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Improved precision in SASHA T 1 mapping with a variable flip angle readout

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The SAturation-recovery single-SHot Acquisition (SASHA) T1 mapping sequence has excellent accuracy independent of T1, T2, heart rate, and flip angle, which are known dependencies of the more commonly used MOdified Look-Locker Inversion-recovery (MOLLI) sequence... However, SASHA has a greater T1 variability (poorer precision) compared to MOLLI... We propose that a variable flip angle (VFA) readout will reduce these systematic errors and thereby allow the improved precision of a two-parameter fit while maintaining the accuracy of the three-parameter fit... SASHA, SASHA-VFA, and MOLLI T1 imaging was performed on 4 healthy volunteers (Siemens Aera 1.5T) on a mid-ventricular short-axis slice with typical bSSFP imaging readout parameters: 1.01/2.44 ms TE/TR, 8 mm slice thickness, 112 × 192 matrix size, 270 × 360 mmfield of view, rate 2 GRAPPA with 24 in-place ACS reference lines, 78% phase resolution, and 7/8 partial Fourier for a total imaging duration of ~175 ms... T1 pixel map were generated and the mean and standard deviation calculated for an ROI enclosing the entire LV myocardium... Two-parameter SASHA overestimated myocardial T1 as compared to the three-parameter fit but with reduced variability (Table 1)... Two-parameter SASHA-VFA showed similar mean T1 values to three-parameter SASHA and with substantially reduced T1 variability... Image artifacts from the bSSFP readout were consistently reduced with the SASHA-VFA sequence compared to the standard SASHA sequence, which may also contribute to the improved variability performance (Figure 1)... The SASHA sequence with VFA readout significantly reduces T1 variability and reduces image artifacts... The current study suggests that two-parameter SASHA-VFA maintains the accuracy of standard three-parameter SASHA with significantly reduced T1 variability, similar to the MOLLI sequence.

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Non-saturated images (top) and T1 pixel maps (bottom) for standard SASHA (left) and SASHA-VFA (right) in a healthy subject. An artifact (arrow) in the inferior right ventricular wall is seen in the non-saturated image for standard SASHA, but not for SASHA-VFA.
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Figure 1: Non-saturated images (top) and T1 pixel maps (bottom) for standard SASHA (left) and SASHA-VFA (right) in a healthy subject. An artifact (arrow) in the inferior right ventricular wall is seen in the non-saturated image for standard SASHA, but not for SASHA-VFA.

Mentions: Two-parameter SASHA overestimated myocardial T1 as compared to the three-parameter fit but with reduced variability (Table 1). Two-parameter SASHA-VFA showed similar mean T1 values to three-parameter SASHA and with substantially reduced T1 variability. Image artifacts from the bSSFP readout were consistently reduced with the SASHA-VFA sequence compared to the standard SASHA sequence, which may also contribute to the improved variability performance (Figure 1).


Improved precision in SASHA T 1 mapping with a variable flip angle readout
Non-saturated images (top) and T1 pixel maps (bottom) for standard SASHA (left) and SASHA-VFA (right) in a healthy subject. An artifact (arrow) in the inferior right ventricular wall is seen in the non-saturated image for standard SASHA, but not for SASHA-VFA.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4043358&req=5

Figure 1: Non-saturated images (top) and T1 pixel maps (bottom) for standard SASHA (left) and SASHA-VFA (right) in a healthy subject. An artifact (arrow) in the inferior right ventricular wall is seen in the non-saturated image for standard SASHA, but not for SASHA-VFA.
Mentions: Two-parameter SASHA overestimated myocardial T1 as compared to the three-parameter fit but with reduced variability (Table 1). Two-parameter SASHA-VFA showed similar mean T1 values to three-parameter SASHA and with substantially reduced T1 variability. Image artifacts from the bSSFP readout were consistently reduced with the SASHA-VFA sequence compared to the standard SASHA sequence, which may also contribute to the improved variability performance (Figure 1).

View Article: PubMed Central - HTML

AUTOMATICALLY GENERATED EXCERPT
Please rate it.

The SAturation-recovery single-SHot Acquisition (SASHA) T1 mapping sequence has excellent accuracy independent of T1, T2, heart rate, and flip angle, which are known dependencies of the more commonly used MOdified Look-Locker Inversion-recovery (MOLLI) sequence... However, SASHA has a greater T1 variability (poorer precision) compared to MOLLI... We propose that a variable flip angle (VFA) readout will reduce these systematic errors and thereby allow the improved precision of a two-parameter fit while maintaining the accuracy of the three-parameter fit... SASHA, SASHA-VFA, and MOLLI T1 imaging was performed on 4 healthy volunteers (Siemens Aera 1.5T) on a mid-ventricular short-axis slice with typical bSSFP imaging readout parameters: 1.01/2.44 ms TE/TR, 8 mm slice thickness, 112 × 192 matrix size, 270 × 360 mmfield of view, rate 2 GRAPPA with 24 in-place ACS reference lines, 78% phase resolution, and 7/8 partial Fourier for a total imaging duration of ~175 ms... T1 pixel map were generated and the mean and standard deviation calculated for an ROI enclosing the entire LV myocardium... Two-parameter SASHA overestimated myocardial T1 as compared to the three-parameter fit but with reduced variability (Table 1)... Two-parameter SASHA-VFA showed similar mean T1 values to three-parameter SASHA and with substantially reduced T1 variability... Image artifacts from the bSSFP readout were consistently reduced with the SASHA-VFA sequence compared to the standard SASHA sequence, which may also contribute to the improved variability performance (Figure 1)... The SASHA sequence with VFA readout significantly reduces T1 variability and reduces image artifacts... The current study suggests that two-parameter SASHA-VFA maintains the accuracy of standard three-parameter SASHA with significantly reduced T1 variability, similar to the MOLLI sequence.

No MeSH data available.


Related in: MedlinePlus