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Needle-based core-biopsy to locate prostate cancer relies heavily upon trans-rectal
ultrasound (TRUS) imaging guidance. Ultrasonographic findings of classic hypoechoic
peripheral zone lesions have a low specificity of ~28%, a low positive predictive value of ~29%,
and an overall accuracy of ~43%, in prostate cancer diagnosis. The prevalence of isoechoic or
nearly invisible prostate cancers on ultrasonography ranges from 25 to 42%. As a result, TRUS
is useful and convenient to direct the needle trajectory following a systematic biopsy sampling
template rather than to target only the potentially malignant lesion for focal-biopsy. To address
this deficiency in the first-line of prostate cancer imaging, a trans-rectal ultrasound-coupled
spectral tomography (TRUST) approach is being developed to non-invasively resolve the likely
optical signatures of prostate malignancy. The approach has evolved from using one NIR
wavelength to two NIR bands, and recently to three bands of NIR spectrum information. The
concept has been evaluated on one normal canine prostate and three dogs with implanted prostate
tumor developed as a model. The initial results implementing TRUST on the canine prostate
tumor model includes: (1) quantifying substantially increased total hemoglobin concentration
over the time-course of imaging in a rapidly growing prostate tumor; (2) confirming hypoxia in a
prostatic cystic lesion; and (3) imaging hypoxic changes of a necrotic prostate tumor. Despite
these interesting results, intensive technologic development is necessary for translating the
approach to benefiting clinical practice, wherein the ultimate utility is not possibly to eliminate
needle-biopsy but to perform focal-biopsy that is only necessary to confirm the cancer, as well as
to monitor and predict treatment responses.
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