Aubin S, Beaulieu L, Pouliot S, Pouliot J, Roy R, Girouard L M, Martel-Brisson N, Vigneault E, Laverdière J
Centre Hospitalier Universitaire de Québec (L'Hôtel-Dieu) and Centre de Recherche en Cancérologie de l'Université Laval, 11 Côte du Palais, Quebec, QC, G1R 2J6, Canada.
Med Phys. 2003 Jul;30(7):1825-32. doi: 10.1118/1.1584041.
An algorithm for the daily localization of the prostate using implanted markers and a standard video-based electronic portal imaging device (V-EPID) has been tested. Prior to planning, three gold markers were implanted in the prostate of seven patients. The clinical images were acquired with a BeamViewPlus 2.1 V-EPID for each field during the normal course radiotherapy treatment and are used off-line to determine the ability of the automatic marker detection algorithm to adequately and consistently detect the markers. Clinical images were obtained with various dose levels from ranging 2.5 to 75 MU. The algorithm is based on marker attenuation characterization in the portal image and spatial distribution. A total of 1182 clinical images were taken. The results show an average efficiency of 93% for the markers detected individually and 85% for the group of markers. This algorithm accomplishes the detection and validation in 0.20-0.40 s. When the center of mass of the group of implanted markers is used, then all displacements can be corrected to within 1.0 mm in 84% of the cases and within 1.5 mm in 97% of cases. The standard video-based EPID tested provides excellent marker detection capability even with low dose levels. The V-EPID can be used successfully with radiopaque markers and the automatic detection algorithm to track and correct the daily setup deviations due to organ motions.
一种利用植入标记物和标准的基于视频的电子射野影像装置（V-EPID）进行前列腺每日定位的算法已经得到测试。在治疗计划制定前，在7名患者的前列腺中植入了3个金标记物。在常规放疗治疗过程中，使用BeamViewPlus 2.1 V-EPID为每个射野采集临床图像，并在离线状态下用于确定自动标记物检测算法充分且一致地检测标记物的能力。临床图像是在2.5至75 MU的不同剂量水平下获得的。该算法基于射野图像中标记物的衰减特征和空间分布。总共采集了1182张临床图像。结果显示，单个标记物的平均检测效率为93%，一组标记物的平均检测效率为85%。该算法在0.20 - 0.40秒内完成检测和验证。当使用植入标记物组的质心时，在84%的情况下，所有位移可校正至1.0毫米以内，在97%的情况下可校正至1.5毫米以内。所测试的基于标准视频的EPID即使在低剂量水平下也具有出色的标记物检测能力。V-EPID可以与不透射线的标记物和自动检测算法成功配合使用，以跟踪和校正由于器官运动导致的每日摆位偏差。
