In soft-tissue cancer, the initial diagnosis is often obtained by imaging systems (e.g. Magnetic Resonance Imaging - MRI). If tumorous tissues are indicated, a biopsy is performed to acquire tissue samples for histopathological examination. The biopsy is typically carried out by an experienced physician under control of an imaging system (e.g. Ultrasound - US) that shows the examined area as the samples are collected. US guided prostate biopsy after MRI diagnosis is a common example of such a procedure.
In this project, we decided to focus mainly on prostate biopsy, as one in seven men is diagnosed with prostate cancer in their lifetime. The initial diagnosis is typically done with a time-consuming MRI that provides images with good contrast between pathological and healthy tissue. The US imaging systems used for real-time guidance of the biopsy device is fast, but the image does not allow to discriminate the soft tissues inside the prostate. The physician needs to use a technique called cognitive biopsy: he has to mentally match the 3D MRI image acquired beforehand with the 2D US acquired in real time to guide the device to the targeted location. Despite the fact that 12 samples are typically taken, it is still possible to miss the tumor tissue due to the lack of proper registration between image modalities. With each subsequent puncture, the correlation between the MRI and US images decreases as a result of deformation and damage to soft tissues. This leads to false-negative histopathology results that hinder the therapy: the procedure needs to be repeated, and the treatment is delayed, decreasing the patient's chance of recovery. The false-negative rate of prostate biopsy varies from 17 to 21%, in patients with a negative first series of biopsies.