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Biomedical subjects

G M Preminger

Publications and source records attributed to G M Preminger.

At least 73 records · Page 4Linked to original sources
PubMed1998

Secured medical imaging over the Internet.

The Internet has established itself as an affordable, extremely viable and ubiquitous communications network that can be easily accessed from virtually any point in the world. This makes it ideally suited for medical image communications. Issues regarding security and confidentiality of information on the Internet, however, need to be addressed for both occasional, individual users and consistent enterprise-wide users. In addition, the limited bandwidth of most Internet connections must be factored into the development of a realistic usermodel and resulting protocol. Open architecture issues must also be considered so that images can be communicated to recipients who do not have similar programs. Further, application-specific software is required to integrate image acquisition, encryption and transmission into a single, streamlined process. Using Photomailer software provided by PhysiTel Inc., the authors investigated the use of sending secured still images over the Internet. The scope of their investigation covered the use of the Internet for communicating images for consultation, referral, mentoring and education. Photomailer software was used at several local and remote sites. The program was used for both sending and receiving images. It was also used for sending images to recipients who did not have Photomailer, but instead relied on conventional email programs. The results of the investigation demonstrated that using products such as Photomailer, images could be quickly and easily communicated from one location to another via the Internet. In addition, the investigators were able to retrieve images off of their existing email accounts, thereby providing greater flexibility and convenience than other systems which require scheduled transmission of information on dedicated systems. We conclude that Photomailer and similar products may provide a significant benefit and improve communications among colleagues, providing an inexpensive means of sending secured images on the Internet.

Computer Communication Networks↗
PubMed1997

Ureteral Stones Clinical Guidelines Panel summary report on the management of ureteral calculi. The American Urological Association.

PURPOSE: The American Urological Association convened the Ureteral Stones Clinical Guidelines Panel to analyze the literature regarding available methods for treating ureteral calculi and to make practice policy recommendations based on the treatment outcomes data. MATERIALS AND METHODS: The panel searched the MEDLINE data base for all articles related to ureteral calculi published from 1966 to January 1996. Outcomes data were extracted from articles accepted after panel review. The data were then meta-analyzed to produce outcome estimates for alternative treatments of ureteral calculi. RESULTS: The data indicate that up to 98% of stones less than 0.5 cm. in diameter, especially in the distal ureter, will pass spontaneously. Shock wave lithotripsy is recommended as first line treatment for most patients with stones 1 cm. or less in the proximal ureter. Shock wave lithotripsy and ureteroscopy are acceptable treatment choices for stones 1 cm. or less in the distal ureter. CONCLUSIONS: Most ureteral stones will pass spontaneously. Those that do not can be removed by either shock wave lithotripsy or ureteroscopy. Traditional blind basket extraction, without fluoroscopic control and guide wires, is not recommended. Open surgery is appropriate as a salvage procedure or in certain unusual circumstances.

Humans↗
PubMed1997

Controlled, forced collapse of cavitation bubbles for improved stone fragmentation during shock wave lithotripsy.

The feasibility of using controlled, forced collapse of cavitation bubbles for improved stone fragmentation during shock wave lithotripsy was demonstrated using microsecond tandem shockwave pulses. High-speed photography revealed that a secondary shock wave, released in less than 500 microseconds (microsec.) following a lithotripter-generated shock wave, can be used to control and force the collapse of cavitation bubbles toward target concretions. This timely enforced shockwave-bubble interaction was found to greatly enhance the cavitational activity near the stone surface, with a resultant up to 43% increment in stone fragmentation. Since most of the cavitation energy is directed and concentrated toward the target stones and fewer shock waves are needed for successful stone comminution, tissue injury associated with this new lithotripsy procedure may also be reduced. This novel concept of shock wave lithotripsy may be used to improve the treatment efficiency and safety of existing clinical lithotripters, as well as in the design of new shock wave lithotripters.

Feasibility Studies↗
PubMed1997

Ethnic and geographic diversity of stone disease.

OBJECTIVES: To ascertain diversity or similarity in stone prevention and problems among different countries around the world. METHODS: Urolithiasis research groups from 10 countries completed a questionnaire. RESULTS: Cost of extracorporeal shock wave lithotripsy (ESWL) was considerably greater than that of drugs in four countries, and equivalent in remaining countries. Stone composition was similar among different countries. Certain urinary risk factors were associated with particular countries, probably from dietary indiscretions. ESWL was used in the majority of patients and open surgery in a minority of patients, except in one country. Medical diagnostic evaluation was used in the majority of patients except in one country. Drug treatment was nonselective, and provided to a minority of recurrent stone-formers. CONCLUSIONS: There is considerable similarity in stone presentations and problems throughout the world. The diversity is likely to be due to nutritional-environmental and socio-political-economic factors.

Cost-Benefit Analysis↗
PubMed1997

Management of calyceal calculi.

Management of calyceal calculi has changed dramatically during the past 20 years. Minimally invasive techniques virtually have replaced open surgical stone removal. Even large and complex calyceal calculi may be treated effectively with these minimally invasive techniques. Although open surgical stone removal is performed infrequently, a clear understanding of the subtle renal anatomy aids the urologist in more effectively treating patients with calyceal calculi and in limiting surgical complications.

Diverticulum↗
PubMed1997

Transient oscillation of cavitation bubbles near stone surface during electrohydraulic lithotripsy.

Using high-speed photography and acoustic emission measurements, we studied the dynamics of a transient cavitation bubble near a stone surface and the concomitant shockwaves generated during electrohydraulic lithotripsy (EHL). At each spark discharge, a vapor plasma and subsequently a cavitation bubble oscillating around the tip of an EHL probe are produced. Simultaneously, three distinctive shockwave pulses are generated. The first shockwave is produced by the rapid expansion of the vapor plasma, while the second and third waves are produced by rebounds of the cavitation bubble. Depending on the proximity of the probe to the stone surface, the collapse of the cavitation bubble may be symmetric, resulting in a strong shockwave emission; or asymmetric, leading to the formation of a liquid jet. For the Nortech AUTOLITH lithotripter with a 1.9F probe that was used in this study, maximum shockwave emission is produced when the probe is about 1 mm from the stone surface, whereas the maximum jet velocity is produced when the probe tip is at distance equivalent to the maximum bubble radius of about 3 mm. These findings are consistent with clinical experience, which suggests that for optimal treatment results, the EHL probe should be placed close to the stone surface.

Acoustics↗
PubMed1997

Inertial cavitation and associated acoustic emission produced during electrohydraulic shock wave lithotripsy.

The inertial cavitation and associated acoustic emission generated during electrohydraulic shock wave lithotripsy were studied using high-speed photography and acoustic pressure measurements. The dynamics of cavitation bubble clusters, induced in vitro by an experimental laboratory lithotripter, were recorded using a high-speed rotating drum camera at 20,000 frames/s. The acoustic emission, generated by the rapid initial expansion and subsequent violent collapse of the cavitation bubbles, was measured simultaneously using a 1-MHz focused hydrophone, The expansion duration of the cavitation bubble cluster was found to correlate closely with the time delay between the first two groups of pressure spikes in the acoustic emission signal. This correlation provides an essential physical basis to assess the inertial cavitation produced by a clinical Dornier HM-3 shock wave lithotripter, both in water and in renal parenchyma of a swine model. In the clinical output voltage range (16-24 kV), the expansion duration of the primary cavitation bubble cluster generated by the HM-3 lithotripter in water increases from 158 to 254 microseconds, whereas the corresponding values in renal parenchyma are much smaller and remain almost unchanged (from 71 to 72 microseconds). In contrast, subsequent oscillation of the bubble following its primary collapse is significantly prolonged (from 158-235 microseconds in water to 1364-1373 microseconds in renal parenchyma). These distinctive differences between lithotripsy-induced inertial cavitation in vitro and that in vivo are presumably due to the constraining effect of renal tissue on bubble expansion.

Acoustics↗
PubMed1997

A multicenter clinical trial investigating the use of a fluoroscopically controlled cutting balloon catheter for the management of ureteral and ureteropelvic junction obstruction.

PURPOSE: We assessed the efficacy of a fluoroscopically controlled cutting balloon catheter for the treatment of ureteropelvic junction and ureteral strictures. MATERIALS AND METHODS: A multicenter trial was performed that included 66 endopyelotomies and 49 endoureterotomies. To our knowledge this study represents the largest number of patients with ureteropelvic junction obstruction and ureteral strictures tested with this device to date. RESULTS: With a mean followup of 7.8 months (range 1 to 17.9) the patency rate was 77% for endopyelotomy, with 72% of the primary and 100% of the secondary ureteropelvic junction obstructions remaining patent. The endoureterotomy patients were followed for an average of 8.7 months (range 1.2 to 17.0), with a patency rate of 55%. CONCLUSIONS: A cutting balloon endoscopic incision is effective in the majority of cases, with patency rates for endopyelotomies and endoureterotomies that mirror current endourological reports using other, albeit more time intensive and more invasive, incisional techniques.

Adolescent↗
PubMed1996

Long-term follow-up of Acucise incision of ureteropelvic junction obstruction and ureteral strictures.

OBJECTIVES: There are few data on the long-term effectiveness of various endoureterotomy procedures. One such technique for the treatment of ureteral strictures and ureteropelvic junction (UPJ) obstruction utilizes a recently developed ureteral cutting balloon catheter, Acucise. This device may be used under fluoroscopic guidance alone, which significantly reduces operating time. The purpose of this study is to determine the long-term efficacy of the Acucise balloon in treatment of ureteral strictures and UPJ obstruction. METHODS: Fifteen patients have been treated with the Acucise balloon, with an average follow-up of 21.6 months. Five of the patients have been followed for more than 2 years, and 11 of the patients had greater than 1 year follow-up. RESULTS: The overall success rate, defined as resolution of obstruction radiographically or disappearance of symptoms, or both, was 73%, with only 4 overt failures. All but one of the procedures were completed in 45 minutes or less, and 13 of the 15 patients were treated as outpatients. There were two significant complications. Seventy-five percent (3 of 4) of the treatment failures occurred within the first 4 months following original procedure. Of the 4 total failures. 2 patients had ureteral strictures greater than 2 cm in length, which were likely ischemic in nature secondary to previous surgeries. One patient, with a primary UPJ obstruction, was found to have a crossing vessel at subsequent open pyeloplasty. CONCLUSIONS: The Acucise cutting balloon offers the urologist a rapid and effective alternative for the management of ureteral strictures and UPJ obstruction. In our experience, early results (3 to 4 months) are usually indicative of long-term success. Proper patient selection may further improve long-term results of this simple, innovative technique.

Adolescent↗
PubMed1996

Percutaneous transhepatic endoscopic electrohydraulic lithotripsy of biliary tract calculi after orthotopic liver transplantation.

The development of biliary tract calculi after orthotopic liver transplantation presents a unique clinical problem. Previously described techniques for removing biliary stones by shock wave lithotripsy, litholytic therapy with oral bile acids, and endoscopic mechanical extraction may be ineffective or contraindicated in liver transplant patients. For this reason, percutaneous transhepatic electrohydraulic lithotripsy (EHL) was performed using an 11 French flexible ureteroscope in two pediatric patients who developed biliary tract calculi following orthotopic liver transplant. There were no complications and postoperative follow-up over 4 years has been uneventful. To our knowledge, these represent the first reported cases of percutaneous transhepatic endoscopic EHL to fragment biliary tract stones in a transplanted liver, which for us has been a safe and effective therapeutic option.

Adolescent↗
PubMed1996

Laparoscopic radical prostatectomy in the canine model.

The purpose of this study was to determine the feasibility of performing laparoscopic radical prostatectomy in a canine model. Laparoscopic radical prostatectomy was performed on six adult male canines. A new endoscopic needle driver was used to construct a secure vesicourethral anastomosis. Average operative time required to complete the procedure was 304 min (range 270-345 min). Dissection of the prostate gland took an average of 67 min (range 35-90 min), and construction of the vesicourethral anastomosis took 154 min (rage 80-240 min). There were no intraoperative complications and only one postoperative complication (anastomotic leak). Five of the six animals recovered uneventfully from the procedure, and their foley catheters were removed 10-14 days postoperatively after a retrograde cystourethrogram demonstrated an intact vesicourethral anastomosis. Four (80%) of the surviving animals were clinically continent within 10 days after catheter removal. Post mortem examination confirmed that the vesicourethral anastomosis was intact with no evidence of urine extravasation. These data demonstrate the feasibility of laparoscopic radical prostatectomy in a canine model, and suggest that additional work with this technique should be continued to develop its potential clinical application.

Animals↗
PubMed1996

Struvite calculi.

Although calcium oxalate stones are the most common type of calculi found in the United States, struvite or infection stones are quite common and generally pose a difficult treatment dilemma. The presence of urinary infection with a urease-producing organism is necessary for these stones to form. Proteus species account for the majority of infections that cause struvite stones in all age ranges. However, other organisms also produce urease and may be detected in conjunction with struvite calculi. Factors that may predispose one to urinary tract infections increase the likelihood of struvite stone formation. Several options are available for the treatment of existing struvite calculi. Smaller stones may be treated with primary shock-wave lithotripsy, whereas larger stones are more appropriately managed with percutaneous or combination procedures. Medical therapy to prevent recurrent stone formation is also an essential part of the treatment of these patients, as the risk of stone recurrence is extremely high. Antibiotic therapy and urease inhibitors perhaps offer the best form of preventative treatment available today.

Anti-Bacterial Agents↗
PubMed1995

Three-dimensional video imaging for endoscopic surgery.

Recently a number of manufacturers have developed three-dimensional (3-D) video systems which significantly improve visualization and enhance the ability of the surgeon to perform delicate endoscopic dissection and suturing. These 3-D video systems may also improve the education of surgeons-in-training as they would have a better understanding of three-dimensional anatomy during laparoscopic surgery. Most of the 3-dimensional stereoendoscopic video systems currently available have four basic principles of stereoendoscopic image processing in common: image capture, conversion of 60-120 Hz images; presentation of left and right images on a single monitor; and separation of the left and right eye images. Skill tests performed assessing laparoscopic suturing and knot tying have demonstrated a 25% increase in speed and accuracy of these laparoscopic tasks when utilizing a three-dimensional video imaging greatly facilitates the efficiency of endoscopic reconstructive procedures. While three-dimensional video imaging systems are more costly than conventional two-dimensional video equipment, the enhanced depth perception produced by 3-D endoscopes has been demonstrated to improve the performance of minimally invasive surgical procedures.

Endoscopes↗
PubMed1995

Clinical and biochemical presentation of gouty diathesis: comparison of uric acid versus pure calcium stone formation.

PURPOSE: We compared gouty diathesis with uric acid versus calcium stones. MATERIALS AND METHODS: We retrospectively reviewed clinical and laboratory data from 95 gouty diathesis patients (28 with uric acid and 67 with calcium stones) and 99 normal subjects. RESULTS: Of the gouty diathesis patients gouty arthritis was present in 21% of those with uric acid and 12% of those with calcium stones. Hyperuricemia developed in 43% of those with uric acid and 27% of those with calcium stones, and 2% of controls. Urinary pH was independent of the net gastrointestinal absorption of alkali in the gouty diathesis groups. Urinary pH and citrate increased after potassium citrate treatment. CONCLUSIONS: The characteristic features of primary gout were present in both gouty diathesis groups and both are responsive to treatment.

Adult↗