3T 3D delivers fast myocardial viability assessment
The use of a 3D inversion recovery gradient-recalled echo (GRE) sequence at 3T MRI allows accurate assessment of myocardial infarction without loss of contrast-to-noise (CNR) ratio compared with a standard 2D technique, according to research published this month in the American Journal of Roentgenology.
The extent of viable myocardium in patients with ischemic cardiomyopathy plays a decisive role in predicting the long-term prognosis after coronary artery bypass grafting. Although nuclear medicine modalities such as SPECT and PET are regarded as the gold standard for distinguishing viable from nonviable myocardium; 3D 3T MRI may be a fast, alternative method for imaging myocardial viability with high spatial resolution.
“When using the 3D inversion recovery GRE sequence at 3T, certain advantages can be anticipated,” wrote the authors of a study conducted at the University Hospitals of Ludwig-Maximilian University in Munich, Germany. “Increased signal-to-noise ratio (SNR) and CNR may be obtained. Furthermore, the higher field strength offers the opportunity to increase spatial resolution.”
Researchers from the departments of radiology and cardiology at the facility sought to show that spatial resolution can be improved without loss of diagnostic accuracy if a 3D inversion recovery GRE sequence is used instead of a segmented inversion recovery GRE at 3T for the assessment of myocardial infarction.
A group of 15 patients who were suspected of having chronic myocardial infarction because of clinical or echocardiographic (ECG) findings were prospectively enrolled in the study from Jan. 2007 to May 2007 for the evaluation of size and transmural extent of myocardial infarction. The cohort consisted of 10 men and five women with a mean age of 58 years. The patients did not have unstable angina, New York Heart Association class III or IV, cardiac arrhythmia, or contraindications to MRI, the authors reported.
All examinations were conducted on a Siemens Healthcare 3T whole-body Magnetom Trio MR system, with all sequences ECG-triggered and performed using the breath-hold technique. Magnitude images of the 3D and 2D inversion recovery techniques were post-processed and reviewed to compare CNR, infarct volumes, the transmural extent of myocardial infarction and acquisition time.
The researchers found that the CNR in the 3D technique did not show any significant difference compared with the 2D technique. No significant difference was seen between the two techniques in infarction volume, and the assessment showed good correlation. In addition, the assessment of the presence of hyperenhanced myocardium in all segments and the evaluation of transmurality also resulted in very good agreement.
However, data acquisition time was significantly reduced with the 3D technique, 2.4 minutes, compared with the standard 2D technique, 4.9 minutes. In addition, the technique yielded higher spatial resolution.
“The combination of parallel imaging and improved array coil systems (32 elements) may allow a reduction in acquisition time for 3D imaging to a single breath-hold without loss of spatial resolution or even the higher, isovolumetric, spatial resolution and higher CNR at 3T,” the authors wrote.
Shorter acquisition times may also be advantageous for selection of optimal inversion times, the researchers noted. If data can be acquired in a short time, inversion time will vary less and may result in a more constant contrast.
The extent of viable myocardium in patients with ischemic cardiomyopathy plays a decisive role in predicting the long-term prognosis after coronary artery bypass grafting. Although nuclear medicine modalities such as SPECT and PET are regarded as the gold standard for distinguishing viable from nonviable myocardium; 3D 3T MRI may be a fast, alternative method for imaging myocardial viability with high spatial resolution.
“When using the 3D inversion recovery GRE sequence at 3T, certain advantages can be anticipated,” wrote the authors of a study conducted at the University Hospitals of Ludwig-Maximilian University in Munich, Germany. “Increased signal-to-noise ratio (SNR) and CNR may be obtained. Furthermore, the higher field strength offers the opportunity to increase spatial resolution.”
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| MR images of 67-year-old man with anteroseptal (arrow) and inferoseptal (arrowhead) myocardial infarction assessed with good agreement between 3D inversion recovery gradient-recalled echo (GRE) sequence in short-axis orientation (top row) and standard 2D |
Researchers from the departments of radiology and cardiology at the facility sought to show that spatial resolution can be improved without loss of diagnostic accuracy if a 3D inversion recovery GRE sequence is used instead of a segmented inversion recovery GRE at 3T for the assessment of myocardial infarction.
A group of 15 patients who were suspected of having chronic myocardial infarction because of clinical or echocardiographic (ECG) findings were prospectively enrolled in the study from Jan. 2007 to May 2007 for the evaluation of size and transmural extent of myocardial infarction. The cohort consisted of 10 men and five women with a mean age of 58 years. The patients did not have unstable angina, New York Heart Association class III or IV, cardiac arrhythmia, or contraindications to MRI, the authors reported.
All examinations were conducted on a Siemens Healthcare 3T whole-body Magnetom Trio MR system, with all sequences ECG-triggered and performed using the breath-hold technique. Magnitude images of the 3D and 2D inversion recovery techniques were post-processed and reviewed to compare CNR, infarct volumes, the transmural extent of myocardial infarction and acquisition time.
The researchers found that the CNR in the 3D technique did not show any significant difference compared with the 2D technique. No significant difference was seen between the two techniques in infarction volume, and the assessment showed good correlation. In addition, the assessment of the presence of hyperenhanced myocardium in all segments and the evaluation of transmurality also resulted in very good agreement.
However, data acquisition time was significantly reduced with the 3D technique, 2.4 minutes, compared with the standard 2D technique, 4.9 minutes. In addition, the technique yielded higher spatial resolution.
“The combination of parallel imaging and improved array coil systems (32 elements) may allow a reduction in acquisition time for 3D imaging to a single breath-hold without loss of spatial resolution or even the higher, isovolumetric, spatial resolution and higher CNR at 3T,” the authors wrote.
Shorter acquisition times may also be advantageous for selection of optimal inversion times, the researchers noted. If data can be acquired in a short time, inversion time will vary less and may result in a more constant contrast.