Burden of Medical Radiation Exposure in Children with Sickle Cell Disease.

Children with sickle cell disease (SCD) present to medical attention repeatedly throughout childhood for medical complications. Chest radiographs are often obtained for fever and respiratory symptoms, and plain radiographs are often ordered because of bone pain. Computed tomography (CT) and nuclear medicine (NM) studies may also be obtained for other complications. Exposure to medical radiation may increase the risk of cancer, especially in children. Growing children are inherently radiosensitive because of their high proportion of dividing cells, and children have more remaining years of life than adults during which cancer can develop. Therefore, it is important to determine the magnitude of medical radiation exposure in children with SCD because they could be so frequently exposed.

We reviewed the medical records for all members of the Dallas Newborn Cohort (Blood 2004;103:4023-7) to determine the number and type of radiographic studies each individual received from 1996 to the present. We recorded the type of radiographic study, body location, clinical indication, date of study, age at the time of study, and the number and types of views when applicable. We also recorded slice thickness and mode for CT scans as well as injection activity, radionuclide, and type of radiopharmaceutical for nuclear medicine studies. To account for different lengths of follow-up, we standardized the number of radiographic studies to yearly rates for each individual to determine the projected number of studies a SCD patient would receive by 18 years of age.

We studied 938 patients (52.8% male) with a mean follow-up of 9.4 years (median 9.2, range 0.1 – 20.6). 571 had sickle cell anemia (SS), 283 had sickle-hemoglobin C disease (SC), 63 had Sβ⁺-thalassemia (Sβ⁺), and 21 had Sβ⁰-thalassemia (Sβ⁰). We identified 9,246 radiographic studies, including 8,697 radiographs, 441 CT scans, and 108 NM studies. 711 (76%) patients had at least one radiographic study. Patients with SS or Sβ⁰ were more likely to have had at least one radiographic study than those with SC or Sβ⁺ (77% vs. 65%; P<0.0001). The mean number of studies per patient was 9.9 [95% confidence interval (C.I.) 8.9 – 10.9; range 0 – 115], corresponding to a mean rate of 1.5 per year (95% C.I. 1.3 – 1.6; range 0 – 27.3). We project that a patient with SCD will be exposed to the radiation from 26.7 (95% C.I. 24.1 – 29.3; range 0 – 492.1) radiographic studies by 18 years of age. Approximately 5% of patients with SCD will be exposed to 100 or more radiographic studies during childhood.

Children with SCD are frequently exposed to medical radiation. Some are exposed to over 100 radiographic studies. Radiographs of the painful part are frequently obtained but are infrequently indicated. Because growing children are more radiosensitive than adults and have more remaining years of life, medical radiation exposure could be clinically significant. We are now calculating the radiation effective doses for this cohort to quantify the risk of malignancy. It is prudent to limit the medical radiation exposure of this high-risk population.

No relevant conflicts of interest to declare.