Janssen P T, van Aken J
Department of Biomaterials, ACTA, University of Amsterdam, The Netherlands.
J Clin Periodontol. 1989 May;16(5):323-30. doi: 10.1111/j.1600-051x.1989.tb01663.x.
The validity of a quantitative digital subtraction technique was investigated in vitro when influenced by the following aspects: the material enveloping the aluminium reference wedge, the radiation quality used to produce the radiographs and the effect of differences in image geometry between repeated radiographs. The test object consisted of a dry mandible in which small test objects made of aluminium with known volumes were introduced. By means of the quantitative digital subtraction technique, the aluminium volumes of these test objects were determined. The best agreement between the measured volumes and the actual volumes, was found when the aluminium reference wedge was embedded in polymethylmethacrylate and exposure conditions of 50 kVp, 15 mAs were used. An increase in the differences in image geometry between radiographs led to a decrease in the validity and accuracy of the measurements. For the in vivo application of this method, serial radiographs of 4 patients were taken to register the periodontal bone changes over a 5-8 month period. Differences in the approximal bone between radiographs were quantified in aluminium equivalent volumes (AEV's). In 23% of the measured sites, changes in the mineral content could be detected. The changed sites were found in only 2 patients. One patient showed 3 sites with remineralization, while the other patient showed 2 sites with demineralization. The differences detected ranged from -1.54 to +0.38 mm3 aluminium equivalent.
包裹铝参考楔的材料、用于生成射线照片的辐射质量以及重复射线照片之间图像几何形状差异的影响。测试对象由一个干燥的下颌骨组成，其中引入了已知体积的由铝制成的小测试对象。通过定量数字减法技术，确定了这些测试对象的铝体积。当铝参考楔嵌入聚甲基丙烯酸甲酯中并使用50 kVp、15 mAs的曝光条件时，测量体积与实际体积之间的一致性最佳。射线照片之间图像几何形状差异的增加导致测量的有效性和准确性降低。对于该方法的体内应用，拍摄了4名患者的系列射线照片，以记录5 - 8个月期间的牙周骨变化。射线照片之间邻面骨的差异以铝当量体积（AEV）进行量化。在23%的测量部位，可以检测到矿物质含量的变化。变化的部位仅在2名患者中发现。一名患者有3个部位出现再矿化，而另一名患者有2个部位出现脱矿。检测到的差异范围为-1.54至+0.38 mm³铝当量。
