Joshi C P, Avadhani J S, Deshpande D D, Pendse A M, Viswanathan P S, Dinshaw K A
Department of Medical Physics, Tata Memorial Hospital, Parel, Bombay, India.
Strahlenther Onkol. 1993 Aug;169(8):495-9.
In the radiation treatment of inclined lesions the longitudinal axis of beam should be always parallel to the longitudinal axis of lesion in the treatment plane. Hence the choice of correct collimator angle is of prime importance in the oblique field off-axis treatment planning of inclined lesions. In this paper a graphical method is discussed to determine the collimator angles from the CT scans taken at different off-axis planes. A phantom was constructed which can simulate conditions like inclined lesion in the patient and CT scans were taken at different levels. The collimator angles estimated from CT scans are found to match with the collimator angles obtained from simulator within +/- 1 degree for various gantry angles. The method is applied to plan a case of cancer of the oesophagus (upper third), which is a typical example of inclined lesion.
在倾斜病变的放射治疗中，在治疗平面内，射束的纵轴应始终与病变的纵轴平行。因此，在倾斜病变的斜野离轴治疗计划中，选择正确的准直器角度至关重要。本文讨论了一种从不同离轴平面的CT扫描确定准直器角度的图形方法。构建了一个模型，其可以模拟患者体内倾斜病变等情况，并在不同层面进行CT扫描。对于各种机架角度，发现从CT扫描估计的准直器角度与从模拟机获得的准直器角度在±1度范围内匹配。该方法应用于一例食管上段癌的治疗计划，这是倾斜病变的一个典型例子。
