KoMBUS – MR-compatible ultrasound for improved biopsy needle guidance

Biopsies have become an essential tool for minimally invasive diagnostics and are part of the daily routine of interventional radiologists. Depending on the target organ that has to be sampled, different imaging modalities such as CT, ultrasound or MRI can be used. In particular, when it comes to detection of small tumors having a low contrast in ultrasound or CT, MRI is the method of choice. The risk for being off-target leading to a potentially false-negative diagnosis is reduced due to the better contrast on MR images. However, MRI still has drawbacks when compared to ultrasound with respect to cost issues, patient comfort and time-resolution.

The goal of KoMBUS therefore is to develop MR-compatible ultrasound hardware allowing to replace MRI by ultrasound to the greatest possible extent in the context of biopsy guidance. In this concept, a diagnostic MRI scan will be performed prior to the biopsy with a simultaneous 3D US scan of the ROI. The latter will be used to autonomously follow the tissue motion and deformation (e.g. as a result of breathing) based on the tracking of defined tissue landmarks. The fusion of the initial MR data and the real-time tracking information derived from US data allows to generate synthetic MR data sets, which reflect the current anatomical situation. If the ultrasound probe is connected to a mechanical needle guiding system, our therapy planning software module will calculate the accurate needle path for a defined target and a corresponding breathing phase. The concept will allow precise biopsies while only needing one initial MRI scan, which reduces the patient discomfort associated with repetitive MR-scans during the biopsies and saves MR time.

In view of the clinical validation of this concept, an MR compatible ultrasound platform consisting of a 256 channel system, different MR-compatible probes and an MR-compatible touchscreen has been developed. For tracking of the organ deformation, an 11 × 11 elements matrix array probe for acquisition of volume data that will be fed in our motion tracking algorithms, has been developed. The development and characterization of our hard- and software will be presented as well as first measurements on phantoms. Furthermore, a clinical validation of the concept is in preparation and the first tests for compliance with the medical device directive have been performed.