Impact of prone position on the diagnostic performance and standardized uptake value of dual-phase ¹⁸F-FDG PET/CT in breast cancer

Objectives The purpose of the study is to determine the influence of prone position on the diagnostic performance and standardized uptake value of dual-phase PET/CT in breast cancer by comparison with dual-phase PET/CT in supine position.

Methods Fifty-one consecutive patients with suspected breast cancer underwent dual-phase supine and prone PET/CT. First-phase supine PET/CT was performed after an uptake phase of 60 min, followed by prone PET/CT after an uptake phase of 70 min by using fixation device. Second-phase supine and prone PET/CT were performed after an uptake phase of 110 and 120 min, respectively. Dual-phase supine PET/CT (supPET/CT) and dual-phase prone PET/CT (proPET/CT) were visually assessed by using a 5-point scoring system for breast lesions. Maximum standard uptake value (SUVmax) and peak SUV (SUVpeak) of the lesions were measured by region of interest with 1.25-cm diameter sphere. The diagnostic capabilities were compared by the ROC analysis followed by the McNemar’s test, based on the reference standard. To evaluate the influence on SUV between supine and prone position, the percentage of change in dual-phase (delta%SUVmax and delta%SUVpeak) were statistically compared by the paired t-test.

Results 88 lesions in 51 patients were detected, and determined by the reference standard. There was no significant difference in area under the curve, sensitivity, specificity and accuracy between supPET/CT and proPET/CT. Delta%SUVmax and delta%SUVpeak of proPET/CT (37.3±48.2 and 33.7±43.7) were significantly lower than those of supPET/CT (48.1±40.4 and 41.1±37.7).

Conclusions Diagnostic performance of dual-phase PET/CT is not influenced by the patients’ positions, however, SUV change in dual-phase is significantly different between supine and prone position. Attention needs when using SUV of dual-phase prone PET/CT for assessment of breast cancer