Myocardial metabolic imaging by means of fluorine-18 deoxyglucose/technetium-99m sestamibi dual-isotope single-photon emission tomography

The detection of preserved glucose uptake in hypoperfused dysfunctional myocardium by fluorine-18 deoxyglucose (FDG) positron emission tomography (PET) represents the method of choice in myocardial viability diagnostics. As the technique is not available for the majority of patients due to cost and the limited capacity of the PET centres, it was the aim of the present work to develop and test FDG single-photon emission tomography (SPET) with the means of conventional nuclear medicine. The perfusion marker sestamibi (MIBI) was used together with the metabolic tracer FDG in dual-isotope acquisition. A conventional SPET camera was equipped with a 511-keV collimator and designed to operate with simultaneous four-channel acquisition. In this way, the scatter of 18F into the technetium-99m energy window could be taken into account by a novel method of scatter correction. Thirty patients with regional wall motion abnormalities at rest were investigated. The results of visual wall motion analysis by contrast cine-ventriculography in nine segments/heart were compared with the results of quantitative scintigraphy. The scintigraphic patterns of MIBI and FDG tracer accumulation were defined as normal, matched defects and perfusion-metabolism mismatches. Spatial resolution of the system was satisfactory, with a full width at half maximum (FWHM) of 15.2 mm for ¹⁸F and 14.0 mm for ^99mTe, as measured by planar imaging in air at 5 cm distance from the collimator. Image quality allowed interpretation in all 30 patients. 88% of segments without relevant wall motion abnormalities presented normal scintigraphic results. Seventy-five akinetic segments showed mismatches in 27%, matched defects in 44% and normal perfusion in 29%. We conclude that FDG-MIBI dual-isotope SPET is technically feasible with the means of conventional nuclear medicine. Thus, the method is potentially available for widespread application in patient care and may represent an alternative to the ²⁰¹T1 reinjection technique.     

Cardiac metabolism: A technical spectrum of modalities including positron emission tomography,single-photon emission computed tomography,and magnetic resonance spectroscopy

Noninvasive techniques for the assessment of cardiac metabolism are important for the detection of potentially salvageable tissue in jeopardized areas of the myocardium. The correct identification of hibernating and stunned myocardium in patients with severely depressed cardiac function can have vital therapeutic consequences for the patient. Changes in myocardial fatty acid and glucose metabolism during acute and prolonged ischemia can be traced by positron-emitting or gamma-emitting radiopharmaceuticals. Alternatively,³¹P-labeled magnetic resonance spectroscopy can be used for the assessment of high-energy phosphate metabolism. It is not yet clear which modality will emerge as the most useful in the clinical setting. Positron emission tomography (PET) that uses combinations of flow tracers and metabolic tracers offers unique opportunities for quantification and high-resolution static and rapid dynamic studies. Currently, assessment of glucose metabolism with¹⁸F-fluorodeoxyglucose is regarded as the gold standard for myocardial viability and prediction of improvement of impaired contractile function after revascularization. However, preserved oxidative metabolism may be required for potential functional improvement, and therefore assessment of residual oxidative metabolism by¹¹C-labeled acetate PET may prove to be more accurate than¹⁸F-fluorodeoxyglucose PET, which reflects both anaerobic and oxidative metabolism. Moreover, because fatty acids are metabolized only aerobically, they are excellent candidates for the clinical assessment of myocardial viability and prediction of functional improvement after revascularization. Especially derivatives of fatty acids that are not metabolized but accumulate in the myocyte are attractive for myocardial imaging. Examples are¹²³I-beta-methyl-p-iodophenyl pentadecanoic acid and 15-(o-¹²³I-phenyl)-pentadecanoic acid. These tracers can be detected by planar scintigraphy and single-photon emission computed tomography, which are more economical and widely available than PET. In addition, 511 keV collimators have been developed recently, making the detection of positron emitters by planar scintigraphy and single-photon emission computed tomography feasible. The experience with³¹P-labeled magnetic resonance spectroscopy in humans is still limited. With current magnetic resonance spectroscopic techniques, insufficient spatial resolution is achieved for clinical purposes, but the possibility of serial measurements to monitor rapid changes of phosphate-containing molecules in time makes magnetic resonance spectroscopy very valuable for the research of myocardial metabolism.     

PET-CT在恶性肿瘤诊断中的初步应用

目的探讨PET-CT一体机在恶性肿瘤中的应用价值.方法收集已经明确诊断的全身不同部位的恶性肿瘤病例62例,经PET-CT检查后进行回顾性分析,采用目测和半定量分析方法.结果62例肿瘤病人共检出142个病灶,PET图像阳性率93.55%(58/62);PET图像阴性率6.45%(4/62);PET发现病灶而CT未完全发现病灶率19.4%(12/62);CT发现而PET未见浓聚率6.45%(4/62);原发灶未能找到率1.61%(1/62).标准化摄取值(SUV)大于2.5占78.2%(111/142);SUV2.5～2.0占14.8%(21/142);SUV小于2.0占7%(10/142).结论PET-CT与单纯PET,CT比较具有明显的优势,可以精确定位、定性,但PET-CT也有一定的局限性.     

18F-FDG-SPECT显像技术在肺癌诊断中的意义

目的 :研究18F FDG SPECT显像技术在肺癌诊断中的临床意义。方法 :利用恶性肿瘤组织高糖酵解的特性 ,对 3 6例肺癌患者用18F标记脱氧葡萄糖 ,使18F浓聚于癌组织中 ,再用带符合线路的SPECT探测其摄取率达到诊断目的 ,并与术后病理切片作对照研究。结果 :3 6例患者病灶检出灵敏度10 0 % ,正确率 91 67% ( 3 3 /3 6) ,其中鳞癌正确率 10 0 % ( 17/17) ,腺癌 84 62 % ( 11/13 )。结论 :18F FDG SPECT能有效地显像肺癌病灶 ,瘤体及转移淋巴结的检出率高于CT ,作为一种补充检查有着重要的临床意义。该检查价格便宜 ,成像清晰 ,有良好应用价值。     

PET在肺癌诊断和分期中的应用

本文介绍正电子发射断层显像(PET)在肺癌诊断和分期中的应用概况，肯定了其临床应用价值。并简要叙述我国PET目前现状及今后展望。PET系大型医疗设备，我国未纳入医疗保险，其发展要根据社会经济发展和病人承受能力，合理布局，有限量地增加。作者指出，加强核医学科人员培训与临床各科医师(包括放射科，肿瘤科，胸外科，放射治疗等)的合作是提高PET临床应用和研究水平的关键因素。     

18F-FDG符合线路SPECT显像在胃肠道恶性肿瘤术后的应用

目的探讨^18F—FDG符合线路SPECT显像在探测胃肠道恶性肿瘤术后复发和远处转移中的应用价值。方法24例胃肠道恶性肿瘤术后患者，其中食管癌4例，胃癌7例，结肠癌6例，直肠癌7例，运用SIEMENS ECAM^deut SPECT仪进行^18F—FDG显像。结果^18F—FDG显像诊断胃肠道恶性肿瘤术后转移和复发的灵敏度为94．7％，特异性80．0％，准确性91．7％。在^18F—FDG显像真阳性18例中，2例为局部复发，5例为局部复发伴转移，11例为远处转移。在有复发的7例患者中，5例^18F—FDG显像结果与CT检查结果一致，2例CT检查局部未见异常，在有转移的16例患者中，共检出转移灶55处。结论符合线路SPECT仪^18F—FDG显像是检测胃肠道恶性肿瘤术后复发和转移的敏感而有效的方法。     

18F-FDG PET用于头颈部肿瘤疗效评价和预后分析的研究进展

正电子发射型计算机断层显像(positron emission tomograph,PET)通过探测肿瘤标准摄取值(standard uptake value,SUV)的大小来判断肿瘤的良恶性、生物学行为、监测放化疗的疗效和早期发现肿瘤的复发等.18F-脱氧葡萄糖(18F-FDG)是目前最常用的PET显像药物,主要反映细胞的葡萄糖代谢情况,18F-FDG的吸收与肿瘤生物学行为、代谢特征、病理学类型及分化程度的相关性为临床判断肿瘤的恶性程度提供了一定的依据,进而为反映肿瘤的预后提供了分子基础.综述了18F-FDG PET在头颈部肿瘤疗效评价和预后分析的研究进展.     

Simultaneous double-isotope autoradiographic measurement of local cerebral glucose metabolic rate and acid-base status in rat brain

We developed a double-isotope autoradiographic method for the simultaneous measurement of the local cerebral metabolic rate for glucose (1CMRG) and index of regional acid-base status (rABI) in single brain slices using [2-¹⁴C]deoxy-D-glucose (DG) and 5,5-dimethyl-[2-¹⁴C]oxazolidine-2,4, dione (DMO). After iv isotope administration, paper chromatography separates plasma DMO from DG activity using a methanol-methylene chloride solvent system. Initial tissue autoradiograms depict regional DMO plus DG and DG metabolite distribution. After 14 days in a well-ventilated hood, 97.5 ±0.5% of all DMO is lost from tissue sections by sublimation, and a second autoradiogram depicts DG plus DG metabolite distribution. Retention of brain lipids does not alter beta-particle self-absorption, avoiding problems associated with isotope extraction with solvents. Autoradiograms are digitized and converted to isotope-content images. The second autoradiogram is used for lCMRG computation. After subtracting the second regional isotope-content value from the first, the DMO content is obtained and used to compute rABI. Application of this method to normal animals yields expected values for lCMRG and rABI. This method is amenable to whole-slice digitization and creation of functional images of lCMRG and ABI followed by pixel-by-pixel correlations of the two variables, making this a potentially valuable tool for the investigation of the relationships between glucose metabolism and brain acid-base balance.     

空洞型肺癌的PET-CT影像特点分析

目的分析空洞型肺癌的PET-CT影像特点。方法回顾性分析35例经病理证实空洞型肺癌患者的PET-CT表现,分析不同病理类型空洞型肺癌间的差异及病理类型、空洞壁厚度最大径、肿瘤最大径对最大标准摄取值(maximum standardized uptake value,SUV max)的影响。结果35例患者中,鳞癌15例,腺癌20例,鳞癌组SUV max为13.51±4.73,显著大于腺癌组(8.50±4.27),P<0.05;而鳞癌组空洞壁厚度最大径及肿瘤最大径均显著大于腺癌组(P值分别为0.001、0.043),两者之间空洞最大径差异无统计学意义(P>0.05)。在空洞壁厚度最大径分组(<0.5 cm,0.5~1.5 cm,>1.5 cm)及肿瘤最大径分组(<3 cm、3~5 cm,>5 cm)中,SUV max差异有统计学意义(F=10.735,P<0.001;F=6.568,P=0.004)。结论18 F-脱氧葡萄糖(18 F-FDG)PET-CT对空洞型肺癌有较好的诊断价值,且SUV max与病理类型、空洞壁厚度最大径以及肿瘤最大径存在一定的关联。     

前期调糖对冠心病患者18F-FDG PET心肌代谢显像图像质量的影响

 目的 探讨前期调糖对冠心病(coronary heart disease,CHD)患者¹⁸F-FDG PET心肌代谢显像图像质量的影响。方法 选择131例年龄33～79岁,CHD患者,男121例,女10例,其中68例合并糖尿病(DM),采用空腹口服葡萄糖＋静脉注射胰岛素法调节血糖,测量其FBG、PBG、BG_注射、记录其高糖及胰岛素用量,之后行¹⁸F-FDG PET心肌代谢显像。图像质量评定采用盲法评定评分法。结果 131例中仅1例显像失败,显像成功率99.2%;将130例显像成功者按是否合并DM分析显示,不合并DM者易获得更佳的图像质量(P=0.002)。患者FBG及BG_注射对图像质量有影响,FBG和BG_注射较低者更易获得高质量的图像,差异有统计学意义(P均=0.000),而PBG和BG_差对最终图像质量无明显影响(P分别=0.191及0.283)。不合并DM组的患者胰岛素/高糖比值与图像质量无明显相关性(P=0.484),而合并DM组患者的胰岛素/高糖在不同图像质量组间有差异,图像质量更好组(评分3分)的胰岛素/高糖更高,差异有统计学意义(P=0.021)。结论 口服葡萄糖+静脉注射胰岛素法¹⁸F-FDG PET心肌代谢显像成功率高,影响图像质量的主要因素是患者FBG和BG_注射。