title: Estimation of the total effective dose from low-dose CT scans and radiopharmaceutical administrations delivered to patients undergoing SPECT/CT explorations.
abstract: Hybrid imaging, such as SPECT/CT, is used in routine clinical practice, allowing coregistered images of the functional and structural information provided by the two imaging modalities. However, this multimodality imaging may mean that patients are exposed to a higher radiation dose than those receiving SPECT alone.
  
  
  OBJECTIVE
  The study aimed to determine the radiation exposure of patients who had undergone SPECT/CT examinations and to relate this to the Background Equivalent Radiation Time (BERT).
  
  
  METHODS
  145 SPECT/CT studies were used to estimate the total effective dose to patients due to both radiopharmaceutical administrations and low-dose CT scans. The CT contribution was estimated by the Dose-Length Product method. Specific conversion coefficients were calculated for SPECT explorations.
  
  
  RESULTS
  The radiation dose from low-dose CTs ranged between 0.6 mSv for head and neck CT and 2.6 mSv for whole body CT scan, representing a maximum of 1 year of background radiation exposure. These values represent a decrease of 80-85% with respect to the radiation dose from diagnostic CT. The radiation exposure from radiopharmaceutical administration varied from 2.1 mSv for stress myocardial perfusion SPECT to 26 mSv for gallium SPECT in patients with lymphoma. The BERT ranged from 1 to 11 years.
  
  
  CONCLUSIONS
  The contribution of low-dose CT scans to the total radiation dose to patients undergoing SPECT/CT examinations is relatively low compared with the effective dose from radiopharmaceutical administration. When a CT scan is only acquired for anatomical localization and attenuation correction, low-dose CT scan is justified on the basis of its lower dose.
authors.affiliation: Medical Physics Department, University Hospital of Salamanca, Paseo de San Vicente, 58-182, 37007, Salamanca, Spain. carlosmf5@hotmail.com
authors.forename: Carlos
authors.initials: C
authors.lastname: Montes
authors.forename: Pilar
authors.initials: P
authors.lastname: Tamayo
authors.forename: Jorge
authors.initials: J
authors.lastname: Hernandez
authors.forename: Felipe
authors.initials: F
authors.lastname: Gomez-Caminero
authors.forename: Sofia
authors.initials: S
authors.lastname: García
authors.forename: Carlos
authors.initials: C
authors.lastname: Martín
authors.forename: Angela
authors.initials: A
authors.lastname: Rosero
mesh_terms: D001417:Background Radiation; D004781:Environmental Exposure / Q000032:analysis; D006801:Humans; D011829:Radiation Dosage; D019275:Radiopharmaceuticals / Q000008:administration & dosage*; D015899:Tomography, Emission-Computed, Single-Photon; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D019275:Radiopharmaceuticals