Department of Radiology, University of Kentucky, Lexington, KY, 40536, United States of America.
Biomed Phys Eng Express. 2024 Sep 3;10(5). doi: 10.1088/2057-1976/ad7266.
. Virtual Grid (VG) is an image processing technique designed to address scattered radiation from radiographic systems without a physical grid. It aims to eliminate artifacts caused by grid misalignment and enhance radiographic workflow efficiency. We intend to evaluate image quality between Virtual Grid and grid-based radiographic systems across various patient thicknesses.. A Fujifilm Virtual Grid and GE AMX-4 portable radiographic system was used. Image quality was assessed using MTF, NPS, LCR, and CNR. MTF calculations employed an edge-device method with a 0.1 mmCu sheet. For NPS evaluation, uniform images were acquired with multiple 30 × 30 cm solid water blocks (2 cm thick), overlaid in 2 cm increments to simulate patient sizes from 2cm to 40 cm. LCR and CNR were evaluated using a CIRS test plate with 9-hole depths for a hole diameter of 0.375'. The test object was placed on top of the detector then water blocks, while maintaining the same SID, beam quality, and exposure between the units. Visual assessments were conducted by four readers, quantifying perceived hole numbers. The weighted Cohen's Kappa and Welch's T-test were utilized for statistical analysis.. At 80% MTF, VG exhibited high contrast resolution of 1.1 l p/mm compared to 1.2 l p/mm for the grid system. VG demonstrated lower noise levels across all frequencies for equivalent patient thicknesses. Welch's T-test indicated no significant differences in LCR (P = 0.31) and CNR (P = 0.34) between the systems. However, qualitative observation demonstrated VG's better low contrast response for patient sizes ≥10 cm. The average weighted Cohen's Kappa value was 0.78.. This work indicates the Virtual Grid technology can effectively mitigate scattered radiation to improve granularity and low-contrast resolution in an image compared to a grid system. Furthermore, it can potentially reduce patient dose.
虚拟栅格（VG）是一种图像处理技术，旨在解决无物理栅格的放射系统中的散射辐射问题。它旨在消除栅格未对准导致的伪影，并提高放射工作流程的效率。我们旨在评估不同患者厚度下虚拟栅格和基于栅格的放射系统之间的图像质量。使用富士通虚拟栅格和 GE AMX-4 便携式放射系统进行了研究。使用调制传递函数（MTF）、调制传递函数噪声功率谱（NPS）、调制传递函数对比灵敏度（LCR）和对比噪声比（CNR）评估图像质量。MTF 计算采用边缘设备方法，使用 0.1mmCu 片。对于 NPS 评估，使用多个 30×30cm 实心水块（2cm 厚）获取均匀图像，以 2cm 为增量叠加，模拟患者尺寸从 2cm 到 40cm。使用具有 9 个孔深度的 CIRS 测试板评估 LCR 和 CNR，孔直径为 0.375'。将测试对象放置在探测器顶部，然后放置水块，同时保持两个设备之间的相同 SID、射线质量和曝光量。由四名读者进行视觉评估，量化感知的孔数。使用加权 Cohen's Kappa 和 Welch's T 检验进行统计分析。在 80% MTF 下，VG 表现出 1.1 l p/mm 的高对比度分辨率，而栅格系统为 1.2 l p/mm。VG 在所有频率下的噪声水平都低于等效患者厚度的噪声水平。Welch's T 检验表明，系统之间的 LCR（P=0.31）和 CNR（P=0.34）没有显著差异。然而，定性观察表明，对于患者尺寸≥10cm 的情况，VG 的低对比度响应更好。平均加权 Cohen's Kappa 值为 0.78。这项工作表明，与栅格系统相比，虚拟栅格技术可以有效减轻散射辐射，提高图像的粒度和低对比度分辨率。此外，它还有可能降低患者剂量。
