Trevisan Diego, Bonutti Faustino, Ravanelli Daniele, Valentini Aldo
Department of Medical Physics, S. Chiara Hospital, APSS Trento, Italy.
Department of Medical Physics, S. M. della Misericordia Hospital, Udine, Italy.
Phys Med. 2014 Dec;30(8):968-72. doi: 10.1016/j.ejmp.2014.06.041. Epub 2014 Jul 6.
Overranging or overscanning increases the dose delivered to patients undergoing helical Computed Tomography examinations. In order to reduce it, nowadays most of the multidetector tomographs close the X-ray beam aperture at the scan extremes. This technical innovation, usually referred to as dynamic or adaptive collimation, also influences the overranging assessment methods. In particular, the film free approach proposed in previous studies is not suitable for these modern tomographs. The present study aims to introduce a new method of estimating overranging with real time dosimetry, even suitable for tomographs equipped with adaptive collimation. The approach proposed is very easy to implement and time saving because only a pencil chamber is required. It is also equivalent in precision and in accuracy to the film based one, considered an absolute benchmark.
扫描范围过大或扫描过度会增加接受螺旋计算机断层扫描检查患者的辐射剂量。为了减少这种情况，如今大多数多排探测器断层扫描仪在扫描极限处关闭X射线束孔径。这项技术创新，通常称为动态或自适应准直，也会影响扫描范围过大的评估方法。特别是，先前研究中提出的无胶片方法不适用于这些现代断层扫描仪。本研究旨在引入一种利用实时剂量测定法估算扫描范围过大的新方法，该方法甚至适用于配备自适应准直的断层扫描仪。所提出的方法非常易于实施且节省时间，因为只需要一个铅笔电离室。在精度和准确性方面，它也与被视为绝对基准的基于胶片的方法相当。
