Correlation Between Breast Parenchymal Stiffness Measured by 3T Magnetic Resonance Elastography and CT-Derived Hounsfield Units

BACKGROUND Breast density and stiffness are imaging biomarkers that reflect tissue composition. Magnetic resonance elastography (MRE) quantifies tissue stiffness, whereas computed tomography (CT) attenuation in Hounsfield units (HU) shows parenchymal density. This study evaluated the relationship between MRE stiffness and CT attenuation in normal breast tissues. MATERIAL AND METHODS In this single-center study, 48 women (aged 29-56 years) who underwent breast magnetic resonance imaging (MRI) with routine 3T MRE and non-contrast chest CT within ±1 month were included. MRE was performed using a 3T scanner with a 19-cm internal pneumatic driver. The corresponding CT attenuation values were measured from the matched parenchymal regions. Correlation, regression, and tissue-specific reference analyses were performed. RESULTS MRE stiffness correlated strongly with CT attenuation (r=0.834, P<0.001). The regression model (kPa=2.402+0.009·HU+0.005·Age) explained 70.1% of the stiffness variance. Fibroglandular tissue showed higher stiffness (2.95±0.43 kPa) and HU (34.6±10.8) than fatty tissue (1.85±0.32 kPa and -89.7±17.3 HU, respectively; P<0.001).The reference stiffness ranges were 2.17-3.77 kPa for fibroglandular and 1.30-2.44 kPa for fatty parenchyma. CONCLUSIONS Breast parenchymal stiffness measured using 3T MRE correlates closely with CT attenuation, confirming that both parameters reflect complementary aspects of tissue density. These findings support MRE as a reliable non-invasive biomarker for quantitative breast tissue characterization.