Vijayan Sarath, Xiong Zhenyu, Rudin Stephen, Bednarek Daniel R
Toshiba Stroke and Vascular Research Center, University at Buffalo, Buffalo, NY 14214.
Proc SPIE Int Soc Opt Eng. 2016 Feb 27;9783. doi: 10.1117/12.2216931. Epub 2016 Mar 29.
The skin-dose tracking system (DTS) provides a color-coded illustration of the cumulative skin-dose distribution on a closely-matching 3D graphic of the patient during fluoroscopic interventions in real-time for immediate feedback to the interventionist. The skin-dose tracking utility of DTS has been extended to include cone-beam computed tomography (CBCT) of neurointerventions. While the DTS was developed to track the entrance skin dose including backscatter, a significant part of the dose in CBCT is contributed by exit primary radiation and scatter due to the many overlapping projections during the rotational scan. The variation of backscatter inside and outside the collimated beam was measured with radiochromic film and a curve was fit to obtain a scatter spread function that could be applied in the DTS. Likewise, the exit dose distribution was measured with radiochromic film for a single projection and a correction factor was determined as a function of path length through the head. Both of these sources of skin dose are added for every projection in the CBCT scan to obtain a total dose mapping over the patient graphic. Results show the backscatter to follow a sigmoidal falloff near the edge of the beam, extending outside the beam as far as 8 cm. The exit dose measured for a cylindrical CTDI phantom was nearly 10 % of the entrance peak skin dose for the central ray. The dose mapping performed by the DTS for a CBCT scan was compared to that measured with radiochromic film and a CTDI-head phantom with good agreement.
皮肤剂量跟踪系统（DTS）在实时荧光透视干预过程中，在与患者紧密匹配的3D图形上提供累积皮肤剂量分布的彩色编码图示，以便立即向干预人员提供反馈。DTS的皮肤剂量跟踪功能已扩展到包括神经介入的锥形束计算机断层扫描（CBCT）。虽然DTS是为跟踪包括反向散射在内的入射皮肤剂量而开发的，但由于旋转扫描期间存在许多重叠投影，CBCT中的很大一部分剂量是由出射的原发射线和散射造成的。使用放射变色胶片测量准直束内外反向散射的变化，并拟合曲线以获得可应用于DTS中的散射扩展函数。同样，使用放射变色胶片测量单个投影的出射剂量分布，并确定作为穿过头部路径长度函数的校正因子。在CBCT扫描的每个投影中都将这两种皮肤剂量来源相加，以获得患者图形上的总剂量映射。结果显示，反向散射在束边缘附近呈S形衰减，在束外延伸至8 cm。对于圆柱形CTDI体模测量的出射剂量接近中心射线入射峰值皮肤剂量的10%。将DTS对CBCT扫描执行的剂量映射与使用放射变色胶片和CTDI头部体模测量的结果进行比较，结果吻合良好。
