Combining CT and scintigraphy: SPECT-CT and PET-CT

In recent years tomographic hybrid scanners have been quickly introduced in nuclear medicine: single-photon emission computed tomography (SPECT)-CT and positron emission tomography (PET)-CT.- Both SPECT-CT and PET-CT techniques provide a higher diagnostic accuracy than conventional (non-tomographic, non-hybrid) bone scintigraphy (bone scan).- Differences between 99mTc hydroxymethylene diphosphonate (HDP) SPECT-CT or 99mTc methylene diphosphonate (MDP) SPECT-CT and 18F-fluoride PET-CT bone scanning relate to image quality, technique, availability, quantification possibilities, radiation dosimetry and financial cost.- Indications for these techniques will especially lie in the field of more accurate detection of skeletal metastases than with bone scans, patients with unexplained musculoskeletal pain, the diagnostic stage after conventional X-ray and/or MRI, and quantification of bone metabolism.     

单个腰椎孤立病灶行SPECT-CT断层显像的初步应用

目的探讨单个腰椎孤立病灶行SPECT-CT断层显像的诊断价值。方法选择20例在全身骨显像图像上只发现腰椎单个病灶的患者,再进行病变部位的SPECT-CT断层显像。将所得数据通过Astonish的重建方法进行重建并与同机CT图像融合后,由两位经验丰富的阅片医生进行阅片,所得结果与其他影像学检查（CT或MRI或PET-CT）或病理学结果进行比对。结果 SPECT-CT诊断的符合率为95%。20例中有12例为腰椎退行性改变,与其他检查结果相符,其中8例SPECT-CT融合图像示浓聚点位于椎体上、下关节突关节,2例位于椎体前缘,2例位于椎体下缘;7例患者提示椎体恶性病变;1例压缩性骨折。结论 SPECT-CT断层融合显像结合了螺旋CT的定位及精细诊断功能,能提供更多信息,对腰椎孤立性病灶的定位、定性诊断有重要价值,具有较高的敏感性和特异性。     

无症状体检人群中~(18)F-FDG PET/CT筛查恶性肿瘤的应用价值

目的评估无症状体检人群中18F-FDG PET/CT筛查恶性肿瘤的应用价值。方法选取2011年1月~2014年12月在解放军总医院健康管理研究院应用18F-FDG PET/CT筛查恶性肿瘤的无症状体检人群4 899例,平均年龄(51.8±9.5)岁,男性3 390例(69.2%),女性1 509例(30.8%)。结果 PET/CT检查发现可疑高代谢或占位病灶,经穿刺或手术病理证实的恶性肿瘤72例,包括肺癌、甲状腺癌以及结肠癌等13种肿瘤,筛查阳性率为1.5%。PET/CT筛查假阴性8例,假阳性65例,筛查的敏感度为90.0%,特异性为99.8%,阳性预测值52.6%,阴性预测值98.4%。结论体检人群中PET/CT筛查可发现全身多部位的早期恶性肿瘤。为减少假阴性和假阳性,PET/CT筛查恶性肿瘤应与甲状腺、肝脏超声及胃肠镜检查相结合。低阳性预测值及射线暴露诱发肿瘤的风险是在无症状体检人群中应用PET/CT筛查恶性肿瘤时应重视的问题,应注意选择适应症,防止滥用检查和过度医疗。     

Positron emission tomography: radioisotope and radiopharmaceutical production

A Centre for Positron Emission Tomography (PET) has been operational within the Department of Nuclear Medicine at the Austin & Repatriation Medical Centre (A&RMC) in Melbourne for seven years. PET is a non-invasive imaging technique based on the use of biologically relevant compounds labelled with short-lived positron-emitting radionuclides such as carbon-11, nitrogen-13, oxygen-15 and fluorine-18. The basic facility consists of a medical cyclotron (10 MeV proton & 5 MeV deuteron), six lead-shielded hotcells with associated radiochemistry facilities, radiopharmacy and a whole body PET scanner. A strong radiolabelling development program, including the production of 15O-oxygen, 15O-carbon monoxide, 15O-carbon dioxide, 15O-water, 13N-ammonia, 18F-FDG, 18F-FMISO, 11C-SCH23390 and 11C-flumazenil has been pursued to support an ambitious clinical and research program in neurology, oncology, cardiology and psychiatry.     

~(18)F-FDG PET和PET/CT在肾上腺病变鉴别诊断中的作用

目的:探讨18F-脱氧葡萄糖(FDG)PET或PET/CT显像在肾上腺病变鉴别诊断中的应用价值。方法:25例肾上腺占位患者均行18FDG PET或PET/CT图像,检查后1月内19例经手术切除,6例经穿刺活检获得病理结果,25例均有同期术前CT增强扫描。按照肾上腺占位是否产生内分泌症状分为有功能病变组(组A,8例)和无功能病变组(组B,17例),对18FDG PET或PET/CT图像所示肾上腺病变行半定量分析,计算肾上腺病变SUVm ax值及肾上腺病变/肝脏SUV-m ax比值。结果:1.有功能病变组的临床多表现为库欣综合征和高血压,良性病变SUVm ax为5.04±2.07,恶性病变的SUVm ax为8.33±2.57.良性肾上腺病变/肝脏SUVm ax的比值为2.52±0.62,恶性肾上腺病变/肝脏SUVm ax的比值为2.92±1.03。良性病变的大小为3.26±1.01 cm,明显小于恶性病变(7.80±1.82 cm)。2.无功能病变组,恶性病变的SUVm ax为11.39±7.96明显高于良性病变(1.93±0.54)。恶性肾上腺病变/肝脏SUVm ax的比值为4.51±2.92,明显高于良性肾上...     

The value of PET-CT imaging in malignant tumours of the head and neck

Imaging with fluor-18-deoxyglucose(FDG)-positron-emission tomography (PET) and CT combined in a single machine is a recent development. Using this technique both molecular and anatomical information are acquired. This results in an increased sensitivity and specificity in comparison to PET and CT as a single modality. One of the main advantages is that interpretation of PET images can be related to the anatomical information which helps to delineate the size and extent of a tumour as well as its relationship with surrounding tissues. It is also useful in planning surgical treatment and irradiation. At restaging PET-CT delineates the site and extent of a recurrence in the complex anatomy of the head and neck region and helps to define the location of a biopsy. This is particularly valuable in the anatomically complex head and neck region. Whole-body imaging can detect distant metastases and second primary tumours. PET-CT has the potential to become a part of the staging procedure of the primary tumour and also the follow-up in patients who have been treated for head and neck cancer.     

Does 18F-FDG PET/CT play a role in the differential diagnosis of parotid masses

AIM: The aim of the present study was to assess the accuracy of an hybrid PET/CT scanner in the evaluation of newly diagnosed parotid masses, comparing the results with those reported in the literature with using PET scanners only. METHODS: The potential role of 18F-FDG PET/CT in distinguishing benign from malignant parotid masses in 14 consecutive patients was investigated. All patients were preoperatively evaluated by means of ultrasound (US), US-guided fine needle aspiration (FNA) cytology, computed tomography (CT) scan, magnetic resonance imaging (MRI) and 18F-FDG PET/CT. For To interpreting FDG PET findings, the right to left parotid (R/L) SUV max ratio was calculated in a group of 54 patients without evidence of parotideal disease (mean+/-SD = 1+/-0.2; range = 0.8-1.2); considering the R/L SUV max ratio, focal or diffuse uptakes <0.8 or >1.2 were considered as potentially pathological. RESULTS: Imaging data were compared with surgical and histopathological findings. At FDG PET/CT, 9 false positive cases were found (8 Warthin's tumours, 1 pleomorphic adenoma), 1 false negative (acinar cell carcinoma), 4 true negative (1 Warthin's tumour, 1 pleomorphic adenoma, 1 lymph epithelial cyst, 1 parotid inflammation) whereas there was no case of true positive. The global accuracy of FGD PET/CT was rather low = at 29%. CONCLUSIONS: In agreement with other preliminary reports in which the FDG PET without CT fusion imaging was used, in our experience 18F-FDG PET/CT did not prove to play a significant role in differential diagnosis (benign vs malignant) of parotid masses. Further studies collecting larger groups of patients are needed to further elucidate this observation.     

FDG PET/CT在胸部肿瘤放疗中的应用

目的总结葡萄糖类似物（FDG）PET/CT在胸部肿瘤放疗中应用的初步经验。方法 2009年8月~2011年12月,42例胸部肿瘤患者在我院接受PET/CT（GE Discovery）定位。图像传至VarianEclipse 8.6治疗计划系统进行图像分析处理及治疗计划设计。分析PET/CT图像融合对认定肿瘤靶区范围及对总体放疗方案和治疗计划的影响。结果 42例患者共确诊肿瘤病灶109个,其中,80.7%病灶在CT和PET图像均明确显示;19.3%病灶通过融合PET图像而确诊。融合图像在明确小的转移性淋巴结方面有显著优势。在肺部病灶大小和范围的显示上PET图像与CT图像常有一定差异,可能与呼吸运动或/和化疗影响肿瘤糖代谢有关。通常FDG PET/CT不能有效鉴别肿瘤与合并的炎症和手术创伤。结论 FDG PET/CT应用显著提高了肿瘤的诊断水准,并对放疗方案和治疗计划产生积极影响,但仍需探求排除假阳性信息的有效方法。     

The clinical application of PET/CT: a contemporary review

The combination of positron emission tomography (PET) scanners and x-ray computed tomography (CT) scanners into a single PET/CT scanner has resulted in significant improvements in the diagnosis and staging of disease, particularly in the field of oncology. A decade on from the publication of the details of the first PET/CT scanner, we review the technology and applications of the modality. We examine the design aspects of combining two different imaging types into a single scanner, and the artefacts produced such as attenuation correction, motion and CT truncation artefacts. The article also provides a discussion and literature review of the applications of PET/CT to date, covering detection of tumours, radiotherapy treatment planning, patient management, and applications external to the field of oncology.     

肿瘤患者放疗后照射野内椎体骨髓FDG PET/CT影像学表现

目的 探讨肿瘤患者放疗后椎体骨髓FDG PET/CT改变及其临床意义。方法 对32例患者放疗后椎体FDG PET/CT SUV与正常健康人椎体SUV比较分析。结果 与正常人椎体相比,放疗后椎体SUV明显降低,并且界限清晰。结论 肿瘤患者放疗后照射野内椎体FDG PET/CT SUV具有特征性,能够指导临床治疗。     

Imaging: the next generation

The next generation of medical imaging scanners includes a combo of positron emission tomography and computed tomography--a hybrid that experts say will revolutionize both the practice and business of cancer treatment through faster and more accurate diagnoses. Accelerating the development of PET-CT machines is HCFA's consideration of expanding Medicare coverage of PET for a larger number of cancers.     

A retrospective evaluation of radiation dose associated with low dose FDG protocols in whole-body PET/CT

The objective of the study is to retrospectively measure patient radiation dose resulting from whole body X-ray CT and FDG PET studies using a low-dose protocol performed on the Siemens Biograph mCT scanner. A total of 483 patient studies were reviewed. For each, the CT dose-length product was used to estimate radiation dose to the patient as a result of the whole body X-ray CT component of the PET/CT study. The net injected FDG dose was used to calculate the whole body effective dose based on ICRP recommendations. Dose calculations were also modified to take into account individual patient weight. The total effective dose received by each patient was taken as the sum of the PET and CT components of the study. The mean effective dose from the CT component of the diagnostic study was found to be 8.2 mSv (3.4–23.4 mSv), for a CT protocol of 120 kV_p and effective tube current–time product of 80 mAs with automatic exposure control. For an average injected FDG activity of 304 MBq the mean PET effective dose was found to be 6.3 mSv when using the ICRP standard models, or 6.0 mSv when scaling effective dose to individual patient weight or patient blood volume. The average total effective dose across the entire patient cohort for a combined PET/CT study was found to be ~14.5 mSv (9.6–29.8 mSv). Low-dose protocols for whole-body PET/CT scanning result in an effective radiation dose to the patient of approximately 14.5 mSv. Additional reductions through the use of iterative CT reconstruction and optimized low-dose FDG protocols could see total effective doses for whole-body PET/CT fall to below 10 mSv.     

Mathematical modeling of the radiation dose received from photons passing over and through shielding walls in a PET/CT suite

Given that the financial cost of shielding PET/CT suites can be substantial, it has become increasingly important to be able to accurately assess the thickness of shielding required for barriers and whether it is necessary to extend such shielding all the way to the ceiling. The overall shielding requirement for a PET/CT installation must take into account both 511 keV gamma ray emissions from PET scans and lower energy x-ray scatter from CT scans. This paper deals with the overall impact of emissions from both modalities. Radiation exposure from both scatter over shielding barriers as well as transmission through these barriers is taken into account. A series of simulations of the dose received by a person positioned behind a shielding barrier in a typical PET/CT scanning suite were carried out using both Monte Carlo and analytical models. The transmission through lead barriers was found to be very dependent on the geometry of the radiation source and the resulting energy spectrum of the emitted radiation. The transmission from a patient source was found to be around half of that from a small vial and also half of that reported previously using parallel beams of mono-energetic radiation. For PET emissions, the dose from scatter over the barrier at waist height is relatively small but may have to be taken into account if the design dose limit is low. Shielding from floor to ceiling is probably not warranted in most instances for PET gamma emissions; in PET/CT installations, however, a thinner layer of shielding may need to extend to the ceiling of the imaging room to limit x-ray scatter over the wall from the CT unit.     

PET/CT中心建设之四——放射防护

目的:探讨PET/CT中心建设中的放射防护。方法:根据我国放射防护相关的现行政策、PET/CT技术特点、辐射剂量的理论及工作经验积累,讨论PET/CT中心建设中放射防护的相关问题。结果:给出了PET/CT中心从放射性药物分装到PET/CT扫描各工作环节中的放射防护要求;导出了各环节中防护设施屏蔽厚度的计算公式,并介绍了放射防护的评价验收程序。结论:全面系统探讨了PET/CT中心建设各环节中的放射防护,为医疗机构建立PET/CT中心提供参考。     

18F-FDG和18F-FET PET-CT检查致受检者辐射剂量研究

目的 估算接受¹⁸F-FDG(¹⁸F-2-deoxy-D-glucose)和¹⁸F-FET(O-2-¹⁸F-fluoroethyl-L-tyrosine)PET-CT全身检查受检者的有效剂量和器官剂量。方法 使用两种PET-CT扫描协议进行全身显像。PET部分的有效剂量和器官剂量利用基于医学内照射剂量(Medical Internal Radiation Dose, MIRD)计算模式的计算程序IDAC 2.1进行计算,CT部分的有效剂量和器官剂量利用VirtualDose软件计算,PET和CT剂量之和为受检者总的有效剂量。结果 在常规PET-CT扫描中,男性受检者受¹⁸F-FDG辐射所致的有效剂量为(4.81 ±1.04) mSv,女性受检者为(6.09 ±0.73) mSv;男性受检者受¹⁸F-FET辐射所致的有效剂量为(2.67 ±0.38) mSv,女性受检者为(3.21 ±0.38) mSv;CT部分男性受检者的有效剂量为(5.63 ±0.32) mSv,女性受检者为(5.51 ±0.29) mSv。¹⁸F-FDG PET-CT检查男性和女性受检者所受总有效剂量分别为(10.44 ±1.09) mSv和(11.60 ±0.79) mSv。¹⁸F-FET PET-CT检查总有效剂量分别为(8.30 ±0.50) mSv和(8.72 ±0.49) mSv。在诊断性CT扫描中,CT扫描致男性受检者的有效剂量为(16.28 ±1.01) mSv,女性受检者为(13.49 ±0.72) mSv;¹⁸F-FDG PET-CT检查男性和女性受检者总有效剂量分别为(21.09 ±1.45) mSv和(19.58 ±1.03) mSv。¹⁸F-FET PET-CT检查总有效剂量分别为(18.95 ±1.08) mSv和(16.70 ±0.81) mSv。结论 不同的PET-CT扫描参数致受检者受到不同大小的辐射剂量,在日常工作中应根据受检者的实际情况,优化PET和CT的采集参数,降低受检者剂量,实践辐射防护最优化。     

PET/CT职业照射的剂量估算与分析

[目的]介绍正电子发射型计算机断层显像（PET）/计算机断层扫描（CT）应用中职业照射剂量估算方法及辐射防护措施,为评价和技术审评提供参考。[方法]参照国际原子能机构（IAEA）58号技术文件和美国医学物理学家协会（AAPM）108工作组的报告,以某医院PET/CT中心为例,分析辐射源项和工作流程,细化参数,分别估算工作人员各操作岗位的年受照剂量,结合轮岗情况给出年剂量。[结果]该中心工作人员分装、注射、摆位和控制室操作等岗位的年受照剂量分别为0.06、0.14、7.00、0.36 mSv,在轮岗情况下年受照剂量约为1.9 mSv,手部当量剂量为340 mSv。[结论]工作人员应实行轮岗制度,加强分装、注射、摆位环节的辐射防护。     

Distribution of thermal neutron flux around a PET cyclotron

The number of positron emission tomography (PET) examinations has greatly increased world-wide. Since positron emission nuclides for the PET examinations have short half-lives, they are mainly produced using on-site cyclotrons. During the production of the nuclides, significant quantities of neutrons are generated from the cyclotrons. Neutrons have potential to activate the materials around the cyclotrons and cause exposure to the staff. To investigate quantities and distribution of the thermal neutrons, thermal neutron fluxes were measured around a PET cyclotron in a laboratory associating with a hospital. The cyclotron accelerates protons up to 18 MeV, and the mean particle current is 20 μA. The neutron fluxes were measured during both 18F production and C production. Gold foils and thermoluminescent dosimeter (TLD) badges were used to measure the neutron fluxes. The neutron fluxes in the target box averaged 9.3 × 10(6) cm(-2) s(-1) and 1.7 × 10(6) cm(-2) s(-1) during 18F and 11C production, respectively. Those in the cyclotron room averaged 4.1 × 10(5) cm(-2) s(-1) and 1.2 × 10(5) cm(-2) s(-1), respectively. Those outside the concrete wall shielding were estimated as being equal to or less than ～3 cm s, which corresponded to 0.1 μSv h(-1) in effective dose. The neutron fluxes outside the concrete shielding were confirmed to be quite low compared to the legal limit.     

The contribution of medical physicists and doctors in Aberdeen to the evolution of modern medical imaging--SPECT, PET and MRI, 1965-1992

From the beginnings of medical imaging with radioactivity, an account is given of the development in Aberdeen of Computed Tomography (CT) scanners in Nuclear Medicine, and their clinical value, leading to present-day gamma-cameras. The introduction and clinical use of the cyclotron and Positron Emission Tomography (PET) imager in Aberdeen, has led to a national programme for the cancer patients in Scotland. Early animal work with electron magnetic resonance, which developed into a programme towards nuclear magnetic resonance of water, and then to a quest to build the first clinically-useful whole-body MRI, is described. Successful diagnostic images obtained with it have led to the present-day worldwide use of the MRI technique.     

医用回旋加速器质量控制与安全策略探讨

医用回旋加速器为临床PET/CT检查提供正电子放射性核素,做好回旋加速器的质量控制和安全防护就是要保证回旋加速器良好稳定的运行,保证安全生产,从而提供足额且符合要求的正电子核素,这就要求做好回旋加速器的维护保养工作,同时要注重技术人员的操作培训和质量控制意识的养成,维修和备件的供应也列入回旋加速器的质控项目。本文总结了医用回旋加速器各结构维护和保养的方法,阐述了对技术人员进行操作培训,培养质量控制意识的重要性。