Accuracy of magnetic resonance imaging and transvaginal ultrasonography in the diagnosis, mapping, and measurement of uterine myomas

OBJECTIVE: The purpose of this study was to evaluate and compare the accuracy of magnetic resonance imaging and transvaginal ultrasonography in myoma diagnosis, mapping, and measurement. STUDY DESIGN: This was a double-blind study of 106 consecutive premenopausal women who underwent hysterectomy for benign reasons. Myomas (total, 257) were exactly mapped by magnetic resonance imaging and transvaginal ultrasonography; in each patient, we counted correctly identified myomas with pathologic position as true value. RESULTS: The presence of myomas was detected with the same high level of precision by both methods (magnetic resonance imaging: sensitivity, 0.99; specificity, 0.86; transvaginal ultrasonography: sensitivity, 0.99; specificity, 0.91). The mean number of correctly identified myomas was significantly higher by magnetic resonance imaging than by transvaginal ultrasonography (mean difference, 0.51 +/- 1.03; P < .001), a difference that narrowed to 0.08 +/- 0.76 (P = .60) in 26 patients with 1 to 4 myomas and uterine volumes <375 mL. Magnetic resonance imaging and transvaginal ultrasonography myoma diameter measurements had equal and high accuracies in patients with 1 to 4 myomas. CONCLUSION: Transvaginal ultrasonography is as efficient as magnetic resonance imaging in detecting myoma presence, but its capacity for exact myoma mapping falls short of that of magnetic resonance imaging, especially in large (>375 mL) multiple-myoma (>4) uteri.