高能X射线肿瘤照射靶区的生物学位置的实验模拟研究

目的:研究50MV高能X射线照射患者时光核反应产生的正电子发射核<'11>C、<'15>O在PET的显象技术及信息,探讨用该信息定量研究照射的肿瘤生物靶区准确度和剂量分布情况.方法:50 MV的X射线照射圆柱体模后快速置于PET上扫描显像和数据处理,确定射野轨迹和照射区大小并与物理射野大小比较,确定<'11>C活度分布...     

用45MV轫致辐射在肿瘤组织产生的光核反应和PET显像研究肿瘤的乏氧情况

目的:提出了一种新的肿瘤乏氧研究方法——光核反应PET显像法,并用放置在同一房间的LA45加速器和PET实验研究该方法。材料与方法:"光核反应PET显像法"研究肿瘤乏氧的原理是由于血液中80%的成分为氧(16O),利用高能光子(如45 MV)辐照人体肿瘤诱发的光核反应16O(γ,n)15O产生的15O的PET显像位置和活度分布,分析确定肿瘤靶区内氧(16O)的分布和肿瘤的血流灌注信息,继而推测肿瘤内部的乏氧(16O)情况和位置分布。选择腹部肿瘤、肝癌、肺癌和肾癌患者5人,肿瘤大小范围从10 cm×10 cm～1.2 cm×1.0 cm,按常规的3DCRT规范对肿瘤部位实施均匀剂量的照射治疗,其中在第一分次治疗时,用LA45加速器45 MV X射线按TPS方案行3野～5野2 Gy～3 Gy剂量照射,随后立即将患者快速转移(大约2 min)至同一治疗室的PET进行20 min的15O扫描显像,对扫描结果进行必要的衰减校正等分析处理,获得15O的在照射位置的活度分布,进而确定肿瘤部位氧(16O)的分布,通过与治疗计划TPS的结果比较,便可推知肿瘤内部的乏氧情况和照射位置是否准确等。结果和讨论:对较大的实体肿瘤,该方法能很好分析出肿瘤内是否存在乏氧。这可能是因为较大实体的肿瘤内容易形成乏氧区,生成的15O活度密度分布差容易区分。对肿瘤病灶小(CTV小于2 cm)且处于密度相对低的组织如肺,15O不能形成有效显像。这可能由于肿瘤很小,且在组织密度低的、毛细血管发达的肺部,这样不仅生成的15O活度密度(单位体积的15O活度)相对较少,而且生成的15O也可能很容易由发达的毛细血管冲洗到肿瘤外部并被稀释。由于15O半衰期很短,为了减少时间,一般设计3野2 Gy照射计划,这样适形度稍差些,更不利的是容易在皮肤表面形成较强的显像,如果单次剂量能给到3 Gy,可以设计5个野,这样既能有清晰的显像,又有较好的适形度,更重要的是不会在皮肤表面产生很强的干扰显像。     

肺癌肺内肿瘤不同能量三维适形放疗的比较

目的:研究6 MV和15 MV X射线对肺癌肺内肿瘤三维适形放疗肿瘤组织、危及器官及正常组织剂量的影响。方法:选择11例肺癌肺内肿瘤患者,对每例患者分别采用6 MV和15 MV X射线进行三维适形放疗计划设计,同一患者的两个计划均使用相同的布野方案和剂量体积约束。比较两组计划的计划靶区、危及器官及正常组织的剂量分布。结果:6MV和15 MV两种能量X线三维适形放疗计划计划靶区的剂量分布、均匀性、适形度的差异无显著性意义(P>0.05),危及器官脊髓、食管、心脏,正常组织肺的剂量分布无显著性意义(P>0.05)。结论:肺癌肺内肿瘤6 MV、15 MV三维适形放疗剂量分布无明显差异,三维适形放疗能量用6 MV,不主张用15 MV。     

不同剂量X射线对人外周血有核细胞DNA及精子DNA损伤的比较

目的:应用单细胞凝胶电泳技术检测不同剂量X射线对人离体外周血有核细胞DNA及精子DNA的损伤,评估外周血有核细胞及精子在高剂量X射线照射后DNA的损伤程度.方法:采用血常规正常的人外周血和采集精液常规正常的人精液,用能量为6MV的X射线给予0Gy,2Gy,4Gy,6Gy,8Gy,10Gy的剂量照射.照射后1h内进行单细...     

核素影像设备的进展

γ相机和单光子发射计算机断层显像术(SPECT)只能进行常规单光子显像,正电子发射断层显像术(PET)和双探头SPECT既能进行单光子显像,又能进行正电子符合显像.PET/CT系统的出现不仅提供高质量的衰减校正图像,保证了正电子显像校正的可靠性,而且能进行同机图像融合,提高了影像定位诊断的准确性.该文简要介绍了核医学影像设备发展历程,PET和PET/CT的原理以及在临床的应用.     

PET—CT联合扫描可增加肺癌患者放疗的准确率

2005年3月1日美国肿瘤和放射治疗学协会主办的，国际肿瘤放射学、生物学及物理学杂志上刊登了一个新的研究成果，利用正电子发射X线照相术（PET）加计算机X线照术（CT）可减少肺癌患者正常组织的X线照射量．     

热释光剂量片测量肺部肿瘤放疗剂量的方法

目的:研究LiF(Mg、Cu、P)热释光剂量片(TLD)在临床肿瘤放疗测量要求的筛选方法。方法:应用~(60)Coγ射线和6 MV X射线,开展TLD分散性、重复性和剂量响应实验,筛选出符合临床肿瘤放疗要求的TLD。根据临床放射治疗需要,将筛选出符合临床要求的TLD分别用称量纸封装并依次编号粘贴在仿真模体处,将粘贴有TLD模体置于6 MV X射线加速器照射,验证仿真模体肺部靶区外的剂量。结果:Li F(Mg、Cu、P)TLD重复性和分散性误差控制在±3%以内;用6MV X射线照射粘贴有TLD的模体,测量的TLD剂量值和治疗计划系统值的偏差与TLD所处位置剂量大小有关,当剂量大于62 mGy时,两者符合较好,其差别小于5%;当剂量远小于62 mGy时,其差别明显偏大。结论:在合适剂量范围内用TLD验证肺部肿瘤放疗剂量的方法准确可靠、经济适用,得到国际原子能机构的认可,可广泛应用于肿瘤放疗的剂量测量。     

不同能量X线胸段食管癌调强放疗计划的剂量学研究

目的:研究不同能量X射线治疗胸段食管癌调强放疗(IMRT)计划的剂量学差异。方法:选择l2例胸段食管癌患者,在ADAC Pinnacle3三维治疗计划系统(TPS)中分别采用6 MV、10 MV和15 MV X线给每位患者设计三个调强放疗计划,在规定计划靶区(PTV)至少达到95%处方剂量的前提下,根据剂量体积直方图(DVH)比较三种计划的靶区剂量分布及脊髓、肺、心脏等正常组织受照射剂量的差异。结果:三种计划中靶区的最大剂量、最小剂量、平均剂量及靶区适形度指数、均匀性指数均无明显差异,但15 MV计划高剂量覆盖程度大于6 MV和10 MV计划,脊髓、双肺及心脏受照剂量都在可耐受的范围内,差异也无统计学意义(P>0.05)。结论:6 MV、10 MV、15 MV X射线都能满足胸段食管癌临床调强放疗需求。     

局部晚期胰腺癌三维适形放射治疗与γ射线体部立体定向放射治疗加量疗效分析

目的回顾性分析局部晚期胰腺癌患者接受直线加速器X射线常规三维适形放射治疗（简称放疗）（3D-CRT组）与常规适形放疗加γ射线体部立体定向放疗加量治疗（SBRT加量组）之间的疗效差异。方法 40例局部晚期胰腺癌患者,其中男性22例,女性18例;年龄46～83岁,中位年龄72岁。3D-CRT组28例,SBRT加量组12例。ⅡA期（T3N0）6例,ⅡB（T1-3N1）5例,Ⅲ（T4N0-1）29例。单纯3D-CRT组计划总剂量46～50 Gy。SBRT加量组的常规适形放疗剂量计划为40 Gy（20次）,然后采用SBRT追加加量16Gy（8次）。结果中位随访时间27个月（随访时间3～44个月）,全组适形放疗中位肿瘤靶体积（GTV）为75.3 mL（GTV为17.5～191.7 mL）,中位CTV为349.7 mL（CTV为114.4～727.9 mL）。SBRT加量CT定位时中位GTV为47.5mL（GTV为11.7～96.9mL）。3D-CRT组中位照射剂量46Gy（照射剂量18～50Gy）,SBRT组适形放疗中位照射剂量40 Gy（照射剂量40～46 Gy）,γ射线立体定向放疗加量中位照射剂量16 Gy（照射剂量14～20 Gy）。全组中位生存时间8.4个月（生存时间1.4～35.1个月）,3D-CRT组与SBRT组的中位生存时间分别为8.2个月（生存时间1.4～21.2个月）、17.7个月（生存时间2.9～35.1个月）,P〉0.05。两组治疗相关急性和后期副反应差异无统计学意义。结论对于局部晚期胰腺癌患者,适形放疗加γ射线立体定向放疗加量耐受性好,有提高生存期的趋势。能否真正地提高生存率,有待进一步扩大样本研究。     

11C-标记PET显像剂的合成及应用

正电子核素:碳-11广泛应用于氨基酸、脂肪酸、受体的配体和神经递质等分子标记,其标记的PET显像剂在生物医学和药理学研究中实现真正意义上的分子生物学显像.利用PET显像临床应用于探查肿瘤、脑血流、代谢、蛋白质合成和神经递质功能活动,在基础科学和临床研究中具有非常重要的意义.     

A biologically-based algorithm for companding computerized tomography (CT) images

Computerized Tomography (CT) images are High Dynamic Range (HDR) images of the X-ray attenuation coefficients of the body's tissues. The inability to see abnormalities in tissues with marked differences in their X-ray attenuation coefficients, in a single CT window, poses a significant clinical problem in radiology. In order to provide proper contrast, which reveals all the required clinical details within each specifically imaged tissue, a single CT slice must be viewed by a radiologist four times: the first viewing focuses on the lung window; the second viewing focuses on the soft tissues window; the third viewing focuses on the liver window; and the fourth viewing focuses on the bone window. In order to enhance the ability to perform a complete diagnosis, while decreasing diagnostic time, we developed the BACCT (Biologically-based Algorithm for Companding CT images) method. Our algorithm compresses and expands (compands) the HDR CT image into a single, low dynamic range image. Before performing the companding procedure, unique processing is required which involves operations that enhance and stretch the image. The performance of our algorithm has been demonstrated on a large repertoire of CT body images. All the clinically required CT information is exposed in each CT slice in a single image. The algorithm compands the CT images in a fully automatic way. Collaborating radiologists have already tested the results of our algorithmic method, and reported that the images seem to provide all the necessary information. However, clinical tests for statistical reliability are still required.     

Artefacts of PET/CT images

Positron emission tomography (PET) is a non-invasive imaging modality, which is clinically widely used both for diagnosis and accessing therapy response in oncology, cardiology and neurology.Fusing PET and CT images in a single dataset would be useful for physicians who could read the functional and the anatomical aspects of a disease in a single shot.The use of fusion software has been replaced in the last few years by integrated PET/CT systems, which combine a PET and a CT scanner in the same gantry. CT images have the double function to correct PET images for attenuation and can fuse with PET for a better visualization and localization of lesions. The use of CT for attenuation correction yields several advantages in terms of accuracy and patient comfort, but can also introduce several artefacts on PET-corrected images.PET/CT image artefacts are due primarily to metallic implants, respiratory motion, use of contrast media and image truncation. This paper reviews different types artefacts and their correction methods.PET/CT improves image quality and image accuracy. However, to avoid possible pitfalls the simultaneous display of both Computed Tomography Attenuation Corrected (CTAC) and non corrected PET images, side by side with CT images is strongly recommended.     

衍射增强成像的生物医学应用研究进展

【摘要】X射线相衬成像技术是近年来研究开发的高衬度和高空间分辨率的新型成像技术,和传统X射线成像技术相比,它可满足生物软组织微观成像条件,获得软组织的丰富内部微观结构细节。衍射增强成像（DEI）是相衬成像技术的研究热点。利用基于DEI的信息提取和CT重建等图像处理技术,能够获得生物样品高质量图像及三维精细微观结构,更好地显示样品内部的结构和细节。结合DEI的理论和图像处理方法介绍了DEI技术的生物医学应用进展。     

A Study on Usefulness Evaluation of SUV Measured in Mini-PACS for Each One of PET/CT Equipment

To save and analyze the data from a positron emission tomography/computed tomography (PET/CT) scan, it is sometimes important to use a server away from the workstation of the equipment or to install and operate mini-picture archiving and communication system (PACS). Mini-PACS was developed to save the data from a scan and measure the standard uptake value (SUV) in PACS that could be measured only in PET/CT equipment manufactured by many companies. Against this background, this study examined whether the SUV measured in PET/CT equipment was the same value in mini-PACS. This study evaluated Biograph 16 and Biograph 40 manufactured by SIEMENS and Discovery Ste 8 manufactured by GE, all of which are installed in this hospital. The SUV of the aorta of 30 patients, who had undergone an ¹⁸F-FDG whole body PET scan in the period from February to October 2012, was measured at the height of the liver and mediastinum. In the mini-PACS program, the SUV was also measured and analyzed in an image with the same phase. According to the study results, the coefficient of the SUV of the liver in PET/CT equipment and mini-PACS was 0.99, 0.98, and 0.64 in Biograph 16, Biograph 40, and Discovery Ste 8, respectively, where the coefficient of the SUV of aorta was 0.98, 0.98, and 0.66 in Biograph 16, Biograph 40, and Discovery Ste 8, showing a positive correlation in all equipment.     

PET/CT成像原理、优势及临床应用

目的:探讨PET/CT成像原理、优势及临床应用。方法:从PET/CT定义开始,相继介绍原理、主要参数、优势及临床应用。结果:PET/CT能将PET(功能代谢显像)和CT(解剖结构显像)两种先进的影像技术有机地结合在一起,让具有不同特征的影像在同一平台显示、解读、对比与分析,具有广泛的应用前景。结论:PET/CT代表了当今医学影像仪器发展的最高水平,是目前医学影像诊断技术最为理想的结合。     

Robust feature-based registration using a Gaussian-weighted distance map and brain feature points for brain PET/CT images

Feature-based registration is an effective technique for clinical use, because it can greatly reduce computational costs. However, this technique, which estimates the transformation by using feature points extracted from two images may cause misalignments, particularly in brain PET and CT images that have low correspondence rates between features due to differences in image characteristics. To cope with this limitation, we propose a robust feature-based registration technique using a Gaussian-weighted distance map (GWDM) that finds the best alignment of feature points even when features of two images are mismatched. A GWDM is generated by propagating the value of the Gaussian-weighted mask from feature points of CT images and leads the feature points of PET images to be aligned on an optimal location even though there is a localization error between feature points extracted from PET and CT images. Feature points are extracted from two images by our automatic brain segmentation method. In our experiments, simulated and clinical data sets were used to compare our method with conventional methods such as normalized mutual information (NMI)-based registration and chamfer matching in accuracy, robustness, and computational time. Experimental results showed that our method aligned the images robustly even in cases where conventional methods failed to find optimal locations. In addition, the accuracy of our method was comparable to that of the NMI-based registration method.     

用于儿科PET/CT检查的参数优化选择方法

目的 目前儿科β-2-[F]氟-2-脱氧-D-葡萄糖（18F-FDG）剂量和采集时间一般是按照成人的参数推算出来.本研究目的是对在不影响图像诊断质量的前提下,行儿科正电子发射型计算机断层显像（PET）/CT检查时,缩短采集时间或降低18F-FDG注射用量的可行性进行初步研究.方法 对36例患者（体质量为13～89 kg,平均体质量（46.51±5.63） kg;年龄3～14岁,平均年龄（9.22±3.16）岁）行36次全身18F-FDG PET/CT扫描,按照5.3 MBq/kg（0.14 mCi/kg）计算注射18F-FDG,采用VIP record采集模式,180 s/视野（FOV）;对于每次检查,VIP record记录的数据按照采集时间的减少（160、140、120、100、80、60 s/FOV的数据按照180 s/FOV的数据来模拟计算）,分别被缩减以形成不同采集时间下的图像.随机挑选168幅PET图像以及相对应的CT图像,通过6位影像学专家阅片,对全身存在的病灶进行分析,分别对颈部、胸部、腹部、骨等部位病灶的符合率进行对比,并对主观可信度以及客观准确度进行全面评估.结果 所有检查均以最大采集时间作为分级标准和检查准确度的参考标准.对于体质量＞30 kg的受检者,当采集时间＞120 s/FOV时,所有病灶均可以检测出来,采用120 s/FOV以下的参数进行采集时,病灶检测准确度会大大降低;对于体质量＜30 kg的受检者,当采集时间＞140s/FOV时,所有病灶均可以检测出来,采用140 s/FOV以下的参数进行采集时,病灶检测准确度会大大降低.结论 应用GE Discovery STE PET/CT行儿科检查时,采用减少18F-FDG用量替代减少采集时间,如果采用180s/FOV时,对于体质量＞30 kg的受检者,18F-FDG的用量可降低33.33％;对于体质量＜30 kg的受检者,18F-FDG的用量可降低22.22％,而且不会损失图像诊断质量.所需扫描全部时间的减少意味着可以减少运动伪影,提高受检者舒适度以及减少所需镇静的时间;另外,通过减少18F-FDG用量,还可降低受辐射的风险     

Development of dose delivery verification by PET imaging of photonuclear reactions following high energy photon therapy

A method for dose delivery monitoring after high energy photon therapy has been investigated based on positron emission tomography (PET). The technique is based on the activation of body tissues by high energy bremsstrahlung beams, preferably with energies well above 20 MeV, resulting primarily in 11C and 15O but also 13N, all positron-emitting radionuclides produced by photoneutron reactions in the nuclei of 12C, 16O and 14N. A PMMA phantom and animal tissue, a frozen hind leg of a pig, were irradiated to 10 Gy and the induced positron activity distributions were measured off-line in a PET camera a couple of minutes after irradiation. The accelerator used was a Racetrack Microtron at the Karolinska University Hospital using 50 MV scanned photon beams. From photonuclear cross-section data integrated over the 50 MV photon fluence spectrum the predicted PET signal was calculated and compared with experimental measurements. Since measured PET images change with time post irradiation, as a result of the different decay times of the radionuclides, the signals from activated 12C, 16O and 14N within the irradiated volume could be separated from each other. Most information is obtained from the carbon and oxygen radionuclides which are the most abundant elements in soft tissue. The predicted and measured overall positron activities are almost equal (-3%) while the predicted activity originating from nitrogen is overestimated by almost a factor of two, possibly due to experimental noise. Based on the results obtained in this first feasibility study the great value of a combined radiotherapy-PET-CT unit is indicated in order to fully exploit the high activity signal from oxygen immediately after treatment and to avoid patient repositioning. With an RT-PET-CT unit a high signal could be collected even at a dose level of 2 Gy and the acquisition time for the PET could be reduced considerably. Real patient dose delivery verification by means of PET imaging seems to be applicable provided that biological transport processes such as capillary blood flow containing mobile 15O and 11C in the activated tissue volume can be accounted for.