PET-CT定位图像上医生对肺癌大体肿瘤体积和临床靶体积定义的影响

目的 研究医生在PET-CT图像上对勾画肺癌大体肿瘤体积(GTV)和临床靶体积(CTV)的影响.方法 选取10例2008-2009年间PET-CT定位的肺癌患者,由本科胸组4位主任医生和副主任医生各自独立确定其GTV、CTV.比较每位患者GTV、CTV的平均值、最大值/最小值、变异系数(标准差/平均值);同时比较CTV外轮廓边界位置并计算其系统误差.结果 GTV、CTV最大值与最小值比的平均值分别为1.66、1.65,变异系数分别为0.20、0.17,体积差异较大原因主要为同侧肺门和纵隔淋巴结区域不同.CTV头脚方向与左右、前后方向系统误差分别为0.48 cm与0.37、0.32 cm (F=0.40、0.60、0.15,P=0.755、0.618、0.928).结论 不同放疗科医生在肺癌患者PET-CT定位图像上定义靶区存在差异,GTV、CTV最大值与最小值比的平均值均在1.7以下,差异较大主要原因为位于肺门或纵隔淋巴结区域.CTV头脚方向系统误差较左右和前后方向稍大但均<5 mm.

Abstract：

Objective To study the variation of gross tumor volume (GTV) and clinical target volume (CTV) definition for lung cancer between different doctors.Methods Ten lung cancer patients with PET-CT simulation were selected from January 2008 to December 2009.GTV and CTV of these patients were defined by four professors or associate professors of radiotherapy independently.Results The mean ratios of largest to smallest GTV and CTV were 1.66 and 1.65, respectively.The mean coefficients of variation for GTV and CTV were 0.20 and 0.17, respectively.System errors of CTV definition in three dimension were less than 5 mm, which was the largest in inferior and superior (0.48 cm,0.37 cm,0.32 cm;F=0.40,0.60,0.15,P=0.755,0.618,0.928).Conclusions The variation of GTV and CTV definition for lung cancer between different doctors exist.The mean ratios of largest to smallest GTV and CTV were less than 1.7.The variation was in hilar and mediastinum lymphanode regions.System error of CTV definition was the largest (<5 mm) in cranio-caudal direction.     

Excluding either gross tumor volume or planning target volume from the normal lung volume in lung cancer irradiation: Evaluation of the dosimetric impact

PurposeWhen evaluating dosimetric parameters predictive of lung toxicity in lung cancer, the total lung volume can be defined to exclude the gross tumor volume (lung-GTV) or to exclude the planning target volume (lung-PTV). The purpose of the study was to evaluate the impact of these 2 types of delineation on the dosimetric parameters V20, V30, and mean lung dose (MLD).Methods and MaterialsWe analyzed 69 patients with lung cancer treated with 3-dimensional radiation therapy. Normal lung volume was defined using 2 modalities of delineation: lung-GTV and lung-PTV. The lung volume inside the PTV, but outside the GTV, corresponded to the margins within the lung parenchyma applied to the GTV and the clinical target volume (CTV) to obtain the PTV. This volume (expressed in percentage of total lung volume) increases with the following: (1) the margins (GTV to CTV and CTV to PTV) increase within the lung parenchyma; (2) the GTV increases; and (3) the total lung volume decreases.ResultsMean reduction of lung volume was 5.1% (range, 1.4-10.0). With the delineation lung-PTV rather than lung-GTV, the mean reduction was 3.1% (P < 10^- 7), 3.3% (P < 10^- 7), and 2.1 Gy (P < 10^- 7) for V20, V30, and MLD, respectively. These reductions correlated strongly with reduction of lung volume (r² range, 0.89-0.96). For 25% of patients having greater reduction of lung volume (high margins, high tumor volume, small lung volume), reduction of V20 ranged from 4.5%-6.3%, reduction of V30 ranged from 4.6%-7.0%, and reduction of MLD ranged from 2.9 Gy-4 Gy.ConclusionsThe dosimetric parameters V20, V30, and MLD are reduced with the delineation using lung-PTV rather than lung-GTV. These reductions correlate with lung volume in the PTV and can be significant.     

CT用于非小细胞肺癌靶区勾画的价值

目的　根据非小细胞肺癌 (NSCLC)患者术前CT勾画的靶区与术后病理指导勾画的靶区相比较 ,探讨CT在三维适形和调强放射治疗中确定靶区的价值和作用。方法　 33例经病理确诊的NSCLC患者均行术前CT检查 ,并且在CT片上勾画包括原发肿瘤和局部转移淋巴结在内的大体肿瘤靶区 (GTV)。原发灶的大体肿瘤靶区 (GTV T)在肺窗上勾画 ,肺门和纵隔转移淋巴结的大体肿瘤靶区 (GTV N)的在纵隔窗上勾画。淋巴结是否有侵犯是以短轴为标准 ,≥ 1cm视为异常 ,<1cm视为正常。手术切除原发肿瘤以及术前CT检查或术中疑为受侵的淋巴结。术后根据手术所见和病理结果在术前CT片上再次勾画GTV ,对两份GTV进行三维重建、体积计算并做分析和比较。结果　 33例GTV勾画对比中 ,2 4例 ( 72 .7% )无变化 ,3例 ( 9.1% )较术前缩小 ,6例 ( 18.2 % )较术前扩大。CT确定GTV地准确性为 72 .7%。结论　 81.8%的患者GTV可以完全包括原发肿瘤和局部转移的淋巴结 ,18.2 %的患者GTV未能完全包括原发肿瘤和局部转移的淋巴结。     

Internal target volume determined with expansion margins beyond composite gross tumor volume in three-dimensional conformal radiotherapy for lung cancer

PURPOSE: Gross tumor volume (GTV) of lung cancer defined by fast helical CT scan represents an image of moving tumor captured at a point in active respiratory movement. However, the method for defining internal margins beyond GTV to account for its expected physiologic movement and all variations in size and shape during the administration of radiation has not been established. The goal of this study was to determine the internal margins with expansion margins beyond individual GTVs defined with (1) fast scan at shallow free breathing, (2) breath-hold scans at the end of tidal volume inspiration and expiration, and (3) 4-s slow scan to approximate the composite GTV of all scans. METHODS AND MATERIALS: A series of sequential CT scans were acquired with (1) a fast helical scan at shallow free breathing and (2) breath-hold scans at the end of tidal volume expiration and inspiration for the first 6 patients, and (3) a 4-s slow scan at quiet free breathing, which was added for the latter 7 patients. We fused breath-hold scans and the 4-s slow scan to the fast scan at shallow free breathing to generate the composite GTV. Margins necessary to encompass the composite GTV beyond individual GTVs defined by either fast scan at quiet free breathing, breath-hold scans, or the 4-s slow scan at quiet free breathing were defined as expansion or internal margins and termed the internal target volumes. The centroid of the tumor volume was also used as another reference for tumor movement. RESULTS: Thirteen patients with 14 tumors were enrolled into the study. Substantial tumor movement was noted by either the extent of internal margins beyond each GTV or the movement of the centroid. Internal margins varied significantly according to the method of CT scanning for determination of GTV. Even for tumors in the same lobe of the lung, a wide range of internal margins and significant variation in the centroid movement in all directions (x, y, and z) were observed. The GTV of a single fast helical scan at free breathing (n = 14) required the largest internal margin (mean, 3.5 mm; maximum, 18 mm; standard deviation [SD], 4.2 mm) to match the composite GTV, compared with those of the 4-s slow scan (mean 2.7 mm, maximum 14 mm, SD 3.5 mm) or combined breath-hold scans (mean 1.1 mm, maximum 9 mm, SD 1.9 mm). Internal margins (expansion margins) required to approximate the composite GTV in 95% of cases were 13 mm, 10 mm, and 5 mm for the GTVs of a single fast scan, 4-s slow scan, and breath-hold scans at the end of tidal volume inspiration and expiration, respectively. CONCLUSIONS: The internal margins required to account for the internal tumor motion in three-dimensional conformal radiotherapy are substantial. For the use of symmetric and population-based margins to account for internal tumor motion, GTV defined with breath-hold scans at the end of tidal volume inspiration and expiration has a narrower range of internal margins in all directions than that of either a single fast scan or 4-s slow scan.     

Performance status assessment in cancer patients. An inter-observer variability study.

The ECOG Scale of Performance Status (PS) is widely used to quantify the functional status of cancer patients, and is an important factor determining prognosis in a number of malignant conditions. The PS describes the status of symptoms and functions with respect to ambulatory status and need for care. PS 0 means normal activity, PS 1 means some symptoms, but still near fully ambulatory, PS 2 means less than 50%, and PS 3 means more than 50% of daytime in bed, while PS 4 means completely bedridden. An inter-observer variability study of PS assessment has been carried out to evaluate the non-chance agreement among three oncologists rating 100 consecutive cancer patients. Total unanimity was observed in 40 cases, unanimity between two observers in 53 cases, and total disagreement in seven cases. Kappa statistics reveal the ability of the observers compared to change alone and were used to evaluate non-chance agreement. Overall Kappa was 0.44, (95% confidence limits 0.38-0.51). The Kappa for PS 0 was 0.55 (0.44-0.67), while those for PS 1, 2, 3 and four were 0.48 (0.37-0.60), 0.31 (0.19-0.42), 0.43 (0.32-0.55), and 0.33 (0.33-0.45), respectively. If one observer allocated patients to PS 0-2, then another randomly selected observed placed the patients in the same category with a probability of 0.92. For patients with PS 3-4 the probability that the same category would be chosen was 0.82. Overall, the non-chance agreement between observers was only moderate, when all ECOG Performance Status groups were considered. However, agreement with regard to allocation of patients to PS 0-2 versus 3-4 was high. This is of interest because this cut-off is often used in clinical studies.     

Radiotherapy of skin cancer. Definitions of gross tumor volume and clinical target volume. Practical implications]

Delineation of GTV and CTV for radiotherapy of skin cancer depends on the natural history of each cancer type and on the clinical presentation of the disease. It is fundamental for the choice of the most adapted radiation technique.     

Variation in background intensity affects PET-based gross tumor volume delineation in non-small-cell lung cancer: The need for individualized information

Purpose

Efficient tumor volume delineation by the combined use of PET/CT scanning is necessary for the proper treatment of non-small cell lung cancer (NSCLC). To understand the effect of variation in background intensity on PET-based gross tumor volume (GTV) delineation, we determined the background standard uptake values (SUVs) in normal lung, aorta (blood pool), and liver tissues and determined GTVs using different methods.

Methods

Thirty-seven previously untreated patients with pathologically confirmed NSCLC underwent PET/CT scanning with ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG). To obtain ¹⁸F-FDG uptake values in normal tissues, regions of interest in the lung lobes (left upper, left lower, right upper, right middle, and right lower), aorta, and liver zones (left, intermediate, and right) were measured. The coefficient of variation (CV) of the SUV was measured for each normal structure. The CT-based GTV (GTV_CT) was considered as the standard to which all PET-based GTVs were compared, and the correlation coefficient was analyzed to compare GTV obtained by the various delineation methods. Linear and logarithmic regression analyses were used to determine the relationship between GTV_CT and GTV_PET.

Results

Normal lung tissue showed a significantly lower SUV and less stability than tissue of the aorta or liver. For the lung, aorta, and liver, the maximum SUV (SUV_max) was 0.82 ± 0.32, 2.35 ± 0.37, and 3.24 ± 0.50 (CV: 38.79%, 15.82%, and 15.30%) and average SUV (SUV_ave) was 0.49 ± 0.18, 1.68 ± 0.32, and 2.34 ± 0.36 (CV: 36.38%, 18.92%, and 15.44%), respectively. The SUVs of the lung varied from lobe to lobe. The GTV delineation method using the SUV_ave of the lung lobe in which the tumor was found as background in the source-to-background ratio (SBR) method showed the best correlation with the volume of CT-based GTV (r = 0.81).

Conclusions

Our results show vast variation in the SUV among normal tissues, as well as in the different lung lobes. The tumor volume delineated using the SBR method correlated well with the CT-based tumor volume. We conclude that it is reasonable and precise to contour GTV in patients with NSCLC after taking into account the background intensity of the lung lobe in which the tumor is found.     

Conformal radiotherapy for lung cancer: different delineation of the gross tumor volume (GTV) by radiologists and radiation oncologists.

PURPOSE: Delineation of the gross tumor volume (GTV) and organs at risk constitutes one of the most important phases of conformal radiotherapy (CRT) procedures. In the absence of a clear redefinition of the GTV, for a given pathology, complemented by detailed contouring procedures, the GTV are likely to be estimated rather arbitrarily with the risk of tumor underdosage or detriment to the surrounding healthy tissues. The objective of this study was to compare the delineation of the GTV of intrathoracic tumors by radiologists and radiation oncologists with experience in the field in various centers. MATERIALS AND METHODS: The computed tomography images of ten patients with nonoperated non-small cell lung cancer (NSCLC) eligible for CRT were reviewed. Nine radiologists and eight radiation oncologists working in five different centers, classified as either 'junior' or 'senior' according to their professional experience, had to delineate the GTV (primary tumor and involved lymph nodes) with predefined visualization parameters. A dedicated software was used to compare the delineated volumes in terms of intersection and union volumes and to calculate the 'concordance index' for each patient and each subgroup of physicians. RESULTS: Significant differences between physicians and between centers were observed. Compared to radiation oncologists, radiologists tended to delineate smaller volumes and encountered fewer difficulties to delineate 'difficult' cases. Junior physicians, regardless of their specialty, also tended to delineate smaller and more homogeneous volumes than senior physicians, especially for 'difficult' cases. CONCLUSIONS: Major discordances were observed between the radiation oncologists' and the radiologists' delineations, indicating that this step needs to be improved. A better training of radiation oncologists in thoracic imaging and collaboration between radiation oncologists and radiologists should decrease this variability. New imaging techniques (image fusion, positron emission tomography, magnetic resonance imaging spectroscopy, etc.) may also provide a useful contribution to this difficult delineation.     

Gross tumor volume and clinical target volume in radiotherapy: lung cancer]

Radiotherapy plays a major role as a curative treatment of various stages non-small cell lung cancers (NSCLC): as an exclusive treatment in curative attempt for patients with unresectable stages I and II; as a preoperative treatment, which is often associated with chemotherapy, for patients with surgically stage IIIA NSCLC in clinical trials; in association with chemotherapy for unresectable stages IIIA and IIIB patients. Currently, three-dimensional conformal radiotherapy allows for some dose escalation, increasing radiation quality. However, the high inherent conformality of this radiotherapy technique requires a rigorous approach and an optimal quality of the preparation throughout the treatment procedure and specifically of the accurate definition of the safety margins (GTV, CTV...). Different questions remain specific to lung cancers: 1) Despite the absence of randomized trials, the irradiated lymph nodes volume should be only, for the majority of the authors, the visible macroscopically involved lymph nodal regions. However, local control remains low and solid arguments suggest the poor local control is due to an insufficient delivered dose. Therefore the goal of radiotherapy, in this particular location, is to improve local control by increasing the dose until the maximum normal tissue tolerance is achieved, which essentially depends on the dose to the organs at risk (OAR) and specifically for the lung, the esophagus and the spinal cord. For this reason, the irradiated volume should be as tiny as possible, leading to not including the macroscopically uninvolved lymph nodes regions in prophylactic view in the target volume; 2) The lung is one of the rare organs with extensive motion within the body, making lung tumors difficult to treat. This particular point is not specifically considered in the GTV and CTV definitions but it is important enough to be noted; 3) When radiation therapy starts after a good response to chemotherapy, the residual tumoral volume should be defined as the target volume in place of the initial tumor volume. These different elements are discussed in this paper.     

Dynamic contrast enhanced CT aiding gross tumor volume delineation of liver tumors: An interobserver variability study

Purpose

To evaluate the application of perfusion CT for gross tumor volume (GTV) delineation for radiotherapy of intrahepatic tumors.

Materials and methods

15 radiotherapy patients with confirmed liver tumors underwent contrast enhanced 4D-CT (Philips Brilliance Big-bore) as well as dynamic contrast enhanced (DCE) CT (GE 750HD). Perfusion maps were generated with CT perfusion v5 from GE. Five observers delineated GTVs of all intrahepatic foci on the 4D-CT, time-averaged DCE-CT and perfusion CT for every patient. STAPLE consensus contours were generated. Dice’s coefficients were compared between GTVs generated by observers on each image set and the corresponding consensus GTVs. Comparisons were also performed with patients stratified by hepatocellular carcinoma (HCC) metastatic tumors, and by tumor volume.

Results

Overall, mean Dice’s coefficients were 0.81 ± 0.14, 0.84 ± 0.10, and 0.81 ± 0.14 for 4D-CT, DCECT and perfusion. DCE-CT performed significantly better than 4D-CT and perfusion (p = 0.005 and p = 0.01 respectively). For patients with HCC, DCE-CT reduced interobserver variability significantly compared to 4D-CT (Dice’s coefficients 0.87 vs. 0.84, p < 0.05). For patients with metastatic disease time-averaged DCE-CT images decreased variability compared to 4D-CT (Dice’s coefficient 0.81 vs. 0.76, p < 0.05), especially true for tumors < 100 cc. The smaller tumors results are important to be included here.

Conclusions

DCE-CT imaging of liver perfusion reduced interobserver variability in GTV delineation for both HCC and metastatic liver tumors.     

胸部增强CT扫描对肺癌大体肿瘤体积勾画的影响

目的探讨胸部增强CT扫描对勾画肺癌大体肿瘤体积(GTV)的影响。方法连续选择肿瘤紧邻纵隔或累及肺门、病理确诊的肺癌患者7例,在治疗体位下行全胸部平扫(C)和增强CT扫描(C+),扫描范围相同。将CT图像传人虚拟模拟计划工作站(AcQSim)中,每份图像传7次(C3次,C+4次)。3位年资相同的放疗科医生完全独立地在C与C+的CT图像上勾画GTV(GTV、GTV+),然后3位医生在另一份C+图像上共同勾画GTV(标准GTVco)。以GTVco形成的计划靶体积(PTV)为标准在治疗计划系统中进行剂量计算并优化,等中心点为剂量归一点(参考点),处方剂量为60Gy。通过图像融合技术将3位医生在C+、C图像上勾画的GTV复制到GTVco图像上,分别计算GTV、GTV+和GTVco共7份GTV体积、GTV三维最大径、90%等剂量线包括PTV的相对体积(V90)及PTV内最小剂量(Dmin),并计算GTV、GTV+与GTVco的比值R及R的变异系数CV,然后对GTV、GTV+两组数据进行配对样本t检验。结果GTV+、GTV体积R分别为1.04±0.16、1.25±0.52,GTV+体积、V90、Dmin的CV均小于GTV的(P值分别<0.01、0.05、0.05)。结论勾画肿瘤紧邻纵隔或累积肺门靶区时,增强CT扫描可明显提高GTV勾画的准确性和一致性,且费用较小容易实施。     

非手术肺癌放疗靶区变化的锥形束CT观察

目的 用千伏级锥形束CT (KVCBCT)离线分析非手术肺癌大体肿瘤体积(GTV)随放疗变化规律。
方法 18例患者分为2个组,A组[13例, 依据GTV变化分为A₁(10例)、A₂(3例)组] 常规放疗(1.8~ 2.2 Gy/次),每周治疗前采集1组KVCBCT;B组(5例)加速放疗(5~ 8 Gy/次),每次治疗前采集1组KVCBCT。在治疗计划系统上融合KVCBCT和CT图像后分析GTV变化。
结果 A组GTV缩减>20%者占77%;A₁组在治疗第4周(第20次治疗) GTV递减变化达最大,GTV缩减(0.94±9.94)%,最大缩减－56.76%;A₂组GTV变化与治疗时间无关。B组GTV缩减(－7.41±1.76)%,最大缩减－15.91%,缩减≤10%占71%,GTV随治疗进行变化较小。
结论 GTV变化随治疗进行无统一变化趋势,在第20次治疗时若GTV缩减>20%建议用自适应放疗。     

应用四维CT评价肺癌大体肿瘤体积随呼吸运动的位移及影响因素

目的 应用四维CT(4DCT)测量肺癌大体肿瘤体积(GTV)在三维方向上随呼吸运动的位移并分析其影响因素.方法 选择21例肺癌患者共22个肺部病灶行4DCT扫描,勾画10个呼吸时相中的GTV0%～GTV90%.测量GTV变化及GTV质心、边界在三维方向上随呼吸运动的位移,计算出三维空间位移向量→(II)v并分析其影响因素.结果 GTV变化的平均值为+14.3%或-8.4%,GTV 中心点和GTV各边界在左右、前后、头脚方向上随呼吸运动的位移分别为(0.20±0.16)、(0.18±0.12)、(0.53±0.59)cm和(0.42±0.23)、(0.41±0.22)、(0.57±0.70)cm,其中GTV中心点在头脚方向上的位移大于左右(Z=-2.12,P=0.034)、前后方向(Z=-2.10,P=0.035),GTV各边界在头脚方向上的位移与左右、前后方向差异无统计学意义(Z=-0.81,P=0.417;Z=-0.86,P=0.391).GTV中心点随呼吸的位移大小只与所在肺叶有关,GTV位于下叶者在头脚方向的位移大于位于上叶者[(0.87±O.64)和(0.35±0.49)em,(t=-2.12,P=0.047)],在前后、左右方向上的位移无差异[(0.23±0.10)和(0.19±0.18)cm(t=-0.49,P=0.629)、(0.21±0.13)和(0.17±0.11)cm(t=-0.76,P=0.460)].GTV体积大小与GTV中心点在头脚、前后、左右方向位移以及三维空间位移向量→(II)v间无明显相关性(r=0.306、-0.062、-0.279、-0.300,P=0.189、0.796、0.234、0.199).结论 肺癌患者GTV随呼吸运动的位移个体化差异明显,头脚方向位移尤为显著,应用4DCT可进行较好评价;下叶病灶位移大,GTV大小与位移间无明显相关性.

Abstract：

Objective This study was to assess the three-dimensional gross tumor volume(GTV)motion of lung cancer caused by respiration using four-dimensional computed tomography(4DCT),and to analyze the influenee factors.Methotis Four-DCT scans of 22 lung focuses in 21 patients with lung cancer were analyzed.The gross tumor volume was contoured in all 10 respiration phases of 4DCT scans.The changes in volume of GTV,the 3D motion of the centroid,boundary of GTV and the 3D spatial motion vectors were calculated and the irdluenee factors were analyzed.Results The average change in volume of GTV was+14.3%(0.2%.42.5%)/-8.4%(0.4%-38.6%),the average movement amplitude of GTV centroid and GTV boundary were(0.18±0.12)cm,(0.20±0.16)cm,(0.53±0.59)cm and(0.42±0.23)cm,(0.41±0.22)cm,(0.57±0.70)cm in medio-lateral,vertro-dorsal,cranio-caudal(CC) direction,respectively.The CC movement was larger than other directions(Z=-2.12,P=0.034;Z:-2.10,P=0.035),and no significant difference was observed in 3D motion of GTV boundary(Z=-0.81.P=0.417;Z=-0.86,0.391).The CC motion of GTV eentroid in lower lobe was larger than that in upper lobe[(0.87±0.64)and(0.35±0.49)cm,(t=-2.12,P=0.047)],and no significant difference was found in other directions[(0.23±0.10)and(0.19±0.18)em(t=-0.49,P=0.629),(0.21±0.13)and(0.17±0.11)cm(t=0.76,P=0.460)].There was no correlation of the 3D movement and 3D spatial motion vector of GTV to the volume of GTV(r=-0.306,-0.062,-0.279,-0.300;P=0.189,0.796.0.234,0.199).Conclusions GTV motion of patients with lung cancer is individual,the CC movement is the moat obvious,using 4DCT to assess is comparatively accurate.The motion amplitude of lower lobe focuses is larger.No significant correlation of the GTV motion to the volume was observed.Larger sample study is needed to analyze the influence of adjacency to the GTV motion.     

Comparison of CT- and FDG-PET-defined gross tumor volume in intensity-modulated radiotherapy for head-and-neck cancer

PURPOSE: To compare the gross tumor volume (GTV) identified on CT to that obtained from fluorodeoxyglucose (FDG) positron emission tomography (PET) and determine the differences in volume and dose coverage of the PET-GTV when the CT-GTV is used for radiotherapy planning. METHODS AND MATERIALS: A total of 40 patients with intact squamous cell carcinoma arising in the head-and-neck region underwent intensity-modulated radiotherapy (IMRT) at one department. All patients underwent CT simulation for treatment planning followed by PET-CT in the treatment position. CT simulation images were fused to the CT component of the PET-CT images. The GTV using the CT simulation images was contoured (CT-GTV), as was the GTV based on the PET scan (PET-GTV). The IMRT plans were obtained using the CT-GTV. RESULTS: The PET-GTV was smaller, the same size, and larger than the CT-GTV in 30 (75%), 3 (8%), and 7 (18%) cases respectively. The median PET-GTV and CT-GTV volume was 20.3 cm(3) (range, 0.2-294) and 37.2 cm(3) (range, 2-456), respectively. The volume of PET-GTV receiving at least 95% of the prescribed dose was 100% in 20 (50%), 95-99% in 10 (25%), 90-94% in 3 (8%), 85-89% in 1 (3%), 80-84% in 2 (5%), 75-79% in 1 (3%), and <75% in 3 (8%) cases. The minimal dose received by 95% of the PET-GTV was >/=100% in 19 (48%), 95-99% in 11 (28%), 90-94% in 5 (13%), 85-89% in 2 (5%), and <75% in 3 (8%) cases. CONCLUSION: The PET-GTV was larger than the CT-GTV in 18% of cases. In approximately 25% of patients with intact head-and-neck cancer treated using IMRT, the volume of PET-GTV receiving at least 95% of the prescribed dose and minimal dose received by 95% of the PET-GTV were less than optimal.     

Clinical implications of defining the gross tumor volume with combination of CT and 18FDG-positron emission tomography in non-small-cell lung cancer

PURPOSE: To compare the planning target volume (PTV) definitions for computed tomography (CT) vs. positron emission tomography (PET) in non-small-cell lung cancer (NSCLC). METHODS AND MATERIALS: A total of 21 patients with NSCLC underwent three-dimensional conformal radiotherapy planning. All underwent a staging F-18 fluorodeoxyglucose-position emission tomography (18FDG-PET) scan and underwent treatment simulation using CT plus a separate planning 18FDG-PET scan. Three sets of target volumes were defined: Set 1, CT volumes (CT tumor + staging PET nodal disease); Set 2, PET volumes (planning PET tumor {gross tumor volume (GTV) = [(0.3069 x mean standardized uptake value) + 0.5853])}; Set 3, composite CT-PET volumes (fused CT-PET tumor). Sets 1 and 2 were compared using a matching index. Three-dimensional conformal radiotherapy plans were created using the Set 1 (CT) volumes; and coverage of the Set 3 (composite) volumes was evaluated. Separate three-dimensional conformal radiotherapy plans were designed for the Set 3 volumes. RESULTS: For the primary tumor GTV, the Set 1 (CT) volume was larger than the Set 2 (PET) volume in 48%, smaller in 33%, and equal in 19%. The mean matching index was 0.65 (35% CT-PET mismatch). Although quantitatively similar, the volumes differed qualitatively. The Set 3 (composite) volume was larger than either CT or PET alone in 62%, smaller in 24%, and equal in 14%. The dose-volume histogram parameters did not differ among the plans for Set 1 (CT) vs. Set 3 (composite) volumes. Small portions of the Set 3 PTV were significantly underdosed in 40% of cases using the CT-only plan. CONCLUSION: Computed tomography and PET are complementary and should be obtained in the treatment position and fused to define the GTV for NSCLC. Although the quantitative absolute target volume is sometimes similar, the qualitative target locations can be substantially different, leading to underdosage of the target when planning is done using CT alone without PET fusion.     

基于四维CT勾画非小细胞肺癌内大体肿瘤靶体积的三种方法比较

Objective To compare positional and volumetric differences of internal gross tumor volume (IGTV) delineated separately by three approaches based on four-dimensional CT (4DCT) for the primary tumor of non-small cell lung cancer (NLCLC). Methods Twenty-one patients with NLCLC underwent big bore 4DCT simulation scan of the thorax. IGTVs of the primary tumor of NSCLC were tumor on the MIP images were delineated to produce IGTVMIP. The position of the target center, the volume of target, the degree of inclusion (DI) and the matching index (MI) were compared reciprocally between IGTV10, IGTVEI+EE and IGTVMIP. Results Average differences between the position of the center of IGTVs on direction of x,y and z axes were less than 1 mm, with no statistically significant difference. The volume of IGTV10 was larger than that of IGTVEI+EE, the difference was statistically significant (t=2.37,P=0.028);the volume of IGTV10 was larger than that of IGTVMIP, but the difference was not statistically significant(t=1.95 ,P=0.065). The ratio of IGTVEI+EE with IGTV10, IGTVMIP with IGTV10 were 0.85±0.08 and 0.92±0.11, respectively. DI of IGTVEI+EE in IGTV10, IGTVMIP in IGTV10 were 84.78% ± 8. 95% and 88.47% ±9.04%. MI between IGTV10 and IGTVEI+EE, IGTV10 and IGTVMIP were 0.85 ±0.09, 0.86±0. 09, respectively. Conclusions The center displacement of the IGTVs delineated separately by the three different techniques based on 4DCT images are not obvious; IGTVEI+EE and IGTVMIP can not replace IGTV10 , however , IGTVMIP is more close to IGTV10 comparing to IGTVEI+EE . The ratio of GTVEI+EE with IGTV10 is correlated to the tumor motion vector. As the vector increases, the ratio of GTVEI+EE with IGTV10decreases, especially for small tumors.     

基于四维CT勾画非小细胞肺癌内大体肿瘤靶体积的三种方法比较

目的 比较基于四维CT(4DCT)三种方法勾画非小细胞肺癌(NSCLC)内大体肿瘤靶体积(IGTV)位置和大小差异.方法 21例NSCLC患者行胸部4DCT模拟定位扫描,采用10个呼吸时相得到IGTV10、0%和50%时相得到IGTVEI+EE、在最大密度投影(MIP)图像上得到IGTVMIP.对比3种勾画方法所得IGTV10、IGTVEI+EE、IGTVMIP的位置、体积、包含度及匹配指数.结果 IGTV10、IGTVEI+EE、IGTVMIP的中心在x、y、z轴上平均差异＜1 mm且均相似(t=0.35～1.57、P=0.730～0.132).IGTV10＞IGTVET+EE(t=2.37、P=0.028),IGTV10与GTVMIP相似(t=1.95,P=0.065),IGTVEI+EE与IGTV10、IGTVMIP与IGTV10比值分别为0.85±0.08和0.92±0.11.IGTV10对IGTVEI+EE和IGTVMIP的包含度分别为84.78%±8.95%和88.47%±9.04%.IGTV10与IGTVEI+EE、IGTV10与IGTVMIP的匹配指数分别为0.85±0.09、0.86±0.09.结论 基于4DCT不同方法所勾画的IGTV中心位置变化不明显;IGTVEI+EE和IGTVMIP均不能替代IGTV10,但IGTVMIP与IGTV10大小更接近;IGTVEI+EE与IGTV10比值与肿瘤运动矢量相关,肿瘤三维运动幅度大且体积较小时IGTVEI+EE与IGTV10比值较小.

Abstract：

Objective To compare positional and volumetric differences of internal gross tumor volume (IGTV) delineated separately by three approaches based on four-dimensional CT (4DCT) for the primary tumor of non-small cell lung cancer (NLCLC). Methods Twenty-one patients with NLCLC underwent big bore 4DCT simulation scan of the thorax. IGTVs of the primary tumor of NSCLC were tumor on the MIP images were delineated to produce IGTVMIP. The position of the target center, the volume of target, the degree of inclusion (DI) and the matching index (MI) were compared reciprocally between IGTV10, IGTVEI+EE and IGTVMIP. Results Average differences between the position of the center of IGTVs on direction of x,y and z axes were less than 1 mm, with no statistically significant difference. The volume of IGTV10 was larger than that of IGTVEI+EE, the difference was statistically significant (t=2.37,P=0.028);the volume of IGTV10 was larger than that of IGTVMIP, but the difference was not statistically significant(t=1.95 ,P=0.065). The ratio of IGTVEI+EE with IGTV10, IGTVMIP with IGTV10 were 0.85±0.08 and 0.92±0.11, respectively. DI of IGTVEI+EE in IGTV10, IGTVMIP in IGTV10 were 84.78% ± 8. 95% and 88.47% ±9.04%. MI between IGTV10 and IGTVEI+EE, IGTV10 and IGTVMIP were 0.85 ±0.09, 0.86±0. 09, respectively. Conclusions The center displacement of the IGTVs delineated separately by the three different techniques based on 4DCT images are not obvious; IGTVEI+EE and IGTVMIP can not replace IGTV10 , however , IGTVMIP is more close to IGTV10 comparing to IGTVEI+EE . The ratio of GTVEI+EE with IGTV10 is correlated to the tumor motion vector. As the vector increases, the ratio of GTVEI+EE with IGTV10decreases, especially for small tumors.     

头颈部癌大体肿瘤体积MRI与CT定义比较研究

目的 采用病理标本验证基于MRI、CT定义的头颈部癌大体肿瘤体积(GTV)准确性差异,为临床评价两种影像方法提供依据。方法 选取10只新西兰大白兔建立VX₂鳞癌细胞系头颈部癌模型,6例成功。每只荷瘤兔在同一体位及固定下行头颈部MR和CT扫描,随后处死并置于明胶溶液－70℃固定72 h。采用可定位曲线锯按照与影像扫描相同位置及层厚切割标本来获取病理解剖图像。分别在MRI、CT、病理解剖图像上勾画GTV,计算GTV_MRI、GTV_CT、GTV_SA和体积差异比(VDR),双向分类方差分析和配对t检验比较差异。结果 GTV_MRI、GTV_CT、GTV_SA平均值分别为(8.20±2.56)、(8.40±2.20)、(8.11±2.88) cm³(F=0.06,P=0.943)。VDR_MRI-SA、VDR_CT-SA平均值分别为0.180±0.060、0.309±0.091(t=7.49,P=0.001)。结论 基于MRI的头颈部癌GTV定义的准确性优于CT。     

Intra-patient variability of tumor volume and tumor motion during conventionally fractionated radiotherapy for locally advanced non-small-cell lung cancer: a prospective clinical study

PURPOSE: The aim of this study was to investigate the change in tumor volume, motion, and breathing frequency during a course of radiotherapy, for locally advanced non-small-cell lung cancer. METHODS AND MATERIALS: A total of 23 patients underwent computed tomography-positron emission tomography (CT-PET) and respiration correlated CT scans before treatment, which was repeated in the first and second weeks after the start of radiotherapy. Patients were treated with an accelerated fractionation schedule, 1.8 Gy twice a day, with a total tumor dose depending on preset dose constraints for the lungs and spinal cord. RESULTS: A striking heterogeneity of tumor volume changes was observed at all time points. In some patients the volume decreased >30% (3/23), whereas in others the volume increased >30% (4/24); but for the majority of patients (16/23), the tumor volume changed only slightly (<30%). No significant changes in average tumor motion or breathing frequencies were observed during treatment. Although a number of changes in individual tumor motion were seen, only in 1 patient would this have led to an increase of the internal margin >1 mm in 1 direction, 1 week after the start of treatment, and in 3 patients for 1 direction, 2 weeks after the start of the treatment. CONCLUSION: In this patients in this study, a large variability in changes in tumor volume was observed. This underscores the need for repeated imaging during the course of radiotherapy. However, the changes in tumor motion are small, which indicates that repeated respiration correlated CT does not appear to be necessary.     

Preliminary study of the internal margin of the gross tumor volume in thoracic esophageal cancer

PurposeTo measure the displacement of the tumor of the gross tumor volume (GTV) of thoracic esophageal cancer in the calm states of end-inspiration and end-expiration for determining the internal margin of the GTV (IGTV).MethodsTwenty-two patients with thoracic esophageal cancer who were unable to undergo surgery were identified in our hospital. The patients received radiotherapy. By using 16-slice spiral computed tomography (CT), we acquired the calm states of end-inspiration and end-expiration. The displacement and volume changes in tumor target volume were measured, and the changes were analyzed to determine if these were associated with the tidal volume and the location and length of the target volume V. In the end, we analyzed the displacement of tumor target volume and calculated the internal margin of the GTV by empirical formula.ResultsThe average tidal volume was 463.6 ml. The average GTV at end-inspiration was 33.3 ml and at end-expiration was 33.35 ml. Three was not any significant between two groups (T = ?0.034, P > 0.05). The IGTV (X-axis direction) was 3.09 mm for the right sector and 4.08 mm for the left border; the IGTV (Z-axis direction) was 3.96 mm for the anterior border and 2.83 mm for the posterior border; and the IGTV (Y-axis direction) was 7.31 mm for the upper boundary (head direction) and 10.16 mm for the lower boundary (feet direction). The motion of the GTV showed no significant correlation with the tidal volume of patients and the length of the tumor, but in relation to the tumor location, the displacement of the lower thoracic and the middle thoracic target volumes occurred in the direction of the anterior and right, which were not significantly different (T = 0.859, 0.229, P > 0.05) The significant differences were observed for the other directions (P < 0.05).ConclusionsBecause of respiratory and organ movements, the displacement of the tumor target volume was different in all directions. Therefore, we recommend that expansion of the planning target volume during clinical radiation treatment needs to include the displacement of the tumor target volume caused by respiratory and organ movements during each radiotherapy session.