Tumor delineation using PET in head and neck cancers: Threshold contouring and lesion volumes
Tumor delineation using PET in head and neck cancers: Threshold contouring and lesion volumes
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DOI：
10.1118/1.2361076
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发表时间：
2006-11-01
期刊：
影响因子：
3.8
通讯作者：
Phillips, Mark
中科院分区：
文献类型：
--
作者：
Ford, Eric C.;Kinahan, Paul E.;Phillips, Mark
使用正电子发射断层扫描（PET）的肿瘤边界描绘是用于放射治疗应用的有前景的工具。在这项研究中，我们量化肿瘤边界划定的不确定性作为一个功能的重建方法，平滑，和病变大小的头颈部癌症患者使用FDG-PET图像和放射治疗计划的剂量影响进行评估。使用GE Advance PET扫描仪采集8例患者的FDG-PET图像。此外，还对一个直径为20 cm的圆柱体模进行了成像，该体模含有6个体积为1.2至26.5 cm（3）的填充FDG的球体。采用OSEM和FBP算法对PET发射扫描图像进行重建，并分别采用不同的平滑参数。使用自动轮廓功能（设置为逐渐升高的阈值轮廓水平）描绘基于PET的肿瘤区域，并计算所得体积。基于CT的肿瘤体积也由医生在共配准的PET/CT患者图像上描绘轮廓。测量返回100%实际体积I-v100的阈值轮廓水平的强度值。我们为一例头颈部患者制定了调强放射治疗（IMRT）计划，对基于CT的大体病变进行66戈伊治疗，对有风险的淋巴结区域进行54戈伊治疗，然后对基于FDG-PET的肿瘤进行增强治疗。基于PET的肿瘤体积是所有患者和体模数据集的阈值轮廓水平的敏感函数。阈值轮廓水平的5%变化可以转化为体积的200%增加。体模数据表明，I-v100可以设置为最大测量摄取的分数f。圆柱形水模中的分数阈值范围为0.23至0.51。分数阈值和阈值-体积曲线均取决于病变大小，小于约5 cm 3的病变显示出更明显的灵敏度和更大的分数阈值。阈值-体积曲线和分数阈值还取决于重建算法和平滑滤波器，其中更多的平滑需要更高的分数阈值轮廓水平。阈值轮廓水平影响肿瘤大小，因此影响IMRT可实现的最终增强剂量。在示例性头部和颈部IMRT计划中，对于42%与55%轮廓阈值水平，计划靶体积的D95从7770 cGy降低到7230 cGy。基于PET的肿瘤体积受到阈值水平选择的强烈影响。这可能具有显著的剂量测定影响。适当的阈值水平取决于病变大小和图像重建参数。当使用PET轮廓和/或体积信息进行放射治疗应用时，应仔细考虑这些影响。(c)2006年美国医学物理学家协会。
Tumor boundary delineation using positron emission tomography (PET) is a promising tool for radiation therapy applications. In this study we quantify the uncertainties in tumor boundary delineation as a function of the reconstruction method, smoothing, and lesion size in head and neck cancer patients using FDG-PET images and evaluate the dosimetric impact on radiotherapy plans. FDG-PET images were acquired for eight patients with a GE Advance PET scanner. In addition, a 20 cm diameter cylindrical phantom with six FDG-filled spheres with volumes of 1.2 to 26.5 cm(3) was imaged. PET emission scans were reconstructed with the OSEM and FBP algorithms with different smoothing parameters. PET-based tumor regions were delineated using an automatic contouring function set at progressively higher threshold contour levels and the resulting volumes were calculated. CT-based tumor volumes were also contoured by a physician on coregistered PET/CT patient images. The intensity value of the threshold contour level that returns 100% of the actual volume, I-v100, was measured. We generated intensity-modulated radiotherapy (IMRT) plans for an example head and neck patient, treating 66 Gy to CT-based gross disease and 54 Gy to nodal regions at risk, followed by a boost to the FDG-PET-based tumor. The volumes of PET-based tumors are a sensitive function of threshold contour level for all patients and phantom datasets. A 5% change in threshold contour level can translate into a 200% increase in volume. Phantom data indicate that I-v100 can be set as a fraction, f, of the maximum measured uptake. Fractional threshold values in the cylindrical water phantom range from 0.23 to 0.51. Both the fractional threshold and the threshold-volume curve are dependent on lesion size, with lesions smaller than approximately 5 cm3 displaying a more pronounced sensitivity and larger fractional threshold values. The threshold-volume curves and fractional threshold values also depend on the reconstruction algorithm and smoothing filter with more smoothing requiring a higher fractional threshold contour level. The threshold contour level affects the tumor size, and therefore the ultimate boost dose that is achievable with IMRT. In an example head and neck IMRT plan, the D95 of the planning target volume decreased from 7770 to 7230 cGy for 42% vs 55% contour threshold levels. PET-based tumor volumes are strongly affected by the choice of threshold level. This can have a significant dosimetric impact. The appropriate threshold level depends on lesion size and image reconstruction parameters. These effects should be carefully considered when using PET contour and/or volume information for radiotherapy applications. (c) 2006 American Association of Physicists in Medicine.