Purpose: Alpha particle emitting radionuclides are useful in cancer therapy or delivery of highly conformal doses and high radiotoxicity to target cells. Accurate assessment of the dose absorbed by target site and any adjacent healthy tissues by imaging the distribution of radionuclides is critical for personalized dosimetry and treatment planning. The objective of this research is to confirm the viability of SPECT/CT imaging for ²²³Ra using conventional and digital scanners.
Methods: Imaging protocols were carried out on two SPECT/CT systems: GE Discovery NM/CT 870 DR and GE Discovery NM/CT 670 CZT. The former system was equipped with three sets of collimators: Low Energy High Resolution (LEHR), Medium Energy General Purpose (MEGP), and Extended Low-Energy General Purpose (ELEGP), while the latter had only a Wide Energy High Resolution (WEHR) collimator. The NEMA body phantom was used for SPECT/CT acquisition. Images were reconstructed using two protocols (standard bone protocol and Washington University protocol). The sensitivity and signal-to-noise ratio (SNR) were evaluated for each of the hot spheres in NEMA phantom to determine the optimal collimator and reconstruction method in assessing the activity concentration at target sites.
Results: The sensitivity of each gamma camera was studied and compared. ELEGP collimator was most efficient for both protocols, with highest sensitivity followed by the WEHR collimator (64 X 64 Matrix). For SNR, the ELEGP and MEGP collimators seemed to give similar results. However, the SNR attained from the ELEGP collimator with bone protocol outperformed the SNR obtained with Washington University protocol.
Conclusion: The current research affirms that SPECT/CT imaging of ²²³Ra is feasible using routine clinical and published protocols on sodium iodide cameras and explores the results in CZT camera. Some additional data and analysis tools are required to establish a comparison between the two SPECT systems and comment further on the performance of CZT.