We recently demonstrated in a clinical trial the ability of a new protocol, IQ SPECT, to acquire myocardial perfusion imaging (MPI) studies in a quarter of the time (12 s/view) of the standard protocol, with preserved diagnostic accuracy. We now aim to establish the lower limit of radioactivity that can be administered to patients and the minimum acquisition time in SPECT MPI using an IQ SPECT protocol, while preserving diagnostic accuracy. Methods: An anthropomorphic cardiac phantom was used to acquire clinical rest scans with a simulated in vivo distribution of ^99mTc-tetrofosmin at full dose (740 MBq) and at doses equal to 50%, 25%, and 18%. For each dose, 2 sets of images were acquired, with and without a transmural defect (TD). Variable acquisition times were also used for each dose. We analyzed raw data and reconstructed images, including no correction and correction for attenuation (AC), for scatter (SC), or for both (ACSC). Images were evaluated qualitatively and quantitatively in order to assess left ventricle (LV) wall thickness (full width at half maximum of the medial sections), TD, and cavity contrast in the LV wall. Data were compared across different acquisition times within the same dose and across doses with the same acquisition time. Results: Images were visually scored as very-good quality except those acquired with 4 s/view or less at 100% dose and 6 s/view or less with 50%, 25%, or 18% dose, due to false-positive defects. LV wall thickness was not significantly different among all acquisitions. Cavity contrast remained unchanged within the same dose for all images and tended to be higher in AC and ACSC images. TD contrast remained unchanged within the same dose for all images. In SC and no-correction images, contrast was constant for all doses. AC images had significantly higher TD contrast values, and ACSC images showed a drop in TD contrast for a 50% dose. Conclusion: IQ SPECT effectively preserved both image quality and quantitative measurements with reduced acquisition time or administered dose in a phantom study. These findings suggest that approximately one eighth of the time, compared with standard protocols with a full dose, or a lower dose at an acquisition time of 12 s/view can be applied in MPI without the loss of diagnostic accuracy.

Neuroblastoma is the most common extra-cranial solid tumor in pediatric patients. Despite the established role of 123I-MIBG and 131I-MIBG scintigraphy in this tumor, only limited data are available regarding the use of 124I-metaiodobenzylguanidine (MIBG) positron emission tomography (PET)/computed tomography (CT). We present our preliminary experience with 124I-MIBG PET/CT: two pediatric patients affected by neuroblastoma, who underwent 124I-MIBG PET/CT for pre-therapy distribution evaluation and restaging purposes. We aimed to evaluate whether 124I-MIBG PET/CT can detect as many or more neuroblastoma lesions than 123I/131I-MIBG imaging. Our cases show promising results, although further validation and standardization of 124I-MIBG PET/CT are required. Neuroblastoma is the most common extra-cranial solid tumor in pediatric patients. Despite the established role of 123I-MIBG and 131I-MIBG scintigraphy in this tumor, only limited data are available regarding the use of 124I-metaiodobenzylguanidine (MIBG) positron emission tomography (PET)/computed tomography (CT). We present our preliminary experience with 124I-MIBG PET/CT: two pediatric patients affected by neuroblastoma, who underwent 124I-MIBG PET/CT for pre-therapy distribution evaluation and restaging purposes. We aimed to evaluate whether 124I-MIBG PET/CT can detect as many or more neuroblastoma lesions than 123I/131I-MIBG imaging. Our cases show promising results, although further validation and standardization of 124I-MIBG PET/CT are required.