Photoacoustic Imaging for Prostate Brachytherapy

Photoacoustic (PA) imaging was explored as a promising technique for detecting brachytherapy seeds in prostate brachytherapy due to its high contrast from the metallic seeds' absorption. However, its effectiveness was limited by the imaging depth due to optical attenuation in tissue. The study tested methods to enhance PA contrast, including coating seeds with contrast-enhancing materials, which increased the signal-to-noise ratio (SNR) by 18 dB and doubled imaging depth to 5 cm. Silver coating improved SNR by 5 dB, and using dyed ethanol solution between seeds showed comparable improvements. Additionally, a novel method for tissue typing was proposed, utilizing temperature-induced changes in tissue parameters like the speed of sound. Experiments showed distinct PA intensity changes in porcine liver and bovine fat, suggesting potential for tissue differentiation.