Ekestubbe A, Thilander A, Gröndahl H G
University of Goteborg, Sweden.
Dentomaxillofac Radiol. 1992 May;21(2):65-9. doi: 10.1259/dmfr.21.2.1397458.
Tomography is sometimes needed to obtain information on the amount of bone available in the maxilla and in the posterior parts of the mandible prior to implant surgery. Both conventional and computed tomography can be employed. Recently a new imaging device, the Scanora, has been introduced which can be used for spiral tomography. The aim of this study was to compare absorbed doses and energy imparted from this new unit with those from conventional hypocycloidal tomography using the Philips Universal Polytome. A multi-film cassette with five pairs of calcium tungstate screens was used in the latter while a single film technique was used with the Scanora. The absorbed dose measurements were made on an anthropomorphic phantom. Most absorbed doses were found to be below 0.2 mGy except those to the major salivary glands. The absorbed doses with the Scanora were higher than with the Polytome. The beam direction and shorter focus-object distance in the Scanora influenced the absorbed dose distribution. The energy imparted was found to be low for both techniques, 1.8-1.9 mJ with the Scanora for both jaws, and for hypocycloidal tomography 0.78 mJ in the maxilla and 1.3 mJ in the mandible.
在种植手术前，有时需要进行断层扫描以获取上颌骨和下颌骨后部可用骨量的信息。传统断层扫描和计算机断层扫描均可采用。最近，一种新型成像设备Scanora被引入，可用于螺旋断层扫描。本研究的目的是比较该新设备与使用飞利浦通用断层机的传统摆线断层扫描的吸收剂量和传递能量。后者使用带有五对钨酸钙屏的多层暗盒，而Scanora使用单张胶片技术。吸收剂量测量是在人体模型上进行的。除主要唾液腺外，大多数吸收剂量低于0.2 mGy。Scanora的吸收剂量高于通用断层机。Scanora中的束流方向和较短的焦点-物体距离影响吸收剂量分布。发现两种技术传递的能量都很低，Scanora对上颌和下颌的能量为1.8-1.9 mJ，摆线断层扫描在上颌为0.78 mJ，在下颌为1.3 mJ。
