Impact of Patient-Specific Size Factors on Dosimetry Measurements: A Comparison of IndoseCT and Phantom-Based CT-Expo

<title>Abstract</title> <p> Background organ dose and effective dose ( <italic>E</italic> ) in computed tomography (CT) are of great concern due to the increasing number of CT examinations. Most organ dose and <italic>E</italic> estimation software assumes a standard patient size, while some use weight and length factors. IndoseCT, on the other hand, estimates organ dose and <italic>E</italic> by accounting for patient size, using the size-specific dose (SSDE). Objectives To date, no direct comparison has been made between software that accounts for patient size (IndoseCT) and software that assumes a standard patient (CT‑Expo). Consequently, the accuracy of IndoseCT for organ dose and <italic>E</italic> remains unvalidated, as no published study has specifically compared IndoseCT with other software platforms. Methods 218 patients (124 males and 94 females) underwent Brain CT in 3 radiology units using 3 scanners: Philips, Siemens, and General Electric (GE). The patients were scanned using brain CT protocols. The organ dose and <italic>E</italic> were calculated using IndoseCT and compared with CT-Expo. Results The average male brain organ dose calculated using IndoseCT was 36.41 mGy, while the calculated brain organ dose using CT-Expo was 42 mGy, without a significant difference p-value &gt; 0.001. For females, the average brain dose calculated using IndoseCT was 33.68 mGy, and the average calculated using CT-Expo was 40.83 mGy, with no significant difference (p-value &gt; 0.001). IndoseCT and CT-Expo showed a significant difference (p-value &lt; 0.001) for the other organs and <italic>E</italic> . However, the percentage difference between IndoseCT and CT-Expo falls within the range reported in the literature for studies comparing various software for assessing organ dose and <italic>E</italic> . Conclusion Size-specific factors are valuable for estimating organ dose and <italic>E</italic> . The observed differences between IndoseCT and CT‑Expo arise primarily because CT‑Expo assumes a standard patient with a constant body size, whereas IndoseCT accounts for patient size, yielding more accurate dose estimates. </p>