Inaccurate table height setting affects the organ-specific radiation dose in computed tomography

Area of Science:

• Medical Physics
• Radiological Sciences
• Diagnostic Imaging

Background:

• Accurate radiation dose assessment in computed tomography (CT) is vital for patient safety.
• The volume CT dose index (CTDIvol) is a standard metric, but its accuracy may be influenced by patient positioning and equipment variations.
• Understanding the impact of table height on localized absorbed doses is essential for refining CT protocols.

Purpose of the Study:

• To investigate the effect of inaccurate computed tomography (CT) table height on locally absorbed doses in organs and tissues.
• To evaluate the performance of auto table height correction (AHC) in maintaining dose metrics under varying table height conditions.

Main Methods:

• Utilized an anthropomorphic phantom with an integrated breast phantom to simulate patient anatomy.
• Varied the phantom's table height incrementally from -40 mm to +40 mm relative to the gantry center.
• Measured volume CT dose index (CTDIvol) and absorbed doses using glass dosimeters at different phantom locations, with and without auto table height correction (AHC).

Main Results:

• Absorbed doses to the lens and mammary gland showed significant deviations (-27.27% to 17.77% and -24.31% to 12.83%, respectively) compared to the gantry center position.
• Higher absorbed doses were observed in the lens and mammary gland at a table height of -40 mm.
• While auto table height correction (AHC) maintained consistent CTDIvol values across most table heights, slight reductions were noted at +40 mm.

Conclusions:

• Table height variations significantly impact organ-specific absorbed doses in CT.
• Auto table height correction (AHC) effectively standardizes the volume CT dose index (CTDIvol) but does not fully compensate for localized dose variations.
• Radiological technologists must ensure precise patient positioning, even when utilizing AHC, to optimize radiation dose management.