Bosmans Geert, Buijsen Jeroen, Dekker André, Velders Marije, Boersma Liesbeth, De Ruysscher Dirk, Minken André, Lambin Philippe
Department of Radiation Oncology (MAASTRO), GROW, University Hospital Maastricht, Maastricht, The Netherlands.
Radiother Oncol. 2006 Oct;81(1):73-80. doi: 10.1016/j.radonc.2006.08.009. Epub 2006 Sep 12.
To determine which method of internal target volume (ITV) definition based on a respiration correlated CT (RCCT) allows optimal tumor coverage.
A free breathing CT (CT(fb)) and an RCCT scan were acquired in 41 lung cancer patients. For 12 patients with a motion >7 mm in any direction, a detailed analysis was made. The RCCT scan was used to measure tumor motion and to reconstruct a CT at 10 phases (CT(10ph)), amongst which the half ventilation CT (CT(hv)). By averaging the CT(10ph), a slow CT (CT(slow)) was reconstructed. Based on those scans ITVs were delineated and treatments were planned, where for the ITV(hv) an internal margin of (motion amplitude)/4 was used. The treatment plans for the ITVs were projected on the 10 respiration phases. Doses were calculated and averaged over the 10 phases to estimate the actual CTV coverage.
The 3D motion was on average 8.1+/-1.0 mm (1 SD) for all patients; no statistical difference was found between lower and upper lobe tumors. The ITV(slow) was the smallest volume on average (142+/-38 cm(3)), followed by the ITV(hv) (160+/-40 cm(3)), the ITV(10ph) (161+/-41 cm(3)) and the ITV(fb) (250+/-63 cm(3)). Mean CTV doses were between 95% and 107% of the prescribed dose for nearly all patients and treatment plans. Analysis of the CTV coverage suggested that underdosage may occur when the CT(slow) is used and a geographic miss occurred using the CT(fb), due to uncorrect localization of the average tumor position.
The CT(hv) seems to be the optimal dataset for delineation, using an adequate anisotropic internal margin of (motion amplitude)/4.
确定基于呼吸相关CT（RCCT）的哪种内部靶区（ITV）定义方法能实现最佳肿瘤覆盖。
对41例肺癌患者进行了自由呼吸CT（CT(fb)）和RCCT扫描。对12例在任何方向运动>7 mm的患者进行了详细分析。RCCT扫描用于测量肿瘤运动，并重建10个时相的CT（CT(10ph)），其中包括半通气CT（CT(hv)）。通过对CT(10ph)进行平均，重建了慢速CT（CT(slow)）。基于这些扫描勾画ITV并制定治疗计划，对于ITV(hv)使用（运动幅度）/4的内部边界。将ITV的治疗计划投影到10个呼吸时相上。计算剂量并在10个时相上进行平均，以估计实际临床靶区（CTV）覆盖情况。
所有患者的三维运动平均为8.1±1.0 mm（1个标准差）；下叶和上叶肿瘤之间未发现统计学差异。平均而言，ITV(slow)体积最小（142±38 cm³），其次是ITV(hv)（160±40 cm³）、ITV(10ph)（161±41 cm³）和ITV(fb)（250±63 cm³）。几乎所有患者和治疗计划的平均CTV剂量在处方剂量的95%至107%之间。对CTV覆盖情况的分析表明，使用CT(slow)时可能发生剂量不足，而使用CT(fb)时由于平均肿瘤位置定位不正确会出现几何遗漏。
使用（运动幅度）/4的适当各向异性内部边界时，CT(hv)似乎是用于勾画的最佳数据集。
