Instituto de Física, Universidade de São Paulo, São Paulo, SP, 05508-090, Brazil.
Instituto de Física Gleb Wataghin, Universidade Estadual de Campinas, Campinas, SP, 13083-859, Brazil.
Med Phys. 2017 Jul;44(7):3504-3511. doi: 10.1002/mp.12287. Epub 2017 May 26.
To introduce and evaluate a method developed for the direct measurement of mammographic x-ray spectra using a CdTe spectrometer. The assembly of a positioning system and the design of a simple and customized alignment device for this application is described.
A positioning system was developed to easily and accurately locate the CdTe detector in the x-ray beam. Additionally, an alignment device to line up the detector with the central axis of the radiation beam was designed. Direct x-ray spectra measurements were performed in two different clinical mammography units and the measured x-ray spectra were compared with computer-generated spectra. In addition, the spectrometer misalignment effect was evaluated by comparing the measured spectra when this device is aligned relatively to when it is misaligned.
The positioning and alignment of the spectrometer have allowed the measurements of direct mammographic x-ray spectra in agreement with computer-generated spectra. The most accurate x-ray spectral shape, related with the minimal HVL value, and high photon fluence for measured spectra was found with the spectrometer aligned according to the proposed method. The HVL values derived from both simulated and measured x-ray spectra differ at most 1.3 and 4.5% for two mammography devices evaluated in this study.
The experimental method developed in this work allows simple positioning and alignment of a spectrometer for x-ray spectra measurements given the geometrical constraints and maintenance of the original configurations of mammography machines.
介绍并评估一种使用 CdTe 光谱仪直接测量乳腺 X 射线光谱的方法。描述了为此应用开发的定位系统和简单定制对准装置的设计。
开发了一种定位系统，可轻松准确地将 CdTe 探测器定位在 X 射线束中。此外，还设计了一种对准装置，用于将探测器与辐射束的中心轴对齐。在两台不同的临床乳腺摄影设备中进行了直接 X 射线光谱测量，并将测量的 X 射线光谱与计算机生成的光谱进行了比较。此外，还通过比较该装置对齐和未对齐时的测量光谱，评估了光谱仪的不对准效应。
光谱仪的定位和对准使得可以测量与计算机生成光谱一致的直接乳腺 X 射线光谱。在所提出的方法下，通过对准光谱仪，可以找到与最小 HVL 值相关的最准确的 X 射线光谱形状和高光子通量。在本研究中评估的两台乳腺摄影设备中，从模拟和测量的 X 射线光谱得出的 HVL 值最多相差 1.3%和 4.5%。
本工作中开发的实验方法允许在考虑到几何约束和保持乳腺摄影设备原始配置的情况下，对光谱仪进行简单的定位和对准，以进行 X 射线光谱测量。
