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Defining PET tumor volume in cervical cancer with hybrid PET/MRI: a comparative study

Zhang, Shaomina; Xin, Juna; Guo, Qiyonga; Ma, Jietaob; Ma, Quanmeia; Sun, Hongzana; Zhao, Xunac

Nuclear Medicine Communications: July 2014 - Volume 35 - Issue 7 - p 712–719
doi: 10.1097/MNM.0000000000000113
Original Articles

Objective The aim of the study was to determine the standardized uptake value (SUV) threshold on gross tumor volume from PET images (PET-GTV) that generates the maximal spatial overlap with MRI-defined GTV (MR-GTV) in locally advanced cervical cancer with the aid of hybrid PET/MRI.

Materials and methods Twenty-seven patients with cervical carcinomas underwent 18F-FDG PET/MRI before radiotherapy. MR-GTV was manually outlined on T2-weighted MRI. PET-GTVs were contoured on PET images using visual inspection (PETvis-GTV), 2.5 SUV (PET2.5-GTV) and 40% SUVmax threshold (PET40-GTV), and compared with MR-GTV. All PET data were reviewed again. The PET-GTV was determined, with the SUVmax threshold defined as the value at which the Dice similarity coefficient (DSC) between PET-GTV and MR-GTV was maximal (PETdsc-GTV). Results were analyzed by Pearson’s analysis, the t-test, and one-way analysis of variance.

Results The mean PETvis-GTV, PET40-GTV, and PET2.5-GTV were significantly different from the mean MR-GTV. The average DSCs were 0.64, 0.65, and 0.68 for PETvis-GTV, PET40-GTV, and PET2.5-GTV with MR-GTV, respectively. The mean threshold of PETdsc-GTV was 29.4% SUVmax, with a maximal DSC value of 0.72 in all patients. PET-GTVs as defined by thresholds of 25 and 30% of SUVmax were not statistically different from the MR-GTV. The mean thresholds of PETdsc-GTV were 43.3±8.8, 27.9±5.8, and 22.2±2.6% for MR-GTV<14, 14–62, and ≥62 cm3, respectively.

Conclusion PETvis-GTV, PET2.5-GTV, and PET40-GTV do not appear to be suitable for target volume delineation in locally advanced cervical cancer. The PETdsc-GTV may increase the accuracy in target volume delineation. Furthermore, a high level of tumor overlap existed between MR-GTV and PETdsc-GTV in hybrid PET/MRI.

Departments of aRadiology

bOncology, Shengjing Hospital of China Medical University, Shenyang

cPhilips Healthcare, Beijing, China

Correspondence to Jun Xin, PhD, MD, Department of Radiology, Shengjing Hospital of China Medical University, Shenyang 110004, China Tel: +86 189 402 51801; fax: +86 024 239 29902; e-mails:,

Received February 3, 2014

Accepted February 27, 2014

© 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins