Popowski Y, Verin V, Schwager M, Nouet P, Papirov I, Rouzaud M, Urban P, Landis J R, Rutishauser W, Kurtz J M
Radiation Oncology Division, University Hospital, Geneva, Switzerland.
Int J Radiat Oncol Biol Phys. 1996 Nov 1;36(4):923-31. doi: 10.1016/s0360-3016(96)00409-9.
A dosimetric evaluation of a new device dedicated to intravascular irradiation, associating a beta source and a centering device, was carried out before initiation of a clinical pilot study.
A 29-mm-long 90Y coil, coated with titanium and fixed to the end of a thrust wire, was introduced into the inner lumen of purpose-built centering balloons of different diameters (2.5, 3, 3.5, and 4 mm). Dose homogeneity was evaluated by studying both axial and circumferential dose variations, based on readings from thermoluminescent dosimeters (TLDs) placed on the balloon surface. Axial homogeneity was determined by comparing the readout values of dosimeters located on peripheral balloon segments with those located on segments adjacent to the midpoint of the source. The centering ability of the device was studied by comparing measurements on opposing surfaces of the balloon. The dose attenuation by water and contrast medium was evaluated and compared with that in air. The balloon contamination was studied using a contamination counter. The total 90Y coil activity was measured by liquid scintillation to relate activity to surface dose.
Activity-surface dose correlation showed that for a linear coil activity of 1 mCi/mm, the mean dose rate at the surface of a 2.5-mm balloon filled with contrast medium was 8.29 Gy/min. The doses at the surface of larger balloons (3, 3.5, and 4 mm) filled with contrast were 78%, 59%, and 47%, respectively, of the dose measured at the surface of the 2.5-mm balloon. The coefficient of variation (CV) in surface dose for 2.5-, 3-, 3.5-, and 4-mm centering devices filled with contrast medium were 9%, 8%, 9%, and 12%, respectively. There was no statistically significant difference between readouts from central and peripheral balloon segments or among rows of dosimeters facing each other. For a 2.5-mm balloon, compared with air the dose attenuation by water and contrast medium was similar (0.70 and 0.69, respectively), but a significant difference was seen between the readouts of water- and contrast-filled balloons when the diameter was larger than 3 mm (p < 0.001). No contamination was found in the balloon shaft after source retrieval.
The dosimetric tests showed very good surface dose homogeneity, demonstrating satisfactory centering of the source within the centering balloons. The achievable dose rates will permit intravascular irradiation within a short time interval. The absence of residual balloon contamination after source retrieval meets the requirements for a sealed source used in a clinical setting.
在一项临床前期研究启动之前，对一种新型血管内照射设备进行了剂量学评估，该设备结合了一个β源和一个定心装置。
将一个29毫米长、涂有钛并固定在推进丝末端的90Y线圈，插入不同直径（2.5、3、3.5和4毫米）的特制定心球囊的内腔中。基于放置在球囊表面的热释光剂量计（TLD）的读数，通过研究轴向和周向剂量变化来评估剂量均匀性。通过比较位于球囊外周段的剂量计与位于源中点相邻段的剂量计的读数，确定轴向均匀性。通过比较球囊相对表面的测量值来研究该装置的定心能力。评估并比较了水和造影剂的剂量衰减与空气中的剂量衰减。使用污染计数器研究球囊污染情况。通过液体闪烁法测量90Y线圈的总活度，以将活度与表面剂量相关联。
活度-表面剂量相关性表明，对于线性线圈活度为1毫居里/毫米，充满造影剂的2.5毫米球囊表面的平均剂量率为8.29戈瑞/分钟。充满造影剂的较大球囊（3、3.5和4毫米）表面的剂量分别为2.5毫米球囊表面测量剂量的78%、59%和47%。充满造影剂的2.5、3、3.5和4毫米定心装置表面剂量的变异系数（CV）分别为9%、8%、9%和12%。球囊中央段和外周段的读数之间或相对的剂量计排之间没有统计学上的显著差异。对于2.5毫米的球囊，与空气相比，水和造影剂的剂量衰减相似（分别为0.70和0.69），但当直径大于3毫米时，充满水和造影剂的球囊读数之间存在显著差异（p < 0.001）。取出源后，在球囊杆中未发现污染。
剂量学测试显示出非常好的表面剂量均匀性，表明源在定心球囊内定心良好。可实现的剂量率将允许在短时间间隔内进行血管内照射。取出源后球囊无残留污染符合临床环境中密封源的要求。
