AJR:198, January 2012
Ralph Gnannt, Michael Fischer, Robert Goetti, Christoph Karlo, Sebastian Leschka, Hatem Alkadhi
OBJECTIVE. The purpose of our study was to evaluate the accuracy of virtual unen-hanced images reconstructed from contrast-enhanced dual-energy CT for the differentiation of incidental adrenal masses in comparison with standard unenhanced CT.
MATERIALS AND METHODS. One hundred-forty patients (mean age, 74 ± 9 years) underwent unenhanced and contrast-enhanced CT of the abdomen, the latter acquired with dual-energy for reconstruction of virtual unenhanced images. Two blinded and independent readers (Rl and R2) measured attenuation of each incidental adrenal mass on standard un¬enhanced and virtual unenhanced images using an optimized dual-energy three-material de-composition algorithm.
RESULTS. Fifty-one incidental adrenal masses were found in 42 of 135 patients (31%); 39 incidental adrenal masses were > 1 cm. On the basis of unenhanced CT, 29 of 51 inciden¬tal adrenal masses and 22 of 39 incidental adrenal masses > 1 cm were classified as benign (HU < 10). Virtual unenhanced image quality was rated as good or with mild impairment (2.45 ± 0.83 for Rl, 2.45 ± 0.99 for R2). Image noise was 12.7 ± 3.6 HU in unenhanced imag¬es and 8.8 ± 2.0 HU in virtual unenhanced images (p < 0.001). There was no significant dif¬ference in incidental adrenal mass attenuation between unenhanced and virtual unenhanced images for all incidental adrenal masses (5.9 ± 21.0 HU vs 7.0 ± 20.6 HU, p = 0.48) and for those > 1 cm (6.6 ± 18.5 HU vs 7.9 ± 18.3 HU, p = 0.87). Sensitivity, specificity, and accuracy of virtual unenhanced images for the characterization of incidental adrenal masses as prob¬ably benign were 76%, 82%, and 78% for Rl and 79%, 95%, and 86% for R2, respectively. For incidental adrenal masses > 1 cm, sensitivity, specificity, and accuracy increased to 95%, 100%, and 97% for Rl and 91%, 100%, and 95% for R2.
CONCLUSION. Reconstruction of virtual unenhanced images from contrast-enhanced dual-energy CT of the abdomen allows the characterization of the incidental adrenal masses with a good accuracy compared with standard unenhanced CT, with the most favorable re¬sults in incidental adrenal masses measuring ≥ 1 cm.