Objectives-This work aims to develop the technique of histotripsy ultrasound therapy as a noninvasive treatment for benign prostatic hyperplasia (BPH). We have previously demonstrated the feasibility of prostate histotripsy fractionation in a canine model. The purpose of this paper is to examine the histotripsy dose -tissue response effect over time to provide insight for treatment optimization.Methods-Various doses of histotripsy were applied trans-abdominally to the prostates of 20 canine subjects. Treated prostates were then harvested at interval time points from zero to 28 days and assessed for histologic treatment response.

Purpose Histotripsy is an extracorporeal ultrasound (US) technology that utilizes cavitational mechanisms to produce non-thermal tissue destruction. Previously, we demonstrated the feasibility of histotripsy for fractionation and immediate debulking of prostate tissue. The purpose of this study is to characterize the local effects and systemic response after histotripsy treatment of prostate tissue in an in-vivo canine model. Materials and Methods Histotripsy was applied transabdominally to the prostate in eighteen intact male canine subjects under general anesthesia. Acoustic bursts (4 microseconds) were delivered at 300 Hz pulse repetition rate from a highly focused 750 kHz piezoelectric US transducer (15 cm aperture, 3×3×8 mm focal volume). The prostate and surrounding structures were harvested at prescribed time points (0, 7, 28, or 56 days) following histotripsy. Blood and urine parameters were assessed periodically while clinical evaluation incorporating a validated veterinary pain scale was performed daily. Results Conventional transrectal US imaging facilitated targeting of the focal volume and provided real-time assessment of cavitation activity. Fractionation of the targeted volume and clearance of the resultant debris with urination produced a treatment cavity within each prostate. No acoustic collateral damage was seen and urothelialization of the treatment cavity occurred within 28 days of treatment. Only transient lab abnormalities and minimal hematuria were noted after treatment. Pain scores revealed only mild post treatment discomfort. Conclusions Histotripsy produced consistent tissue fractionation and prostate debulking without collateral acoustic injury or clinical side effects and was well tolerated in the canine model.

Purpose Histotripsy is a non-invasive ultrasound technology which induces microbubble formation (cavitation) within tissues producing mechanical tissue fractionation. During initial in-vivo feasibility canine studies of prostate ablation, minimal hematuria was observed. In the current study, we sought to further explore this phenomenon by performing extensive prostate histotripsy treatments in anticoagulated canines. Materials and Methods Histotripsy was performed on 9 canine subjects pre-treated with 6 mg of oral warfarin for 3 to 5 days using an extracorporeal 750 kHz therapeutic ultrasound transducer delivering acoustic pulses to the prostatic urethra and periurethral parenchyma. After 7–28 days, the subjects were euthanized, transrectal prostate ultrasound was performed and the prostate was harvested. Serum hemoglobin and International Normalization Ratio (INR) were measured immediately prior to histotripsy treatment and at euthanasia. Results Mean treatment INR was 4.6 (median 2.4, range 1.2 to 11.3). There was no clinically significant change in hemoglobin concentration at euthanasia compared to baseline. At harvest, histologic sections of the prostate revealed a large cavity corresponding to the planned treatment volume incorporating the prostatic urethra and parenchyma in all subjects. Urine was clear within 2 days of treatment and no blood clots were seen. Conclusions Despite therapeutic and supratherapeutic anticoagulation, histotripsy resulted in minimal bleeding despite significant fractionation and tissue debulking of the prostate. These results have prompted further studies to understand the mechanism of non-thermal hemostasis underlying histotripsy.

This study aimed to measure acoustic access to the prostate for extracorporeal ultrasound ablation. Both transabdominal and transperineal approaches were considered. The objective was to measure the size and shape of the aperture available for unobstructed targeting of the prostate. CT images of 17 randomly selected men >56 years of age were used to create 3D reconstructions of the lower abdomen and pelvis. Rays were traced from target locations in the prostate toward the perineum and the abdomen. The maximum CT density encountered along each path was recorded; those paths that traversed structures with CT density exceeding a soft tissue threshold were considered to be blocked by bone. Unblocked rays comprised the accessible aperture. The aperture through the perineum was found to be a triangular-shaped region bounded by the lower bones of the pelvis varying significantly in size between subjects. The free aperture through the abdomen was wedge shaped limited by the pubis and also with great subject-to-subject variability. Average unblocked fractions of an f=1 transducer to target base, middle, and apex of the prostate along the urethra from the perineum were 77.0%, 94.4%, and 99.6%, respectively. Averages targeting from the abdomen were 86.1%, 52.3%, and 11.0%. Acoustic access to the prostate for therapy through the perineum was judged to be feasible. Access from the abdomen was judged to be sufficient for the base of the prostate, but likely inadequate for the middle and apex.

No abstract

Minimally invasive surgical procedures have revolutionized surgery of the paranasal sinuses. The endonasal procedure has become standard practice due to a better understanding of pathological physiology. However, malformations, previous operations and bleeding can interfere greatly with intraoperative orientation. Together with microscopy and endoscopy, image-guided surgery has the potential to be of significant assistance to the surgeon. We evaluated the electromagnetic navigation system InstaTrak 2000 (Visualization Technologies Inc., Lawrence, MA) in 168 patients with various disorders of the paranasal sinuses who underwent endonasal surgery. The system consists of a headset attached to an electronic transmitter which is fitted on the dorsum of the nose and in the external auditory canal. With the aid of low-frequency magnetic fields the position of the instrument equipped with an electromagnetic receiver is calculated on the basis of the reaction of ferromagnetic components in the magnetic field; the location is displayed in orthogonal sections on a high resolution screen. The intraoperative accuracy of the system was estimated to be 1.2-2.8 mm. The preparation time amounted to < 10 min. No system failures were observed. The InstaTrak 2000 navigation system is only suitable for endonasal surgery. The placement of the electromagnetic transmitter and receiver allows flexible head positioning through the use of a headset. This system is a valuable aid for the surgeon under anatomically complex conditions. The technology also lends itself well to training purposes, as visualization in different sectional planes augments the understanding of anatomy and pathological anatomy.

No abstract

No abstract