A method for determining data defining an estimate of the thickness and density of a cortical bone tissue structure of interest from clinical low resolution imaging data, the method comprising: a) determining a variable thickness-density relationship between cortical bone tissue structure density and cortical bone tissue structure thickness; b) providing measured variations of an imaging parameter of said clinical low resolution imaging data defining at least one representation of a region of bone tissue of a patient including said cortical bone tissue structure of interest, said variations being measured along a line crossing said cortical bone tissue structure of interest and being representative of variations of bone tissue structure density; c) modelling said variations of said imaging parameter along said line as a function having at least one parameter defining said thickness of said cortical bone tissue structure of interest along said line, at least a first density parameter defining said density of said cortical bone tissue structure of interest along said line and at least one parameter representing the blur of said imaging data; and d) fitting said function to said measured variations of said imaging parameter, wherein said fitting comprises searching for optimal values for said at least one parameter representing the blur of the said imaging data, for said at least one parameter defining said thickness of said cortical bone tissue structure of interest and for said at least first density parameter defining said density of said cortical bone tissue structure of interest, while ensuring said at least first density parameter and said at least one parameter defining said thickness to substantially follow said variable thickness-density relationship; wherein said optimal values for said at least one parameter defining said thickness of said cortical bone tissue structure of interest and for said at least first density parameter comprise, respectively, data defining said estimate of said thickness and data defining said estimate of said density of the cortical bone tissue structure of interest; characterised in that the method comprises determining, at step a), said variable thickness-density relationship from measured variations from multiple thickness and density measurements made on reference imaging data, which are high resolution imaging data, of a reference cortical bone tissue structure of a subject which is not said patient, wherein said multiple thickness and density measurements include thickness and density measurements made on thin cortex regions of said reference cortical bone tissue structure, wherein said thin cortex regions have thicknesses below 3 mm. a) determining a variable thickness-density relationship between cortical bone tissue structure density and cortical bone tissue structure thickness; b) providing measured variations of an imaging parameter of said clinical low resolution imaging data defining at least one representation of a region of bone tissue of a patient including said cortical bone tissue structure of interest, said variations being measured along a line crossing said cortical bone tissue structure of interest and being representative of variations of bone tissue structure density; c) modelling said variations of said imaging parameter along said line as a function having at least one parameter defining said thickness of said cortical bone tissue structure of interest along said line, at least a first density parameter defining said density of said cortical bone tissue structure of interest along said line and at least one parameter representing the blur of said imaging data; and d) fitting said function to said measured variations of said imaging parameter, wherein said fitting comprises searching for optimal values for said at least one parameter representing the blur of the said imaging data, for said at least one parameter defining said thickness of said cortical bone tissue structure of interest and for said at least first density parameter defining said density of said cortical bone tissue structure of interest, while ensuring said at least first density parameter and said at least one parameter defining said thickness to substantially follow said variable thickness-density relationship; wherein said optimal values for said at least one parameter defining said thickness of said cortical bone tissue structure of interest and for said at least first density parameter comprise, respectively, data defining said estimate of said thickness and data defining said estimate of said density of the cortical bone tissue structure of interest; characterised in that the method comprises determining, at step a), said variable thickness-density relationship from measured variations from multiple thickness and density measurements made on reference imaging data, which are high resolution imaging data, of a reference cortical bone tissue structure of a subject which is not said patient, wherein said multiple thickness and density measurements include thickness and density measurements made on thin cortex regions of said reference cortical bone tissue structure, wherein said thin cortex regions have thicknesses below 3 mm.