Holmium-yttrium Aluminum Garnet Research Articles

Safety Parameters for the Use of Holmium:YAG Laser in the Treatment of Biliary Calculi: The Ex-Vivo Model.

Background and Objectives: While studies have demonstrated the efficacy of cholangioscopy-guided Holmium-Yttrium aluminum garnet (Ho:YAG) laser lithotripsy for the treatment of refractory bile duct stones, data regarding the safety of the operating parameters for laser lithotripsy are lacking. The aim of this study was to determine safe, yet effective, energy settings for Ho:YAG laser in the ex-vivo model. Materials and Methods: This ex vivo experimental study utilized the Ho:YAG laser on porcine bile duct epithelium and human gallstones. Ho:YAG laser lithotripsy was applied in different power settings from 8 to 15 Watts (W) to six explanted porcine bile ducts. Settings that appeared safe were then utilized to fragment seventy-three human gallstones. Results: The median bile duct perforation times with the Ho:YAG laser between 8-15 W were: >60 s (8 W); 23 s (9 W); 29 s (10 W); 27 s (12 W); 12 s (14 W); and 8 s (15 W). Statistically significant differences in the median perforation times were noted between 8 W vs. 15 W, 9 W vs. 15 W, 10 W vs. 15 W, and 12 W vs. 15 W (p < 0.05). When using a 365 µm Ho:YAG laser probe at 8-12 W, the fragmentation rates on various size stones were: 100% (<1.5 cm); 80-100% (1.6-2.0 cm) and 0-32% (>2.0 cm). Optimal fragmentation was seen utilizing 12 W with high energy (2.4 J) and low frequency (5 Hz) settings. Using a larger 550 µm probe at these settings resulted in 100% fragmentation of stones larger than 2 cm. Conclusions: The Ho:YAG laser appears to be safe and effective in the treatment of large bile duct stones when used between 8-12 W in 5 s bursts in an ex vivo model utilizing porcine bile ducts and human gallstones.

Analytical solution of heat-transfer in central part of tibia bone tissue using non-Fourier heat equation with a laser heat source

Hyperbolic heat transfer equation considering a laser heat source is analytically investigated using Laplace transform method to study the temperature distribution in the central part of the tibia bone tissue. The target zone is the compact layer of tibia, and the laser irradiation in four near-surface points during 2 s is taken into account. Holmium–Yttrium–Aluminum-Garnet (Ho-YAG) laser is utilized in the simulations. Results indicate that there is a trilateral relationship among the temperature changes of various points in the tissue, the power used and the wavelength. While neglecting the effects of blood circulation upon laser interaction with the bone surface, the results reveal that the temperature of the points adjacent to the bone surface dramatically increases up to 85 °C. Meanwhile, the heat source is provided based on the Beer-Lambert law, and finally it demonstrates that the penetration depth exponentially reduces the intensity and causing considerable decrease in temperature. For the first time, the non-Fourier heat transfer equation was solved using the Laplace transform method for the tibia bone, and its results were compared with the numerical solution results using the Leap- Frog method. Knowing the temperature changes caused by laser inside the tissue is very crucial in Laser tissue welding, tissue ablation, photocoagulation and photo-thermal denaturation, angioplasty, treatment of granulation tissues, change and deformation of cartilage.

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&lt;0.05). A reduced lithotripsy activation period of 30.8±3.7mins was associated with stone size (p&lt;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.

Holmium:YAG Laser for the Treatment of Genital and urethral Warts: Multicentre Prospective Evaluation of Safety and Efficacy.

Introduction: Genital condylomatosis is a highly contagious disease caused by the human papilloma virus (HPV). The aim of this prospective multicentre study was to evaluate the safety and efficacy of the Holmium:YAG (yttrium-aluminium-garnet) laser in the treatment of genital and intra-urethral warts; the secondary aim was to assess the patients' postoperative satisfaction and cosmetic results. Methods: From December 2016 to March 2019, patients with genital warts were prospectively enrolled in three hospitals. The inclusion criteria were male gender, age over 18 years-old and treatment-naïve. External and urethral genitalia warts were treated by the Holmium YAG laser. The follow-up analysis consisted of physical examination, flexible urethro-cystoscopy in case of meatal lesions, and administration of Dermatology Quality of Life Index (DLQI) and Patient Global Impression of Improvement (PGI-I) questionnaires at 1, 3, 6 and 12 months after surgery and subsequently yearly. Results: Sixty patients were enrolled. The single treatment was effective in 57/60 patients (95%). At a mean follow-up of 26 months, recurrences occurred in 8 patients (13.3%). No peri- or post-operative complication occurred. An improvement in pre-operative condition was highlighted with PGI-I and DLQI questionnaires. Conclusion: Our prospective multicentre study showed that holmium laser surgery seems to be a safe and effective treatment for external genital and urethral warts. Good dermatological outcomes aid to further improve patient satisfaction.

Feasibility and long-term safety of Ho:YAG laser lithotripsy in broncholithiasis patients

BackgroundTreatment of broncholithiasis is complex, especially in the case of a large or transbronchial broncholith. Holmium-yttrium aluminum garnet (Ho:YAG) laser lithotripsy may be a useful treatment in broncholithiasis; however, as it is not yet common practice, the optimal parameters are unknown.MethodsWe performed a single-center retrospective analysis of the clinical data of 13 broncholithiasis patients who underwent Ho:YAG laser lithotripsy from May 2012 to October 2018.ResultsFor the 13 patients (2 males and 11 females), Ho:YAG laser lithotripsy was performed 17 times, in total. All procedures were performed under general anesthesia with rigid bronchoscopy. We initially set the Ho:YAG laser to a pulse frequency of 5 Hz and a pulse energy of 0.8 J, gradually increasing these as required. The pulse frequency range we employed was 5–15 Hz, and the pulse energy range was 0.8–1.6 J. All broncholiths were successfully extracted after lithotripsy, and all symptoms improved. Hemoptysis, bronchial esophageal fistula, and pneumonia were the most common complications; however, there were no long-term complications.ConclusionsHo:YAG laser lithotripsy is an effective and safe treatment for broncholithiasis, over a long-term follow up.

Advanced application of holmium: YAG laser combined ALA-PDT for the treatment of refractory condylomata acuminata in anal canal.

Anal canal condylomata acuminata is a disease caused by the human papilloma virus. Conventional cauterizing laser treatment cannot achieve a satisfactory result owing to a high recurrence rate, and the application of 5-aminolaevulinic acid-photodynamic therapy (ALA-PDT) also has limitations in the anal canal. Holmium yttrium aluminum garnet (Ho: YAG) laser with fiber is found to be effective at removing canal lesions, and may create suitable conditions for ALA-PDT. We aim to investigate the feasibility of Ho: YAG laser combined with ALA-PDT and to explore a more optimal therapy in refractory anal canal condylomata. Data of 37 patients with anal canal condylomata (number of warts≥ 10 lesions) from May 2017 to March 2019 were reviewed. In total 17 cases were treated with Ho: YAG laser plus ALA-PDT, and 20 patients treated with CO2 laser plus ALA-PDT were selected as control. Wart clearance and recurrence rates were evaluated as well as laser complications. Most warts (88.23 %) were removed after a session of Ho: YAG laser pretreatment. The average number of laser sessions required to clear all warts was 1.94 in the Ho: YAG laser plus ALA-PDT group. Meanwhile, no wound infections or defecation disfunctions were found. Ho: YAG laser with ALA-PDT could significantly reduce wart recurrence rates (17.6 %) in comparison with CO2 laser with ALA-PDT (55 %). Ho: YAG laser combined with ALA-PDT raised the cure rate of refractory anal canal condylomata and has important guidance implications for clinical application.

Determining the correlation between transition zone index with international prostate symptom score and peak flow rate on clinical outcome after transurethral resection of the prostate in benign prostatic hyperplasia

Background: Benign prostatic hyperplasia (BPH) is a pathologic process which has common contribution to lower urinary tract symptoms (LUTS) in aging men. International Prostate Symptom Score (IPSS) is an important means of assesment in the clinical research of LUTS and BPH. Free flow rates (peak flow rate or Qmax) give an indirect measure for the probability of obstruction whereas subvesical obstruction only can be measured by invasive pressure-flow studies. Among the various surgical or minimally invasive techniques available for BPH like Intraprostatic stents (temporary/permanent), transurethral needle ablation (TUNA), transurethral microwave thermotherapy (TUMT), transurethral electrovaporization of prostate (TUVP), Transurethral incision of prostate (TUIP), lasers (Nd: YAG (Neodymium-doped yttrium aluminium garnet), Ho: YAG (Holmium yttrium aluminium garnet), potassium titanyl phosphate (KTP), diode, thulium laser) etc, transurethral resection of the prostate (TURP) is a safe and effective procedure. Comparison of difference in the pre and postoperative ultrasonic prostatic volume with amount of tissue resected at operation has established the accuracy of the method. The aims of present study are to determine the correlation between transition zone index with international prostate symptom score (IPSS) and peak flow rate (Qmax) on clinical outcome after TURP in BPH patients.Methods: A prospective study was conducted to determine the effect of the extent of tissue resection on symptom improvement after TURP in men and to evaluate any potential correlation between prostate size and outcome.Results: Total of 52 patients studied prospectively. Transitional zone (TZ) index was found to have a significant correlation with the clinical outcome.Conclusions: Symptomatic improvement after TURP will depend on the amount of tissue resected in terms of IPSS and peak flow rates.

Long-Term Prospective Outcomes of Patients with Non-Muscle Invasive Bladder Cancer After Holmium Laser Ablation.

Objectives: To evaluate the long-term tumor recurrence, progression, and cancer-specific mortality (CSM) of patients after holmium laser ablation of non-muscle invasive bladder cancer (NMIBC) under topical anesthesia. To identify variables that help to predict risk of tumor recurrence, progression, and CSM. Materials and Methods: A prospective study of 251 consecutive patients with 399 recurrent NMIBC who underwent outpatient Holmium yttrium aluminium garnet laser ablation under topical anesthesia was carried out between September 2006 and September 2018. All patients underwent primary transurethral resection of bladder tumor to obtain histology. All patients completed a patient satisfaction questionnaire and visual analogue scale (VAS) for procedure-related pain. Results: All 251 patients were analyzed with an average age of 75.2 years and follow-up of 69.8 months. The majority of patients had multiple comorbidities with an American Society of Anesthesiologists of 3 or 4. The proportion of tumor grade 1, 2, and 3 disease and tumor stage Ta and T1 was 43.4%, 41.5%, 15.1%, 78.5%, and 21.5%, respectively. Overall, 57.8% of patients had at least one tumor recurrence with an average time of 16.3 months. Risk factors were tumor grade, number of tumors at time of first laser ablation, and tumor stage. Overall, 19.1% of patients demonstrated tumor progression with an average time of 51 months. Only 5.6% of patients had progression to muscle invasive bladder cancer, and the CSM rate was 5.2% with an average time to death of 71.2 months. Risk factors for CSM were tumor grade, stage, and the patient's age. The average VAS for pain was 0.6 out of 10, with all patients willing to have the procedure repeated if required. Conclusion: Laser ablation of NMIBC is a safe, effective, and well-tolerated long-term option for patients, particular in those who have moderate-to-severe co-morbidities. The long-term cancer outcomes are best for younger patients with primary low-grade and low-stage disease.

Vaporizing Effect of the Popcorn Technique for Laser Lithotripsy: Comparing the Different Settings of High Energy in a Caliceal Model.

Objective: To assess the effectiveness of laser lithotripsy in different holmium:yttrium aluminum garnet (Ho-YAG) laser settings with a wide range of energies, frequencies, and power. Materials and Methods: Two types of phantom stones were utilized, including soft stone, which mimics uric acid stone, and hard stone, which mimics calcium oxalate monohydrate stone. The stones were made into a round shape measuring 10 mm in diameter. The lithotripsy settings were 1 J × 20 Hz, 2 J × 10 Hz, 1.5 J × 20 Hz, 3 J × 10 Hz, and 2 J × 20 Hz. The lithotripsy was conducted in a caliceal model with a 2-mm filter. All stone vanishing from the artificial calix was an end point of the experiment. All fragments that passed through the filter of each setting were dried and weighed to calculate the vaporizing effect as well as to compare among the different settings. Laser fiber degradation was compared by using these settings. Results: Disintegration efficiency was determined by time consumption and the amount of vaporized stone. The best time consumption was 8 min 51 sec for 2 J × 20 Hz for hard stone and 5 min 13 sec for this setting for soft stone. The most vaporizing effect for hard stone was 92.19% for 2 J × 20 Hz and 87.30% for this setting for soft stone. The most fiber tip degradation was 28 mm for 3 J × 10 Hz for hard stone and 4 mm for 1.5 J × 20 Hz for soft stone. Conclusion: The study revealed that the best setting for hard stone was 2 J × 20 Hz, which was the fastest for achieving maximum vaporization, whereas fiber degeneration was comparable to others. For soft stone, there was no difference among the settings.

Foreign Body Stones in the Urinary Bladder of Two Children

Bladder calculi rarelyseen in children and are usually a manifestation of an underlying pathologic condition of the lower urinary tract, metabolic disease, voiding dysfunction, urinary infection, obstruction, or foreign body retention. However, a forgotten double j stent and a ruptured Foley balloon-induced bladder stone are an unusual complication for children. We report two case of bladder stone induced by a fragment of a ruptured Foley balloon and forgotten double j stent . The bladder stone and balloon fragment and stent were successfully removed by cystoscopy by using a holmium:yttrium–aluminum-garnet (Ho-YAG) laser lithotripter

Prospective Analysis of a Complete Retrograde Ureteroscopic Technique with Holmium Laser Stent Cutting for Management of Encrusted Ureteral Stents.

Purpose: To propose and evaluate a new endoscopic technique using only a retrograde ureteroscopic approach for the removal of heavily encrusted ureteral stents. Methods: Data from 51 consecutive patients with encrusted and retained ureteral stents were prospectively collected. Description of the successive steps of surgery is detailed. The holmium yttrium aluminum garnet (Ho:YAG) laser properties offer the opportunity for fragmentation of stent-attached encrustation and the ability to cut the stent itself. Reducing the length of the stent is critical to creating space in the ureter and to allow free access for ureteroscopes or ureteral access sheath placement. The primary outcome of this study was the feasibility and the safety of this retrograde intrarenal approach. Some factors of encrustation and outcomes are also discussed in comparison with lithotripsy, percutaneous, laparoscopic, open surgery, or a combination of these techniques. Results: The removal of the encrusted stent was possible with only this retrograde technique in 98% of patients. The transection of the encrusted stent with the Ho:YAG laser was useful in 71% of the patients. Mean operative time was 110 minutes and mean hospital stay was 2.33 days. Postoperative complications were mainly nonobstructive pyelonephritis (10%). The most significant predictor of this life-threatening complication was the presence of struvite stones with the encrusted stent (p = 0.018). Contrariwise, operative time, body mass index, gender, and encrustation rate were not associated with postoperative pyelonephritis. Both cystine stone disease and pregnancy led to faster stent encrustation. Conclusions: Retrograde ureteroscopic surgery is efficient and safe for removing retained stents and associated stone burdens. The Ho:YAG laser is essential to perform the encrustation removal and sectioning of the stent.

Ultrasound-guided micropercutaneous nephrolithotomy in pediatric patients with kidney stones.

To present the outcomes of ultrasound-guided micropercutaneous nephrolithotomy for the treatment of renal stones in pediatric patients. Ultrasound-guided micropercutaneous nephrolithotomy was carried out on 25 pediatric patients from June 2012 to October 2014. Micropercutaneous nephrolithotomy surgery was completed without the use of fluoroscopy in 19 patients. Medical records were retrieved from our institutional database and retrospectively reviewed. Percutaneous puncture was carried out by an "all-seeing needle" in seven patients and by a 14-G intravenous cannula in 18 patients. After entering to the collecting system through an "all-seeing needle" or by Microsheath, the calculus was fragmented using a 273-micron holmium yttrium aluminium garnet laser. After the stone was fragmented to the smallest pieces possible, the operation was terminated. Single access was obtained in all patients using ultrasound guidance. The average age of the patients was 4.12 ± 5.33 years. The mean stone size was 13.45 ± 3.11 mm. The mean operative time was 51.45 ± 30.69 min. The mean duration of hospitalization was 3.18 ± 1.77 days. Treatment success was 92%. Two patients had residual fragments after the procedure; these patients were followed conservatively. A total of three minor complications were observed and all of them were managed conservatively. To our knowledge, this is the first study of ultrasound-guided micropercutaneous nephrolithotomy in the pediatric population. Our findings suggest that micropercutaneous nephrolithotomy can be safely carried out with ultrasound guidance in children by experienced hands, allowing to minimize risks associated with radiation exposure in this patient population.

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.

Use of the holmium yttrium aluminum garnet laser for percutaneous ablation of thoracolumbar discs in dogs: A historical summary

AbstractPercutaneous holmium yttrium aluminum garnet (Ho:YAG) laser ablation of the nucleus pulposus of thoracolumbar discs in dogs as a prophylactic procedure for prevention of catastrophic intervertebral disc protrusion/extrusion has been utilized at Oklahoma State University Center for Veterinary Health Sciences (CVHS) since 1992. Over 400 animals have been treated using percutaneous laser disc ablation (PLDA) with minimal post-treatment complications and a decreased rate of neurologic recurrence. The purpose of this summary is to provide a brief historical background of this minimally invasive procedure as well as its current status in clinical practice in the USA.

Laser welding of vesicovaginal fistula—outcome analysis and long-term outcome: single-centre experience

The aim of this study is to evaluate the efficacy and safety of laser welding of vesicovaginal fistula (VVF) at our centre. Between January 1, 2001 and January 3, 2010, eight patients underwent laser welding of vesicovaginal fistula. The mean age was 44 years (35-55). The VVF were primary (failing to heal following conservative management) in five and secondary (recurring following primary repair) in three cases. The mean fistula size was 3 mm (range, 2-4). Neodymium yttrium aluminium garnet (YAG) laser was used for the initial case, and in the remaining seven cases, holmium YAG laser was used for circumferential welding of the fistula. Following the procedure, a catheter was kept for 3 weeks. The mean hospitalisation period was 1 day. The mean follow-up is 47 months (2-110). Seven patients were dry after catheter removal. In one patient, procedure was abandoned due to bleeding. Laser welding of VVF is a simple, safe and efficacious procedure in a select group of patients.

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.

Application of holmium yttrium aluminium garnet (YAG) laser in treatment of acquired posterior choanal atresia following radiotherapy for nasopharyngeal carcinoma

To report on the use of holmium yttrium aluminium garnet (YAG) laser in the treatment of acquired posterior choanal atresia following radiotherapy in patients with nasopharyngeal carcinoma. Five patients with acquired bilateral choanal atresia and two with unilateral choanal atresia in the posterior choanae were identified following treatment of nasopharyngeal carcinoma by external radiotherapy, from July 1998 to April 1999. The mean age was 44.6 years (range, 22-65 years). Two patients had stage two and five had stage three disease according to Ho's classification. All patients received 66 Gy of external irradiation delivered to the nasopharynx and a mean dose of 61 Gy (39.8-72 Gy) to the neck. Five patients received an additional external boost of 20 Gy and two received 14 Gy delivered to the parapharyngeal region. Two other patients also received intracavitatory brachytherapy of 18 Gy delivered to the nasopharynx. One patient had concurrent chemotherapy by cisplatinum during external radiotherapy. The mean onset of nasal symptoms was 17 months (range, 2-38 months) following irradiation. All patients were treated by transnasal endoscopic holmium YAG laser resection. Merocel epistaxis packing and a modified nasopharyngeal tube were used to stent the nasal airway for two weeks post-operatively. The mean follow up was 26.8 months (range, 20-32 months) after surgery. All patients were symptom free on follow up. Five patients (71 per cent) retained full patency in the posterior choanae. Two patients (28 per cent) had bilateral mild restenosis in the postnasal space, not requiring revision surgery. The surgical fields were almost bloodless. No adverse post-operative complications occurred, except for delayed nasal septal perforation in one patient and unilateral exposure of the septal cartilage in another; no further treatment was required in either patient. Acquired posterior choanal atresia is an unusual complication following radiotherapy, and it can occur early after treatment. It can be successfully treated by transnasal endoscopic holmium YAG laser resection of the scar tissue, with minimal bleeding. A two week period of Merocel nasal packing and nasopharyngeal tube stenting was sufficient to prevent severe restenosis in the posterior choanae; nasal breathing through the tube lumen was possible during this time.

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.