病例为基础的局部晚期NSCLC靶区勾画共识与争议

目的 分析局部晚期NSCLC靶区勾画中的专家共识与争议。方法 调查国内12家单位对NSCLC靶区勾画相关15个问题意见。由复旦大学附属肿瘤医院选择1份局部晚期NSCLC病例,将定位CT图像和病史资料发送至12家单位,各单位自行组织讨论并委派1位医师在第六届肿瘤精准放化疗暨肺癌多学科高峰论坛上主讲对该病例靶区勾画情况及理论认识,参会专家共同讨论。结果 12家单位全部填写问卷并按时发回。肺癌靶区勾画标准肺窗的窗宽/窗位为800~1600/-600~-750 HU,纵隔窗为350~400/20~40 HU。呼吸动度的测量:经验外扩2~5 mm、模拟定位机测定、四维CT测定、模拟定位机+四维CT测定。GTV外扩CTV距离:原发灶鳞癌5~6 mm、腺癌5~8 mm;纵隔淋巴结转移灶6家单位采用5 mm,6家单位采用同原发病灶一致距离。摆位误差:10家单位5 mm、1家单位3 mm、1家单位4~6 mm。双肺V₂₀限定:10家单位<30%、1家单位<35%、1家单位<28%。局部晚期NSCLC同步放化疗放疗剂量:9家单位60 Gy分30次、1家单位62.7 Gy分33次、1家单位50~60 Gy分25~30次、1家单位60~70 Gy分25~30次。肺内原发病灶靶区勾画:3家GTV→IGTV→PTV、8家GTV→CTV→ITV→PTV、1家GTV→CTV→PTV或GTV→IGTV→CTV→PTV;纵隔淋巴结转移灶靶区勾画:3家GTV→IGTV→PTV、8家GTV→CTV→ITV→PTV、1家GTV→CTV→PTV。放疗过程中10%~100%患者需要改野,38~50 Gy时改野合适。关于PET-CT定位及靶区勾画SUV值尚无统一标准,7家单位已开展MRI定位,10家单位已开展了SBRT治疗早期NSCLC。早期NSCLC (T_1-2N₀M₀)的SBRT靶区勾画:5家单位GTV→IGTV→PTV、3家单位IGTV→PTV、2家单位GTV→CTV→ITV→PTV。周围型早期NSCLC分割6.0~12.5 Gy/次,3~12次;中央型早期NSCLC分割4.6~10.0 Gy/次,5~10次。靶区勾画讨论结果:肺癌靶区勾画目前应采用4DCT或模拟机测定呼吸动度;勾画肺癌靶区时CT肺窗的窗宽/窗位为1600/-600 HU,纵隔窗为400/20 HU;争议主要是纵隔转移淋巴结CTV_nd为累及野照射还是选择性淋巴结预防照射。结论 对局部晚期NSCLC靶区勾画的CT的窗宽、窗位,呼吸运动和摆位误差测量、原发灶靶区勾画方法、同步放化疗放疗剂量及改野时机均已基本达成共识。主要争议和尚未达成共识的是PET-CT定位勾画靶区时显示病灶的最佳SUV值、SBRT治疗早期NSCLC最佳剂量分割模式、CTV_nd的勾画。     

部分乳腺外照射自主呼吸控制不同呼吸状态靶区体积重合度的研究

目的 探讨保乳术后部分乳腺外照射(EB-PBI)自主呼吸控制(ABC)不同呼吸状态体积重合度及其差异,从靶区体积重合的角度,表述ABC辅助呼吸运动对EB-PBI分次内靶区位移的影响.方法 对术腔放置银夹拟行EB-PBI的患者行乳腺托架固定ABC辅助CT模拟定位,同时采集适度深吸气呼吸控制(mDIBH)状态、自由呼吸(FB)状态、深吸气呼吸控制(DEBH)状态各2套CT图像.应用Pinnacle3治疗计划系统,进行2套mDIBH图像间、2套FB图像间、2套DEBH图像间及mDIBH与DEBH图像间自动融合,计算融合图像.选定进行融合的2套图像的大体肿瘤体积(GTV)、临床靶区体积(CTV)、计划靶区体积(PTV)的重合度,比较同一配准中3种靶区各自重合度间及不同配准中同一种靶区重合度间的差异.结果 mDIBH/mDIBH配准中,GTV/GTV、CTV/CTV和PTV/PTV重合度分别为(83.54±11.41)%、(93.00±6.49)%和(95.26±4.90)%,GTV/GTV与CTV/CTV、GTV/GTV与PTV/PTV重合度间差异均有统计学意义(P＜0.05),而CTV/CTV与PTV/PTV重合度间差异无统计学意义(P＞0.05).FB/FB配准中,GTV/GTV、CTV/CTV、PTV/PTV重合度分别为(72.55±29.10)%、(89.36±9.53)%和(92.47±7.25)%,GTV/GTV与CTV/CTV、CTV/CTV与PTV/PTV重合度间差异均无统计学意义(均P＞0.05),而GTV/GTV与PTV/PTV重合度间差异有统计学意义(P＜0.05).DEBH/DEBH配准中,GTV/GTV、CTV/CTV、PTV/PTV重合度分别为(79.48±22.31)%、(92.83±6.77)%和(95.05±4.81)%,3组靶区两两间重合度差异均有统计学意义(均P＜0.05).mDIBH/mDIBH与DEBH/DEBH间、mDIBH/mDIBH与FB/FB间、FB/FB与DEBH/DEBH间的GTV、CTV和PTV重合度差异均无统计学意义(均P＞0.05),而mDIBH/mDIBH与mDIBH/DEBH间、FB/FB与mDIBH/DEBH间的GTV、CTV和PTV重合度差异均有统计学意义(均P＜0.05).结论 ABC辅助实施EB-PBI,两次mDIBH间、两次FB间和两次DEBH间各靶区体积重合度差异不明显,且三者的PTV/PTV重合度均达到较高水平.因此,从靶区重合度的角度,若施照前进行在线摆位误差校正,EB-PBI实施进行呼吸控制的必要性值得商榷.     

The value of magnetic resonance imaging in target volume delineation of base of tongue tumours - A study using flexible surface coils

Introduction

Magnetic resonance imaging (MRI) provides superior diagnostic accuracy over computed tomography (CT) in oropharyngeal tumours. Precise delineation of the gross tumour volume (GTV) is mandatory in radiotherapy planning when a GTV boost is required. CT volume definition in this regard is poor. We studied the feasibility of using flexible surface (flex-L) coils to obtain MR images for MR-CT fusion to assess the benefit of MRI over CT alone in planning base of tongue tumours.

Methods

Eight patients underwent CT and MRI radiotherapy planning scans with an immobilisation device. Distortion-corrected T1-weighted post-contrast MR scans were fused to contrast-enhanced planning CT scans. GTV, clinical target and planning target volumes (CTV, PTV) and organs at risk (OAR) were delineated on CT, then on MRI with blinding to the CT images. The volumetric and spatial differences between MRI and CT volumes for GTV, CTV, PTV and OAR were compared. MR image distortions due to field inhomogeneity and non-linear gradients were corrected and the need for such correction was evaluated.

Results

The mean primary GTV was larger on MRI (22.2 vs. 9.5 cm³, p = 0.05) than CT. The mean primary and nodal GTV (i.e. BOT and macroscopic nodes) was significantly larger on MRI (27.2 vs. 14.4 cm³, p = 0.05). The volume overlap index (VOI) between MRI and CT for the primary was 0.34 suggesting that MRI depicts parts of the primary tumour not detected by CT. There was no significant difference in volume delineation between MR and CT for CTV, PTV, nodal CTV and nodal PTV. MRI volumes for brainstem and spinal cord were significantly smaller due to improved organ definition (p = 0.002). Susceptibility and gradient-related distortions were not found to be clinically significant.

Conclusion

MRI improves the definition of tongue base tumours and neurological structures. The use of MRI is recommended for GTV dose-escalation techniques to provide precise depiction of GTV and improved sparing of spinal cord and brainstem.     

The delineation of target volumes for radiotherapy of lung cancer patients

Purpose

Differences in the delineation of the gross target volume (GTV) and planning target volume (PTV) in patients with non-small-cell lung cancer are considerable. The focus of this work is on the analysis of observer-related reasons while controlling for other variables.

Methods

In three consecutive patients, eighteen physicians from fourteen different departments delineated the GTV and PTV in CT-slices using a detailed instruction for target delineation. Differences in the volumes, the delineated anatomic lymph node compartments and differences in every delineated pixel of the contoured volumes in the CT-slices (pixel-by-pixel-analysis) were evaluated for different groups: ten radiation oncologists from ten departments (ROs), four haematologic oncologists and chest physicians from four departments (HOs) and five radiation oncologists from one department (RO1D).

Results

Agreement (overlap ? 70% of the contoured pixels) for the GTV and PTV delineation was found in 16.3% and 23.7% (ROs), 30.4% and 38.6% (HOs) and 32.8% and 35.9% (RO1D), respectively.

Conclusion

A large interobserver variability in the PTV and much more in the GTV delineation were observed in spite of a detailed instruction for delineation. The variability was smallest for group ROID where due to repeated discussions and uniform teaching a better agreement was achieved.     

CT灌注成像对非小细胞肺癌放疗靶区确定的临床意义

目的探讨CT灌注成像扫描对非小细胞肺癌（NSCLC）行三维适形放疗（3DCRT）时靶区确定的临床意义。方法对36例经病理组织学检查证实为NSCLC患者,先后行胸部常规CT扫描及CT灌注成像扫描。根据成像勾画原发病灶范围,分别称为CT-GTV和CTPI-CTV,由三维治疗计划系统得出GTV具体数值进行比较。结果所有患者均有不同程度差别。CT-GTV平均为133.00cm^3（90～194cm^3）,CTPI-CTV平均为106.60cm^3（67～152cm^3）;CTPI-CTV较CT-GTV缩小19.8%（26.4cm^3）（P=0.00）。GTV减少的主要原因是CT灌注成像能辨别肺不张和肿瘤,因而可以减少肿瘤靶体积并且避免正常组织不必要的勾画。结论CT灌注成像在确定非小细胞肺癌3DCRT靶区方面具有一定临床价值,并由此提高了靶区定位的精确性。     

Consensus on Contouring Primary Breast Tumors on MRI in the Setting of Neoadjuvant Partial Breast Irradiation in Trials

PurposeOur purpose was to present and evaluate expert consensus on contouring primary breast tumors on magnetic resonance imaging (MRI) in the setting of neoadjuvant partial breast irradiation in trials.Methods and MaterialsExpert consensus on contouring guidelines for target definition of primary breast tumors on contrast-enhanced MRI in trials was developed by an international team of experienced breast radiation oncologists and a dedicated breast radiologist during 3 meetings. At the first meeting, draft guidelines were developed through discussing and contouring 2 cases. At the second meeting 6 breast radiation oncologists delineated gross tumor volume (GTV) in 10 patients with early-stage breast cancer (cT1N0) according to draft guidelines. GTV was expanded isotropically (20 mm) to generate clinical target volume (CTV), excluding skin and chest wall. Delineations were reviewed for disagreement and guidelines were clarified accordingly. At the third meeting 5 radiation oncologists redelineated 6 cases using consensus-based guidelines. Interobserver variation of GTV and CTV was assessed using generalized conformity index (CI). CI was calculated as the sum of volumes each pair of observers agreed upon, divided by the sum of encompassing volumes for each pair of observers.ResultsFor the 2 delineation sessions combined, mean GTV ranged between 0.19 and 2.44 cm³, CI for GTV ranged between 0.28 and 0.77, and CI for CTV between 0.77 and 0.94. The largest interobserver variation in GTV delineations was observed in cases with extended tumor spiculae, blood vessels near or markers within the tumor, or with increased enhancement of glandular breast tissue. Consensus-based guidelines stated to delineate all visible tumors on contrast enhanced–MRI scan 1 to 2 minutes after contrast injection and if a marker was inserted in the tumor to include this.ConclusionsExpert-based consensus on contouring primary breast tumors on MRI in trials has been reached. This resulted in low interobserver variation for CTV in the context of a uniform 20 mm GTV to CTV expansion margin.     

Adaptive radiotherapy for invasive bladder cancer: a feasibility study

PURPOSE: To evaluate the feasibility of adaptive radiotherapy (ART) in combination with a partial bladder irradiation. METHODS AND MATERIALS: Twenty-one patients with solitary T1-T4 N0M0 bladder cancer were treated to the bladder tumor + 2 cm margin planning target volume (PTV(CONV)). During the first treatment week, five daily computed tomography (CT) scans were made immediately before or after treatment. In the second week, a volume was constructed encompassing the gross tumor volumes (GTVs) on the planning scan and the five CT scans (GTV(ART)). The GTV(ART) was expanded with a 1 cm margin for the construction of a PTV(ART). Starting in the third week, patients were treated to PTV(ART). Repeat CT scans were used to evaluate treatment accuracy. RESULTS: On 5 of 91 repeat CT scans (5%), the GTV was not adequately covered by the PTV(ART). On treatment planning, there was only one scan in which the GTV was not adequately covered by the 95% isodose. On average, the treatment volumes were reduced by 40% when comparing PTV(ART) with PTV(CONV) (p < 0.0001). CONCLUSION: The adaptive strategy for bladder cancer is an effective way to deal with treatment errors caused by variations in bladder tumor position and leads to a substantial reduction in treatment volumes.     

Impact of FDG-PET on radiation therapy volume delineation in non-small-cell lung cancer

PURPOSE: Locoregional failure remains a significant problem for patients receiving definitive radiation therapy alone or combined with chemotherapy for non-small-cell lung cancer (NSCLC). Positron emission tomography (PET) with [(18)F]fluoro-2-deoxy-d-glucose (FDG) has proven to be a valuable diagnostic and staging tool for NSCLC. This prospective study was performed to determine the impact of treatment simulation with FDG-PET and CT on radiation therapy target volume definition and toxicity profiles by comparison to simulation with computed tomography (CT) scanning alone. METHODS: Twenty-six patients with Stages I-III NSCLC were studied. Each patient underwent sequential CT and FDG-PET simulation on the same day. Immobilization devices used for both simulations included an alpha cradle, a flat tabletop, 6 external fiducial markers, and a laser positioning system. A radiation therapist participated in both simulations to reproduce the treatment setup. Both the CT and fused PET/CT image data sets were transferred to the radiation treatment planning workstation for contouring. Each FDG-PET study was reviewed with the interpreting nuclear radiologist before tumor volumes were contoured. The fused PET/CT images were used to develop the three-dimensional conformal radiation therapy (3DCRT) plan. A second physician, blinded to the results of PET, contoured the gross tumor volumes (GTV) and planning target volumes (PTV) from the CT data sets, and these volumes were used to generate mock 3DCRT plans. The PTV was defined by a 10-mm margin around the GTV. The two 3DCRT plans for each patient were compared with respect to the GTV, PTV, mean lung dose, volume of normal lung receiving > or =20 Gy (V20), and mean esophageal dose. RESULTS: The FDG-PET findings altered the AJCC TNM stage in 8 of 26 (31%) patients; 2 patients were diagnosed with metastatic disease based on FDG-PET and received palliative radiation therapy. Of the 24 patients who were planned with 3DCRT, PET clearly altered the radiation therapy volume in 14 (58%), as follows. PET helped to distinguish tumor from atelectasis in all 3 patients with atelectasis. Unsuspected nodal disease was detected by PET in 10 patients, and 1 patient had a separate tumor focus detected within the same lobe of the lung. Increases in the target volumes led to increases in the mean lung dose, V20, and mean esophageal dose. Decreases in the target volumes in the patients with atelectasis led to decreases in these normal-tissue toxicity parameters. CONCLUSIONS: Radiation targeting with fused FDG-PET and CT images resulted in alterations in radiation therapy planning in over 50% of patients by comparison with CT targeting. The increasing availability of integrated PET/CT units will facilitate the use of this technology for radiation treatment planning. A confirmatory multicenter, cooperative group trial is planned within the Radiation Therapy Oncology Group.     

PET/CT在非小细胞肺癌放疗靶区勾画中的应用及其影响

目的探讨非小细胞肺癌(Non-small cell lung cancer,NSCLC)在放射治疗中,应用PET/CT融合图像勾画靶区对靶体积及正常组织受照剂量的影响。方法 随机选择21例临床分期T_3-4N₀M₀的NSCLC患者,分别根据CT图像和PET/CT图像勾画靶区和危及器官。分别比较基于两种影像资料所得靶区体积的大小差异,及该差异与靶区本身体积的关系;在靶区的剂量达到临床要求的条件下,比较两者的调强放射治疗(IMRT)计划中双肺Vx(即接受大于X剂量照射的肺的体积)、平均剂量(MLD)、心脏剂量和脊髓剂量的差异。结果 85.7%的病例,在CT图像上得到的靶体积(即依据传统CT资料所勾画的靶)比PET/CT大,且两者所勾画出的临床靶区(CTV)之间比较,差异具有统计学意义(P=0.001);计划靶区(PTV)之间比较差异具有统计学意义(P=0.001);两种方法所得到的靶体积差异与靶体积本身的大小呈正相关,肿瘤区(GTV)r=0.96、CTV部分r=0.82、PTV部分r=0.61;依据CT图像的计划中正常肺组织受照射剂量均较PET/CT的大,且两者肺受照20Gy以上剂量的肺体积(V20)之间比较,差异有统计学意义(P=0.017);两者肺的平均受照剂量(MLD)之间比较,差异有统计学意义(P=0.004);两者受照40Gy以上剂量的心脏体积(Vheart)之间比较,差异有统计学意义(P=0.02)。结论 应用PET/CT融合图像勾画靶区能改善靶体积和正常组织的照射剂量。     

Planning target volumes for radiotherapy: how much margin is needed?

Purpose: The radiotherapy planning target volume (PTV) encloses the clinical target volume (CTV) with anisotropic margins to account for possible uncertainties in beam alignment, patient positioning, organ motion, and organ deformation. Ideally, the CTV-PTV margin should be determined solely by the magnitudes of the uncertainties involved. In practice, the clinician usually also considers doses to abutting healthy tissues when deciding on the size of the CTV-PTV margin. This study calculates the ideal size of the CTV-PTV margin when only physical position uncertainties are considered.

Methods and Materials: The position of the CTV for any treatment is assumed to be described by independent Gaussian distributions in each of the three Cartesian directions. Three strategies for choosing a CTV-PTV margin are analyzed. The CTV-PTV margin can be based on: 1. the probability that the CTV is completely enclosed by the PTV; 2. the probability that the projection of the CTV in the beam’s eye view (BEV) is completely enclosed by the projection of the PTV in the BEV; and 3. the probability that a point on the edge of the CTV is within the PTV. Cumulative probability distributions are derived for each of the above strategies.

Results: Expansion of the CTV by 1 standard deviation (SD) in each direction results in the CTV being entirely enclosed within the PTV 24% of the time; the BEV projection of the CTV is enclosed within the BEV projection of the PTV 39% of the time; and a point on the edge of the CTV is within the PTV 84% of the time. To have the CTV enclosed entirely within the PTV 95% of the time requires a margin of 2.8 SD. For the BEV projection of the CTV to be within the BEV projection of the PTV 95% of the time requires a margin of 2.45 SD. To have any point on the surface of the CTV be within the PTV 95% of the time requires a margin of 1.65 SD.

Conclusion: In the first two strategies for selecting a margin, the probability of finding the CTV within the PTV is unrelated to dose variations in the CTV. In the third strategy, the specified confidence limit is correlated with the minimum target dose. We recommend that the PTV be calculated from the CTV using a margin of 1.65 SD in each direction. This gives a minimum CTV dose that is greater than 95% of the minimum PTV dose. Additional sparing of adjoining healthy structures should be accomplished by modifying beam portals, rather than adjusting the PTV. Then, the dose distributions more accurately reflect the clinical compromise between treating the tumor and sparing the patient.     

Physical considerations on discrepancies in target volume delineation

Background and purposeTo compare the delineations and interpretations of target volumes by physicians in different radio-oncology centers.Materials and methodsEleven Swiss radio-oncology centers delineated volumes according to ICRU 50 recommendations for one prostate and one head and neck case. In order to evaluate the consistency of the volume delineations, the following parameters were determined: 1) the target volumes (GTV, CTV and manually expanded PTV) and their extensions in the three main axes and 2) the correlation of the volume delineated by each pair of centers using the ratio of the intersection to the union (called proximity index).ResultsThe delineated prostate volume was 105±55 cm³ for the CTV and 218±44 cm³ for the PTV. The delineated head and neck volume was 46±15 cm³ for the GTV, 327±154 cm³ for the CTV and 528±106 cm³ for the PTV. The mean proximity index for the prostate case was 0.50±0.13 for the CTV and 0.57±0.11 for the PTV. The proximity index for the head and neck case was 0.45±0.09 for the GTV, 0.42±0.13 for the CTV and 0.59±0.06 for the PTV.ConclusionsLarge discrepancies between all the delineated target volumes were observed. There was an inverse relationship between the CTV volume and the margin between CTV and PTV, leading to less discrepancies in the PTV than is the CTV delineations. There was more spread in the sagittal and frontal planes due to CT pixel anisotropy, which suggests that radiation oncologists should delineate the target volumes not only in the transverse plane, but also in the sagittal and frontal planes to improve the delineation by allowing a consistency check.     

Consistency in seroma contouring for partial breast radiotherapy: impact of guidelines

PURPOSE: Inconsistencies in contouring target structures can undermine the precision of conformal radiation therapy (RT) planning and compromise the validity of clinical trial results. This study evaluated the impact of guidelines on consistency in target volume contouring for partial breast RT planning. METHODS AND MATERIALS: Guidelines for target volume definition for partial breast radiation therapy (PBRT) planning were developed by members of the steering committee for a pilot trial of PBRT using conformal external beam planning. In phase 1, delineation of the breast seroma in 5 early-stage breast cancer patients was independently performed by a "trained" cohort of four radiation oncologists who were provided with these guidelines and an "untrained" cohort of four radiation oncologists who contoured without guidelines. Using automated planning software, the seroma target volume (STV) was expanded into a clinical target volume (CTV) and planning target volume (PTV) for each oncologist. Means and standard deviations were calculated, and two-tailed t tests were used to assess differences between the "trained" and "untrained" cohorts. In phase 2, all eight radiation oncologists were provided with the same contouring guidelines, and were asked to delineate the seroma in five new cases. Data were again analyzed to evaluate consistency between the two cohorts. RESULTS: The "untrained" cohort contoured larger seroma volumes and had larger CTVs and PTVs compared with the "trained" cohort in three of five cases. When seroma contouring was performed after review of contouring guidelines, the differences in the STVs, CTVs, and PTVs were no longer statistically significant. CONCLUSION: Guidelines can improve consistency among radiation oncologists performing target volume delineation for PBRT planning.     

中晚期非小细胞肺癌放疗临床靶区设置的必要性

目的:探讨中晚期非小细胞肺癌放疗时临床靶区设置的必要性。方法:2006年－2012年福建省肿瘤医院177例经病理组织学和(或)细胞学确诊的中晚期非小细胞肺癌患者接受三维适形放疗或者调强放疗,根据靶区勾画原则分为不勾画肺部肿瘤临床靶区组:勾画肿瘤靶区（GTV）和计划靶区（PTV）,勾画肺部肿瘤临床靶区组:勾画肿瘤靶区（GTV）、临床靶区（CTV）和计划靶区（PTV）。两组肺部病灶分割剂量200~220 cGy/次,5次/周,肺部病灶放疗剂量 DT 5 600~6 600 cGy。两组资料经统计学分析具有可比性。结果:不勾画肺部肿瘤临床靶区组和勾画肺部肿瘤临床靶区组相比,肺部肿瘤平均剂量分别为59.6 Gy、60.7 Gy。两组近期总有效率（CR+PR）分别为76.30%、83.33%（P=0.230）。1、2、3年无进展生存率分别为52.98%、35.35%、24.3%和38.95%、24.33%、11.5%（P=0.360）。1、2、3年总生存率分别为69.9%、45.3%、30.8%和62.18%、37.59%、26.58%（P=0.573）。1、2、3年远处转移率分别为61.07%、40.27%、30.4%和43.55%、32.03%、27.56%（P=0.481）。两组复发率分别为38.52%、59.52%,均为野内复发。两组放射性肺炎发生率分别为16.30%、33.33%（P=0.017）,放射性食管炎发生率分别为18.52%、21.43%（P=0.414）,骨髓抑制发生率分别为38.52%、33.33%（P=0.338）,两组均未出现3级以上放射性肺炎。结论:不勾画肺部肿瘤临床靶区使肺部放疗区域减少,治疗后并不减少局部肿瘤的无进展生存和总生存率,但明显减少放射性肺炎的发生率。     

Motion and deformation of the target volumes during IMRT for cervical cancer: What margins do we need?

BACKGROUND AND PURPOSE: For cervical cancer patients the CTV consists of multiple structures, exhibiting complex inter-fraction changes. The purpose of this study is to use weekly MR imaging to derive PTV margins that accommodate these changes. MATERIALS AND METHODS: Twenty patients with cervical cancer underwent a T2-weighted MRI exam before and weekly during IMRT. The CTV, GTV and surrounding organs were delineated. PTV margins were derived from the boundaries of the GTV and CTV in the six main directions and correlated with changes in the volumes of organs at risk. RESULTS: Around the GTV a margin of 12, 14, 12, 11, 4 and 8mm to the anterior, posterior, right lateral, left lateral, superior and inferior directions was needed. The CTV required margins of 24, 17, 12, 16, 11 and 8mm. The shift of the GTV and CTV in the AP directions correlated weakly with the change in rectal volume. For the bladder the correlations were even weaker. CONCLUSIONS: We used weekly MRI scans to derive inhomogeneous PTV margins that accommodate changes in GTV and CTV. The weak correlations with rectum and bladder volume suggest that measures to control filling status of these organs may not be very effective.     

食管癌调强技术根治性放疗后局部区域失败与靶区剂量体积关系研究

目的 研究食管癌调强技术根治性放疗后局部区域失败与靶区剂量体积关系影响.方法 随机选取70例食管癌患者,按照照射范围不同分为两种:累及野照射(IFI)和选择性淋巴引流区预防照射(ENI),根据术后随访数据与复查资料确认是否为局部区域失败.将其分为A、B两组.其中A组为局部区域失败共38例,B组为非局部区域失败共32例.通过对比两组患者基本资料、靶剂量、体积参数;分析全组生存率、不同照射范围时靶体积剂量、体积参数;并分别对A、B两组不同照射范围时靶体积剂量、体积参数进行了对比分析.结果 通过对比两组患者的靶区剂量参数、体积参数,发现A、B两组在GTV、CTV、PTV的剂量参数与体积参数方面差异无统计学意义(P>0.05).全组进行了不同照射范围时ENI者与IFI者GTV、CTV、PTV的剂量参数对比,发现差异显著均有统计学意义(P<0.05);体积参数对比CTV的V55、V50和PTV的V60、V55、V50差异显著均有统计学意义(P<0.05).其中A组ENI者与IFI者的CTV的剂量参数D98%、D95%、PTV的剂量参数D98%、D95%、D50%差异显著,均有统计学意义(P<0.05);体积参数值对比可见两组CTV的V55和PTV的V60、V55、V50比较差异显著,均有统计学意义(P<0.05);B组中ENI者与IFI者的GTV、CTV、PTV的剂量参数D98%、D95%、D50%、D2%差异显著,均有统计学意义(P<0.05);体积参数值对比可见两组PTV的V60、V55、V50比较差异显著,均有统计学意义(P<0.05).结论 食管癌调强技术根治性治疗中,建议处方剂量所包含的靶体积不低于95%,使用淋巴引流区的预防照射(ENI)在一定程度上可提高靶区剂量体积,可能有效减少局部区域失败,提升食管癌放疗的局部控制率.     

基于四维CT原发性肝癌内靶体积的确定及剂量学研究

目的 应用四维CT确定原发性肝癌内靶体积(ITV),比较常规三维计划与四维计划、呼吸门控计划的靶区体积及剂量学差异.方法 选择12例肝癌患者,行四维CT扫描,在10个时相的CT图像中分别勾画GTV、CTV和危及器官.根据PTV_(3D)、PTV_(40)、PTV_(Gating)为每例患者分别设计三维计划、四维计划、呼吸门控计划.PIV_(3D)由CTV外扩常规的安全边界得到,PTV_(4D)由10个时相的CTV融合形成的ITV_(40)外扩摆位误差(SM)得到,PTV_(Gating)由呼气末3个时相的CTV融合形成的ITV_(Gating)外扩SM得到.比较3套计划中靶区体积和危及器官剂量学的差异.结果 12例患者PTV_(3D)均显著大于PTV4D及PTV_(Gating),其中5例患者PTV_(3D)较PTV_(4D)遗漏了部分靶区.四维计划、呼吸门控计划中危及器官的受照剂量均较三维计划降低,以肝最为显著.在不增加正常组织受照剂量的前提下,四维计划的处方剂量可由三维计划的(50.8±2.0)Gy提升至(54.7±3.3)Cy,而呼吸门控计划可进一步提升至(58.0±3.9)Gy.结论 应用四维CT可在三维适形放疗基础上缩小肝癌靶区,在保证覆盖肿瘤的同时减少正常组织的受照剂量,并提升靶区剂量;门控放疗可进一步缩小靶区,更有利于保护正常组织,尤其是对于肝呼吸动度较大的病例.     

Maximum-intensity volumes for fast contouring of lung tumors including respiratory motion in 4DCT planning

PURPOSE: To assess the accuracy of maximum-intensity volumes (MIV) for fast contouring of lung tumors including respiratory motion. METHODS AND MATERIALS: Four-dimensional computed tomography (4DCT) data of 10 patients were acquired. Maximum-intensity volumes were constructed by assigning the maximum Hounsfield unit in all CT volumes per geometric voxel to a new, synthetic volume. Gross tumor volumes (GTVs) were contoured on all CT volumes, and their union was constructed. The GTV with all its respiratory motion was contoured on the MIV as well. Union GTVs and GTVs including motion were compared visually. Furthermore, planning target volumes (PTVs) were constructed for the union of GTVs and the GTV on MIV. These PTVs were compared by centroid position, volume, geometric extent, and surface distance. RESULTS: Visual comparison of GTVs demonstrated failure of the MIV technique for 5 of 10 patients. For adequate GTV(MIV)s, differences between PTVs were <1.0 mm in centroid position, 5% in volume, +/-5 mm in geometric extent, and +/-0.5 +/- 2.0 mm in surface distance. These values represent the uncertainties for successful MIV contouring. CONCLUSION: Maximum-intensity volumes are a good first estimate for target volume definition including respiratory motion. However, it seems mandatory to validate each individual MIV by overlaying it on a movie loop displaying the 4DCT data and editing it for possible inadequate coverage of GTVs on additional 4DCT motion states.