Analysis of effective and organ dose estimation in CT when using mA modulation: A single scanner pilot study

Area of Science:

• Medical Physics
• Radiological Sciences
• Imaging Technology

Background:

• Effective dose (ED) estimation in CT examinations typically uses dose length product (DLP) with coefficients or software.
• Current methods often fail to account for tube current (mA) modulation, which varies with patient size.

Purpose of the Study:

• To compare various organ and ED estimation methods against measured values in CT chest, abdomen, and pelvis examinations utilizing mA modulation.
• To evaluate the impact of phantom mass corrections on ED estimation accuracy.

Main Methods:

• Organ doses were measured using digital dosimeters and a phantom in CT chest, abdomen, and pelvis scans.
• Six ED estimation methods incorporating mA modulation were applied using ImPACT CTDosimetry and DLP-to-ED coefficients.
• Twelve estimation methods were compared after applying phantom mass corrections.

Main Results:

• Calculated EDs were: chest 12.35 mSv, abdomen 8.74 mSv, and pelvis 4.68 mSv.
• All methods showed overestimation of ED, with corrections for phantom mass improving agreement.
• Organ dose estimations exhibited overestimation within the scan range and underestimation outside it.

Conclusions:

• ImPACT CTDosimetry software and k-coefficients provide reasonable ED estimates for CT chest and abdomen.
• Improved accuracy is needed for pelvic CT ED estimation.
• Organ dose estimation accuracy is significantly influenced by whether the organ is within the scan range.