PDF(Pubmed)
Abstract：
Studies have shown large variations in stopping-power ratio (SPR) prediction from computed tomography (CT) across European proton centres. To standardise this process, a step-by-step guide on specifying a Hounsfield look-up table (HLUT) is presented here.
The HLUT specification process is divided into six steps: Phantom setup, CT acquisition, CT number extraction, SPR determination, HLUT specification, and HLUT validation. Appropriate CT phantoms have a head- and body-sized part, with tissue-equivalent inserts in regard to X-ray and proton interactions. CT numbers are extracted from a region-of-interest covering the inner 70% of each insert in-plane and several axial CT slices in scan direction. For optimal HLUT specification, the SPR of phantom inserts is measured in a proton beam and the SPR of tabulated human tissues is computed stoichiometrically at 100 MeV. Including both phantom inserts and tabulated human tissues increases HLUT stability. Piecewise linear regressions are performed between CT numbers and SPRs for four tissue groups (lung, adipose, soft tissue, and bone) and then connected with straight lines. Finally, a thorough but simple validation is performed.
The best practices and individual challenges are explained comprehensively for each step. A well-defined strategy for specifying the connection points between the individual line segments of the HLUT is presented. The guide was tested exemplarily on three CT scanners from different vendors, proving its feasibility.
The presented step-by-step guide for CT-based HLUT specification with recommendations and examples can contribute to reduce inter-centre variations in SPR prediction.
The HLUT specification process is divided into six steps: Phantom setup, CT acquisition, CT number extraction, SPR determination, HLUT specification, and HLUT validation. Appropriate CT phantoms have a head- and body-sized part, with tissue-equivalent inserts in regard to X-ray and proton interactions. CT numbers are extracted from a region-of-interest covering the inner 70% of each insert in-plane and several axial CT slices in scan direction. For optimal HLUT specification, the SPR of phantom inserts is measured in a proton beam and the SPR of tabulated human tissues is computed stoichiometrically at 100 MeV. Including both phantom inserts and tabulated human tissues increases HLUT stability. Piecewise linear regressions are performed between CT numbers and SPRs for four tissue groups (lung, adipose, soft tissue, and bone) and then connected with straight lines. Finally, a thorough but simple validation is performed.
The best practices and individual challenges are explained comprehensively for each step. A well-defined strategy for specifying the connection points between the individual line segments of the HLUT is presented. The guide was tested exemplarily on three CT scanners from different vendors, proving its feasibility.
The presented step-by-step guide for CT-based HLUT specification with recommendations and examples can contribute to reduce inter-centre variations in SPR prediction.
摘要：
目的：研究表明，来自欧洲质子中心的计算机断层扫描（CT）的停止功率比（SPR）预测差异很大。为了标准化这个过程，此处提供了有关指定Hounsfield查找表（HLUT）的分步指南。
方法：HLUT规范过程分为六个步骤：幻影设置，CT采集,CT数提取,SPR测定,HLUT规范,和HLUT验证。适当的CT体模有头部和身体大小的部分，关于X射线和质子相互作用的组织等效插入物。从覆盖每个插入件的内部70％的感兴趣区域中提取CT编号，并在扫描方向上提取几个轴向CT切片。为了获得最佳的HLUT规格，在质子束中测量体模插入物的SPR，并以100MeV的化学计量计算制表的人体组织的SPR。包括体模插入物和制表的人体组织都增加了HLUT的稳定性。在四个组织组（肺，脂肪,软组织,和骨头），然后用直线连接。最后,进行彻底但简单的验证。
结果：每个步骤都全面解释了最佳实践和个人挑战。提出了一种定义明确的策略，用于指定HLUT各个线段之间的连接点。该指南在不同供应商的三台CT扫描仪上进行了示例性测试，证明其可行性。
结论：提出的基于CT的HLUT规范的分步指南以及建议和示例有助于减少SPR预测中的中心间差异。
方法：HLUT规范过程分为六个步骤：幻影设置，CT采集,CT数提取,SPR测定,HLUT规范,和HLUT验证。适当的CT体模有头部和身体大小的部分，关于X射线和质子相互作用的组织等效插入物。从覆盖每个插入件的内部70％的感兴趣区域中提取CT编号，并在扫描方向上提取几个轴向CT切片。为了获得最佳的HLUT规格，在质子束中测量体模插入物的SPR，并以100MeV的化学计量计算制表的人体组织的SPR。包括体模插入物和制表的人体组织都增加了HLUT的稳定性。在四个组织组（肺，脂肪,软组织,和骨头），然后用直线连接。最后,进行彻底但简单的验证。
结果：每个步骤都全面解释了最佳实践和个人挑战。提出了一种定义明确的策略，用于指定HLUT各个线段之间的连接点。该指南在不同供应商的三台CT扫描仪上进行了示例性测试，证明其可行性。
结论：提出的基于CT的HLUT规范的分步指南以及建议和示例有助于减少SPR预测中的中心间差异。
