Contrast-to-Noise Ratio Performance of Dynamic Contrast-Enhanced CT Compared to 4D-CT for Liver Radiotherapy Planning
Abstract
Purpose
Radiotherapy planning for liver tumours remains challenging due to low tumour conspicuity and respiratory motion. This study explores the conditions under which dynamic contrast enhanced (DCE)-CT can be used to enhance tumour delineation for radiotherapy planning compared to a routinely utilized planning modality, 4D-CT.
Methods
Fifteen patients with a total of 18 intrahepatic tumours underwent DCE-CT (average, arterial, and portal phase) and respiration-tracked 4D-CT. Eight patients had primary hepatocellular carcinoma, and 7 patients had metastatic lesions with a total of 10 tumours originating from esophageal, breast, and colorectal primaries. Both DCE-CT and 4D-CT were performed at 120 kVp but with 1920 mAs and 600 mAs, respectively. The contrast-to-noise ratio (CNR) of each lesion was calculated across all image sets and compared using a two-sided paired Student’s t-test. Subgroup analyses were performed, separated by prior treatment status, tumour size, and primary versus metastatic origin.
Results
CNR was significantly higher for DCE-CT compared to 4D-CT on average and portal phase acquisitions (both p < 0.01), but was lower in the arterial phase (p = 0.016). Subgroup analyses demonstrated that CNR was significantly increased for lesions that were previously treated (p = 0.03), smaller than the cohort’s average size of 5.7 cm (p = 0.018), and metastatic in origin (p = 0.02).
Conclusion
DCE-CT can be used to improve tumour delineation for those that are small, metastatic, and previously treated. Although newer modalities such as 4D-MRI and MR-Linac are emerging for treatment planning, DCE-CT remains a more practical and accessible option, especially for centers without access to these newer imaging technologies.