Fig. 6

Example from enema group showing the PET-CT scans at 45 min (a, d), 2 h (b, e) and 4 h (c, f) for different transaxial slices in the same subject. The blue circular ROI of 10 mm radius was drawn on three consecutive slices in bladder, the red ROI marks the tumour and the yellow arrow shows the non-tumour activity in close proximity to the tumour ROI. a–c highlights the fact that the non-tumour [¹⁸F]FMISO in rectum in close proximity to the tumour is visible at 2 h, but not after the enema given before the 4 h scan. In d–f, the patient emptied their bladder before the 4 h scan as seen from the reduced volume/activity in the bladder in f compared to d (42 cm³ compared to 16 cm³ when thresholded using an absolute value of 5 kBq/cm³ to estimate the bladder volume) but the activity accumulated again at 4 h (in f). As a result, the tumour TAC in Fig. 7 shows an increase while the bladder activity was almost the same at 2 and 4 h, showing the direct effect of bladder activity on tumour [¹⁸F]FMISO quantification. PET = positron emission tomography; CT = computed tomography; min = minute; h = hour; ROI = region of interest; mm = millimetre; cm³ = cubic centimetre; TAC = time-activity curves; [¹⁸F]FMISO = [¹⁸F]fluoromisonidazole; kBq = kilo Becquerel