1350715 - A retrospective study by technologists to evaluate native T1 imaging with the aim of reducing routine gadolinium use

Recent literature evidence suggests that native T1 mapping can obviate the need for routine late gadolinium enhancement (LGE) imaging especially in specific cardiac conditions. However the routine use of T1 mapping as a gatekeeper to LGE imaging has not been tested in daily unselected clinical list. As majority of the scans worldwide are carried out by technologists, we aimed to assess if the technologists would be able assess the feasibility of native T1 mapping as a gatekeeper of LGE imaging.
 


Methods:

In this retrospective study the technologists assessed the native T1 mapping quantitative data from 26 anonymised studies. After a short training session on T1 mapping analysis, 3 radiographers with cardiac MRI experience ranging between 2 - 14 years, assessed 26 anonymised Cardiomyopathy studies. Native T1 maps positioned in the basal and mid ventricular short axis (SA) were analysed using semi-automated software CVI42 (Circle CVI, Calgary). The T1 values were recorded on the proforma for each study using the 17 segments AHA model. Normal range for the local scanner has been determined as 960ms-1100ms.

Following data collection, the T1 mapping results for each study was compared to the radiologist reports to collaborate the presence of LGE.
 


Results:

Of the 26 studies, 22 studies were positive for LGE. 4 studies had no LGE. Of the 22 LGE positive studies T1 maps were noted to be abnormal in 16 of them. 6 studies which were positive for LGE reported T1 maps within normal range. In 2 studies with abnormal T1 mapping results, there was no LGE noted in the report.

Where LGE was present, T1 maps were significantly more likely to be abnormal (73% 19/26) than normal (27% 7/26) (p=0.002).

where T1 was abnormal, there was no significant difference in prevalence of LGE (73% 19/26) vs no LGE (50% 13/26) (p=0.153).

The results are summarised in the following table:

 

Conclusion:

The results conclude that quantification of native T1 mapping in basal and mid ventricular slices alone is an unreliable technique to predict the presence of late Gad imaging.

Of the 26 studies that were positive for LGE, the technologist analysis showed abnormal native T1 mapping values in 73% of cases. It could be argued a contributing factor to this result was that only 2x native T1 mapping slices; one at the base of the LV and another in the middle of the LV (in the short axis plane) were used for this study. If a stack of contiguous T1 slices were acquired, perhaps with the addition of long axis slices, a greater amount of myocardium would be analysed and therefore more recordable data available. This would avoid LGE being reported in a region of the heart where T1 mapping has not been performed (due to the physical gap between the basal and mid slices). Further investigation into the use of native T1 mapping as a gatekeeper for LGE is recommended.