Comparison of delayed enhanced CT and chemical shift MR for evaluating hyperattenuating incidental adrenal masses.
OBJECTIVE
To retrospectively compare the accuracy of delayed enhanced computed tomography (CT) and chemical shift magnetic resonance (MR) imaging for characterizing hyperattenuating adrenal masses at CT, with either follow-up imaging or pathologic review as the reference standard.


METHODS
The institutional review board approved this retrospective study with a waiver of patient informed consent. Forty-three hyperattenuating adrenal masses (>10 HU) on unenhanced CT images were found in 34 patients (23 men and 11 women; mean age, 52.7 years) by reviewing radiologic reports. These lesions were retrospectively analyzed with delayed enhanced CT and chemical shift MR. The diagnostic accuracy of CT by using absolute percentage loss of enhancement (PLE) and relative PLE and of chemical shift MR by using adrenal-to-spleen ratio (ASR) or signal intensity index (SII) were obtained to determine which modality was more accurate for lipid-poor adenoma. For CT, an adenoma was diagnosed if a mass had an absolute PLE greater than 60% and a relative PLE greater than 40%. For MR, an adenoma was diagnosed if a mass had an ASR of 0.71 or an SII greater than 16.5%. McNemar test was used to compare diagnostic performance of CT and MR.


RESULTS
Hyperattenuating adrenal masses included 37 adenomas and six nonadenomas. The sensitivity, specificity, and accuracy for adenoma at CT were 97% (36 of 37), 100% (six of six), and 98% (42 of 43), respectively, and at MR were 86% (32 of 37), 50% (three of six), and 49% (21 of 43), respectively. CT helped confirm five more adenomas and three more metastatic tumors than did MR. However, there was no significant difference for diagnostic accuracy between these two imaging modalities (P>.05)


CONCLUSIONS
Delayed enhanced CT can characterize additional hyperattenuating adrenal masses that cannot be characterized with chemical shift MR.
Park
Byung Kwan
BK
Department of Radiology and Center for Imaging Science, Samsung Medical Center, Sungkyunkwan University School of Medicine, 50 Ilwon-dong, Kangnam-ku, Seoul 135-710, Korea. rapark@skku.edu
Kim
Chan Kyo
CK
Kim
Bohyun
B
Lee
Jung Hee
JH
D000310:Adrenal Gland Neoplasms / Q000175:diagnosis*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D033162:Incidental Findings; D007472:Iohexol / Q000031:analogs & derivatives* / Q000627:therapeutic use; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*
D007472:Iohexol; C038192:iopromide