title: Effect of Radionuclide Activity Concentration on PET-CT Image Uniformity.
abstract: Assessment of radionuclide activity concentration on positron emission tomography-computedr tomography (PET-CT) image uniformity has been carried out quantitatively. Tomographic PET-CT images of cylindrical phantom containing F-18 fluorodeoxyglucose (FDG) activity concentration was acquired and used for the assessment. Activity concentrations were varied and PET-CT images were acquired at the constant acquisition parameters of time, matrix size, and reconstruction algorithm, respectively. Using midtransaxial image slices, quantitative index of nonuniformity (NU), and coefficient of uniformity variation were estimated for the different activity concentrations. Maximum NUs of 17.6%, 26.3%, 32.7%, 36.2%, and 38.5% were estimated for activity concentrations of 16.87 kBq/mL, 14.06 kBq/mL, 11.25 kBq/mL, 8.43 kBq/mL, and 5.62 kBq/mL, respectively. The coefficient of uniformity variation established an inverse quadratic relationship with activity concentration. Activity concentrations of 16.87 kBq/mL, 14.06 kBq/mL, 11.25 kBq/mL, 8.43 kBq/mL, and 5.62 kBq/mL produced uniformity variations of 1.47%, 2.52%, 4.23%, 5.12%, and 4.98%, respectively. Increasing activity concentration resulted in decreasing coefficient of uniformity and hence, an increase in image uniformity. The uniformity estimates compared well with the standards set internationally.
authors.affiliation: Department of Nuclear Medicine, CM Johannesburg Academic Hospital, University of the Witwatersrand, Johannesburg, South Africa; Department of Medical Physics, School of Nuclear and Allied Sciences, University of Ghana, Accra, Ghana,; Medical Radiation Physics Centre, Radiological and Medical Sciences Research Institute, Ghana Atomic Energy Commission, Accra, Ghana.
authors.forename: Francis
authors.initials: F
authors.lastname: Hasford
authors.affiliation: Department of Nuclear Medicine, CM Johannesburg Academic Hospital, University of the Witwatersrand, Johannesburg, South Africa.
authors.forename: Bronwin Van
authors.initials: BV
authors.lastname: Wyk
authors.affiliation: Department of Nuclear Medicine, CM Johannesburg Academic Hospital, University of the Witwatersrand, Johannesburg, South Africa.
authors.forename: Thulani
authors.initials: T
authors.lastname: Mabhengu
authors.affiliation: Department of Nuclear Medicine, CM Johannesburg Academic Hospital, University of the Witwatersrand, Johannesburg, South Africa.
authors.forename: Mboyo Di Tamba
authors.initials: MD
authors.lastname: Vangu
authors.affiliation: Department of Medical Physics, School of Nuclear and Allied Sciences, University of Ghana, Accra, Ghana.
authors.forename: Augustine Kwame
authors.initials: AK
authors.lastname: Kyere
authors.affiliation: Department of Medical Physics, School of Nuclear and Allied Sciences, University of Ghana, Accra, Ghana.
authors.forename: John Humphrey
authors.initials: JH
authors.lastname: Amuasi
keywords: Activity concentration; counts of activity; image uniformity; positron emission tomography-computed tomography; radionuclide