Comparative dose evaluations between XVI and OBI cone beam CT systems using Gafchromic XRQA2 film and nanoDot optical stimulated luminescence dosimeters
Comparative dose evaluations between XVI and OBI cone beam CT systems using Gafchromic XRQA2 film and nanoDot optical stimulated luminescence dosimeters
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DOI：
10.1118/1.4803466
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发表时间：
2013-06-01
期刊：
影响因子：
3.8
通讯作者：
Xiao, Ying
中科院分区：
文献类型：
--
作者：
Giaddui, Tawfik;Cui, Yunfeng;Xiao, Ying
目的：研究能量（kVp）和滤光片（无滤光片、半Bowtie和全Bowtie）对CBCT剂量场中Gafchromic XRQA 2薄膜和nanoDot光学受激发光剂量计（OSLD）的剂量响应曲线的影响。为了测量在X射线体积成像仪（XVI）（版本R4.5）和机载成像仪（OBI）（版本1.5）CBCT成像协议期间接收的表面和内部剂量，使用这两种类型的dosometer.Methods：Gafchromic XRQA 2胶片和nanoDot OSLD剂量响应曲线在XVI（软件版本R4.5）和OBI（软件版本1.5）CBCT系统使用的不同kV成像设置下生成。XVI系统的设置为：100 kVp/F0（无过滤器）、120 kVp/F0和120 kVp/F1（Bowtie过滤器），OBI系统的设置为：100 kVp/全风扇、125 kVp/全风扇和125 kVp/半风扇。XRQA 2胶片在0和11 cGy之间的空气-空气比释动能水平中校准，并使用反射扫描模式用Epson Expression 10000 XL平板文档扫描仪扫描。在体模上将NanoDot OSLD校准到0至14 cGy之间的表面剂量水平，并使用inLight（TM）MicroStar读取器读取。两种剂量计被用来测量在现场表面和内部剂量在男性Alderson Rando Phantom.Results：剂量响应曲线的XRQA 2薄膜和nanoDot OSLD在不同的XVI和OBI CBCT设置的报告。对于XVI系统，表面剂量范围在快速头颈扫描期间头部区域的0.02 cGy和对称扫描期间胸部区域的4.99 cGy之间。另一方面，内部剂量范围在快速头颈部扫描期间头部区域的0.02 cGy和胸部M20扫描期间胸部区域的3.17 cGy之间。平均（内部和外部）剂量范围为快速头颈部扫描期间头部区域的0.05 cGy和胸部M20扫描期间胸部区域的2.41 cGy。对于OBI系统，头部扫描期间头部区域的表面剂量范围为0.19 cGy，聚光灯扫描期间骨盆区域的表面剂量范围为4.55 cGy。然而，内部剂量范围在头部扫描期间头部区域中的0.47 cGy和聚光灯扫描期间骨盆区域中的5.55 cGy之间。平均（内部和外部）剂量范围为头部扫描期间头部区域的0.45 cGy和聚光灯扫描期间骨盆区域的3.59 cGy。Gafchromic XRQA 2胶片和nanoDot OSLD在许多情况下都能对剂量进行接近的估计（在不确定性范围内）。结论：Gafchromic XRQA 2胶片和nanoDot OSLD的剂量响应曲线表明，即使在相同的光子能量下，使用不同的滤光片，这两种剂量计的剂量响应也是不同的。两个剂量测定系统的不确定性水平均低于6%，剂量超过1 cGy。在许多情况下，两种剂量测定系统给出的剂量估计几乎相似（在不确定性范围内），但在某些情况下，差异约为20%-30%。新版本的CBCT系统（在本研究中进行了研究）导致成像剂量低于先前研究中早期版本报告的剂量。(c)2013年美国医学物理学家协会。
Purpose: To investigate the effect of energy (kVp) and filters (no filter, half Bowtie, and full Bowtie) on the dose response curves of the Gafchromic XRQA2 film and nanoDot optical stimulated luminescence dosimeters (OSLDs) in CBCT dose fields. To measure surface and internal doses received during x-ray volume imager (XVI) (Version R4.5) and on board imager (OBI) (Version 1.5) CBCT imaging protocols using these two types of dosimeters.Methods: Gafchromic XRQA2 film and nanoDot OSLD dose response curves were generated at different kV imaging settings used by XVI (software version R4.5) and OBI (software version 1.5) CBCT systems. The settings for the XVI system were: 100 kVp/F0 (no filter), 120 kVp/F0, and 120 kVp/F1 (Bowtie filter), and for the OBI system were: 100 kVp/full fan, 125 kVp/full fan, and 125 kVp/half fan. XRQA2 film was calibrated in air to air kerma levels between 0 and 11 cGy and scanned using reflection scanning mode with the Epson Expression 10000 XL flat-bed document scanner. NanoDot OSLDs were calibrated on phantom to surface dose levels between 0 and 14 cGy and read using the inLight (TM) MicroStar reader. Both dosimeters were used to measure in field surface and internal doses in a male Alderson Rando Phantom.Results: Dose response curves of XRQA2 film and nanoDot OSLDs at different XVI and OBI CBCT settings were reported. For XVI system, the surface dose ranged between 0.02 cGy in head region during fast head and neck scan and 4.99 cGy in the chest region during symmetry scan. On the other hand, the internal dose ranged between 0.02 cGy in the head region during fast head and neck scan and 3.17 cGy in the chest region during chest M20 scan. The average (internal and external) dose ranged between 0.05 cGy in the head region during fast head and neck scan and 2.41 cGy in the chest region during chest M20 scan. For OBI system, the surface dose ranged between 0.19 cGy in head region during head scan and 4.55 cGy in the pelvis region during spot light scan. However, the internal dose ranged between 0.47 cGy in the head region during head scan and 5.55 cGy in the pelvis region during spot light scan. The average (internal and external) dose ranged between 0.45 cGy in the head region during head scan and 3.59 cGy in the pelvis region during spot light scan. Both Gafchromic XRQA2 film and nanoDot OSLDs gave close estimation of dose (within uncertainties) in many cases. Though, discrepancies of up to 20%-30% were observed in some cases.Conclusions: Dose response curves of Gafchromic XRQA2 film and nanoDot OSLDs indicated that the dose responses of these two dosimeters were different even at the same photon energy when different filters were used. Uncertainty levels of both dosimetry systems were below 6% at doses above 1 cGy. Both dosimetry systems gave almost similar estimation of doses (within uncertainties) in many cases, with exceptions of some cases when the discrepancy was around 20%-30%. New versions of the CBCT systems (investigated in this study) resulted in lower imaging doses compared with doses reported on earlier versions in previous studies. (c) 2013 American Association of Physicists in Medicine.