Excimer laser photoablation in glaucoma filtering surgery.
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Animals↗
Biomedical subjects
W Grundfest
Publications and source records attributed to W Grundfest.
A perspective of coronary disease seen through the arteries of living man.
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Coronary Disease↗
Coronary angioscopy in patients with unstable angina pectoris.
To visualize intracoronary lesions in patients with different clinical expressions of coronary disease, we performed coronary angioscopy during coronary-artery bypass surgery in 10 patients with unstable angina and 10 patients with stable coronary disease. We examined a total of 32 vessels, using flexible fiberoptic angioscopes. Twenty-two vessels had no acute intimal lesion; three had complex plaques, six had thrombi, and one had both. Coronary angiography correctly identified the absence of complex plaque and thrombus in 22 vessels, but it detected only one of four complex plaques and one of seven thrombi. On angioscopy, none of the 17 arteries in the patients with stable coronary disease had either a complex plaque or thrombus. In the "offending" arteries of the patients with unstable angina, all three patients with accelerated angina had complex plaques and all seven with angina at rest had thrombi. We conclude that angioscopy frequently reveals complex plaques or thrombi not detected by coronary angiography. Our observations suggest that anginal syndromes that are refractory to medical treatment can be caused by unstable pathologic processes in the intima. Ulceration of plaques may increase the frequency and severity of effort angina, and the subsequent development of partially occlusive thrombi may cause unstable rest angina.
Adult↗
Thermal effects of high-field (1.5 tesla) magnetic resonance imaging of the spine. Clinical experience above a specific absorption rate of 0.4 W/kg.
Current safety guidelines recommend limiting the exposure to radiofrequency (RF) radiation used for clinical magnetic resonance imaging to a whole body average specific absorption rate (SAR) of 0.4 W/kg. Since it may be desirable to image with SARs that exceed this level during MRI of the spine, we evaluated the thermal responses associated with these procedures. Body and skin temperatures were determined in 25 patients immediately before and after MRI. Since the eye is particularly susceptible to thermal injury, corneal temperature was also measured. High-resolution thermography was performed on three subjects to evaluate the surface heating pattern and identify potential thermal 'hot spots'. A 1.5 tesla/64 MHz MRI system with quadrature transmission and reception was used iN this study. The whole body average specific absorption rate ranged from 0.5 to 1.3 W/kg. Ambient conditions were room temperature 20-24 degrees C and relative humidity between 40 and 50 per cent. There was a slight but statistically significant (p less than 0.01) increase in body temperature after MRI (36.5 +/- 0.4 to 36.7 +/- 0.4 degrees C). Temperatures of the hand (30.4 +/- 1.4 to 31.2 +/- 1.0 degrees C), positioning isocenter (32.1 +/- 0.6 to 32.9 +/- 0.5), and cornea (32.5 +/- 0.6 to 32.9 +/- 0.5 degrees C) also increased a statistically significant amount. Thermographic imaging revealed normal heating patterns with no surface 'hot spots'. We conclude that the temperature changes associated with MRI of the spine at the SARs we studied were well below known thresholds for adverse effects and do not appear to be harmful to patients.
Adult↗
Intraoperative coronary angioscopy. Technique and results in the initial 58 patients.
Coronary angioscopy provides images of intravascular detail with greater than 0.2 mm spatial resolution and excellent contrast resolution. Using endoscopes of 1.25 to 1.8 mm outer diameter, we performed intraoperative angioscopy of the coronary arteries or saphenous vein grafts, or both, in 58 patients. Eighty-one native coronary arteries and 43 vein grafts were examined. A clear viewing field was created by infusion of crystalloid cardioplegic solution through the aortic root during cardiopulmonary bypass. Technical details crucial for obtaining high-quality images were as follows: sufficient coronary perfusion by cardioplegic solution to displace all blood; adequate intraluminal illumination; and high-quality fiberoptic and lens systems. Incomplete studies in approximately 14% of patients were related to failure to achieve these technical details and lack of scope steerability. In 30% of patients, previously unrecognized anatomic details were revealed by angioscopy. These included intimal flaps at the site of vein-to-artery anastomoses, atheromatous plaques with adherent thrombi, and hemorrhagic ulcerated plaques, not recognized on angiography. Although a coronary intimal flap developed proximal to the anastomosis during retrograde examination in two patients, no serious complications occurred as a result of the procedure. We conclude that intraoperative angioscopy is safe, provides novel information that may be clinically relevant, and has future potential for development of the techniques for coronary endarterectomy and intraoperative balloon and laser angioplasty.
Angina, Unstable↗
Biliary lithotripsy as an adjunct to laparoscopic common bile duct stone extraction.
We investigated various energy sources and delivery systems suitable for fragmentation of common duct calculi by a laparoscopic technique. We evaluated electrohydraulic lithotripsy (EHL) using 1.9-Fr probe delivering 80 W and laser lithotripsy using a 200-micron(s) fiber delivering 30-70 mJ/pulse at 5-20 Hz. In vitro biliary stone fragmentation analysis suggested that the laser lithotripsy produced a more controllable fragmentation than EHL. Initial attempts to employ EHL techniques in animal models resulted in common bile duct injury or inadequate fragmentation of stones. In contrast, biliary lithotripsy was accomplished in pigs using the pulsed-dye laser at 10 Hz and 60 mJ/pulse. Histologic evaluation revealed no evidence of ductal injury related to laser stone fragmentation. Subsequently, laser common duct lithotripsy was used in two human subjects. One patient had a 1.8-cm impacted ampullary stone and one patient had a 3-cm intrahepatic stone. In both cases, the stones were removed laparoscopically after laser fragmentation. Our experience suggests that the laser lithotripsy may facilitate laparoscopic common duct stone extraction procedures.
Adult↗
A comparison of excimer laser (308 nm) ablation of the human lens nucleus in air and saline with a fiber optic delivery system.
BACKGROUND: Photoablation with excimer lasers has demonstrated precise tissue cutting and minimal thermal damage. Potential ophthalmic applications of these lasers include remodelling of the corneal surface, glaucoma treatment, and phacoablation. Ablation of human lens with a 308 nm XeCl excimer laser light delivered through a fiber has been demonstrated in preliminary experiments. Intraocular delivery of laser light must be done in a fluid medium to preserve the integrity of ocular structures. However, little information is available on the effect of the fluid media on the ablation process. Therefore, a series of experiments was conducted to determine whether the ablation of human lens nucleus at 308 nm via a fiber differs in air and saline media. METHODS: Ablation of human lens nuclei (n = 30) was conducted with a XeCI excimer laser (308 nm) coupled to a 600 microns core size fiber. Irradiation was performed at 2.8 mJ/cm2 energy density and 20 Hz. The fiberoptic was brought to contact with the lens nucleus and remained fixed for the duration of irradiation. Variables consisted of the medium (air or saline) and number of pulses delivered (100 to 10,000). Following establishment of the tissue shrinkage ratio, the depth of each crater and the tissue volume removed were measured histologically. The histological features of nucleus ablation in air and in saline were also examined with both light and scanning electron microscopy. RESULTS: Light microscopy revealed that the average zone of thermal damage adjacent to the crater is thinner in the presence of saline (60 microns, SD = 6 microns) than it is in air (90 microns, SD = 12 microns). In both media, the thickness of the zone of thermal damage is greater at the surface than it is at its base. Following irradiation in air, deep sharpedged craters with smooth walls are formed. Craters formed by irradiation in saline are characterized by reduced depth and irregular walls. For the same number of pulses applied (500, 1000, and 2000), the mean depth of ablation per pulse in air (8.6 to 2.7 microns/pulse) was greater by approximately a factor of two than that in saline (4.10 to 1.30 microns/pulse) at P < .01. However, the mean ablated volume removed per pulse was greater in saline (0.00250 to 0.00150 mm3/pulse) than in air (0.00120 to 0.00080 mm3/pulse), for the same number of pulses (1000, 2000) at P < .01. CONCLUSIONS: In comparing the data for the same number of pulses applied in air and in saline, it appears that the depth of crater formed by irradiation in air is deeper than that in fluid. The overall volume ablated is greater in fluid than it is in air at 1000 and 2000 pulses. Additionally, the zone of thermal damage is thinner in the presence of saline than it is in air. Smoother crater shapes were observed following irradiation in air than in saline. These results suggest that under this specific experimental setup, the ablation in saline is different from that in air.
Aged↗