Development of an Innovative Shape Memory Alloy Based Tool for Brachytherapy

Brachytherapy is a type of radiotherapy for localized tumors whereby radio-active substances are placed within or close to the tumor region. The procedure is extremely invasive; in the instance of prostate cancer, up to 20 needles are used to deliver 100 grain-sized capsules (usually ¹²⁵I or ¹⁰³Pd) throughout the prostate. Such a high number of needles increase the risk of damaging the rich bed of blood vessels around the prostate and also cause increased discomfort for the patient, along with other possible complications. Accordingly, an innovative shape memory alloy (SMA) based low dose rate (LDR) brachytherapy tool was designed to address this issue. Curved superelastic nitinol wires were tested on tissue simulants (Perma-gel) in order to investigate how differently curved SMA needles behave in tissue. It was found that the wires were able to create curved shapes in tissue. However, in most cases, tissue relaxation and friction caused discrepancies between the original shape of the wire and the trail it created in tissue. With the ability to create highly curved needle trajectories, it is theoretically possible to significantly reduce the required amount of external punctures normally seen in prostate brachytherapy. This study also opens up the possibility of using radically different seed planning strategies for prostate brachytherapy.