Page 66 - Quantitative Imaging of Small Tumours with Positron Emission Tomography

Statistical analysis Data were described as mean with standard deviation (SD), median with interquartile range (IQR), minimum and maximum. Correlations between pairwise data were investigated using Spearman correlation. To assess technical validation of simplified metrics, we assessed correlations between both single measurements of kinetic parameter estimations and simplified metrics as well as correlations between relative changes in these parameters during treatment. 3 Differences were tested using the Wilcoxon signed rank test (two related) or the Friedman test (multiple related), with significance level p<0.05. SPSS Statistics v22 (IBM) was used for statistical analyses. Results Patients Ten patients with EGFR-mutated NSCLC were included, consisting of 4 men and 6 women with a mean age of 64±8 years. Treatment consisted of gefitinib and erlotinib in 7 and 3 patients, respectively. In one patient, the baseline scan was not evaluable due to scanner failure (scan at 7 and 28 days could still be used for lesion-based analyses). Another patient had no visible lesions at PET-CT. Twenty- four suspected lesions were detected on 18F-FLT PET-CT (5). HYPR optimization A single composite (HYPRsingle) provided most SNR improvement (Supplemental Figure 1, available at https://ejnmmires.springeropen.com). However, it eliminated the temporal dynamics of PVC (Figure 1). A HYPRmoving setting with a composite image consisting of ±3 frames relative to the denoised frame provided an adequate trade-off between SNR improvement and partial-volume correction and was hence used in further analyses. Image-derived input functions We verified the assumption that partial-volume effects do not affect ascending aorta-derived IDIFs (based on the 2x2 voxel VOI approach used that minimized or avoided partial volume effects). First, PVC introduced only small relative differences in IDIF area-under-the-curve (AUC; Table 3.1), which were mitigated by HYPRmoving and reduced to 0% by HYPRsingle (the latter providing most noise PVC in dynamic PET-CT 65