Uterine leiomyoma: correlation between signal intensity on magnetic resonance imaging and pathologic characteristics.

To correlate the signal intensity of uterine leiomyoma with its pathologic characteristics, with particular emphasis on the fibrous component, 33 magnetic resonance (MR) examinations that revealed 93 leiomyomas were prospectively studied. All patients were imaged in axial and sagittal planes with different spin-echo pulse sequences to obtain T1-, T2-weighted, and proton density images. Nondegenerative leiomyomas (n = 62) showing a homogeneous signal of low intensity, and degenerative leiomyomas (n = 31) with a heterogeneous signal of variable intensity on T2-weighted images could be correlated. Histopathological assessment of fiber constitution and degeneration, and MR intensity were interpreted by independent observers. There was excellent accord between the averages for MR intensity, T2 relaxation time and fiber content, although the intensity values in each fiber grade showed a wide range. The greater the fiber content the lower the MR intensity on T2-weighted images, and the shorter the T2 relaxation time (p < 0.0001). In addition, the manner in which fiber distribution affected MR appearance was also elucidated. These data contribute guidelines for precise tissue differentiation of myogenic tumors on MR images, and for MR imaging tissue diagnosis of any lesion with a considerable fibrous element.