A visual grading analysis-based audit for MR simulation sequence development

Abstract

Purpose or Objective To assess recently implemented MR Simulation protocols used for treatment planning in head and neck patients being treated as part of a newly introduced proton beam radiotherapy (PBT) service. Material and Methods Based on a review of the literature, an imaging protocol comprising four sequences was implemented. Imaging was performed using a 1.5 Tesla (T) magnet, utilising a combination of 32-channel body array, 44-channel spinal array and two large flexible 2-channel transmit receive coils. Table 1 details the sequences used, but in short included 2- and 3 – dimensional acquisitions using turbo spin echo (TSE), driven equilibrium (DRIVE), spectral presaturation with inversion (SPIR) and mDixon sequences. All patients were imaged axially from superior orbital margin to sternal notch in the treatment position. To evaluate image quality and suitability, an audit was undertaken, using a visual grading analysis (VGA). The VGA was based on a 4-point scale, ranging from “very clear” to “not visible” for a series of predetermined structures (table 2) by 3 multidisciplinary team members. Results Sixteen patient datasets were available for review. The preliminary analysis demonstrated a scan time of 31.26 minutes, with a mean ‘in-room’ time of 64.07 minutes (range 24-101 minutes). Using VGA tool, one radiographer, one radiologist and one clinical oncologist reviewed images (Table 1). Overall, an average of 69.4% of the sequences and structures were reported as “very clear” or “clear” (range 57.1-87.3%) (Table 2). The T2W TSE mDixon and T1 SPIR with intravenous contrast were the 2 sequences that scored the highest. The 3D T2W DRIVE sequence came out as unclear or had structures that weren’t visible in nearly 43% of the cases. Conclusion Based on our analysis, the most appropriate sequences for planning PBT for head and neck tumours are a combination of T2W TSE mDixon and T1 SPIR with intravenous contrast. Considering clarity of named anatomical structures has facilitated an optimisation process of individual sequences. Using interdisciplinary VGA as an audit tool, we have implemented a continuous quality improvement (CQI) process for PBT treatment planning in head and neck cancers using MR. We anticipate this process will soon be implemented for other treatment sites at our institution. This philosophy of CQI will ensure sequence selection is evidence-based, the inclusion of appropriately selected sequences, and the removal of sequences felt to be less useful.