Radiation Exposure

Key Features

Essentials of Diagnosis

• Damage from radiation is determined by the source, type, quantity, duration, bodily location and susceptibility and accumulation of exposures of the person

• Radiation exposure from medical diagnostic imaging

  • Has risen dramatically over the past few decades

  • Needs standardization and regulation of radiation dosing

• Clinicians and patients must be educated regarding the risks of medical diagnostic radiation weighed against the benefits of the medical imaging needed

• All patients should keep records of their medical imaging radiation exposures, and copies of the medical images and interpretations

General Considerations

• Nonionizing radiation

  • Low energy

  • Results in injuries related to local thermal damage (ie, microwave and radiowave)

• Ionizing radiation

  • High energy

  • Causes cellular disruption, DNA damage, and mutations

  • Categorized as either electromagnetic (ie, x-rays and gamma rays) or particulate, (ie, alpha or beta particles, neutrons, and protons)

  • Exposure may be external, internal or both

• Exposure to radiation may occur from environmental, occupational, medical care, accidental, or intentional (ie, terrorism) sources

RADIATION TERMINOLOGY

• Roentgen (R) refers to the amount of radiation dose delivered to the body

• A rad is the unit of absorbed dose

• A rem is the unit of any radiation dose to body tissue in terms of its estimated biological effect

• For x-ray or gamma-ray radiation, roentgens, rems and rads are virtually the same

• For particulate radiation from radioactive materials, these terms may differ greatly (eg, for neutrons, 1 rad equals 10 rems)

• In the Système International (SI) nomenclature, the rad has been replaced by the gray (Gy), and 1 rad equals 0.01 Gy = 1 cGy

• The SI replacement for the rem is the Sievert (Sv), and 1 rem equals 0.01 Sv

Clinical Findings

Symptoms and Signs

SKIN AND MUCOUS MEMBRANES

• Erythema

• Epilation

• Fingernail destruction

• Epidermolysis

HEMATOPOIETIC TISSUES

• Injury to bone marrow may vary from transient decreases to complete destruction of blood elements

CARDIOVASCULAR SYSTEM

• Pericarditis with effusion or constrictive pericarditis after months or years

• Myocarditis less common

• Smaller vessels (the capillaries and arterioles) more readily damaged than larger ones

UROGENITAL SYSTEM

• Males

  • Small single dose (200–300 cGy) cause temporary aspermatogenesis

  • Larger doses (600–800 cGy) cause permanent sterility

• Females

  • Single dose of 200 cGy may cause temporary cessation of menses

  • 500–800 cGy causes permanent castration

• Moderate–heavy irradiation of embryo in utero results in injury to fetus or embryonic death/spontaneous abortion

PULMONARY SYSTEM

• High or repeated moderate doses may cause pneumonitis or pulmonary fibrosis, often delayed for weeks or months

GASTROINTESTINAL SYSTEM