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Surface/Specialty Coil Devices and Gating Techniques in Magnetic Resonance Imaging

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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.

Language: English.

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 usefulness.

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 resolution.

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