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首页> 外文期刊>Physics in medicine and biology. >Determination of the dose characteristics in the near area of a new type of ~(192)Ir-HDR afterloading source with a PinPoint ionization chamber
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Determination of the dose characteristics in the near area of a new type of ~(192)Ir-HDR afterloading source with a PinPoint ionization chamber

机译：确定具有PinPoint电离室的新型〜（192）Ir-HDR后装源附近区域的剂量特性

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摘要

Since the company MDS Nordion Haan GmbH introduced the new afterloading radiation unit GammaMed plus~(TM) in 1998, new HDR Ir-192 sources with a diameter of 0.9 mm (formerly 1.1 mm) and a length of 4.5 mm (formerly 5.5 mm) have been used. With this equipment it is possible to treat peripheral vessels for prophylaxis of restenosis after percutaneous transluminal angioplasty (PTA). In this case a good knowledge of the dose characteristics in the near area is the prerequisite for safe application. In this study, the dose characteristics for this source type is investigated at close range by means of an ionization chamber. For the description of the dose characteristics, the radial dose distribution and the anisotropy function are used. The measurements were carried out using an ionization chamber, the so called PinPoint chamber (Type PTW 31006, PTW Freiburg, Germany). The radial dose distribution was examined in the area of 0.26 to 12 cm. The anisotropy function was examined in the range from 0.5 to 5 cm (distance from the effective site of measurement to the source axis). The radial dose function was compared with the correction function k_(as,w)(r), published in the German standard DIN 6809 part 2 (1991 Beuth Verlag, Berlin, Germany). In the area up to 4 cm (distance source-axis to measuring point) the deviation maximized up to 2%. The deviation climbs with greater distance from the source with results around 3%. The anisotropy function was compared with that used in the treatment planning system Abacus 3.0~(TM) of the same manufacturer. In the close range between 0.5 and 1 cm, there were some major variations (up to 10%) from the anisotropy function used in the planning system. The fault reduces itself with greater distance to under 2%. In view of the results presented in this paper further measurements of the anisotropy function in the close range from 0 to 1.5 cm from the source axis should be made. It can be seen that the function used in the planning system supplies results that are too high in comparison with the results of other authors. This concerns primarily the area of very small and very big angles.
机译：自MDS Nordion Haan GmbH公司于1998年推出新的后装辐射装置GammaMed plus〜（TM）以来，新的HDR Ir-192辐射源的直径为0.9毫米（以前为1.1毫米），长度为4.5毫米（以前为5.5毫米）被用过。使用该设备可以治疗经皮腔内血管成形术（PTA）后预防再狭窄的周围血管。在这种情况下，对附近区域剂量特性的充分了解是安全应用的前提。在这项研究中，通过电离室在近距离下研究了这种源类型的剂量特性。为了描述剂量特性，使用了径向剂量分布和各向异性函数。使用电离室，即所谓的PinPoint室（PTW 31006型，德国弗赖堡PTW）进行测量。在0.26至12 cm的区域内检查径向剂量分布。在0.5到5 cm（从有效测量位置到源轴的距离）范围内检查各向异性函数。将径向剂量函数与修正函数k_（as，w）（r）进行比较，该修正函数已发布在德国标准DIN 6809第2部分（1991年，德国柏林，Beuth Verlag）中。在最大4 cm的区域（源到测量点的距离）中，偏差最大为2％。偏离源的距离越远，偏差就越大，结果大约为3％。将各向异性函数与同一制造商的治疗计划系统Abacus 3.0〜（TM）中使用的函数进行了比较。在0.5到1厘米之间的近距离范围内，规划系统中使用的各向异性函数存在一些主要变化（最高10％）。故障将自身减小到2％以下。鉴于本文提出的结果，应在距源轴0至1.5 cm的近距离内对各向异性函数进行进一步测量。可以看出，计划系统中使用的功能所提供的结果与其他作者的结果相比过高。这主要涉及非常小和非常大的角度的区域。

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