Comparative study of gross tumor volume shown on MRI and FDG PET/CT of nasopharyngeal carcinoma

Abstract

Objective To compare gross tumor volume (GTV) of nasopharyngeal carcinoma (NPC) according to MRI and FDG PET/CT and to investigated four fixed threshold methods to delineate the GTV using FDG PET/CT.Methods Fifty patients with primary biopsy-proven NPC were prospectively were enrolled into the study.FDG PET/CT scans and MRI were carried out within one week prior to pretreatment,respectively.The GTV was named GTV-MRI (GTV were delineated according to MRI),GTV-PETvis,GTV-PET30,GTV-PET40,GTV-PET50 (GTV was delineated according to the PET-based GTVs obtained by visual interpretationor,by percentage of the SUVmax (30％,40％,50％) thresholds,respectively).The differences were compared among the GTV-MRI,GTV-PETvis,GTV-PET30,GTV-PET40 and GTV-PET50 in different by Wilcoxon test.Results Of 50 patients,the median of volume descending order were: GTV-MRI 27.8 cm3,GTV-PETvis 22.2 cm3,GTV-PET30 22.7 cm3,GTV-PET40 14.4 cm3 and GTV-PET50 9.0 cm3.However,there was no significant difference between GTV-PETvis and GTV-PET30 (Z=-0.05,P=0.958),as well as GTV-MRI and GTV-PETvis or GTV-PET30 in 25 patients who were T1-2 stage (Z =-0.93,-0.93,P=0.353,O.353),the other GTVs were all different in 50 patients' (Z=-5.74-2.09,P =0.000-0.037).Conclusions All the GTVs delineated by the different methods of using FDG PET/CT were less than the GTV delineated by MRI.The potential advantages with the GTV-PETvis or GTV-PET30 delineated by FDG PET/CT are reduction of biological metabolic tumor volume in GTV delineation and reduction of the size of the GTV in NPC patients. Key words: Magnetic resonance imaging; Tomography,positron-emission; Tomography,X-ray computed; Nasopharyngeal neoplasms; Gross tumor volume delineate