Comparison of Anatomical and Indication‐Based Diagnostic Reference Levels (DRLs) in Head CT Imaging: Implications for Radiation Dose Management

<b>Introduction:</b> Many diagnostic reference levels (DRLs) in computed tomography (CT) imaging are based mainly on anatomical locations and often overlook variations in radiation exposure due to different clinical indications. While indication-based DRLs, derived from dose descriptors like volume-weighted CT dose index (CTDI_vol) and dose length product (DLP), are recommended for optimising patient radiation exposure, many studies still use anatomical-based DRL values. This study is aimed at quantifying the differences between anatomical and indication-based DRL values in head CT imaging and assessing its implications for radiation dose management. This will support the narrative when explaining the distinction between indication-based DRLs and anatomical DRLs for patients' dose management. <b>Methods:</b> Employing a retrospective quantitative study design, we developed and compared anatomical and common indication-based DRL values using a dataset of head CT scans with similar characteristics. The indications included in the study were brain tumor/intracranial space-occupying lesion (ISOL), head injury/trauma, stroke, and anatomical examinations. Data analysis was conducted using SPSS Version 29. <b>Results:</b> The findings suggest that using anatomical-based DLP DRL values for CT head examinations leads to underestimations in the median, 25th percentile, and 75th percentile values of head injury/trauma by 20.2%, 30.0%, and 14.5% in single-phase CT head procedures. Conversely, for the entire examination, using anatomical-based DLP DRL as a benchmark for CT stroke DRL overestimates median, 25th percentile, and 75th percentile values by 18.3%, 23.9%, and 13.5%. Brain tumor/ISOL DL<i>P</i> values are underestimated by 62.6%, 60.4%, and 71.8%, respectively. <b>Conclusion:</b>The study highlights that using anatomical DLP DRL values for specific indications in head CT scans can lead to underestimated or overestimated DL<i>P</i> values, making them less reliable for radiation management compared to indication-based DRLs. Therefore, it is imperative to promote the establishment and use of indication-based DRLs for more accurate dose management in CT imaging.