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MRI‐guided interstitial ultrasound thermal therapy of the prostate: A feasibility study in the canine model
Author(s) -
Nau William H.,
Diederich Chris J.,
Ross Anthony B.,
Butts Kim,
Rieke Viola,
Bouley Donna M.,
Gill Harcharan,
Daniel Bruce,
Sommer Graham
Publication year - 2005
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.1861163
Subject(s) - ultrasound , medicine , prostate , radiology , magnetic resonance imaging , medical imaging , nuclear medicine , medical physics , cancer
The feasibility of MRI‐guided interstitial ultrasound thermal therapy of the prostate was evaluated in an in vivo canine prostate model. MRI compatible, multielement interstitial ultrasound applicators were developed using1.5 mmdiameter cylindrical piezoceramic transducers (7 to 8 MHz ) sectored to provide180 °of angular directional heating. Two in vivo experiments were performed in canine prostate. The first using two interstitial ultrasound applicators, the second using three ultrasound applicators in conjunction with rectal and urethral cooling. In both experiments, the applicators were inserted transperineally into the prostate with the energy directed ventrally, away from the rectum. Electrical power levels of5 – 17 Wper element ( ∼ 1.6 – 5.4 Wacoustic output power) were applied for heating periods of 18 and48 min . Phase‐sensitive gradient‐echo MR imaging was used to monitor the thermal treatment in real‐time on a0.5 Tinterventional MRI system. Contrast‐enhanced T1‐weighted images and vital‐stained serial tissue sections were obtained to assess thermal damage and correlate to real‐time thermal contour plots and calculated thermal doses. Results from these studies indicated a large volume of ablated (nonstained) tissue within the prostate, extending 1.2 to2.0 cmfrom the applicators to the periphery of the gland, with the dorsal margin of coagulation well‐defined by the applicator placement and directionality. The shape of the lesions correlated well to the hypointense regions visible in the contrast‐enhanced T1‐weighted images, and were also in good agreement with the contours of the52 ° Cthreshold temperature andt 43 > 240 min . This study demonstrates the feasibility of using directional interstitial ultrasound in conjunction with MRI thermal imaging to monitor and possibly control thermal coagulation within a targeted tissue volume while potentially protecting surrounding tissue, such as rectum, from thermal damage.