Challenges estimating patient organs doses undergoing enhanced chest CT examination: exploratory study

Area of Science:

• Medical Physics
• Radiology
• Radiation Dosimetry

Background:

• Estimating organ doses (ODs) in computed tomography (CT) is crucial for patient safety.
• Contrast enhancement in CT can influence organ doses, necessitating accurate estimation methods.
• Current methods for dose estimation may not fully capture the impact of contrast agents.

Purpose of the Study:

• To estimate organ doses (ODs) in patients undergoing unenhanced (S1) and enhanced (S2) chest CT.
• To compare the reliability of CT-EXPO simulation and Amato's phantom-based fitting model (APFM) in estimating dose increments due to contrast.
• To assess the relationship between Hounsfield Units (HUs) and OD increments.

Main Methods:

• Retrospective analysis of CT scans from 16 patients (unenhanced and enhanced chest CT series).
• Organ doses (liver, pancreas) estimated using CT-EXPO simulation and APFM.
• Hounsfield Units (HUs) quantified using regions of interest (ROIs); regression analysis and statistical tests (Spearman, Wilcoxon) performed.

Main Results:

• Significant differences in HUs and ODs between S1 and S2 were observed.
• CT-EXPO showed a higher OD difference than APFM for liver and pancreas.
• APFM demonstrated a strong correlation (R=0.99) between HUs and OD increments, unlike CT-EXPO (R=0.39-0.05).

Conclusions:

• CT-EXPO is unreliable for assessing dose impact from contrast enhancement.
• APFM accounts for contrast enhancement but provides only relative OD increments, limiting clinical utility.
• Further research is needed for accurate, clinically applicable methods to estimate contrast-enhanced CT organ doses.