基于GEANT4的三维康普顿成像装置的Monte Carlo研究
Monte Carlo study of a 3D Compton imaging device with GEANT4
摘要：
在本文中，我们调查，详细的蒙特卡罗模拟的基础上Geant 4，新的方法[Nucl.Instrum.2004]。方法A588（2008）457]采用光子散射进行三维成像。使用单色且良好准直的伽马射束来照射待成像的对象，并且通过周围的锗条检测器来检测康普顿散射的光子。高精度地测量了光子的碰撞位置和能量，并计算了沿束轴的散射位置。我们研究这种技术的应用的情况下，脑成像，但结果也可以应用于一个较轻的对象，与局部的密度变化，是嵌入在一个更密集的容器的情况下。我们在这里报告可达到的灵敏度作为一个函数的光束能量，深度内的对象和大小和密度的夹杂物的密度变化的检测。使用600 keV γ射线，对于相对于周围组织密度增加30%，沿射线厚度为5 mm的包裹体，我们在中脑位置获得了约2 mm的分辨率和12%的对比度。此外，模拟表明，对于相同的伽马射线束能量，完整的脑部扫描将导致约1 mSv的有效剂量。
英文摘要：
In this paper we investigate, with a detailed Monte-Carlo simulation based on Geant4, the novel approach [Nucl. Instrum. Methods A588 (2008) 457] to 3D imaging with photon scattering. A monochromatic and well collimated gamma beam is used to illuminate the object to be imaged and the photons Compton scattered are detected by means of a surrounding germanium strip detector. The impact position and the energy of the photons are measured with high precision and the scattering position along the beam axis is calculated. We study as an application of this technique the case of brain imaging but the results can be applied as well to situations where a lighter object, with localized variations of density, is embedded in a denser container. We report here the attainable sensitivity in the detection of density variations as a function of the beam energy, the depth inside the object and size and density of the inclusions. Using a 600 keV gamma beam, for an inclusion with a density increase of 30% with respect to the sorrounding tissue and thickness along the beam of 5 mm, we obtain at midbrain position a resolution of about 2 mm and a contrast of 12%. In addition the simulation indicates that for the same gamma beam energy a complete brain scan would result in an effective dose of about 1 mSv.
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