Simultaneous temperature and magnetization transfer (MT) monitoring during high-intensity focused ultrasound (HIFU) treatment: preliminary investigation on ex vivo porcine muscle.
OBJECTIVE
To measure temperature change and magnetization transfer ratio (MTR) simultaneously during high-intensity focused ultrasound (HIFU) treatment.


METHODS
This study proposed an interleaved dual gradient-echo technique to monitor the heat and tissue damage brought to the heated tissue. The technique was applied to tissue samples to test its efficacy.


RESULTS
Ex vivo experiments on the porcine muscle demonstrated that both temperature changes and MTR exhibited high consistency in localizing the heated regions. As the heat dissipated after the treatment, the temperature of the heated regions decreased rapidly but MTR continued to be elevated. Moreover, thermal dose (TD) maps derived from the temperature curves demonstrated a sharp margin in the heated regions, but MTR maps may show a spatial gradient of tissue damage, suggesting complimentary information provided by these two measures.


CONCLUSIONS
In a protocol of spot-by-spot heating over a large volume of tissue, MTR provides additional values to mark the locations of previously heated regions. By continuously recording the locations of heated spots, MTR maps could help plan the next target spots appropriately, potentially improving the efficiency of HIFU treatment and reducing undesirable damage to the normal tissue.
Peng
Hsu-Hsia
HH
Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Hsinchu, Taiwan.
Huang
Teng-Yi
TY
Tseng
Wen-Yih Isaac
WY
Lin
En-Li
EL
Chung
Hsiao-Wen
HW
Wu
Chih-Ching
CC
Wang
Yu-Shun
YS
Chen
Wen-Shiang
WS
D000818:Animals; D001831:Body Temperature; D006358:Hot Temperature; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008991:Monitoring, Physiologic / Q000379:methods*; D018482:Muscle, Skeletal / Q000033:anatomy & histology* / Q000293:injuries; D015203:Reproducibility of Results; D013552:Swine; D013696:Temperature; D013997:Time Factors; D014464:Ultrasonic Therapy / Q000009:adverse effects / Q000379:methods*