Department of Radiation Oncology, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark.
Int J Radiat Oncol Biol Phys. 2011 Aug 1;80(5):1573-80. doi: 10.1016/j.ijrobp.2010.10.036. Epub 2010 Dec 14.
Artifacts impacting the imaged tumor volume can be seen in conventional three-dimensional CT (3DCT) scans for planning of lung cancer radiotherapy but can be reduced with the use of respiration-correlated imaging, i.e., 4DCT or breathhold CT (BHCT) scans. The aim of this study was to compare delineated gross tumor volume (GTV) sizes in 3DCT, 4DCT, and BHCT scans of patients with lung tumors.
A total of 36 patients with 46 tumors referred for stereotactic radiotherapy of lung tumors were included. All patients underwent positron emission tomography (PET)/CT, 4DCT, and BHCT scans. GTVs in all CT scans of individual patients were delineated during one session by a single physician to minimize systematic delineation uncertainty. The GTV size from the BHCT was considered the closest to true tumor volume and was chosen as the reference. The reference GTV size was compared to GTV sizes in 3DCT, at midventilation (MidV), at end-inspiration (Insp), and at end-expiration (Exp) bins from the 4DCT scan.
The median BHCT GTV size was 4.9 cm(3) (0.1-53.3 cm(3)). Median deviation between 3DCT and BHCT GTV size was 0.3 cm(3) (-3.3 to 30.0 cm(3)), between MidV and BHCT size was 0.2 cm(3) (-5.7 to 19.7 cm(3)), between Insp and BHCT size was 0.3 cm(3) (-4.7 to 24.8 cm(3)), and between Exp and BHCT size was 0.3 cm(3) (-4.8 to 25.5 cm(3)). The 3DCT, MidV, Insp, and Exp median GTV sizes were all significantly larger than the BHCT median GTV size.
In the present study, the choice of CT method significantly influenced the delineated GTV size, on average, leading to an increase in GTV size compared to the reference BHCT. The uncertainty caused by artifacts is estimated to be in the same magnitude as delineation uncertainty and should be considered in the design of margins for radiotherapy.
在肺癌放射治疗计划的常规三维 CT（3DCT）扫描中，可以看到影响成像肿瘤体积的伪影，但可以使用呼吸相关成像（即 4DCT 或屏气 CT（BHCT）扫描）来减少这些伪影。本研究的目的是比较肺癌患者的 3DCT、4DCT 和 BHCT 扫描中勾画的大体肿瘤体积（GTV）大小。
共纳入 36 例 46 个肿瘤患者，这些患者均因肺癌行立体定向放疗。所有患者均行正电子发射断层扫描（PET）/CT、4DCT 和 BHCT 扫描。在一次会议中，由一位医生对每位患者的所有 CT 扫描进行 GTV 勾画，以尽量减少系统勾画不确定性。BHCT 的 GTV 大小被认为最接近真实肿瘤体积，被选为参考。参考 GTV 大小与 3DCT、4DCT 中的 midventilation（MidV）、end-inspiration（Insp）和 end-expiration（Exp）bins 的 GTV 大小进行比较。
BHCT GTV 大小的中位数为 4.9cm³（0.1-53.3cm³）。3DCT 与 BHCT GTV 大小之间的中位数偏差为 0.3cm³（-3.3 至 30.0cm³），MidV 与 BHCT 大小之间的中位数偏差为 0.2cm³（-5.7 至 19.7cm³），Insp 与 BHCT 大小之间的中位数偏差为 0.3cm³（-4.7 至 24.8cm³），Exp 与 BHCT 大小之间的中位数偏差为 0.3cm³（-4.8 至 25.5cm³）。3DCT、MidV、Insp 和 Exp 的 GTV 大小中位数均明显大于 BHCT 的 GTV 大小中位数。
在本研究中，CT 方法的选择显著影响了勾画的 GTV 大小，平均而言，与参考 BHCT 相比，GTV 大小会增加。由伪影引起的不确定性估计与勾画不确定性相当，在设计放射治疗的边缘时应考虑到这一点。
