# Comparing the Diagnostic Accuracy of CBCT
## 4 Discussion  
This inquiry demonstrated that positive relationships did exist between the measured CBCT HU values and DXA scores among osteoporotic and normal dental implant participants. In addition, CBCT HU values were related to the existence of osteoporosis and were able to predict osteoporosis. Therefore, the null hypothesis was rejected. In this study, a digital 3D CBCT machine was used to calculate bone mineral density. It has nine fields of views (FOV) and various low-doses settings that offer great flexibility when choosing the exposure mode. Moreover, it has a wide range of sizes that allow choosing based on true clinical needs. [PERSON] reported that the radiation dose decreased after decreasing the FOV, but the relation was not linear [39]. During this investigation, the acquisitions were made with medium FOV (\(10\times 14\) mm), in order to reduce the radiation dose. The diagnostic accuracy of this CBCT machine has been confirmed previously [40]. The DXA machine used to assess osteoporosis for the purpose of this study was a central DXA device, as it is more sensitive and better standardized than peripheral ones [41]. In addition, it has controlled dose methods to minimize scatter radiation. This ensures that only the exposed parts are imaged, while other parts of the body receive minimal radiation. Few studies have been conducted to evaluate the efficacy of CBCT in measuring bone density and to correlate it with DXA values [11; 13; 17; 42; 43; 44]. To the authors' knowledge, this is the first study that correlated the CBCT Hounsfield number to DXA T scores at different regions, in both the mandible and the maxilla. In the present study, GS values at the posterior maxilla were able to predict the presence of osteoporosis. This might be explained by the thin cortical bone and greater volume of cancellous bone in comparison to the mandible. Therefore, it is affected more by hormonal changes in osteoporotic conditions, as it has a richer blood supply [11]. This is in accordance with the findings of [PERSON] et al., who concluded that the voxel values of mandibular trabecular bone obtained from CBCT could be used for BMD estimation [26]. Similarly, [PERSON] et al. suggested that the bone density measurement of the mandible with CBCT can predict subjects with osteoporosis [20]. However, they did not use GS values to predict osteoporosis during their investigations, and they studied the mandible, not the maxilla [21]. Other researches also indicated that osteoporosis could be predicted with high accuracy from the radiographic density value of the mandibular body performed by CBCT [21]. The outcomes of the present study showed that GS values at the posterior maxilla and anterior mandible were able to predict T value. This is in agreement with previous investigations that used different methods and different research settings in this regard [45]. [PERSON] et al. compared the BMD values obtained by CBCT and DXA, and found a positive correlation between the two modalities [45]. Moreover, [PERSON] et al. used the fractal dimension (FD) and radio-morphometric indices of jawbone CBCT images and correlated them with BMD accessed via DXA [46]. They observed high correlations between the radio-morphometric indices and BMD values. In addition, [PERSON] et al. compared CBCT and DXA to evaluate the bone strength of the cortical bone of rats' femur and tibia bones. Their observations suggested that CBCT could provide better fracture load predictions than DXA [47]. In contrast, other researchers reported no correlation between the BMD obtained from DXA and the CBCT for the mandible [48]. This could be attributed to utilizing different CBCT