在 PET 扫描中勾画肺肿瘤的最佳方法是什么？一种基于梯度的 NSCLC 数字 PET 体模多观察者验证方法。
What is the best way to contour lung tumors on PET scans? Multiobserver validation of a gradient-based method using a NSCLC digital PET phantom.
机构信息
Department of Radiation Oncology, Thomas Jefferson University Hospital, Philadelphia, PA 19107, USA.
出版信息
Int J Radiat Oncol Biol Phys. 2012 Mar 1;82(3):1164-71. doi: 10.1016/j.ijrobp.2010.12.055. Epub 2011 Apr 29.
PURPOSE
To evaluate the accuracy and consistency of a gradient-based positron emission tomography (PET) segmentation method, GRADIENT, compared with manual (MANUAL) and constant threshold (THRESHOLD) methods.
METHODS AND MATERIALS
Contouring accuracy was evaluated with sphere phantoms and clinically realistic Monte Carlo PET phantoms of the thorax. The sphere phantoms were 10-37 mm in diameter and were acquired at five institutions emulating clinical conditions. One institution also acquired a sphere phantom with multiple source-to-background ratios of 2:1, 5:1, 10:1, 20:1, and 70:1. One observer segmented (contoured) each sphere with GRADIENT and THRESHOLD from 25% to 50% at 5% increments. Subsequently, seven physicians segmented 31 lesions (7-264 mL) from 25 digital thorax phantoms using GRADIENT, THRESHOLD, and MANUAL.
RESULTS
For spheres <20 mm in diameter, GRADIENT was the most accurate with a mean absolute % error in diameter of 8.15% (10.2% SD) compared with 49.2% (51.1% SD) for 45% THRESHOLD (p < 0.005). For larger spheres, the methods were statistically equivalent. For varying source-to-background ratios, GRADIENT was the most accurate for spheres >20 mm (p < 0.065) and <20 mm (p < 0.015). For digital thorax phantoms, GRADIENT was the most accurate (p < 0.01), with a mean absolute % error in volume of 10.99% (11.9% SD), followed by 25% THRESHOLD at 17.5% (29.4% SD), and MANUAL at 19.5% (17.2% SD). GRADIENT had the least systematic bias, with a mean % error in volume of -0.05% (16.2% SD) compared with 25% THRESHOLD at -2.1% (34.2% SD) and MANUAL at -16.3% (20.2% SD; p value <0.01). Interobserver variability was reduced using GRADIENT compared with both 25% THRESHOLD and MANUAL (p value <0.01, Levene's test).
CONCLUSION
GRADIENT was the most accurate and consistent technique for target volume contouring. GRADIENT was also the most robust for varying imaging conditions. GRADIENT has the potential to play an important role for tumor delineation in radiation therapy planning and response assessment.
目的
评估基于梯度的正电子发射断层扫描（PET）分割方法（GRADIENT）与手动（MANUAL）和固定阈值（THRESHOLD）方法相比的准确性和一致性。
方法和材料
使用球体体模和临床逼真的胸部蒙特卡罗 PET 体模评估轮廓准确性。球体体模的直径为 10-37 毫米，在五个机构中采集，模拟临床条件。一个机构还采集了一个球体体模，具有 2:1、5:1、10:1、20:1 和 70:1 的源到背景比的多个。一位观察者使用 GRADIENT 和 THRESHOLD 从 25%到 50%以 5%的增量递增，对每个球体进行分割（轮廓）。随后，七位医生使用 GRADIENT、THRESHOLD 和 MANUAL 从 25 个数字胸部体模中分割了 31 个病变（7-264 毫升）。
结果
对于直径<20 毫米的球体，GRADIENT 的平均绝对%误差最小，为 8.15%（10.2%SD），而 45%THRESHOLD 的平均绝对%误差为 49.2%（51.1%SD）（p<0.005）。对于较大的球体，这些方法在统计学上是等效的。对于不同的源到背景比，GRADIENT 对于>20 毫米（p<0.065）和<20 毫米（p<0.015）的球体最准确。对于数字胸部体模，GRADIENT 的准确性最高（p<0.01），体积平均绝对%误差为 10.99%（11.9%SD），其次是 25%THRESHOLD 的 17.5%（29.4%SD），以及 MANUAL 的 19.5%（17.2%SD）。GRADIENT 的系统偏差最小，体积平均%误差为-0.05%（16.2%SD），而 25%THRESHOLD 的平均%误差为-2.1%（34.2%SD），MANUAL 的平均%误差为-16.3%（20.2%SD；p 值<0.01）。与 25%THRESHOLD 和 MANUAL 相比，GRADIENT 降低了观察者间的变异性（p 值<0.01，Levene 检验）。
结论
GRADIENT 是用于目标体积轮廓的最准确和一致的技术。GRADIENT 对于不同的成像条件也最稳健。GRADIENT 有可能在放射治疗计划和反应评估中的肿瘤描绘中发挥重要作用。
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