18F-FDG联合11C-乙酸盐PET-CT在肝癌诊断中的应用

原发性肝癌位居发展中国家肿瘤发病率的第三位,严重威胁人们的健康和生命,CT、MRI、超声等传统影像检查方法虽然可以诊断大部分病灶,但对于传统检查方法难以诊断的原发性肝癌,PEF-CT可以作为有效的补充检查方法。18F-FDG PET-CT诊断原发性肝癌的阳性率较低,对于18F-FDG PET-CT阴性的肝脏病灶,再结合...     

11C-胆碱和18F-FDG在肿瘤PET中的比较

11C-胆碱是最近研制的一种正电子肿瘤阳性显像剂,在肿瘤/非靶组织的比值高于18F-FDG,特别在脑肿瘤和前列腺癌显像方面较18F-FDG显示出优势.11C-胆碱和18F-FDG在脑肿瘤、肺癌、食道癌和前列腺癌的诊断方面各有优劣,两者的摄取机理与显像方法也不同.除了11C-胆碱,还有18F-氟代胆碱(18F-fluorocholine),其临床价值有待更多的研究来证实.     

Positron emission tomography for prostate, bladder, and renal cancer

Prostate cancer, renal cancer, bladder, and other urothelial malignancies make up the common tumors of the male genitourinary tract. For prostate cancer, common clinical scenarios include managing the patient presenting with 1) low-risk primary cancer; 2) high-risk primary cancer; 3) prostate-specific antigen (PSA) recurrence after apparently successful primary therapy; 4) progressive metastatic disease in the noncastrate state; and 5) progressive metastatic disease in the castrate state. These clinical states dictate the appropriate choice of diagnostic imaging modalities. The role of positron emission tomography (PET) is still evolving but is likely to be most important in determining early spread of disease in patients with aggressive tumors and for monitoring response to therapy in more advanced patients. Available PET tracers for assessment of prostate cancer include FDG, 11C or 18F choline and acetate, 11C methionine, 18F fluoride, and fluorodihydrotestosterone. Proper staging of prostate cancer is particularly important in high-risk primary disease before embarking on radical prostatectomy or radiation therapy. PET with 11C choline or acetate, but not with FDG, appears promising for the assessment of nodal metastases. PSA relapse frequently is the first sign of recurrent or metastatic disease after radical prostatectomy or radiation therapy. PET with FDG can identify local recurrence and distant metastases, and the probability for a positive test increases with PSA. However, essentially all studies have shown that the sensitivity for recurrent disease detection is higher with either acetate or choline as compared with FDG. Although more data need to be gathered, it is likely that these two agents will become the PET tracers of choice for staging prostate cancer once metastatic disease is strongly suspected or documented. 18F fluoride may provide a more sensitive bone scan and will probably be most valuable when PSA is greater than 20 ng/mL in patients with high suspicion or documented osseous metastases. Several studies suggest that FDG uptake in metastatic prostate cancer lesions reflects the biologic activity of the disease. Accordingly, FDG can be used to monitor the response to chemotherapy and hormonal therapy. Androgen receptor imaging agents like fluorodihydrotestosterone are being explored to predict the biology of treatment response for progressive tumor in late stage disease in castrated patients. The assessment of renal masses and primary staging of renal cell carcinoma are the domain of helical CT. PET with FDG may be helpful in the evaluation of "equivocal findings" on conventional studies, including bone scan, and also in the differentiation between recurrence and posttreatment changes. The value of other PET tracers in renal cell carcinoma is under investigation. Few studies have addressed the role of PET in bladder cancer. Because of its renal excretion, FDG is not a useful tracer for the detection of primary bladder tumors. The few studies that investigated its role in the detection of lymph node metastases at the time of primary staging were largely disappointing. Bladder cancer imaging with 11C choline, 11C methionine, or 11C- acetate deserves further study.     

Combined 18F-FDG and 11C-methionine PET scans in patients with newly progressive metastatic prostate cancer.

Metastatic prostate cancer may respond initially to hormone suppression, with involution of tumor sites, but ultimate tumor progression is inevitable. Our aim was to detect the proportion of bone and soft-tissue lesions that represent metabolically active tumor sites in patients with progressive metastatic prostate cancer. METHODS: In a prospective study, we compared 18F-FDG and L-methyl-11C-methionine (11C-methionine) PET with conventional imaging modalities (CIM), which included the combination of 99mTc-methylene diphosphonate scintigraphy, CT, or MRI. Twelve patients with prostate cancer, increasing levels of prostate-specific antigen (PSA), and at least 1 site (index lesion) with new or increasing disease on CIM were studied. The total numbers of soft-tissue and bone-tissue lesions, in a site-by-site comparison, were calculated for all imaging modalities. RESULTS: The sensitivities of 18F-FDG PET and 11C-methionine PET were 48% (167/348 lesions) and 72.1% (251/348 lesions), respectively, with CIM being used as the 100% reference (348/348). 11C-Methionine PET identified significantly more lesions than 18F-FDG PET (P < 0.01). All 12 patients with progressive metastatic prostate cancer had at least 1 lesion site of active metabolism for 18F-FDG or 11C-methionine, which could be used as an index lesion to monitor the metabolic response to therapy. A significant proportion of lesions (26%) had no detectable metabolism of 18F-FDG or 11C-methionine. Although technical factors cannot be totally excluded, we believe that metabolically inactive sites may be necrotic or dormant. More than 95% (251/258) of metabolically active sites (72% of the total number of lesions detected by CIM) metabolize 11C-methionine. 18F-FDG uptake is more variable, with 65% of metabolically active sites (48% of the total number of lesions detected by CIM). CONCLUSION: These findings reflect the different biologic characteristics of the lesions in a heterogeneous tumor such as prostate cancer and suggest that a time-dependent metabolic cascade may occur in advanced prostate cancer, with initial uptake of 11C-methionine in dormant sites followed by increased uptake of 18F-FDG during progression of disease.     

Positron emission tomography in gynecologic cancer

Most positron emission tomography (PET) imaging studies in gynecologic cancer are performed using (18)F-fluorodeoxyglucose (FDG). It contributes valuable information in primary staging of untreated advanced cervical cancer, in the post-treatment surveillance with unexplained tumor marker (such as squamous cell carcinoma antigen [SCC-Ag]) elevation or suspicious of recurrence, and restaging of potentially curable recurrent cervical cancer. Its value in early-stage resectable cervical cancer is questionable. In ovarian cancer, FDG-PET provides benefits for those with plateaued or increasing abnormal serum CA 125 (>35 U/mL), computed tomography and/or magnetic resonance imaging (CT-MRI) defined localized recurrence feasible for local destructive procedures (such as surgery, radiotherapy, or radiofrequency ablation), and clinically suspected recurrent or persistent cancer for which CT-guide biopsy cannot be performed. The role of FDG-PET in endometrial cancer is relatively less defined because of the lack of data in the literature. In our prospective study, FDG-PET coupled with MRI-CT may facilitate optimal management of endometrial cancer in well-selected cases. The clinical impact was positive in 29 (48.3%) of the 60 scans, 22.2% for primary staging, 73.1% for post-therapy surveillance, and 57.1% after salvage therapy, respectively. Scant studies have been reported in the management of vulvar cancer using FDG-PET. More data are needed. Gestational trophoblastic neoplasia is quite unique in biological behavior and clinical management. Our preliminary results suggest that FDG-PET is potentially useful in selected gestational trophoblastic neoplasia by providing a precise metastatic mapping of tumor extent up front, monitoring response, and localizing viable tumors after chemotherapy. The evaluation of a diagnostic tool, such as PET, is usually via comparing the diagnostic efficacy (sensitivity, specificity, etc), by using a more sophisticated receiver operating curve method, or the proportion of treatment been modified. Evaluating PET by clinical benefit is specific to the individual tumor and an attractive new endpoint.     

Positron emission tomography in lung cancer

Carcinoma of the lung is one of the most frequent malignancies and a major cause of mortality. The use of positron emission tomography (PET) has been extensively investigated in patients with carcinoma of the lung and has established clinical utility and cost-effectiveness in characterization of solitary pulmonary nodules and preoperative staging of carcinoma of the lung. Evolving applications in carcinoma of the lung include detection of recurrence, assessment of treatment response, radiotherapy planning, and prognosis. In addition, there is developing interest in combined anatomic/metabolic imaging and new tracer techniques, in particular gene expression imaging. This review aims to present existing data supporting the use of PET in carcinoma of the lung and to explore the evolving indications and future prospects of PET and lung cancer.     

11C-acetate PET imaging of prostate cancer.

11C-Acetate can act as a probe of tissue metabolism through entry into catabolic or anabolic metabolic pathways as mediated by acetyl-coenzyme A. The uptake of (11)C-acetate in prostate cancer was investigated to determine whether this tracer has potential in tumor identification. METHODS: Twenty-two patients with prostate cancer underwent PET after intravenous administration of 740 MBq (11)C-acetate. Eighteen of the 22 patients were also investigated with (18)F-FDG PET. Standardized uptake values (SUVs) for each tumor were investigated for tracer activity at 10-20 min after (11)C-acetate and 40-60 min after (18)F-FDG administration. RESULTS: Adenocarcinoma of the prostate showed variable uptake of (11)C-acetate, with SUVs ranging from 3.27 to 9.87. In contrast, SUVs for (18)F-FDG ranged from 1.97 to 6.34. By visual inspection, (11)C-acetate accumulation in primary prostate tumors was positive in all patients, whereas (18)F-FDG accumulation was positive in only 15 of 18 patients. (11)C-Acetate PET in a patient with lymph node metastasis showed high intrapelvic accumulation corresponding to metastatic sites. Similarly, 2 patients with bone metastases were (11)C-acetate avid. CONCLUSION: (11)C-Acetate shows marked uptake in prostate cancer and is more sensitive in detection of prostate cancer than is (18)F-FDG PET. (11)C-Acetate represents a new tracer for detection of prostate cancer with PET, measuring radiopharmaceutical uptake pathways that are different from those measured by (18)F-FDG.     

Positron emission tomography in thyroid cancer management

Selected patients with thyroid cancer can benefit from the use of PET imaging with FDG or with I-124. The PET scan impacts on management by providing (1) more accurate information about staging of patients in terms of extent of tumor for better treatment planning, especially in patients who do not concentration radioactive I-131; (2) the relationship of tumor involvement to vital structures, especially in the neck and central nervous system; and (3) prognostic information (an SUV > 10 and extensive PET + disease connotes a poor prognosis in advanced patients). In the occasional patient, surgically respectable disease has been identified on PET with the result that the patient has been rendered no evident disease with treatment. PET has also been used in the follow-up of patients who have been treated for thyroid cancer, to assess response. PET may also be useful for lesion specific dosimetry, with I-124. The combination of PET and CT in the same gantry facilitates localization of thyroid cancer PET scan abnormalities in relationship to critical organs and structures.     

Grading of brain glioma with 1-11C-acetate PET: comparison with 18F-FDG PET

The objective of this study is to reevaluate the clinical significance of 1-11C-acetate (ACE) positron emission tomography (PET) in patients with brain glioma, in comparison with 18F-fluorodeoxyglucose (FDG) PET. METHODS: Ten patients with histologically proven glioma were included in this study. They underwent PET examination with both FDG and ACE on separate days. For ACE PET, 20-min data acquisition was performed just after the administration of 740 MBq of ACE; 10-20-min data were used for the analysis. FDG PET data acquisition for 10 min started 60 min postinjection of 370 MBq of FDG, approximately. Both reconstructed images were converted to standardized uptake value (SUV) images for patient body weight and injected dose. Regions of interest were placed on the tumor and the contralateral cerebral cortex, and SUV and tumor-to-cortex ratio (T/C) were calculated; these values were compared between high- and low-grade gliomas. RESULTS: SUV and T/C of ACE PET showed significant difference (SUV: 2.63+/-0.46 vs. 1.85+/-0.56, P=.03; T/C: 2.36+/-0.63 vs. 1.14+/-0.36, P=.02). In contrast, FDG PET revealed no significant difference in SUV or T/C between high- and low-grade gliomas (SUV: 7.13+/-4.31 vs. 4.71+/-1.27, P=.31; T/C: 0.98+/-0.55 vs. 0.62+/-0.09, P=.22). CONCLUSION: This preliminary study revealed that ACE PET is a promising tracer for the grading of brain glioma.     

1-11C-acetate kinetics of prostate cancer.

(18)F-FDG is in widespread use in cancer imaging but has limited utility in staging and monitoring of prostate cancer. 1-(11)C-Labeled acetate, a substrate for the citric acid cycle, is superior. The kinetics of prostate tumors were investigated. METHODS: Ten patients with primary prostate cancer, 10 with recurrent tumor, and 2 men with benign prostate hypertrophy were studied. After administration of 5.5 MBq/kg 1-(11)C-acetate, dynamic PET of the pelvis was acquired for 20 min. Images were reconstructed with iterative algorithms, and corrections for attenuation and scatter were applied. Factor analysis produced factor images, representing iliac vessels and the prostate from which blood-input and tissue-output functions were derived with simple thresholding techniques. Five different kinetic models were applied to the dynamic data to estimate the rate constants. RESULTS: The standard 3-compartment, 2-tissue model was able to describe 1-(11)C-acetate kinetics of the prostate. The model could be reduced to 3 parameters by setting the tissue blood fraction and release from the second tissue compartment (k(4)) to zero. Correction for metabolites appeared to be necessary. This reduced model performed marginally better than a 2-compartment model. A significant correlation was found between the influx rate constant (K) and acetate uptake (standardized uptake value) for primary tumors (r = 0.91), whereas there was no correlation for recurrent tumors (r = -0.17). Patlak graphical analysis provided accurate parameter estimates. CONCLUSION: A 3-compartment, 3-parameter model is able to describe adequately the acetate kinetics in prostate cancer. Significant differences between primary and recurrent cancer were found for transport k(1), influx K, distribution volume V(d), as well as early (6-10 min) and late (15-20 min) 1-(11)C-acetate uptake.     

Positron emission tomography

Positron emission tomography is a sophisticated, physiology-based imaging technique that provides information about the function of tissues and organs. Combining PET data with computed tomography or magnetic resonance images provides clinicians with physiological information linked to an anatomical site. This overview discusses the biological principles underlying the technology, PET radiopharmaceuticals, PET imaging facilities, specific imaging applications and reimbursement issues.     

Positron emission tomography with [18F]FDG for therapy response monitoring in lymphoma patients

Lymphomas are a heterogeneous group of diseases with differing histopathology, clinical behaviour, response to therapy and outcome. Lymphomas are highly sensitive to chemotherapy and radiotherapy, and the recent developments in treatment have considerably improved clinical outcome. However, there is increasing recognition that this has been at the cost of long-term treatment-related effects in a relatively young patient population. Thus, one of the most challenging aspects in the imaging of lymphoma patients is tailoring the intensity of the treatment to the individual patient. This paper reviews recently published data concerning the use of fluorine-18 fluorodeoxyglucose positron emission tomography ([¹⁸F]FDG-PET) for therapy monitoring in lymphoma patients and highlights the shortcomings and future directions. A temporary strategy for the implementation of [¹⁸F]FDG-PET in the management of lymphoma patients is proposed.

     

Positron emission tomography: brain tumors and lung cancer

F-18 fluorodeoxyglucose positron emission tomography is a uniquely powerful diagnostic tool that noninvasively provides information that is critical to appropriate clinical management of patients with non-small cell lung cancer. Not only does the functional information provided by PET complement and clarify the anatomic information supplied by CT and MR imaging, but the superior sensitivity and negative predictive value of PET allow for improved accuracy in diagnosis, prognosis, staging, and monitoring the effects of treatment. With better information at their disposal, clinicians and patients are able to make better-informed decisions, contributing to more appropriate and more cost-effective medical care. Truly, FDG-PET has earned its place as the new standard of care in imaging non-small cell lung cancer.