Transurethral photoacoustic and ultrasonic endoscopic probe developed for bladder cancer diagnosis

The minimally invasive application of photoacoustic (optoacoustic) tomography (PAT) has been mainly focused on gastrointestinal endoscopy and the imaging of cardiovascular and reproductive systems, such as the uterus, ovaries, and prostate, in relation to the diagnosis of atherosclerotic plaques (e.g., in coronary arteries) and reproductive cancers. However, the miniature probe technology involved could also make a considerable contribution to the diagnosis and post-treatment follow-ups of urinary diseases. PAT can provide a variety of anatomical, functional, and molecular information that is not producible with conventional imaging methods, such as MRI and ultrasound. Among the related clinical issues, the development of a new diagnostic paradigm for the early detection of bladder cancer is urgently needed, because it is known to be very aggressive and lethal if found after stage 2 (T2). In this study, we developed a transurethral photoacoustic and ultrasonic endoscopic probe with an outer diameter of 2.8 mm to contribute to the early diagnosis of bladder cancer in clinical urology. From a live rabbit, we successfully acquired the first high-resolution 3D vasculature map of more than 50% of the bladder wall, which we believe is a completely new type of image information never acquired before from a vertebrate urinary system.