Detection of microscopic fat in adrenal adenomas: comparison of 2D dual gradient-echo MRI and 3D two-point Dixon techniques

Abstract

Background

Limited data exist comparing the detection of microscopic fat in adrenal adenomas on two-dimensional chemical shift dual-echo (2D CSI) magnetic resonance imaging (MRI) and three-dimensional two-point Dixon techniques (3D Dixon).

Purpose

To compare the sensitivity of 2D CSI versus 3D Dixon techniques for the diagnosis of adrenal adenomas.

Material and Methods

A retrospective analysis was conducted of 33 patients with adrenal masses who underwent both 2D CSI and 3D Dixon sequences on a 1.5-T scanner. Two blinded radiologists measured and calculated signal intensity (SI) index (SII) (100×(SI in phase – SI out of phase)/SI in phase) of nodules on each technique. Reference standard diagnosis of 30 adrenal adenomas was established. Sensitivity for adrenal adenoma diagnosis was determined using a SII >16.5%.

Results

In total, 33 nodules were investigated (mean size=22 mm, range=11–55 mm). Of the 30 adenomas, the mean SII on 2D CSI was 48% for reader 1 and 44% for reader 2, compared to 34% on 3D Dixon for both readers (P < 0.001). Sensitivity for the diagnosis of adenoma with 2D CSI was 90% (95% confidence interval [CI]=82–98) for both readers, while 3D Dixon demonstrated a sensitivity of 73% (95% CI=65–82) for reader 1 and 63% (95% CI=55–72) for reader 2.

Conclusion

2D dual gradient-echo CSI demonstrated a higher sensitivity for the diagnosis of adrenal adenoma than the 3D Dixon technique. Adrenal MRI evaluation of the adrenal glands at 1.5 T should include 2D dual gradient-echo CSI and not rely solely on 3D two-point Dixon techniques for the diagnosis of adrenal adenomas.