Authors: Mohd Hafizi Mahmud, Abdul Jalil Nordin, Fathinul Fikri Ahmad Saad and Ahmad Zaid Fattah Azman
Objective: To evaluate the effects of intravenous (IV) contrast media on computed tomography (CT) value and positron emission tomography (PET) semi-quantification value of liver and lesion during contemporaneous whole body fluorine-18 fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) in cancer imaging.
Methods: We reviewed whole body 18F-FDG PET/CT scans of 51 oncology cases performed with and without IV contrast administration. Non-enhanced CT images were acquired following IV injection of FDG. Subsequently contrast-enhanced CT images were acquired utilizing non ionizing iodinated contrast media without positional change. PET images were reconstructed using both contrast-enhanced and unenhanced CT image datasets. Region of interest (ROI) was drawn on field of view over the site of lesion on PET contrast-enhanced CT images. Similar ROI was copied to the corresponding PET non-enhanced CT images. The mean Hounsfield unit (HUmean) and maximum standardized uptake value (SUVmax) of both datasets were compared using paired-samples t-test with p < 0.05 considered as significant. Results: The mean ± standard deviation percentage difference of SUVmax between contrast-enhanced and unenhanced CT for all investigated liver and lesions were not significant [(0.064% ± 0.559 and 0.245% ± 1.192), respectively, p > 0.05], but significant differences were observed in CT values [(77.99% ± 19.65 and 41. 62% ± 149.40) %, respectively, p < 0.05]. Conclusion: Contrast-enhanced 18F-FDG PET/CT protocol causes significant change in HUmean values within enhanced liver and lesion, with no significant effect in SUVmax values, thus this protocol can be recommended in routine PET/CT examination, optimizing its role as a ‘one-stop’ imaging modality. Keywords: contrast-enhanced CT, PET/CT, cancer imaging