CT 中用于降低辐射剂量的管电压自动选择：一种通用策略。

Automatic selection of tube potential for radiation dose reduction in CT: a general strategy.

机构信息

Department of Radiology, Mayo Clinic, Rochester, Minnesota 55905, USA.

出版信息

Med Phys. 2010 Jan;37(1):234-43. doi: 10.1118/1.3264614.

DOI:10.1118/1.3264614

PMID:20175486

Abstract

PURPOSE

To optimize radiation dose efficiency in CT while maintaining image quality, it is important to select the optimal tube potential. The selection of optimal tube potential, however, is highly dependent on patient size and diagnostic task. The purpose of this work was to develop a general strategy that allows for automatic tube potential selection for each individual patient and each diagnostic task.

METHODS

The authors propose a general strategy that allows automatic adaptation of the tube potential as a function of patient size and diagnostic task, using a novel index of image quality, "iodine contrast to noise ratio with a noise constraint (iCNR_NC)," to characterize the different image quality requirements by various clinical applications. The relative dose factor (RDF) at each tube potential to achieve a target image quality was then determined as a function of patient size and the noise constraint parameter. A workflow was developed to automatically identify the optimal tube potential that is both dose efficient and practically feasible, incorporating patient size and diagnostic task. An experimental study using a series of semianthropomorphic thoracic phantoms was used to demonstrate how the proposed general strategy can be implemented and how the radiation dose reduction achievable by the tube potential selection depends on phantom sizes and noise constraint parameters.

RESULTS

The proposed strategy provides a flexible and quantitative way to select the optimal tube potential based on the patient size and diagnostic task. The noise constraint parameter alpha can be adapted for different clinical applications. For example, alpha = 1 for noncontrast routine exams; alpha = 1.1- 1.25 for contrast-enhanced routine exams; and alpha = 1.5-2.0 for CT angiography. For the five thoracic phantoms in the experiment, when alpha = 1, the optimal tube potentials were 80, 100, 100, 120, 120, respectively. The corresponding RDFs (relative to 120 kV) were 78.0%, 90.9%, 95.2%, 100%, and 100%. When alpha = 1.5, the optimal tube potentials were 80, 80, 80, 100, 100, respectively, with corresponding RDFs of 34.7%, 44.7%, 54.7%, 60.8%, and 89.5%.

CONCLUSIONS

A general strategy to automatically select the most dose efficient tube potential for CT exams was developed that takes into account patient size and diagnostic task. Dependent on the patient size and the selection of noise constraint parameter for different diagnostic tasks, the dose reduction at each tube potential, quantified explicitly with the RDF, varies significantly.

摘要

目的

为了在 CT 中优化辐射剂量效率，同时保持图像质量，选择最佳管电压非常重要。然而，最佳管电压的选择高度依赖于患者体型和诊断任务。本研究的目的是开发一种通用策略，允许为每个患者和每个诊断任务自动选择管电压。

方法

作者提出了一种通用策略，允许根据患者体型和诊断任务自动调整管电压，使用新的图像质量指标“噪声约束下的碘对比噪声比（iCNR_NC）”来描述各种临床应用的不同图像质量要求。然后，根据患者体型和噪声约束参数确定在每个管电压下达到目标图像质量的相对剂量因子（RDF）。开发了一个工作流程，自动识别既具有剂量效率又具有实际可行性的最佳管电压，同时考虑患者体型和诊断任务。使用一系列半拟人胸部体模进行了实验研究，以演示如何实现所提出的通用策略以及通过管电压选择可实现的辐射剂量减少如何取决于体模尺寸和噪声约束参数。

结果

所提出的策略提供了一种基于患者体型和诊断任务选择最佳管电压的灵活和定量方法。噪声约束参数 alpha 可以适应不同的临床应用。例如，alpha = 1 用于非增强常规检查；alpha = 1.1-1.25 用于增强常规检查；alpha = 1.5-2.0 用于 CT 血管造影。在实验中的五个胸部体模中，当 alpha = 1 时，最佳管电压分别为 80、100、100、120、120。相应的 RDF（相对于 120 kV）分别为 78.0%、90.9%、95.2%、100%和 100%。当 alpha = 1.5 时，最佳管电压分别为 80、80、80、100、100，相应的 RDF 分别为 34.7%、44.7%、54.7%、60.8%和 89.5%。