FDG PET-CT与MRI在鼻咽癌原发灶靶区勾画中的对比研究

目的 对比研究FDG PET-CT不同勾画方法间及与MRI显示鼻咽原发灶靶区差异,探讨FDG PET-CT勾画鼻咽原发灶大体肿瘤体积(GTV)生物靶区的可行性。方法 50例初治鼻咽癌患者治疗前均行FDG PET-CT和MRI检查,先在MRI图像上勾画GTV得到GTV-MRI,然后在FDG PET-CT上分别用目测法或不同阈值法(30%、40%、50%SUV_max)勾画GTV得到GTV-PET_vis、GTV-PET₃₀、GTV-PET₄₀、GTV-PET₅₀。采用Wilcoxon检验GTV-PET不同方法间和GTV-MRI差异,以及不同T分期中不同勾画方法间差异。结果 全组GTV-MRI、GTV-PET_vis、GTV-PET₃₀、GTV-PET₄₀、GTV-PET₅₀分别为27.8、22.2、22.7、14.4、9.0 cm³,除GTV-PET_vis与GTV-PET₃₀间(Z=－0.05,P=0.958)以及T_1~2期(25例) GTV-MRI与GTV-PET_vis和GTV-PET₃₀相似外(Z=－0.93、－0.93,P=0.353、0.353),其余均不同(Z=－5.74~－2.09,P=0.000~0.037)。结论 应用FDG PET-CT不同方法勾画的GTV-PET均max为阈值自动勾画鼻咽原发灶GTV可实现生物代谢肿瘤体积范围勾画。     

基于PET-CT的SUV值与基于4DCT的EE时相勾画胸段食管癌GTV相关性分析

目的 探讨基于PET-CT图像SUV阈值≥2.0及20%SUV_max与基于4DCT的EE时相图像勾画胸段食管癌原发肿瘤GTV相关性因素。方法 22例胸段食管癌患者序贯完成3DCT、4DCT、FDG PET-CT 胸部定位扫描。基于4DCT的EE时相图像勾画GTV_50%。基于SUV≥2.0、20%SUV_max分别在PET图像上勾画IGTV_PET并分别命名为IGTV_PET2.0、IGTV_PET20%。获得GTV_50%最大横径、GTV_50%大小、上下方向位移、三维运动矢量和SUV_max。结果 IGTV_PET2.0、IGTV_PET20%与GTV_50%间体积比与GTV_50%最大横径、GTV_50%大小、上下方向位移、三维运动矢量均无相关性(P=0.055~0.932);IGTV_PET2.0、IGTV_PET20%与GTV_50%间CI与GTV_50%最大横径、GTV_50%大小、上下方向位移、三维运动矢量均有相关性(P=0.005~0.033);IGTV_PET20%与GTV_50%间体积比、CI与SUV_max均有相关性(P=0.001、0.016)。结论 基于PET-CT图像构建的IGTV并不能客观真实反映肿瘤空间位置变化及运动信息,而且单一数值的SUV阈值选取也是不可靠的。构建食管癌原发肿瘤靶区时应依据4DCT所构建IGTV纠正PET-CT所构建IGTV边界及其位置。     

勾画标准培训对乳腺癌保乳术后放疗靶区勾画的作用

目的 探讨勾画标准培训对保乳术后瘤床靶区和全乳靶区勾画的影响。方法 选择 12例保乳术后患者,5位勾画者先对每位患者依据金属夹勾画瘤床靶区(GTV₁)、依据术腔血清肿勾画瘤床靶区(GTV₂)、勾画全乳靶区(CTV),随后参照勾画标准重复勾画GTV₁、GTV₂、CTV,比较5位勾画者间差异和参照标准前后差异并行单因素方差分析或配对t检验。结果 5位勾画者参照标准前的GTV₁、GTV₂、CTV均不同(F=11.16、7.54、3.78,P=0.000、0.000、0.009),参照勾画标准后的GTV₁、GTV₂不同(F=4.78、4.24,P=0.002、0.005),但CTV相似(F=1.52,P=0.209)。参照勾画标准前后的GTV₁、GTV₂、CTV变异系数不同(t=3.14、2.81、2.70,P=0.009、0.017、0.021),匹配指数也不同(F=16.08、8.61、8.48,P=0.000、0.000、0.000)。结论 乳腺癌靶区勾画标准的制订可降低勾画者之间差异,尤其是对全乳靶区的勾画更为明显。     

4DCT、PET-CT与MRI勾画胸段食管癌大体肿瘤体积比较研究

目的 比较基于4DCT呼气末时相、¹⁸F-FDG PET-CT及T2加权(T2W) MRI所勾画胸段食管癌大体肿瘤体积(GTV)、位置及长度差异,探讨食管癌原发肿瘤GTV勾画时PET-CT与MRI图像结合的必要性。方法 26例拟行同步放化疗的胸段食管癌患者序贯完成增强3DCT、增强4DCT、PET-CT、增强MRI胸部定位扫描,基于3DCT图像形变配准。分别基于3DCT、4DCT的呼气末时相、PET-CT SUV 2.5、T2W-MRI和DWI图像勾画GTV获得GTVCT、GTV50%、GTVPET2.5、GTVMRI和GTVDWI。结果 GTVPET2.5大于GTV50%(P<0.001)和GTVMRI (P=0.008),而GTVMRI与GTV50%接近(P=0.439)。GTVMRI与GTV50%、GTVCT的适形指数(CI)大于GTVPET2.5与GTV50%、GTVCT的(P=0.004、P=0.039),GTVMRI与GTVPET2.5的CI明显小于GTVMRI、GTVPET2.5与GTV50%、GTVCT的(P=0.000~0.021)。镜检长度与GTVPET、GTVDWI长度相近(P>0.05),且GTVPET2.5与GTVDWI长度接近(P=0.072)。结论 基于PET-CT SUV2.5与呼吸门控状态下T2W-MRI所勾画食管癌GTV和空间位置差异明显,PET-CT与MRI结合进行食管癌靶区勾画的必要性尚需探讨,但MRI-DWI可以代替PET-CT帮助基于CT图像勾画GTV时上下界的确定。     

食管鳞癌18F-FDGPET图像异质性及其对放疗靶区勾画影响分析

目的:探讨18氟-氟代脱氧葡萄糖(18 F-fluorodeoxyglucose,18 F-FDG)PET图像异质性对食管癌放疗靶区勾画的影响。方法:28例经病理确诊为食管鳞癌初治患者治疗前行18 F-FDG PET/CT扫描。通过视觉法和三维图像纹理参数(能量和熵)分析获得FDG摄取异质性。CT图像上勾画出肿瘤靶区(GTVCT)。PET图像上肿瘤靶区采用自动勾画法,分别采用40%SUVmax阈值勾画(GTVPET40%)和标准化摄取值(standardized uptake value,SUV)=2.5绝对值阈值勾画(GTVPET2.5)。分析FDG摄取异质性与不同方法勾画肿瘤靶区体积差值间的相关性。结果:3种方法获得的肿瘤靶区差异有统计学意义,GTVCT为(45.00±43.40)cm3明显大于GTVPET40%的(20.42±16.12)cm3和GTVPET2.5(35.88±36.33)cm3,其中GTVCT与GTVPET40%差异有统计学意义,t=4.34,P=0.00;GTVCT与GTVPET2.5差异有统计学意义,t=4.80,P=0.00;GTVPET40%与GTVPET2.5:差异有统计学意义,t=3.59,P=0.00。肿瘤摄取异质性与传统代谢参数SUVmax和SUVmean及靶区体积间存在相关性,|r|=0.41,P≤0.03。GTVPET40%和GTVPET2.5之间的差异与熵呈正相关,r=0.41,P=0.029;与能量负相关,r=-0.39,P=0.04。视觉评分与GTVPET40%和GTVPET2.5之间的百分率差值也存在相关性,r=0.59,P=0.001。结论:PET图像上靶区勾画受到FDG摄取异质性的影响,特别是异质性较大的肿瘤。PET精确靶区勾画方法需要考虑到肿瘤异质性的影响。     

4DCT MIP图像与FDG PET-CT不同SUV阈值勾画NSCLC IGTV的比较研究

目的 比较NSCLC基于4DCT MIP图像与FDG PET-CT不同SUV阈值勾画所得靶区间体积及位置差异。方法 10例NSCLC患者序贯完成胸部3DCT、4DCT增强扫描并基于相同体位固定方式及定位参数行FDG PET-CT扫描。在4DCT MIP图像上勾画IGTV_MIP,分别基于PET图像9种不同阈值自动勾画及手动勾画10种IGTV_PET(IGTV_PET2.0、IGTV_PET2.5、IGTV_PET3.0、IGTV_PET3.5、IGTV_PET20%、IGTV_PET25%、IGTV_PET30%、IGTV_PET35%、IGTV_PET40%、IGTV_PETman)。配对t检验比较IGTV_PET与IGTV_MIP靶区位置、体积、包含度及匹配指数差异。 结果 10种 IGTV_PET与IGTV_MIP 中心点坐标仅在z轴差异有统计学意义(P=0.014~ 0.044)。IGTV_{PET2.0 及IGTVPET20% 与IGTVMIP体积大小最接近,体积比分别为1.02和1.06(P= 0.806)。IGTVPET2.0与IGTVMIP 及IGTVPET25%与IGTVMIP 的匹配指数最高,分别为0.46和0.45(P=0.603 )。IGTVMIP 对IGTV PET20% 及IGTVPET2.0 的包含度最高,分别为0.61 和0.61 (P=0.963 )。 结论 基于PET SUV值2.0及最大值的20%勾画的IGTVPET 与基于4DCT MIP图像构建的IGTVMIP 体积大小最接近、空间错位也相对较少,但就空间位置而言,两者均不能替代IGTVMIP 。基于PETCT勾画NSCLC原发肿瘤靶区时,选择合适的SUV值的同时要参照4DCT进行靶区位置校正。}     

4DCT全时相与PET-CT不同SUV阈值勾画胸段食管癌IGTV的比较研究

目的 比较基于4DCT 10个时相与基于PET-CT不同SUV值勾画的IGTV的大小和CI、DI值。方法 15例胸段食管癌患者序贯完成3DCT、4DCT、FDG PET-CT 胸部定位扫描。在4DCT各时相图像上分别勾画IGTV并融合获得IGTV₁₀。基于不同SUV值(≥2.0、2.5、3.0、3.5)及 SUV_max的不同百分比(≥20%、25%、30%、35%、40%)分别在PET图像上勾画IGTV_PET2.0、IGTV_PET2.5、IGTV_PET3.0、IGTV_PET3.5、IGTV_PET20%、IGTV_PET25%、IGTV_PET30%、IGTV_PET35%、IGTV_PET40%。两两比较采用配对t检验,靶区中心间距与CI、DI值相关性采用Pearson法分析。结果 IGTV_PET2.5、IGTV_PET20%与IGTV₁₀体积相近(体积比0.92、1.08,P=0.985、0.886),IGTV_PET2.0、IGTV_PET2.5、IGTV_PET20%与IGTV₁₀间CI值也相近(0.53、0.52、0.53,P=0.432,1.00,0.414),但三者均明显大于其他6个IGTV_PET与IGTV₁₀间的CI值(0.33~0.50,P=0.000~0.047)。IGTV_PET2.5对IGTV₁₀的DI (0.74)与IGTV_PET20%对IGTV₁₀的DI (0.72)也相近(P=0.542),IGTV₁₀对IGTV_PET2.5的DI (0.67)与IGTV₁₀对IGTV_PET20%的DI也相近(P=0.539)。结论 SUV阈值为2.5及最大值的20%时,基于PET-CT勾画的IGTV_PET与基于4DCT 10个时相构建的IGTV₁₀体积大小接近且空间错位程度相对较小。     

FDG PET-CT靶区勾画方法在食管癌中的比较及病理对照研究

目的 比较3种FDG PET-CT勾画方法在食管癌GTV勾画中的差别,寻找GTV勾画的最佳SUV阈值,探讨FDG PET-CT在淋巴结检测中的作用.方法接受根治性食管癌切除术患者33例人组,除常规检查外均行PET-CT扫描.采用肉眼法、SUV 2.5和40%SUVmax3种方法勾画肿瘤GTV,测量其纵轴长度后分别记为Lvis、L2.5和L40%.术后测量病理标本的长度,记为Lpath,并与PETCT测量的长度比较.术后对PET重新阅片,采用不同的SUVmax百分数勾画GTV,当长度与Lpath一致时,该值为最佳SUV阈值.根据术后病理验证PET-CT对食管癌淋巴结转移诊断结果.结果病理长度(Lpath)为(5.52±2.00)cm,21个肿瘤长度≥5 cm,12个肿瘤《5 cm.Lvis、L2.5和L40%值分别为(5.16±1.97)、(5.55±1.81)和(4.42±1.60)cnl,与Lpath的相关系数分别为0.817、0.877和0.863.L40%显著小于Lpath(P《0.001).在所有肿瘤中最佳SUV阈值为24.30%±10.96%,在长度≥5 cm的肿瘤中为21.14%±9.06%,《5 cm的为29.83%±12.15%.最佳SUV阈值与IMB比值和Lpath的相关系数分别为-0.730、-0.515.对淋巴结检测的敏感性、特异性和准确性分别为77.8%、95.2%和92.3%.结论不同方法勾画的肿瘤长度不同.L2.5勾画的结果与病理长度一致性最好.最佳SUV阈值与L/B比值和肿瘤长度呈负相关.FDG PET-CT能够较准确地检测转移淋巴结.     

胰腺癌平扫或强化氟脱氧葡萄糖PET-CT图像靶区勾画研究

目的 探讨平扫或强化氟脱氧葡萄糖(FDG) PET-CT图像在胰腺癌靶区勾画中的作用。方法 回顾分析本院 2008—2009年间 21例局部晚期不可切除及术后复发胰腺癌患者资料,以相同固定体位分别行平扫CT、PET,其中 11例之后行强化CT。将扫描数据输入治疗计划系统,行平扫或强化CT、PET图像融合,分别依据强化CT、平扫CT、平扫PET及平扫或强化PET-CT融合图像勾画大体肿瘤体积(GTV),并用配对或成组t检验比较不同图像GTV大小。结果 21例患者平扫 GTV_CT、平扫 GTV_PET、平扫或强化 GTV_PET-CT平均值分别为76.9、47.0、44.5 cm³,平扫 GTV_PET-CT平均体积明显小于平扫GTV_CT (z=－3.91,P=0.000)。11例强化 GTV_CT、强化 GTV_PET、强化 GTV_PET-CT平均体积分别为64.1、45.1、49.3 cm³,强化 GTV_PET-CT平均体积明显小于强化GTV_CT (z=－2.13,P=0.033),强化 GTV_PET-CT平均体积与平扫 GTV_PET-CT相似(z=－0.80,P=0.424)。结论 PET和强化或平扫CT的融合图像能提高不可切除胰腺癌靶区勾画准确性,有望降低放疗不良反应。     

功能影像在食管癌精确放疗中的应用价值研究

目的 探讨PET-CT在食管癌临床分期诊断和三维适形放疗靶区勾画及治疗计划制定中的应用价值.方法 2007-2008年经病理证实的食管癌患者20例人组,其中2例接受手术治疗,18例行三维适形放疗.患者疗前行PET-CT模拟定位,比较食管镜、食管钡餐造影、CT、PET-CT_(SUV2.5)、PET-CT_(40%SUVmax)图像上的病变长度及最大横径,观察CT与PET-CT对临床分期诊断的差异.依据CT、PET-CT_(SUV2.5)和PET-CT<40%SUVmax>勾画靶区并制定治疗计划,评价3套计划受量情况.结果 食管镜、食管钡餐造影、CT、PET-CTS_(SUV2.5、PET-CT_(40%SUVmax))所示病变长度分别为4.93、5.06、6.67、5.89、4.84 cm,CT、PET-CT_(SUV2.5)、PET-CT_(40%SUV)所示病变最大横径分别为4.05、3.38、2.95 cm.CT图像诊断31个淋巴结转移,PET-CT图像诊断21个淋巴结转移,共同诊断14个,17个淋巴结CT诊断阳性而PET-CT为阴性,7个淋巴结CT诊断阴性而PET-CT为高代谢.5例患者经PET-CT模拟定位后M分期由Mn期改为_1期,1例经PET-CT模拟定位后由M_0期改为M_1期,1例CT和PET-CT M分期一致.依据CT和PET-CT_(SUV2.5)勾画的GTV基本相等2例,CTV_(CT)GT_(SUV2.5)者13例,GTV_(SUV2.5),相似文献   

Comparison of five segmentation tools for 18F-fluoro-deoxy-glucose-positron emission tomography-based target volume definition in head and neck cancer

PURPOSE: Target-volume delineation for radiation treatment to the head and neck area traditionally is based on physical examination, computed tomography (CT), and magnetic resonance imaging. Additional molecular imaging with (18)F-fluoro-deoxy-glucose (FDG)-positron emission tomography (PET) may improve definition of the gross tumor volume (GTV). In this study, five methods for tumor delineation on FDG-PET are compared with CT-based delineation. METHODS AND MATERIALS: Seventy-eight patients with Stages II-IV squamous cell carcinoma of the head and neck area underwent coregistered CT and FDG-PET. The primary tumor was delineated on CT, and five PET-based GTVs were obtained: visual interpretation, applying an isocontour of a standardized uptake value of 2.5, using a fixed threshold of 40% and 50% of the maximum signal intensity, and applying an adaptive threshold based on the signal-to-background ratio. Absolute GTV volumes were compared, and overlap analyses were performed. RESULTS: The GTV method of applying an isocontour of a standardized uptake value of 2.5 failed to provide successful delineation in 45% of cases. For the other PET delineation methods, volume and shape of the GTV were influenced heavily by the choice of segmentation tool. On average, all threshold-based PET-GTVs were smaller than on CT. Nevertheless, PET frequently detected significant tumor extension outside the GTV delineated on CT (15-34% of PET volume). CONCLUSIONS: The choice of segmentation tool for target-volume definition of head and neck cancer based on FDG-PET images is not trivial because it influences both volume and shape of the resulting GTV. With adequate delineation, PET may add significantly to CT- and physical examination-based GTV definition.     

Correlation of PET standard uptake value and CT window-level thresholds for target delineation in CT-based radiation treatment planning

PURPOSE: To develop standardized correlates of [18F]fluoro-2-deoxy-d-glucose positron emission tomography (FDG-PET) standard uptake value (SUV) to computed tomography (CT)-based window and levels. METHODS AND MATERIALS: Nineteen patients with non-small-cell lung cancer who underwent imaging with positron emission tomography (PET) and CT were selected. A method of standardizing SUV within CT planning software was developed. A scale factor, determined by a sensitivity calibration of the PET scanner, converts voxel counts to activity per gram in tissue, allowing SUVs to be correlated to CT window and levels. A method of limiting interobserver variations was devised to enhance "edges" of regions of interest based on SUV thresholds. The difference in gross tumor volumes (GTVs) based on CT, PET SUV >or= 2.5, and regions of 40% maximum SUV were analyzed. RESULTS: The mean SUV was 9.3. Mean GTV volumes were 253 cc for CT, 221 cc for SUV >or= 2.5, and 97 cc for SUV40%Max. Average volume difference was -259% between >or=2.5 SUV and CT and -162% between SUV40%Max and CT. Percent difference between GTV >or= 2.5 SUV and SUV40%Max remained constant beyond SUV > 7. For SUVs 4-6, best correlation among SUV thresholds occurred at volumes near 90 cc. Mean percent change from GTVs contoured according to CT (GTV CT) was -260% for GTV2.5 and -162% for GTV40%Max. Using the SUV40%Max threshold resulted in a significant alteration of volume in 98% of patients, while the SUV2.5 threshold resulted in an alteration of volume in 58% of patients. CONCLUSIONS: Our method of correlating SUV to W/L thresholds permits accurate displaying of SUV in coregistered PET/CT studies. The optimal SUV thresholds to contour GTV depend on maximum tumor SUV and volume. Best correlation occurs with SUVs >6 and small volumes <100 cc. At SUVs >7, differences between the SUV threshold filters remain constant. Because of variability in volumes obtained by using SUV40%Max, we recommend using SUV >or= 2.5 for radiotherapy planning in non-small-cell lung cancer.     

18F-FDG PET/CT在子宫颈癌放疗靶区勾画中的价值

目的 探讨18F-FDG PET/CT在子宫颈癌放疗靶区勾画中的价值.方法 收集2015年3月至2016年10月经病理学检查证实为子宫颈鳞癌Ⅲb期患者33例,由3名放疗医师分别基于单纯CT和PET/CT融合图像勾画原发病灶大体肿瘤靶区体积(gross target volume,GTV),比较不同医师所勾画靶区的差异.结果 3名医师在单纯CT和PET/CT融合图像下定义的GTV比较差异均有统计学意义(P＜0.001).不同医师定义GTVCr差异有统计学意义(F=4.28,P＜0.001),但GTVPERT-CT差异无统计学意义(F=0.21,P=0.81).3位医师应用PET/CT图像勾画的肿瘤靶区体积变异减小(7.75 cm3 vs 24.50 cm3).结论 PET/CT融合图像可以提高靶区勾画的准确性.     

Automated functional image-guided radiation treatment planning for rectal cancer

PURPOSE: Computer tomography-based (CT-based) tumor-volume definition is time consuming and is subject to clinical interpretation. CT is not accessible for standardized algorithms for the purpose of treatment-volume planning. We have evaluated the accuracy of target-volume definition based on the positron emission tomography (PET) data from an integrated PET/CT system with 2-[(18)F]fluoro-2-deoxy-D-glucose (FDG) for standardized target-volume delineation. MATERIALS AND METHODS: Eleven patients with rectal cancer who were undergoing preoperative radiation therapy (RT) were studied. A standardized region-growing algorithm was tested to replace the CT-derived gross tumor volume by the PET-derived gross tumor volume (PET-GTV) or the biologic target volume (BTV). A software tool was developed to automatically delineate the appropriate tumor volume as defined by the FDG signal, the PET-GTV, and the planning target volume (PTV). The PET-derived volumes were compared with the target volumes from CT. RESULTS: The BTV defined for appropriate GTV assessment was set at a single peak threshold of 40% of the signal of interest. Immediate treatment volume definition based on the choice of a single-tumor volume-derived PET-voxel resulted in a tumor volume that strongly correlated with the CT-derived GTV (r(2) = 0.84; p < 0.01) and the volume as assessed on subsequent anatomic-pathologic analysis (r(2) = 0.77; p < 0.01). In providing sufficient extension margins from the CT-derived GTV and the PET-derived GTV, to PTV, respectively, the correlation of the CT-derived and PET-derived PTV was sufficiently accurate for PTV definition for external-beam therapy (r(2) = 0.96; p < 0.01). CONCLUSION: Automated segmentation of the PET signal from rectal cancer may allow immediate and sufficiently accurate definition of a preliminary working PTV for preoperative RT. If required, correction for anatomic precision and geometric resolution may be applied in a second step. Computed PET-based target-volume definition could be useful for the definition of standardized simultaneous internal-boost volumes for intensity-modulated radiation therapy (IMRT) based on biologic target volumes.     

PET-CT用于评价食管鳞癌放疗中18F-FDG高摄取区域的空间动态变化的前瞻性研究

背景与目的：放疗为食管癌重要的治疗方式之一,但疗效并不理想。目前认为肿瘤在PET-CT上高摄取的区域可能与放射抵抗有关。本文通过观察放疗前和放疗中两次PET-CT所显示的食管原发病灶18F-FDG高摄取区域的空间位置关系,从而推测依据放疗前的PET图像上所显示的食管癌原发灶高18F-FDG摄取的信息进行区域选择性加量放疗的可行性。方法：入组2011—2013年在复旦大学附属肿瘤医院放疗科接受同步放化疗治疗的初治食管鳞癌患者。所有患者在放疗前和放疗40 Gy时(第2次同步化疗前)分别行18F-FDG PET-CT扫描。在第1次PET图像上原发灶勾画首先以标准摄取值(standard uptake value,SUV)=2.5、5和40%~70%SUVmax-pre为阈值在PET图像上自动勾画得到大体肿瘤体积(gross tumor volume,GTV)2.5pre、GTV5pre、GTV40%pre、GTV50%pre、GTV60%pre和GTV70%pre。在第2次PET图像上,以SUV=2.5和70%~90%SUVmax-dur为阈值勾画得到GTV2.5dur、GTV70%dur、GTV80%dur和GTV90%dur。计算两次PET图像上以阈值自动勾画的区域的空间交集分数(overlap fraction,OF),即两个感兴趣区(region of interest,ROI)的交集的体积与两个ROI相对较小的体积的比值。结果：共入组22例患者。所有患者的原发灶SUVmax、SUVmean均有显著下降(P=0.003和P<0.0001)。残留高摄取区域与治疗前GTV50%pre的OF达到70%以上,其中热点区域GTV90%dur完全处于原发灶的高摄取区域内,OF达到100%。以不同阈值勾画的体积有很大差异,而放疗前和放疗中的食管癌原发灶高代谢区域尽管体积变化很大,但空间位置保持相对的稳定。结论：放疗中食管鳞癌原发灶的SUV显著下降,但食管癌原发灶残留的18F-FDG高摄取区域仍然较稳定的落在治疗前原发灶GTV及治疗前PET上所显示的18F-FDG高摄取区域内,提示依据治疗前PET图像来选择性对食管癌原发病灶的部分区域进行局部加量放疗是可行的。     

Impact of integrated PET/CT on variability of target volume delineation in rectal cancer

Several studies have demonstrated substantial variability among individual radiation oncologists in defining target volumes using computed tomography (CT). The objective of this study was to determine the impact of combined positron emission tomography and computed tomography (PET/CT) on inter-observer variability of target volume delineation in rectal cancer. We also compared the relative concordance of two PET imaging tracers, 18F-fluorodeoxyglucose (FDG) and 18F-fluorodeoxythymidine (FLT), against conventional computed tomography (CT). Six consecutive patients with locally advanced rectal cancer were enrolled onto an institutional protocol involving preoperative chemoradiotherapy and correlative studies including FDG- and FLT-PET scans acquired in the treatment position. Using these image data sets, four radiation oncologists independently delineated primary and nodal gross tumor volumes (GTVp and GTVn) for a hypothetical boost treatment. Contours were first defined based on CT alone with observers blinded to the PET images, then based on combined PET/CT. An inter-observer similarity index (SI), ranging from a value of 0 for complete disagreement to 1 for complete agreement of contoured voxels, was calculated for each set of volumes. For primary gross tumor volume (GTVp), the difference in estimated SI between CT and FDG was modest (CT SI = 0.77 vs. FDG SI = 0.81), but statistically significant (p = 0.013). The SI difference between CT and FLT for GTVp was also slight (FLT SI = 0.80) and marginally non-significant (p < 0.082). For nodal gross tumor volume, (GTVn), SI was significantly lower for CT based volumes with an estimated SI of 0.22 compared to an estimated SI of 0.70 for FDG-PET/CT (p < 0.0001) and an estimated SI of 0.70 for FLT-PET/CT (p < 0.0001). Boost target volumes in rectal cancer based on combined PET/CT results in lower inter-observer variability compared with CT alone, particularly for nodal disease. The use of FDG and FLT did not appear to be different from this perspective.     

The contribution of integrated PET/CT to the evolving definition of treatment volumes in radiation treatment planning in lung cancer

PURPOSE: Positron emission tomography (PET) with the glucose analog [18F]fluro-2-deoxy-D-glucose (FDG) has been accepted as a valuable tool for the staging of lung cancer, but the use of PET/CT in radiation treatment planning is still not yet clearly defined. By the use of (PET/computed tomography (CT) images in treatment planning, we were able to define a new gross treatment volume using anatomic biologic contour (ABC), delineated directly on PET/CT images. We prospectively addressed three issues in this study: (1) How to contour treatment volumes on PET/CT images, (2) Assessment of the degree of correlation between CT-based gross tumor volume/planning target volume (GTV/PTV) (GTV-CT and PTV-CT) and the corresponding PET/CT-based ABC treatment volumes (GTV-ABC and PTV-ABC), (3) Magnitude of interobserver (radiation oncologist planner) variability in the delineation of ABC treatment volumes (using our contouring method). METHODS AND MATERIALS: Nineteen patients with Stages II-IIIB non-small-cell lung cancer were planned for radiation treatments using a fully integrated PET/CT device. Median patient age was 74 years (range: 52-82 years), and median Karnofsky performance status was 70. Thermoplastic or vacuum-molded immobilization devices required for conformal radiation therapy were custom fabricated for the patient before the injection of [18]f-FDG. Integrated, coregistered PET/CT images were obtained and transferred to the radiation planning workstation (Xeleris). While the PET data remained obscured, a CT-based gross tumor volume (GTV-CT) was delineated by two independent observers. The PTV was obtained by adding a 1.5-cm margin around the GTV. The same volumes were recontoured using PET/CT data and termed GTV-ABC and PTV-ABC, correspondingly. RESULTS: We observed a distinct "halo" around areas of maximal standardized uptake value (SUV). The halo was identified by its distinct color at the periphery of all areas of maximal SUV uptake, independent of PET/CT gain ratio; the halo had an SUV of 2 +/- 0.4 and thickness of 2 mm +/- 0.5 mm. Whereas the center of our contoured treatment volume expressed the maximum SUV level, a steady decline of SUV was noted peripherally until SUV levels of 2 +/- 0.4 were reached at the peripheral edge of our contoured volume, coinciding with the observed halo region. This halo was always included in the contoured GTV-ABC. Because of the contribution of PET/CT to treatment planning, a clinically significant (> or =25%) treatment volume modification was observed between the GTV-CT and GTV-ABC in 10/19 (52%) cases, 5 of which resulted in an increase in GTV-ABC volume vs. GTV-CT. The modification of GTV between CT-based and PET/CT-based treatment planning resulted in an alteration of PTV exceeding 20% in 8 out of 19 patients (42%). Interobserver GTV variability decreased from a mean volume difference of 28.3 cm3 (in CT-based planning) to 9.12 cm3 (in PET/CT-based planning) with a respective decrease in standard deviation (SD) from 20.99 to 6.47. Interobserver PTV variability also decreased from 69.8 cm3 (SD +/- 82.76) in CT-based planning to 23.9 cm3 (SD +/- 15.31) with the use of PET/CT in planning. The concordance in treatment planning between observers was increased by the use of PET/CT; 16 (84%) had < or =10% difference from mean of GTVs using PET/CT compared to 7 cases (37%) using CT alone (p = 0.0035). Conclusion: Position emission tomography/CT-based radiation treatment planning is a useful tool resulting in modification of GTV in 52% and improvement of interobserver variability up to 84%. The use of PET/CT-based ABC can potentially replace the use of GTV. The anatomic biologic halo can be used for delineation of volumes.     

Variability of gross tumor volume delineation in head-and-neck cancer using CT and PET/CT fusion

PURPOSE: To assess the need for gross tumor volume (GTV) delineation protocols in head-and-neck cancer (HNC) treatment planning by use of positron emission tomography (PET)/computed tomography (CT) fusion imaging. Assessment will consist of interobserver and intermodality variation analysis. METHODS AND MATERIALS: Sixteen HNC patients were accrued for the study. Four physicians (2 neuroradiologists and 2 radiation oncologists) contoured GTV on 16 patients. Physicians were asked to contour GTV on the basis of the CT alone, and then on PET/CT fusion. Statistical analysis included analysis of variance for interobserver variability and Student's paired sample t test for intermodality and interdisciplinary variability. A Boolean pairwise analysis was included to measure degree of overlap. RESULTS: Near-significant variation occurred across physicians' CT volumes (p = 0.09) and significant variation occurred across physicians' PET/CT volumes (p = 0.0002). The Boolean comparison correlates with statistical findings. One radiation oncologist's PET/CT fusion volumes were significantly larger than his CT volumes (p < 0.01). Conversely, the other radiation oncologist's CT volumes tended to be larger than his fusion volumes (p = 0.06). No significant interdisciplinary variation was seen. Significant disagreement occurred between radiation oncologists. CONCLUSION: Significant differences in GTV delineation were found between multiple observers contouring on PET/CT fusion. The need for delineation protocol has been confirmed.     

F-fluorocholine PET-guided target volume delineation techniques for partial prostate re-irradiation in local recurrent prostate cancer

Background and purpose

We evaluate the contribution of ¹⁸F-choline PET/CT in the delineation of gross tumour volume (GTV) in local recurrent prostate cancer after initial irradiation using various PET image segmentation techniques.

Materials and methods

Seventeen patients with local-only recurrent prostate cancer (median = 5.7 years) after initial irradiation were included in the study. Rebiopsies were performed in 10 patients that confirmed the local recurrence. Following injection of 300 MBq of ¹⁸F-fluorocholine, dynamic PET frames (3 min each) were reconstructed from the list-mode acquisition. Five PET image segmentation techniques were used to delineate the ¹⁸F-choline-based GTVs. These included manual delineation of contours (GTV_man) by two teams consisting of a radiation oncologist and a nuclear medicine physician each, a fixed threshold of 40% and 50% of the maximum signal intensity (GTV_40% and GTV_50%), signal-to-background ratio-based adaptive thresholding (GTV_SBR), and a region growing (GTV_RG) algorithm. Geographic mismatches between the GTVs were also assessed using overlap analysis.

Results

Inter-observer variability for manual delineation of GTVs was high but not statistically significant (p = 0.459). In addition, the volumes and shapes of GTVs delineated using semi-automated techniques were significantly higher than those of GTVs defined manually.

Conclusions

Semi-automated segmentation techniques for ¹⁸F-choline PET-guided GTV delineation resulted in substantially higher GTVs compared to manual delineation and might replace the latter for determination of recurrent prostate cancer for partial prostate re-irradiation. The selection of the most appropriate segmentation algorithm still needs to be determined.