Limits...
Aortic 4D flow: quantifying the effects of contrast and field strength at 1.5 T, 3T and 7T

View Article: PubMed Central - HTML

AUTOMATICALLY GENERATED EXCERPT
Please rate it.

SNR in aortic 4D flow increases at 3T versus 1.5T (Strecker et al, JMRI 2012) and further by adding a contrast agent (Bock et al, MRM 2010)... This work extends this comparison to human 7 Tesla and quantifies the field strength dependent effects of contrast agents... At 7 T no RF spoiling was employed and a flip angle post B1 shimming ranging from 5° to 7° through the aorta. 7 T scans employed dynamic B1 shimming alternating between navigator and aorta specific shim... SNR was calculated by taking the difference of two symmetrically flow-encoded in one direction magnitude images (enc1 and enc3)... SNR = mean(enc1(, t) + enc3(, t))/√2 (std(enc1(, t) - enc3(, t))), is the spatial coordinate and t are the temporal frames during diastole... SNR was assessed in the descending aorta over a 40 × 7.5 mm× aorta diameter ROI centered 60 mm below the midpoint of the aortic arch... SNR for each of the six scans for each subject are plotted and a set of stream lines seeded in the LV (7 T data) are shown... The mean ± SD increase in SNR due to contrast agent is 1.8 ± 0.2, 1.8 ± 0.5 and 1.4 ± 0.2 for 1.5 T, 3 T and 7 T respectively... The mean ± SD increase in SNR due to field strength without and with the contrast agent is 1.8 ± 0.4 and 1.7 ± 0.1 for 1.5 T to 3 T and 2.1 ± 0.7 and 1.7 ± 0.4 for 3 T to 7 T... The average difference in peak net flow rate at the same location in descending aorta at 7 T compared to 3 T was 7 ± 7 ml/s... Of interest is that increases in SNR by stepping up in field strength are comparable to the increase from contrast. 4D aortic flow is feasible at 7 Tesla and yields substantial SNR improvements over lower field strengths... Future work will exploit this higher SNR to explore improved spatial and/or temporal resolution.

No MeSH data available.


Streamlines generated from a 7 T scan with contrast using software from Siemens and by seeding the streamlines in the left ventricle at 155 ms after the ECG R wave.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
getmorefigures.php?uid=PMC4044086&req=5

Figure 2: Streamlines generated from a 7 T scan with contrast using software from Siemens and by seeding the streamlines in the left ventricle at 155 ms after the ECG R wave.


Aortic 4D flow: quantifying the effects of contrast and field strength at 1.5 T, 3T and 7T
Streamlines generated from a 7 T scan with contrast using software from Siemens and by seeding the streamlines in the left ventricle at 155 ms after the ECG R wave.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4044086&req=5

Figure 2: Streamlines generated from a 7 T scan with contrast using software from Siemens and by seeding the streamlines in the left ventricle at 155 ms after the ECG R wave.

View Article: PubMed Central - HTML

AUTOMATICALLY GENERATED EXCERPT
Please rate it.

SNR in aortic 4D flow increases at 3T versus 1.5T (Strecker et al, JMRI 2012) and further by adding a contrast agent (Bock et al, MRM 2010)... This work extends this comparison to human 7 Tesla and quantifies the field strength dependent effects of contrast agents... At 7 T no RF spoiling was employed and a flip angle post B1 shimming ranging from 5° to 7° through the aorta. 7 T scans employed dynamic B1 shimming alternating between navigator and aorta specific shim... SNR was calculated by taking the difference of two symmetrically flow-encoded in one direction magnitude images (enc1 and enc3)... SNR = mean(enc1(, t) + enc3(, t))/√2 (std(enc1(, t) - enc3(, t))), is the spatial coordinate and t are the temporal frames during diastole... SNR was assessed in the descending aorta over a 40 × 7.5 mm× aorta diameter ROI centered 60 mm below the midpoint of the aortic arch... SNR for each of the six scans for each subject are plotted and a set of stream lines seeded in the LV (7 T data) are shown... The mean ± SD increase in SNR due to contrast agent is 1.8 ± 0.2, 1.8 ± 0.5 and 1.4 ± 0.2 for 1.5 T, 3 T and 7 T respectively... The mean ± SD increase in SNR due to field strength without and with the contrast agent is 1.8 ± 0.4 and 1.7 ± 0.1 for 1.5 T to 3 T and 2.1 ± 0.7 and 1.7 ± 0.4 for 3 T to 7 T... The average difference in peak net flow rate at the same location in descending aorta at 7 T compared to 3 T was 7 ± 7 ml/s... Of interest is that increases in SNR by stepping up in field strength are comparable to the increase from contrast. 4D aortic flow is feasible at 7 Tesla and yields substantial SNR improvements over lower field strengths... Future work will exploit this higher SNR to explore improved spatial and/or temporal resolution.

No MeSH data available.