AJR: MR-conditional examswhat rads need to know
The approval of an MR-conditional pacemaker system opens the door to imaging patients with implanted cardiac devices. In order to ensure a safe study, radiologists need to understand and communicate the specific limitations of scanning with these devices, according to an opinion published in the September issue of American Journal of Roentgenology.
“Approximately 50 to 75 percent of the more than 1.5 million patients with implanted cardiac devices may have indications for MRI during the course of these devices,” wrote Patrick M. Colletti, MD, from the department of radiology at University of Southern California in Los Angeles, and colleagues.
The authors noted that the FDA has approved one MR-conditional system and predicted that others, already approved for use in Europe, will follow.
“The importance of appropriate MR-conditional pacemaker management cannot be overstated,” wrote Colletti et al, who provided guidance for radiologists and other healthcare professionals to ensure safe, diagnostic exams.
The first step, they said, is to consult with the referring physician to determine if another modality could offer the required diagnostic data. If MRI is the only suitable exam, physicians need to ensure that the pacemaker is labeled for MRI, properly implanted and that no other implanted devices are present.
After the cardiologist verifies the pacemaker history and system model, the pacemaker should be examined to verify appropriate thresholds.
Prior to the actual scan, a healthcare professional with MR-safe training needs to re-examine the system and specifications and set the pacemaker to the “on” mode. In addition, a professional with appropriate training must supervise the MRI study.
Colletti et al reiterated that the current system is limited to scans of the brain, skull base, upper neck and cervical spine, thoracolumbar spine, mid and lower abdomen, pelvic and lower extremities. The patient must be placed in the system head or feet first depending on the region to be scanned. Scans of the hands, wrist or elbow may be completed if the patient enters the scanner with his or her arm over the head. The authors added that the body radiofrequency coil should not be placed over the pacemaker.
MRI scans of patients with MR-conditional pacemakers are limited to 1.5T systems at a maximum gradient slew rate of 200 T/m/s per axis or less with the scanner in “normal operating mode.”
After the study, the pacemaker pulse generator should be turned off and the system should be re-checked to confirm normal function.
Given the complexities and risks among this population, “it is reasonable for all MRI providers to adjust their policies and procedures to either appropriately scan or decline to scan patients with MR-conditional pacemakers,” wrote Colletti and colleagues. They added that schedulers should be aware that such studies require prior notification and approval by a radiologist.
The authors issued a final caution, noting that scanning of pacemaker-dependent patients requires specific pulse generator settings. However, it is difficult to define such patients and predict the reliability of the underlying rhythm, necessitating careful monitoring to avoid complications.
“The introduction of MR-conditional cardiac devices enables the vital diagnostic capabilities provided by MRI to be available to a new group of previously denied patients. The safe use of this new device technology will require conscientious system-based care delivered by requesting physicians, cardiologists, MRI managers, MRI technologists and radiologists,” concluded the authors.
“Approximately 50 to 75 percent of the more than 1.5 million patients with implanted cardiac devices may have indications for MRI during the course of these devices,” wrote Patrick M. Colletti, MD, from the department of radiology at University of Southern California in Los Angeles, and colleagues.
The authors noted that the FDA has approved one MR-conditional system and predicted that others, already approved for use in Europe, will follow.
“The importance of appropriate MR-conditional pacemaker management cannot be overstated,” wrote Colletti et al, who provided guidance for radiologists and other healthcare professionals to ensure safe, diagnostic exams.
The first step, they said, is to consult with the referring physician to determine if another modality could offer the required diagnostic data. If MRI is the only suitable exam, physicians need to ensure that the pacemaker is labeled for MRI, properly implanted and that no other implanted devices are present.
After the cardiologist verifies the pacemaker history and system model, the pacemaker should be examined to verify appropriate thresholds.
Prior to the actual scan, a healthcare professional with MR-safe training needs to re-examine the system and specifications and set the pacemaker to the “on” mode. In addition, a professional with appropriate training must supervise the MRI study.
Colletti et al reiterated that the current system is limited to scans of the brain, skull base, upper neck and cervical spine, thoracolumbar spine, mid and lower abdomen, pelvic and lower extremities. The patient must be placed in the system head or feet first depending on the region to be scanned. Scans of the hands, wrist or elbow may be completed if the patient enters the scanner with his or her arm over the head. The authors added that the body radiofrequency coil should not be placed over the pacemaker.
MRI scans of patients with MR-conditional pacemakers are limited to 1.5T systems at a maximum gradient slew rate of 200 T/m/s per axis or less with the scanner in “normal operating mode.”
After the study, the pacemaker pulse generator should be turned off and the system should be re-checked to confirm normal function.
Given the complexities and risks among this population, “it is reasonable for all MRI providers to adjust their policies and procedures to either appropriately scan or decline to scan patients with MR-conditional pacemakers,” wrote Colletti and colleagues. They added that schedulers should be aware that such studies require prior notification and approval by a radiologist.
The authors issued a final caution, noting that scanning of pacemaker-dependent patients requires specific pulse generator settings. However, it is difficult to define such patients and predict the reliability of the underlying rhythm, necessitating careful monitoring to avoid complications.
“The introduction of MR-conditional cardiac devices enables the vital diagnostic capabilities provided by MRI to be available to a new group of previously denied patients. The safe use of this new device technology will require conscientious system-based care delivered by requesting physicians, cardiologists, MRI managers, MRI technologists and radiologists,” concluded the authors.