Figure 9a. Pathognomonic MR imaging features of endometrioma. (a) Axial T1-weighted spin-echo image (450/10) reveals high-signal-intensity cystic masses within the fallopian tubes. (b) Axial T2-weighted turbo spin-echo (4900/120) MR image demonstrates loss of signal intensity in the cystic masses. This phenomenon is called "shading" and occasionally occurs in a graded pattern, with higher to lower signal intensities as result of high protein content and iron concentration from recurrent hemorrhage.