Khojastepour L, Mohammadzadeh S, Jazayeri M, Omidi M
Professor of Oral and Maxillofacial Radiology (M.Sc.), Department of Radiology, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran.
Specialist in Periodontology (M.Sc.), Department of Periodontics, School of Dentistry, Bushehr University of Medical Sciences, Bushehr, Iran.
J Biomed Phys Eng. 2017 Sep 1;7(3):289-298. eCollection 2017 Sep.
Jaw bone quality plays an essential role in treatment planning and prognosis of dental implants. Regarding several available methods for bone density measurements, they are not routinely used before implant surgery due to hard accessibility.
An in vitro investigation of correlation between average gray scale in direct digital radiographs and Hounsfield units in CT-Scan provides a feasible method for evaluating alveolar bone quality prior to implant surgery.
26 sheep's mandibles in which a square shape ROI marked by gutta percha, were prepared. Three direct digital radiographs (CCD sensor) from every specimen were taken using 80, 100 and 200 milli-seconds. Then, the average gray levels for ROIs were calculated using a costume-made software. Next, the specimens were scanned using a 16-slice spiral CT and the Hounsfield Unit of each ROI was calculated. Pearson analysis measured the correlation between Hounsfield units and average gray levels.
There was a positive correlation between Hounsfield unit and average gray level in the radiographs and the correlation was better in higher exposure times.
It is possible to estimate Hounsfield unit and bone density in the jaw bones using average gray scale in a digital radiograph. This approach is easy, simple and available and also results in lower patient exposure comparing other bone densitometric analysis methods.
颌骨质量在牙种植体治疗计划和预后中起着至关重要的作用。关于几种现有的骨密度测量方法，由于难以获取，在种植手术前并未常规使用。
对直接数字化X线片的平均灰度与CT扫描中的亨氏单位之间的相关性进行体外研究，为种植手术前评估牙槽骨质量提供一种可行的方法。
准备26个用牙胶标记出方形感兴趣区（ROI）的绵羊下颌骨。使用80、100和200毫秒对每个标本拍摄三张直接数字化X线片（CCD传感器）。然后，使用定制软件计算ROI的平均灰度。接下来，使用16层螺旋CT对标本进行扫描，并计算每个ROI的亨氏单位。Pearson分析测量亨氏单位与平均灰度之间的相关性。
X线片中亨氏单位与平均灰度之间存在正相关，且在较高曝光时间下相关性更好。
利用数字化X线片中的平均灰度来估计颌骨中的亨氏单位和骨密度是可行的。这种方法简便易行且可获得，与其他骨密度分析方法相比，还能减少患者的辐射暴露。
