Evaluation of relative wash-in ratio of adrenal lesions at early biphasic CT.
OBJECTIVE
The purpose of this study was to retrospectively evaluate the accuracy of unenhanced attenuation and relative percentage wash-in ratio in early, that is, arterial and portal venous phase, biphasic CT in differentiating adrenal adenomas from metastatic lesions.


METHODS
One hundred seven adrenal masses in 86 consecutively registered patients (45 men, 41 women; mean age, 56 years) were evaluated. Diagnosis was achieved with percutaneous biopsy (n = 6), surgery (n = 13), and at least 1 year of imaging follow-up (n = 88). Unenhanced, arterial phase, and portal phase scans were obtained. Diameter and absolute attenuation values in each phase of CT were measured in a region of interest covering one to two thirds of a lesion. Relative percentage wash-in ratio was calculated. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy in differentiation of adenomas from metastatic lesions were calculated for unenhanced attenuation and for wash-in ratio. A value of p < 0.05 was considered significant.


RESULTS
The final diagnosis was metastasis in 51 cases and adenoma in 56 cases. A significant difference was found between benign and malignant lesions in regard to diameter (p = 0.001), unenhanced CT attenuation (p = 0.001), and relative percentage wash-in ratio from the arterial to the portal venous scan (p = 0.014). In the differentiation of benign from malignant lesions, the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of unenhanced CT attenuation (at an 11-HU threshold) were 98%, 86%, 86%, 98%, and 92%, and those of relative percentage wash-in ratio from the arterial to the portal venous phase were 94%, 77%, 79%, 93%, and 85%.


CONCLUSIONS
Relative percentage wash-in ratio may help in differentiating adenoma from metastasis and in guiding the decision to perform CT directed at the adrenal glands when unenhanced CT is not available.
Foti
Giovanni
G
Department of Radiology G. B. Rossi Hospital, University of Verona, 37134 Verona, Italy. gfoti81@yahoo.it
Faccioli
Niccolò
N
Manfredi
Riccardo
R
Mantovani
William
W
Mucelli
Roberto Pozzi
RP
D000310:Adrenal Gland Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D018246:Adrenocortical Adenoma / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D001706:Biopsy; D016009:Chi-Square Distribution; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009362:Neoplasm Metastasis; D011237:Predictive Value of Tests; D011857:Radiographic Image Interpretation, Computer-Assisted; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D018709:Statistics, Nonparametric; D014057:Tomography, X-Ray Computed / Q000379:methods*