Improved delineation with diffusion weighted imaging for laryngeal and hypopharyngeal tumors validated with pathology.

Objective: This study aims to determine the added value of a geometrically accurate diffusion-weighted (DW-) MRI sequence on the accuracy of gross tumor volume (GTV) delineations, using pathological tumor delineations as a ground truth.
Methods: Sixteen patients with laryngeal or hypopharyngeal carcinoma were included. After total laryngectomy, the specimen was cut into slices. Photographs of these slices were stacked to create a 3D digital specimen reconstruction, which was registered to the in vivo imaging. The pathological tumor (tumor _HE ) was delineated on the specimen reconstruction. Six observers delineated all tumors twice: once with only anatomical MR imaging, and once (a few weeks later) when DW sequences were also provided. The majority voting delineation of session one (GTV _MRI ) and session two (GTV _DW-MRI ), as well as the clinical target volumes (CTVs), were compared to the tumor _HE .
Results: The mean tumor _HE volume was 11.1 cm ³ , compared to a mean GTV _MRI volume of 18.5 cm ³ and a mean GTV _DW-MRI volume of 15.7 cm ³ . The median sensitivity (tumor coverage) was comparable between sessions: 0.93 (range: 0.61-0.99) for the GTV _MRI and 0.91 (range: 0.53-1.00) for the GTV _DW-MRI . The CTV volume also decreased when DWI was available, with a mean CTV _MR of 47.1 cm ³ and a mean CTV _DW-MRI of 41.4 cm ³ . Complete tumor coverage was achieved in 15 and 14 tumors, respectively.
Conclusion: GTV delineations based on anatomical MR imaging tend to overestimate the tumor volume. The availability of the geometrically accurate DW sequence reduces the GTV overestimation and thereby CTV volumes, while maintaining acceptable tumor coverage.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
(Copyright © 2024 The Author(s). Published by Elsevier B.V. All rights reserved.)