ESTRO 2024 - Abstract Book

S3851

Physics - Image acquisition and processing

ESTRO 2024

Figure 1: Comparison of the pathological tumor volume (tumor HE ) and the majority voting GTV delineation with and without DW-SPLICE imaging (GTV MRI and GTV DW-MRI , respectively).

Figure 2: T1 with gadolinium, DW-SPLICE b800 image, and the apparent diffusion coefficient (ADC) map of a hypopharyngeal T4 tumor (patient 4) with tumor HE in green, GTV MRI in red and GTV DW-MRI in blue. The availability of DW-SPLICE reduced the GTV volume by 4.5 cm3 (17.6%) in this patient, while a good sensitivity was maintained (0.98 for GTV MRI and 0.96 for GTV DW MRI ). Differences in delineations between scans are caused by resampling due to a difference in slice thickness. In most cases, adding DWI had a positive effect on the accuracy of the tumor delineation, Figure 2. The median PPV increased from 0.50 (range: 0.22-0.86) to 0.61 (range: 0.36-0.85) for GTV MRI and GTV DW-MRI , respectively, while the median sensitivity was comparable between sessions: 0.93 (range: 0.61-0.99) for the GTV MRI and 0.91 (range: 0.54-1) for the GTV DW-MRI .

As the delineated volume decreased, the median type I HD95 increased when DWI was available from 0.7 mm (range: 0-7.3 mm) to 1.4 mm (range: 0-6.6 mm) for the GTV MRI and GTV DW-MRI , respectively.

As for the IOV, the CI gen from all six observers was comparable for delineation sessions with and without DWI, with a median C Igen of 0.65 (range: 0.41-0.74) in the first session, and 0.64 (range: 0.41-0.72) in the DWI session.

Conclusion: