The use of magnetic resonance imaging (MRI) for radiotherapy treatment planning (RTP) is increasing due to excellent tissue contrast and high-resolution images compared to other modalities. However, the issue of image inhomogeneity which affects tissue delineation and contrast during treatment planning needs to be resolved. This study is aimed to qualitatively observe image inhomogeneity in T2-weighted images and T2 measurement using head phantom. Agar hydrogel phantom of various concentrations were used to form inhomogeneous phantom for mimicking tissue variation in the brain in addition to American College of Radiology accredited phantom. T2 images from both phantoms were obtained using fast spin echo sequence with variation of echo time (TE) and repetition time. Image processing was processed to obtain signal intensity and image mapping and the effect of inhomogeneity was observed qualitatively. T2 values were obtained by fitting signal intensity against TE and T2-mapping images were obtained. T2-weighted and T2-mapping images from the experiment provided qualitative description on image inhomogeneity and contrast. The result showed that T2-mapping images offered more information on phantom properties and described image inhomogeneity and contrast better than T2-weighted images. T2 measurement provided an alternative method for better description of image contrast which could enhance localization and tissue delineation in MRI-based RTP.

中文翻译：

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在头模中使用 T2 磁共振成像评估图像不均匀性用于放射治疗计划：初步研究

由于与其他方式相比，磁共振成像 (MRI) 具有出色的组织对比度和高分辨率图像，因此越来越多地使用磁共振成像 (MRI) 进行放射治疗计划 (RTP)。然而，需要解决在治疗计划期间影响组织描绘和对比度的图像不均匀性问题。本研究旨在定性观察 T2 加权图像中的图像不均匀性和使用头模的 T2 测量。除了美国放射学会认可的幻影外，还使用各种浓度的琼脂水凝胶幻影来形成不均匀的幻影，以模拟大脑中的组织变异。使用具有回波时间 (TE) 和重复时间变化的快速自旋回波序列获得来自两个体模的 T2 图像。对图像进行处理以获得信号强度和图像映射，并定性观察不均匀性的影响。通过将信号强度与 TE 进行拟合来获得 T2 值，并获得 T2 映射图像。来自实验的 T2 加权和 T2 映射图像提供了对图像不均匀性和对比度的定性描述。结果表明，与 T2 加权图像相比，T2 映射图像提供了更多关于体模特性的信息，并且更好地描述了图像的不均匀性和对比度。T2 测量为更好地描述图像对比度提供了一种替代方法，可以增强基于 MRI 的 RTP 中的定位和组织描绘。来自实验的 T2 加权和 T2 映射图像提供了对图像不均匀性和对比度的定性描述。结果表明，与 T2 加权图像相比，T2 映射图像提供了更多关于体模特性的信息，并且更好地描述了图像的不均匀性和对比度。T2 测量为更好地描述图像对比度提供了一种替代方法，可以增强基于 MRI 的 RTP 中的定位和组织描绘。来自实验的 T2 加权和 T2 映射图像提供了对图像不均匀性和对比度的定性描述。结果表明，与 T2 加权图像相比，T2 映射图像提供了更多关于体模特性的信息，并且更好地描述了图像的不均匀性和对比度。T2 测量为更好地描述图像对比度提供了一种替代方法，可以增强基于 MRI 的 RTP 中的定位和组织描绘。