Fukumitsu Nobuyoshi, Numajiri Haruko, Ohnishi Kayoko, Mizumoto Masashi, Aihara Teruhito, Ishikawa Hitoshi, Okumura Toshiyuki, Tsuboi Koji, Terunuma Toshiyuki, Sakae Takeji, Sakurai Hideyuki
Proton Medical Research Center, University of Tsukuba, 1-1-1, Tennoudai, Tsukuba, 305-8575, Japan,
Jpn J Radiol. 2015 Jun;33(6):303-10. doi: 10.1007/s11604-015-0418-1. Epub 2015 Apr 16.
To estimate the prediction error and required internal margin provided for irregular respiratory movements.
Twenty-eight patterns of irregular movement were prepared using a moving phantom. For irregular cycle movement, a cycle of 2.0-5.0 s was inserted into the baseline movement data (3.5-s cycle, 6-mm amplitude) every four cycles. In addition, a cycle of 2.5-4.5 s was further inserted into one of the irregular data points every four cycles to produce more complicated irregularity. For irregular amplitude movement, an amplitude of 3.0-9.0 mm was inserted into the baseline respiratory movement data. In addition, an amplitude of 4.0-8.0 mm was further inserted into one of the irregular data points every four cycles to produce more complicated irregularity. Images of the moving target were acquired using a real-time position management (RPM) and four-dimensional CT (4DCT) system. The displacement from the baseline image and required margin to compensate for irregular movement were calculated.
Amplitude irregularity tended to lose stable placement and need larger margins to compensate for the reduction of image reproducibility than cycle irregularity. There was a large displacement and required margin when the target moved with more complicated irregular amplitude.
The RPM and 4DCT system has a risk of prediction error, which may result from the complicated amplitude irregularity of respiratory movement.
评估针对不规则呼吸运动所提供的预测误差和所需的内部边界。
使用移动体模制备28种不规则运动模式。对于不规则周期运动，每四个周期在基线运动数据（3.5秒周期，6毫米幅度）中插入一个2.0 - 5.0秒的周期。此外，每四个周期在其中一个不规则数据点进一步插入一个2.5 - 4.5秒的周期，以产生更复杂的不规则性。对于不规则幅度运动，在基线呼吸运动数据中插入3.0 - 9.0毫米的幅度。此外，每四个周期在其中一个不规则数据点进一步插入4.0 - 8.0毫米的幅度，以产生更复杂的不规则性。使用实时位置管理（RPM）和四维CT（4DCT）系统获取移动目标的图像。计算相对于基线图像的位移以及补偿不规则运动所需的边界。
与周期不规则性相比，幅度不规则性往往会失去稳定放置，并且需要更大的边界来补偿图像再现性的降低。当目标以更复杂的不规则幅度移动时，存在较大的位移和所需边界。
RPM和4DCT系统存在预测误差风险，这可能是由呼吸运动复杂的幅度不规则性导致的。
