A biopsy system that can automatically sample and remove prostate biopsy samples

Abstract

Suspicion of prostate cancer is based on diagnostic tests such as Prostate-Specific-Antigen (PSA) screening or a Digital-rectal-exam. Prostate needle biopsy can be performed to confirm the diagnosis and determine the stage of the disease. The golden standard in prostate biopsy is the trans-rectal biopsy under ultra-sound guidance (TRUS). TRUS is a relative cost-effective approach, though it has the limitation of having a low prostate cancer detection rate (PCa). A succesfull alternative approach is the trans-perineal (TP) biopsy under MRI guidance. Physicians often use this approach for rebiopsies. In contrast to TRUS, TP under MRI guidance is quite expensive. An MRI-safe biopsy system that can automatically sample, remove and store multiple biopsy samples can make TP procedure under MRI guidance more time-efficient. This thesis tackled several challenge related to the development of such an automatic biopsy system.
First of all, the tissue sample should be removed from the biopsy needle without human intervention. The State of the Art research showed that vacuum-suction was the dominant removing technique in breast biopsy. In this thesis, vacuum-suction was not used for the automatic biopsy system. On the grounds that vacuum-suction only proved to be viable with 13G needles and not with 18G or smaller needles. Therefore, a novel technique to remove a tissue samples from a biopsy needle was developed. Flushing with saline showed to have potential during several pilot tests. The second challenge was to fire and reload the biopsy needle without human intervention. A concept was created that implemented both the first and second challenge. Here, a pneumatic cylinder both fired and reloaded the stylet. A compression spring fired the cannula while two pneumatic cylinder ensured automatic reloading. The concept was realized in a Proof of Principle prototype. The prototype was verified against the product specifications (PS). The PS were related to the stylet and cannula velocity, the tissue sample quality and the removing of the tissue sample. As sampling on live human prostate was not possible at this stage of the product development, sampling was done on raw chicken breasts. The samples were compared to the ones taken with a standard 18 biopsy needle. The results showed that the velocity of the stylet was acceptable, while those of the cannula was insufficient. This did not result in a reduction of the sample quality though. Surprisingly, the results showed the exact opposite. The samples taken with the automatic biopsy system were significantly longer that the ones taken with the standard biopsy needle. A tissue sample might appear to be longer if the parts of a fragmented samples are compressed together. This could be a explanation for the surprisingly increase of sample length. The automatic biopsy system presented in this thesis project had a fragmentation rate of 20%. This figure is already twice as low compared the vacuum technique. All this was accomplished with a two times smaller diameter. This thesis project showed the potential of the automatic biopsy system that uses flushing to remove the tissue sample from the biopsy needle.