Implementation of a dedicated 1.5 T MR scanner for radiotherapy treatment planning featuring a novel high-channel coil setup for brain imaging in treatment position

Abstract

Purpose To share our experiences in implementing a dedicated magnetic resonance (MR) scanner for radiotherapy (RT) treatment planning using a novel coil setup for brain imaging in treatment position as well as to present developed core protocols with sequences specifically tuned for brain and prostate RT treatment planning. Materials and methods Our novel setup consists of two large 18-channel flexible coils and a specifically designed wooden mask holder mounted on a flat tabletop overlay, which allows patients to be measured in treatment position with mask immobilization. The signal-to-noise ratio (SNR) of this setup was compared to the vendor-provided flexible coil RT setup and the standard setup for diagnostic radiology. The occurrence of motion artifacts was quantified. To develop magnetic resonance imaging (MRI) protocols, we formulated site- and disease-specific clinical objectives. Results Our novel setup showed mean SNR of 163 ± 28 anteriorly, 104 ± 23 centrally, and 78 ± 14 posteriorly compared to 84 ± 8 and 102 ± 22 anteriorly, 68 ± 6 and 95 ± 20 centrally, and 56 ± 7 and 119 ± 23 posteriorly for the vendor-provided and diagnostic setup, respectively. All differences were significant (p > 0.05). Image quality of our novel setup was judged suitable for contouring by expert-based assessment. Motion artifacts were found in 8/60 patients in the diagnostic setup, whereas none were found for patients in the RT setup. Site-specific core protocols were designed to minimize distortions while optimizing tissue contrast and 3D resolution according to indication-specific objectives. Conclusion We present a novel setup for high-quality imaging in treatment position that allows use of several immobilization systems enabling MR-only workflows, which could reduce unnecessary dose and registration inaccuracies.

Image quality comparisons of coil setups in 3T MRI for brain and head and neck radiotherapy simulations

“…The SNR observations for a T1 and T2‐weighted TSE and a STIR sequence in our work generally agreed with SNR comparisons between a similar UFL18 and a FL4 coil setup reported by Mengling et al 13 . for a T1‐weighted MPRAGE and a T2‐weighted FLAIR sequence.…”

Adaptive Proton Therapy of Pediatric Head and Neck Cases Using MRI-Based Synthetic CTs: Initial Experience of the Prospective KiAPT Study

“…This could lead to inaccuracies in positioning, especially in the neck, and subsequently in the registration. As result, the anatomical changes could be underestimated, which in turn could affect the replanning accuracy [ 47 , 48 ]. Recent studies demonstrate the use of immobilization equipment in the MRI [ 26 , 48 ].…”

“…As result, the anatomical changes could be underestimated, which in turn could affect the replanning accuracy [ 47 , 48 ]. Recent studies demonstrate the use of immobilization equipment in the MRI [ 26 , 48 ].…”

Feasibility of artificial-intelligence-based synthetic computed tomography in a magnetic resonance-only radiotherapy workflow for brain radiotherapy: Two-way dose validation and 2D/2D kV-image-based positioning

“…MRIs were acquired at the MAGNETOM Sola (1.5 T, Siemens Healthineers, Erlangen, Germany) using a dedicated RT setup. The RT setup included the use of a flat RT table-top, an immobilization RT mask system, and a dedicated coil setup of two 18 channels Ultraflex coils (further details see [29] ). After 20 patients, refinements were made to the RT mask holder for MRI acquisition to increase rotational accuracy compared to treatment position.…”

“…The first network segments the MRI in three classes (background, bone, soft tissue), while the second network uses Generative Adversarial Network to generate sCT with continuous HU and discriminates it from a real CT image. In the TPS, the HU look-up table as recommended by the vendor [29] was used. Each sCT was first rigidly registered to the corresponding CT, followed by copying the identical clinical structures from the CT onto the sCT.…”