High-dose dobutamine stress SSFP cine MRI at 3 Tesla with patient adaptive local RF shimming using dual-source RF transmission

Background Image quality of cine imaging using steady state free precession (SSFP) sequences at 3T is insufficient due to increased RF-inhomogeneity (B1 field) and the high sensitivity of SSFP sequences to off-resonance artefacts. Recently, the introduction of a dual source RF transmission system with patient-adaptive local RF-shimming has led to a significant improvement of image quality of SSFP imaging at 3T. The objective of this study was to prospectively evaluate the feasibility, image quality and diagnostic accuracy of high-dose dobutamine stress magnetic resonance imaging (DSMR) at 3T comparing dual-source versus single-source transmit technology.

High-dose dobutamine stress SSFP cine MRI at 3 Tesla with patient adaptive local RF shimming using dual-source RF transmission Alexander Berger 1* , Bernhard Schnackenburg 2 , Christopher Schneeweis 1 , Sebastian Kelle 1 , Christoph Klein 1 , Marc Kouwenhoven 3 , Eckart Fleck 1 , Rolf Gebker 1 From 15th Annual SCMR Scientific Sessions Orlando, FL, USA. 2-5 February 2012 Background Image quality of cine imaging using steady state free precession (SSFP) sequences at 3T is insufficient due to increased RF-inhomogeneity (B1 field) and the high sensitivity of SSFP sequences to off-resonance artefacts. Recently, the introduction of a dual source RF transmission system with patient-adaptive local RF-shimming has led to a significant improvement of image quality of SSFP imaging at 3T.
The objective of this study was to prospectively evaluate the feasibility, image quality and diagnostic accuracy of high-dose dobutamine stress magnetic resonance imaging (DSMR) at 3T comparing dual-source versus single-source transmit technology.

Methods
DSMR was performed in 44 patients with each participant undergoing cine imaging at rest and during dobutamine infusion using both dual-and single-source transmit technology.
B1-maps and measurements of contrast to noise ratio (CNR) were evaluated to quantify the effect of RF calibration in both transmission modes.
Analysis of image quality (0=non diagnostic, 1=severe artifact, 2=slight artifact, 3=no artifact) and wall motion was performed at rest and at maximum stress comparing single-and dual-source technology.
CAD was defined on invasive coronary angiography as the presence of ≥70% stenosis.

Results
The mean percentage of the intended flip angle within the heart increased from 88% ± 9.1 with single-source to 103% ± 5.6 with dual-source (p<0.001). Deviation of the flip angle from the base to the apex along the pseudo-long axis decreased from 29.8% ± 12.9% with single-source to 12.8% ± 7.2% with dual-source.
Image quality of dual-source was higher than singlesource both at rest (2.8 ± 0.5 vs. 2.6 ± 0.7, p<0.001) and stress (2.5 ± 0.7 vs. 2.0 ± 1.0, p<0.001). The number of segments with either severe artifacts or non-diagnostic image quality at stress was 27% using single-source compared to only 8% using dual-source (figure 1).

Conclusions
We demonstrated that using a dual-source transmit technology in a standard DSMR protocol is feasible in a 3T environment. Furthermore, the dual-source transmit technology provides better image quality and higher diagnostic accuracy compared to single-source transmit technology.
1 Department of Internal Medicine/Cardiology, German Heart Institute Berlin, Berlin, Germany Full list of author information is available at the end of the article Figure 1 Analysis of image quality of DSMR SSFP cine imaging at 3 Tesla. A significant difference existed between the number of segments with severe artifacts and no diagnostic segments comparing single-source and dual-source transmit technology both at rest and even more pronounced at maximum stress.