Spectral CT in renal cell carcinoma: the promising role of dual-energy and photon-counting techniques.

The expansion of cross-sectional imaging has led to a rise in the incidentally detected renal masses, including renal cell carcinomas (RCC). Though most incidentally detected renal masses are cysts, a clinical challenge is distinguishing cystic (often proteinaceous or hemorrhagic) from solid lesions, particularly when only a single phase examination is available. Spectral CT has the potential to offer advantages across different clinical applications in RCC. It has direct protocol implications, reducing the number of phases needed in CT urography or renal CT protocols, thereby lowering radiation dose while maintaining accuracy and cost-effectiveness. In addition, energy- and material-specific information can be extracted from a single data set, including quantitative data often regarded as surrogates of functional information (e.g., perfusion) that could be used to characterize renal lesions. Spectral CT imaging enables accurate distinction between cystic and solid renal masses. It could be a useful adjunct tool that improves characterization and monitoring, but it doesn't yet replace biopsy or histology, especially for subtype and grading, and may play an important role in post-treatment follow-up, assessment of therapy response, and differentiation of metastasis. Finally, PCCT offers the added advantages of improved spatial resolution and reduced contrast dose, image noise, and artifacts. PCCT may also enable new applications, such as K-edge imaging. The purpose of this article is to provide the reader with a summary of the technique's physics and its potential advantages, including both current and emerging applications in RCC.