Comparison of the region-based and pixel-wise methods for cardiac T2* analysis in 50 transfusion-dependent Thai thalassemia patients.

PURPOSE: To compare the observer variability of the conventional region-based (RB) to the typical and proposed pixel-wise (PW) methods for cardiac T2* analysis in thalassemia patients. DESIGN AND METHODS: Fifty thalassemia major patients were enrolled for the study. Short-axis bright- and black-blood sequences were acquired and analyzed using the RB and PW methods. Regions were defined using the whole septum (WS) or partial septum (PS). From the same PS region, results were reported by mean (PS-PW) and median (MPS-PW). Intraobserver and interobserver variabilities were investigated on all data set by 2 independent observers blinded to the result.
RESULTS: The T2* values from the PS-PW and MPS-PW methods were comparable to the conventional WS-RB method on both scanning techniques. When comparing the interobserver variability from the WS-RB to the PS-PW method, the coefficient of variation of the PS-PW method was equivalent (4.5% vs 4.7%, P = NS) for the bright-blood technique but 31% lower (4.0% vs 2.8%, P = 0.21) for the black-blood technique. The proposed MPS-PW method performed even better with respect to the conventional WS-RB method, decreasing interobserver coefficient of variation by 24% (4.5% vs 3.5%, P = 0.08) and 42% (4.0% vs 2.4%, P = 0.02), respectively. Intraobserver reproducibility followed the same trend.
CONCLUSIONS: The proposed PW method using the median of T2* values calculated from partial interventricular septum region provided lower intraobserver and interobserver variabilities compared with the conventional RB or typical PW methods.