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Biomedical subjects

D I Rosen

Publications and source records attributed to D I Rosen.

11 recordsLinked to original sources
PubMed1997

Development of a smart holmium:YAG laser lithotriptor.

BACKGROUND AND OBJECTIVE: The purpose of this study was to develop a feedback control system for the pulsed holmium:YAG medical laser that enhances tissue selectivity and safety by discriminating between soft and hard biological tissue such as urinary and biliary calculi and bone. STUDY DESIGN/MATERIALS AND METHODS: The ability to discriminate is achieved by monitoring prompt laser-induced visible/NIR photoemissions via retrograde transmission over the laser delivery fiber in conjunction with a developed detection algorithm. RESULTS: Experimental data are presented for a system that employs this discrimination scheme with an electro-optic shutter for rapid intrapulse feedback control of holmium laser-based lithotripsy procedures. The results demonstrate the feasibility of a lithotriptor that can deliver 1 J per pulse to calculi yet limit errant discharges to surrounding urinary tract tissue to < or = 0.1 J. CONCLUSION: Based on animal tissue safety data, the laser margin of safety is improved by an order of magnitude.

Algorithms↗
PubMed1993

The electromechanical impactor: the results of design modifications.

The first generation clinical electromechanical impactor was a 5F device that used a 3.0F electrohydraulic probe within a coiled spring with a blunt solder end cap. Clinical trials showed that this device fragmented 70% of the calculi but failed to fragment the harder stones. Applying the principle that impact kinetic energy is most dependent on velocity (KE = 1/2 MV2), 3 major design modifications were made to improve fragmentation efficiency: 1) the spring was changed from an extension to a compression type that captured and used more of each electrical spark, 2) the tip was changed from solder to lightweight titanium and 3) the tip shape was changed from blunt to conical. The result was a 41% increase in impact kinetic energy, a 40% increase in probe longevity and successful in vitro fragmentation of the harder calculi without compromise in tissue safety as determined by membrane perforation studies.

Animals↗
PubMed1990

Effects of shielded or unshielded laser and electrohydraulic lithotripsy on rabbit bladder.

The pulsed dye laser and electrohydraulic lithotriptor (EHL) are both effective devices for fragmenting urinary and biliary calculi. Both fragment stones by producing a plasma-mediated shockwave. Recently, a plasma shield consisting of a hollow spring and a metal end cap has been described for use with the laser and EHL devices in an attempt to minimize tissue damage without adversely affecting stone fragmentation rates. The tissue effects produced by a pulsed dye laser and an EHL device with and without plasma shields were examined and compared using rabbit urinary bladders. If blood was present, the unshielded laser perforated the bladder wall in two pulses. However, in the absence of blood, over 100 pulses were needed for the laser to perforate the bladder. A mean of six pulses were required to perforate the bladder wall with a shielded laser. The unshielded EHL perforated the bladder wall in two pulses, whereas, the shielded EHL required a mean of 35 pulses. Microscopically, areas of exposure revealed hemorrhage and tissue ablation. We conclude that all devices examined can produce significant tissue damage when discharged directly onto bladder epithelium.

Animals↗
PubMed1989

Acoustic and plasma-guided laser angioplasty.

The feasibility of using acoustic and plasma-guided laser (APGL) for angioplasty was studied in vitro. A flashlamp-pumped tunable dye laser operating at a wavelength of 504 nm (coumarin green) was used as the laser source. Acoustic signals were recorded with a hydrophone, which has a useful frequency response of up to 350 kHz. Plasma optical emissions were transmitted retrograde along the laser fiber and reflected through a beam splitter to an optical detection system consisting of a series of spectral filters (to transmit plasma radiation from 380 nm to 440 nm and block any 504 nm laser light) and a photomultiplier tube. Measurements of the acoustic and the plasma optical signals were obtained from blood, atheromatous plaque, and normal arterial wall. Results of monitoring show that it is possible to know without direct vision whether the laser energy is being discharged in the lumen (blood), on the normal arterial wall, or on the atheromatous plaque. Blood produced strong acoustic signals but no plasma signals; plaque produced strong plasma and strong acoustic signals. Neither plasma nor significant acoustic signals were produced by the normal arterial wall. These distinctions may allow clinical laser ablation of plaque to be performed with fewer complications.

Acoustics↗
PubMed1989

Plasma shield lasertripsy: in vitro studies.

A technique for safer and more effective pulsed laser lithotripsy of urinary and biliary calculi was investigated in vitro. The technique involves enclosing the distal end of the laser delivery fiber in a "plasma shield." The plasma shield is a specially designed metal cap that serves to transfer the laser-induced mechanical impulse to the calculus while shielding surrounding tissue from direct laser exposure and thermal radiation. The metal cap also offers the advantage of effectively blunting the sharp fiber tip and improving its visualization under fluoroscopy. Plasma shield lithotripsy using a 200 micron quartz fiber inserted into a section of a modified 0.034 in. diameter stainless steel guide wire was tested in vitro on a variety of calculi and compared with results obtained using a 200 micron laser fiber applied directly. Calculi tested included cystine, struvite and calcium oxalate dihydrate urinary stones and pigmented cholesterol gallstones. The laser source was a flashlamp-pumped dye laser producing pulses of 1.2 microsecond duration and operated at a wavelength of 504 nm and pulse repetition frequency of 5 Hz. The results show that plasma shield lasertripsy is as effective as direct lasertripsy for fragmenting gallstones, struvite and calcium oxalate dihydrate calculi, is potentially safer, and can fragment cystine calculi which the pulsed dye laser applied directly cannot.

Cholelithiasis↗