Distinguishing adrenal adenomas from nonadenomas: combined use of diagnostic parameters of unenhanced and short 5-minute dynamic enhanced CT protocol.
OBJECTIVE
To retrospectively examine the diagnostic values of individual parameters obtained from unenhanced and 35-second and 5-minute contrast material-enhanced (enhanced) computed tomography (CT) in distinguishing adenomas, particularly lipid-poor adenomas, from nonadenomas and to determine the best diagnostic method by using these parameters.


METHODS
This retrospective study had institutional review board approval; the need for informed consent was waived. The study population consisted of 61 patients (20 men and 41 women; mean age, 58 years) with 68 adrenal masses (53 adenomas and 15 nonadenomas). In each patient, unenhanced CT was followed by 35-second and 5-minute enhanced CT. Adenomas were classified as 30 lipid-rich (<or=10 HU) and 23 lipid-poor (>10 HU) adenomas by using unenhanced attenuation. The diagnostic parameters were tumor size, unenhanced attenuation, 35-second and 5-minute enhanced attenuation, wash-in and washout attenuation, percentage enhancement washout ratio (PEW), and relative PEW (RPEW). The sensitivity, specificity, and accuracy for diagnosing adenomas were calculated by using a threshold level of each parameter determined by the least sum of false-positive and false-negative cases and a combination of the threshold levels with 100% specificity.


RESULTS
The best results were obtained by using a combination of the threshold levels with 100% (15 of 15) specificity (presence of at least one of the following criteria for diagnosing adenomas: unenhanced attenuation of <or=19 HU, 5-minute attenuation of <or=50 HU, PEW of >or=45%, and RPEW of >or=31%). Sensitivity was 94% (50 of 53) or 87% (20 of 23) and accuracy was 96% (65 of 68) or 92% (35 of 38) for diagnosing total adrenal adenomas or lipid-poor adenomas, respectively.


CONCLUSIONS
Combining the diagnostic parameters of the CT protocol can yield diagnostic results comparable to those with previously reported longer dynamic enhanced CT protocols.
Kamiyama
Takuro
T
Department of Radiology, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima, Japan. takuro3@m2.kufm.kagoshima-u.ac.jp
Fukukura
Yoshihiko
Y
Yoneyama
Tomohide
T
Takumi
Koji
K
Nakajo
Masayuki
M
D000293:Adolescent; D000310:Adrenal Gland Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D018246:Adrenocortical Adenoma / Q000000981:diagnostic imaging* / Q000473:pathology; D000328:Adult; D000368:Aged; D016009:Chi-Square Distribution; D003287:Contrast Media; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011857:Radiographic Image Interpretation, Computer-Assisted; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D018709:Statistics, Nonparametric; D014057:Tomography, X-Ray Computed / Q000379:methods*
D003287:Contrast Media