Comparative evaluation of absorbed doses in silver wedge-filter-based chest CT versus chest radiography: A Monte Carlo study

In the silver (Ag) wedge-filter-fitted computed tomography (CT) scanner, we estimated organ doses during chest CT examinations and chest radiography to assess the Ag-filter-based dose reduction in six scan protocols for chest CT: three conventional protocols with standard filters (clinical standard, low-dose, and ultra-low-dose) and three corresponding Ag-filter-based protocols; the tube current was adjusted to maintain similar standard deviations (SD) and two protocols for chest radiography: posteroanterior (PA) projection (medical checkups) and posteroanterior with right-left (PA + RL) projection (clinical protocols). Using the Monte Carlo simulation software (ImpactMC), we estimated absorbed doses by simulating photon transport in computational phantoms (adult males and females) based on average values for organ doses (lungs, breast tissue, heart, stomach, and liver) and the maximum value for the skin dose. Despite similar SD, the organ and tissue doses in the Ag filter-based ultra-low-dose chest CT protocol (vs. no-Ag filter) were lower for females: skin (39.6 %), lung (17.4 %), breast tissue (20.1 %), heart (16.5 %), stomach (14.4 %), and liver (16.7 %), with similar dose reductions across other scan protocols. In the ultra-low-dose Ag-filter-based chest CT protocol, the absorbed doses resembled those of PA + RL radiography (clinical protocol). During chest CT examinations, the Ag filter-based effective reduction of the radiation dose conferred a potentially significant impact on the risk–benefit balance in CT-based lung cancer screening; this potentially influences the screening targets and overall effectiveness. By balancing radiation risk and diagnostic benefits, the Ag filter facilitates a paradigm shift from radiography to ultra-low-dose CT examinations in conventional diagnosis and follow-up.