. TCAs were highly reproducible. Injection rate of 2 ml/s provided optimal thermal coronary images. Thermal angiograms of the LAD were sometimes affected by large crossing coronary veins, myocardial bridges, and excess of fat pretending nonexistent coronary stenosis. TCA is a highly sensitive and reproducible method as compared to standard coronary angiography and allows for detection of coronary stenoses. The image quality was best in arrested hearts.

Animals↗