Role of Photon Counting CT in Detecting Liver Metastatis From Colorectal Cancer

Colorectal cancer is the first leading cause of cancer death in men and second in women. Its incidence rates also increased by 1%-2% annually in young adults (ages \<55 years). The liver is the most common site of colorectal cancer metastasis, with approximately 25% 50% of patients developing liver metastases during the disease. Maximising resection of liver metastasis using all available techniques remains a key objective and provides the best chance of long-term survival and cure. For unresectable patients, optimal systemic and locoregional chemotherapeutic, biological and radiotherapeutic treatments improve survival, and may convert initially unresectable patients to operability. Computed Tomography is currently the modality of choice for patients staging and restaging for high spatial resolution providing accurate delineation of lesion, vascular structure and relation with surrounding structure. The portal venous phase (approximately 60-70 s after administration of contrast agent) is the most reliable phase for detection of liver metastasis with a detection rate of 85% with lower performance for lesion \<1 cm which are interpreted as too small to characterize. Compared to computed tomography, MRI has superior soft tissue contrast and the possibly of a multiparametric characterization of lesion thanks to the evaluation of diffusivity and the uptake of hepatospecific contrast media, resulting in higher accuracy also for lesion smaller than \< 10 mm. Photon-counting detector computed tomography (PCD-CT), used as standard clinical practice, by employing a reduced radiation dose, allows the acquisition of ultra-high resolution images (up to 169 microns) and spectral information, with a high detection rate of liver metastases and their characterization. Therefore, aim of the present study is to evaluate the value of PCD-CT in the detection of liver metastasis from colorectal cancer in comparison to MRI as reference standard.