Purpose: To demonstrate the characteristics of renal cystic lesions using dual-layer Spectral Detector CT (SDCT) and to determine the added value of spectral results.
Materials and Methods: 70 patients with at least one renal cystic lesion that underwent abdominpelvic examination on an SDCT were included in the study. Eighty-four lesions were categorized as hypo-attenuating (simple) and hyper-attenuating (complex or neoplastic) based on single-phase post-contrast images only. Attenuation in each lesion was measured on standard conventional images and the virtual monoenergetic images of 40keV and 100keV. A spectral curve slope was calculated. The iodine concentration in the lesions was measured using iodine-density map. Reference standard for each lesion type was established using histopathologic correlation, prior and follow-up imaging.
Results: Mean attenuation values for benign complex cysts and simple cysts differed significantly (41.7 ± 16.3 and 8 ± 3.2 HU, respectively; p<0.001). Iodine concentration in benign complex and simple cysts was almost identical (0.23 ± 0.04 mg/ml and 0.24 ± 0.04 respectively), while iodine concentration in malignant lesions was significantly higher (2.1 ± 0.08 mg/ml; p<0.001). The mean spectral curve slope did not differ significantly between benign simple and complex cysts (0.3 ± 0.03 and 0.33 ± 0.05 respectively) however was considerably higher in neoplastic lesions (2.6 ± 0.1; p<0.001).
Conclusion: Spectral properties obtained from SDCT are highly promising in distinguishing benign complex renal cysts from cystic neoplasm based on single-phase post-contrast imaging only.
