WE‐C‐103‐10: Lung Density Standard Reference for Medical Computed Tomography

Abstract

Purpose: To report to the quantitative imaging community that Standard Reference Material™ 2088, Density Standard for Medical Computed Tomography, is in the final stages of certification. The SRM 2088 can be used to determine the radiodensity scale in medical computed tomography (CT) in the range of lung tissue, partially supplementing the quantitative imaging effort championed by the Quantitative Imaging Biomarkers Alliance (QIBA) to specifically address the standardization of lung density measurements using CT. Methods: The SRM consists of a set of five rigid polyurethane foam blocks, approximately 5 cm × 4 cm × 2 cm, with densities ranging from 0.06 to 0.30 g/cm3 corresponding to HU values nominally from −950 and −695. A total of 200 blocks makes up the 40 packaged units, each containing 5 blocks of the 5 unique densities. Among these, 15 (3 from each density level) were randomly selected to have their physical density determined by SI traceable length and mass measurements. The measured densities of these blocks and their corresponding HU value obtained in a CT measurement serve as the calibration for assigning a density value to the entire 200 blocks. In addition, 3 units randomly selected were measured in the NIST standard beam qualities to obtain the mass attenuation coefficient. The linear attenuation coefficient, the lot averaged path length along the x‐ray beam, and the assigned mass density were used to obtain the mass attenuation coefficient. Results: Based on rigorous statistical analyses, all 200 blocks in the 40 units are issued a certified physical density in kg/m3, and the entire lot of the SRM is issued a mass attenuation coefficient, in kg/m2, for each of the four standard beam qualities. Conclusion: SRM 2088 allows an SI‐traceable calibration of densities observed in a CT in the density range of lung tissue.