动物PET研究进展

分子医学研究需要在活体实验动物上观察分子水平的生物学过程，因而正电子发射体层（PET）显像作为目前最成熟的分子显像方法，正被直来越多地用于动物实验。新开发的实验动物专用PET扫描仪的各项性能也逐步趋于完善。该技术将在疾病研究、新药开发、基因治疗等领域发挥重要作用。     

动物PET研究进展

分子医学研究需要在活体实验动物上观察分子水平的生物学过程,因而正电子发射体层(PET)显像作为目前最成熟的分子显像方法,正被越来越多地用于动物实验。新开发的实验动物专用PET扫描仪的各项性能也逐步趋于完善。该技术将在疾病研究、新药开发、基因治疗等领域发挥重要作用。     

PET与临床

自１９７７年以来，ＰＥＴ在欧美各国已广泛用于临床，它能从分子水平反应体内的功能和代谢状况，可用于冠心病、冠状动脉狭窄程度和心肌存活性的判断，对于癫痫灶的定位有其优越性，还可用于肿瘤的早期诊断、分期及良恶性肿瘤的鉴别诊断，其灵敏度和特异性均优于ＳＰＥＣＴ．     

PET和PET/MRI在阿尔茨海默病中的应用

阿尔茨海默病(AD)是老年痴呆最常见的原因,AD的早期诊断有利于改善病人预后。PET和PET/MRI技术在AD的早期诊断和病情评估方面有重要的临床应用价值。现就~(18)F-FDG PET、淀粉样蛋白PET、Tau PET以及PET/MRI在AD方面的发展现状、优势和局限性,以及发展趋势的预测进行综述。     

PET报告基因显像

运用正电子发射体层显像(PET)及相关的PET报告基因及报告探针的活体显像技术可提供关于基因治疗定量及定性的信息,并可提供其他技术不能获得的参数,这对更好地理解基因治疗的过程及人类基因治疗的未来发展及临床应用很有意义。     

PET与临床

自１９７７年以来，ＰＥＴ在欧美各国已广泛用于临床，它能从分子水平反应体内的功能和代谢状况，可用于冠心病、完状动脉狭窄程度和心肌存活性的判断，对于癫痫灶的定位有其优越性，还可用于肿瘤的早期诊断、分期及良恶性肿瘤的鉴别诊断，其灵敏度和特异性均优于ＳＰＥＣＴ。     

PET／MR与PET／CT的对比研究

目的通过与PET／CT在病灶检测及定量分析方面的比较,论证PET／MR一体机应用于临床的可行性。方法2012年5月至2013年2月共300例患者同天间隔15—35min行PET／CT和PET／MR检查,其中临床及影像学资料完整的277例[男165例,女112例,平均年龄（52．9±12．6）岁]纳入该研究。扫描范围由下颌至大腿根部。PET／CT采集为2或3min／床位,PET／MR采集为5min／床位,MRI图像包括T1、T2及弥散加权成像,图像重建采用Vender软件及MRI散射校正Mu图。PET、CT、MRI中只要有1项为阳性,即认为PET／CT及PET／MR的结果为阳性。勾画ROI并计算SUVmax。不同显像技术间探测效率的比较采用配对X2检验,并对PET／CT与PET／MR的SUVmax进行相关分析。结果277例患者随访证实阳性220例,病灶353个。与PET／CT比,PET／MR少发现了6个病灶,但多发现了30个病灶。两者的探测效率差异有统计学意义（P〈0．05）。以病灶和患者计,两者的一致性分别为89.8％（317／353）和85．9％（189／220）。相同部位病灶PET／CT和PET／MR的SUVmax的相关性良好（rs=0．91,P〈0．01）,多数正常组织（除肺和主气管）的SUVmax也具有良好的相关性（rs=0．62-0．76,均P〈0．01）。结论PET／MR一体机在半定量分析方面与PET／CT有良好的相关性,在躯干部尤其是腹、盆腔病变及软组织病变检测方面优于PET／CT,可以为临床提供可靠的影像学诊断。     

美国PET考察情况汇报

美国ＰＥＴ考察情况汇报田嘉禾我有幸受解放军总医院的委派，参加由ＧＥ公司邀请组成的ＰＥＴ考察组，在美国、日本进行了为期２周的以ＰＥＴ发展及应用现状为主要内容的实地考察，现将美国ＰＥＴ考察情况汇报如下。一、目前ＰＥＴ应用概况１．ＰＥＴ的装备。ＰＥＴ是目前...     

Non-malignant FDG uptake in infradiaphragmatic adipose tissue: a new site of physiological tracer biodistribution characterised by PET/CT

The purpose of this study was to characterise a benign pattern of infradiaphragmatic ¹⁸F-fluorodeoxyglucose (FDG) uptake in cancer patients using PET/CT. Infradiaphragmatic foci of FDG uptake, localised by PET/CT in regions of normal fat tissues, were demonstrated, in conjunction with fatty uptake in the neck and shoulders, in 9 of 1,241 (0.7%) patients. The imaging and clinical characteristics of this pattern and its possible clinical significance were assessed. PET/CT precisely localised infradiaphragmatic fat uptake (IDFU) within normal retroperitoneal fatty tissue of the perirenal space (nine patients) and in the paracolic or parahepatic space (four patients). Perirenal uptake was bilateral in five patients and focal in six. Paracolic and parahepatic uptake was bilateral in three patients and linear in all four patients. There was no evidence of malignancy at any of the sites during a follow-up period of 9–21 months. IDFU was significantly more prevalent in young patients assessed for monitoring response to therapy, and was always associated with the benign supradiaphragmatic uptake pattern, although its prevalence was significantly lower. There were no significant differences between the clinical characteristics of these two patterns of benign fatty FDG uptake. It is concluded that PET/CT allows for precise identification of increased FDG uptake in abdominal fatty tissue and further exclusion of disease at such sites. This benign uptake may represent increased glucose consumption in activated brown adipose tissue, similar to the mechanism suggested for supradiaphragmatic uptake. Recognition of this benign IDFU pattern is important for correct interpretation of abdominal PET findings in cancer patients.     

Differentiation between malignant and benign pathologic fractures with F-18-fluoro-2-deoxy-<Emphasis Type="SmallCaps">D</Emphasis>-glucose positron emission tomography/computed tomography

Objective To evaluate the efficacy of F-18-fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography (FDG PET/CT) in differentiating malignant from benign pathologic fractures. Materials and methods F-18 FDG PET/CT was performed on 34 patients with pathologic fractures between May 2004 and June 2007. Fractures were located in tubular bones (26), in the pelvis (six), in the spine (one) and in a rib (one). The FDG uptake pattern at the fracture site was described, whether FDG uptake occurred in the marrow or cortex and soft tissue. Maximum standardized uptake values (SUVmax, the largest value at the region of interest) were measured at the fracture site, including cortical bone, bone marrow and soft tissue. As a reference standard, biopsy was used for 12 patients and clinical follow-up for 22 patients. Sensitivity, specificity and diagnostic accuracy of PET/CT were calculated. Results There were 19 malignant and 15 benign fractures. In the malignant fractures, PET/CT demonstrated high (mean SUVmax 12.0, range 4.3 to 45.7) F-18 FDG uptake in bone marrow in most cases (17 of 19). In benign fractures, there was low FDG uptake (mean SUVmax 2.9, range 0.6 to 5.5) within cortical bone or adjacent soft tissue around the fracture, rarely in the marrow. There were significant differences in the pattern of intramedullary FDG uptake (P < 0.001) and in the mean SUVmax (P < 0.01) between malignant and benign fractures. The sensitivity, specificity and diagnostic accuracy of F-18 FDG PET/CT were 89.5%, 86.7% and 88.2%, respectively, with a cut-off SUVmax set at 4.7. The time interval between fracture and PET/CT did not significantly influence FDG uptake at the fracture site. Conclusion F-18 FDG PET/CT reliably differentiated between malignant and benign fractures based on the SUVmax and based on medullary uptake, which was characteristic for malignant fractures. This research was supported by the Yeungnam University research grants in 2007.     

Growing Cardiac Hemangioma on Serial F-18 FDG PET/CT

Cardiac hemangiomas are extremely rare, benign tumors, which can occur anywhere in the heart. Symptoms are variable according to the size, extension and tumor location, but most cases are asymptomatic and are detected incidentally. They may grow, remain stable and regress; therefore, the natural course of the tumors is unpredictable. Diagnosis mainly depends upon echocardiography, CT, MRI and angiography. Reports of detection by F-18 FDG PET/CT are very limited. We report a case of cardiac hemangioma attached to the right ventricle, compressing the ventricle. It was revealed incidentally on F-18 FDG PET/CT for routine evaluation of thyroid cancer. During two serial F-18 FDG PET/CTs, it grew from 2.8 cm to 4.0 cm with mild FDG uptake. After surgery, the patient remained stable without any complications.     

The influence of I-131 therapy on FDG uptake in differentiated thyroid cancer

OBJECTIVE: 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) [or PET/computed tomography (CT)] is more likely to show false-negative results when it is performed shortly after chemotherapy and/or radiotherapy because of "metabolic stunning". The present study aimed to evaluate the influence of I-131 therapy on FDG uptake and the detection of recurrence or metastasis of differentiated thyroid cancer (DTC). METHODS: We retrospectively enrolled 16 consecutive FDG-PET/CT studies which had been performed in patients with DTC with elevated thyroglobulin (TG) but negative I-131 whole-body scan. All studies were performed under L: -thyroxine suppression. The patients were divided into groups A and B for PET/CT performed within 4 months of I-131 therapy or no such therapy, respectively. Each lesion identified on PET/CT was characterized using a 5-point scale by visual analysis: 0 = definitely benign, 1 = probably benign, 2 = equivocal, 3 = probably malignant, and 4 = definitely malignant. The maximum standardized uptake value (SUV max) in each lesion was also measured for semiquantitative analysis. We compared the visual grading and SUV max of the lesion of highest FDG uptake between groups A and B. RESULTS: For visual analysis, group B had significantly more patients with an uptake score of 3 or 4 than group A (80% vs. 17%, P = 0.01). In addition, there were significantly more equivocal results from group A than from group B (67% vs. 10%, P = 0.02). If the patients with the highest uptake scores of 2, 3, and 4 were considered to be positive for local recurrence or metastasis, there would be no significant difference between the positive rates of groups A and B (83% vs. 90%, P = 0.7). However, the mean SUV max of positive results was significantly lower for group A than for group B (3.1 +/- 0.9 and 6.6 +/- 3.5, respectively, P = 0.02). CONCLUSIONS: The preliminary results suggested that FDG uptake in DTC may be negatively influenced by I-131 therapy within 4 months, resulting in lower FDG uptake and more equivocal results. Further studies are necessary to determine whether it is secondary to "metabolic stunning" caused by I-131 therapy.     

FDG avidity and PET/CT patterns in primary gastric lymphoma

PURPOSE: The use of 18F-fluoro-deoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) in primary gastric lymphoma (PGL) is challenging due to physiologic FDG activity in the stomach and variability in the degree of uptake in various histologic subtypes. This study assesses FDG avidity and PET/CT patterns in newly diagnosed PGL. METHODS: Sixty-two PET/CT studies of newly diagnosed PGL were reviewed (24 low-grade mucosa-associated lymphoid tissue [MALT], 38 aggressive non-Hodgkin's lymphoma [AGNHL]). FDG avidity, patterns (focal/diffuse), and intensity (visually vs. the liver and SUVmax) were assessed and compared to 27 controls. Gastric CT abnormalities and extragastric sites were recorded. RESULTS: Gastric FDG uptake was found in 55/62 (89%) PGL (71% MALT vs. 100% AGNHL, p < 0.001) and 63% controls. A diffuse pattern was found in 60% PGL (76% MALT vs. 53% AGNHL, p = NS) and 47% controls. FDG uptake higher than liver was found in 82% PGL (58% MALT vs. 97% AGNHL, p < 0.05) and 63% controls. SUVmax in FDG-avid PGLs was 15.3 +/- 11.7 (5.4 +/- 2.9 MALT vs. 19.7 +/- 11.5 AGNHL, p < 0.001) and 4.6 +/- 1.4 in controls. CT abnormalities were found in 79% PGL (thickening, n = 49; ulcerations, n = 22). Extra-gastric FDG-avid sites were seen in none of MALT, but 61% of AGNHL (nodal, n = 18; nodal and extranodal, n = 5). CONCLUSIONS: FDG avidity was present in 89% of PGLs, including all patients with AGNHL but only 71% of MALT. FDG uptake can be differentiated, in particular in AGNHL-PGL, from physiologic tracer activity by intensity but not by pattern. Extragastric foci on PET and structural CT abnormalities are additional parameters that can improve PET/CT assessment of PGL. Defining FDG avidity and PET/CT patterns in AGNHL and a subgroup of MALT-PGL before treatment may be important for further monitoring therapy response.     

肿瘤非手术治疗后FDG PET随访的临床价值

目的　探讨 FDG PET影像诊断在肿瘤非手术治疗后临床随访中的价值。　方法　选择实质性肿瘤高强度聚焦超声 (HIFU)治疗后 2 1例 ,鼻咽癌患者放射治疗后 14例 ,共 35例 ,随访中同期行 FDG PET和 CT、MRI检查 ,并将结果进行双盲比较。　结果　 2 1例实质性肿瘤 HIFU治疗后 2～ 3个月复查 ,19例 CT、MRI表现密度和信号有变化 ,但形态、大小未见明显改变 ,另 2例 CT、MRI密度和信号变化不明显 ;PET示 17例肿瘤中心大部分放射性分布缺损 ,但以肿瘤边缘部分为主仍有 FDG代谢活跃现像 ,提示部分肿瘤存活 ,其中 6例在 FDG代谢活跃局部经穿刺活检证实肿瘤存活 ;4例 PET表现为 FDG摄取缺损 ,其中 1例局部穿刺活检证实为坏死组织。 14例鼻咽癌放疗后 12～ 18个月复查 ,CT和 MRI提示 11例未见局部肿瘤复发 ,PET显示其中 3例有局灶性 FDG浓聚病变 ,其中 1例局部穿刺活检证实为局部肿瘤复发 ;2例 CT和 MRI提示肿瘤复发 ,FDG显像病变处有明显的放射性浓聚 ;余 1例放射治疗后脑损伤 FDG PET显示为放射性分布缺损区。　结论　 FDG显像在实质性肿瘤 HIFU治疗后疗效判断和鼻咽癌放射治疗后肿瘤复发诊断上较 CT和 MRI准确 ,两者结合分析在临床随访中更具有明显的优势     

Initial evaluation of <Superscript>18</Superscript>F-fluorothymidine (FLT) PET/CT scanning for primary pancreatic cancer

Purpose The aim of this study was to evaluate the potential of ¹⁸F-fluorothymidine (FLT) PET/CT for imaging pancreatic adenocarcinoma. Methods This was a pilot study of five patients (four males, one female) with newly diagnosed and previously untreated pancreatic adenocarcinoma. Patients underwent FLT PET/CT, ¹⁸F-fluorodeoxyglucose (FDG) PET/CT, and contrast-enhanced CT scanning before treatment. The presence of cancer was confirmed by histopathological analysis at the time of scanning in all five patients. The degree of FLT and FDG uptake at the primary tumor site was assessed using visual interpretation and semi-quantitative SUV analyses. Results The primary tumor size ranged from 2.5×2.8 cm to 3.5 × 7.0 cm. The SUV of FLT uptake within the primary tumor ranged from 2.1 to 3.1. Using visual interpretation, the primary cancer could be detected from background activity in two of five patients (40%) on FLT PET/CT. By comparison, FDG uptake was higher in each patient with a SUV range of 3.4 to 10.8, and the primary cancer could be detected from background in all five patients (100%). Conclusions In this pilot study of five patients with primary pancreatic adenocarcinoma, FLT PET/CT scanning showed poor lesion detectability and relatively low levels of radiotracer uptake in the primary tumor.     

FDG PET in solitary metastastic/secondary tumor of the kidney: A report of three cases and a review of the relevant literature

Metastatic tumors or secondary lymphoma of the kidney are rare and can often be missed on conventional computed tomography (CT) imaging. On the other hand, many types of metastatic tumor or lymphoma can be detected clearly as hotspots of elevated uptake on FDG PET. However, excreted FDG present in the urinary tract mimics these findings and interferes with image reading. Careful investigation of the renal cortex by FDG PET and review of anatomical images, such as the findings of CT and MRI, have important roles in the detection of renal tumor. Here, we present three cases of solitary metastatic/secondary tumor of the kidney, and discuss the features of the lesions on FDG PET in comparison with their appearance on CT.     

Benign Schwannoma Mimicking Metastatic Lesion on F-18 FDG PET/CT in Differentiated Thyroid Cancer

We report a case of benign schwannoma mimicking metastatic carcinoma. A 55-year-old female with papillary thyroid carcinoma underwent total thyroidectomy. F-18 fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) demonstrated a focal hypermetabolic lesion with maximum standardized uptake value (SUVmax) 5.3 at the right chest wall. Conventional chest CT demonstrated a 5.4 cm ovoid mass lesion between the intercostal muscles and liver. Pathology revealed a schwannoma by tumor excision. This case demonstrates that benign schwannoma may demonstrate FDG uptake mimicking metastatic carcinoma.     

Diagnostic accuracy of FDG PET imaging for the detection of recurrent or metastatic gynecologic cancer

PURPOSE: This study evaluated the diagnostic role and accuracy of positron emission tomography (PET) using 2-[F-18]fluoro-2-deoxy-D-glucose (FDG) for the detection of tumor foci in patients with suspected recurrent or metastatic lesions of gynecologic cancers. MATERIALS AND METHODS: FDG PET imaging was performed on 51 patients with a previous history of gynecologic cancer who were referred for a clinical suspicion of recurrent disease. PET acquisition was started 50-60 min after the intravenous injection of 5-6 MBq/kg FDG in all patients. The PET images were interpreted visually, and tracer uptake was quantitated as the standardized uptake value adjusted to body weight (SUV) in the lesions showing FDG uptake. The accuracy of the PET results was assessed by a consensual verdict based on histology, cytology, other imaging and clinical follow-up. RESULTS: FDG PET correctly diagnosed 33 of 36 patients with recurrent disease and 12 of 15 patients without recurrence. On patient-based analysis, the sensitivity, specificity and accuracy of FDG PET were 91.7%, 80.0% and 88.2%, respectively, depending on the selected scheme for visual scoring of the lesions. The area index in receiver-operating characteristic analysis was 0.95 for patient detection. Malignant lesions accumulated significantly more FDG than the benign ones (the mean SUVs were 3.7 +/- 1.9 and 1.6 +/- 1.1, respectively, p = 0.004). The sensitivity and specificity in correct identification of tumor recurrence or metastases using a threshold SUV 1.9 were 88.8% and 66.7% in contrast to the visual analysis (sensitivity 96.4%, specificity 50%) on a lesion-based analysis. The partial volume effect of SUV in a few small lesions and the presence of bone lesions in which FDG uptake was relatively low might be the reason for the lower sensitivity in SUV analysis. FDG PET was valuable when CT/MRI was negative or inconclusive, and in patients with elevated tumor marker levels as well as with normal tumor marker levels when recurrence was suspected clinically. However, PET failed to visualize some small metastatic lesions in lung and bone, and showed falsely high FDG uptake in some benign lesions. CONCLUSION: The results indicated that FDG PET is a reliable and accurate diagnostic method for detecting recurrent or metastatic gynecologic cancer particularly lymph node metastases. Although the sensitivity of PET for detecting small metastases was relatively limited, the overall sensitivity of FDG PET was significantly higher than morphologic imaging.