Medical Physics and Radiation Protection Service, Fuenlabrada University Hospital, Fuenlabrada, Spain.
Medical Physics, Radiology Department, Complutense University, Madrid, Spain.
Phys Med Biol. 2020 Nov 17;65(22):225019. doi: 10.1088/1361-6560/abb71b.
Radiochromic film in conjunction with flatbed scanners are frequently employed as dosimeters for advanced techniques in radiotherapy. Their strengths are as follows: light element composition, low energy dependence, near biological tissue equivalence and high spatial resolution. However, they have some weaknesses as well: non-uniformities, read out noise, and scanning artifacts. Several processing protocols have been proposed intending to correct the perturbations these weaknesses produce. The aim of this paper is to present a new processing protocol for radiochromic film dosimetry based on a non-local means denoising algorithm. Three dose distributions of open square fields and a spatial combination of these fields using different angles of incidence and monitor units have been employed to validate the protocol. The dose distributions are traceable to ionization chamber measurements. Additionally, a real dose distribution of a treatment was used to simulate scanning data with noise and scanning lateral artifact, and to study how the protocol behaves under these perturbations. The same measured raw data have been processed by means of an implementation of the multichannel protocol (multigaussian method). It has been found that the proposed protocol reduces dose uncertainty even though it uses fewer scans than the multichannel protocol.
放射色胶片与平板扫描仪通常被用作放射治疗先进技术的剂量计。它们的优点如下：轻元素组成、低能量依赖性、接近生物组织等效性和高空间分辨率。然而，它们也有一些缺点：不均匀性、读出噪声和扫描伪影。已经提出了几种处理方案，旨在纠正这些弱点产生的干扰。本文的目的是提出一种基于非局部均值去噪算法的放射色胶片剂量测定新处理方案。使用开放正方形场的三个剂量分布和这些场的空间组合，采用不同的入射角和监测器单位，对方案进行验证。剂量分布可追溯到电离室测量。此外，还使用实际的治疗剂量分布来模拟带有噪声和扫描横向伪影的扫描数据，并研究该方案在这些干扰下的表现。使用多通道方案（多高斯方法）的实现方式对相同的实测原始数据进行了处理。结果发现，尽管该方案使用的扫描次数比多通道方案少，但仍能降低剂量不确定性。
