Radiation dose management for pediatric cardiac computed tomography: a report from the Image Gently ‘Have-A-Heart’ campaign
Children with congenital or acquired heart disease can be exposed to relatively high lifetime cumulative doses of ionizing radiation from necessary medical imaging procedures including radiography, fluoroscopic procedures including diagnostic and interventional cardiac catheterizations, electrophysiology examinations, cardiac computed tomography (CT) studies, and nuclear cardiology examinations. Despite the clinical necessity of these imaging studies, the related ionizing radiation exposure could pose an increased lifetime attributable cancer risk. The Image Gently “Have-A-Heart” campaign is promoting the appropriate use of medical imaging studies in children with congenital or acquired heart disease while minimizing radiation exposure. The focus of this manuscript is to provide a comprehensive review of radiation dose management and CT performance in children with congenital or acquired heart disease.
Computed tomography Children Congenital heart disease Heart Radiation safety
Diagnostic imaging and image-guided interventions are essential in the care of children with known or suspected congenital or acquired heart disease. Many imaging modalities, including radiography, fluoroscopy/angiography, computed tomography (CT) and nuclear imaging depend on ionizing radiation for image formation. Ionizing radiation in high doses can have biological effects, including carcinogenesis . However, the amount of radiation delivered for diagnostic imaging is typically low-level. Evidence of deoxyribonucleic acid (DNA) damage has been shown to occur with ionizing radiation doses in the medical imaging range [2, 3], but how this relates to the risk of cancer is not known . There have been reports of excess cancer risk in patients exposed to CT as children [4, 5], but the challenges to the methodologies of these studies, including the possibility of reverse causation, highlight the complexities of studying excess cancer risk in populations [6, 7, 8, 9]. Children are especially vulnerable to the harmful effects of ionizing radiation due to the greater sensitivity of growing tissue and a longer anticipated lifetime to manifest radiation-induced damage as compared to adults . Moreover, because of reduced tissue attenuation, similar exposures in smaller children result in greater doses to organs and tissues than in larger children (i.e. teenagers) and adults.
The scientific and medical communities are engaged in a dialogue regarding the relationship of radiation from modalities such as CT, and cancer risk. Opinions range from a perspective that small amounts of radiation might reduce cancer risk (hormesis), to positions that risk is effectively zero, linearly related to dose, or that risk is greater than linear [4, 5, 11, 12, 13, 14, 15, 16]. The majority of the expert communities, reflected by reports from the International Commission on Radiological Protection, the United States National Academies and the National Council on Radiation Protection and Measurements [10, 17, 18, 19, 20], subscribe to the position that the risk associated with low-dose ionizing radiation exposure is uncertain, with a linear relationship between dose and risk reasonably fitting the limited available data. This perspective is reflected in the principle of ALARA (dose as low as reasonably achievable) and incorporates both justification and optimization. Justification indicates that imaging is appropriately indicated and that the expected benefits are sufficiently greater than the risks. Optimization entails performing the study so that there is due consideration given to both image quality and radiation exposure, using only as much radiation as is necessary to address the clinical questions. A scientific statement of expert consensus recommendations for multimodality optimization of medical imaging procedures commonly performed in children with congenital or acquired heart disease was written as part of the Image Gently Have-A-Heart campaign . This Image Gently report focuses on radiation dose management and cardiac CT performance in children with congenital or acquired heart disease.
Several factors guide the discussion of CT radiation and risk in children congenital or acquired heart disease: (1) increasing value and use of this modality even in the youngest children [22, 23, 24], (2) relatively high radiation dose of CT compared with radiography, (3) longer anticipated survival of children relative to adults, with the potential for larger cumulative doses, and (4) less familiarity with the proper performance of pediatric CT for congenital or acquired heart disease among those who care for these patients relatively infrequently [23, 25, 26, 27, 28, 29]. Health care providers as well as patients, parents, other caregivers and the public have a limited and sometimes inaccurate understanding of which imaging examinations use radiation, the potential and effective radiation doses of these exams, and the attendant risks [30, 31, 32, 33, 34, 35, 36, 37, 38, 39]. For these reasons, we review key aspects of cardiac CT performance in children with congenital or acquired heart disease as a reference with respect to radiation dose management for those involved in the care of these children including primary providers, pediatric radiologists, cardiologists, surgeons, physicists, technologists and nurses. Topics include radiation dose metrics, reported cardiac CT dose ranges, considerations for selecting cardiac CT as an imaging modality, techniques for optimum performance of cardiac CT, risk communication with patients and caregivers, and implementation of institutional CT dose monitoring.
Radiation dose metrics
Effective dose is a calculated whole-body metric reported in the SI (International System of Units) unit of Sievert (Sv). Effective dose reflects the relative risk of detrimental biological effects from exposure to ionizing radiation and accounts for the absorbed dose to all cancer-susceptible organs of the body, the relative harm level of the type of ionizing radiation, and the organ radiation sensitivities with respect to cancer susceptibility from ionizing radiation exposure. As a whole-body metric, effective dose is useful for comparing doses across different imaging modalities that employ ionizing radiation (e.g., radiographs, fluoroscopy, CT, nuclear medicine) [40, 41].
CT dose reports
Current CT scanners provide a [Read more….]