Duggan D M, Coffey C W, Lobdell J L, Schell M C
Center for Radiation Oncology, The Vanderbilt Clinic, Vanderbilt University Medical Center, Nashville, Tennessee 37232-5671, USA.
Med Phys. 1999 Nov;26(11):2461-4. doi: 10.1118/1.598814.
Good clinical physics practice requires that dose rates of brachytherapy sources be checked by the institution using them, as recommended by American Association of Physicists in Medicine Task Group 56 and The American College of Radiology. For intravascular brachytherapy with catheter-based systems, AAPM Task Group 60 recommends that the dose rate be measured at a reference point located at a radial distance of 2 mm from the center of the catheter axis. AAPM Task Group 60 also recommends that the dose rate along the catheter axis at a radial distance of 2 mm should be uniform to within +/- 10% in the center two-thirds of the treated length, and the relative dose rate in the plane perpendicular to the catheter axis through the center of the source should be measured at distances from 0.5 mm to R90 (the distance from a point source within which 90% of the energy is deposited) at intervals of 0.5 mm. Radiochromic film dosimetry has been used to measure the dose distribution in a plane parallel to and at a radial distance of 2 mm from the axis of a novel, catheter-based, beta source for intravascular brachytherapy. The dose rate was averaged along a line parallel to the catheter axis at a radial distance of 2 mm, in the centered 24.5 mm of the treated length. This average dose rate agreed with the dose rate measured with a well ionization chamber by the replacement method using source trains calibrated with an extrapolation chamber at the National Institute of Standards and Technology. All of the dose rates in the centered 24.5 mm of a line parallel to the axis at a distance of 2 mm were within +/-10% of the average.
良好的临床物理实践要求，正如美国医学物理学家协会任务组56和美国放射学会所建议的那样，使用近距离放射治疗源的机构应对其剂量率进行检查。对于基于导管系统的血管内近距离放射治疗，美国医学物理学家协会任务组60建议在距离导管轴中心径向距离2毫米处的参考点测量剂量率。美国医学物理学家协会任务组60还建议，在治疗长度的中心三分之二范围内，沿导管轴在径向距离2毫米处的剂量率应均匀在±10%以内，并且应在从0.5毫米到R90（90%能量沉积在其中的点源距离）的距离处，以0.5毫米的间隔测量垂直于导管轴并通过源中心的平面内的相对剂量率。放射变色薄膜剂量测定法已用于测量与一种新型基于导管的血管内近距离放射治疗β源的轴平行且径向距离为2毫米的平面内的剂量分布。剂量率是在治疗长度中心24.5毫米内，沿与导管轴平行且径向距离为2毫米的一条线进行平均的。该平均剂量率与使用国家标准与技术研究院用外推电离室校准的源串通过替代法用良好电离室测量的剂量率一致。在与轴平行且距离为2毫米的一条线的中心24.5毫米内的所有剂量率均在平均值的±10%以内。
