Krishna M. Bhatta

Cystine Calculi—Rough and Smooth: A New Clinical Distinction

Four stones each from 2 populations of cystine calculi, 1 with a rough external surface (cystine-R) and the other smooth (cystine-S), were studied for their crystal structure with stereoscopic and scanning electron microscopy. Two stones each of cystine-R and cystine-S, calcium oxalate monohydrate, calcium oxalate dihydrate, struvite plus apatite and brushite were fragmented with extracorporeal shock wave lithotripsy and the fragmentability was compared. Fragments resulting from cystine-R and cystine-S extracorporeal shock wave lithotripsy were examined under the stereoscope to assess the plane of cleavage or fracture. Results show that cystine-R stones are comprised of well formed blocks of hexagonal crystals, whereas cystine-S calculi have small, irregular and poorly formed interlacing crystals. The center of cystine-R stones was similar to that of the periphery but the center of cystine-S stones was formed of blocks of hexagons similar to but smaller than the cystine-R calculi. Fragmentation with extracorporeal shock wave lithotripsy revealed that cystine-S stones are the least fragile, calcium oxalate dihydrate and struvite plus apatite were the most fragile, and cystine-R, brushite and calcium oxalate monohydrate calculi were in the intermediate fragility range. The possibility of the patient having a cystine-R calculus should be considered during therapeutic procedures.

Comparative study of different laser systems

OBJECTIVE To review lasers, laser physics, laser-tissue interaction, delivery systems, and their clinical applications relevant to gynecology. SETTINGS Gynecological Service at Massachusetts General Hospital (MGH) and MGH Laser Center. INTERVENTIONS None. DESIGN Laser literature review and personal experiences of the authors were used to prepare this manuscript. CONCLUSIONS Lasers have been used in gynecologic practice for cutting and coagulating purposes. Photodynamic therapy has been used clinically for malignant conditions and is being investigated for dysplastic lesions of the lower genital tract and for endometrial ablation. Laser welding has potential, but further work is required in this field before it finds a clinical application. The main lasers used in gynecology are CO2, neodymium-yttrium aluminum garnet (Nd:YAG), and potassium tatanyl-phosphate-doubled Nd:YAG. Pulsed Ho:YAG laser looks promising, as does diode lasers. Holmium-yttrium aluminum garnet and diode lasers will be soon available commercially. Improvements in delivery systems have increased user friendliness, and more developments in this area are anticipated, for example, a fiber-optic delivery system for CO2 lasers. We believe that enhanced understanding of laser technology will provide unique applications for development in gynecology.

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.

Clinical Experience With High Power (140 MJ.), Large Fiber (320 Micron) Pulsed Dye Laser Lithotripsy

The pulsed dye laser, at 504 nm. wavelength with a pulse duration of 1 microsecond, was used at 140 mj. per pulse via a 320 mu. (core) fiber for fragmentation of 72 ureteral calculi. The fragmentation efficiency and clinical results using the 140 mj./320 mu. fiber were compared to previous experience using the 60 mj./200 mu. (core) fiber. Fragmentation efficiency was significantly improved requiring many fewer laser pulses to fragment calculi of similar size and composition, and decreasing the need for auxiliary methods to complete stone fragmentation. The higher energy and larger fiber allowed for more efficient ureteroscopic ureteral stone fragmentation without compromising tissue safety.

Acoustic and plasma guided lasertripsy (APGL) of urinary calculi.

The feasibility of using pulsed laser generated acoustic and plasma optical emission signals to monitor laser fragmentation of urinary stones 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.-440 nm. and block any 504 nm. laser light) and a photomultiplier tube. Measurements of acoustic and plasma signals were taken from different urinary calculi, guidewires, catheters, blood, blood clots, bruised soft tissue and normal ureter. Signals were also obtained from stones placed in ureter of an ex vivo bovine urinary tract specimen. Results of monitoring both plasma and acoustic signals show that it is possible to determine, without direct vision, whether the laser is hitting stone, ureteral wall or lumen. Strong plasma and strong acoustic signals are produced by calculi; strong acoustic but no plasma signals suggest that the laser is hitting blood clot or bruised ureteral wall. Absent plasma and acoustic response indicate that the laser is discharging on normal ureter or in the lumen. These distinctions may allow clinical stone fragmentation without direct ureteroscopic vision.

Conversion of the Electrohydraulic Electrode to an Electromechanical Stone Impactor: Basic Studies and a Case Report

A 3.3F electrohydraulic electrode (Wolf 2137.23) has been confined within a spring with a metal end cap, irrigated with water and covered with a 0.003-inch metal sheath (outside diameter 5F). The electrohydraulic lithotripsy discharge (Wolf Generator 2137.50) at E1 causes the metal cap to extend 3 mm. at 1,500 cm. per second and creates an impact pressure of 600 to 800 bar. Stone fragmentation efficiency of the electromechanical impactor was equivalent to unshielded electrohydraulic lithotripsy (gallstone 2.83 mg. per pulse, struvite/apatite 1.41 mg. per pulse, cystine 0.41 mg. per pulse, uric acid 1.48 mg. per pulse and 100% calcium oxalate monohydrate 0.10 mg. per pulse). Studies of the discharge of the electromechanical impactor within the pig ureter showed that minimal ureteral submucosal edema and hemorrhage occurred at 300 shocks discharged at a single point, and disruption of the mucosa and partial injury to the muscle layer occurred after 600 shocks given at the site of a pinched pig ureter. Pushing the electromechanical impactor perpendicular to the wall of the pig bladder will create a mechanical perforation within 35 shocks (electrohydraulic lithotripsy within 2 shocks). One patient had excellent fragmentation of a lower ureteral mixed monohydrate and dihydrate stone under direct vision performed with the electromechanical impactor passed via a 9.5F ureteroscope. There was no evidence of mucosal injury with 500 shocks. The electromechanical impactor has been developed to provide a safe and inexpensive method of ureteral stone fragmentation or disimpaction. These studies were performed to establish limits of safety that may allow use of the electromechanical impactor for stone fragmentation in the ureter without the need for ureteroscopy.

Cystine Calculi: Two Types

Four stones each from two populations of cystine calculi, one with rough external surface (cystine-R) and the other with smooth external surface (cystine-S), were studied for their crystalline structure with scanning electron microscopy and stereoscopy. Two stones each of cystine-R and cystine-S, calcium oxalate monohydrate (COM), calcium oxalate dihydrate (COD), struvite/apatite, and brushite were fragmented with shock wave lithotripsy and the fragmentability compared. Fragments resulting from cystine-R and cystine-S shock wave lithotripsy were examined under a stereoscope to assess plane of cleavage or fracture. Results showed that cystine-R is comprised of well-formed blocks of hexagonal crystals; whereas, cystine-S has small, irregular crystals that are poorly formed and interlacing. The center of a cystine-R stone was similar to that of the periphery, but the center of a cystine-S stone was formed of blocks of hexagons similar to but smaller than the cystine-R. Fragmentation with shock wave lithotripsy revealed that cystine-S is the least fragile, COD and struvite/apatite are most fragile, and cystine-R, brushite, and COM are in the intermediate fragility range. The possibility of the patient having cystine-R calculus should be considered during therapeutic procedures.

Acoustical And Optical Feedback Guidance For Pulsed Laser Lithotripsy And Angioplasty

The feasibility of using acoustic and plasma optical feedback emissions for guidance during pulsed laser lithotripsy and angioplasty procedures was studied in-vitro. A flash-lamp 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 to 440 nm and block any 504 nm laser light) and a photomultiplier tube. Measurements of the laser-induced acoustic and the plasma optical emission signals were obtained from urinary and biliary calculi, ex-vivo bovine ureters, blood, blood clots, bile, 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, on healthy soft tissue, or on calculus or atheromatous plaque. Blood, blood clots, bile produced strong acoustic signals but no plasma signals; calculi and plaque produced strong plasma and strong acoustic signals. Neither plasma nor significant acoustic signals were produced by normal ureteral or arterial wall. These distinctions may allow clinical laser fragmentation of calculi or ablation of plaque to be performed with fewer complications.

Monitoring of Lasertripsy of Urinary Calculi Using Acoustic Emission Signals and Plasma Optical Emission Signals

The feasibility of using pulsed laser-generated acoustic emission signals and plasma optical emission signals to monitor laser fragmentation of urinary stones was studied in vitro. A flashlamppumped, tunable-dye laser, operating at a wave length 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 to block any 504 nm laser light) and a photomultiplier tube.