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Title: Surface/Specialty Coil Devices and Gating Techniques in Magnetic Resonance Imaging.
Agency: Agency for Health Care Policy and Research/Center for Health Care Technology
(Formerly, the Office of Health Technology Assessment).
Contact: Martin Erlichman, M.S., Senior Health Science Analyst.
Status: Technology Assessment: Published, 1990.
Primary Objective: Scientific evaluation of the safety and clinical effectiveness of surface and
other specialty coil devices and gating techniques in conjunction with MRI procedures.
Methods Used: Synthesis of published literature and information solicited from Public Health
Service agencies and professional societies and organizations.
Data Identification: English language journal articles and textbooks published between 1980 and
1988 available through the search capabilities of the National Library of Medicine. Key Words:
"MRI," "Surface Coils," "Gating," "Respiratory Gating."
Study Selection: 19 studies contained information regarding differences in the signal-to-noise
ratio for MR images utilizing body coil vs surface coil. 24 studies contained information of the
differences in gated and ungated MR images regarding artifacts, distortions and signal loss.
Data Extraction: Demonstrated that MR images were enhanced (resolution) by changes in
signal-to-noise ratio. Demonstrated that MR images were enhanced by elimination of movement
artifacts that cause degradation of the signal and associated blurring.
Key Results/Findings: Surface coils improve image quality compared with body coils by virtue
of the improved signal-to-noise ratio, which results in better anatomic detail and tissue contrast. A
greater signal-to-noise ratio can be traded for better spatial resolution or reduced scanning time.
Gating techniques eliminate or reduce movement artifacts causing degradation of the RF signal
and associated blurring of the image. Cardiac gated imaging has enabled the acquisition of high
resolution diagnostic quality cardiac images with conventional MRI. It also has been found
valuable in reducing motion artifacts in MRI of the chest, brain, spine, and liver. Although
respiratory gating improves thoracic and abdominal imaging, the inherent time delays limit its
Conclusions: Surface and other specialty coils enhance the quality of MR images, particularly for
small structures that require greater spatial resolution. Gating enhances the quality of MR images
of structures that are not stationary by reducing motion artifacts and improving temporal