Popowski Y, Verin V, Papirov I, Nouet P, Rouzaud M, Schwager M, Urban P, Rutishauser W, Kurtz J M
Radiation Oncology Division, University Hospital, Geneva, Switzerland.
Int J Radiat Oncol Biol Phys. 1995 Oct 15;33(3):713-7. doi: 10.1016/0360-3016(95)00259-2.
Irradiation has been shown to be effective in preventing restenosis after dilatation in human peripheral arteries. We have developed a dedicated system for coronary intraarterial irradiation using a 90Y pure beta-emitting source inside a specially modified angioplasty balloon. This paper presents a preliminary dosimetric evaluation of this system.
Specially fabricated titanium-covered and activated yttrium wires (outer diameter 0.32 mm) were used for these studies. Dosimetry was performed using small thermoluminescent dosimeters (TLDs) placed on the surface of the 2-cm long angioplasty balloons, inflated with contrast medium to a diameter of 2.5, 3, 3.5, and 4 mm. Radioactive 90Y wires were left in the inner balloon catheter and the surface dose rate was measured and extrapolated to 72 h after activation to allow a comparison between the values obtained. After observing the poor centering of the source within the standard angioplasty balloon, a new centering balloon was developed. A conventional balloon was subdivided into four evenly spaced interconnecting chambers, thus assuring adequate centering of the inner catheter. Thermoluminescent dosimetric measurements were performed with a 3.5 mm centering balloon to evaluate the homogeneity of the surface doses compared to those measured with the conventional balloon.
Thermoluminescent dosimetric measurements using the standard balloons filled with contrast medium were plotted semilogarithmically as a function of distance from the balloon surface. The logarithms of the measured doses fit a straight line as a function of depth. The doses at 1 mm and 3 mm are approximately 50 and 10% of the surface dose, respectively. Due to the poor centering of the source in the conventional balloons, the dispersion and standard deviations (SDs) of the measured surface doses increased proportionally to the balloon diameter (SDs are 1.89, 5.52, 5.79, and 6.46 Gy for 2.5, 3, 3.5, and 4 mm balloon diameters, respectively). For the 3.5 mm centering and conventional balloons the respective mean, minimum, and maximum surface doses were 8.41 Gy (min. 7.26; max. 9.46) and 7.89 Gy (min. 2.18; max. 16.06) and their standard deviations were 0.66 and 5.79 Gy, respectively.
Conventional angioplasty balloons cannot ensure a homogeneous dose delivery to an arterial wall with an intralumenal 90Y beta source. Preliminary dosimetric results using a modified centering balloon show that it permits improved surface dose distribution (axial and circumferential homogeneity), making it suitable for clinical applications.
已证明照射在预防人类外周动脉扩张后再狭窄方面是有效的。我们开发了一种专用系统，用于在经过特殊改装的血管成形术球囊内使用90Y纯β发射源进行冠状动脉内照射。本文介绍了该系统的初步剂量学评估。
这些研究使用了特殊制造的钛包覆并活化的钇丝（外径0.32毫米）。剂量学是通过将小型热释光剂量计（TLD）放置在2厘米长的血管成形术球囊表面进行的，球囊用造影剂充气至直径2.5、3、3.5和4毫米。将放射性90Y丝留在球囊内导管中，测量表面剂量率并外推至活化后72小时，以便比较所得值。在观察到标准血管成形术球囊内源的对中较差后，开发了一种新的对中球囊。将传统球囊细分为四个等间距互连的腔室，从而确保内导管有足够的对中。使用3.5毫米对中球囊进行热释光剂量测量，以评估与传统球囊测量的表面剂量相比的均匀性。
使用充满造影剂的标准球囊进行的热释光剂量测量结果以半对数形式绘制为距球囊表面距离的函数。测量剂量的对数作为深度的函数拟合一条直线。1毫米和3毫米处的剂量分别约为表面剂量的50%和10%。由于传统球囊中源的对中较差，测量的表面剂量的离散度和标准差（SD）与球囊直径成比例增加（对于直径2.5、3、3.5和4毫米的球囊，SD分别为1.89、5.52、5.79和6.46 Gy）。对于3.5毫米对中球囊和传统球囊，各自的平均、最小和最大表面剂量分别为8.41 Gy（最小7.26；最大9.46）和7.89 Gy（最小2.18；最大16.06），其标准差分别为0.66和5.79 Gy。
传统血管成形术球囊不能确保将腔内90Yβ源的剂量均匀地输送到动脉壁。使用改良对中球囊的初步剂量学结果表明，它允许改善表面剂量分布（轴向和周向均匀性），使其适用于临床应用。
