DocumentCode :
3366704
Title :
Gas-bubble enhanced heating in rabbit thigh in vivo
Author :
Sokka, S. ; King, Randy ; McDannold, Nathan ; Hynynen, Kullervo
Author_Institution :
Focused Ultrasound Lab., Harvard Med. Sch., Boston, MA, USA
Volume :
2
fYear :
2002
fDate :
8-11 Oct. 2002
Firstpage :
1415
Abstract :
In this study, we propose a focused ultrasound surgery protocol that induces and then uses gas bubbles at the focus to enhance the ultrasound absorption and ultimately create larger lesions in vivo. MRI and ultrasound visualization and monitoring methods for this heating method are also investigated. Larger lesions created with a carefully monitored single ultrasound exposure could greatly improve the speed of tumor coagulation with focused ultrasound. All experiments were performed under MRI (clinical, 1.5T) guidance with one of two eight-sector spherically curved piezoelectric transducers (1.1 and 1.7 MHz). An ultrasound detector ring was fixed with the therapy transducer to monitor gas bubble activity during treatment. FUS exposures were delivered to the thighs of seven New Zealand white rabbits. The experimental, gas bubble-enhanced heating exposures consisted of a high amplitude 300 acoustic watt, half second pulse followed by a 7 W, 14 W, or 21 W continuous wave exposure for 19.5 seconds. The respective control sonications were 20-second exposures of 14 W, 21 W, and 28 W. During the exposures, MR thermometry was obtained, and MR T2-enhanced imaging was used to evaluate the resulting lesions. Specific metrics were used to evaluate the differences between the gas-bubble enhanced exposures and their respective control sonications: temperatures with respect to time and space, lesion size and shape, and their agreement with thermal dose predictions. The bubble-enhanced exposures showed a faster temperature rise and higher overall temperatures than the sonications without bubble formation. The MRI derived spatial temperature and thermal dose maps closely correlated with the resulting lesion as examined by T2-wieghted imaging. The lesions created with the gas-bubble enhanced heating exposures were 3 times larger by volume, were consistently more spherical in shape, and closer to the transducer than the control exposures. The study demonstrates that gas bubbles can reliably be used to create significantly larger lesions in vivo.
Keywords :
biological effects of acoustic radiation; biomedical MRI; biomedical ultrasonics; biothermics; bubbles; muscle; piezoelectric transducers; radiation therapy; surgery; tumours; ultrasonic effects; ultrasonic transducers; 1.1 MHz; 1.5 T; 1.7 MHz; 14 W; 19.5 sec; 21 W; 28 W; 7 W; MRI derived spatial temperature maps; MRI derived thermal dose maps; New Zealand white rabbits; bubble formation; bubble-enhanced exposures; clinical magnetic resonance imaging guidance; continuous wave exposure; eight-sector spherically curved piezoelectric transducers; focused ultrasound surgery protocol; gas bubble activity; gas bubble-enhanced heating exposures; gas-bubble enhanced heating; heating method; lesion shape; lesion size; lesions; magnetic resonance T2-enhanced imaging; magnetic resonance thermometry; rabbit thigh in vivo; single ultrasound exposure; sonications; therapy transducer; thermal dose predictions; tumor coagulation; ultrasound absorption; ultrasound detector ring; ultrasound monitoring methods; ultrasound visualization; Focusing; Heating; In vivo; Lesions; Magnetic resonance imaging; Monitoring; Rabbits; Shape control; Thigh; Ultrasonic imaging;
fLanguage :
English
Publisher :
ieee
Conference_Titel :
Ultrasonics Symposium, 2002. Proceedings. 2002 IEEE
ISSN :
1051-0117
Print_ISBN :
0-7803-7582-3
Type :
conf
DOI :
10.1109/ULTSYM.2002.1192561
Filename :
1192561
Link To Document :
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