Purpose To evaluate the utility of amide proton transfer (APT) imaging in estimating histologic grades of endometrioid endometrial adenocarcinoma (EEA). Materials and Methods The institutional review board approved this prospective study. Between June 2012 and March 2016, 32 patients with EEA underwent magnetic resonance (MR) imaging. After their surgical procedures, their EEAs were confirmed pathologically and classified into histologic grades: grade 1 (n = 11), grade 2 (n = 11), and grade 3 (n = 10). The APT signal intensities (SIs) and the mean and minimum apparent diffusion coefficients (ADCs) of the three grades were calculated and compared. Spearman rank correlation coefficient was also calculated between the APT SIs and histologic grades, and between the ADCs and histologic grades. Results The Spearman correlation coefficient with histologic grade of the APT SIs, the mean ADC, and the minimum ADC were 0.55 (P = .001), 0.03 (P = .84), and -0.30 (P = .09), respectively. The average APT SIs and the mean and minimum ADCs were 2.2% ± 0.2 (standard deviation), 0.9 × 10^-3 mm²/sec ± 0.2, and 0.6 × 10^-3 mm²/sec ± 0.1 for grade 1; 3.2% ± 0.3, 0.8 × 10^-3 mm²/sec ± 0.1, and 0.5 × 10^-3 mm²/sec ± 0.1 for grade 2; and 3.7% ± 0.3, 0.9 × 10^-3 mm²/sec ± 0.1, and 0.5 × 10^-3 mm²/sec ± 0.1 for grade 3, respectively. The APT SIs of grade 3 EEA were significantly higher than those of grade 1 EEA (P = .01), but other pairwise comparisons did not reveal any significant differences (P = .06-.51). The mean and minimum ADCs showed no significant differences among the three histologic grades (P =.13-.51). Conclusion The APT SI was positively correlated with the histologic grades of EEA. ^© RSNA, 2017 Online supplemental material is available for this article.

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