Comparison of image quality of different radionuclides technetium-99m, samarium-153, and iodine-123

Abstract

Introduction: The choice of the radionuclide has a key role in nuclear medicine which appearing the lowest scatter fraction. In addition, the presence of penetrated and scattered photons from collimator in single-photon emission computed tomography images degrades resolution and contrast. Thus, image quality depends on sensitivity and resolution of the collimator–detector system. The goal of this study was to compare the image quality that can be achieved by three radionuclides: technetium-99 m (Tc-99 m), iodine-123 (I-123), and samarium-153 (Sm-153). Materials and Methods: Tc-99 m and Sm-153 were imaged with low-energy high resolution (LEHR) collimator, while I-123 was imaged with medium-energy (ME) collimator. We modeled the Siemens Symbia Medical system using Monte Carlo simulation code SIMIND. The imaging characteristics of each radionuclide were investigated by simulated data: point spread function, sensitivity (Cps/MBq) and geometric, penetration and scattering distribution. Results: Tc-99 m and Sm-153 give best and results with LEHR collimator for spatial resolution (full width at half maximum [FWHM] = 3.19 mm; full width at tenth maximum [FWTM] = 6.73 mm) and (FWHM = 3.22 mm; FWTM = 7.39 mm), respectively. Whereas, I-123 provided with ME collimator a lower resolution (FWHM = 4.89 mm; FWTM = 9.89 mm). The sensitivity recorded by Tc-99 m, Sm-153, and I-153 were (31.21 Cps/MBq), (10.16 Cps/MBq), and (51.22 Cps/MBq), respectively. Conclusion: Tc-99 m and Sm-153 give the best and generally similar imaging properties with LEHR. For I-123, the ME collimator helps lowering the influence of high-energy gamma rays.

Collimator and Energy Window Evaluation in Ga-67 Imaging by Monte Carlo Simulation

“…These parameters were compared within the 20% and 10% energy windows. It can be seen from the table that, for each collimator, the FWTM increased with the width of the energy windows, especially for the LEHR and ME collimators, while, the FWHM remained approximately the same ( 21 , 22 , 23 ). On the other hand, the sensitivity decreased when the width of the energy window decreased, which was an extremely sharp transition for LEHR.…”

“…The curves of Ga-67 with the ME and HE collimators demonstrate the effects of the septal that lowers the resolution. LEHR offers a poorer resolution than the HE and ME collimators within 20% and 10% windows ( 20 , 21 , 22 ) owing to the septal penetration and the scattering effects.…”

“…The presence of a high level of penetrated and scattered photons from the LEHR collimator degrades spatial resolution, contrast, and quantification ( 20 , 21 , 22 , 23 , 24 ). Table 6 depicts that the use of LEHR collimator with Ga-67 imaging resulted in the most degraded spatial resolution, while the use of an HE collimator in Ga-67 imaging resulted in the loss of sensitivity and spatial resolutions ( 25 ).…”