Evaluation of Frequency Domain Analysis of a Multiwavelength Photoacoustic Signal for Differentiating Malignant From Benign and Normal Prostates

Abstract

Objectives The purpose of this study was to investigate the feasibility of differentiating malignant prostate from benign prostatic hyperplasia (BPH) and normal prostate tissue by performing frequency domain analysis of photoacoustic images acquired at 2 different wavelengths. Methods We performed multiwavelength photoacoustic imaging on freshly excised human prostate specimens taken from a total of 30 patients undergoing prostatectomy for biopsy-confirmed prostate cancer. Histologic slides marked by a genitourinary pathologist were used as ground truth to define regions of interest (ROIs) in the photoacoustic images. Primarily, 3 different prostate tissue categories, namely malignant, BPH, and normal, were considered, while a fourth category named nonmalignant was formed by combining the ROIs corresponding to BPH and normal tissue together. We extracted 3 spectral parameters, namely slope, midband fit, and intercept, from power spectra of the radiofrequency photoacoustic signals corresponding to the 3 primary tissue categories. Results We analyzed data from 53 ROIs selected from the photoacoustic images of 30 patients. According to the histopathologic analysis, 19 ROIs were malignant, 8 were BPH, and 26 were normal. All the 3 spectral parameters and C-scan grayscale photo - acoustic image pixel values were found to be significantly different (P < .01) between malignant and nonmalignant prostate as well as malignant and normal prostate. Conclusions Preliminary results of our ex vivo human prostate study suggest that spectral parameters obtained by performing frequency domain analysis of photoacoustic signals can be used to differentiate between malignant and nonmalignant prostate.

Interstitial assessment of aggressive prostate cancer by physio‐chemical photoacoustics: An ex vivo study with intact human prostates

“…Therefore, the superficial illumination approach used in our previous studies is not applicable in the in vivo prostate imaging scenario. Most of the previous studies on the PA imaging of prostate cancer were performed with sliced prostate tissues ex vivo . Our recently developed needle PA probe facilitates the delivery of relatively uniform illumination along a fiber optic diffuser, and the reception of the high frequency PA signals with a needle hydrophone from nearby tissues .…”

Photoacoustic imaging of prostate cancer

“…Exploiting the spectrum of PA signal amplitude at a range of PA wave frequency, frequency domain analysis has shown potential in determining important parameters, such as the size and concentration, of the optical absorber and thus enabling the quantitative characterization of the prostate tissue, as demonstrated by Kumon et al, Sinha et al, and Patterson et al [87][88][89] Several challenges, however, are faced in the development of both PAI spectroscopy and frequency domain analysis towards clinical implementation. The spectral parameters are likely to be di®erent in an in vivo system, due to the overlying tissue; the algorithm for chromophore PA image reconstrucion is more complicated in reality, given that there are more components than dHb, HbO 2 , lipids, and water in biological tissues.…”

“…The spectral parameters are likely to be di®erent in an in vivo system, due to the overlying tissue; the algorithm for chromophore PA image reconstrucion is more complicated in reality, given that there are more components than dHb, HbO 2 , lipids, and water in biological tissues. 88,90 Additionally, in going from a 1D transducer to a 2D or 3D transducer array used in in vivo prostate imaging, the di±culty in image processing must be overcome. 88 Although studies have shown e®ective endogenous contrast for tumor visualization, these biological ¼ 800 nm, 6 Â 12 mm).…”

“…88,90 Additionally, in going from a 1D transducer to a 2D or 3D transducer array used in in vivo prostate imaging, the di±culty in image processing must be overcome. 88 Although studies have shown e®ective endogenous contrast for tumor visualization, these biological ¼ 800 nm, 6 Â 12 mm). PA images on days 9 and 16 revealed a map and progression of the vascular network.…”

Frequency Domain Analysis of Multiwavelength Photoacoustic Signals for Differentiating Among Malignant, Benign, and Normal Thyroids in an Ex Vivo Study With Human Thyroids

“…Using simulation and experiments involving osteoporotic rat femoral heads, Feng et al explored the capability of photoacoustic spectral parameters to perform bone microstructure characterization. Sinha et al differentiated among malignant, benign, and normal prostate tissue using photoacoustic spectral parameters in an ex vivo multiwavelength photoacoustic study with actual human patients. In an ex vivo study, Xu et al used a frequency domain analysis of photoacoustic signals for fatty liver diagnosis in a mouse model.…”