Program Information
End-To-End Phantom Evaluation for Transition From MR/CT Combined to MR-Only Workflow
J.M. Cunningham1,2*, C Glide-Hurst1,2 , (1)Wayne State University, Detroit, MI (2) Henry Ford Health System, Detroit, MI
Presentations
SU-I-GPD-J-84 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall
Purpose: As we move toward MR-only treatment planning, a need exists to distinguish discrepancies between MR-only and MR/CT combined workflows. We evaluated a new MR-safe stereotactic head phantom for its performance for end-to-end testing for MR-SIM.
Methods: We require a phantom that can mimic the entire MR-SIM workflow including: setup in site-specific coils, data acquisition using the same sequences, isocenter marking, synthetic CT generation or co-registration for MR/CT combined, planning, and delivery with dosimetric measurements. The head phantom was immobilized using an MR-compatible headrest and external MR/CT fiducials were aligned to the magnet laser system. 1.0T brain MR-SIM scans (T1-weighted, T2-weighted, FLAIR, and UTE-Dixon) were acquired using an 8-channel head coil. An MRI/CT target insert (12.5 cc volume) was filled with signal generator fluid and embedded in a ~380 cc water-filled cube insert. CT-SIM was conducted using the same setup. Images were transferred to the treatment planning system and rigid registration was performed.
Results: The head phantom was challenging to align in MR-SIM due to the head coil and irregular posterior phantom surface. While the phantom includes a custom-made cradle, it would not fit in the head coil. Setup was more straightforward in CT-SIM. MR/CT compatible fiducial landmarks were visible in both modalities. The target insert was visible and exhibited contrast from the water-filled cube. Co-registered images illustrated strong agreement between MR and CT images. However, much of the phantom did not yield visible MR signal, suggesting that generation of a synthetic CT is not possible. In addition, dosimetric measurements would be challenging to obtain in the fluid-filled inserts.
Conclusion: The MR/CT compatible phantom may evaluate the geometric integrity of simulation although it will not test all of the unique requirements for MR-only planning. Further development is warranted as we move toward an entirely MR-based workflow including MR-IGRT.
Funding Support, Disclosures, and Conflict of Interest: Research supported by the National Cancer Institute of the National Institutes of Health under Award Number R01CA204189. The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH. C. Glide-Hurst acknowledges funding from HFHS Internal Mentored Grant and Philips Healthcare.
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