Niroomand-Rad A, Razavi R, Thobejane S, Harter K W
Department of Radiation Medicine, Georgetown University Medical Center, Washington, DC 20007, USA.
Int J Radiat Oncol Biol Phys. 1996 Jan 15;34(2):475-80. doi: 10.1016/0360-3016(95)02095-0.
To determine the dose perturbation effects at the tissue-metal implant interfaces in head and neck cancer patients treated with 6 MV and 10 MV photon beams.
Phantom measurements were performed to investigate the magnitude of dose perturbation to the tissue adjacent to the titanium alloy implants with (100 mu and 500 mu thick) and without hydroxylapatite (HA) coating. Radiographic and radiochromic films were placed at the upper (and lower) surface of circular metal discs (diameter x thickness: 15 x 3.2, 48 x 3.2, 48 x 3.8 mm2) in a solid water phantom and were exposed perpendicular to radiation beams. The dosimeters were scanned with automatic film scanners. Using a thin-window parallel-plate ion chamber, dose perturbation were measured for a 48 x 3.2 mm2 disc.
At the upper surface of the tissue-dental implant interface, the radiographic data indicate that for 15 x 3.2 mm2 uncoated, as well as 100 mu coated discs, dose perturbation is about +22.5% and +20.0% using 6 MV and 10 MV photon beams, respectively. For 48 x 3.2 mm2 discs, these values basically remain the same. However, for 48 x 3.8 mm2 discs, these values increase slightly to about +23.0% and +20.5% for 6 MV and 10 MV beams, respectively. For 48 x 3.2 mm2 discs with 500 mu coating, dose enhancement is slightly lower than that obtained for uncoated and 100 mu coated discs for each beam energy studied. At the lower interface for 15 x 3.2 mm2 and 48 x 3.2 mm2 uncoated and 100 mu coated discs, dose reduction is similar and is about -13.5% and -9.5% for 6 MV and 10 MV beams, respectively. For 48 x 3.8 mm2 discs, dose reduction is about -14.5% and -10.0% for 6 MV and 10 MV beams, respectively. For 48 x 3.2 mm2 discs with 500 mu coating, the dose reduction were slightly higher than those for uncoated and 100 mu coated discs.
For the beam energies studied, dose enhancement is slightly larger for the lower energy beam. The results of dose perturbation were similar for 100 mu coated and uncoated discs. These results were slightly lower for the 500 mu coated discs but are not clinically significant. The dosimetry results obtained from radiochromic films were similar to the ones obtained from radiographic film. The dose enhancement results obtained from ion chamber dosimetry are higher than those obtained from film dosimetry. The ion chamber data represent the data at "true" tissue-titanium interface, whereas the ones obtained from film dosimetry represent the data at film-titanium interface.
确定接受6兆伏和10兆伏光子束治疗的头颈癌患者组织-金属植入物界面处的剂量扰动效应。
进行模体测量，以研究与有（100微米和500微米厚）和无羟基磷灰石（HA）涂层的钛合金植入物相邻组织的剂量扰动幅度。将射线照相胶片和放射变色胶片放置在固体水模体中圆形金属盘（直径×厚度：15×3.2、48×3.2、48×3.8平方毫米）的上（和下）表面，并垂直于辐射束进行照射。使用自动胶片扫描仪对剂量计进行扫描。使用薄窗平行板电离室，对一个48×3.2平方毫米的圆盘测量剂量扰动。
在组织-牙植入物界面的上表面，射线照相数据表明，对于15×3.2平方毫米未涂层以及100微米涂层的圆盘，使用6兆伏和10兆伏光子束时，剂量扰动分别约为+22.5%和+20.0%。对于48×3.2平方毫米的圆盘，这些值基本保持不变。然而，对于48×3.8平方毫米的圆盘，对于6兆伏和10兆伏束，这些值分别略微增加到约+23.0%和+20.5%。对于研究的每种束能量，对于有500微米涂层的48×3.2平方毫米圆盘，剂量增强略低于未涂层和100微米涂层圆盘。在15×3.2平方毫米和48×3.2平方毫米未涂层和100微米涂层圆盘的下界面，剂量降低相似，对于6兆伏和10兆伏束分别约为-13.5%和-9.5%。对于48×3.8平方毫米的圆盘，对于6兆伏和10兆伏束，剂量降低分别约为-14.5%和-10.0%。对于有500微米涂层的48×3.2平方毫米圆盘，剂量降低略高于未涂层和100微米涂层圆盘。
对于所研究的束能量，较低能量束的剂量增强略大。100微米涂层和未涂层圆盘的剂量扰动结果相似。对于500微米涂层圆盘，这些结果略低，但在临床上不显著。从放射变色胶片获得的剂量测定结果与从射线照相胶片获得的结果相似。从电离室剂量测定获得的剂量增强结果高于从胶片剂量测定获得的结果。电离室数据代表“真实”组织-钛界面处的数据，而从胶片剂量测定获得的数据代表胶片-钛界面处的数据。
