Improved R2* measurements in myocardial iron overload

Open Access
Publisher Website
Google Scholar
Abstract
Purpose To optimize R2*(1/T2*) measurements for cardiac iron detection in sickle cell and thalassemia patients. Materials and Methods We studied 31 patients with transfusion‐dependent sickle cell disease and 48 patients with thalassemia major; myocardial R2* was assessed in a single midpapillary slice using a gated gradient‐echo pulse sequence. Pixel‐wise maps were coregistered among the patients to determine systematic spatial fluctuations in R2*. The contributions of minimum TE, echo spacing, signal‐decay model, and region‐of‐interest (ROI) choice were compared in synthetic and acquired images. Results Cardiac relaxivity demonstrated characteristic circumferential variations regardless of the degree of iron overload. Within the interventricular septum, a gradient in R2* from right to left ventricle was noted at high values. Pixel‐wise and ROI techniques yielded nearly identical values. Signal decay was exponential but a constant offset or second exponential term was necessary to avoid underestimation at high iron concentration. Systematic underestimation of R2* was observed for higher minimum TE, limiting the range of iron concentrations that can be profiled. Fat‐water oscillations, although detectable, represented only 1% of the total signal. Conclusion Clinical cardiac R2* measurements should be restricted to the interventricular septum and should have a minimum TE ≤ 2 msec. ROI analysis techniques are accurate; however, offset‐correction is essential. J. Magn. Reson. Imaging 2006.