Initial evaluation of a commercial EPID modified to a novel direct-detection configuration for radiotherapy dosimetry.
Initial evaluation of a commercial EPID modified to a novel direct-detection configuration for radiotherapy dosimetry.
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对商业 EPID 的初步评估修改为用于放射治疗剂量测定的新型直接检测配置。
DOI：
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发表时间：
2008
期刊：
影响因子：
--
通讯作者：
C. Baldock
中科院分区：
文献类型：
--
作者：
P. Vial;P. Greer;L. Oliver;C. Baldock
与医用直线加速器集成的电子门户成像设备(EPID)利用间接检测EPID配置(ID-EPID)。非晶硅ID-EPID为放射治疗的验证提供了高质量的低剂量图像，但它们在剂量计方面存在局限性。标准ID-EPID配置包括高原子序数荧光粉闪烁体屏幕、1 mm铜层和覆盖探测器的其他非水等效材料。这种配置导致ID-EPID的响应与标准放射治疗剂量计(如水中的电离室)相比有显著差异。在这项研究中，从标准的商用EPID中去除了磷和铜，将其结构修改为直接检测EPID(DD-EPID)。使用固体水作为探测器的积聚和背向散射，在DD-EPID上进行剂量测量，并与6和18 mV光子的标准水中剂量数据进行比较。DD-EPID的灵敏度约为ID-EPID的八分之一，但该信号足以为开放光束和强度调制光束产生准确和可重现的光束轮廓测量。由于较低的信号电平，发现有必要确保暗场校正(无辐射)DD-EPID信号稳定或频繁更新。剂量反应的线性与ID-EPID相当，但在低剂量时有更大的欠反应。DD-EPID测量野大小输出因子和最大剂量(DMAX)深度处的束流分布，以及0.5到10厘米深度之间的组织最大比率，与水中剂量测量非常一致。在DMAX以外的深度，DD-EPID显示出比电离室测量更大的对场大小的响应变化，并且与二极管扫描相比，束流半影更宽。本文研究的改进的DD-EPID结构具有提高EPID用于放射治疗剂量验证的性能的潜力。
Electronic portal imaging devices (EPIDs) integrated with medical linear accelerators utilize an indirect-detection EPID configuration (ID-EPID). Amorphous silicon ID-EPIDs provide high quality low dose images for verification of radiotherapy treatments but they have limitations as dosimeters. The standard ID-EPID configuration includes a high atomic number phosphor scintillator screen, a 1 mm copper layer, and other nonwater equivalent materials covering the detector. This configuration leads to marked differences in the response of an ID-EPID compared to standard radiotherapy dosimeters such as ion chambers in water. In this study the phosphor and copper were removed from a standard commercial EPID to modify the configuration to a direct-detection EPID (DD-EPID). Using solid water as the buildup and backscatter for the detector, dosimetric measurements were performed on the DD-EPID and compared to standard dose-in-water data for 6 and 18 MV photons. The sensitivity of the DD-EPID was approximately eight times less than the ID-EPID but the signal was sufficient to produce accurate and reproducible beam profile measurements for open beams and an intensity-modulated beam. Due to the lower signal levels it was found necessary to ensure that the dark field correction (no radiation) DD-EPID signal was stable or updated frequently. The linearity of dose response was comparable to the ID-EPID but with a greater under-response at low doses. DD-EPID measurements of field size output factors and beam profiles at the depth of maximum dose (dmax), and tissue-maximum ratios between the depths of 0.5 and 10 cm, were in close agreement with dose in water measurements. At depths beyond dmax the DD-EPID showed a greater change in response to field size than ionisation chamber measurements and the beam penumbrae were broader compared to diode scans. The modified DD-EPID configuration studied here has the potential to improve the performance of EPIDs for dose verification of radiotherapy treatments.
用于 IMRT 测量的直接检测有源矩阵平板剂量计 (AMFPD) 的性能。
影响因子：
3.8
作者：
Chen,Yu;Moran,JeanM;Roberts,DonaldA;El-Mohri,Youcef;Antonuk,LarryE;Fraass,BenedickA
通讯作者：
Fraass,BenedickA
影响因子：
3.8
作者：
Zhao, W;DeCrescenzo, G;Rowlands, JA
通讯作者：
Rowlands, JA