For the determining the thickness of a tissue layer based on an image recorded with an imaging process such as ultrasound imaging (11), an image describing spatial behavior of a measured quantity across at least one section through said tissue layer is recorded (13) and processed in a data processing apparatus, which calculates values of thickness for said image data. For this calculation, a plurality of section lines within the image is used, thickness value candidates for each of the section lines are determined (17), the thickness value candidates are sorted into distance classes (19), of which at least one is selected, and a value of thickness is calculated by averaging (21) the thickness value candidates within the distance class(es) selected. The individual distance values can also be used for analyses of patterns, e.g. subcutaneous fat patterning in the imaged part of the body.
