Computed tomography osteodensitometry of calvarial bone mineral density in skeletally healthy cats.

Introduction / Purpose: Metabolic bone disease can cause significant morbidity in cats. Calculation of bone mineral density (BMD) using quantitative computed tomography (qCT) is a novel tool. This retrospective study assesses the time requirements and ease-of-use of qCT and osteodensitometry software, establishing BMD reference values for skeletally healthy cats, and relationship between BMD and age, weight, sex and breed. Methods: Institutional archives were searched for computed tomography (CT) examinations of skeletally healthy cats including calvarial qCT and patient data. Calvarial BMD was calculated using a dedicated osteodensitometry software. In 50 cats time requirements for qCT and BMD analysis were recorded. Statistical analyses were performed using the R software system. Associations between BMD and categorical variables (breed, sex, and age group) were evaluated using the Kruskal-Wallis test. Correlations between BMD and body weight were assessed using the Spearman’s rank correlation. Results: Quantitative CT studies of 128 cases met the inclusion criteria. There were no associations between BMD and body weight, sex, age group or breed. The median BMD was 397.3 mg Calcium hydroxyapatite /mL. The mean duration of calvarial qCT scanning was 52.2s (9-174s), and the mean duration of BMD analysis was 13.7s (4-44s), with a mean of 1.1 (1-2) manual adjustments required for bone margin tracing. Discussion / Conclusion: Feline qCT BMD assessment of the calvarium can be performed in less than one minute, making it suitable as a routine part of the protocol for head CT scanning, providing information about skeletal health in cats.