Department of Radiology, CHU Nîmes, Univ Montpellier, Medical Imaging Group Nîmes, EA 2415, 30029 Nîmes, France.
Department of Radiology, CHU Nîmes, Univ Montpellier, Medical Imaging Group Nîmes, EA 2415, 30029 Nîmes, France.
Diagn Interv Imaging. 2020 Jun;101(6):373-381. doi: 10.1016/j.diii.2020.01.002. Epub 2020 Jan 31.
The purpose of this study was to assess the impact of tin filter (TF) on X-ray beam quality, image quality and radiation dose and its suitability for routine use for chest and lumbar-spine/pelvis-hip ultralow-dose (ULD) CT examination protocols.
The X-ray beam quality was determined by measuring the half-value layer (HVL) and calculating the mean weighted energy for 100, 120, 150kVp (using standard filtration) and for 100 and 150kVp using TF (Sn100kVp and Sn150kVp, respectively). Acquisitions were performed on a phantom at four dose levels for each previously definedkVp. The mean attenuation (N), noise-power-spectrum (NPS) and task-based transfer function (TTF) were computed. The detectability index (d') was computed to model the detection of two lesions in spine and pelvic/hip examination and two for chest exploration. Image quality and detectability using a TF were assessed for two routinely used ULD protocols.
The HVL and mean weighted energy increased using a TF for the same tube voltage. Using a TF for the same tube voltage changed N for bone and acrylic inserts, decreased the NPS peak without changing the NPS spatial frequency and increased the TTF values. The d' values were improved using a TF and with the dose increase. d' values of all modeled lesions were improved using Sn100kVp and Sn150kVp for the lumbar-spine/pelvis-hip and chest ULD protocols except for sclerotic bone lesion using Sn150kVp.
The use of TF increases the X-ray beam quality and improves the image quality characteristics in phantom images, thus appearing as a promising tool for reducing dose and/or improving the image quality of ULD protocols.
本研究旨在评估锡滤器（TF）对 X 射线束质量、图像质量和辐射剂量的影响，以及其在胸部和腰椎-脊柱/骨盆-髋关节超低剂量（ULD）CT 检查方案中的常规使用的适用性。
通过测量半值层（HVL）和计算 100、120、150kVp（使用标准过滤）和 100 和 150kVp（分别使用 TF Sn100kVp 和 Sn150kVp）的平均加权能量来确定 X 射线束质量。在每个先前定义的 kVp 下，在四个剂量水平下对体模进行采集。计算平均衰减（N）、噪声功率谱（NPS）和基于任务的传递函数（TTF）。计算检测指标（d'）以模拟脊柱和骨盆/髋关节检查中两个病变以及胸部探查中两个病变的检测。使用 TF 评估两种常规使用的 ULD 方案的图像质量和检测能力。
使用 TF 会增加相同管电压下的 HVL 和平均加权能量。使用 TF 改变相同管电压下的骨和丙烯酸插入物的 N，降低 NPS 峰值而不改变 NPS 空间频率，并增加 TTF 值。使用 TF 并增加剂量可以提高 d'值。使用 Sn100kVp 和 Sn150kVp 对腰椎-脊柱/骨盆-髋关节和胸部 ULD 方案进行建模时，除了使用 Sn150kVp 的硬化性骨病变外，所有病变的 d'值均得到改善。
使用 TF 可提高 X 射线束质量，并改善体模图像的图像质量特性，因此似乎是降低剂量和/或改善 ULD 方案图像质量的有前途的工具。
