No clinically relevant differences between positron emission tomography (PET) reconstructions based on low-dose or contrast-enhanced CT in combined integrated multiphase (18) F-Fluorethylcholine PET/CT for prostate cancer.

OBJECTIVES: To qualitatively and quantitatively compare the reconstructions of (18) F-Fluorethylcholine (FCH) positron emission tomography (PET) based on the non-enhanced X-ray computed tomography (neCT) and contrast-enhanced CT (ceCT) acquired in integrated PET/CT in prostate cancer (PCA) patients. METHODS: We retrospectively analysed FCH-PET/CTs of 63 PCA patients. PET images were reconstructed using either neCT or ceCT for attenuation correction. Contrast-enhancement (HU) and mean and maximum standardised FDG uptake (SUVmean and SUVmax) were measured at eight anatomical sites, and PET images were evaluated for image quality and patient staging by two independent observers. RESULTS: At all anatomical sites the HU values were significantly higher in the ceCT than in the neCT. This in turn led to increases in SUVmean and SUVmax that, although small in both absolute and relative terms, were highly consistent and thus statistically highly significant. However, assessment of the FCH-PET images reconstructed using either neCT or ceCT revealed no differences between observers or reconstructions with regard to patient staging (all κ = 1.0: excellent agreement; P = 1.0). Minor visual differences without clinical relevance were seen in 21 scans by observer 1 and in 22 scans by observer 2 (κ = 0.68, P < 0.001). CONCLUSIONS: There is no clinically relevant difference between reconstruction of PET images based on ceCT or neCT in FCH-PET/CT in patients with prostate cancer. Small quantitative differences exist, but do not lead to clinically relevant differences in visual quality or clinical assessment of patients. Therefore, CT scan may be used for attenuation correction.

Body surface area adapted iopromide 300 mg/ml versus 370 mg/ml contrast medium injection protocol: influence on quantitative and clinical assessment in combined PET/CT.

PURPOSE: To investigate the quantitative and qualitative differences between combined positron emission tomography and computed X-ray tomography (PET/CT) enhanced with contrast medium with either an iodine concentration 300 mg/ml or 370 mg/ml. MATERIALS AND METHODS: 120 consecutive patients scheduled for F-18-Fluorodeoxyglucose (FDG) PET/CT were included. The first (second) 60 patients received contrast medium with 300 (370) mg iodine/ml. Intravenous injection protocols were adapted for an identical iodine delivery rate (1.3mg/s) and body surface area (BSA) adapted iodine dose (22.26 gI/m(2)). Maximum and mean standardized uptake values (SUV(max); SUV(mean)) and contrast enhancement (HU) were determined in the ascending aorta, the abdominal aorta, the inferior vena cava, the portal vein, the liver and the right kidney in the venous contrast medium phase. PET data were evaluated visually for the presence of malignancy and image quality. RESULTS: Both media caused significantly higher values for HU, SUV(mean) and SUV(max) for the enhanced PET/CT than the non-enhanced one (all p<0.01). There were no significant differences in the degree of increase of HU, SUV(mean) and SUV(max) between the two contrast media at any anatomic site (all p>0.05). Visual evaluation of lesions showed no differences between contrast and non-contrast PET/CT or between the two different contrast media (p=0.77). CONCLUSION: When using a constant iodine delivery rate and total iodine dose in a BSA adapted injection protocol, there are no quantitative or qualitative differences in either CT or PET between contrast media with an iodine concentration of 300 mg/ml and 370 mg/ml, respectively.