1. A method for determining bone mineral density values of an object to be examined by way of a computerized tomography system, the method comprising: acquiring first two-dimensional projection overview image data of the object to be examined in an image detail with a first X-ray energy; acquiring at least second two-dimensional projection overview image data of the object to be examined in an image detail with at least one second X-ray energy, which differs from the first X-ray energy; planning a computerized tomography (CT) examination of the object using one of the first two-dimensional projection overview image data and the second two-dimensional projection overview image data; determining a bone overview image data record using the first projection overview image data and the second projection overview image data; determining at least one specific evaluation region of the image detail using the bone overview image data record; and determining a bone mineral density value for the specific evaluation region of the image detail using the image data of the bone overview image data record in the specific evaluation region such that one of the first two-dimensional projection overview image data and the second two-dimensional projection overview image data is simultaneously used to plan the CT examination and determine the bone mineral density value for the specific evaluation region of the image detail of the object.