Exhibit Hall | Forum 8
Purpose: Studies of tin spectral filtration in CT colonography (CTC) and CT lung cancer screening (CTLCS) have demonstrated its potential of reducing radiation dose while maintaining image quality. The extent of dose reduction however was often quantified using CTDI(vol). The purpose of this study was to investigate the effect of tin filtration on patient organ and effective dose.
Methods: The study included 53 computational patient models from the extended cardiac-torso family (weight: 57-130 kg). A Monte Carlo program was developed and validated for a 96-row CT scanner (Somatom Force, Siemens Healthineers). For each patient model, the program simulated CTC scans of the abdomen-pelvis using three different spectra: 120 kVp, 100 kVp with tin (100Sn), and 150 kVp with tin (150Sn). The same procedure was repeated to simulate CTLCS scans of the chest. CTDI(vol)-normalized organ doses and DLP-normalized effective doses were compared between the different spectra.
Results: For all CTC and CTLCS scans, effective and organ doses increased with increasing beam-hardness (120kVp, 100Sn, 150Sn). For CTC, the median increase in effective dose between 120kVp and 100Sn was 11.5%, with organ dose increases of 9.1%, 10.0%, 10.8%, and 3.5% to colon, liver, stomach, and skin, respectively. Median increase in effective dose between 120kVp and 150Sn was 20.9%, with organ dose increases of 15.6%, 17.3%, 18.5%, and 10.3% to the same organs, respectively. For CTLCS, the median increase in effective dose between 120kVp and 100Sn was 9.0%, with organ dose increases of 7.8%, 5.4%, 14.6%, and 3.1% to lungs, breast, thyroid, and skin, respectively. Median effective dose increase between 120kVp and 150Sn was 19.5%, with organ dose increases of 16.0%, 18.0%, 26.4%, and 12.0% to the same organs, respectively.
Conclusion: Results suggest dose conversion factors are greater using tin filtration and these differences should be considered when evaluating potential dose reduction using tin.
Funding Support, Disclosures, and Conflict of Interest: This project is funded by a research grant from Siemens Healthineers.