Yue N, Nath R, Hehrlein C
Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, Connecticut 06510, USA.
Cardiovasc Radiat Med. 1999 Oct-Dec;1(4):349-57. doi: 10.1016/s1522-1865(00)00022-6.
A phosphorus-32-impregnated balloon angioplasty catheter was used in a novel technique of simultaneous angioplasty and vessel irradiation. The 32P radionuclides were distributed on the surface of the balloon so that a certain amount of radiation was delivered while angioplasty was performed. Three-dimensional dosimetry and dose-time relationship needs to be established for the catheter so that quantitative dosimetric information is available for both clinical treatment and research investigation.
The 32P-impregnated balloon of an angioplasty catheter was assumed to have a cylindrical shape, and the radionuclides were assumed to be distributed uniformly on the curved surface of the cylinder. The dose rate at a point in space was computed by integrating the point dose-rate kernel of 32P over the radioactive surface of the balloon. The point dose-rate kernel was computed with Monte Carlo simulation of radiation transport. The energy spectra of 32P based on a mathematical model was used in the calculations. The three-dimensional dose distributions and dose-time relationships were calculated for balloons of various lengths and radii.
At a short radial distance (e.g., 0.2 mm) away from the balloon surface, the dose distribution was uniform across a large portion of the balloon along the longitudinal axis, and dropped off rapidly at both ends of the balloon. Uniformity became worse as the radial distance increased. Uniformity was almost independent of balloon radius. The underdosed length at each end of the balloon was also almost independent of balloon length. In the central transverse plane, the dose reached a maximum at the surface of the balloon and then dropped off rapidly as the distance increases. Relative dose coverage outside the balloon was approximately independent of balloon radius and length, and the absolute dose coverage was approximately inversely proportional to balloon radius and length, assuming same total activity.
Point dose-rate kernel of 32P beta emitter and the three-dimensional dose distributions of a 32P-impregnated balloon from an novel angioplasty catheter were calculated. A rule of thumb for dose calculation and dose coverage was established for simultaneous angioplasty and vascular brachytherapy with a 32P-impregnated balloon catheter.
一种含磷 - 32的球囊血管成形术导管被用于一种同时进行血管成形术和血管照射的新技术。32P放射性核素分布在球囊表面，以便在进行血管成形术时能传递一定量的辐射。需要为该导管建立三维剂量测定法和剂量 - 时间关系，以便为临床治疗和研究调查提供定量的剂量测定信息。
血管成形术导管的含32P球囊被假定为圆柱形，且放射性核素被假定均匀分布在圆柱的曲面上。通过在球囊的放射性表面上对32P的点剂量率核进行积分，计算空间中某一点的剂量率。点剂量率核通过辐射传输的蒙特卡罗模拟计算得出。计算中使用了基于数学模型的32P能谱。针对不同长度和半径的球囊计算了三维剂量分布和剂量 - 时间关系。
在距球囊表面较短的径向距离（例如0.2毫米）处，沿纵轴方向，球囊大部分区域的剂量分布是均匀的，并且在球囊两端迅速下降。随着径向距离增加，均匀性变差。均匀性几乎与球囊半径无关。球囊两端的剂量不足长度也几乎与球囊长度无关。在中央横向平面中，剂量在球囊表面达到最大值，然后随着距离增加迅速下降。假设总活度相同，球囊外的相对剂量覆盖范围大致与球囊半径和长度无关，而绝对剂量覆盖范围大致与球囊半径和长度成反比。
计算了32Pβ发射体的点剂量率核以及新型血管成形术导管含32P球囊的三维剂量分布。为使用含32P球囊导管同时进行血管成形术和血管近距离治疗建立了剂量计算和剂量覆盖的经验法则。
