Assessment of image quality and establishment of local acceptable quality dose for computed tomography based on patient effective diameter.

Purpose: We aim to develop modified clinical indication (CI)-based image quality scoring criteria (IQSC) for assessing image quality (IQ) and establishing acceptable quality doses (AQDs) in adult computed tomography (CT) examinations, based on CIs and patient sizes.

Approach: CT images, volume CT dose index ( ${\mathrm{CTDI}}_{\mathrm{vol}}$ ), and dose length product (DLP) were collected retrospectively between September 2020 and September 2021 for eight common CIs from two CT scanners at a central hospital in the Kingdom of Bahrain. Using the modified CI-based IQSC and a Likert scale (0 to 4), three radiologists assessed the IQ of each examination. AQDs were then established as the median value of ${\mathrm{CTDI}}_{\mathrm{vol}}$ and DLP for images with an average score of 3 and compared to national diagnostic reference levels (NDRLs).

Results: Out of 581 examinations, 60 were excluded from the study due to average scores above or below 3. The established AQDs were lower than the NDRLs for all CIs, except $\mathrm{AQDs}/{\mathrm{CTDI}}_{\mathrm{vol}}$ for oncologic follow-up for large patients (28 versus 26 mGy) in scanner A, besides abdominal pain for medium patients (16 versus 15 mGy) and large patients (34 versus 27 mGy), and diverticulitis/appendicitis for medium patients (15 versus 12 mGy) and large patients (33 versus 30 mGy) in scanner B, indicating the need for optimization.

Conclusions: CI-based IQSC is crucial for IQ assessment and establishing AQDs according to patient size. It identifies stations requiring optimization of patient radiation exposure.