Evaluation of PET/MRI for Tumor Volume Delineation for Head and Neck Cancer

Abstract

IntroductionComputed tomography (CT), combined positron emitted tomography and CT (PET/CT), and magnetic resonance imaging (MRI) are commonly used in head and neck radiation planning. Hybrid PET/MRI has garnered attention for potential added value in cancer staging and treatment planning. Herein, we compare PET/MRI vs. planning CT for head and neck cancer gross tumor volume (GTV) delineation.Material and methodsWe prospectively enrolled patients with head and neck cancer treated with definitive chemoradiation to 60–70 Gy using IMRT. We performed pretreatment contrast-enhanced planning CT and gadolinium-enhanced PET/MRI. Primary and nodal volumes were delineated on planning CT (GTV-CT) prospectively before treatment and PET/MRI (GTV-PET/MRI) retrospectively after treatment. GTV-PET/MRI was compared to GTV-CT using separate rigid registrations for each tumor volume. The Dice similarity coefficient (DSC) metric evaluating spatial overlap and modified Hausdorff distance (mHD) evaluating mean orthogonal distance difference were calculated. Minimum dose to 95% of GTVs (D95) was compared.ResultsEleven patients were evaluable (10 oropharynx, 1 larynx). Nine patients had evaluable primary tumor GTVs and seven patients had evaluable nodal GTVs. Mean primary GTV-CT and GTV-PET/MRI size were 13.2 and 14.3 cc, with mean intersection 8.7 cc, DSC 0.63, and mHD 1.6 mm. D95 was 65.3 Gy for primary GTV-CT vs. 65.2 Gy for primary GTV-PET/MRI. Mean nodal GTV-CT and GTV-PET/MRI size were 19.0 and 23.0 cc, with mean intersection 14.4 cc, DSC 0.69, and mHD 2.3 mm. D95 was 62.3 Gy for both nodal GTV-CT and GTV-PET/MRI.ConclusionIn this series of patients with head and neck (primarily oropharynx) cancer, PET/MRI and CT-GTVs had similar volumes (though there were individual cases with larger differences) with overall small discrepancies in spatial overlap, small mean orthogonal distance differences, and similar radiation doses.

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Assessment of image quality of a radiotherapy-specific hardware solution for PET/MRI in head and neck cancer patients

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Evaluation of Hybrid PET/MRI for Gross Tumor Volume (GTV) Delineation in Liver Cancer Radiotherapy

“…In addition, spatial analysis within GTV-MRI, GTV-PET and GTV-PET/MRI was performed. The Dice similarity coe cient (DSC) was calculated using the equation: 2 × (A∩B)/(A + B), where A and B represent two volumes, (A∩B) represents the volume of the intersection, and (A + B) represents the absolute sum of their volumes [11].…”

“…In their study, GTV VIS and GTV FUS were larger than GTV MRI with the use of hybrid PET/MRI images, which was similar to our ndings, but tumor site determinations were different. While Wang, K. et al [11] demonstrated that hybrid PET/MRI-and CT-generated GTVs were similar overall and supplied similar radiation doses to the head and neck. Zhang, Shaomin.…”