Greene-Donnelly Kerry A, Ogden Kent M
SUNY Upstate Medical University.
J Appl Clin Med Phys. 2016 Jan 8;17(1):416-420. doi: 10.1120/jacmp.v17i1.5785.
The American College of Radiology (ACR) Computed Tomography (CT) Accreditation Program requires submission of phantom scans acquired with the ACR accreditation phantom. There is a known issue with some wide-beam scanners in which the Hounsfield unit (HU) value of water may be correct when using the scanner manufacturer's phantom, but will be out of range in some scan modes when scanning the accreditation phantom. The phantom manufacturer has developed a product known as Extension Plates to eliminate the water HU value issue. The purpose of this technical note is to evaluate the effectiveness of the Extension Plates in alleviating the water HU issue. The ACR phantom was scanned on nine different CT scanners representing four CT manufacturers at eight different facilities. Scanner models included 16- and 64-channel geometries from each manufacturer. All scanners passed routine daily water HU testing per the manufacturer's instructions. The accreditation phantom was scanned in helical and axial modes both with and without the Extension Plates present. Regions of interest were placed on the linearity test objects as well as the water HU test object in Module 1 of the phantom. Mean values were recorded and compared with the acceptable ranges specified by the ACR accreditation phantom testing instructions. Water HU values failed for one scanner model when scanned in helical mode using the widest collimation available and the Extension Plates were not present. All other scanner models passed the water HU linearity test with or without the Extension Plates in both axial and helical scan modes. Three of the four manufacturers tested failed the linearity test for different materials. The presence of the Extension Plates only affected the HU measurement for the water test object.
美国放射学会（ACR）计算机断层扫描（CT）认证计划要求提交使用ACR认证体模获取的体模扫描数据。一些宽束扫描仪存在一个已知问题，即使用扫描仪制造商的体模时，水的亨氏单位（HU）值可能是正确的，但在扫描认证体模时，某些扫描模式下该值会超出范围。体模制造商开发了一种名为扩展板的产品来消除水HU值问题。本技术说明的目的是评估扩展板在缓解水HU问题方面的有效性。在八个不同机构对代表四个CT制造商的九台不同CT扫描仪进行了ACR体模扫描。扫描仪型号包括每个制造商的16通道和64通道机型。所有扫描仪均按照制造商的说明通过了日常水HU常规测试。在有和没有扩展板的情况下，分别以螺旋和轴向模式对认证体模进行扫描。在体模模块1的线性测试物体以及水HU测试物体上放置感兴趣区域。记录平均值并与ACR认证体模测试说明规定的可接受范围进行比较。在使用可用的最宽准直且没有扩展板的情况下，以螺旋模式扫描时，一个扫描仪型号的水HU值未通过测试。所有其他扫描仪型号在轴向和螺旋扫描模式下，无论有无扩展板，水HU线性测试均通过。四个接受测试的制造商中有三个在不同材料的线性测试中未通过。扩展板的存在仅影响水测试物体的HU测量。
