MultiTransmit 4D brings robustness to 3.0T cardiac imaging

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1 Publication for the Philips MRI Community Issue 44 SUMMER 2011 MultiTransmit 4D brings robustness to 3.0T cardiac imaging Bonn clinicians see a reduction in artifacts and inhomogeneities as a significant step forward in cardiac high-field applications. This article is part of FieldStrength issue 44 Summer 2011

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3 23 User experiences Daniel Thomas, MD, Section Chief Cardiac Imaging, Department of Radiology, University of Bonn. MultiTransmit 4D brings robustness to 3.0T cardiac imaging Bonn clinicians see a reduction in artifacts and inhomogeneities as a significant step forward in cardiac high-field applications. Bonn University has found MultiTransmit RF technology extends 3.0T imaging in cardiac applications and gives greater flexibility. For example, black blood TSE sequences are perceived to be more robust which benefits imaging of cardiomyopathies. MultiTransmit and the cardiac application The University of Bonn was one of the first to apply MultiTransmit in cardiac MR. Daniel Thomas, MD, attending radiologist and chief of cardiac imaging in the Department of Radiology, has worked with MultiTransmit in cardiac MR since its earliest conception. Dr. Thomas has also gained extensive experience on MultiTransmit with 3.0T spine and whole body imaging. The radiology department sees, for example, patients with congenital heart disease, patients referred for stress testing and patients with suspected cardiomyopathies. An important aspect of MR imaging here is to rule out, or confirm, myocarditis. CONTINUE FieldStrength 23

4 User experiences MultiTransmit advantages seen in black blood TSE and cine imaging Patient-adaptive MultiTransmit also called RF shimming provides a more homogeneous B1 field, which translates into a more uniform signal distribution in images and better image contrast. Also in 3.0T cardiac MR, MultiTransmit produces images with excellent uniformity. In cine images as well as black blood TSE, this results in better delineation of the myocardium versus the blood pool. Standing wave effects are now significantly reduced, especially beneficial in patients with cardiomyopathies, who often have large pleural effusion, says Dr. Thomas. Cardiac imaging team of University of Bonn. With MultiTransmit, the local SAR distribution is more homogeneous, and consequently shorter TR and TE can be selected than on standard 3.0T. The effect of a more homogeneous B1 field and shorter TR and TE is exciting; this benefits image quality as SNR and CNR increase and fewer black band artifacts are seen, says Dr. Thomas. In addition, with the optimized B1-field created by MultiTransmit, flip angles are more accurately reached. This will further improve SNR and CNR in B-TFE cine scans and will provide more homogeneous signal distribution. 3.0T Cardiac MR with MultiTransmit in myocarditis 45-year-old male with shortness of breath and chest pain since three days. He was treated for tonsillitis with antibiotics for one week. Elevated cardiac and infection parameters. Coronary angiography showed no significant coronary artery disease. B-FFE cine horizontal long axis B-FFE cine short axis B-FFE cine images show discrete hypokinesis of the left lateral free wall. PD-weighted images show focal edematous spots in the left mid-ventricular and apical left lateral free wall. Cardiac MRI helps confirm the diagnosis of myocarditis with focal patchy necroses. After immediate adequate treatment the patient did well. PDW PDW zoomed 24 FieldStrength - Issue 44 - Summer 2011

5 Using MultiTransmit I see far fewer and smaller artifacts than with standard 3.0T, especially with Balanced FFE imaging. The reduction of standing wave artifacts (dielectric shading) in the heart and specifically in the right ventricular (RV) free wall makes cardiac MR so much more robust, Dr. Thomas explains. He finds that MultiTransmit makes 3.0T more flexible and extends the use of cardiac applications. His next step is to exploit further the use of MultiTransmit in cardiac, and to translate these findings into a clinical benefit. In cardiac MR, the main advantages of MultiTransmit are seen in black blood images using TSE, and cine imaging. Dr. Thomas stresses that in cardiac applications the advantages of MultiTransmit are slightly different compared with other body regions. We have seen an increase in image homogeneity and contrast, although the increase in speed is less in cardiac gated and breath hold TSE sequences, compared to, for example, spine imaging, where SAR issues translate into increased imaging time for TSE sequences. However, a slight increase in cine speed is seen, where improved SAR management does allow for a shorter TR and TE. This gain in speed compared to standard 3.0T may be used to reduce breath hold duration by 1 to 3 seconds, (depending on the scan parameters), which makes a difference for patients with problems holding their breath. Another benefit is that the TR reduction reduces the susceptibility to dark-band artifacts, Dr. Thomas concludes. NetForum Visit NetForum for more details and movies of clinical cases. Cardiac MultiTransmit 4D is currently available for Ingenia 3.0T only. B-FFE B-FFE T2 TSE STIR MultiTransmit Cardiac MR of acute myocardial infarction 39-year-old male with retrosternal burning, ECG without abnormalities. Cardiac biomarkers elevated. Coronary angiography revealed chronic occlusion of left circumflex artery and acute occlusion of the right coronary artery, most likely based on a subtotal stenosis. Attempts of interventional recanalization were unsuccessful. Patient was referred to cardiac MR prior to bypass surgery. The B-FFE cine images show akinesis and hypokinesis of the basal and midventricular inferior, inferolateral and inferoseptal segments. Hypokinesis can also be found in anterolateral segments. T2 TSE STIR imaging shows a mainly basally localized myocardial edema of the lateral wall. Diagnosis is acute myocardial infarction mainly in the territory of the right coronary artery. Patient received coronary bypass grafts. Postoperatively LV function improved (EF 56% vs. 46%). Note the excellent signal uniformity provided by MultiTransmit. FieldStrength 25