Ground truth was defined using patient datasets consisting of 60 min fluorodeoxyglucose (18F-FDG) dynamic acquisitions of 22 patients with non-high-grade (grades 1 and 2), estrogen receptor positive (ER+) primary breast cancer pre- and post-therapy, as previously described (Wangerin et al 2015 (link)). Patient characteristics are summarized in table 3. The patient scans were performed on a GE Discovery STE PET/CT Scanner (GE Healthcare, Waukesha, WI). The dynamic data were acquired with frames of 16 × 5 s, 7 × 10 s, 5 × 30 s, 5 × 60 s, 5 × 180 s, 7 × 300 s. The data were reconstructed using 3D OSEM with 28 subsets, six iterations, and a 7 mm transaxial Gaussian post-filter. The image voxel size was 4.3 × 4.3 mm transaxially and 3.3 mm axially. The tumor and normal breast tissue regions-of-interest (ROIs) were 3 × 3 × 3 voxels (1.6 cc). The normal breast tissue ROI was placed in the most homogeneous portion in successive tissue in the contralateral breast. We note here that while partial volume effects, as described in Soret et al (2007) (link), were present in the estimate of SUV, the tumors were not expected to significantly change in size between the pre- and post-therapy scans (average time = 20 d) when treated with hormonal therapy. Thus, partial volume correction methods were not evaluated.