서강대학교

초록/요약

Although transrectal ultrasound (TRUS) imaging is widely used for screening and diagnosing prostate cancer, prostate cancer is often not found on TRUS images, depending on its stage, size, and location. Additionally, due to the weak echo signal and the low contrast of TRUS images, it is difficult to diagnose early-stage prostate cancers and distinguish malignant tumors from benign prostatic hyperplasia. For this reason, TRUS image-guided biopsy is mandatory to confirm the malignancy of the suspicious tumor, but the diagnostic accuracy of initial biopsy is only 20 to 30% so that the patients inevitably undergo repeated biopsies. Transrectal ultrasound-photoacoustic (TRUS-PA) imaging is one way to resolve those problems. However, the development of a TRUS-PA probe, in which an ultrasound array transducer and optical fibers are integrated, is demanding because the overall size of the probe should be as small as possible for the convenience of the patients while providing the desired performances. The objective of this dissertation was to develop a miniaturized TRUS-PA probe for the US and PA imaging to improve diagnostic accuracy and biopsy accuracy of prostate cancer. This aims to overcome the cause of poor diagnostic accuracy by providing a clear PA image of early cancer, morphological changes, including angiogenesis, and biopsy needle for guidance. In addition, identification of the suspicious lesions and targeted biopsy for minimal extracted biopsy cores were finally set to the goal to reduce the repetitive biopsy. This dissertation discusses the development of the miniaturized TRUS-PA probe for the combined ultrasound and photoacoustic imaging of the prostate. A miniaturized TRUS transducer was initially developed to overcome the problem of the increase in the external size while satisfying the clinical requirements. RUS transducer could be used in the transrectal application in spite of the small aperture size. Subsequently, the optical lens based PA imaging scheme was developed for the minimal increase in the external size when integrating the US transducer and optical fiber. The optical lens was numerically modeled using ray tracing technique and it was designed, fabricated and evaluated. The performance evaluation results with and without the optical lens were significantly different in optical energy distribution. The prototype of the miniaturized TRUS-PA probe was completed by combining the developed TRUS transducer and optical lens based scheme in the custom-made housing assembly. In the PA imaging, the optical lens based scheme demonstrated the usefulness compared to the PA imaging scheme without an optical lens. Additionally, using the porcine intestine which mimicked the human rectum wall, both ex vivo and in vivo were evaluated to be able to image the specific molecules. Finally, the signal and imaging processing algorithms for detection of the biopsy needle and tip was proposed, implemented, and validated using the ex vivo experiments.