T2-prepared SSFP improves diagnostic confidence in edema imaging in acute myocardial infarction compared to turbo spin echo

Abstract

T2-weighted MRI of edema in acute myocardial infarction (MI) provides a means of differentiating acute and chronic MI, and assessing the area at risk of infarction. Conventional T2-weighted imaging of edema uses a turbo spin-echo (TSE) readout with dark-blood preparation. Clinical applications of dark-blood TSE methods can be limited by artifacts such as posterior wall signal loss due to through-plane motion, and bright subendocardial artifacts due to stagnant blood. Single-shot imaging with a T2-prepared SSFP readout provides an alternative to dark-blood TSE and may be conducted during free breathing. We hypothesized that T2-prepared SSFP would be a more reliable method than dark-blood TSE for imaging of edema in patients with MI. In patients with MI (22 acute and nine chronic MI cases), T2-weighted imaging with both methods was performed prior to contrast administration and delayed-enhancement imaging. The T2-weighted images using TSE were nondiagnostic in three of 31 cases, while six additional cases rated as being of diagnostic quality yielded incorrect diagnoses. In all 31 cases the T2-prepared SSFP images were rated as diagnostic quality, correctly differentiated acute or chronic MI, and correctly determined the coronary territory. Free-breathing T2 prepared SSFP provides T2-weighted images of acute MI with fewer artifacts and better diagnostic accuracy than conventional dark-blood TSE.

FIG. 1

Pulse sequence diagram for T₂-prepared single-shot SSFP imaging with acquisition of T₂-weighted data and reference data for B₁ maps used for parallel imaging autocalibration and surface-coil intensity correction: (a) ECG, (b) R-wave trigger, (c) T₂ preparation, (d) magnetization, and (e) data acquisition (during mid-diastole) for the i-th repetition.

FIG. 2

Acute-MI patient exhibiting edema in the LAD territory with true-positive imaging by both dark-blood TSE (left) and T₂-prepared SSFP (center). The delayed enhancement is shown at right. Arrows indicate regions of increased intensity.

FIG. 3

Acute-MI patient exhibiting edema with false-positive dark-blood TSE (left) showing apparently elevated T₂ in the LAD (incorrect) coronary territory but true-positive T₂-prepared SSFP (center) with elevated-T₂ in the RCA territory. The delayed enhancement shown at right is consistent with an MI in the RCA territory. This patient had significant RR variability. Arrows indicate regions of increased intensity.

FIG. 4

ECG waveform and corresponding R-R interval exhibiting significant R-R variation during a breath-hold for a patient corresponding to images shown in Fig 3. The R-R interval increased from 900 to 1305 ms.

FIG. 5

Acute-MI patient exhibiting edema in the LAD coronary territory with a nondiagnostic dark-blood TSE image but true-positive T₂-prepared SSFP image. The dark-blood TSE (left) was considered to be nondiagnostic with apparent elevated T₂ spanning two coronary territories. The T₂-prepared SSFP (center) showed elevated T₂ in the LAD territory, in agreement with delayed enhancement (right). Arrows indicate regions of increased intensity.

FIG. 6

Patient with chronic MI in the RCA territory is negative for edema with both dark-blood TSE and T₂-prepared SSFP in agreement. Left: dark-blood TSE; center: T₂-prepared SSFP; right: delayed enhancement. Images are surface-coil intensity-corrected. Arrows indicate regions of increased intensity.

FIG. 7

Patient with chronic MI in the LAD territory showing a false-positive dark-blood TSE (left) suggesting edema, but true-negative T₂-prepared TSE (center). Delayed-enhancement images are at right. Images are surface-coil intensity-corrected. Arrows indicate regions of increased intensity.

FIG. 8

Overall results for patients (N = 31) with both acute (N = 22) and chronic (N = 9) MI.

FIG. 9

Example illustrating bright-blood artifact for dark-blood TSE image (left) resulting from stagnant blood within trabeculae along endocardial wall. The corresponding T₂-prepared SSFP image (right) has no blood artifact.