Fluorine-18-labeled Fluorodeoxyglucose Research Articles

AI Transformers for Radiation Dose Reduction in Serial Whole-Body PET Scans

To develop a deep learning approach that enables ultra-low-dose, 1% of the standard clinical dosage (3 MBq/kg), ultrafast whole-body PET reconstruction in cancer imaging.In this Health Insurance Portability and Accountability Act-compliant study, serial fluorine 18-labeled fluorodeoxyglucose PET/MRI scans of pediatric patients with lymphoma were retrospectively collected from two cross-continental medical centers between July 2015 and March 2020. Global similarity between baseline and follow-up scans was used to develop Masked-LMCTrans, a longitudinal multimodality coattentional convolutional neural network (CNN) transformer that provides interaction and joint reasoning between serial PET/MRI scans from the same patient. Image quality of the reconstructed ultra-low-dose PET was evaluated in comparison with a simulated standard 1% PET image. The performance of Masked-LMCTrans was compared with that of CNNs with pure convolution operations (classic U-Net family), and the effect of different CNN encoders on feature representation was assessed. Statistical differences in the structural similarity index measure (SSIM), peak signal-to-noise ratio (PSNR), and visual information fidelity (VIF) were assessed by two-sample testing with the Wilcoxon signed rank t test.The study included 21 patients (mean age, 15 years ± 7 [SD]; 12 female) in the primary cohort and 10 patients (mean age, 13 years ± 4; six female) in the external test cohort. Masked-LMCTrans-reconstructed follow-up PET images demonstrated significantly less noise and more detailed structure compared with simulated 1% extremely ultra-low-dose PET images. SSIM, PSNR, and VIF were significantly higher for Masked-LMCTrans-reconstructed PET (P < .001), with improvements of 15.8%, 23.4%, and 186%, respectively.Masked-LMCTrans achieved high image quality reconstruction of 1% low-dose whole-body PET images.Keywords: Pediatrics, PET, Convolutional Neural Network (CNN), Dose Reduction Supplemental material is available for this article. © RSNA, 2023.

18F-FDG PET/MRI in Detection of Pulmonary Malignancies: A Systematic Review and Meta-Analysis.

Background There have been conflicting results regarding fluorine 18-labeled fluorodeoxyglucose (18F-FDG) PET/MRI diagnostic performance in lung malignant neoplasms. Purpose To evaluate the diagnostic performance of 18F-FDG PET/MRI for the detection of pulmonary malignant neoplasms. Materials and Methods A systematic search was conducted within the Scopus, Web of Science, and PubMed databases until December 31, 2021. Published original articles that met the following criteria were considered eligible for meta-analysis: (a) detecting malignant lesions in the lung, (b) comparing 18F-FDG PET/MRI with a valid reference standard, and (c) providing data for the meta-analytic calculations. A hierarchical method was used to pool the performances. The bivariate model was used to find the summary points and 95% CIs. The hierarchical summary receiver operating characteristic model was used to draw the summary receiver operating characteristic curve and calculate the area under the curve. The Higgins I2 statistic and Cochran Q test were used for heterogeneity assessment. Results A total of 43 studies involving 1278 patients met the inclusion criteria and were included in the meta-analysis. 18F-FDG PET/MRI had a pooled sensitivity and specificity of 96% (95% CI: 84, 99) and 100% (95% CI: 98, 100), respectively. 18F-FDG PET/CT had a pooled sensitivity and specificity of 99% (95% CI: 61, 100) and 99% (95% CI: 94, 100), respectively, which were comparable with those of 18F-FDG PET/MRI. At meta-regression, studies in which contrast media (P = .03) and diffusion-weighted imaging (P = .04) were used as a part of a pulmonary 18F-FDG PET/MRI protocol showed significantly higher sensitivities. Conclusion Fluorine 18-labeled fluorodeoxyglucose (18F-FDG) PET/MRI was found to be accurate and comparable with 18F-FDG PET/CT in the detection of malignant pulmonary lesions, with significantly improved sensitivity when advanced acquisition protocols were used. © RSNA, 2023 Supplemental material is available for this article.

Comparison of 68Ga-FAPI and 18F-FDG PET/CT in the Evaluation of Advanced Lung Cancer.

Background Gallium 68 (68Ga)-labeled fibroblast-activation protein inhibitor (FAPI) has recently been introduced as a promising tumor imaging agent. Purpose To compare 68Ga-FAPI PET/CT with fluorine 18 (18F)-labeled fluorodeoxyglucose (FDG) PET/CT in evaluating lung cancer. Materials and Methods In this prospective study conducted from September 2020 to February 2021, images from participants with lung cancer who underwent both 68Ga-FAPI and 18F-FDG PET/CT examinations were analyzed. The tracer uptakes, quantified by maximum standardized uptake value (SUVmax) and target-to-background ratio (TBR), were compared for paired positive lesions between both modalities using the paired t test or Wilcoxon signed-rank test. Results Thirty-four participants (median age, 64 years [interquartile range: 46-80 years]; 20 men) were evaluated. From visual evaluation, 68Ga-FAPI PET/CT and 18F-FDG PET/CT showed similar performance in the delineation of primary tumors and detection of suspected metastases in the lungs, liver, and adrenal glands. The metabolic tumor volume in primary and recurrent lung tumors showed no difference between modalities (mean: 11.6 vs 10.8, respectively; P = .68). However, compared with 18F-FDG PET/CT, 68Ga-FAPI PET/CT depicted more suspected metastases in lymph nodes (356 vs 320), brain (23 vs 10), bone (109 vs 91), and pleura (66 vs 35). From semiquantitative evaluation, the SUVmax and TBR of primary or recurrent tumors, positive lymph nodes, bone lesions, and pleural lesions at 68Ga-FAPI PET/CT were all higher than those at 18F-FDG PET/CT (all P < .01). Although SUVmax of 68Ga-FAPI and 18F-FDG in brain metastases were not different (mean SUVmax: 9.0 vs 7.4, P = .32), TBR was higher with 68Ga-FAPI than with 18F-FDG (mean: 314.4 vs 1.0, P = .02). Conclusion Gallium 68-labeled fibroblast-activation protein inhibitor PET/CT may outperform fluorine 18-labeled fluorodeoxyglucose PET/CT in staging lung cancer, particularly in the detection of metastasis to the brain, lymph nodes, bone, and pleura. © RSNA, 2022 Online supplemental material is available for this article. See also the editorial by Jacobson and Van den Abbeele in this issue.

Neoadjuvant Trastuzumab, Pertuzumab, and Docetaxel vs Trastuzumab Emtansine in Patients With ERBB2-Positive Breast Cancer

Trastuzumab emtansine (T-DM1) is presently approved for treatment of advanced breast cancer and after incomplete response to neoadjuvant therapy, but the potential of T-DM1 as monotherapy is so far unknown. To assess pathologic complete response (pCR) to standard neoadjuvant therapy of combination docetaxel, trastuzumab, and pertuzumab (DTP) vs T-DM1 monotherapy in patients with ERBB2 (formerly HER2)-positive breast cancer. This randomized phase 2 trial, conducted at 9 sites in Sweden, enrolled 202 patients between December 1, 2014, and October 31, 2018. Participants were 18 years or older, with ERBB2-positive tumors larger than 20 mm and/or verified lymph node metastases. Analysis was performed on an intention-to-treat basis. Patients were randomized to receive 6 cycles of DTP (standard group) or T-DM1 (investigational group). Crossover was recommended at lack of response or occurrence of intolerable toxic effects. Assessment with fluorine 18-labeled fluorodeoxyglucose (18F-FDG) positron emission tomography combined with computed tomography (PET-CT) was performed at baseline and after 2 and 6 treatment cycles. Pathologic complete response, defined as ypT0 or Tis ypN0. Secondary end points were clinical and radiologic objective response; event-free survival, invasive disease-free survival, distant disease-free survival, and overall survival; safety; health-related quality of life (HRQoL); functional and biological tumor characteristics; and frequency of breast-conserving surgery. Overall, 202 patients were randomized; 197 (99 women in the standard group [median age, 51 years (range, 26-73 years)] and 98 women in the investigational group [median age, 53 years (range, 28-74 years)]) were evaluable for the primary end point. Pathologic complete response was achieved in 45 patients in the standard group (45.5%; 95% CI 35.4%-55.8%) and 43 patients in the investigational group (43.9%; 95% CI 33.9%-54.3%). The difference was not statistically significant (P = .82). In a subgroup analysis, the pCR rate was higher in hormone receptor-negative tumors than in hormone receptor-positive tumors in both treatment groups (45 of 72 [62.5%] vs 45 of 125 [36.0%]). Three patients in the T-DM1 group experienced progression during therapy. In an exploratory analysis, tumor-infiltrating lymphocytes at 10% or more (median) estimated pCR significantly (odds ratio, 2.76; 95% CI, 1.42-5.36; P = .003). Response evaluation with 18F-FDG PET-CT revealed a relative decrease of maximum standardized uptake value by equal to or greater than 68.7% (median) was associated with pCR (odds ratio, 6.74, 95% CI, 2.75-16.51; P < .001). In this study, treatment with standard neoadjuvant combination DTP was equal to T-DM1. ClinicalTrials.gov Identifier: NCT02568839; EudraCT number: 2014-000808-10.

A Case of Synchronous Lung Adenocarcinoma and Extranodal Marginal Zone B-Cell Lymphoma of Mucosa-Associated Lymphoid Tissue Type

Abstract SESSION TYPE: Cancer Global Case Report PostersPRESENTED ON: Tuesday, October 23, 2012 at 01:30 PM - 02:30 PMINTRODUCTION: Extranodal marginal zone B-cell lymphoma (extranodal MZL) of mucosa-associated lymphoid tissue (MALT) type, also called MALT lymphoma, is a distinct subgroup of non-Hodgkin's lymphoma (NHL). More than two thirds of primary pulmonary NHLs are extranodal MZLs but they account for less than 0.5% of all primary lung neoplasms. Only a few cases of simultaneous lung cancer and pulmonary extranodal MZL have been reported. Also, it is extremely rare that primary extranodal MZL occurs in the large airways. To our knowledge, only one case of lung cancer coexisting with extranodal MZL of the large airway has been reported. We report a case of synchronous lung adenocarcinoma and primary extranodal MZL of the left main bronchus.CASE PRESENTATION: A 60-year old woman was referred to our hospital with a pulmonary nodule in the right upper lung seen on chest radiograph during a routine health checkup. She had never smoked. A chest radiograph showed a nodule in the right upper lung. A chest computed tomographic (CT) scan showed a peripherally located 2.4 × 1.8 cm sized solid nodule in the anterior segment of the right upper lobe. Fluorine 18-labeled fluorodeoxyglucose (FDG)-positron emission tomography (PET)-CT scan revealed abnormal FDG uptake in the right upper lobe lung nodule and in the right hilar lymph node. She underwent CT image-guided percutaneous core needle biopsy of the nodule in the right upper lobe. Additionally, a flexible bronchoscopic examination was performed to identify the endobronchial lesion. At bronchoscopy, a few small variable-sized protrusions were observed in the proximal left main bronchus and a biopsy was performed . The needle biopsy specimens of the right lung nodule showed non-mucinous adenocarcinoma. Immunohistochemical stains were positive for CK7 and TTF-1, and negative for CK20. Histopathology of the bronchoscopic biopsy specimens of the left main bronchus lesions showed diffuse proliferation of atypical lymphoid cells beneath the mucosal epithelium. Immunohistochemical stains showed diffuse strong positive for CD20, and were negative for CKpan and CD10. The bronchial lesion was diagnosed as extranodal marginal zone B-cell lymphoma of MALT type. She underwent right upper lobectomy and lymph node dissection for the lung adenocarcinoma. However, she did not receive specialized therapy for extranodal MZL of the left main bronchus. Since then she has been observed regularly.DISCUSSION: Synchronous primary malignancy and extranodal MZL in the same anatomical sites, such as stomach and lung is very unusual. To our knowledge, there is only one other report showing the coexistence of lung cancer and pulmonary extranodal MZL of the large airway. However, in that case, the histology of lung cancer was squamous cell carcinoma. The present case is the first report of the simultaneous occurrence of lung adenocarcinoma and pulmonary extranodal MZL of the large airway. The cause of the synchronous lesions in our case is uncertain. We postulate that a pulmonary extranodal MZL may coincide with a lung adenocarcinoma by accident. Little is known about the mechanism of the simultaneous occurrence of these different tumors. Moreover, the two different malignancies were located in different lungs in this case. However, other possible causes may include common etiologic factors and genetic or epigenetic alterations participating in the development of both the lung adenocarcinoma and extranodal MZL. Further studies will be required to clarify the relationship between lung adenocarcinoma and pulmonary extranodal MZL. It is necessary to accumulate more cases with both malignancies.CONCLUSIONS: In conclusion, we report a unique case of pulmonary extranodal MZL of main bronchus coexisting with lung adenocarcinoma. The patient was asymptomatic and was diagnosed with pulmonary extranodal MZL by chance during investigation of an endobronchial lesion.1) Jaffe ES, Harris NL, Stein H, Vardiman JW. World Health Organization Classification of Tumors. Pathology and Genetics of Tumors of Haematopoietic and Lymphoid tissue. Lyon: International Agency for Research on Cancer; 2001.DISCLOSURE: The following authors have nothing to disclose: Chi Young Jung, Young June JeonNo Product/Research Disclosure InformationKeimyung University Dongsan Hospital, Daegu, Republic of Korea.

Role of Fluorine 18 Fluorodeoxyglucose Positron Emission Tomography-Computed Tomography in Focal and Generalized Infectious and Inflammatory Disorders

Several advances in imaging have become part of the work-up for localization, diagnosis, and management of infectious diseases and inflammatory disorders. Utility of multiple imaging modalities is a time-consuming step, and significant numbers of patients remain undiagnosed despite utilization of series of tests. Inflammatory cells have avidity for fluorine 18-labeled fluorodeoxyglucose ((18)F-FDG), and thus positron emission tomographic-computed tomographic (PET-CT) hybrid imaging provides anatomical and metabolic information that can be used to define the extent of infectious and inflammatory diseases and assess response to treatment. PET-CT provides a "one-stop test" in which use of hybrid imaging provides anatomical and metabolic information. The extent of disease is defined quickly, and response to treatment can be assessed. This modality also helps define the metastatic and/or septic foci where there is lack of localizing symptoms. More recently, there is increasing awareness among clinicians regarding the ability of PET-CT to help in diagnosing, characterizing, and assessing inflammatory disorders. This article reviews the usefulness of this imaging modality.

Imaging appearances of pulmonary mucosa-associated lymphoid tissue type lymphoma

Objective To assess the value of CT or PET-CT with fluorine-18-labeled fluorodeoxyglucose (FDG) for the diagnosis of pulmonary mucosa-associated lymphoid tissue (MALT) type lymphoma. Methods The CT or FDG PET-CT findings in 14 patients with pathologically proved pulmonary MALT lymphoma were retrospectively analyzed. Results Lung lesions were unilateral in 7 patients and bilateral in 7 patients. Lesions presented as a single mass in 3 patients, as a single consolidation in 3 patients, as a nodule in 1 patient, as multiple nodules in 1 patient, as multiple patchy consolidations in 4 patients, as a mass with multiple nodules and patchy consolidations in 1 patients, as diffuse interstitial change in 1 patients. Air bronchogram was found in 9 patients and CT angiogram sign in 5 patients. On PET-CT, lesions showed heterogeneous FDG uptake in 2 patients, maximum standard uptake value was higher than 2. 5. Conclusion Imaging characteristics of pulmonary MALT lymphoma are single or multiple nodules or consolidations with air bronchogram on CT, and heterogeneous high FDG uptake on PET-CT. Key words: Lung neoplasms; Lymphoma; Tomography,X-ray computed; Tomography,emission-computed

Increased Radiotracer Uptake on Positron Emission Tomography After Invasive Thoracic Procedures: A Case Series

To investigate the hypothesis that tissue changes induced by invasive thoracic procedures may be associated with increased fluorine 18-labeled fluorodeoxyglucose (FDG) uptake on positron emission tomography (PET) scans, potentially leading to these tissue changes being mistaken for malignancies. We retrospectively reviewed the records of all patients undergoing bronchoscopies and FDG-PET at Mayo Clinic Jacksonville from February 2002 to September 2004 and identified patients who had undergone computed tomography (CT) of the chest and bronchoscopy before FDG-PET. We identified and reviewed the imaging studies of patients who had increased FDG uptake on PET scans and whose CT scans showed no corresponding abnormalities suggestive of malignancy. Eighty-one patients had undergone both bronchoscopy and PET within the defined study period. Of these, 45 (56%) underwent PET within 4 weeks after bronchoscopy, and 13 (29%) of these 45 patients had increased FDG uptake on PET scans that did not correlate with pathological findings on CT. We judged that increased uptake on 3 (23%) of the 13 PET scans was most likely related to the bronchoscopic procedure. Additionally, 2 patients who had undergone thoracoscopy after bronchoscopy but before PET had discordant CT and PET findings. Invasive thoracic procedures may cause an increased uptake of radiotracer on PET scans that could be mistakenly interpreted as evidence of malignancy. To avoid clinical misjudgment, clinicians should perform PET before invasive thoracic procedures.

Differential diagnosis of gallbladder cancer using positron emission tomography with fluorine-18-labeled fluoro-deoxyglucose (FDG-PET).

The purpose of this paper is to evaluate the utility of positron emission tomography (PET) with fluorine-18-labeled fluoro-deoxyglucose (FDG) in the preoperative differential diagnosis of gallbladder tumors. We performed PET studies of gallbladder tumors in order to predict the malignancy of these tumors preoperatively. Sixteen patients who had protuberant lesions in the gallbladder and who were scheduled to undergo surgery were studied with PET using FDG. Focally increased FDG uptake in the gallbladder region was considered malignant. The FDG-PET findings were compared with the histological findings of surgical pathology. Sensitivity of FDG-PET was 75% (6/8 patients). One of two false-negative cases suffered from diabetes mellitus, and in the other case, the lesion was small. Specificity was 87.5% (7/8 patients). A case with xanthogranulomatous cholecystitis (XGC) was the only false-positive case. FDG-PET may be able to provide important information for evaluating the malignancy of gallbladder tumors.

Efficacy and limitation of F-18-fluorodeoxyglucose positron emission tomography during fasting to assess myocardial viability in the acute phase of myocardial infarction.

The present study was designed to determine the ability of positron emission tomography (PET) to assess myocardial viability and ischemia in acute myocardial infarction (MI) after reperfusion therapy (thrombolysis and/or coronary angioplasty). PET with fluorine-18-labeled fluorodeoxyglucose (FDG) under fasting conditions and thallium-201 single-photon emission computed tomography (TL) were analyzed in 21 patients one week following MI. Myocardial viability was also assessed by regional wall motion using serial analysis of 2-D echocardiography or left ventriculography. Marked uptake of FDG together with a residual perfusion defect were observed in the infarct region in all patients one week post MI. However, in 9 of the 21 patients, the infarct-related coronary artery had no significant stenosis after reperfusion therapy and remained patent in one month post MI suggesting no myocardial ischemia. In contrast, in 4 of the 21 patients the regional wall motion was akinetic and there was a complete defect observed with TL imaging at one month post MI, indicating no viability in the infarct region. PET using fasting FDG at one week post MI had a limitation to predict myocardial viability or ischemia.

Fluorine 18-labeled fluorodeoxyglucose myocardial scintigraphy with Anger gamma cameras for assessing myocardial viability

A significant body of evidence now suggests that clinically adequate planar and SPECT myocardial perfusion/FDG metabolism studies can be performed for assessment of myocardial viability with conventional gamma cameras. This might reduce the need for more sophisticated PET scanners in this patient subgroup and also increase the general applicability of metabolic assessment of myocardial viability with FDG. The procedure is technically demanding in terms of both equipment and interpretation, and requires further careful evaluation before it can be recommended for widespread use. Nevertheless, it appears to have enough potential to warrant evaluation along with improving techniques of using myocardial perfusion tracers, PET imaging, and stress echocardiography to identify the most cost-effective options for assessing viability of myocardium in clinical situations in which this becomes important.

Evaluation of pancreatic tumors with positron emission tomography and F-18 fluorodeoxyglucose: comparison with CT and US.

To assess the clinical value of positron emission tomography (PET) with fluorine-18-labeled fluorodeoxyglucose (FDG) for identification of pancreatic carcinoma. Forty-six patients suspected of having a pancreatic neoplasm and who were to undergo surgery prospectively underwent FDG PET, computed tomography (CT), and transabdominal ultrasound (US). Endoscopic US was performed in 40 patients. Images were independently interpreted and compared with the histopathologic findings at surgery (41 patients) or with clinical follow-up findings (five patients). In 33 of 35 patients, foci of pancreatic carcinomas (10-100 mm in diameter) were identified as an increase in FDG uptake, whereas CT, transabdominal US, and endoscopic US depicted the foci in 31, 31, and 28, cases, respectively. Among 11 benign lesions, nine showed no increased FDG uptake (specificity = 82%). Specificities of the other modalities were lower. False-positive findings were obtained in a case of chronic active pancreatitis and in a serous cystadenoma. FDG PET, which provides "biochemical" information, is accurate in identifying pancreatic carcinoma and may be a method of choice when imaging equivocal masses detected with other "anatomic" imaging studies.

Optimal cutoff levels of F-18 fluorodeoxyglucose uptake in the differentiation of low-grade from high-grade brain tumors with PET.

To determine the optimal cutoff level of fluorine-18-labeled fluorodeoxyglucose (FDG) uptake in the differentiation of low-grade from high-grade cerebral tumors at position emission tomography (PET). The authors retrospectively reviewed images from PET, magnetic resonance imaging, and computed tomography performed in 58 consecutive patients with histologically proved brain tumors. There were 32 high-grade tumors (20 gliomas) and 26 low-grade tumors (18 gliomas). The best cutoff level of FDG uptake ratios in the differentiation of high-grade from low-grade tumors was 1.5 for tumor-to-white matter (T/WM) ratios and 0.6 for tumor-to-cortex (T/C) ratios. These levels were the same when only gliomas were analyzed and when all tumors were analyzed. When a T/WM ratio of more than 1.5 was considered indicative of a high-grade tumor, the sensitivity and specificity were 94% and 77%, respectively. The results were similar for the T/C ratio. Cutoff levels of 1.5 for the T/WM FDG uptake ratio and 0.6 for the T/C ratio are useful in the differentiation of low-grade from high-grade gliomas with PET.

F-18 fluorodeoxyglucose PET in vivo evaluation of pancreatic glucose metabolism for detection of pancreatic cancer.

To evaluate positron emission tomography (PET) with fluorine-18-labeled fluorodeoxyglucose (FDG) for detection of pancreatic cancer compared with computed tomography (CT) and ultrasonography (US). Forty patients with suspected pancreatic cancer underwent static PET after intravenous injection of 150-300 MBq FDG. Focal FDG accumulation was regarded as a sign of malignancy and was quantitated by calculating differential uptake ratios (DURs) and tumor-liver ratios (TLRs). Malignancy was histologically proved in 27 patients. PET helped correctly classify 25 of 27 malignant conditions and 11 of 13 benign disorders. DUR and TLR were statistically significantly higher in malignant compared with benign disease (P < .01). False-negative findings were obtained in patients with insulin-dependent diabetes. False-positive findings were noted in a patient with retroperitoneal fibrosis and in one with pancreas divisum with chronic pancreatitis. PET was superior to CT and US in detection of lymph node metastases (13 of 17 vs three of 17 or one of 15, respectively. FDG PET has the potential to improve the detection of lymphadenopathy and the differential diagnosis of pancreatic masses.

Methodology governing the assessment of myocardial glucose metabolism by positron emission tomography and fluorine 18-labeled fluorodeoxyglucose.

Positron emission tomography (PET) with fluorine 18-labeled fluorodeoxyglucose (FDG) has provided important insights into the alterations in myocardial glucose metabolism associated with normal cardiac physiology and pathophysiology. In patients with left ventricular dysfunction caused by coronary artery disease, PET-FDG studies have identified certain patterns of myocardial glucose metabolism relative to flow that are associated with viable myocardium. Consequently, in many centers, PET-FDG imaging is being used to identify patients with left ventricular dysfunction who are likely to benefit from coronary revascularization. However, myocardial glucose metabolism (and thus myocardial uptake of FDG) is markedly dependent on a variety of factors, particularly the substrate environment and level of myocardial perfusion. These and other factors must be considered to obtain and interpret myocardial FDG images accurately with respect to the underlying pathophysiologic process. In this review the impact of these factors on myocardial FDG imaging, as well as the relative advantages and disadvantages of approaches designed to optimize myocardial PET-FDG studies, will be discussed.

Current status of viability assessment with positron tomography.

Accurate detection of reversible myocardium has great clinical importance, especially in patients being considered for interventional therapy. Positron emission tomography (PET) with fluorine 18-labeled fluorodeoxyglucose (FDG) has been used for this purpose, based on the residual metabolic activity in reversible ischemic areas. Although thallium imaging has been widely used for the evaluation of tissue viability in clinical cardiology, PET-FDG may provide independent values and thus may enhance the accuracy of studies for identifying ischemic myocardium. This review considers the advantages of PET technique, the clinical value of PET-FDG for assessing tissue viability, and the development of other new PET techniques.

Identification of viable myocardium in patients with chronic coronary artery disease and left ventricular dysfunction. Comparison of thallium scintigraphy with reinjection and PET imaging with 18F-fluorodeoxyglucose.

In patients with chronic coronary artery disease and left ventricular dysfunction, the distinction between ventricular dysfunction arising from myocardial fibrosis and ischemic, but viable, myocardium has important clinical implications. By positron emission tomography (PET), enhanced fluorine-18-labeled fluorodeoxyglucose (FDG) uptake in myocardial segments with impaired function and reduced blood flow is evidence of myocardial viability. Reinjection of thallium-201 at rest immediately after stress-redistribution imaging may also provide evidence of myocardial viability by demonstrating thallium uptake in regions with apparently "irreversible" defects. To compare these two methods, we studied 16 patients with chronic coronary artery disease and left ventricular dysfunction (ejection fraction, 27 +/- 9%), all of whom had irreversible defects on standard exercise-redistribution thallium single-photon emission computed tomography (SPECT) imaging. Thallium was reinjected immediately after the redistribution study, and SPECT images were reacquired. The patients also underwent PET imaging with FDG and oxygen-15-labeled water. A total of 432 myocardial segments were analyzed from comparable transaxial tomograms, of which 166 (38%) had irreversible thallium defects on redistribution images before reinjection. FDG uptake was demonstrated in 121 (73%) of these irreversible defects. Irreversible defects were then subgrouped according to the degree of thallium activity, relative to peak activity in normal regions. Irreversible defects with only mild (60-85% of peak activity) or moderate (50-59% of peak) reduction in thallium activity were considered viable on the basis of FDG uptake in 91% and 84% of these segments, respectively. In contrast, in irreversible defects with severe reduction in thallium activity (less than 50% of peak), FDG uptake was present in 51% of segments. In such severe defects, an identical number of segments (51%) demonstrated enhanced uptake of thallium after reinjection. In these severe "irreversible" defects, data on myocardial viability were concordant by the two techniques in 88% of segments, with 45% identified as viable and 43% identified as scar on both PET and thallium reinjection studies. These observations suggest that thallium imaging can be used to identify viable myocardium in patients with chronic coronary artery disease and left ventricular dysfunction. Most irreversible defects with only mild or moderate reduction in thallium activity represent viable myocardium as confirmed by FDG uptake.(ABSTRACT TRUNCATED AT 400 WORDS)

Regional myocardial glucose metabolism in angina pectoris obtained from positron emission tomography.

This article presents a review of studies carried out with positron tomography on myocardial blood flow and glucose metabolism in patients with coronary artery disease and either stable (SA) or unstable angina (UA) pectoris. Regional blood flow was assessed with rubidium 82, an analogue of potassium, and glucose metabolism both with fluorine 18-labeled fluorodeoxyglucose (FDG) and carbon 11-labeled glucose (CG). There were no clear differences in regional myocardial blood flow between SA and UA patients and a group of normal volunteers. FDG uptake was low and homogeneous in both SA patients and normals. In contrast, all UA patients showed abnormally high FDG uptake in at least one left ventricular region at rest in the absence of symptoms or signs of acute ischemia. In the recovery from a period of exercise-induced angina, FDG uptake in SA patients was observed to be higher in previously ischemic regions than in nonischemic regions (as defined by 82Rb). It is postulated that higher FDG uptake in the postischemic myocardium of SA patients is due to repletion of glycogen stores. It remains unclear whether the high uptake in UA patients is due to a recent ischemic episode or is a reflection of a chronic adaptation to repeated stress.