Abstract
Optoacoustic (OA) imaging was employed to distinguish normal from neoplastic tissues in a transgenic murine model of prostate cancer. OA images of five tumor-bearing mice and five age-matched controls across a 14 mm × 14 mm region of interest (ROI) on the lower abdomen were acquired using a reverse-mode OA imaging system (Seno Medical Instruments Inc., San Antonio, Texas). Neoplastic prostate tissue was identified based on the OA signal amplitude in combination with spectral analysis of the OA radio frequency (RF) data. Integration of the signal amplitude images was performed to construct two-dimensional images of the ROI. The prostate tumors generated higher amplitude signals than those of the surrounding tissues, with contrast ratios ranging from 31 to 36 dB. The RF spectrum analysis showed significant differences between the tumor and the control mice. The midband fit was higher by 5 dB (62%), the intercept higher by 4 dB (57%) and the spectral slope higher by 0.4 dB/MHz (50%) for neoplastic prostate tissue compared to normal tissues in the control mice. The results demonstrate that OA offers high contrast imaging of prostate cancer in vivo.
Highlights
Conventional imaging techniques for prostate cancer, such as ultrasound, computed tomography, and magnetic resonance imaging, are used to identify abnormal areas in the prostate that are biopsied for a definitive diagnosis
One of the most common techniques used for local grading of the prostate is transrectal ultrasound (TRUS) because it can be performed in real time
Recent techniques have been developed that probe tissue microstructure based on the spectral analysis of radio frequency (RF) data;[8,9] these ultrasonic techniques do not provide any information on the oxygen saturation or hemoglobin concentration of the tissue, both of which are often altered with neoplasia.[10,11]
Summary
Conventional imaging techniques for prostate cancer, such as ultrasound, computed tomography, and magnetic resonance imaging, are used to identify abnormal areas in the prostate that are biopsied for a definitive diagnosis. These imaging techniques do not reliably distinguish neoplastic from healthy prostate tissue,[1] leading to the large sampling error associated with biopsies. TRUS systems that utilize transducers in the 5 to 7 MHz range[3] can provide an acceptable resolution of 0.3 to 0.5 mm.[4] the accuracy of this technique is reported to be less than 50% to 60% with respect to the detection of prostate cancer, due largely to the weak contrast at depth in soft tissues.[5,6,7] Conventional diagnosis is currently based solely on the detection of gross anatomic properties of tissues. Recent techniques have been developed that probe tissue microstructure based on the spectral analysis of radio frequency (RF) data;[8,9] these ultrasonic techniques do not provide any information on the oxygen saturation or hemoglobin concentration of the tissue, both of which are often altered with neoplasia.[10,11] Pure optical imaging techniques, such as diffuse optical tomography (DOT), are being investigated as possible targeting technologies for prostate cancer because of their ability to achieve
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