Article ID: mp.2024-0066
Purpose: To evaluate short T2 components potentially reflecting calcification or other susceptibility-affected tissue components in atherosclerotic plaques, using multicomponent analysis with ultrashort TE (UTE) MRI.
Methods: A phantom experiment was conducted using a 4-echo UTE sequence, mimicking the sample as a small amount of calcification found intra-voxel. The phantom included 6 samples containing varying concentrations of hydroxyapatite (calcification) and mayonnaise (lipid–water emulsion). Data acquired from the UTE sequence were compared with those obtained using a conventional multi-echo gradient-echo (mGRE) method.
Results: Bi-exponential analysis of UTE data successfully separated short- and long-T2* components, with ranges of 0.44–4.81 ms and 4.29–24.37 ms, respectively. Short T2* values derived from UTE showed minor changes with increasing hydroxyapatite concentration. Using bi-exponential analysis of mGRE data, short and long T2* values ranged from 0.17–0.77 ms and 6.16–39.20 ms, respectively. For mono-exponential fitting of mGRE data, T2* values ranged from 4.84–38.32 ms. In all datasets, 1/T2* increased with hydroxyapatite concentration. The signal fraction of short T2* components in the UTE dataset decreased as hydroxyapatite concentration increased. A clinical scan of 1 patient with an atherosclerotic plaque yielded mean short and long T2* values of 0.12 ± 0.35 ms and 33.22 ± 17.25 ms, respectively.
Conclusion: T2* analysis using UTE data enabled the separation of mixed calcification and mayonnaise (lipid–water emulsion) within a sample into 2 components and detected short T2* components that may reflect calcification-related susceptibility effects, without directly indicating calcification. Multicomponent T2* analysis with UTE-MRI is a promising technique for evaluating calcification and other short T2* components in atherosclerotic plaques.
