Establishment of local diagnostic reference levels for adult chest CT examinations at a South African tertiary hospital in Gauteng province, South Africa.

Introduction: Computed tomography (CT) provides high-resolution three-dimensional images. However, there are concerns that CT delivers high patient doses. To mitigate risks, the International Commission on Radiological Protection introduced Diagnostic Reference Levels (DRLs) aimed at optimization of doses while maintaining acceptable image quality. This study established local DRLs for adult chest CT scans using dose length product (DLP) and volumetric CT dose index (CTDI_vol) doses at a tertiary hospital.

Materials and methods: A retrospective review of CTDI_vol and DLP values for 50 patients (≥18 years, weighing 70 ± 10 kg) who underwent non-contrast chest CT examinations. CT scan parameters were also documented. Median CTDI_vol and DLP doses were calculated as local DRLs, while the 75th percentile values were proposed as national DRLs for benchmarking with international studies. Independent samples t-test compared dose metrics between male and female patients. Statistical significance was set at p < 0.05.

Results: The median CTDI_vol values were 9.5 mGy and 10.8 mGy for females and males respectively (p = 0.18) while respective median DLP values were 370.8 mGy cm and 447.6 mGy cm (p = 0.02). The established local DRLs in terms of CTDI_vol and DLP were 10.4 mGy and 428.9 mGy cm respectively while the respective proposed national DRLs were 14.4 mGy and 622.2 mGy cm. CTDI_vol values were comparable to international DRLs while DLP values were higher.

Conclusion: The established local DRLs provide a baseline for optimizing adult chest CT practices at our institution and a first step toward establishment of national DRL standards in South Africa.