Al-Qaisieh Bashar, Smith David W, Brearley Elizabeth, St Clair Shaun, Bownes Peter
Medical Physics Department, Cookridge Hospital, Leeds, UK.
Radiother Oncol. 2007 Aug;84(2):140-7. doi: 10.1016/j.radonc.2007.05.023. Epub 2007 Jun 22.
To compare the visibility of different manufacturers I-125, seeds, and to investigate the effect of differences in dosimetry on treatment planning.
Oncura Oncoseed, Oncura Echoseed, IBT Intersource, Bebig Isoseed and Nucletron Selectseed were investigated. The point dose at increasing distances from each seed type was calculated for three different angles; theta=0 degrees, 45 degrees and 90 degrees (where theta=0 degrees lies parallel to seed length). 10 patient plans were used to assess the effect of a change in dosimetry on treatment planning and quality of prostate and rectum implant indices such as Vp100, Vp200, Dp90, Vr100 and Vr69. All implant indices and dosimetry data were compared to Oncoseed. Visibility under X-ray, fluoroscopy, CT and MRI was investigated using prostate phantoms created in-house. Statistical significance was calculated using paired two-tailed t-tests.
Dosimetric analysis was carried out for seeds of the same source strength. Differences in dose increase closer to the centre of each source, with the largest changes occurring for the angle theta=0 degrees. Selectseed and Isoseed seed types provide a consistently lower dose in all three directions. Changes to Vp100 are small and statistically insignificant for all seeds except Selectseed which shows a statistically significant decrease of 0.04% (p=0.02). Changes to Vp150 and Vp200 are statistically significant (p<0.01), with Intersource showing the greatest increase in both values. Selectseed shows a decrease in both Vp150 and Vp200. Echoseed shows an increase in both Vp150 and Vp200. Changes to D90 are statistically significant (p<0.01), with Intersource showing the greatest increase, followed by Isoseed then Echoseed. Selectseed shows a decrease in D90. For Vr100 there is no statistically significant change for any seed type. However, all seeds except Selectseed show a statistically significant increase in the value of Vr69, with Intersource showing the greatest increase. On fluoroscopy and X-ray images, Intersource seeds appear least visible, Echoseed and Oncoseed are similar, and Isoseed and Selectseed are most visible. Ultrasound greyscale beam profiles show that all seed images have a FWHM larger than the Oncoseed image. The CT greyscale beam profiles are similar for all seed images. The MRI signal voids are similar for all seed images except Intersource which shows a larger signal void.
The greatest changes to point dose occur at very close distances to the seeds. Changing seed type may require a treatment replan to maintain satisfactory DVH criteria. Visibility on US and CT is similar, though it may vary on MRI, X-ray and fluoroscopy.
比较不同制造商的I-125种子源的可视性，并研究剂量学差异对治疗计划的影响。
对Oncura Oncoseed、Oncura Echoseed、IBT Intersource、Bebig Isoseed和Nucletron Selectseed进行了研究。针对三种不同角度（θ=0度、45度和90度，其中θ=0度与种子长度平行），计算了距每种种子源不同距离处的点剂量。使用10例患者计划评估剂量学变化对治疗计划以及前列腺和直肠植入指标（如Vp100、Vp200、Dp90、Vr100和Vr69）质量的影响。将所有植入指标和剂量学数据与Oncoseed进行比较。使用内部制作的前列腺模体研究了X射线、荧光透视、CT和MRI下的可视性。采用配对双尾t检验计算统计学显著性。
对相同源强度的种子进行了剂量学分析。在每个源中心附近剂量增加存在差异，在θ=0度时变化最大。Selectseed和Isoseed种子类型在所有三个方向上的剂量始终较低。除Selectseed外，所有种子的Vp100变化较小且无统计学显著性，Selectseed的Vp100有统计学显著性降低0.04%（p=0.02）。Vp150和Vp200的变化具有统计学显著性（p<0.01），Intersource在这两个值上的增加最大。Selectseed的Vp150和Vp200均降低。Echoseed的Vp150和Vp200均增加。D90的变化具有统计学显著性（p<0.01），Intersource增加最大，其次是Isoseed，然后是Echoseed。Selectseed的D90降低。对于Vr100，任何种子类型均无统计学显著性变化。然而，除Selectseed外，所有种子的Vr69值均有统计学显著性增加，Intersource增加最大。在荧光透视和X射线图像上，Intersource种子看起来最不易见，Echoseed和Oncoseed相似，Isoseed和Selectseed最易见。超声灰度波束剖面显示，所有种子图像的半高宽均大于Oncoseed图像。所有种子图像的CT灰度波束剖面相似。除Intersource显示较大信号空白外，所有种子图像的MRI信号空白相似。
点剂量的最大变化发生在距种子非常近的距离处。改变种子类型可能需要重新进行治疗计划以维持满意的剂量体积直方图标准。超声和CT上的可视性相似，不过在MRI、X射线和荧光透视上可能有所不同。
