A comparison of laser-ultrasound detection system sensitivity with a broad-band ultrasonic source for biomedical applications.
BACKGROUND
Laser ultrasound detection systems are used for noninvasive imaging of internal structures and function of soft tissues. The detection systems with a high sensitivity can be used for detecting small tumors located deeply in human tissues, such as the breast. In this study, the sensitivity of existing ultrasonic detection systems has been compared experimentally by using thermoelastic waves as a broadband ultrasonic source.


METHODS
For the comparison, an optical stress transducer, a polyvinylidene difluoride (PVDF) sheet and a calibrated PVDF needle hydrophone were used. To ensure that all detection systems were interrogated by the same ultrasonic field, a small optical instrument was constructed to fix the generating laser head. The sensitivity was evaluated by measuring signal-to-noise ratios (SNRs) and noise equivalent pressures (NEPs).


RESULTS
The PVDF system, with a 4 kPa NEP, has a 22-dB better performance than the optical stress transducer. The optical stress transducer showed nearly the same sensitivity as the hydrophone for detecting ultrasound waves at a 1-cm distance.


CONCLUSIONS
PVDF detection system provides a useful tool for imaging of soft tissues because of its high sensitivity and broadband detection range.
Hejazi
Marjaneh
M
Department of Medical Physics and Biomedical Systems, Faculty of Medicine, Tehran University of Medical Sciences, and Research Centre for Science and Technology in Medicine (RCSTIM), Tehran, Iran. mhejazi@sina.tums.ac.ir
Abolhassani
Mohamad D
MD
Ahmadian
Alireza
A
Frenz
M
M
Jaeger
M
M
Niederhauser
J J
JJ
Amjadi
A
A
D020811:Biomedical Technology / Q000295:instrumentation* / Q000379:methods*; D004867:Equipment Design; D007834:Lasers; D011312:Pressure; D012680:Sensitivity and Specificity; D014465:Ultrasonics