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Development and Preliminary Evaluation of a Motorized Needle Guide Template for MRI-guided Targeted Prostate Biopsy

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Song, S.-E. ; Tokuda, J. ; Tuncali, K. ; Tempany, C.M. ; Zhang, E. ; Hata, N.
Volume: 60, Issue:11, Page: 3019 – 3027

Harvard Medical School Song-Hata-figure

To overcome the problems of limited needle insertion accuracy and human error in the use of a conventional needle guide template in MRI-guided prostate interventions, we developed a motorized MRI-compatible needle guide template driven by two ultrasonic motors. The device is designed for MRI-guided transperineal prostate biopsy, which enables automated, gapless needle insertion position guidance in a 3T MRI scanner, and improves workflow of the current clinical procedure. To evaluate the impact of the motorized template on MR images, signal-to-noise ratio and distortion were measured under various system configurations (baseline, device in place, cable in place, system connected, system ready, and motors running). A maximum of 44% signal-to-noise ratio decrease was found when the ultrasonic motors were running. We concluded that this image degradation will not affect the biopsy procedure since MR images to assess needle position are only acquired when the motors are not running. Within the targeting volume, only a maximum of 0.4% image distortion was observed due to the presence of the motorized template. To measure needle insertion accuracy, we performed four sets of five random target needle insertions into a phantom mimicking four biopsy procedures. This study resulted in an average in-plane targeting error of 0.94 mm with a standard deviation of 0.34 mm. Our results suggested that the presence and operation of the motorized template in the MRI bore creates insignificant image degradation, and provides submillimeter targeting accuracy. The automated needle guide that is directly controlled by navigation software eliminates human error and improves procedural safety.


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