Introduction: The Moses technology for the Ho:YAG laser introduces a pulse-shape modulation that optimizes energy delivery through water. The aim of this study was to assess fiber tip to stone working distance on fragmentation incorporating a variety of pulse modes.
Methods: Experiments were conducted with a 3D positioner, a 30 mm flat BegoStone, and a 230 µm fiber utilizing short pulse (SP), long pulse (LP), Moses Contact (MC), and Moses Distance (MD) modes. Ablation crater volume was measured by 3D confocal microscopy, after a single pulse (1.0J) with the fiber tip positioned at 0, 0.5, 1, 2, and 3 mm from the stone. Fragmentation efficiency (1Jx10Hz) was assessed with the fiber tip at 0 and 1 mm distance, programmed to fragment the stone over 3 minutes. Fragmentation was defined as difference in stone mass before and after each experiment.
Results: For all tested pulse modes, ablation crater volume and fragmentation were greatest when the fiber tip was in contact with the stone. Ablation declined as the working distance increased with no ablation occurring at 3 mm. At 1 mm distance, ablation volume using MD mode was significantly higher when compared to SP, LP and MC (p<0.05). Compared to all modes tested, MD resulted in 28% and 39% greater fragmentation at both 0 and 1 mm working distance, respectively (p<0.05).
Conclusion: Holmium laser lithotripsy is significantly affected by fiber working distance. At 0 and 1 mm distance, MD had the greatest fragmentation efficiency suggesting this mode may have advantages during ureteroscopy.
We explored the potential of an emerging laser-based technology, photoacoustic imaging (PAI), for bladder cancer
diagnosis through high resolution imaging of microvasculature in the interior bladder tissues. Images of ex vivo canine
bladders demonstrated the excellent ability of PAI to map three-dimensional microvasculature in optically scattering
bladder tissues. By comparing the results from human bladder specimens affected by cancer to those from the normal
control, the feasibility of PAI in differentiating malignant from benign bladder tissues was explored. The reported
distinctive morphometric characteristics of tumor microvasculature can be seen in the images from cancer samples,
suggesting that PAI may allow in vivo assessment of neoangiogenesis that is closely associated with bladder cancer
generation and progression. By presenting subsurface morphological and physiological information in bladder tissues,
PAI, when performed in a similar way to that in conventional endoscopy, provides an opportunity for improved
diagnosis, staging and treatment guidance of bladder cancer.
Histotripsy is an extracorporeal ablative technology that utilizes microsecond pulses of intense ultrasound (< 1% duty
cycle) to produce nonthermal, mechanical fractionation of targeted tissue. We have previously demonstrated the
feasibility of histotripsy prostate ablation. In this study we sought to assess the chronic tissue response, tolerability and
safety of histotripsy in a chronic in vivo canine model. Five acute and thirteen chronic canine subjects were anesthetized
and treated with histotripsy targeting the prostate. Pulses consisted of 3 cycle bursts of 750 kHz ultrasound at a repetition
rate of 300 Hz delivered transabdominally from a highly focused 15 cm aperture array. Transrectal ultrasound imaging
provided accurate targeting and real-time monitoring of histotripsy treatment. Prostates were harvested at 0, 7, 28, or 56
days after treatment. Consistent mechanical tissue fractionation and debulking of prostate tissue was seen acutely and at
delayed time points without collateral injury. Urothelialization of the treatment cavity was apparent 28 days after
treatment. Canine subjects tolerated histotripsy with minimal hematuria or discomfort. Only mild transient lab
abnormalities were noted. Histotripsy is a promising non-invasive therapy for prostate tissue fractionation and
debulking that appears safe and well tolerated without systemic side effects in the canine model.
Conference Committee Involvement (2)
Therapeutics and Diagnostics in Urology 2021
23 January 2021 | San Francisco, California, United States
Therapeutics and Diagnostics in Urology 2020
1 February 2020 | San Francisco, California, United States