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  • Section 12 Biologic Hazards of Magnetic Resonance Imaging

  • Section 12 Biologic Hazards of Magnetic Resonance Imaging Questions

    1. The use of conventional metal detectors in MR environments is NOT recommended by the American College of Radiology (ACR). The basis for this recommendation considers each of the following EXCEPT .

    A. Metal detectors are not necessary because low fringe fields exist with modern actively shielded superconducting magnets.
    B. Metal detectors do not differentiate between ferromagnetic and nonferromagnetic metallic objects/implants/foreign bodies.
    C. Metal detectors cannot detect a small metal fragment in the orbit or near the heart.
    D. Metal detectors have variable sensitivity response.

    2. What is the ACR recommendation regarding the pregnant health care practitioner working in the MR environment?
    A. Permitted to work in and around the MR environment during the second and third trimesters only.
    B. Permitted to work in and around the MR environment throughout all stages of pregnancy.
    C. Permitted to remain in the magnet room during actual data acquisition/imaging.
    D. Should not enter the magnet room in response to an emergency.

    3. What is the ACR guideline regarding the MR imaging of pregnant patients?
    A. Pregnant patients can be accepted to undergo MR imaging at any stage of pregnancy.
    B. Pregnant patients should not undergo MR imaging during the first trimester.
    C. Gadolinium-based MR contrast agents can be routinely administered to pregnant patients.
    D. Fast MR imaging sequences, such as echo-planar imaging, should be avoided.

    4. Nephrogenic systemic fibrosis (NSF) has been associated with administration of gadolinium-based MR contrast agents to patients with renal disease. What guidelines are recommended by the ACR when considering administering gadolinium-based MR contrast agents to a patient? (Select all that apply.)
    A. Hematologic screening for glomerular filtration rate (GFR) prior to MR imaging.
    B. No special treatment for patients with stage 1 or 2 chronic kidney disease.
    C. Refrain from administering gadolinium-based MR contrast agents to patients with stage 3, 4, or 5 renal disease.
    D. Immediate hemodialysis following administration of gadolinium-based MR contrast agents should be considered for any patient with severe or end-stage renal disease.

    5. The presence of each the following metallic objects/devices is considered a contraindication for MR imaging examination (meaning performance of MR imaging is not routine) EXCEPT
    A. Implantable cardioverter-defibrillator.
    B. Implanted cardiac pacemaker.
    C. Intracranial aneurysm clips composed of titanium.
    D. Ferromagnetic foreign body in the eye.
    E. Swan-Ganz catheters.

    6. Which of the following best defines a quench with respect to the superconducting magnet? (Select all that apply.)
    A. Uncontrolled loss of superconductivity
    B. Rapid boil-off of cryogens
    C. Requires the immediate evacuation of the patient and personnel from the magnet room

    7. According to the Food and Drug Administration (FDA), for the safe operation of pacemakers a controlled access area must be established such that the fringe field outside this area does not exceed ________.
    A. 10 G
    B. 5 G
    C. 1 G
    D. 0.5 G

    8. In 1988, the FDA reclassified MR diagnostic imagers as class II devices. New devices brought to the market had to demonstrate only that they were “substantially equivalent” to MR devices presently on the market. Which of the following are included in safety guidelines pertaining to clinical MR imaging issued by the FDA?
    A. Static magnetic field strength
    B. Time-varying magnetic fields
    C. Radiofrequency (RF) power deposition
    D. Acoustic noise levels

    9. The specific absorption rate (SAR) in units of watts per kilogram describes ________.
    A. Tissue heating induced by changes in magnetic field gradients.
    B. Absorption of transmitted RF energy by tissue.
    C. Attenuation of MR imaging signal by the patient.
    D. Attenuation of the applied static magnetic field within the patient.

    10. What is the principal source of MR-generated acoustic noise during MR imaging?
    A. Cryogen reclamation system
    B. Room air conditioners
    C. Vibrations of the gradient coils
    D. Thermoelastic expansion caused by the absorption of RF energy in the head

    11. Current MR imagers produce time-varying magnetic fields (dB/dt), which can result in which of the following types of stimulation in some patients?
    A. Induction of intense pain (brain stimulation)
    B. Cardiac stimulation
    C. Peripheral nerve stimulation

    12. Local thermal injury to a patient during MR imaging can be caused by ________. (Select all that apply.)
    A. Disconnected surface coil lead left on the patient.
    B. Patient contact with the inner bore of the magnet.
    C. Patients crossing their arms or legs in the MR imager.
    D. Implanted metallic foreign objects in the patient.
    E. All of the above.

    13. What deleterious biologic effects are associated with chronic exposure to magnetic field strengths produced by MR imagers (0.2–4 T)?
    A. Peripheral nerve stimulation
    B. Leukemia
    C. Congenital malformations
    D. No effects are associated.

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