Radiation safety summit: nuclear medicine and PET/CT justification and optimization

Abstract

Widespread concern about radiation exposure requires a serious review of justification and protocols for all imaging studies including dedicated scintigraphic procedures in nuclear medicine as well as hybrid procedures for both PET/CT and SPECT/CT. Consultation with the imaging specialist who will be performing and interpreting the test should include an appropriate review of all of the patient’s relevant imaging prior to the requested study. This will ensure that the requested study is indeed justified. After it is determined the study will add to care of the child, the scintigraphic or hybrid study to be undertaken should be tailored to the particular clinical question to be answered. Repeating studies is to be avoided. Adhering to guidelines for administered radiopharmaceutical doses in children should optimize pediatric nuclear medicine studies. There are two published standards for mainly weight-based pediatric radiopharmaceutical dose administration: (1) Consensus guidelines for administered radiopharmaceutical activities in children and adolescents by Gelfand et al., recently published in the Journal of Nuclear Medicine; and (2) the European Association of Nuclear Medicine (EANM) pediatric dose card by Lassmann et al., published in 2007 in the European Journal of Nuclear Medicine and Molecular Imaging. Certain radiopharmaceuticals are not recommended for use in children. Indium-111 for inflammation has generally not been utilized in the pediatric age group because of possible damage to lymphocytes. More recently the North American consensus guidelines recommend that gallium-67 should only be used infrequently in children and only in low doses because of the high absorbed radiation dose from this radiopharmaceutical. The more widespread use of PET/CT and SPECT/CT hybrid imaging has replaced many of the indications for gallium scintigraphy. Additional reduction of radiation exposure in general nuclear medicine might be possible with software resolution recovery programs to improve image resolution, if lower administered radiopharmaceutical dose is utilized with longer acquisition time. In hybrid imaging to include PET/CT and SPECT/CT, the focus has been on how to reduce the CT dose and adhere to the ALARA principle. Many organizations are providing guidelines and information on the risks of CT examinations in children and information on pediatricspecific CT protocols that should be utilized when performing CT examinations in children (Table 1). For both SPECT/CT and PET/CT the acquisition parameters and DLP and CTDI recorded at the scanner at the time of the study should become part of the permanent record and sent to the PACS. There are now software programs that can calculate the patient effective dose on the fly as the study is performed or retrospectively if these data are available. An accurate cumulative measure of patient effective dose should be part of the patient’s health record as we enter the era of the electronic health record. SPECT/CT studies are mainly performed for tumor studies utilizing I-123 metaiodobenzylguanidine (MIBG) or for bone imaging. In these studies it is particularly important for the imaging physician to tailor the examination. At the time of the request for examination it should be determined whether a CT in addition to the SPECT study might be warranted. If the child has recently had a crosssectional imaging study (CT or MR) that could be fused with post-processing fusion software, then an additional CT Disclaimer Dr. Nadel has no financial interests, investigational or offlabel uses to disclose.