Sookpeng S, Martin C J, Gentle D J
Health Physics, Gartnavel Royal Hospital, 1055 Great Western Road, Glasgow G12 0XH, UK. Department of Clinical Physics, University of Glasgow, Glasgow G12 8QQ, UK.
J Radiol Prot. 2013 Dec;33(4):735-61. doi: 10.1088/0952-4746/33/4/735. Epub 2013 Sep 11.
Modern CT scanners modulate tube current during scans according to patient size, shape and attenuation. However, the ATCM (automatic tube current modulation) systems for different CT manufacturers work on different principles. Although the systems are used for the majority of patients and examinations, there is no standard phantom for routine quality control of CT scanner ATCM operation. The ideal phantom for testing these systems should be capable of evaluating how tube current and image quality as well as dose vary according to changes in patient size and shape. For this study, a conical phantom designed by ImPACT has been compared with two phantoms made from elliptical sections with varying dimensions. The concept of the designs is to reflect the ATCM performance for the varying shapes and dimensions along the length of the human body. The first phantom comprises five elliptical sections with a wide range of different dimensions and the second has three sections that are more similar in size. The phantoms have been used to test ATCM systems for Philips, Siemens, GE and Toshiba scanners. Although the results of the tube current modulation patterns were similar for all CT scanners, the abrupt changes in attenuation for the first sectional phantom provoked an abnormal ATCM response for the GE and Toshiba scanners. The second sectional phantom was developed from the results of the first, and was more effective for ATCM system testing and could be used for dose and image quality assessment in standard positions. However, the ImPACT conical phantom provided the best overall assessment of performance in terms of tube current modulations and noise pattern.
现代CT扫描仪在扫描过程中会根据患者的大小、形状和衰减程度来调制管电流。然而，不同CT制造商的自动管电流调制（ATCM）系统工作原理不同。尽管这些系统适用于大多数患者和检查，但对于CT扫描仪ATCM操作的常规质量控制，尚无标准体模。测试这些系统的理想体模应能够评估管电流、图像质量以及剂量如何随患者大小和形状的变化而变化。在本研究中，将由ImPACT设计的锥形体模与两个由不同尺寸椭圆截面制成的体模进行了比较。这些设计的理念是反映沿人体长度方向不同形状和尺寸下的ATCM性能。第一个体模由五个具有广泛不同尺寸的椭圆截面组成，第二个有三个尺寸更相近的截面。这些体模已用于测试飞利浦、西门子、通用电气和东芝扫描仪的ATCM系统。尽管所有CT扫描仪的管电流调制模式结果相似，但第一个截面体模衰减的突然变化引发了通用电气和东芝扫描仪异常的ATCM响应。第二个截面体模是根据第一个的结果开发的，对ATCM系统测试更有效，可用于标准体位下的剂量和图像质量评估。然而，就管电流调制和噪声模式而言，ImPACT锥形体模对性能的整体评估最佳。
