Limits...
Influence of Off-resonance in myocardial T1-mapping using SSFP based MOLLI method.

Kellman P, Herzka DA, Arai AE, Hansen MS - J Cardiovasc Magn Reson (2013)

Bottom Line: A significant error in T1 may result at relatively small off-resonance frequencies that are well within the region without banding artifacts.For T1 = 1000 ms, the variation in T1 due to off-resonance variation was approximately 20 ms at 62 Hz, and > 50 ms at 125 Hz.Regional variations due to the inability to completely shim the B0-field variation around the heart appear as regional variation in T1, which is artifactual.

View Article: PubMed Central - HTML - PubMed

Affiliation: National Heart, Lung, and Blood Institute, National Institutes of Health, DHHS, Bethesda, MD 20892, USA. kellman@nih.gov

ABSTRACT

Background: Myocardial T1-mapping methods such as MOLLI use SSFP readout and are prone to frequency-dependent error in T1-measurement. A significant error in T1 may result at relatively small off-resonance frequencies that are well within the region without banding artifacts.

Methods: The sensitivity of T1-estimates based on the SSFP based MOLLI sequence to errors in center frequency are calculated by means of a Bloch simulation and validated by phantom measurements. Typical off-resonance errors following local cardiac shimming are determined by field mapping at both 1.5 and 3.0T. In vivo examples demonstrate the artifactual appearance of T1-maps in the presence of off-resonance variation.

Results: Off-resonance varied 61.8 ± 15.5 Hz (mean ± SD, n = 18) across the heart at 1.5T and 125.0 ± 40.6 Hz (mean ± SD, n = 18) at 3.0T. For T1 = 1000 ms, the variation in T1 due to off-resonance variation was approximately 20 ms at 62 Hz, and > 50 ms at 125 Hz.

Conclusions: Regional variations due to the inability to completely shim the B0-field variation around the heart appear as regional variation in T1, which is artifactual.

Show MeSH

Related in: MedlinePlus

Off-resonance error in T1 using MOLLI 5(3)3 protocol with 35 degree flip angle for a range of tissue T1 values with T2 = 45 ms, showing error in ms (top) and percent (bottom). The T1 error and sensitivity to off-resonance frequency increase for higher values of T1.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3733653&req=5

Figure 3: Off-resonance error in T1 using MOLLI 5(3)3 protocol with 35 degree flip angle for a range of tissue T1 values with T2 = 45 ms, showing error in ms (top) and percent (bottom). The T1 error and sensitivity to off-resonance frequency increase for higher values of T1.

Mentions: The off-resonance error in T1 is shown in Figure 3 for a MOLLI 5(3)3 protocol with 35 degree flip angle for a range of tissue T1 values with T2 = 45 ms. Error in ms is displayed on the top panel of Figure 3 and in percent on the bottom panel. The T1 error and sensitivity to off-resonance frequency increase for higher values of T1. At T1=1000 ms, measured T1 varied by 10ms (1%) across ± 50 Hz, and 20 ms (2.0%) across ± 75 Hz. This variation across frequency is in addition to the measurement error for on resonance tissue.


Influence of Off-resonance in myocardial T1-mapping using SSFP based MOLLI method.

Kellman P, Herzka DA, Arai AE, Hansen MS - J Cardiovasc Magn Reson (2013)

Off-resonance error in T1 using MOLLI 5(3)3 protocol with 35 degree flip angle for a range of tissue T1 values with T2 = 45 ms, showing error in ms (top) and percent (bottom). The T1 error and sensitivity to off-resonance frequency increase for higher values of T1.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3733653&req=5

Figure 3: Off-resonance error in T1 using MOLLI 5(3)3 protocol with 35 degree flip angle for a range of tissue T1 values with T2 = 45 ms, showing error in ms (top) and percent (bottom). The T1 error and sensitivity to off-resonance frequency increase for higher values of T1.
Mentions: The off-resonance error in T1 is shown in Figure 3 for a MOLLI 5(3)3 protocol with 35 degree flip angle for a range of tissue T1 values with T2 = 45 ms. Error in ms is displayed on the top panel of Figure 3 and in percent on the bottom panel. The T1 error and sensitivity to off-resonance frequency increase for higher values of T1. At T1=1000 ms, measured T1 varied by 10ms (1%) across ± 50 Hz, and 20 ms (2.0%) across ± 75 Hz. This variation across frequency is in addition to the measurement error for on resonance tissue.

Bottom Line: A significant error in T1 may result at relatively small off-resonance frequencies that are well within the region without banding artifacts.For T1 = 1000 ms, the variation in T1 due to off-resonance variation was approximately 20 ms at 62 Hz, and > 50 ms at 125 Hz.Regional variations due to the inability to completely shim the B0-field variation around the heart appear as regional variation in T1, which is artifactual.

View Article: PubMed Central - HTML - PubMed

Affiliation: National Heart, Lung, and Blood Institute, National Institutes of Health, DHHS, Bethesda, MD 20892, USA. kellman@nih.gov

ABSTRACT

Background: Myocardial T1-mapping methods such as MOLLI use SSFP readout and are prone to frequency-dependent error in T1-measurement. A significant error in T1 may result at relatively small off-resonance frequencies that are well within the region without banding artifacts.

Methods: The sensitivity of T1-estimates based on the SSFP based MOLLI sequence to errors in center frequency are calculated by means of a Bloch simulation and validated by phantom measurements. Typical off-resonance errors following local cardiac shimming are determined by field mapping at both 1.5 and 3.0T. In vivo examples demonstrate the artifactual appearance of T1-maps in the presence of off-resonance variation.

Results: Off-resonance varied 61.8 ± 15.5 Hz (mean ± SD, n = 18) across the heart at 1.5T and 125.0 ± 40.6 Hz (mean ± SD, n = 18) at 3.0T. For T1 = 1000 ms, the variation in T1 due to off-resonance variation was approximately 20 ms at 62 Hz, and > 50 ms at 125 Hz.

Conclusions: Regional variations due to the inability to completely shim the B0-field variation around the heart appear as regional variation in T1, which is artifactual.

Show MeSH
Related in: MedlinePlus