Tsalafoutas Ioannis A, AlKhazzam Shady, Tsapaki Virginia, Kharita Mohammed Hassan
Medical Physics Section, OHS Department, Hamad Medical Corporation, Doha, Qatar.
NAHU - Dosimetry and Medical Radiation Physics Section, IAEA, Vienna, Austria.
J Appl Clin Med Phys. 2025 Feb;26(2):e14599. doi: 10.1002/acm2.14599. Epub 2025 Jan 13.
To evaluate image quality (IQ) of for-processing (raw) and for-presentation (clinical) radiography images, under different exposure conditions and digital image post-processing algorithms, using a phantom that enables multiple detection tasks.
A modified version of the radiography phantom described in the IAEA Human Health Series No. 39 publication was constructed, incorporating six additional Aluminum (Al) targets of thicknesses both smaller and larger than the standard one. Raw and clinical images were simultaneously acquired using two digital radiography units from different manufacturers, various exposure parameters and different examination protocols. The phantom images were read using the free IAEA software (ATIA) that estimates automatically various IQ-metrics in images of the original phantom. Since in the modified phantom had seven Al targets, images were read seven times, one for each different Al thickness. The IQ-metrics' values obtained were analyzed to investigate their dependence on incident air kerma on the image receptor, tube potential, examination protocol, image type (raw or clinical), Al-target thicknesses, and manufacturer.
The IQ-metric values calculated using the modified IAEA phantom images can be radically different between raw and clinical images, and between different manufacturers, irrespectively whether only the standard or all the different Al-target thicknesses are considered. The modulation transfer function (MTF) and the signal-to-noise-ratio (SNR) dependence on exposure conditions and post-processing algorithms do not always follow the same trends for raw and clinical images and/or different manufacturers, while the signal-difference-to-noise-ratio (SDNR) and the detectability index (d'), despite their differences, seem more appropriate to characterize IQ. However, the d' metric, which also considers both MTF and the normalized noise power spectrum (NNPS) should be considered more complete IQ-metric than SDNR.
Though theoretically d' values should be calculated using raw images, clinical images can be also used, at least for constancy tests.
使用能够进行多种检测任务的体模，评估在不同曝光条件和数字图像后处理算法下，用于处理（原始）和用于呈现（临床）的射线照相图像的图像质量（IQ）。
构建了国际原子能机构（IAEA）第39号人类健康系列出版物中描述的射线照相体模的修改版本，纳入了六个厚度小于和大于标准厚度的额外铝（Al）靶。使用来自不同制造商的两个数字射线照相设备、各种曝光参数和不同的检查方案同时采集原始图像和临床图像。使用免费的IAEA软件（ATIA）读取体模图像，该软件可自动估计原始体模图像中的各种IQ指标。由于修改后的体模有七个Al靶，因此对图像进行了七次读取，每种不同的Al厚度读取一次。分析获得的IQ指标值，以研究它们对图像受体上的入射空气比释动能、管电压、检查方案、图像类型（原始或临床）、Al靶厚度和制造商的依赖性。
无论仅考虑标准Al靶厚度还是所有不同的Al靶厚度，使用修改后的IAEA体模图像计算出的IQ指标值在原始图像和临床图像之间以及不同制造商之间可能会有很大差异。调制传递函数（MTF）和信噪比（SNR）对曝光条件和后处理算法的依赖性，对于原始图像和临床图像以及/或不同制造商而言，并不总是遵循相同的趋势，而信号差噪比（SDNR）和可探测性指数（d'），尽管存在差异，但似乎更适合表征IQ。然而，同时考虑MTF和归一化噪声功率谱（NNPS）的d'指标应被视为比SDNR更完整的IQ指标。
虽然理论上d'值应使用原始图像计算，但临床图像也可使用，至少用于稳定性测试。
