Spectral diagnosis of atherosclerosis using an optical fiber laser catheter.

This communication demonstrates that fluorescence spectra of human aorta with good S/N ratios can be collected using an optical fiber laser catheter. The performance of this catheter is compared to a non-fiber optic collection system with an equivalent delivery/collection geometry. For a given sample, fluorescence lineshapes obtained using the two systems are identical; differences in peak fluorescence intensity are related to the different collection efficiencies of the two systems. It is shown that the fluorescence lineshape of arterial tissue depends on the delivery/collection geometry of the detection system, and that this is due to the interaction of absorption and fluorescence within the artery wall. This effect is investigated systematically using a specially designed collection system. Results are analyzed qualitatively using a simple, one-dimensional model of tissue fluorescence. With this analysis, we present design requirements for a collection system in which such geometric effects are eliminated, and show that our optical fiber laser catheter satisfies these requirements.

Simple adaptor using a Zeiss observer tube on a Nikon slit lamp.

A simple adaptor was manufactured to allow fitting of a Zeiss beam splitter and observer tube onto a Nikon slit lamp YAG laser. No noticeable optical or mechanical problems have been experienced with this cost-saving device.

[The practicality of laser-Doppler spectrometry in andrology]. / Untersuchungen zur Praktikabilität der Laser-Doppler Spektrometrie in der Andrologie.

Hereby we inform about the experimental results obtained using the Lazymot apparatus. It was shown that the assay for both the sperm density and the sperm motility rate are most unreliable. Marked differences were shown between the results obtained from the manual counting procedures and those with the Lazymot device. The input of work into using this apparatus shows no correlation to the output of results. Therefore the Lazymot device is not useful for the routine-laboratory diagnostic.

The argon "contact" laser scalpel: technical considerations.

The authors describe the use of a new contact argon laser scalpel designed specifically for hand-controlled cutting and hemostasis. This instrument delivers energy precisely to targeted tissue and produces minimal damage to adjacent healthy structures. Potential clinical applications are discussed.

The argon contact laser scalpel: a study of its effect on atherosclerosis.

A new argon laser scalpel (ALS) that delivers radiation to tissue by direct contact was used to perform endarterectomies on atherosclerotic rabbit aortas in vivo. The resultant effects were compared to those induced by CO2 laser (CO2) and conventional surgical endarterectomy (END) to determine whether this instrument might be useful in the treatment of occlusive cerebrovascular disease. Light microscopy of the treated aortic segments revealed significantly more atheroma removed and less damage to the underlying media in the ALS segments compared to the CO2 segments. Electron microscopy showed that the ALS surface and distal intima-media interface were smoother and more even than those of the CO2 or END groups. Prostacyclin synthesis, as measured by 6-keto-prostaglandin F1a levels, was significantly reduced in the ALS compared to the END and control segments. These results indicate that the ALS is superior to CO2 in performing open laser endarterectomies, but such treatment places the atherosclerotic blood vessel at greater risk for thrombotic complications during the early postoperative period that does surgical endarterectomy. It is conceivable that a contact laser may be useful in the smooth welding of the distal edge of an atheroma (i.e., during carotid endarterectomy) and for the transcatheter ablation of surgically inaccessible obstructions of the cerebral circulation.

Optical trapping and manipulation of single cells using infrared laser beams.

Use of optical traps for the manipulation of biological particles was recently proposed, and initial observations of laser trapping of bacteria and viruses with visible argon-laser light were reported. We report here the use of infrared (IR) light to make much improved laser traps with significantly less optical damage to a variety of living cells. Using IR light we have observed the reproduction of Escherichia coli within optical traps at power levels sufficient to give manipulation at velocities up to approximately 500 micron s-1. Reproduction of yeast cells by budding was also achieved in IR traps capable of manipulating individual cells and clumps of cells at velocities of approximately micron s-1. Damage-free trapping and manipulation of suspensions of red blood cells of humans and of organelles located within individual living cells of spirogyra was also achieved, largely as a result of the reduced absorption of haemoglobin and chlorophyll in the IR. Trapping of many types of small protozoa and manipulation of organelles within protozoa is also possible. The manipulative capabilities of optical techniques were exploited in experiments showing separation of individual bacteria from one sample and their introduction into another sample. Optical orientation of individual bacterial cells in space was also achieved using a pair of laser-beam traps. These new manipulative techniques using IR light are capable of producing large forces under damage-free conditions and improve the prospects for wider use of optical manipulation techniques in microbiology.

Contact application of Nd:YAG laser through a fiberoptic and a sapphire tip.

We evaluated the effects of Nd:YAG laser energy directly applied to ocular tissue through a fiberoptic and a sapphire tip. All ocular tissue could be easily cut with the maximum 4 watts of energy. The coagulated borders extended 20 to 200 mu into the healthy tissue depending on the speed with which the cutting was performed.

A contact Nd:YAG laser to resect large ciliary body and choroidal tumors.

We used a contact Nd:YAG laser fit with a 0.2-mm diameter sapphire tip to excise a large (5 1/2 clock hour) iris ciliary body-choroidal tumor and a large (15 X 8 X 3 mm) choroidal tumor. The cutting and coagulation action of the laser helped to minimize intraoperative and postoperative hemorrhage.

Illumination and detection systems for quantitative fluorescence microscopy.

Systems are described for the illumination and detection of light microscope images of fluorescence in living cells at low levels of excitation. The illumination system is based on the use of an acousto-optic modulator to control the wavelength and power of the excitation beam. The detection system utilizes an image intensifier coupled with a television camera to acquire images at extremely low intensities. Both the illumination and detection systems have superior performance compared to existing devices.

Efficiency and safety of optically modified fiber tips for laser angioplasty.

To evaluate the safety and efficiency of optically modified fiber tips, craters were created in human cadaver atherosclerotic arterial walls using sapphire contact probes and lensed fibers connected to a continuous wave neodymium yttrium aluminum garnet (Nd-YAG) laser. Laser energy was emitted at a constant level of 50 J. The sapphire contact probe catheter consisted of a round 2.2 mm diameter synthetic sapphire attached to an 8F catheter into which a 0.2 mm diameter optical fiber was inserted with the distal tip maintained at 3 mm from the sapphire. The lensed fiber catheter consisted of a 0.2 mm optical fiber at the end of which a 1 mm diameter lens was made. The fiber was inserted into a 5F low profile balloon catheter with the lens maintained 3 mm beyond the catheter tip. During laser emissions the catheter tips were maintained in a stationary position in contact with tissue targets immersed in blood at an angle of 90 degrees. The diameter of holes at the entry and exit of craters, the depth of craters and thermal injury to adjacent tissue (rim of carbonization and vacuolization) were measured with microscopy. The volume of tissue removed was derived from these values. Controlled effect index was determined as the ratio of diameter of holes and the extent of thermal injury. Efficiency was determined as the ratio of volume of tissue removed and the energy required to vaporize tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Ultrasonic assessment of skin and wounds with the scanning laser acoustic microscope.

The aim of the present study was to test the hypothesis that ultrasonic propagation properties in skin and wound tissue would correlate with material properties such as collagen content, water content, and tensile strength of those tissues. Both ultrasonic speed and ultrasonic attenuation coefficient were directly correlated with tissue collagen content, [r = 0.80 and r = 0.56, respectively (p less than 0.001)]. In addition, ultrasonic speed and attenuation coefficient were inversely correlated with tissue water content, [r = -0.57 and r = -0.73, respectively (p less than 0.001)]. Tensile strength also correlated very significantly with ultrasonic speed (r = 0.90, p less than 0.001), and significantly with attenuation coefficient (r = 0.58, p less than 0.001). The results demonstrate the feasibility of using ultrasound for noninvasively determining the material properties of biologic tissues including healing cutaneous wounds.