Summary <p>In this study, we used routine ultra-low dose computed tomography scans of patients with cystic fibrosis to predict bone mineral density (BMD). A strong correlation was found between the attenuation of trabecular bone in thoracic vertebrae and the BMD in the proximal femur and lumbar spine as measured on DEXA.</p> Purpose <p>Osteoporosis is a serious global health concern with millions of people affected worldwide. A particularly vulnerable cohort in developing osteoporosis are patients with cystic fibrosis (CF). Bone mineral density (BMD) is typically measured with dual energy X-ray absorptiometry (DEXA) scanning; however, this comes at a cost to the healthcare system and an exposure to ionising radiation. In our institution, patients with cystic fibrosis undergo routine ultra-low dose computed tomography (ULDCT) for monitoring of disease progression. The aim of this study was to assess the validity of estimating BMD using data derived from ULDCT scans.</p> Methods <p>Adult CF patients were included if they had undergone a routine ULDCT scan within 12&#xa0;months of a DEXA scan. Additionally, 100 non-CF patients with non-contrast standard dose CT scans were selected to act as the control group. Trabecular bone density (T-BD) at T4, T7 and T10 was measured on PACS in Hounsfield units (HU) and compared to DEXA scan results and a formula developed to the predict BMD.</p> Results <p>Fifty-two female and 62 male patients were included with mean ages of 34.4 and 35.1 respectively. Moderately strong correlation was found between the T-BD and BMD of both the lumbar spine (<i>r</i> = 0.629, <i>p</i> &lt; 0.001) and proximal femur (<i>r</i> = 0.649, <i>p</i> &lt; 0.001). Receiver operator characteristic (ROC) curve analysis found a sensitivity and specificity of 0.700 and 0.714 respectively at predicting osteoporosis at T-BD of 193.33 HU or below.</p> Conclusion <p>T-BD measured on ULDCT may be a valuable tool in the early identification of CF patients at risk of osteoporosis.</p>