Improved visualization of high-intensity focused ultrasound lesions.
Spectral parameter imaging in both the fundamental and harmonic of backscattered radio-frequency (RF) data were used for immediate visualization of high-intensity focused ultrasound (HIFU) lesion sites. A focused 5-MHz HIFU transducer with a coaxial 9-MHz focused single-element diagnostic transducer was used to create and scan lesions in chicken breast and freshly excised rabbit liver. B-mode images derived from the backscattered RF signal envelope were compared with midband fit (MBF) spectral parameter images in the fundamental (9-MHz) and harmonic (18-MHz) bands of the diagnostic probe. Images of HIFU-induced lesions derived from the MBF to the calibrated spectrum showed improved contrast (approximately 3 dB) of tumor margins versus surround compared with images produced from the conventional signal envelope. MBF parameter images produced from the harmonic band showed higher contrast in attenuated structures (core, shadow) compared with either the conventional envelope (3.3 dB core; 11.6 dB shadow) or MBF images of the fundamental band (4.4 dB core; 7.4 dB shadow). The gradient between the lesion and surround was 3.4 dB/mm, 6.9 dB/mm and 17.2 dB/mm for B-mode, MBF-fundamental mode and MBF-harmonic mode, respectively. Images of threshold and "popcorn" lesions produced in freshly excised rabbit liver were most easily visualized and boundaries best-defined using MBF-harmonic mode.
Silverman
Ronald H
RH
Riverside Research Institute, New York, NY, USA. rsilverman@rrinyc.org
Muratore
Robert
R
Ketterling
Jeffrey A
JA
Mamou
Jonathan
J
Coleman
D Jackson
DJ
Feleppa
Ernest J
EJ
D000818:Animals; D002645:Chickens; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008099:Liver / Q000000981:diagnostic imaging; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging; D011817:Rabbits; D014159:Transducers; D014464:Ultrasonic Therapy / Q000295:instrumentation / Q000379:methods*; D014463:Ultrasonography