Screening techniques for prostate adenocarcinoma (PCa) have increased diagnostic sensitivity to detect early stage diseases. Techniques such as digital rectal exam and prostate-specific antigen (PSA) tests are effective for identifying patients who are at risk; however, these tests cannot definitively diagnose PCa. Biopsy of the prostate is required for a definitive histopathological diagnosis and is usually critical in providing information that allows the prediction of tumor biology and subsequent clinical management.
During the prostate biopsy procedure an “end-firing”, 2D transrectal ultrasound (TRUS) probe is inserted into the rectum allowing the prostate to be imaged through the rectal wall (FIGS. 1a and 1b). By rotating the probe, the physician can “fan” through the entire prostate gland and guide the biopsy needle to the desired location(s) (See FIG. 2). Unfortunately, early stage PCa is often isoechoiec and not visible under the conventional ultrasound, or tumor foci are microscopic, so physicians are unable to target tumors directly. Instead, biopsy sites are determined pre-biopsy, based on anatomical zones of the prostate that have a higher probability of harboring PCa. Poor sensitivity (˜53%) plagues the prostate biopsy procedure, since tumors are not always targeted directly. Studies have shown PCa detection rates up to 34% on repeat biopsies, after an initial negative biopsy. This inherent inaccuracy may lead to delays in cancer diagnosis and treatment, as well as increased patient anxiety and discomfort due to repeat biopsies.
The current clinical biopsy procedure is confined to using a 2D imaging tool for targeting and recording the 3D biopsy locations. This makes the procedure prone to spatial ambiguity, as the physician tries to envision the 3D location and orientation of their 2D TRUS view within the prostate. This problem is compounded for repeat biopsies, where it is vital that the physician target specific areas in the prostate, either to avoid prior biopsy locations or target them directly—as in the case of lesions, such as atypical small acinar proliferation (ASAP). Repeat biopsies of patients with ASAP in the initial biopsy will result in detection of PCa in 30-50% of cases, with a high probability that the tumor foci is located in the same anatomical region as the ASAP. For these clinical scenarios, the physician's targeting accuracy must be high and consistent, and therefore 3D intra-biopsy prostate information may be essential to increase the detection rate and improve the diagnostic accuracy.