The Use of T1W BB Signal Intensity Difference Ratio In Assessing Myocardial Disease Involving Increasing Extracellular Volume: A Preliminary Study

Abstract

OBJECTIVE: To evaluate whether the new magnetic resonance imaging (MRI)technique related to T1 weighted black blood (T1W BB) signal intensity differenceratio between pre- and post- gadolinium contrast injection can serve as a potentialtechnique for use in differentiating normal and diseased myocardium involving theincreasing myocardial extracellular volume (ECV) in terms of sensitivity, specificityand accuracy in comparison with late gadolinium contrast enhancement (LGE) MRItechnique.MATERIALS AND METHODS: A retrospective analysis was conducted for a pilotof a total of 14 patients with known and suspected myocardial disease who underwenta cardiovascular magnetic resonance (CMR) scan at Bangkok Heart Hospital, Bangkok,Thailand in the period from September 2016-April 2017. LGE MRI and Spin echo T1WBB MRI in both pre- and post- contrast injection were performed in all patents on shortaxis view in the same slice position and number of slices. The myocardial signal intensitymeasurement on the T1W BB in both pre- and post- contrast injection images wereacquired on short axis view at the same region of interest (contrast enhancement regionand negative enhancement) on LGE MRI images. T1 signal intensity difference ratio(SDR) between pre- and post- contrast were calculated in both LGE positive andnegative groups. The mean T1W BB signal intensity difference ratio value > 30% wasclassified as abnormal increased ECV myocardium.RESULTS: The 14 study population have a mean age of 53.3±11.5 and are 64% male.Five were normal patients with negative LGE and nine were found to have myocardialdisease with positive LGE. A total of 61 sample slices on short axis view of theventricle of each T1W BB pre- and post- contrast were obtained from all patients, 31of 61 were from diseased myocardium with LGE positive scan and 30 were from normalmyocardium with a LGE negative scan. A myocardial T1 signal difference ratio > 30%was found in 2 of 30 slices of normal myocardium with the LGE negative group and 31of 31 slices of the LGE positive group. The mean signal difference ratio value of normaland diseased myocardium were 19.13±7.5 % and 41.4±7.6% respectively. The sensitivityand specificity and the accuracy of T1W BB difference ratio > 30% in differentiatingnormal from myocardium with involving increasing ECV were 100%, 93.3% and 96.7%(p=0.72) consecutively compared to the LGE MRI.CONCLUSION: The use of T1W BB in assessing myocardial diseases with either afocal or diffuse involvement demonstrates a higher value ratio of extracellular spacepre- and post- contrast study of more than 30% indicating myocardial disease with 100%sensitivity and 93.3% in specificity and 96.7% accuracy that is shown to be comparableto gold standard LGE technique in detecting focal increasing myocardial ECV bystatistic chi-square test p =0.72 (not less than 0.05)