A review of co-registered transvaginal photoacoustic and ultrasound imaging for ovarian cancer diagnosis

Ovarian cancer is the deadliest of all gynecological malignancies. When ovarian cancer is detected at an early, localized stage, surgery and chemotherapy can cure 70%–90% of patients, compared with 20% or fewer when it is diagnosed at later stages. Clearly, early detection is critical, yet the lack of early symptoms and effective screening tools means that only 20–25% of ovarian cancers are diagnosed early. Photoacoustic imaging (PAI) is an emerging modality that uses a short-pulsed laser to excite tissue. The resulting photoacoustic waves are used to image tissue optical contrast, which is directly related to tissue microvasculature and thus to cancer growth. When co-registered with transvaginal ultrasound (US), PAI offers great promise in diagnosing earlier stage ovarian cancers and distinguishing benign processes from malignant ovarian masses. In this article, we review the limitations of the current imaging tools for early ovarian cancer diagnosis and present recent advances in co-registered PAI/US.