Radiation Safety With Positron Emission Tomography and Computed Tomography

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Combined positron emission tomography and computed tomography (PET/CT) has proven clinical utility, particularly in the diagnosis, staging, and management of cancer. The use of PET/CT has grown substantially in the past few years, with an increasing number of hospitals and imaging centers installing PET/CT systems each year. The combination of 2 procedures, which each imparting a radiation dose and hence the potential for deleterious health effects, creates unique radiation safety issues. This article addresses the radiation safety issues posed by PET/CT with regard to the protection and safety of PET/CT personnel, the public, and adult and pediatric patients.

Section snippets

PET/CT Shielding Requirements

PET/CT is most commonly performed with 18F-FDG, which has a half-life of 109.8 minutes. Fluorine-18 is a positron-emitting radionuclide that leads to an annihilation reaction of a positron and electron, producing two 511 keV photons. The 511 keV annihilation photons are much more highly penetrating than other diagnostic radiations.9 Therefore, a greater amount of lead is required for shielding in PET/CT suites compared with traditional diagnostic radiology or nuclear medicine examination rooms.

Radiation Exposure to PET/CT Technologists and Personnel

The radiation doses received by PET/CT technologists may be higher than those received by diagnostic radiology technologists or by general nuclear medicine technologists who do not perform PET/CT.15 There are several factors that lead to an increased risk of occupational exposure for PET/CT technologists, and these are predominantly related to the PET portion of the examination. The 511 keV photons from 18F-FDG have uniquely high energy and penetration. For comparison, the γ ray constant (which

Radiation Exposure to Non-PET/CT Staff and the Public

After injection of a radiopharmaceutical, the patient becomes a radiation source and should be placed in a designated uptake room with a nearby patient-only toilet. Typically, a PET/CT is performed 1 hour after injection. The patient should rest quietly and comfortably in a darkened room for this hour to minimize muscle activity during the uptake period. The main consideration for not returning the patient to the waiting room is the promotion of peaceful inactivity on the part of the patient

Radiation Exposure to Patients

Although most PET/CT studies are performed on patients who already have cancer, the issue of radiation safety is still pertinent. Patients with cancer often undergo multiple PET/CT examinations over the course of several years, and the long-term survival of cancer patients is increasing.19

Radiation dose to the patient from a PET/CT scan is equal to the sum of the combined dose from the PET and the CT components of the scan. The radiation dose of the FDG PET component of the scan has been

Pregnant Patients

There is limited data regarding the use of PET/CT in pregnant patients. A combined PET/CT results in a relatively high radiation dose to an embryo.24 This is a function of 18F-FDG uptake as well as the CT dose, which varies depending on the scan parameters. Every female patient referred for PET/CT should be carefully screened for pregnancy, and the study is usually canceled if there is a question of pregnancy. There may be instances in which the benefits of a PET/CT would outweigh the risks to

Lactating Patients

Given the increasing use of PET/CT, it is not uncommon for a currently breastfeeding woman to be referred for PET/CT. Lactating patients demonstrate significantly increased uptake of radiotracer in their breasts compared with nonlactating patients.27 This is predominantly because of uptake of 18F-FDG by active glandular tissue. A relatively low level of radiotracer is excreted into the actual breast milk.28 Consequently, the main source of radiation exposure for a nursing infant would be close

Pediatric Patients

PET/CT has proven utility in pediatric oncology and can significantly change clinical management in many pediatric malignancies.29 Concern over the radiation dose to pediatric patients undergoing CT examinations has heightened in recent years, and increased awareness and education has led to significant improvements in this regard.30, 31 PET/CT faces similar concerns given the ever-increasing number of pediatric patients referred for examinations. Both the CT and the PET portions of the

Summary

PET/CT has become an indispensable modality in clinical imaging, particularly in the management of oncology patients, and is becoming the study of choice for many indications.36, 4 PET/CT is accurate and quick, and is becoming increasingly available in various practice settings.37 The use of 18F-FDG, a positron-emitting radionuclide, poses special hazards in a PET/CT facility. The radiation exposure to patients undergoing PET/CT is of concern as the dose is a combination of internal and

References (37)

  • M.A. Dell

    Radiation safety review for 511-keV emitters in nuclear medicine

    J Nucl Med Technol

    (1997)
  • A. Bixler et al.

    Practical aspects of radiation safety for using fluorine 18

    J Nucl Med Technol

    (1999)
  • B. Huang et al.

    Whole body PET/CT scanning: Estimation of radiation dose and cancer risk

    Radiology

    (2009)
  • T.H. Wu et al.

    Radiation exposure during transmission measurements: Comparison between CT and germanium based techniques with a current PET scanner

    Eur J Nucl Med Mol Imaging

    (2003)
  • E. Hippelainen et al.

    Personal radiation doses in PET/CT facility: measurements vs. calculations

    Radiat Prot Dosim

    (2008)
  • P. Zanzonico et al.

    Operational radiation safety for PET-CT, SPECT-CT and cyclotron facilities

    Health Phys

    (2008)
  • M.T. Madsen et al.

    AAPM task group 108: PET/CT shielding requirements

    Med Phys

    (2006)
  • F.O. Roberts et al.

    Radiation dose to PET technologists and strategies to lower occupational exposure

    J Nucl Med Technol

    (2005)
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