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Title: Transurethral ultrasound applicators with dynamic multi-sector control for prostate thermal therapy: In vivo evaluation under MR guidance

Abstract

The purpose of this study was to explore the feasibility and performance of a multi-sectored tubular array transurethral ultrasound applicator for prostate thermal therapy, with potential to provide dynamic angular and length control of heating under MR guidance without mechanical movement of the applicator. Test configurations were fabricated, incorporating a linear array of two multi-sectored tubular transducers (7.8-8.4 MHz, 3 mm OD, 6 mm length), with three 120 deg. independent active sectors per tube. A flexible delivery catheter facilitated water cooling (100 ml min{sup -1}) within an expandable urethral balloon (35 mm longx10 mm diameter). An integrated positioning hub allows for rotating and translating the transducer assembly within the urethral balloon for final targeting prior to therapy delivery. Rotational beam plots indicate {approx}90 deg. - 100 deg. acoustic output patterns from each 120 deg. transducer sector, negligible coupling between sectors, and acoustic efficiencies between 41% and 53%. Experiments were performed within in vivo canine prostate (n=3), with real-time MR temperature monitoring in either the axial or coronal planes to facilitate control of the heating profiles and provide thermal dosimetry for performance assessment. Gross inspection of serial sections of treated prostate, exposed to TTC (triphenyl tetrazolium chloride) tissue viability stain, allowedmore » for direct assessment of the extent of thermal coagulation. These devices created large contiguous thermal lesions (defined by 52 deg. C maximum temperature, t{sub 43}=240 min thermal dose contours, and TTC tissue sections) that extended radially from the applicator toward the border of the prostate ({approx}15 mm) during a short power application ({approx}8-16 W per active sector, 8-15 min), with {approx}200 deg. or 360 deg. sector coagulation demonstrated depending upon the activation scheme. Analysis of transient temperature profiles indicated progression of lethal temperature and thermal dose contours initially centered on each sector that coalesced within {approx}5 min to produce uniform and contiguous zones of thermal destruction between sectors, with smooth outer boundaries and continued radial propagation in time. The dimension of the coagulation zone along the applicator was well-defined by positioning and active array length. Although not as precise as rotating planar and curvilinear devices currently under development for MR-guided procedures, advantages of these multi-sectored transurethral applicators include a flexible delivery catheter and that mechanical manipulation of the device using rotational motors is not required during therapy. This multi-sectored tubular array transurethral ultrasound technology has demonstrated potential for relatively fast and reasonably conformal targeting of prostate volumes suitable for the minimally invasive treatment of BPH and cancer under MR guidance, with further development warranted.« less

Authors:
; ; ; ; ; ;  [1]
  1. Thermal Therapy Research Group, Department of Radiation Oncology, University of California, San Francisco, California 94143 (United States) and Joint Graduate Group in Bioengineering, University of California, Berkeley and San Francisco, California 94158 (United States)
Publication Date:
OSTI Identifier:
21120700
Resource Type:
Journal Article
Journal Name:
Medical Physics
Additional Journal Information:
Journal Volume: 35; Journal Issue: 5; Other Information: DOI: 10.1118/1.2900131; (c) 2008 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0094-2405
Country of Publication:
United States
Language:
English
Subject:
62 RADIOLOGY AND NUCLEAR MEDICINE; DOGS; IN VIVO; NEOPLASMS; NMR IMAGING; PROSTATE; RADIOTHERAPY; TEMPERATURE MONITORING; TETRAZOLIUM; TRANSDUCERS; ULTRASONOGRAPHY; WATER

Citation Formats

Kinsey, Adam M, Diederich, Chris J, Rieke, Viola, Nau, William H, Pauly, Kim Butts, Bouley, Donna, Sommer, Graham, Department of Radiology, Stanford University Medical Center, Stanford, California 94305, Thermal Therapy Research Group, Department of Radiation Oncology, University of California, San Francisco, California 94143, Department of Radiology, Stanford University Medical Center, Stanford, California 94305, Department of Comparative Medicine, Stanford University, Stanford, California 94305, and Department of Radiology, Stanford University Medical Center, Stanford, California 94305. Transurethral ultrasound applicators with dynamic multi-sector control for prostate thermal therapy: In vivo evaluation under MR guidance. United States: N. p., 2008. Web. doi:10.1118/1.2900131.
Kinsey, Adam M, Diederich, Chris J, Rieke, Viola, Nau, William H, Pauly, Kim Butts, Bouley, Donna, Sommer, Graham, Department of Radiology, Stanford University Medical Center, Stanford, California 94305, Thermal Therapy Research Group, Department of Radiation Oncology, University of California, San Francisco, California 94143, Department of Radiology, Stanford University Medical Center, Stanford, California 94305, Department of Comparative Medicine, Stanford University, Stanford, California 94305, & Department of Radiology, Stanford University Medical Center, Stanford, California 94305. Transurethral ultrasound applicators with dynamic multi-sector control for prostate thermal therapy: In vivo evaluation under MR guidance. United States. doi:10.1118/1.2900131.
Kinsey, Adam M, Diederich, Chris J, Rieke, Viola, Nau, William H, Pauly, Kim Butts, Bouley, Donna, Sommer, Graham, Department of Radiology, Stanford University Medical Center, Stanford, California 94305, Thermal Therapy Research Group, Department of Radiation Oncology, University of California, San Francisco, California 94143, Department of Radiology, Stanford University Medical Center, Stanford, California 94305, Department of Comparative Medicine, Stanford University, Stanford, California 94305, and Department of Radiology, Stanford University Medical Center, Stanford, California 94305. Thu . "Transurethral ultrasound applicators with dynamic multi-sector control for prostate thermal therapy: In vivo evaluation under MR guidance". United States. doi:10.1118/1.2900131.
@article{osti_21120700,
title = {Transurethral ultrasound applicators with dynamic multi-sector control for prostate thermal therapy: In vivo evaluation under MR guidance},
author = {Kinsey, Adam M and Diederich, Chris J and Rieke, Viola and Nau, William H and Pauly, Kim Butts and Bouley, Donna and Sommer, Graham and Department of Radiology, Stanford University Medical Center, Stanford, California 94305 and Thermal Therapy Research Group, Department of Radiation Oncology, University of California, San Francisco, California 94143 and Department of Radiology, Stanford University Medical Center, Stanford, California 94305 and Department of Comparative Medicine, Stanford University, Stanford, California 94305 and Department of Radiology, Stanford University Medical Center, Stanford, California 94305},
abstractNote = {The purpose of this study was to explore the feasibility and performance of a multi-sectored tubular array transurethral ultrasound applicator for prostate thermal therapy, with potential to provide dynamic angular and length control of heating under MR guidance without mechanical movement of the applicator. Test configurations were fabricated, incorporating a linear array of two multi-sectored tubular transducers (7.8-8.4 MHz, 3 mm OD, 6 mm length), with three 120 deg. independent active sectors per tube. A flexible delivery catheter facilitated water cooling (100 ml min{sup -1}) within an expandable urethral balloon (35 mm longx10 mm diameter). An integrated positioning hub allows for rotating and translating the transducer assembly within the urethral balloon for final targeting prior to therapy delivery. Rotational beam plots indicate {approx}90 deg. - 100 deg. acoustic output patterns from each 120 deg. transducer sector, negligible coupling between sectors, and acoustic efficiencies between 41% and 53%. Experiments were performed within in vivo canine prostate (n=3), with real-time MR temperature monitoring in either the axial or coronal planes to facilitate control of the heating profiles and provide thermal dosimetry for performance assessment. Gross inspection of serial sections of treated prostate, exposed to TTC (triphenyl tetrazolium chloride) tissue viability stain, allowed for direct assessment of the extent of thermal coagulation. These devices created large contiguous thermal lesions (defined by 52 deg. C maximum temperature, t{sub 43}=240 min thermal dose contours, and TTC tissue sections) that extended radially from the applicator toward the border of the prostate ({approx}15 mm) during a short power application ({approx}8-16 W per active sector, 8-15 min), with {approx}200 deg. or 360 deg. sector coagulation demonstrated depending upon the activation scheme. Analysis of transient temperature profiles indicated progression of lethal temperature and thermal dose contours initially centered on each sector that coalesced within {approx}5 min to produce uniform and contiguous zones of thermal destruction between sectors, with smooth outer boundaries and continued radial propagation in time. The dimension of the coagulation zone along the applicator was well-defined by positioning and active array length. Although not as precise as rotating planar and curvilinear devices currently under development for MR-guided procedures, advantages of these multi-sectored transurethral applicators include a flexible delivery catheter and that mechanical manipulation of the device using rotational motors is not required during therapy. This multi-sectored tubular array transurethral ultrasound technology has demonstrated potential for relatively fast and reasonably conformal targeting of prostate volumes suitable for the minimally invasive treatment of BPH and cancer under MR guidance, with further development warranted.},
doi = {10.1118/1.2900131},
journal = {Medical Physics},
issn = {0094-2405},
number = 5,
volume = 35,
place = {United States},
year = {2008},
month = {5}
}