Holmium-yttrium Aluminum Garnet Laser Research Articles

Comparing Holmium (Ho): YAG Laser with Pneumatic Lithoclast for Treatment Efficacy of Ureteric Stones

ABSTRACT Background: Holmium YAG (yttrium-aluminum-garnet) laser, a comparatively new technique, can clear all types and sizes of stones and is only being used in two institutes of Karachi, Pakistan. The study aimed to compare pneumatic lithoclast and holmium YAG laser, to evaluate stone-free rate (SFR), postoperative complications, operative duration, and effectiveness. Methods: This cross-sectional research included 60 patients with age 16-65 years having ureteric stones, reporting to kidney center, Urology Department, Karachi, Pakistan. CT Scan of Kidneys, Ureter, and Bladder (KUB) were used to record stone size, laterality, and location within the ureter. Patients were divided into two clusters of 30 each, group A (Ho: YAG laser) and group B (pneumatic Lithoclast) having 0.5 to 02 cm of size ureteric stones. An Independent two-sample “t” test was used to assess the difference for the continuous variables. A p-value of ≤0.05 was considered statistically significant. Results: Stone sizes distribution was 1.3±0.3cms and 1.4±0.3cms for A and B groups respectively (p=0.8). The insignificance of the p-value demonstrated no substantial divergence between both groups and stone sizes. Clearance from the proximal ureter was noted 26(84.6%) in group A and 41.7% in group B with (p<0.05). A reduced lithotripsy activation period of 30.8±3.7mins was associated with stone size (p<0.05). Conclusion: Holmium: YAG Laser had better stone-free rate (SFR), with 84% clearance than pneumatic. Improved and effective clearance reduces the risk of residual stones within a lesser time, required for getting back to normal life routines. Keywords: Lasers; Ureteric Stones; Ho: YAG Laser; Pneumatic Lithoclast; Kidney Stones.

The use of ureteral access sheath during mini-percutaneous nephrolithotomy with high-power holmium YAG laser.

To present our preliminary results and describe a technical modification of mini-PCNL (12Fr) with the insertion of a ureteral access sheath (UAS) to facilitate the procedure. A prospective study for the time period of January 2020 to January 2021 was conducted including patients with renal stones sized ≤ 25mm in whom prone mini-PCNL (tract size 12Fr) together with the retrograde insertion of UAS was performed. All patients had been prestented at least 1week prior to the planned surgery. A single-step tract dilation to 12Fr diameter was performed through a nonpapillary medial puncture. The lithotripsy was achieved using high-power holmium yttrium aluminum garnet laser (Ho:YAG) with the 60W power setting (40Hz and 1.5J). The follow-up investigations were planned at 1-month after the surgery. In total, 32 patients with the median age and stone size of 56.5 (IQR = 53-62) years and 20.8 (IQR = 19.3-22.7) mm were included. The median operative and cumulative fluoroscopy time were 34.0 (IQR = 29.9-37.5) and 1.9 (1.8-2.1) min, respectively. The stone-free rate (SFR) at 1-month follow-up was 93.8% (30/32). Only one patient developed a fever and required prolonged antibiotic administration. None of the patients experienced clinically significant bleeding. Our preliminary results showed that the use of UASs during mini-PCNL procedures is feasible and provides directed evacuation of the stone fragments reaching 93.8% SFR at a 1-month follow-up. Future well-designed studies are necessary to prove our findings.

Outcome of Rirs for Renal Pelvic Stones 1.5 to 2.0 cm using Semi-Rigid Uretero-Renoscopy

Background Retrograde Intrarenal Surgery (RIRS) is among the recommended treatment modality for stones located in renal pelvis and is of less than 2 cm. Renal Stones with Hounsfield units more than 1000 have low stone free rate with ESWL. Objective To determine the outcome of retrograde intrarenal surgery using semirigid ureteroscope in fragmentation of renal pelvic stone. Methods Patients with 1.5-2.0 cm stone located in renal pelvis of more than 1000 HU who underwent retrograde intrarenal surgery as primary procedure at Sindh Institute of Urology And Transplantation were included. Stone fragmentation was achieved with holmium-yttrium aluminum garnet laser. Secondary procedure was performed if complete stone fragmentation was not achieved. Statistical analysis was performed by SPSS version 20. Result Total 82 patients with mean size of pelvic renal stones 1.7 ± 0.53 cm were included. The mean operating time was 32.1±12.9 mins. The stone clearance rate at six weeks after the first procedure was 79.3%. Minor complications including flank pain, fever and hematuria were reported. Conclusion Retrograde intrarenal surgery performed with semi rigid ureteroscope in renal pelvic stones of more than 1000 HU is a technically safe and effective procedure. Keywords: Retrograde intrarenal surgery; Pelvic stone; Flexible ureteroscopy and holmium laser.

Percutaneous yttrium aluminum garnet-laser lithotripsy of intrahepatic stones and casts after liver transplantation.

Bile duct stones and casts (BDSs) contribute importantly to morbidity after liver transplantation (LT). The purpose of this study was to estimate the clinical efficacy, safety, and long-term results of percutaneous transhepatic cholangioscopic lithotripsy (PTCSL) in transplant recipients and to discuss underlying factors affecting the outcome. A retrospective chart review revealed 18 recipients with BDSs treated by PTCSL laser lithotripsy with a holmium-yttrium aluminum garnet laser probe at 365 to 550 µm. They were analyzed in a median follow-up time of 55 months. In all but 1 patient (17/18 or 94%), it was technically feasible to clear all BDSs with a mean of 1.3 sessions. PTCSL was unsuccessful in 1 patient because of multiple stones impacting the bile ducts bilaterally; 17% had early complications (Clavien II). All biliary casts were successfully cleared; 39% had total remission; 61% needed additional interventions in the form of percutaneous transhepatic cholangiography and dilation (17%), re-PTCSL (11%), self-expandable metallic stents (22%), or hepaticojejunostomy (6%); and 22% eventually underwent retransplantation. The overall liver graft survival rate was 78%. Two patients died during follow-up for reasons not related to their BDS. Nonanastomotic strictures (NASs) were significantly associated with treatment failure. We conclude that PTCSL in LT patients is safe and feasible. NASs significantly increased the risk of relapse. Repeated minimally invasive treatments, however, prevented graft failure in 78% of the cases.

The use of holmium-yttrium aluminum garnet laser as pit and fissure cleaner

Background: The prevention and management of pit and fissure caries has become relatively more important in recent times. There is a need for an effective preventive measure against pit and fissure caries. Purpose: The purpose of this study was to investigate the effect of laser beam as a cleaning method of pits and fissures. Methods: Ho-YAG laser which has a wavelength of 2.1 µm was used in this experiment. The specimens were extracted human teeth. The effect of three cleaning methods was examined comparatively by scoring the cleaned area of fissure, namely laser irradiation with Ho-YAG laser, chemico-mechanical with combination of 10% NaOCl and ultrasonic scaler and mechanical with ultrasonic scaler. Vertico-bucco-lingual serial ground sections of each tooth were observed under light microscopy. Scoring the depth of cleaned area was performed by comparing the depth of fissure. result: Progressive result was obtained on the cleaning effect of three methods laser irradiation methods which was the most effective compared to other methods but statistically was not significant. Cleaned area of laser irradiation method was 48.91%, chemico-mechanical method was 41.77% and mechanical method was 36.78%. Conclusion: Holmium -yttrium aluminum garner laser is a relatively new method for pit and fissure cleaning even though the effectivity is not yet maximal. More research is needed to maximize the use of this laser.

Assessment of Cellular Response to Thermal Laser Injury Through Bioluminescence Imaging of Heat Shock Protein 70¶†

Assessment of laser-induced tissue damage is not complete without an investigation into the resulting cellular and molecular changes. In the past, tissue damage was quantified macroscopically by visual effects such as tissue mass removal, carbonization and melting. Microscopically, assessment of tissue damage has been typically limited to histological analysis of excised tissue samples. In this research, we used heat shock protein (hsp70) transcription to track cellular response to laser-induced injury. A stable cell line (NIH-3T3) was generated containing the firefly luciferase (luc) reporter gene attached to the hsp promoter (murine hsp70a1). After thermal injury with a pulsed holmium-yttrium aluminum garnet laser (lambda = 2.1 microm, taup = 250 micros, 30 pulses, 3 Hz), luciferase is produced on hsp70 activation and emits broad-spectrum bioluminescence over a range of 500-700 nm, with a peak at 563 nm. The onset of bioluminescence can be seen as early as 2 h after treatment and usually peaks at 8-12 h depending on the severity of heat shock. The luminescence was quantified in live cells using bioluminescence imaging. A minimum pulse energy (65 mJ/pulse [total energy 1.95 J; total radiant exposure = 6 J/cm2]) was needed to activate the hsp70 response, and a higher energy (103 mJ/pulse [total energy 3.09 J; total radiant exposure = 9.6 J/cm2]) was associated with a reduction in hsp70 response and cell death. Bioluminescence levels correlated well with actual hsp70 protein concentrations as determined by enzyme-linked immunosorbent assay. Photon counts were normalized to the percentage of live cells by means of a flow cytometry cell viability assay. Within a relatively small range between a lower activation threshold and an upper threshold that leads to cell death, the hsp70 response followed an Arrhenius relationship when constant-temperature water bath and laser experiments were carried out.

Use of the holmium yttrium aluminum garnet laser for percutaneous thoracolumbar intervertebral disk ablation in dogs

Objective To evaluate a laser ablation technique for treatment of thoracolumbar intervertebral disk disease in dogs. Design Prospective case series. Animals 33 dogs with signs of recurrent back pain associated with intervertebral disk disease after the initial episode had been managed conservatively for a minimum of 2 weeks. Procedure Spinal needles were placed percutaneously through the annulus fibroses to permit delivery of an optical fiber into the nucleus pulposes of thoracolumbar intervertebral disks T10-11 through L3-4. Fluoroscopy was used to guide needle placement. Holmium yttrium aluminum garnet laser energy then was used to ablate the contents of each selected intervertebral disk. Intervals from time of treatment to time of assessment ranged from 3 to 114 weeks. Results All dogs recovered without complication. Results of follow-up radiography and histologic evaluation indicated that percutaneous holmium yttrium aluminum garnet laser ablation reduces the volume of nucleus pulposus in treated disks. Clinical Implications Used as a clinical treatment and prophylactically, this minimally invasive procedure should prevent further extrusion of partially herniated disks and should reduce the chances of subsequent herniation of disks at other treatment sites. (J Am Vet Med Assoc 1996;208:1263–1267)

Effects of pulsed lasers on agar model simulation of the arterial wall.

Coronary laser angioplasty is limited by a high rate of dissection and the occurrence of abrupt closure and perforation. The aim of this study was to visualize the mechanical effects of pulsed lasers on two chamber in vitro models. These models consisted of 1 or 2 agar layers and calcium carbonate inclusions (1-layer model) or lipid (2-layer model) simulating lipid or calcified tissue. The inclusions were irradiated with a holmium-yttrium-aluminum-garnet (Ho-YAG) laser or a xenon chloride excimer laser. The Ho-YAG laser demonstrated dissection-like expansions of the target and perforation-like cracks. The size of dissection was obtained using an the empirical formula of energy (E) and the maximal expansion distance (Dmax) of the targets, Dmax = 0.15E0,87-1,17. The excimer laser showed rare and short perforation-like cracks and little dissection-like expansion of the gaseous products originating from the ablation of material. Ho-YAG laser ablation is likely to induce target tissue dissections and/or perforations. Excimer laser-ablates targets with less traumatic effects than Ho-YAG laser.

Characteristics of shock waves induced by pulsed lasers and their effects on arterial tissue: Comparison of excimer, pulse dye, and holmium YAG lasers

Shock waves were investigated using an excimer laser at 308 nm with 18.9 mjoules/pulse, a pulsed dye laser at 480 nm with 100 mjoules/pulse, and a holmium YAG (yttrium-aluminum-garnet) laser at 2.1 μm with 420 mjoules/pulse. At a distance from the target tissue, excimer lasing resulted in no shock waves in saline, while the other lasers produced smaller shock waves than those recorded when the laser was in contact with tissue (0.22 versus 2.0 mm Hg with the pulsed dye laser, 0 versus 0.23 mm Hg with the excimer laser, and 0.44 versus 6.9 mm Hg with the holmium YAG laser; p < 0.001, respectively). In blood, excimer laser irradiation at a distance from the tissue produced shock waves as great as those produced when the laser was in contact with the tissue (0.19 versus 0.24 mm Hg with the excimer laser, 1.8 versus 3.0 mm Hg with the pulsed dye laser, and 3.1 versus 5.9 mm Hg with the holmium YAG laser; p < 0.001 with the pulsed dye and holmium YAG lasers, respectively). When lasing was done at 60 mjoules/mm 2, the pulsed dye and excimer lasers produced similar shock waves when the lasers were in contact with tissue; however, the holmium YAG laser did not produce shock waves. Thus pulsed lasers can produce shock waves of different characteristics according to the laser source.