Quantitative Assessment of Radionuclide Uptake and Positron Emission Tomography-computed Tomography Image Contrast.

Radionuclide uptake and contrast for positron emission tomography-computed tomography (PET-CT) images have been assessed in this study using NEMA image quality phantom filled with background activity concentration of 5.3 kBq/mL fluorodeoxyglucose (F-18 FDG). Spheres in the phantom were filled in turns with water to mimic cold lesions and FDG of higher activity concentrations to mimic tumor sites. Transaxial image slices were acquired on the PET-CT system and used for the evaluation of mean standard uptake value (SUVmean) and contrasts for varying sphere sizes at different activity concentrations of 10.6 kBq/mL, 21.2 kBq/mL, and 42.4 kBq/mL. For spheres of same sizes, SUVmean increased with increase in activity concentration. SUVmean was increased by 80.6%, 83.5%, 63.2%, 87.4%, and 63.2% when activity concentrations of spheres with a diameter of 1.3 cm, 1.7 cm, 2.2 cm, 2.8 cm, and 3.7 cm, respectively, were increased from 10.6 kBq/mL to 42.4 kBq/mL. Average percentage contrast between cold spheres (cold lesions) and background activity concentration was estimated to be 89.96% for the spheres. Average contrast for the spheres containing 10.6 kBq/mL, 21.2 kBq/mL, and 42.4 kBq/mL were found to be 110.92%, 134.48%, and 150.52%, respectively. The average background contrast variability was estimated to be 2.97% at 95% confidence interval (P < 0.05).

Comparative Study of Radionuclide Uptake Levels between Primary and Metastatic Bone Tumors.

Study on 95 patients to compare radionuclide uptake levels in patients undergoing bone scintigraphy at a Nuclear Medicine Unit has been performed quantitatively using Image J software. Patients were administered with activity ranging from 0.555 to 1.110 MBq depending on their body weight, and their whole-body bone scans obtained with an installed e.cam single-photon emission computed tomography system. Matrix size of 256 × 1024 was used in acquiring the scintigrams. Quantitative analyses performed with installed Image J software revealed higher radionuclide uptake levels in metastatic tumors compared with primary tumors for all selected skeletal parts. Average normalized count of activity in metastatic tumors was 37.117 ± 27.740 cts/mm(2)/MBq and its corresponding uptake in primary tumors was 23.035 ± 19.542 cts/mm(2)/MBq. The relative higher uptake in metastatic tumors over primary tumors could be attributed to higher osteoblastic activity and blood flow in metastatic tumors.