Svenson J, Irvine M A
X-ray Safety Australia, Ashgrove West, PO Box 574, Ashgrove West, QLD, 4060, Australia.
Phys Eng Sci Med. 2024 Dec;47(4):1773-1780. doi: 10.1007/s13246-024-01468-z. Epub 2024 Sep 9.
A novel phantom for measuring the 10% and 50% values of the modulation transfer function (MTF) for computed tomography scanners (CT) was investigated. The phantom was constructed by drilling rows of holes of different sizes and frequencies into a small block of polymethyl methacrylate (PMMA). The MTF at a given frequency was determined from the ratio of the range of Hounsfield units within the rows of holes at different frequencies, and the difference in Hounsfield units between air and PMMA. A MTF curve was plotted from measurements at different frequencies and the 10% and 50% MTF values were obtained from a cubic spline interpolation. The MTF results obtained with the drilled hole phantom method were compared to a conventional method - using a thin wire and Spice-CT ImageJ Plugin- and with identical acquisition and reconstruction parameters. The drilled hole phantom measured the 50% MTF with reasonable accuracy but underestimated the 10% MTF by 8.2% on average. MTF measurements were reproducible for repeated image acquisitions and with different users analysing the images, and the phantom was able to accurately measure the change in MTF when measured on images using different reconstruction kernels. The tool may find application as a cheap, easy to use method for routine QC testing of CT scanners.
研究了一种用于测量计算机断层扫描扫描仪（CT）调制传递函数（MTF）10%和50%值的新型体模。该体模是通过在一小块聚甲基丙烯酸甲酯（PMMA）上钻出不同尺寸和频率的孔排来构建的。给定频率下的MTF由不同频率孔排内亨氏单位范围与空气和PMMA之间亨氏单位差异的比值确定。根据不同频率下的测量结果绘制MTF曲线，并通过三次样条插值获得10%和50%的MTF值。将钻孔体模法获得的MTF结果与传统方法（使用细金属丝和Spice-CT ImageJ插件）进行比较，且采集和重建参数相同。钻孔体模测量50%MTF时具有合理的准确性，但平均低估1 / 10MTF 8.2%。对于重复的图像采集以及不同用户分析图像，MTF测量结果具有可重复性，并且当使用不同的重建内核在图像上进行测量时，该体模能够准确测量MTF的变化。该工具可能作为一种廉价、易于使用的方法用于CT扫描仪的常规质量控制测试。
