Page 94 - Quantitative Imaging of Small Tumours with Positron Emission Tomography
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 A 40 30 20 10 SUVmean SUVpeak SUVmax B 40 30 20 10 01 10 100 1000 01 10 100 1000 ARTV (mL) ARTV (mL) Figure 4.5: Relative difference (%) between SUVs derived from EARL1 images compared to SUVs derived from EARL2 images as a function of lesion ARTV. (A) Results from original (100% of counts) scans and (B) 4 split (50% of counts) images. Semi-quantitative measurements On EARL1 images, SUVmean, SUVpeak, and SUVmax of 100% count scans were highly correlated with those of 50% count scans (Figure 4.4), with SUVmax being most affected by count reduction (albeit still with R2>0.98 and ICC=0.99-1.00). Similar results were observed for EARL2 images (Figure 4.4), with again SUVmax being most affected by count reduction (R2>0.98 and ICC=0.99-1.00). On 100% count EARL2 images, SUVmean, SUVpeak and SUVmax were median 12.1% (IQR 9.8-14.2%), 15.6% (IQR 13.1-17.9%), and 21.7% (IQR 18.4-25.1%) higher compared to EARL1 images. Similarly, on 50% count EARL2 images, SUVmean, SUVpeak and SUVmax were a median 12.0% (9.6-14.2%), 15.5% (IQR 13.2- 17.9%), and 21.6% (IQR 18.5-25.1%) higher compared to EARL1 images. These relative differences were inversely related to lesion ARTV (Figure 4.5). Intrascan variability RCs between 50% count scans on day 1 and 2, respectively, were 9.9% and 8.5% for SUVmean, 14.3% and 12.0% for SUVpeak, and 19.6% and 17.8% for SUVmax (Figure 4.6) on EARL1 images. ICCs and R2 values between SUVs of 50% count EARL1 scans were high (ICC=0.97-1.00; R2=0.95-0.99). On EARL2 images, RCs between 50% count scans on day 1 and 2, respectively, were 10.6% and 9.1% for SUVmean, 16.0% and 13.3% for SUVpeak, and 22.2% and 19.8% for SUVmax (Figure 4.6). For EARL2 images, ICCs and R2 between SUVs of 50% count scans were almost identical to EARL1 (ICC=0.97-0.99.;R2=0.94-0.99.). SUV intrascan variability was volume-dependent for both EARL1 and EARL2 images (Supplemental Figure 1, available at https://ejnmmires.springeropen.com). [18F]FDHT PET repeatability %difference in SUV %difference in SUV 93 


































































































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