Rapid fabrication of custom patient biopsy guides

Image‐guided surgery is currently performed using frame‐based as well as frameless approaches. In order to reduce the invasive nature of stereotactic guidance and the cost in both equipment and time required within the operating room, we investigated the use of rapid prototyping (RP) technology. In our approach, we fabricated custom patient‐specific face masks and guides that can be applied to the patient during stereotactic surgery. While the use of RP machines has previously been shown to be satisfactory from an accuracy standpoint, one of our design criteria – completing the entire build and introduction into the sterile field in less than two hours – was unobtainable.(1) Our primary problems were the fabrication time and the nonresistance of the built material to high‐temperature sterilization. In the current study, we have investigated the use of subtractive rapid prototyping (SRP) machines to perform the same quality of surgical guidance, while improving the fabrication time and allowing for choosing materials suitable for sterilization. Because SRP technology does not offer the same flexibility as RP in terms of prototype shape and complexity, our software program was adapted to provide new guide designs suitable for SRP fabrication. The biopsy guide was subdivided for a more efficient build with the parts being uniquely assembled to form the final guide. The accuracy of the assembly was then assessed using a modified Brown‐Roberts‐Wells phantom base by which the position of a biopsy needle introduced into the guide can be measured and compared with the actual planned target. These tests showed that: 1) SRP machines provide an average technical accuracy of 0.77 mm with a standard deviation of the mean of 0.07 mm, and 2) SRP allows for fabrication and sterilization within three‐and‐a‐half hours after diagnostic image acquisition. We are confident that technology is capable of reducing this time to less than one hour. Further tests are being conducted to determine the registration accuracy of the face mask on the patient's head under IRB‐approved trials. The accuracy of this new guidance technology will be verified by judging it against current frame‐based or frameless systems. PACS number: 87.57.Gg