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Cardiac MR Imaging with External Respirator: Synchronizing Cardiac and Respiratory Motion—Feasibility Study¹

¹ From the Cardiac Magnetic Resonance Unit (S.P., S.B., T.R.J., G.J.B., M.U.S.) and Department of Medical Physics (J.P.R.), General Infirmary at Leeds, Great George St, Rm 170, D-floor, Jubilee Wing, Leeds LS1 3EX, England. Received February 25, 2002; revision requested April 24; final revision received August 29; accepted September 30. S.P. supported by a British Heart Foundation Research Fellowship. Address correspondence to S.P. (e-mail: sven.plein@leedsth.nhs.uk).

View larger version (33K): [in a new window]   Figure 1a. Setup of external respirator for MR imaging. (a) Schematic setup. (b) Setup with a volunteer. 1 = cuirass, 2 = foam seal, 3 = flexible tubing, 4 = hook and loop straps, 5 = cardiac receiver coil, 6 = ECG electrodes, 7 = pressure transducer.

View larger version (111K): [in a new window]   Figure 1b. Setup of external respirator for MR imaging. (a) Schematic setup. (b) Setup with a volunteer. 1 = cuirass, 2 = foam seal, 3 = flexible tubing, 4 = hook and loop straps, 5 = cardiac receiver coil, 6 = ECG electrodes, 7 = pressure transducer.

View larger version (20K): [in a new window]   Figure 2. Schematic representation of synchronized data acquisition at coronary MR angiography with use of the external respirator (RTX). The respirator is set to generate a short end-expiratory phase in early systole and a slow inspiratory phase in diastole. Data are acquired in diastole, when both the coronary motion in the cardiac cycle and the respiratory motion are minimal.

View larger version (157K): [in a new window]   Figure 3. Images from a multiphase data set. Left: End-diastolic images. Right: End-systolic images. Top: Conventional acquisitions. Bottom: Respirator-triggered acquisitions. Images obtained in both acquisitions were scored as having good image quality, and objective measurements showed no substantial differences. Arrows indicate the distance between chest wall and diaphragm. In the conventional images, this distance remains unchanged between diastole and systole. In the respirator-triggered images, the distance is shorter in systole, which reflects chest compression in inspiration.

View larger version (84K): [in a new window]   Figure 4. Double-oblique MR angiograms show single sections of the right coronary artery (RCA). Left: Image acquired conventionally without the use of the external respirator. Right: Image acquired with the external respirator switched on. Total imaging time for the respirator-triggered acquisition was 45% of that for the conventional acquisition. Navigator efficiency was 95% with the respirator. Both images were scored as 2 (good).