Objective: The objective of this study was to compare the accuracy of calculating the primary tumor volumes using a gradient-based method and fixed threshold methods on the standardized uptake value (SUV) maps and the net influx of FDG (Ki) maps from positron emission tomography-computed tomography (PET-CT) images.
Materials and Methods: Newly diagnosed patients with head and neck cancer were recruited, and dynamic PET-CT scan and T2-weighted magnetic resonance imaging were performed. The maps of Ki and SUV were calculated from PET-CT images. The tumor volumes were calculated using a gradient-based method and a fixed threshold method at 40% of maximal SUV or maximal Ki. Four kinds of volumes, VOLKi-Gra (from the Ki maps using the gradient-based method), VOLKi-40% (from the Ki maps using the threshold of 40% maximal Ki), VOLSUV-Gra (from the SUV maps using the gradient-based method), and VOLSUV-40% (from the SUV maps using the threshold of 40% maximal SUV), were acquired and compared with VOLMRI (the volumes acquired on T2-weighted images) using the Pearson correlation, paired t test, and similarity analysis.
Results: Eighteen patients were studied, of which 4 had poorly defined tumors (PDT). The positron emission tomography–derived volumes were as follows: VOLSUV-40%, 2.1 to 41.2 cm3 (mean [SD], 12.3 [10.6]); VOLSUV-Gra, 2.2 to 28.1 cm3 (mean [SD], 13.2 [8.4]); VOLKi-Gra, 2.4 to 17.0 cm3 (mean [SD], 9.5 [4.6]); and VOLKi-40%, 2.7 to 20.3 cm3 (mean [SD], 12.0 [6.0]). The VOLMRI ranged from 2.9 to 18.1 cm3 (mean [SD], 9.1 [3.9]). The VOLKi-Gra significantly correlated with VOLMRI with the highest correlation coefficient (PDT included, R = 0.673, P = 0.002; PDT excluded, R = 0.841, P < 0.001) and presented no difference from VOLMRI (P = 0.672 or 0.561, respectively, PDT included and excluded). The difference between VOLKi-Gra and VOLMRI was also the smallest.
Conclusions: The tumor volumes delineated on the Ki maps using the gradient-based method are more accurate than those on the SUV maps and using the fixed threshold methods.
From the *Department of Radiology, Guangzhou Panyu Central Hospital; †Medical Imaging Center, The First Affiliated Hospital of Jinan University, Guangzhou; ‡Department of Radiology, Peking University Shenzhen Hospital, Shenzhen; §Department of Diagnostic Radiology, The University of Hong Kong, Hong Kong Special Administrative Region, China; ∥Department of Radiation Sciences, Radiation Physics, Umeå University, Umeå, Sweden; ¶Department of Radiology, Hospital of Stomatology, Guanghua School of Stomatology; #Department of Radiology, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China; and **Shenzhen University, Shenzhen, China.
Received for publication September 7, 2013; accepted September 23, 2013.
Reprints: Liangping Luo, MD, Medical Imaging Center, The First Affiliated Hospital of Jinan University, Guangzhou, China (e-mail: firstname.lastname@example.org); Bingsheng Huang, PhD, Room 406, Block K, Queen Mary Hospital, 102 Pokfulam Rd, Hong Kong Special Administrative Region, China (e-mail email@example.com).
Supported by The National Natural Science Foundation of China (No. 81301273) and The University of Hong Kong Small Project Funding (No. 201209176182).
The authors declare that they have no conflict of interest.
Authors Chen and Jiang had an equal contribution to this article as co-first authors.