Eight echo T2 measurements of adrenal masses: limitations of differential diagnosis by relaxation time determination.
OBJECTIVE
Previous studies have revealed that benign and malignant adrenal masses differ in their T2-related MRI characteristics, but there is sufficient overlap in these characteristics that very accurate differential diagnosis is not possible. This ambiguity might be due to variations inherent in the measurement techniques or to real overlap in the T2 relaxation times of the lesion groups. We attempted to reduce the scatter and overlap of data from adenomas and malignancies by using an eight echo T2 assessment, which we compared with a two echo technique and with reference tissue brightness ratio determinations.


METHODS
Forty-eight adrenal masses in 44 adult patients were assessed; 30 were diagnosed as adenomas and 18 as malignancies by means other than MR. Each lesion was subjected to a single slice eight SE (spin echo) image (TR 2,000, TE 20-160), from which a T2 relaxation time was calculated. T2 relaxation times were also calculated using two echoes (TE 20 and 100), as were lesion/liver, lesion/fat, and lesion/muscle brightness ratios (TE 100). The differential diagnostic efficacies of the techniques were compared by receiver operating characteristic (ROC) analysis.


RESULTS
Although the means of the malignant and benign groups differed, significant overlap was present for each assessment technique. ROC analysis showed that the best differentiation was achieved by the lesion/fat brightness ratio, followed very closely by the eight echo technique. The eight echo technique was significantly better at differentiation than the two echo technique.


CONCLUSIONS
Although eight echo T2 determination has less variability and permits slightly better differential diagnosis than most other T2-dependent MR techniques, considerable ambiguity persists that may be due to intrinsic overlap in the T2 relaxation characteristics of the lesions rather than to variability in imaging techniques.
Gruss
L P
LP
Department of Radiology, Columbia-Presbyterian Medical Center, New York, NY 10032, USA.
Newhouse
J H
JH
D000236:Adenoma / Q000175:diagnosis; D000310:Adrenal Gland Neoplasms / Q000175:diagnosis*; D000328:Adult; D000368:Aged; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D012372:ROC Curve