Flampouri Stella, McNair Helen A, Donovan Ellen M, Evans Philip M, Partridge Mike, Verhaegen Frank, Nutting Christopher M
Joint Physics Department, Royal Marsden NHS Trust and Institute of Cancer Research, Sutton, UK.
Radiother Oncol. 2005 Jul;76(1):63-71. doi: 10.1016/j.radonc.2005.04.006.
To investigate the feasibility and the advantages of a portal-imaging mode on a medical accelerator, consisting of a thin low-Z bremsstrahlung target and a thin Gd2O2S/film detector, for patient imaging.
The international code of practice for high-energy photon dosimetry was used to calibrate dosimetry instruments for the imaging beam produced by 4.75 MeV electrons hitting a 6mm thick aluminium target. Images of the head and neck of a humanoid phantom were taken with a mammography film system and the dose in the phantom was measured with TLDs calibrated for this beam. The first head and neck patient images are compared with conventional images (taken with the treatment beam on a film radiotherapy verification detector). Visibility of structures for six patients was evaluated.
Images of the head and neck of a humanoid phantom, taken with both imaging systems showed that the contrast increased dramatically for the new system while the dose required to form an image was less than 10(-2)Gy. The patient images taken with the new and the conventional systems showed that air-tissue interfaces were better defined in the new system image. Anatomical structures, visible on both films, are clearer with the new system. Additionally, bony structures, such as vertebrae, were clearly visible only with the new system. The system under evaluation was significantly better for all features in lateral images and most features in anterior images.
This pilot study of the new portal imaging system showed the image quality is significantly improved.
研究一种由薄的低原子序数轫致辐射靶和薄的硫氧化钆/胶片探测器组成的医学加速器门静脉成像模式用于患者成像的可行性和优势。
采用高能光子剂量测定的国际实践准则，对由4.75 MeV电子轰击6 mm厚铝靶产生的成像束的剂量测定仪器进行校准。使用乳腺摄影胶片系统拍摄人形模体的头部和颈部图像，并用针对该束校准的热释光剂量计测量模体内的剂量。将首批头部和颈部患者图像与传统图像（在胶片放射治疗验证探测器上用治疗束拍摄）进行比较。评估了6名患者结构的可见性。
两种成像系统拍摄的人形模体头部和颈部图像显示，新系统的对比度显著提高，而形成图像所需的剂量小于10(-2)Gy。用新系统和传统系统拍摄的患者图像显示，新系统图像中空气-组织界面的定义更好。两张胶片上都可见的解剖结构在新系统中更清晰。此外，只有新系统能清晰看到椎骨等骨骼结构。在侧位图像的所有特征和前后位图像的大多数特征方面，所评估的系统明显更好。
这项新的门静脉成像系统的初步研究表明图像质量有显著提高。
