PDF(Pubmed)
Abstract：
OBJECTIVE: To develop a Total Body Irradiation (TBI) technique using IMRT at extended SSD that can be performed in any size Linac room.
METHODS: Patients studied were placed on a platform close to the floor, directly under the gantry with cranial-caudal axis parallel to the gantry rotation plane and at SSD ∼200 cm. Two abutting fields with the same external isocenter at gantry angles of ±21˚, collimator angle of 90˚, and field size of 25 × 40 cm2 are employed for both supine and prone positions. An iterative optimization algorithm was developed to generate a uniform dose at the patient mid-plane with adequate shielding to critical organs such as lungs and kidneys. The technique was validated in both phantom and patient CT images for treatment planning, and dose measurement and QA were performed in phantom.
RESULTS: A uniform dose distribution in the mid-plane within ±5% of the prescription dose was reached after a few iterations. This was confirmed with ion-chamber measurements in phantom. The mean dose to lungs and kidneys can be adjusted according to clinical requirements and can be as low as ∼25% of the prescription dose. For a typical prescription dose of 200 cGy/fraction, the total MU was ∼2400/1200 for the superior/inferior field. The overall treatment time for both supine/prone positions was ∼54 min to meet the maximum absorbed dose rate criteria of 15 cGy/min. IMRT QA with portal dosimetry shows excellent agreement.
CONCLUSIONS: We have developed a promising TBI technique using abutting IMRT fields at extended SSD. The patient is in a comfortable recumbent position with good reproducibility and less motion during treatment. An additional benefit of this technique is that full 3D dose distribution is available from the TPS with a DVH summary for organs of interest. The technique allows precise sparing of lungs and kidneys and can be executed in any linac room.
METHODS: Patients studied were placed on a platform close to the floor, directly under the gantry with cranial-caudal axis parallel to the gantry rotation plane and at SSD ∼200 cm. Two abutting fields with the same external isocenter at gantry angles of ±21˚, collimator angle of 90˚, and field size of 25 × 40 cm2 are employed for both supine and prone positions. An iterative optimization algorithm was developed to generate a uniform dose at the patient mid-plane with adequate shielding to critical organs such as lungs and kidneys. The technique was validated in both phantom and patient CT images for treatment planning, and dose measurement and QA were performed in phantom.
RESULTS: A uniform dose distribution in the mid-plane within ±5% of the prescription dose was reached after a few iterations. This was confirmed with ion-chamber measurements in phantom. The mean dose to lungs and kidneys can be adjusted according to clinical requirements and can be as low as ∼25% of the prescription dose. For a typical prescription dose of 200 cGy/fraction, the total MU was ∼2400/1200 for the superior/inferior field. The overall treatment time for both supine/prone positions was ∼54 min to meet the maximum absorbed dose rate criteria of 15 cGy/min. IMRT QA with portal dosimetry shows excellent agreement.
CONCLUSIONS: We have developed a promising TBI technique using abutting IMRT fields at extended SSD. The patient is in a comfortable recumbent position with good reproducibility and less motion during treatment. An additional benefit of this technique is that full 3D dose distribution is available from the TPS with a DVH summary for organs of interest. The technique allows precise sparing of lungs and kidneys and can be executed in any linac room.
摘要：
目的：开发一种在扩展SSD上使用IMRT的全身照射（TBI）技术，该技术可在任何大小的Linac房间中进行。
方法：研究的患者被放置在靠近地板的平台上，在龙门架正下方，头尾轴平行于龙门架旋转平面，在SSD~200cm处。两个具有相同外部等中心的邻接场，机架角度为±21º，准直器角度为90°，仰卧位和俯卧位都采用25×40cm2的视野大小。开发了一种迭代优化算法，以在患者中平面处产生均匀剂量，并对关键器官（例如肺和肾脏）具有足够的屏蔽作用。该技术在体模和患者CT图像中都得到了验证，用于治疗计划，在体模中进行剂量测量和QA。
结果：经过几次迭代，在处方剂量的±5％范围内达到了中平面的均匀剂量分布。这通过体模中的离子室测量得到证实。肺和肾脏的平均剂量可以根据临床要求进行调整，并且可以低至处方剂量的25％。对于200cGy/分数的典型处方剂量，上级/下级场的总MU为2400/1200。仰卧位/俯卧位的总治疗时间为~54min，以满足15cGy/min的最大吸收剂量率标准。IMRTQA与门户剂量测定显示出极好的一致性。
结论：我们开发了一种在扩展SSD上使用邻接IMRT场的TBI技术。患者处于舒适的卧位，具有良好的可重复性和治疗期间的较少运动。该技术的额外益处在于,可从TPS获得完整的3D剂量分布,所述TPS具有感兴趣器官的DVH概要。该技术允许精确保留肺和肾脏，并且可以在任何直线加速器室中执行。
方法：研究的患者被放置在靠近地板的平台上，在龙门架正下方，头尾轴平行于龙门架旋转平面，在SSD~200cm处。两个具有相同外部等中心的邻接场，机架角度为±21º，准直器角度为90°，仰卧位和俯卧位都采用25×40cm2的视野大小。开发了一种迭代优化算法，以在患者中平面处产生均匀剂量，并对关键器官（例如肺和肾脏）具有足够的屏蔽作用。该技术在体模和患者CT图像中都得到了验证，用于治疗计划，在体模中进行剂量测量和QA。
结果：经过几次迭代，在处方剂量的±5％范围内达到了中平面的均匀剂量分布。这通过体模中的离子室测量得到证实。肺和肾脏的平均剂量可以根据临床要求进行调整，并且可以低至处方剂量的25％。对于200cGy/分数的典型处方剂量，上级/下级场的总MU为2400/1200。仰卧位/俯卧位的总治疗时间为~54min，以满足15cGy/min的最大吸收剂量率标准。IMRTQA与门户剂量测定显示出极好的一致性。
结论：我们开发了一种在扩展SSD上使用邻接IMRT场的TBI技术。患者处于舒适的卧位，具有良好的可重复性和治疗期间的较少运动。该技术的额外益处在于,可从TPS获得完整的3D剂量分布,所述TPS具有感兴趣器官的DVH概要。该技术允许精确保留肺和肾脏，并且可以在任何直线加速器室中执行。
