Use of a slit camera for MTF measurements.
Use of a slit camera for MTF measurements.
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使用狭缝相机进行 MTF 测量。
DOI：
10.1118/1.598742
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发表时间：
1999
期刊：
影响因子：
3.8
通讯作者：
Waidelich,JM
中科院分区：
文献类型：
--
作者：
Bradford,CD;Peppler,WW;Waidelich,JM
对狭缝相机进行了分析，以确定其作为表征射线照相成像系统的 MTF 测量工具的实用性和局限性。商用狭缝相机对于 MTF 测量很有吸引力，因为与传统的平行钳口狭缝相比，斜角边缘显着降低了其对准灵敏度。穿过斜角边缘的辐射增加了狭缝相机的有效宽度，因此基于标称狭缝宽度的校正将在 MTF 测量中留下残余误差。在狭缝相机（10 μm 标称狭缝宽度）上进行了实验和蒙特卡罗模拟 MTF 测量，以估计其对准灵敏度，量化由于通过斜面钳口传输而产生的 MTF 误差，并提供校正因子。研究发现，在入射光束的小 HVL（~1.3 mm Al）处，狭缝相机的对准公差比平行钳口狭缝大约 12 倍，在较高 HVL（~7 mm Al）处则大 9 倍。 MTF 残余误差的大小取决于入射光谱的质量。对于具有高 kVp 和 HVL（⩾120 kVp、⩾5 mm Al HVL）的入射光谱，通过斜角边缘的传输产生的 MTF 误差在 5 个周期/毫米时高达 15%，在 10 个周期/毫米时高达 30%。通过基于入射光束的 kVp、HVL 和过滤材料假设具有有效宽度的矩形狭缝轮廓，确定了 MTF 校正因子。应用此校正因子可将误差降低至 4% 以下，最高可达 10 周期/毫米。在低光束能量和空间频率下，校正不太重要。易于对准和更高的可用性使得商用狭缝相机可用于 MTF 测量。如果应用适当的校正因子，则可以进行准确的 MTF 测量。
The slit camera was analyzed in order to establish its utility and limitations as an MTF measurement tool for characterizing radiographic imaging systems. Commercial slit cameras are attractive for MTF measurements because the beveled edges significantly reduce their alignment sensitivity as compared to the conventional parallel jaw slit. Radiation passing through the beveled edges increases the effective width of the slit camera so that a correction based on the nominal slit width would leave residual error in the MTF measurement. Experimental and Monte Carlo simulated MTF measurements were made on a slit camera (10 μm nominal slit width) in order to estimate its sensitivity in alignment, quantify the error in MTF due to transmission through the beveled jaws, and provide a correction factor. The alignment tolerances of the slit camera were found to be about 12 times larger than for the parallel jaw slit at small HVLs (∼1.3 mm Al) of the incident beam and 9 times larger at higher HVLs (∼7 mm Al). The magnitude of the residual error in MTF was dependent on the quality of the incident spectrum. For incident spectra with high kVp and HVL (⩾120 kVp, ⩾5 mm Al HVL), transmission through the beveled edges produced errors in MTF up to 15% at 5 cycles/mm and 30% at 10 cycles/mm. By assuming a rectangular slit profile with aneffectivewidth based on the kVp, HVL, and filtration material of the incident beam, an MTF correction factor was determined. Application of this correction factor reduced the errors to less than 4% up to 10 cycles/mm. At low beam energies and spatial frequencies, the correction is less critical. Ease of alignment and greater availability make a commercial slit camera useful for MTF measurements. Accurate MTF measurements can be made if appropriate correction factors are applied.
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DOI：
--
发表时间：
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期刊：
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影响因子：
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