A medical needle drive for the study of interstitial implant mechanics

We describe the construction and test performance of a computer-controlled medical needle drive. The drive represents one facet of a larger project whose aim is to investigate experimentally the mechanics of needle introduction in radioactive 'seed' prostate implants, with a view to identifying ways of making incremental improvements in needle placement accuracy. It is capable of mimicking a range of motions imparted to a needle by a clinical practitioner, and of monitoring the compressive force at the needle tip in real time via an in-line load cell. Tests involving driving needles into porcine gelatin samples using a variety of velocity profiles confirm intended operation. The drive will permit us to introduce needles in a controlled and reproducible manner into a realistic prostate phantom currently being designed.