Using gamma–gamma coincidence measurements to validate Monte Carlo generated detector response functions

Author(s):  
W.A. Metwally ◽  
R.P. Gardner ◽  
A. Sood
2017 ◽  
Vol 20 (2) ◽  
pp. 65 ◽  
Author(s):  
Rasito Tursinah ◽  
Bunawas Bunawas ◽  
Jungho Kim

Neutron Response Function of Bonner Sphere Spectrometer With 6LiI(Eu) Detector. The detector response function was needed to measure the neutron fluence based on the count rates from Bonner Sphere Spectrometer (BSS). The determination of response function of a BSS with 6LiI(Eu) detector has been performed using Monte Carlo MCNPX code. This calculation was performed for BSS using scintillation detector of 4 mm × 4 mm 6LiI(Eu) which is placed at the center of a set of polyethylene spheres i.e bare, 2", 3", 5", 8", 10", and 12" diameters. The BSS response functions were obtained for neutron energy of 1x10-9 MeV - 1x102  MeV in 111 energy bins and each value has an uncertainty less or equal to 2 %. The response function were compared with two response functions reported in the literature i.e IAEA document in Technical Reports Series 403 (TRS-403) and the calculation from Vega-Carrillo, et al. Also validated with measurement 252Cf neutron spectra, that shown the simulated BSS spectra were quite close to the experimental measured with a differrence of 3%.


2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Keamogetswe Ramonaheng ◽  
Johannes A. van Staden ◽  
Hanlie du Raan

Abstract Background Different gamma camera calibration factor (CF) geometries have been proposed to convert SPECT data into units of activity concentration. However, no consensus has been reached on a standardised geometry. The CF is dependent on the selected geometry and is further affected by partial volume effects. This study investigated the effect of two CF geometries and their corresponding recovery coefficients (RCs) on the quantification accuracy of 177Lu SPECT images using Monte Carlo simulations. Methods The CF geometries investigated were (i) a radioactive-sphere surrounded by non-radioactive water (sphere-CF) and (ii) a cylindrical phantom uniformly filled with radioactive water (cylinder-CF). Recovery coefficients were obtained using the sphere-CF and cylinder-CF, yielding the sphere-RC and cylinder-RC values, respectively, for partial volume correction (PVC). The quantification accuracy was evaluated using four different-sized spheres (15.6–65.4 ml) and a kidney model with known activity concentrations inside a cylindrical, torso and patient phantom. Images were reconstructed with the 3D OS-EM algorithm incorporating attenuation, scatter and detector-response corrections. Segmentation was performed using the physical size and a small cylindrical volume inside the cylinder for the sphere-CF and cylinder-CF, respectively. Results The sphere quantification error (without PVC) was better for the sphere-CF (≤ − 5.54%) compared to the cylinder-CF (≤ − 20.90%), attributed to the similar geometry of the quantified and CF spheres. Partial volume correction yielded comparable results for the sphere-CF-RC (≤ 3.47%) and cylinder-CF-RC (≤ 3.53%). The accuracy of the kidney quantification was poorer (≤ 22.34%) for the sphere-CF without PVC compared to the cylinder-CF (≤ 2.44%). With PVC, the kidney quantification results improved and compared well for the sphere-CF-RC (≤ 3.50%) and the cylinder-CF-RC (≤ 3.45%). Conclusion The study demonstrated that upon careful selection of CF-RC combinations, comparable quantification errors (≤ 3.53%) were obtained between the sphere-CF-RC and cylinder-CF-RC, when all corrections were applied.


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