*2.3. Statistical Analysis*

The recovery coefficients from the four hot spherical inserts were used for a multiple linear regression analysis (IBM SPSS, v28) to determine which variables had a statistically significant impact on the measured recoveries. The impact of respiratory motion correction was further assessed by a paired, two-tailed *t*-test on the recovery coefficients from all inserts, comparing results from images with and without respiratory gating. The same test was applied to the AC80 values.
