PET图像定量计算中的误差分析

目的分析PET影像中的误差成分,以期为分析PET定量计算精度提供思路.材料与方法PET,质控模型,18 FFDG,在5个剂量用2D方式采集数据.计算18 F-FDG均匀分布区域像素计数均值和标准差,曲线拟合.结果综合误差平方随信号变化呈二次曲线型.误差成分可分为三部分(1)与随机符合相关的成分正比于信号强度;(2)与放射性统计涨落相关的成分正比于信号强度平方根;(3)其它成分与信号强度无关.结论和γ照相机和SPECT图像中的信噪比随信号源强度一直增加不同,PET图像中特有的随机符合误差使信噪比随信号源强度的增加速度逐渐减慢.     

部分容积效应对双探头符合探测图像的影响

目的 探讨双探头符合探测(DHC)图像中热灶的部分容积效应。方法 双探头符合探测设备：GE Hawkeye。模型：东芝AZ-618 ECT模型。核素：^18F-脱氧葡萄糖(FDG)，活度为204-15MBq，分18次扫描。图像重建：OSEM，Hannimg后滤波。由模型热灶区的重建数据确定热灶的恢复系数及半高宽，分析部分容积效应。结果 ①恢复系数随热灶增大而减小；②同一热灶的恢复系数随感兴趣区增大而减小；③热灶恢复系数随其实际放射性浓度增高而降低；④热灶半高宽随其实际放射性浓度增加而展宽。结论 DHC图像的部分容积效应随病灶减小和病灶放射性浓度增加而增强。     

用双探头符合探测计算FDG图像像素的放射性浓度

目的 探讨由双探头SPECT符合探测(DHC)图像像素计数值确定体内放射性浓度的方法。方法 利用模型确定定标系数，将图像像素计数转换成放射性浓度。在模型中注入脱氧葡萄糖(FDG)水溶液，对18种活度(15．15～204．33MBq)的模型分别进行扫描。结果①由探测单计数率确定定标系数，其关系满足1个四阶多项式。②由图像像素的累积计数、采集时间及定标系数确定像素的放射性浓度，其关系可以一经验公式表示。结论 建立了计算病灶放射性浓度的方法，为DHC图像定量分析提供依据。     

患者移动对双探头心肌灌注断层采集的影响

目的探讨双探头ＳＰＥＣＴ仪心肌灌注断层采集中患者身体移动产生的影响。方法２只探头置成９０°夹角,双探头采集９０°,单探头采集１８０°（关闭１只探头）。心肌灌注断层采集中移动心肌模型模拟患者移动,Ｘ和Ｙ分别移动１个、２个和３个像素。采用移动探测软件对原始图像进行移动测试,图像重建后进行靶心图分析。结果在双探头采集中,Ｙ方向模型的１次移动相当于出现３次移动;Ｘ方向的１次移动同样会导致多次移动,但程度与探头平面和Ｘ轴的夹角有关。在Ｙ方向,单探头２个像素的移动、双探头１个像素的移动导致靶心图出现心尖计数下降。Ｘ方向移动的影响与探头平面和Ｘ轴的夹角有明显关系。在实验的２个移动位置中,３１５°位置１个像素的移动使单探头靶心图的心壁、双探头的心壁和心尖出现计数下降,单探头在２７０°位置的移动影响较小。结论双探头心肌灌注采集过程中患者移动的影响比用单探头时显著。     

利用符合探测技术提高99mTc-MIBI/18F-FDG双核素显像成功率

目的评价符合探测技术对提高99mTc-MIBI/18F-FDG双核素显像成功率的作用。资料与方法在218例双核素心肌显像中,56例心肌代谢图像质量不满意,改用双探头符合探测采集图像。结果 56例心肌代谢图像质量不满意改用灵敏度更高的双探头符合探测采集后,41例获得了能够用于诊断的图像,显像成功率由74.3%提高到93.1%,差异有统计学意义(χ2=7.899,P<0.05)。结论心肌代谢显像的图像质量可能受多种因素的影响,提高探测灵敏度可以提高心肌代谢显像的成功率。     

^18F—FDG双探头符合探测显像诊断恶性肿瘤的初步应用

目的 :探讨 18F -FDG双探头符合探测对恶性肿瘤诊断的价值。材料和方法 :2 2例原发及转移瘤患者接受了18F FDG双探头符合探测显像 ,及CT、超声检查 ,对照病理证实结果比较分析了几种影像技术的诊断效率。结果 :18F FDG双探头符合探测、CT、超声检出肿瘤的准确率分别是 94% ,69% ,69%。个别分化程度较高或太小的病灶出现18F FDG显像假阴性 ;炎性病灶可造成假阳性表现。结论 :18F FDG双探头符合探测对肿瘤原发及转移灶检测方面有较高的价值 ,但需与其他临床资料综合分析得出结论。     

符合线路显像与PET显像中SUV的比较研究

目的比较符合线路显像标准摄取值(SUV)与PET显像的SUV。方法用双探头符合显像仪及PET对模型显像，分别采用不同的重建算法重建，测定图像上热灶的SUV。结果对直径小于30mm热灶，相同大小时，PET、得到的SUV高于符合线路显像；无论对PET还是符合线路显像，随热灶大小增加SUV增加；SUV与重建算法有关；选取的感兴趣区(ROI)越大，获得的SUV越小；由PET图像获得的热灶SUV可见，当热灶大于2倍的系统分辨率时，SUCmax接近热灶的真实值(SUVmax)。结论符合线路显像的SUV低于PET显像；病灶大小、重建算法、ROI大小均影响SUV。     

双探头符合线路技术和检测肿瘤的价值

双探头符合线路(DHC)显像技术的不断成熟和广泛应用,使核医学显像技术在诊断肿瘤方面有了新的发展。由于双探头符合线路在图像处理方面采用了符合探测的预先分组最大期望值图像重建(COSEM)方法(迭代重建法)代替了常用的滤波反投影法(FBP),使图像效果有了明显改善。并且,采用CT或137Cs等放射源在发射显像之前或之后作透射显像以对图像进行衰减校正,对病灶的检出以及图像效果均有较大益处。近来许多研究采用CT等影像技术与SPECT图像进行同机或非同机图像融合处理,对临床判定病灶部位有很大帮助。     

双探头投影偏差所致伪影的识别与校正

目的 探讨双探头ＳＰＥＣＴ仪采集中,由于投影位置偏差使２组图像连接处出现偏移,造成图像伪影与偏差的识别和校正,方法 （１）模型采集;２只探头置成９０°（Ｌ模式）或１８０°（Ｈ模式）夹角,内插球形冷区的Ｊａｓｚｃｚａｋ模型和心肌灌注模型采集。用单探头采集的方法模拟投影偏差,关闭１只探头,在采集全过程的１／２处移动模型,（２）偏差探测：方法一是２只探头在同一角度采集点源图像,计算了２幅点源矩心的偏差;     

符合探测显像中放射性浓度和病灶大小对病灶/本底比值的影响

目的 探讨双探头SPECT符合探测显像中病灶／本底(L/B)比值的影响因素及其校正方法。方法 ①模型研究：分析模型的符合探测显像中不同^18F—脱氧葡萄糖(FDG)对比度(即阳模区或病灶与本底^18F—FDG放射性浓度之比)、不同直径大小阳模柱体对应的L/B比值；②临床研究：分析8例患者29个良、恶性病灶的L/B比值，井探讨其校正方法。结果 ^18F—FDG对比度和物体直径大小均会影响L/B比值测定，校正病灶大小可明显提高诊断准确性。结论 在双探头SPECT符合探测显像中，应充分考虑病灶大小对L/B比值的影响，必要时应加以校正。     

Image fusion using an integrated, dual-head coincidence camera with X-ray tube-based attenuation maps.

The purpose of this study was to characterize a dual-head gamma camera capable of FDG imaging using coincidence detection and equipped with an integrated x-ray transmission system for attenuation correction, anatomic mapping, and image fusion. METHODS: Radiation dose (425 mrads skin dose) and tissue contrast (0.7% deviation from expected values) were assessed for the x-ray system. Registration of transmission and emission scans was validated using a hot sphere phantom and was verified in selected patient studies. RESULTS: Fusion of anatomic maps and FDG images allowed precise anatomic localization of lesions identified using dual-head coincidence imaging. CONCLUSION: The combined approach of x-ray attenuation, anatomic mapping, and image fusion with scintigraphic studies provides a new diagnostic tool for nuclear medicine and fertile ground for future research.     

衰减校正在18F-FDG符合线路显像中的价值

目的评价衰减校正(AC)在^18F-脱氧葡萄糖(FDG)符合线路显像中的价值。方法对圆柱体模型行^18F-FDG符合线路显像，进行AC和非衰减校正(NAC)图像视觉分析和半定量分析比较。结果AC图像在均匀度和空间分辨率等方面均优于NAC图像，并消除了NAC图像中的形变现象。结论AC可明显改善图像质量。     

The benefit of functional-anatomical imaging with [18F]fluorodeoxyglucose utilizing a dual-head coincidence gamma camera with an integrated X-ray transmission system in non-small cell lung cancer

AIM: To evaluate functional-anatomical imaging with 2-[F]fluoro-2-deoxy-D-glucose (F-FDG) utilizing a dual-head coincidence gamma camera with an integrated X-ray transmission system for attenuation correction, anatomical mapping, and image fusion compared to conventional diagnostics by computed tomography (CT) in non-small cell lung cancer (NSCLC). METHODS: Thirty-five patients with NSCLC underwent FDG imaging of the thoracic area using a dual-head coincidence gamma camera (DHC) with an integrated X-ray transmission system. State-of-the-art CT scans had been performed before. Whole-body dedicated FDG positron emission tomography (PET) was performed immediately prior to DHC. Staging by CT and DHC, and DHC with integrated image fusion (FDHC) were re-evaluated with regard to detectable lesions, correct anatomical diagnoses, and clinical impact. Results of DHC and PET were compared for analysis of limitations of DHC. RESULTS: One hundred and thirteen tumour lesions were identified by CT. DHC detected 128 lesions overall: 102 true positive CT lesions were confirmed, 25 additional lesions were detected which affected staging in eight patients, and one false positive lung lesion did not show up in DHC. Nine CT lesions were missed by DHC (lymph node and lung). PET detected 150 areas of focally enhanced uptake, delivering two false positive results (nuchal muscles, pneumonia). Final evaluation confirmed 148 malignant lesions. Compared to CT, the results of DHC changed staging or treatment in 8/35 patients (23%). Lesion detection by DHC was limited by tumour size and intensity of FDG uptake. Image fusion provided relevant clinical information in 9/35 patients (26%). CONCLUSION: Functional imaging in NSCLC with this dual-head gamma camera is superior to morphological imaging by CT, although inferior to dedicated PET imaging. Combined functional-anatomical imaging has the potential to improve staging and localization procedures before surgery or radiotherapy.     

Correction methods for random coincidences in fully 3D whole-body PET: impact on data and image quality.

With the advantages of the increased sensitivity of fully 3-dimensional (3D) PET for whole-body imaging come the challenges of more complicated quantitative corrections and, in particular, an increase in the number of random coincidences. The most common method of correcting for random coincidences is the real-time subtraction of a delayed coincidence channel, which does not add bias but increases noise. An alternative approach is the postacquisition subtraction of a low-noise random coincidence estimate, which can be obtained either from a smoothed delayed coincidence sinogram or from a calibration scan or directly estimated. Each method makes different trade-offs between noise amplification, bias, and data-processing requirements. These trade-offs are dependent on activity injected, the local imaging environment (e.g., near the bladder), and the reconstruction algorithm. METHODS: Using fully 3D whole-body simulations and phantom studies, we investigate how the gains in noise equivalent count (NEC) rates from using a noiseless random coincidence estimation method are translated to improvements in image signal-to-noise ratio (SNR). The image SNR, however, depends on the image reconstruction method and the local imaging environment. RESULTS: We show that for fully 3D whole-body imaging using a particular set of scanners and clinical protocols, a low-noise estimate of random coincidences improves sinogram and image SNRs by approximately 15% compared with online subtraction of delayed coincidences. CONCLUSION: A 15% improvement in image SNR arises from a 32% increase in the NEC rate. Thus, scan duration can be reduced by 25% while still maintaining a constant total acquired NEC.     

Assessment of malignancy in pulmonary lesions: FDG dual-head coincidence gamma camera imaging in association with serum tumor marker measurement.

The purpose of the study was to evaluate the performance of dual-head coincidence gamma camera imaging using FDG in association with serum marker assays in identifying lung carcinoma in patients with abnormal findings on chest radiography. METHODS: A prospective evaluation of FDG imaging with coincidence detection emission tomography (CDET) using a dual-head gamma camera combined with the assessment of 3 sensitive serum markers of lung cancer (carcinoembryonic antigen, neuron specific enolase, and CYFRA 21-1) was performed on the same day on 58 consecutive patients with known or suspected lung malignancy. RESULTS: Fifty-three patients were proven to have lung cancer, and 5 patients had benign lung disease. Coincidence imaging showed significantly increased FDG uptake in 49 of 53 patients with proven malignancy (sensitivity, 92.5%) and in 3 patients with benign disease. FDG imaging had negative findings in 4 patients with proven malignancy and 2 patients with benign disease. Serum tumor marker levels were elevated in 42 of 53 cancer patients (sensitivity, 79.2%) and normal in 11 patients with proven malignancy. Nine patients with proven malignancy had positive findings on FDG images and negative marker assays. Two patients with proven malignancy had negative findings on FDG images and positive marker assays. The positive predictive value for lung cancer was 94.2% for FDG alone and 97.6% for FDG in association with serum markers. CONCLUSION: In this study, FDG CDET imaging was a powerful tool for evaluating patients with lung lesions suggestive of malignancy. Although the determination of serum marker levels was less accurate than FDG imaging, positive FDG results found in association with positive markers significantly increased the likelihood of lung malignancy.     

Oncological diagnosis using positron coincidence gamma camera with fluorodeoxyglucose in comparison with dedicated PET

The purpose of this study was to compare the utility of a dual-head positron coincidence detection gamma camera (PCD) with that of dedicated positron emission tomography (PET) in the imaging of various malignancies using (18)F-fluorodeoxyglucose (FDG). 25 patients with known or suspected malignancies at various sites underwent imaging with both methods, and diagnostic performance on a lesion basis was compared. Tumour lesions were analyzed visually and semi-quantitatively using the ratio of tumour-to-background counts (T/B ratio). FDG PCD and FDG PET visually detected 34 (72.3%) lesions and 37 (78.7%) lesions, respectively. The mean T/B ratio and standard deviation (SD) of FDG PCD was 3.5+/-3.3, significantly lower than that of FDG PET (8.4+/-7.1, p<0.001). When tumour lesions were less than 2.0 cm in diameter, the sensitivity of FDG PCD was 37.5%, significantly inferior to that of FDG PET (50.0%, p<0.01). Sensitivity between FDG PCD and FDG PET in lesions of more than 2.0 cm diameter showed no statistically significant difference. This study indicates that FDG imaging with a dual-head coincidence detection gamma camera can provide suitable diagnostic performance for lesions greater than 2.0 cm diameter, but performed significantly worse than dedicated PET for lesions smaller than this.     

Comparison of FDG PET and positron coincidence detection imaging using a dual-head gamma camera with 5/8-inch NaI(Tl) crystals in patients with suspected body malignancies

The purpose of this study was to compare the diagnostic accuracy of fluorine-18 fluorodeoxyglucose (FDG) images obtained with (a) a dual-head coincidence gamma camera (DHC) equipped with 5/8-inch-thick NaI(Tl) crystals and parallel slit collimators and (b) a dedicated positron emission tomograph (PET) in a series of 28 patients with known or suspected malignancies. Twenty-eight patients with known or suspected malignancies underwent whole-body FDG PET imaging (Siemens, ECAT 933) after injection of approximately 10 mCi of 18F-FDG. FDG DHC images were then acquired for 30 min over the regions of interest using a dual-head gamma camera (VariCam, Elscint). The images were reconstructed in the normal mode, using photopeak/photopeak, photopeak/Compton, and Compton/photopeak coincidence events. FDG PET imaging found 45 lesions ranging in size from 1 cm to 7 cm in 28 patients. FDG DHC imaging detected 35/45 (78%) of these lesions. Among the ten lesions not seen with FDG DHC imaging, eight were less than 1.5 cm in size, and two were located centrally within the abdomen suffering from marked attenuation effects. The lesions were classified into three categories: thorax (n=24), liver (n=12), and extrahepatic abdominal (n=9). FDG DHC imaging identified 100% of lesions above 1.5 cm in the thorax group and 78% of those below 1.5 cm, for an overall total of 83%. FDG DHC imaging identified 100% of lesions above 1.5 cm, in the liver and 43% of lesions below 1.5 cm, for an overall total of 67%. FDG DHC imaging identified 78% of lesions above 1.5 cm in the extrahepatic abdominal group. There were no lesions below 1.5 cm in this group. FDG coincidence imaging using a dual-head gamma camera detected 90% of lesions greater than 1.5 cm. These data suggest that DHC imaging can be used clinically in well-defined diagnostic situations to differentiate benign from malignant lesions.     

18F-FDG符合线路显像对食管癌术后复发转移的诊断价值

目的 探讨^18F-脱氧葡萄糖（FDG）符合线路显像对食管癌术后复发转移的诊断价值。方法 对29例临床怀疑复发转移的食管鳞状细胞癌术后患者行^18F-FDG符合线路显像，计算其诊断复发转移灶的灵敏度、特异性和准确性，并与CT诊断结果比较。结果 29例患者中符合线路显像真阳性19例，真阴性6例，假阳性、假阴性各2例，其诊断食管癌术后复发转移的灵敏度、特异性和准确性分别为90．5％（19／21例）、75．0％（6／8例）和86．2％（25／29例）；而CT诊断的灵敏度、特异性和准确性分别为71．4％（15／21例）、87．5％（7／8例）和75．9％（22／29例）。在符合线路显像与CT检查均阳性的13例患者中，CT检出病灶20个；而符合线路显像检出27个，比CT多检出的病灶包括食管癌复发，锁骨上、纵隔和肺门淋巴结及骨转移。结论 ^18F-FDG符合线路显像对食管癌术后复发转移的诊断具有较高的临床价值，尤其在临床疑有复发转移而常规影像学检查阴性时有重要意义。     

Usefulness of dual-head coincidence gamma camera with thick nal crystals for nuclear oncology: Comparison with dedicated PET camera and conventional gamma camera with thin NaI crystals

AIM: A comparative study of the images obtained with a dual-head coincidence gamma camera with thick NaI crystals (19 mm), a dedicated PET camera with BGO crystals and a conventional gamma camera with thin NaI crystals (9.5 mm) was conducted to clarify the clinical feasibility of a dual-head coincidence gamma camera with thick NaI crystals. METHODS: FDG images of 27 patients with malignant tumors were obtained by means of a dual-head coincidence gamma camera with thick NaI crystal and a dedicated PET camera with BGO crystals. The images of bone scintigraphy in 10 cancer patients obtained with the dual-head coincidence gamma camera were compared with those taken by a conventional dual-head gamma camera with thin NaI crystals. RESULTS: Patient-basis sensitivity in 27 patients with neoplasms and lesion-basis sensitivity of the dual-head coincidence gamma camera and the dedicated PET camera were 74.1% and 85.2% (n.s.), 66.7% and 72.2% (n.s.), respectively. The tumor to background FDG uptake ratio derived from the coincidence gamma camera was significantly lower than that derived from the dedicated PET camera (mean +/- s.d.; 3.48 +/- 3.77 vs. 8.12 +/- 8.92, p < 0.0001), but the tumor to background FDG uptake ratio obtained with both methods correlated well (r = 0.84, p < 0.001). Similar whole body bone scans were obtained with the dual-head coincidence gamma camera and the conventional dual-head gamma camera in all 10 patients. CONCLUSION: These results suggest that the dual-head coincidence gamma camera with thick NaI crystals has potentially high clinical applicability for community hospitals.