Response to the editor of JBMR regarding the letter related to “Opportunistic screening with CT: comparison of phantomless BMD calibration methods”

Le résumé fourni par la source

We thank Prof. Boyd and colleagues for their interesting comments highlighting the growing importance of internal bone mineral density (BMD) calibration techniques for use in opportunistic screening. We agree that the phantomless BMD calibration method developed at the University of Calgary1 is easier to use than other methods because it does not require an external reference data set. We had addressed this point in our publication2 in the first sentence of the section “Phantomless calibration method 4: Voxel-specific calibration.” It is true that at the time of writing, we were not aware of the public availability of the voxel-specific calibration method developed in Calgary. In retrospect, we have noted that a reference to the website appears to have been published only in an article focusing on muscle density calibration.3 We congratulate the authors for providing a public domain tool. We have now implemented the Calgary software as provided in the Github archive and compared the results with the software we implemented for our publication.2 There were two remaining differences between the two software. First, as pointed out in the authors’ letter, the Calgary software is based on 5 internal reference materials. Thus, for the comparison specifically performed to address this letter, we used the same set of materials in our software. Second, the Calgary software used mass absorption coefficients (MAC) to determine the effective energy, although the paper by Millner et al.4 cited by Michalski as a reference for the method to determine the effective energy suggested the use of linear absorption coefficients of the internal reference materials. Consequently, we had also used linear absorption coefficients for all calculations performed for our publication.2 However, for the purpose of comparison, we have now implemented MAC in our software. We applied both softwares to our DS1 dataset of 350 computed tomography (CT) scans from female residents of Minnesota, described in detail in our publication. The BMD accuracy errors obtained with the Calgary software were virtually identical to our software (modified for comparison as described above), as can be seen in Figure 1.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.