A patient is scheduled for a magnetic resonance imaging (MRI) scan for suspected lung cancer. Which of the following is a contraindication to the study for this patient?
A. The patient is allergic to shellfish.
B. The patient has a pacemaker.
C. The patient suffers from claustrophobia.
D. The patient takes antipsychotic medication.
Correct Answer: B. The patient has a pacemaker.
The implanted pacemaker will interfere with the magnetic fields of the MRI scanner and may be deactivated by them. The strong static magnetic field (B0) of MRI scanners can attract and accelerate ferromagnetic objects toward the center of the machine and turn them into dangerous projectiles. This magnetic field can also displace implants or affect the function of devices such as pacemakers and pumps.
Option A: Shellfish/iodine allergy is not a contraindication because the contrast used in MRI scanning is not iodine-based. MRI contrast agents are gadolinium chelates with different stability, viscosity, and osmolality. Gadolinium is a relatively very safe contrast; however, it rarely might cause allergic reactions in patients.
Option C: Open MRI scanners and anti-anxiety medications are available for patients with claustrophobia. Claustrophobic patients might refuse to complete the MRI scan and need sedation. These patients need to be well informed about the MRI scan procedure. The recommendation is that a physician has a discussion with them about the details in advance. Using Larger and opener MRI systems might be helpful in claustrophobic patients.
Option D: Psychiatric medication is not a contraindication to MRI scanning. Patients who are unable to be still or obey breathing instructions in the scanner need special attention. Some patients in pain might move during the procedure, which degrades the quality of the images, restrict the interpretation, and decrease the accuracy of the report. Some MRI sequences need to be obtained while patients hold their breath and lie motionless.