Polymer gels are three-dimensional dosimetric tools. The purpose of the present study was to investigate the temperature dependence of polymer gels during scanning Magnetic Resonance Imaging. Prepared gels were irradi...Polymer gels are three-dimensional dosimetric tools. The purpose of the present study was to investigate the temperature dependence of polymer gels during scanning Magnetic Resonance Imaging. Prepared gels were irradiated with a 6MV X-ray beam at intensities ranging from 0 to 20 Gy in order to investigate their dose-R2 and dose-R1 responses. Irradiated gels were evaluated from 1.5-T magnetic resonance R2 and R1 images for each 5°C change in temperature from 5°C to 41°C, and then the four-field box technique irradiation plan was used to deliver a total dose of 4 Gy using the same beam weight in each direction to the prepared gels. The profile of the dose map generated from the four-field irradiated gel data at 20°C was then compared with the planned data. The dose-R2 response curve was linear up to 20 Gy at 20°C, with a slope of 1.17 Gy-1˙s-1. The slopes of the fitted curves of the dose-R2 decreased as gel temperature increased. The slopes of the dose-R1 curves were more parallel than the slopes of the dose-R2 curves between 5 and 41°C. The difference in the full width of half maximum of the gel profile data obtained using the four-field box technique at 20°C and the planned data were below 5% on average. The dose map from the irradiated gels obtained using the dose-R2 curve was the same as that from the planned data under the same temperature conditions. Measurement of difference between various temperatures is significant with dose accuracy. It is suitable to evaluate the gel dosimeter under the thermal equilibrium condition, MRI room temperature from the point of view of the stability of the irradiated gels.展开更多
目的探讨采用病理学与核磁共振扫描(MRI)的图像,计算晚期酒精性股骨头坏死(osteonecrosis of the femoral head,ONFH)表面积及坏死面积占整个股骨头表面积的百分比(简称坏死表面积比),进行定量分析,并应用于临床对股骨头坏死程度的分析...目的探讨采用病理学与核磁共振扫描(MRI)的图像,计算晚期酒精性股骨头坏死(osteonecrosis of the femoral head,ONFH)表面积及坏死面积占整个股骨头表面积的百分比(简称坏死表面积比),进行定量分析,并应用于临床对股骨头坏死程度的分析。方法对9例12髋拟行关节置换的ONFH,术前作标准的MRI扫描,依T1连续图像计算,得出坏死表面积及坏死表面积比。将手术标本锯成与MRI扫描相同的层厚和层数,应用坐标纸粘贴,图像分析仪测出数据,并作统计学分析。结果 MRI图像法与标本测量的数据差异有统计学意义(P>0.05),MRI图像不能准确说明晚期酒精性股骨头缺血性坏死的程度,MRI显示的坏死程度低于病理结果。结论 MRI图像法计算股骨头坏死表面积及坏死表面积比小于病理结果。展开更多
文摘Polymer gels are three-dimensional dosimetric tools. The purpose of the present study was to investigate the temperature dependence of polymer gels during scanning Magnetic Resonance Imaging. Prepared gels were irradiated with a 6MV X-ray beam at intensities ranging from 0 to 20 Gy in order to investigate their dose-R2 and dose-R1 responses. Irradiated gels were evaluated from 1.5-T magnetic resonance R2 and R1 images for each 5°C change in temperature from 5°C to 41°C, and then the four-field box technique irradiation plan was used to deliver a total dose of 4 Gy using the same beam weight in each direction to the prepared gels. The profile of the dose map generated from the four-field irradiated gel data at 20°C was then compared with the planned data. The dose-R2 response curve was linear up to 20 Gy at 20°C, with a slope of 1.17 Gy-1˙s-1. The slopes of the fitted curves of the dose-R2 decreased as gel temperature increased. The slopes of the dose-R1 curves were more parallel than the slopes of the dose-R2 curves between 5 and 41°C. The difference in the full width of half maximum of the gel profile data obtained using the four-field box technique at 20°C and the planned data were below 5% on average. The dose map from the irradiated gels obtained using the dose-R2 curve was the same as that from the planned data under the same temperature conditions. Measurement of difference between various temperatures is significant with dose accuracy. It is suitable to evaluate the gel dosimeter under the thermal equilibrium condition, MRI room temperature from the point of view of the stability of the irradiated gels.
文摘目的探讨采用病理学与核磁共振扫描(MRI)的图像,计算晚期酒精性股骨头坏死(osteonecrosis of the femoral head,ONFH)表面积及坏死面积占整个股骨头表面积的百分比(简称坏死表面积比),进行定量分析,并应用于临床对股骨头坏死程度的分析。方法对9例12髋拟行关节置换的ONFH,术前作标准的MRI扫描,依T1连续图像计算,得出坏死表面积及坏死表面积比。将手术标本锯成与MRI扫描相同的层厚和层数,应用坐标纸粘贴,图像分析仪测出数据,并作统计学分析。结果 MRI图像法与标本测量的数据差异有统计学意义(P>0.05),MRI图像不能准确说明晚期酒精性股骨头缺血性坏死的程度,MRI显示的坏死程度低于病理结果。结论 MRI图像法计算股骨头坏死表面积及坏死表面积比小于病理结果。
