Prostate Cryotherapy Monitoring Using Vibroacoustography: Preliminary Results of an Ex Vivo Study and Technical Feasibility

Abstract

The objective of this research is to prospectively evaluate the feasibility of vibroacoustography (VA) imaging in monitoring prostate cryotherapy in an ex vivo model. Baseline scanning of an excised human prostate is accomplished by a VA system apparatus in a tank of degassed water. Alcohol and dry ice mixture are used to freeze two prostate tissue samples. The frozen prostates are subsequently placed within the water tank at 27°C and rescanned. VA images were acquired at prescribed time intervals to characterize the acoustic properties of the partially frozen tissue. The frozen prostate tissue appears in the images as hypoemitting signal. Once the tissue thaws, previously frozen regions show coarser texture than prior to freezing. The margin of the frozen tissue is delineated with a welldefined rim. The thawed cryolesions show a different contrast compared with normal unfrozen prostate. In conclusion, this pilot study shows that VA produces clear images of a frozen prostate at different temperature stages. The frozen tissue appears as a uniform region with well-defined borders that are readily identified. These characteristic images should allow safer and more efficient application of prostatic cryosurgery. These results provide substantial motivation to further investigate VA as a potential modality to monitor prostate cryotherapy intraoperatively.

High-intensity focused ultrasound monitoring using harmonic motion imaging for focused ultrasound (HMIFU) under boiling or slow denaturation conditions

“…Noninvasive echo-shift-based thermography is capable of sub-millimeter mapping of HIFU focal zone based on the tissue echo shifts induced by changes in speed of sound with temperature rise [9–11]. Other ultrasound-based techniques have also investigated the distinctive spectral characteristics from the backscattered signals of the thermal lesion [12], as well as assessment of elasticity properties with mechanical excitation using static [13], dynamic [14], or acoustic radiation force [15–17] for visualizing treatment targets and the induced thermal lesions [18–29]. …”

Vibro-acoustography beam formation with reconfigurable arrays

“…This small difference is quantitative evidence that the Field II and Fresnel methods are within good agreement. (11) where the normalized pressure fields are given as p N,FieldII = p FieldII …”

“…These problems can be partially solved by using a water tank to host the transducer. Multiple laboratory VA studies using the confocal transducer in a water tank have been performed in breast [7] [8], thyroid [9], and prostrate tissues [10] [11] [12] [13]. The same confocal transducer has been also used for in vivo measurements in human breast [14] [15] [16].…”

Complex background suppression for vibro-acoustography images

“…Vibro-acoustography has been used in imaging of arteries [3], breast [4, 5], thyroid [6], prostate [7-9], and in other biomedical applications [10]. It has also been used in nondestructive evaluation and imaging of surface roughness [11, 12].…”