To more clearly define the efficiency and potential benefits of variable pulse-width laser technology for ureteroscopic lithotripsy, we performed comparative in vitro evaluations assessing stone ...comminution, laser fiber tip degradation, and stone retropulsion.
All experiments were conducted using a Swiss LaserClast Holmium:YAG laser (Electro Medical Systems, Nyon, Switzerland) with adjustable pulse duration (300 µs-1500 µs). To assess comminution efficiency and fiber tip degradation, a "dusting" model was employed; the laser fiber tip was moved by a 3-dimensional positioning system in a spiral motion across a flat BegoStone surface submerged in water. Comminution efficiency was measured as the loss of stone mass while fiber tip degradation was measured simultaneously. The same laser and fiber were used in a pendulum model to measure stone retropulsion with a high-speed resolution camera.
In our dusting model, comminution was significantly greater at high energy (2 J/5 Hz). At the high energy setting, comminution was significantly greater with long pulse duration than short pulse, although this difference was not seen at the high frequency setting (1 J/10 Hz). Tip degradation was increased at high energy settings and was even more pronounced with short pulse duration than long pulse. Short pulse duration caused far more retropulsion than the long pulse setting.
In an in vitro dusting model, a longer laser pulse duration provides effective stone comminution with the advantage of reducing laser fiber tip degradation and stone retropulsion.
Summary Background People with type 2 diabetes are at risk of cognitive impairment and brain atrophy. We aimed to compare the effects on cognitive function and brain volume of intensive versus ...standard glycaemic control. Methods The Memory in Diabetes (MIND) study was done in 52 clinical sites in North America as part of Action to Control Cardiovascular Risk in Diabetes (ACCORD), a double two-by-two factorial parallel group randomised trial. Participants (aged 55–80 years) with type 2 diabetes, high glycated haemoglobin A1c (HbA1c ) concentrations (>7·5%; >58 mmol/mol), and a high risk of cardiovascular events were randomly assigned to receive intensive glycaemic control targeting HbA1c to less than 6·0% (42 mmol/mol) or a standard strategy targeting HbA1c to 7·0–7·9% (53–63 mmol/mol). Randomisation was via a centralised web-based system and treatment allocation was not masked from clinic staff or participants. We assessed our cognitive primary outcome, the Digit Symbol Substitution Test (DSST) score, at baseline and at 20 and 40 months. We assessed total brain volume (TBV), our primary brain structure outcome, with MRI at baseline and 40 months in a subset of participants. We included all participants with follow-up data in our primary analyses. In February, 2008, raised mortality risk led to the end of the intensive treatment and transition of those participants to standard treatment. We tested our cognitive function hypotheses with a mixed-effects model that incorporated information from both the 20 and 40 month outcome measures. We tested our MRI hypotheses with an ANCOVA model that included intracranial volume and factors used to stratify randomisation. This study is registered with ClinicalTrials.gov , number NCT00182910. Findings We consecutively enrolled 2977 patients (mean age 62·5 years; SD 5·8) who had been randomly assigned to treatment groups in the ACCORD study. Our primary cognitive analysis was of patients with a 20-month or 40-month DSST score: 1378 assigned to receive intensive treatment and 1416 assigned to receive standard treatment. Of the 614 patients with a baseline MRI, we included 230 assigned to receive intensive treatment and 273 assigned to receive standard treatment in our primary MRI analysis at 40 months. There was no significant treatment difference in mean 40-month DSST score (difference in mean 0·32, 95% CI −0·28 to 0·91; p=0·2997). The intensive-treatment group had a greater mean TBV than the standard-treatment group (4·62, 2·0 to 7·3; p=0·0007). Interpretation Although significant differences in TBV favoured the intensive treatment, cognitive outcomes were not different. Combined with the non-significant effects on other ACCORD outcomes, and increased mortality in participants in the intensive treatment group, our findings do not support the use of intensive therapy to reduce the adverse effects of diabetes on the brain in patients with similar characteristics to those of our participants. Funding US National Institute on Aging and US National Heart, Lung, and Blood Institute.
Ureteroscopic laser lithotripsy requires irrigation for adequate visualization and temperature control during treatment of ureteral stones. However, there are little data on how different irrigation ...and laser settings affect the ureteral wall and surrounding tissues. This effect has become an important consideration with the advent of high-powered lasers. We therefore evaluated the effect of laser settings and irrigation flow on ureteral temperature in an in vitro setting.
To mimic ureteroscopic laser lithotripsy, we simulated clinically relevant irrigation flow rates and fired a Holmium:Yttrium-aluminum-garnet (Ho:YAG) laser while monitoring "intraureteral" temperature. The probe tip of a thermometer was placed 1 mm from the tip of a 200 μm laser fiber, which was fired for 60 seconds at 0.2 J/50 Hz, 0.6 J/6 Hz, 0.8 J/8 Hz, 1 J/10 Hz, and 1 J/20 Hz within a tubing system that allowed for specified room temperature flow rates (100, 50, and 0 mL/minute). We recorded temperatures every 5 seconds. The maximum temperature was noted, and each laser/flow trial was duplicated. Averaged maximum temperatures were compared using analysis of variance across irrigation settings.
At 100 cc/minute, only the 1 J/20 Hz laser setting produced a significantly higher maximum temperature (p < 0.01), although this finding was not clinically significant at a maximum of 30.7°C. At a lower irrigation rate of 50 cc/minute, the 1 J/20 Hz setting was again the only significantly higher maximum temperature (p < 0.05), although this temperature crossed the toxic threshold at a maximum of 43.4°C. With no flow, all maximum temperatures reached over 43°C, with 0.8 J/8 Hz, 1 J/10 Hz, and 1 J/20 Hz each statistically higher than the lower-energy settings (p < 0.05). The maximum temperature at 1 J/20 Hz with no irrigation was over 100°C.
Despite increasing laser settings, adequate irrigation can maintain relatively stable temperatures within an in vitro ureteral system. As irrigation rates decrease, even lower power laser settings produce a clinically significant increase in maximum temperature, potentially causing ureteral tissue injury.
Office cystoscopy is one of the most frequently performed procedures by a urologist. However, single-use cystoscopes remain quite undeveloped. Ambu
has developed single-use broncoscopes, ...rhinolaryngoscopes, and duodenoscopes. Recently, they released a single-use cystoscope. In this study, we performed a benchtop and an initial clinical assessment of the Ambu aScope™ (4) Cysto (aS4C) single-use cystoscope.
Ten new, never-used aS4C single-use cystoscopes were assessed for optical performance, maximal tip flexion, and irrigation flow rate with empty working channel, 365 μm laser fiber, 0.035 in hydrophilic-tipped wire, 1.9F nitinol basket, and a 1.8 mm flexible stent grasper. All cystoscopes were then fully flexed 25 times in each direction, and maximal flexion angles were remeasured with and without instruments. Optical resolution, distortion, and depth of field were measured and compared with our reusable digital flexible cystoscopes. Assessment of clinical use was performed for inpatient bedside procedures using a Likert feedback survey and the NASA Task Load Index.
Maximal upward flexion exceeded 200° and 160° for all working instruments in upward and downward flexion. Downward flexion demonstrated different flexion between instrument groups in pre- and postcycling (
< 0.001). There was no clinical difference between the pre- and postcycling flexion. Flow rate decreased with increasing working instrument size (
< 0.001). The Olympus HD cystoscope resolution was superior at 3 and 5 mm distance, but not at other distances. The Ambu scope was superior to the Olympus SD scope at all distances except 3 mm. The aS4C had higher Likert scale survey scores for clinical use.
The new Ambu single-use cystoscope demonstrates good flexion across instruments and comparable optics with reusable cystoscopes. In addition, initial inpatient bedside use of the aS4C and Monitor system compares favorably with the Olympus reusable cystoscope. Further testing in clinical scenarios such as hematuria, urothelial carcinoma, and operative endoscopy is warranted.
Purpose There is rising concern over the increasing amount of patient radiation exposure from diagnostic imaging and medical procedures. Patients with nephrolithiasis are at potentially significant ...risk for radiation exposure due to the need for imaging to manage recurrent stone disease. We reviewed the literature in an attempt to better characterize actual risks and discussed methods to reduce radiation exposure for adult patients with nephrolithiasis. Materials and Methods A PubMed® search was performed using the key words nephrolithiasis, stones, radiation, fluoroscopy, ureteroscopy, percutaneous nephrolithotomy, computerized tomography and shock wave lithotripsy. Additional citations were identified by reviewing reference lists of pertinent articles. Results A total of 50 relevant articles were included in this review. Patients with a first time acute stone event are exposed to a significant amount of radiation. Most radiation is from computerized tomography. Patients undergoing percutaneous nephrolithotomy are exposed to an equal or greater amount of radiation than they received from computerized tomography. Risk factors for increased exposure during percutaneous nephrolithotomy include obesity, multiple tracts and a larger stone burden. Ureteroscopy exposes patients to approximately the same amount of radiation as plain x-ray of the kidneys, ureters and bladder. Risk factors for increased exposure during ureteroscopy include obesity and ureteral dilation. During shock wave lithotripsy the amount of radiation exposure is not well characterized. Interventions to reduce exposure to patients include using ultrasound when possible and implementing low dose computerized tomography protocols. The as low as reasonably achievable principle of radiation exposure should always be followed when fluoroscopy is performed. The use of an air retrograde pyelogram may also reduce exposure during percutaneous nephrolithotomy. Fluoroscopy time during ureteroscopy may be decreased by a laser guided C-arm, a dedicated C-arm technician, stent placement under direct vision and tactile feedback to help guide wire placement. Conclusions Patients with nephrolithiasis are at significant risk for increased radiation exposure from the imaging and fluoroscopy used during treatment. The true risks of low radiation exposure remain uncertain. It is important to be aware of these risks to provide better counseling for patients. Urologists must also be familiar with techniques to decrease radiation exposure for patients with nephrolithiasis.
To investigate the mechanism of stone dusting in Holmium (Ho): YAG laser lithotripsy (LL).
Cylindrical BegoStone samples (6 × 6 mm, H × D) were treated in water using a clinical Ho:YAG laser ...lithotripter in dusting mode (0.2-0.4 J with 70-78 μs in pulse duration, 20 Hz) at various fiber tip to stone standoff distances (SD = 0, 0.5, and 1 mm). Stone damage craters were quantified by optical coherence tomography and bubble dynamics were captured by high-speed video imaging. To differentiate the contribution of cavitation
thermal ablation to stone damage, three additional experiments were performed. First, presoaked wet stones were treated in air to assess stone damage without cavitation. Second, the laser fiber was advanced at various offset distances (OSD = 0.25, 1, 2, 3, and 10 mm) from the tip of a flexible ureteroscope to alter the dynamics of bubble collapse. Third, stones were treated with parallel fiber to minimize photothermal damage while isolating the contribution of cavitation to stone damage.
Treatment in water resulted in 2.5- to 90-fold increase in stone damage compared with those produced in air where thermal ablation dominates. With the fiber tip placed at OSD = 0.25 mm, the collapse of the bubble was distracted away from the stone surface by the ureteroscope tip, leading to significantly reduced stone damage compared with treatment without the scope or with scope at large OSD of 3-10 mm. The average crater volume produced by parallel fiber orientation at 0.2 J after 100 pulses, where cavitation is the dominant mechanism of stone damage, was comparable with those produced by using perpendicular fiber orientation within SD = 0.25-1 mm.
Cavitation plays a dominant role over photothermal ablation in stone dusting during short pulse Ho:YAG LL when 10 or more pulses are delivered to the same location.
Low energy and high frequency settings are used in stone dusting for holmium lasers. Such settings may not be optimal for thulium fiber laser (TFL). With the seemingly endless combination of ...settings, we aim to provide guidance to the practicing urologists and assess the efficiency of the TFL platform in an automated
"dusting model."
Three experimental setups were designed to investigate stone dusting produced by an IPG Photonics TLR-50 W TFL system using 200 μm fiber and soft BegoStone phantoms. The most popular 10 and 20 W dusting settings among endourologist familiar with TFL were evaluated. We directly compared short pulse (SP)
long pulse (LP) mode using various combinations of pulse energy (E
) and pulse frequency (F). Thereafter, we tested the 10 and 20 W settings and compared them among each other to elucidate the most efficient settings at each power. Treatments were performed under the same total laser energy delivered to the stone at four different standoff distances (SDs) with a clinically relevant scanning speed of either 1 or 2 mm/sec. Ablation volumes were quantified by optical coherence tomography to assess stone dusting efficiency. Fragment size after ablation at different pulse energies was evaluated by sieving and evaluating under a microscope after treatment.
Overall, SP provided greater ablation volume when compared with LP. Our dusting efficiency model demonstrated that the maximum stone ablation was achieved at the combination of high energy/low frequency settings (
< 0.005) and at a SD of 0.2 mm. At all tested pulse energies, no stone phantoms were broken into fragments >1 mm.
During stone dusting with TFL, SP offers superior ablation to LP settings. Optimal dusting at clinically relevant scanning speeds of 1 and 2 mm/sec occurs at high energy/low frequency settings. Thulium lithotripsy with high E
does not result in increased fragment size.
Objectives
To explore the optimal laser settings and treatment strategies for thulium fibre laser (TFL) lithotripsy, namely, those with the highest treatment efficiency, lowest thermal injury risk, ...and shortest procedure time.
Materials and Methods
An in vitro kidney model was used to assess the efficacy of TFL lithotripsy in the upper calyx. Stone ablation experiments were performed on BegoStone phantoms at different combinations of pulse energy (EP) and frequency (F) to determine the optimal settings. Temperature changes and thermal injury risks were monitored using embedded thermocouples. Experiments were also performed on calcium oxalate monohydrate (COM) stones to validate the optimal settings.
Results
High EP/low F settings demonstrated superior treatment efficiency compared to low EP/high F settings using the same power. Specifically, 0.8 J/12 Hz was the optimal setting, resulting in a twofold increase in treatment efficiency, a 39% reduction in energy expenditure per unit of ablated stone mass, a 35% reduction in residual fragments, and a 36% reduction in total procedure time compared to the 0.2 J/50 Hz setting for COM stones. Thermal injury risk assessment indicated that 10 W power settings with high EP/low F combinations remained below the threshold for tissue injury, while higher power settings (>10 W) consistently exceeded the safety threshold.
Conclusions
Our findings suggest that high EP/low F settings, such as 0.8 J/12 Hz, are optimal for TFL lithotripsy in the treatment of COM stones. These settings demonstrated significantly improved treatment efficiency with reduced residual fragments compared to conventional settings while keeping the thermal dose below the injury threshold. This study highlights the importance of using the high EP/low F combination with low power settings, which maximizes treatment efficiency and minimizes potential thermal injury. Further studies are warranted to determine the optimal settings for TFL for treating kidney stones with different compositions.
The ureteral access sheath (UAS) facilitates the use of flexible ureteroscopy, enabling improved minimally invasive management of complex upper urinary tract diseases. The UAS, which comes in a ...variety of diameters and lengths, is passed in a retrograde fashion, aided by a hydrophilic coating and other features designed to confer smooth passage into the ureter with sufficient resistance to kinking and buckling. Use of a UAS has the advantage of enabling repeated passage of the ureteroscope while minimizing damage to the ureter, thus improving the flow of irrigation fluid and visualization within the urethra with reductions in operative times, which improves both the effectiveness of the surgery and reduces the costs. Placement of the UAS carries an increased risk of ureteral wall ischaemia and injury to the mucosal or muscular layers of the ureter, and a theoretically increased risk of ureteral strictures. A ureteral stent is typically placed after ureteroscopy with a UAS. Endourologists have found several additional practical uses of a UAS, such as the percutaneous treatment of patients with ureteral stones, and solutions to other endourological challenges.
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