Clinical validation of real-time tissue change monitoring during prostate tissue ablation with high intensity focused ultrasound

Abstract

BackgroundThe purpose of these clinical studies was to validate a Tissue Change Monitoring (TCM) algorithm in vivo. TCM is a quantitative tool for the real-time assessment of HIFU dose. TCM provides quantitative analysis of the backscatter pulse echo signals (pre and immediately post HIFU) for each individual ablative site, using ultrasonic tissue characterization as a surrogate for monitoring tissue temperature. Real-time analysis generates an energy difference parameter (ΔE in dB) that is proportional to tissue temperature.MethodsPost in vitro studies, two clinical studies were conducted to validate the TCM algorithm on the Sonablate® device. Studies enrolled histologically confirmed, organ confined prostate cancer patients. The first clinical study was conducted in two phases for whole gland ablation. First eight patients’ data were used to measure the algorithm performance followed by 89 additional patients for long term outcome. The second clinical study enrolled five patients; four patients with focal cancer had hemi-ablation only and one had whole gland ablation. Four 3 Fr. needles containing three thermocouples each were placed transperineally in the prostate to record tissue temperatures in the focal zone, posterior to the focal zone and on the lateral gland where no HIFU was applied. Tissue temperatures from the focal zone were correlated to the ΔE parameter.ResultsIn the first clinical study, the average TCM rate was 86%. Pre and 6 months post HIFU, median PSA was 7.64 and 0.025 ng/ml respectively and 97% patients had negative biopsy. For the second clinical study, the measured prostate tissue temperatures (Average, Max, and Min) in the ablation zones were 84°, 114° and 60 °C and the corresponding ΔE (dB/10) parameters were 1.05, 2.6 and 0.4 resulting in 83% of temperatures in the range of 75°-100 °C and 17% in the 60°-74 °C range. Outside the focal zone, the average temperature was 50 °C and in the lateral lobe where no HIFU was applied, peak temperature was 40.7 °C.ConclusionsThe TCM algorithm is able to estimate tissue changes reliably during the HIFU procedure for prostate tissue ablation in real-time and can be used as a guide for HIFU dose delivery and tissue ablation control.

Thermal Ablation and High-Resolution Imaging Using a Back-to-Back (BTB) Dual-Mode Ultrasonic Transducer: In Vivo Results

“…As shown in Figure 8, the tissues around the target region were not adversely affected. High-frequency ultrasound imaging at 20.0 MHz with a lateral resolution of 200 µm is ideally suited for monitoring these echo-induced changes as these parameters overcome the resolution limitations of previous ultrasound-guided HIFU devices [25][26][27][28]. The use of a specular reflector along the small intestinal wall helps to emphasize the boundaries of the small intestine.…”

“…A dualfrequency sensor based on a capacitive micromachined ultrasonic transducer (CMUT) combines imaging and HIFU systems into one integrated circuit [26]. Recently, integrated ultrasonic systems that combine imaging and HIFU with mechanical scanning in both the transverse and sagittal planes have been developed for the treatment of localized prostate cancer [27]. This "see and treat" technology is especially well applied in the skin treatment field, as it provides advantages in ultrasound imaging of the dermal and subcutaneous tissue layers down to 4.5 mm [28].…”

Heating technology for malignant tumors: a review

“…Commercially available MR guided devices which incorporate MR-thermometry sequences include the BSD-2000 Sigma-Eye which can be integrated into the MR systems of various vendors (see section 'Locoregional heating techniques'), as well as the Sonalleve HIFU system integrated into the 3 T Achieva MR system (Philips) and the ExAblate FUS system integrated into the Discovery MR450w 1.5 T wide bore and Discovery MR750w 3.0 T wide bore MR systems (GE). US guidance is clinically used in combination with ablative SFUS devices; the Sonablate [391] and Ablatherm [392] systems, where feedback is based on changes in echogenicity rather than temperature mapping [393] (see also section 'Local heating techniques: scanned focused ultrasound').…”

Histotripsy: The Next Generation of High‐Intensity Focused Ultrasound for Focal Prostate Cancer Therapy

“…Sophisticated mathematical techniques as well as advanced US technology such as that reported by Lyka et al, in which prostate motion registration optimizes targeting, have been used for the performance of fused and transrectal US examinations at biopsies and could be applied to HIFU monitoring as well. Algorithms have been produced that are clinically available, such as the Tissue Change Monitoring system on the Sonoblate system, which allows real‐time US imaging to monitor HIFU treatment . It has been noted that during treatment of prostate cancer with HIFU, the resulting edema causes the prostate to enlarge, which changes the targeting of the treatment zone.…”