Preclinical evaluation of a clinical prototype transrectal diffuse optical tomography system for monitoring photothermal therapy of focal prostate cancer.

Celina L Li,Carl J Fisher,Brian C Wilson,Robert A Weersink

doi:10.1117/1.jbo.27.2.026001

Abstract

.Significance: Our work demonstrates in preclinical models that continuous-wave transrectal diffuse optical tomography (TRDOT) can be used to accurately monitor photothermal therapy (PTT) and, in particular, the progression of the photocoagulation boundary toward the rectum. When used in patients, this should prevent rectal damage during PTT, thereby achieving maximum treatment efficacy while ensuring safety, using a technology platform suitable for wide dissemination.Aim: We aim to validate that TRDOT measurements analyzed using a shape-based image-reconstruction algorithm (SBDOT) allow localization of the photocoagulation boundary during PTT within toward the rectum in the transverse plane.Approach: TRDOT measurements were performed in tissue-simulating phantoms, ex vivo tissues, and an in vivo canine prostate model. The accuracy and sensitivity of reconstructing the size and location of the coagulation zone were determined, based on changes in the tissue absorption and reduced scattering coefficients upon photocoagulation. The reconstruction also yields the native and coagulated tissue optical properties.Results: The TRDOT measurements and SBDOT reconstruction algorithm were confirmed to perform sufficiently well for clinical translation in PTT monitoring, recovering the location of the coagulation boundary within compared to the true value as determined by direct visualization postexcision and/or MRI.Conclusions: Implementing previously described TRDOT instrumentation and SBDOT image reconstruction in different tissue models confirms the potential for clinincal translation, including required refinements of the system and reconstruction algorithm.

Highlights

Screening programs for prostate cancer (PCa) have increased the detection rate of low- and intermediate-risk disease confined to the prostate, for which treatment options range from active surveillance, with risk of disease progression, to radical therapies that carry significant rates of urinary incontinence and erectile dysfunction.[1,2] Focal ablative therapies, in which treatment is targeted to the dominant lesion ratherJournal of Biomedical OpticsDownloaded From: https://www.spiedigitallibrary.org/journals/Journal-of-Biomedical-Optics on 28 Feb 2022 Terms of Use: https://www.spiedigitallibrary.org/terms-of-useFebruary 2022 Vol 27(2)Li et al.: Preclinical evaluation of a clinical prototype transrectal diffuse optical tomography system. . .than the whole gland, aim to minimize morbidity while achieving successful cancer control and preserving the possibility of retreatment
The shape-based imagereconstruction algorithm (SBDOT) reconstructed radius was r 1⁄4 10.8 Æ 0.2 mm, compared with the true value of 10 mm
This work has confirmed the feasibility and accuracy of transrectal diffuse optical tomography (TRDOT) with shape-based reconstruction of the coagulation zone for monitoring photothermal therapy (PTT) treatments. This particular algorithm is not designed for reconstructing the tissue optical properties with high accuracy but, rather, to localize the photocoagulation boundary accurately with respect to the rectal wall

Summary

Introduction

Screening programs for prostate cancer (PCa) have increased the detection rate of low- and intermediate-risk disease confined to the prostate (focal tumors), for which treatment options range from active surveillance, with risk of disease progression, to radical therapies (prostatectomy and radiotherapy) that carry significant rates of urinary incontinence and erectile dysfunction.[1,2] Focal ablative therapies, in which treatment is targeted to the dominant (index) lesion ratherJournal of Biomedical OpticsDownloaded From: https://www.spiedigitallibrary.org/journals/Journal-of-Biomedical-Optics on 28 Feb 2022 Terms of Use: https://www.spiedigitallibrary.org/terms-of-useFebruary 2022 Vol 27(2)Li et al.: Preclinical evaluation of a clinical prototype transrectal diffuse optical tomography system. . .than the whole gland, aim to minimize morbidity while achieving successful cancer control and preserving the possibility of retreatment. Several clinical trials and case studies in low/intermediate-risk PCa patients have demonstrated that PTT can achieve minimal adverse effects and biopsyconfirmed tumor ablation in most cases, with 70% to 80% being radiologically and pathologically disease-free in the targeted ablation zone at 3 to 18 months follow up.[13,14,15,16,17,18] due to the limited spatial resolution and indirect monitoring of the coagulation zone based on MRI temperature mapping, the photocoagulation front (boundary of thermal coagulation) cannot be delineated precisely enough to achieve complete tumor destruction in all cases, for tumors in the posterior capsule, because of the need to prevent damage to the rectal wall. For example, only 11 out of 23 patients had complete target ablation.[19]

Objectives

Methods

Results

Conclusion