Background/Objectives:To present the technical aspects of contrast-enhanced 4DCT (ce4DCT) simulation for abdominal SBRT.Methods:Twenty-two patients underwent two sequential 4DCT scans: one baseline and one contrast-enhanced with personalized delay time (tdelay) calculated to capture the tumor in the desired contrast phase, based on diagnostic triple-phase CT. The internal target volume (ITV) was delineated on ten contrast phases, and a panel of three experts qualitatively evaluated tumor visibility. Aortic HU values were measured to refine thetdelayfor subsequent patients. The commonly used approach of combining triple-phase CT with unenhanced 4DCT was simulated, and differences in target delineation were evaluated by volume, centroid shift, Dice and Jaccard indices, and mean distance agreement (MDA). The margins required to account for motion were calculated.Results:The ce4DCT acquisitions substantially improved tumor visibility over the entire breathing cycle in 20 patients, according to the experts’ unanimous evaluation. The median contrast peak time was 54.5 s, and the washout plateau was observed at 70.3 s, with mean peak and plateau HU values of 292 ± 59 and 169 ± 25. The volumes from the commonly used procedure (ITV2) were significantly smaller than the ce4DCT volumes (ITV1) (p= 0.045). The median centroid shift was 4.7 mm. The ITV1-ITV2 overlap was 69% (Dice index), 53% (Jaccard index), and 2.89 mm (MDA), with the liver volumes showing significantly lower indices compared to the pancreatic volumes (p≤ 0.011). The margins required to better encompass ITV1 were highly variable, with mean values ≥ 4 mm in all directions except for the left–right axis.Conclusions:The ce4DCT simulation was feasible, resulting in optimal tumor enhancement with minimal resource investment, while significantly mitigating uncertainties in SBRT planning by addressing poor visibility and respiratory motion. Triple-phase 3DCT with unenhanced 4DCT led to high variability in target delineation, making the isotropic margins ineffective.
背景/目的：介绍腹部立体定向放射治疗（SBRT）中对比增强四维计算机断层扫描（ce4DCT）模拟的技术细节。 方法：对22例患者进行两次连续的4DCT扫描：一次为基线扫描，另一次为对比增强扫描，其个性化延迟时间（tdelay）根据诊断性三期CT计算，旨在捕捉肿瘤在理想对比剂增强期。在十个对比增强期上勾画内靶区（ITV），并由三位专家组成的小组对肿瘤可见性进行定性评估。测量主动脉HU值以优化后续患者的tdelay。模拟了常用的三期CT联合非增强4DCT方法，并通过体积、质心偏移、Dice指数、Jaccard指数和平均距离一致性（MDA）评估靶区勾画的差异。计算了考虑运动所需的边界。 结果：根据专家一致评估，ce4DCT采集显著改善了20例患者在整个呼吸周期中的肿瘤可见性。对比剂峰值时间中位数为54.5秒，洗脱平台期出现在70.3秒，峰值和平台期HU平均值分别为292±59和169±25。常用方法获得的靶区体积（ITV2）显著小于ce4DCT体积（ITV1）（p=0.045）。质心偏移中位数为4.7毫米。ITV1与ITV2的重叠率为69%（Dice指数）、53%（Jaccard指数）和2.89毫米（MDA），其中肝脏体积的指数显著低于胰腺体积（p≤0.011）。为更好覆盖ITV1所需的边界变化较大，除左右轴外，各方向平均值均≥4毫米。 结论：ce4DCT模拟具有可行性，能以最小资源投入实现最佳肿瘤增强，同时通过解决可见性差和呼吸运动问题，显著降低SBRT计划中的不确定性。三期3DCT联合非增强4DCT导致靶区勾画变异性高，使得各向同性边界无效。
Synchronized Contrast-Enhanced 4DCT Simulation for Target Volume Delineation in Abdominal SBRT
肿瘤(癌症)患者之家