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Temporal stability of gel relaxation-time phantoms for quality control of T1 and extracellular volume fraction measurements

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Well-known dependence of ECV estimation on imaging parameters requires quality-control by T1 phantoms... NiCl2-agarose gel phantoms were made by a reproducible lab procedure, developed to model T1 and T2 of myocardium and blood, native and post-contrast... These were kept in the MRI room and imaged weekly 10 times (Siemens, Avanto 1.5T) using consistent coil and phantom arrangement, with 11-RR MOLLI: high-resolution (heart-rate 75 bpm) and low-resolution (100 bpm) versions, with pre-contrast and post-contrast variants, plus spin-echo T2 (Figure 1)... Phantom mean T1 and T2 values were taken in pixelwise maps... The CoV (100 × Stdev/Mean)% of 10 weeks was compared against 10 re-positioned repeats... Neither accuracy nor magnetisation transfer were assessed in this study of long-term precision... The T1 and T2 values (Figure 2) show greater variation over 10 weeks (T1 CoV 1.1% over all measurements) than short-term (T1 CoV 0.2%)... No consistent drift was observed over 10 weeks... For long-term usefulness, phantom scans would need to be more stable than the ≈1/10th change in native-T1 and ECV in many applications, and this was supported by the initial results... The 10-week native T1- phantom CoVs were ≈2%, while "phantom ECV" (Hct 0.43) predictably showed smaller CoV ≈1%... Multi-slice data showed minimal variation with location in the gels... Adequate stability of phantoms was shown over 10 weeks to support their continued use in ascertaining long-term precision of T1 mapping.

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The T1 values are from 11-cycle 8-image faster MOLLI protocols: preGad 5(3)3 and postGad 4(1)3(1)2. These were repeated in high resolution (75 bpm) and low resolution (100 bpm) versions. The "overall CoV" stated in results is the average over all the CoVs(not all are shown). The "phantom ECV" was calculated using the averages of high and low-resolution T1s.
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Figure 2: The T1 values are from 11-cycle 8-image faster MOLLI protocols: preGad 5(3)3 and postGad 4(1)3(1)2. These were repeated in high resolution (75 bpm) and low resolution (100 bpm) versions. The "overall CoV" stated in results is the average over all the CoVs(not all are shown). The "phantom ECV" was calculated using the averages of high and low-resolution T1s.

Mentions: The T1 and T2 values (Figure 2) show greater variation over 10 weeks (T1 CoV 1.1% over all measurements) than short-term (T1 CoV 0.2%). The longer relaxation times showed more dependence on temperature. No consistent drift was observed over 10 weeks. For long-term usefulness, phantom scans would need to be more stable than the ≈1/10th change in native-T1 and ECV in many applications, and this was supported by the initial results. The 10-week native T1- phantom CoVs were ≈2%, while "phantom ECV" (Hct 0.43) predictably showed smaller CoV ≈1%. Multi-slice data showed minimal variation with location in the gels.


Temporal stability of gel relaxation-time phantoms for quality control of T1 and extracellular volume fraction measurements
The T1 values are from 11-cycle 8-image faster MOLLI protocols: preGad 5(3)3 and postGad 4(1)3(1)2. These were repeated in high resolution (75 bpm) and low resolution (100 bpm) versions. The "overall CoV" stated in results is the average over all the CoVs(not all are shown). The "phantom ECV" was calculated using the averages of high and low-resolution T1s.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4044048&req=5

Figure 2: The T1 values are from 11-cycle 8-image faster MOLLI protocols: preGad 5(3)3 and postGad 4(1)3(1)2. These were repeated in high resolution (75 bpm) and low resolution (100 bpm) versions. The "overall CoV" stated in results is the average over all the CoVs(not all are shown). The "phantom ECV" was calculated using the averages of high and low-resolution T1s.
Mentions: The T1 and T2 values (Figure 2) show greater variation over 10 weeks (T1 CoV 1.1% over all measurements) than short-term (T1 CoV 0.2%). The longer relaxation times showed more dependence on temperature. No consistent drift was observed over 10 weeks. For long-term usefulness, phantom scans would need to be more stable than the ≈1/10th change in native-T1 and ECV in many applications, and this was supported by the initial results. The 10-week native T1- phantom CoVs were ≈2%, while "phantom ECV" (Hct 0.43) predictably showed smaller CoV ≈1%. Multi-slice data showed minimal variation with location in the gels.

View Article: PubMed Central - HTML

AUTOMATICALLY GENERATED EXCERPT
Please rate it.

Well-known dependence of ECV estimation on imaging parameters requires quality-control by T1 phantoms... NiCl2-agarose gel phantoms were made by a reproducible lab procedure, developed to model T1 and T2 of myocardium and blood, native and post-contrast... These were kept in the MRI room and imaged weekly 10 times (Siemens, Avanto 1.5T) using consistent coil and phantom arrangement, with 11-RR MOLLI: high-resolution (heart-rate 75 bpm) and low-resolution (100 bpm) versions, with pre-contrast and post-contrast variants, plus spin-echo T2 (Figure 1)... Phantom mean T1 and T2 values were taken in pixelwise maps... The CoV (100 × Stdev/Mean)% of 10 weeks was compared against 10 re-positioned repeats... Neither accuracy nor magnetisation transfer were assessed in this study of long-term precision... The T1 and T2 values (Figure 2) show greater variation over 10 weeks (T1 CoV 1.1% over all measurements) than short-term (T1 CoV 0.2%)... No consistent drift was observed over 10 weeks... For long-term usefulness, phantom scans would need to be more stable than the ≈1/10th change in native-T1 and ECV in many applications, and this was supported by the initial results... The 10-week native T1- phantom CoVs were ≈2%, while "phantom ECV" (Hct 0.43) predictably showed smaller CoV ≈1%... Multi-slice data showed minimal variation with location in the gels... Adequate stability of phantoms was shown over 10 weeks to support their continued use in ascertaining long-term precision of T1 mapping.

No MeSH data available.