The use of 2-[18F]fluoro-2-deoxy-D-glucose as a potential in vitro agent for labelling human granulocytes for clinical studies by positron emission tomography

Feasibility of 18F-FDG Labelling of Leucocytes in a Centre Without an On-Site Cyclotron and Monitoring of Radiation Dose to Occupational Worker in the Labelling Procedure

Objectives: Differentiation of infection from sterile inflammation is still a major concern for clinicians. The ¹⁸F-WBC positron emission tomography/computed tomography scan has been considered a promising tool for accurate diagnosis of infection owing to its high specificity, but it renders the availability of a medical cyclotron a necessity. The aim of the present study was to determine the feasibility of labeling leukocytes and establish the protocol in a center without the availability of an on-site medical cyclotron. The secondary aim was to monitor radiation doses to occupational workers involved in labeling of leukocytes with ¹⁸F-FDG. Materials and Methods: Leukocyte separation was performed and leukocytes were radiolabeled with ¹⁸F-FDG in a sterile environment according to the procedure described by Bhattacharya et al. In vitro leukocyte viability was assessed using the trypan dye exclusion technique. Labeling efficiency and yield were also estimated for all radiolabeling procedures. Whole-body and extremity doses received by the personnel involved in the radiolabeling procedure were also estimated using pocket dosimeters. Results: Leukocyte labeling was carried out in 35 runs, during which there were two failed labeling attempts due to clotting of the blood sample. The total time involved in the whole procedure was around 2.5 h. The average labeling efficiency was 78.01% ± 6.99% (range 63.46%-86.54%), cell viability was 98%, and the cell suspension was stable up to 4 h. The mean dose was measured as 17 μSv at the chest level and 32 μSv at the extremity level, per procedure. Conclusions: Labeling of leukocytes with ¹⁸F-FDG is possible at a tertiary nuclear medicine setup without the availability of an on-site medical cyclotron, with reasonable labeling efficiency of 78.01% ± 6.99%. In addition, in-house labeling of leukocytes with ¹⁸F-FDG is safe and the radiation doses incurred by the personnel during the labeling procedure are well within the occupational dose limits established by the national regulatory authority.

Incremental Value of 18 F-FDG-Labeled Leukocytes PET/CT Over 18 F-FDG PET/CT Scan in the Detection of Occult Infection

PURPOSE

Differentiating infection and sterile inflammation is the main clinical concern of clinicians as they are closely related to each other. Although 18 F-FDG PET/CT imaging is widely used, its main disadvantage is its lack of specificity to discriminate aseptic from septic inflammation. 18 F-WBC PET/CT scan is a promising tool for the accurate diagnosis of infection owing to its high specificity. The aim of the present study is to determine the utility of 18 F-WBC PET/CT in the diagnosis of occult infections and to assess its incremental value over routine 18 F-FDG PET/CT scan.

PATIENTS AND METHODS

This prospective observational diagnostic accuracy study included 33 patients with fever of unknown origin or suspected periprosthetic infection and raised C-reactive protein and total leukocyte count. All the patients underwent both 18 F-WBC PET/CT scan and 18 F-FDG PET/CT scan using a standard protocol on 2 different days. Images of both the scans were evaluated by both visual analyses based on uptake intensity and quantitative grading based on lesion-to-background SUV max values. For interpretation of FDG PET/CT images, visual scoring of grade 0 (undetectable or no uptake), grade 1a (less than liver uptake), grade 1b (equivalent to liver uptake), grade 2 (higher than liver uptake), and grade 3 (higher than cerebellum uptake) was used. 18 F-WBC PET/CT images were also interpreted visually as grade 0 (undetectable or no uptake), grade 1a (significantly less than lumbar vertebrae or liver uptake for truncal lesions, and in case of extremity lesion slightly higher than neighboring soft tissue uptake or less than neighboring bone marrow uptake), grade 1b (equivalent to liver or lumbar vertebrae uptake for truncal lesions, and in case of extremity lesion significantly higher than neighboring soft tissue uptake or higher than neighboring bone marrow uptake), grade 2 (higher than liver or bone marrow uptake), and grade 3 (higher than twice the liver or bone marrow uptake). Similarly, a quantitative grading was also done based on lesion-to-background SUV max using a circular region of interest manually drawn. For both 18 F-FDG and 18 F-WBC PET/CT, the lesion-to-background ratio of <1.5 was recorded as grade 0, 1.5-2.5 as grade 1a, 2.5-3.5 as grade 1b, 3.5-4.5 as grade 2, and >4.5 as grade 3. Final diagnosis was made by histopathological, microbiological analysis, or clinical-radiological workup.

RESULTS

Twenty-nine foci of suspected infection were found in 25/33 patients by either 18 F-FDG PET/CT or 18 F-WBC PET/CT scan. No abnormal uptake of either 18 F-FDG or 18 F-FDG WBC scan was seen in 8 patients. There was a concordance of 18 F-FDG PET/CT and 18 F-WBC PET/CT in 28 sites each using grade 1b of visual and quantitative analysis, respectively. Of the 29 suspicious infected foci, 18 were proven positive for infection (14/18 sites by the histopathological/microbiological culture and the rest 4/18 sites by clinical/radiological workup). Culture of aspirates or biopsy from 11/29 suspicious sites was proven noninfective. Seven of 11 suspicious sites were proven noninfective by clinical/radiological workup. The mean clinical follow-up was 8 months (1-15 months).Overall significantly higher diagnostic accuracy was demonstrated with 18 F-WBC PET/CT in comparison to 18 F-FDG PET/CT for the detection of infection ( P < 0.05). The highest diagnostic accuracy of 18 F-WBC PET/CT scan was reported with both grade 1b of visual as well as of quantitative analysis (lesion-to-background SUV max , 2.5-3.5) and grade 2 for both visual and quantitative analysis for 18 F FDG PET/CT.

CONCLUSIONS

18 F-WBC PET/CT has a higher diagnostic accuracy over 18 F-FDG PET/CT for the diagnosis of occult infection.

Relationship Between 18F-fluorodeoxyglucose Uptake on Positron Emission Tomography and Aortic Calcification

Introduction: Although ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET) has been widely utilized to assess the extent of inflammation, the association between the extent and severity of atherosclerosis and ¹⁸F-FDG uptake on PET remains unexamined. The current study aimed to investigate whether aortic calcium (AC) scores were associated with increased aortic uptake of ¹⁸F-FDG on PET. Methods: A total of 167 consecutive patients with suspected lung cancer but unproven malignancy who underwent non-contrast-enhanced computed tomography (CT) and ¹⁸F-FDG PET/CT were enrolled. The average standardized uptake values in the ascending aorta were used to calculate the target-to-background ratio (Mean TBR). The total (thoracic and abdominal) AC scores were measured on non-contrast-enhanced chest and abdominal CT using the Agatston method, and were categorized into three groups (0, 1-399, and ≥400). The relationship between total AC scores and ¹⁸F-FDG uptake in the ascending aorta was assessed using multivariate linear regression analysis. Results: In total, 68.26% were male, and a mean age was 67.10±14.70 years. Mean TBR values increased progressively with total AC score 0, 1-399, and ≥400 (1.01±0.07, 1.08±0.09, and 1.11±0.11, respectively; p<0.00001). Multivariate linear regression analysis revealed that increased total AC scores of 1-399 (β=0.06, 95% CI: 0.01-0.11, p=0.02) and ≥400 (β=0.11, 95% CI: 0.06-0.16, p<0.001) were significantly associated with higher Mean TBR. Conclusions: The current study demonstrated that total AC scores were associated with Mean TBR. Patients with a greater extent and severity of aortic calcifications may possess increased atherosclerotic inflammatory activity as measured by ¹⁸F-FDG PET/CT.

Direct Cell Radiolabeling for in Vivo Cell Tracking with PET and SPECT Imaging

The arrival of cell-based therapies is a revolution in medicine. However, its safe clinical application in a rational manner depends on reliable, clinically applicable methods for determining the fate and trafficking of therapeutic cells in vivo using medical imaging techniques─known as in vivo cell tracking. Radionuclide imaging using single photon emission computed tomography (SPECT) or positron emission tomography (PET) has several advantages over other imaging modalities for cell tracking because of its high sensitivity (requiring low amounts of probe per cell for imaging) and whole-body quantitative imaging capability using clinically available scanners. For cell tracking with radionuclides, ex vivo direct cell radiolabeling, that is, radiolabeling cells before their administration, is the simplest and most robust method, allowing labeling of any cell type without the need for genetic modification. This Review covers the development and application of direct cell radiolabeling probes utilizing a variety of chemical approaches: organic and inorganic/coordination (radio)chemistry, nanomaterials, and biochemistry. We describe the key early developments and the most recent advances in the field, identifying advantages and disadvantages of the different approaches and informing future development and choice of methods for clinical and preclinical application.

99mTc-HMPAO-WBC SPECT/CT versus 18F-FDG-WBC PET/CT in chronic prosthetic joint infection: a pilot study

PURPOSE

The aim of this study was to compare 99mTc-HMPAO-WBC-SPECT/CT combined with 99mTc-nanocollloid SPECT/CT and 18F-FDG-WBC-PET/CT combined with 99mTc-Nanocollloid SPECT/CT for the diagnosis and treatment evaluation of chronic prosthetic joint infection (PJI).

METHODS

Patients with suspected chronic PJI were examined with 99mTc-HMPAO-WBC SPECT/CT, 18F-FDG-WBC PET/CT, and 99mTc-nanocolloid SPECT/CT (to visualize bone marrow). The location and patterns of uptake were noted and compared between the two leukocyte examinations. Both leukocyte examinations were evaluated visually for infection. The PET examinations were also evaluated semiquantitatively. Chronic PJI was verified clinically by microbial culture and successfully treated PJI was confirmed by 12 months symptom-free follow-up after cessation of antibiotics.

RESULTS

Nineteen patients were included with 10 hip prostheses and nine knee prostheses. Fourteen were diagnosed with chronic PJI and five with successfully treated PJI. The sensitivity of visual evaluation of 99mTc-WBC-HMPAO SPECT/CT for all joints was 0.31 and for 18F-FDG-WBC PET/CT 0.38. The specificity was 0.80 and 0.83, respectively. All patients with a true-positive SPECT examination had a false-negative PET examination and vice versa. Semiquantitative evaluation of the hips gave an area under the curve of 0.905 using the iliac crest as the background. Semiquantitative evaluation of the knees did not produce significant results.

CONCLUSION

This pilot study showed no difference in the sensitivity or specificity of 99mTc-HMPAO-WBC SPECT/CT and 18F-FDG-WBC PET/CT when combined with 99mTc-nanocollloid SPECT/CT in the diagnosis or treatment evaluation of suspected late chronic PJI.

Invasive Fungal Infection in COVID-19-Recovered Patient Detected on 18F-FDG-Labeled Leukocytes PET/CT Scan

ABSTRACT

Occurrence of invasive fungal infections has gained significant attention during recent times in patients with COVID-19. Patients with severe form of COVID-19, such as those treated in the intensive care unit with prolonged steroid use, are particularly vulnerable to secondary bacterial and fungal infections. Disseminated systemic mycosis is a life-threatening condition, especially in immunocompromised patients. Here, we report a case of a recovered severe COVID-19 patient, who presented with persistent fever. 18F-FDG-labeled leukocyte scan revealed focal accumulation of radiotracer in the small intestine and right lung lower lobe. Subsequently, performed biopsy revealed mucormycosis.

Infection imaging using [18F]FDG-labelled white blood cell positron emission tomography-computed tomography

Localizing the sites of infection in the body is possible in nuclear medicine using a variety of radiopharmaceuticals that target different components of the infective and inflammatory cascade. Gamma(γ)-emitting agents such as [67Ga]gallium citrate were among the first tracers used, followed by development of positron-emitting tracers like 2-deoxy-2-[18F]fluoro-D-glucose (¹⁸F-FDG). Though these tracers are quite sensitive, they have limited specificity for infection due to their concentration in sites of non-infective inflammation. White blood cells (WBC) labelled with γ or positron emitters have higher accuracy for differentiating the infective processes from the non-infective conditions that may show positivity with tracers such as ¹⁸F-FDG. We present a pictorial review of potential clinical applications of PET/CT using ¹⁸F-FDG labelled WBC.

Achievement in active agent structures as a power tools in tumor angiogenesis imaging

According to World Health Organization (WHO) cancer is the second most important cause of death globally. Because angiogenesis is considered as an essential process of growth, proliferation and tumor progression, within this review we decided to shade light on recent development of chemical compounds which play a significant role in its imaging and monitoring. Indeed, the review gives insight about the current achievements of active agents structures involved in imaging techniques such as: positron emission computed tomography (PET), magnetic resonance imaging (MRI) and single photon emission computed tomography (SPECT), as well as combination PET/MRI and PET/CT. The review aims to provide the journal audience with a comprehensive and in-deep understanding of chemistry policy in tumor angiogenesis imaging.

Rodent Leukocyte Isolation and Radiolabeling for Inflammation Imaging Study

Purpose

The objective of this study was to describe to develop methods of rodent leukocyte isolation and radiolabeling for in vivo inflammation imaging.

Methods

Thigh muscle inflammation was induced by injection of collagenase. Blood was collected from the jugular vein and separated by Histopaque. The collected cells were incubated in a 37 °C CO₂ incubator for 1~2 h. After incubation, ^99mTc-HMPAO and ¹⁸F-FDG were used to treat leukocytes followed by incubation for 30 min. ^99mTc-HMPAO and ¹⁸F-FDG labeled autologous leukocytes were injected into the tail veins of rats. The images were then acquired at various time points. Image-based lesion to normal muscle ratio was compared.

Results

After Histopaque separation, the proportion of lymphocytes was higher than that of other cell types. After CO₂ incubation, the collected leukocytes were viable, while room temperature exposed leukocytes without CO₂ incubation were non-viable. Granulocytes, especially, were more quickly influenced by various conditions than the mononuclear cells. Labeling efficiencies of ^99mTc-HMPAO and ¹⁸F-FDG were 4.00 ± 2.06 and 1.8%, respectively. ^99mTc-HMPAO- and ¹⁸F-FDG-labeled leukocytes targeted well the inflamed lesion. ^99mTc-HMPAO-labeled leukocytes, but not ¹⁸F-FDG-labeled leukocytes, were found in the abdomen activity.

Conclusion

Inflamed lesions of rats were well visualized using autologous radiolabeled leukocytes. This method might provide good information for understanding inflammatory diseases.

Diagnostic Performance of PET or PET/CT Using 18F-FDG Labeled White Blood Cells in Infectious Diseases: A Systematic Review and a Bivariate Meta-Analysis

BACKGROUND

Diagnostic performance of positron emission tomography using white blood cells labeled with fluorine-18-fluorodeoxyglucose (¹⁸F-FDG-WBC PET or PET/CT) in patients with suspicious infectious diseases has been evaluated in several studies; however, there is no consensus about the diagnostic accuracy of this method. Therefore, a systematic review and meta-analysis was carried out on this topic.

METHODS

A comprehensive computer literature search screening PubMed/MEDLINE, Embase and Cochrane library databases through March 2019 was performed. Pooled sensitivity, specificity, positive and negative likelihood ratios (LR+ and LR-), and diagnostic odds ratio (DOR) of ¹⁸F-FDG-WBC PET or PET/CT in patients with infectious diseases were calculated.

RESULTS

Eight studies on the use of ¹⁸F-FDG-WBC PET or PET/CT in suspicious infectious diseases were discussed in the systematic review. The meta-analysis of seven studies (236 patients) provided these pooled results on a per patient-based analysis: sensitivity was 86.3% [95% confidence interval (95%CI) 75-92.9%], specificity 92% (95%CI 79.8-97.1%), LR+ 6.6 (95%CI: 3.1-14.1), LR- 0.2 (95%CI: 0.12-0.33), DOR 43.5 (95%CI: 12.2-155). A statistically significant heterogeneity was not detected.

CONCLUSIONS

Despite limited literature data, ¹⁸F-FDG-WBC PET or PET/CT demonstrated a good diagnostic accuracy for the diagnosis of infectious diseases; nevertheless, larger studies are needed.

Clinical experience with white blood cell-PET/CT in autosomal dominant polycystic kidney disease patients with suspected cyst infection: A prospective case series

AIMS

Cyst infection (CI) is a common problem in patients with autosomal dominant polycystic kidney disease (ADPKD). Localization is of great importance in CI. We describe the clinical experience with [18F] FDG-labelled white-blood cell (WBC) PET/CT in detecting CI in ADPKD.

METHODS

Nineteen ADPKD patients (M:F = 7:12) suspected of having CI were enrolled in this prospective study. All underwent WBC-PET/CT and MRI or CT. The degree of their WBC accumulation was evaluated from the maximal standardized uptake value of cystic wall.

RESULTS

Cyst infection was diagnosed in 14 cases [definite (n = 6), probable (n = 1), or possible (n = 7); kidney (n = 11), or liver (n = 3)]. There was no difference in fever or laboratory findings (White blood cell count, C-reactive protein, culture results, and eGFR). The blood culture was positive only in a subset of CI patients (n = 4). Cyst fluid culture yielded bacterial growth in 80% of aspirates. WBC-PET/CT detected 64% of CI cases, whereas conventional imaging, 50%. WBC-PET/CT showed false-positive results in two of five cases with no CI. The reasons for false negatives with WBC-PET/CT were poor host immune reaction, low virulence, or prior antibiotic therapy. Haemorrhagic cysts were the most common cause of false positivity in WBC-PET/CT. However, WBC-PET/CT detected CI in three cases, in which the conventional imaging failed to find CI.

CONCLUSIONS

Clinical information may play little role in the diagnosis of CI. WBC-PET/CT can be used to detect CI with better sensitivity in ADPKD patients, circumventing the exposure to contrast media.

18F-FDG-labeled red blood cell PET for blood-pool imaging: preclinical evaluation in rats

Background

Red blood cells (RBCs) labeled with single-photon emitters have been clinically used for blood-pool imaging. Although some PET tracers have been introduced for blood-pool imaging, they have not yet been widely used. The present study investigated the feasibility of labeling RBCs with ¹⁸F-2-deoxy-2-fluoro-D-glucose (¹⁸F-FDG) for blood-pool imaging with PET.

RBCs isolated from venous blood of rats were washed with glucose-free phosphate-buffered saline and labeled with ¹⁸F-FDG. To optimize labeling efficiency, the effects of glucose deprivation time and incubation (labeling) time with ¹⁸F-FDG were investigated. Post-labeling stability was assessed by calculating the release fraction of radioactivity and identifying the chemical forms of ¹⁸F in the released and intracellular components of ¹⁸F-FDG-labeled RBCs incubated in plasma. Just after intravenous injection of the optimized autologous ¹⁸F-FDG-labeled RBCs, dynamic PET scans were performed to evaluate in vivo imaging in normal rats and intraabdominal bleeding models (temporary and persistent bleeding).

Results

The optimal durations of glucose deprivation and incubation (labeling) with ¹⁸F-FDG were 60 and 30 min, respectively. As low as 10% of ¹⁸F was released as the form of ¹⁸F-FDG from ¹⁸F-FDG-labeled RBCs after a 60-min incubation. Dynamic PET images of normal rats showed strong persistence in the cardiovascular system for at least 120 min. In the intraabdominal bleeding models, ¹⁸F-FDG-labeled RBC PET visualized the extravascular blood clearly and revealed the dynamic changes of the extravascular radioactivity in the temporary and persistent bleeding.

Conclusions

RBCs can be effectively labeled with ¹⁸F-FDG and used for blood-pool imaging with PET in rats.

Electronic supplementary material

The online version of this article (doi:10.1186/s13550-017-0266-3) contains supplementary material, which is available to authorized users.

Positron Emission Tomography and Autoradiography of (18)F-Fluorodeoxyglucose Labeled Islets With or Without Warm Ischemic Stress in Portal Transplanted Rats

OBJECTIVE

The use of positron-emission tomography (PET) with (18)F-fluorodeoxyglucose (FDG) -labeled islets has been considered to be a potential modality to visualize and quantify early engraftment of islet transplantation. The objective of this study was to evaluate the early islets' survival of the FDG-labeled islets with or without warm ischemic stress in portal transplanted rats using PET and autoradiography.

METHODS

Islets were isolated from Lewis rat pancreata with or without 30-minute warm ischemia times (WITs). For islets' labeling, 300 islets were incubated with 3 MBq FDG for 60 minutes. FDG-labeled islets were transplanted into the liver via portal vein. In in vivo study, a PET study was scanned for 90 minutes and the FDG uptake was expressed as percentage of liver injection dose (ID). In ex vivo study, the liver was exposed for 30 minutes with single fluorescence autoradiography.

RESULTS

In the PET study, the percentage of liver ID of the islets without WIT was 27.8 and that of the WIT islets was 20.1 at the end of islet transplantation. At 90 minutes after transplantation, the percentage of liver ID was decreased to 14.7 in the islets without WIT and 10.1 in the WIT islets. In the autoradiogram, the number of hot spots was more obviously visualized in the liver transplanted without WIT islets than in the liver transplanted with WIT islets.

CONCLUSION

Almost 50% of the islets were immediately lost in both the islets without WIT and those with WIT transplantation in the early period. However, islet survival was 1.4 times higher in the islets without WIT than that in those with WIT in the early engraftment phase.

Increased choline uptake in macrophages and prostate cancer cells does not allow for differentiation between benign and malignant prostate pathologies

INTRODUCTION

Inflammatory cells may contribute to the choline uptake in different prostate pathologies. The aim of this study was (i) to assess if inflammatory cells incorporate choline and (ii) to potentially detect differences compared to FDG uptake. Therefore we investigated the uptake of [(3)H]choline and [(18)F]FDG in human prostate carcinoma cells and human inflammatory cells.

METHODS

Macrophages were cultured from isolated mononuclear cells, gained by density gradient centrifugation of human buffy coats. T-lymphocytes, B-lymphocytes and granulocytes were enriched by density gradient centrifugation before cell sorting by means of flow cytometry was performed. [(3)H]choline and [(18)F]FDG uptake of isolated inflammatory cells as well as of LNCaP and PC-3 human prostate carcinoma cells was assessed simultaneously in dual tracer uptake experiments.

RESULTS

Macrophages showed highest [(3)H]choline and [(18)F]FDG uptake compared to the tracer uptake rates of leukocytes. [(3)H]choline uptake of macrophages was in the same range as in prostate cancer cells. Lipopolysaccharide stimulation of macrophages resulted in an increase of [(18)F]FDG uptake in macrophages, but not in an increased [(3)H]choline uptake.

CONCLUSIONS

The high [(3)H]choline uptake in macrophages may be a source of false-positive PET results in diagnosis of prostate cancer by choline-PET/CT. As already known from FDG-PET, discrimination between tumor and inflammation in prostate cancer patients is not possible via choline-PET.

ADVANCES IN KNOWLEDGE AND IMPLICATIONS FOR PATIENT CARE

The application of choline-PET for reliable primary prostate cancer detection and delineation has to be queried.

A longitudinal study of FDG-PET in Crohn disease patients receiving granulocyte/monocyte apheresis therapy

BACKGROUND AIMS

Endoscopy is the gold standard for the diagnosis and follow-up of patients with Crohn disease (CD). However, a less invasive approach is now being sought for the management of these patients. The objective of this study was to examine whether (18)F-fluorodeoxyglucose (FDG)-positron emission tomography (PET) might be relevant for monitoring the disease activity in CD patients undergoing granulocyte/monocyte apheresis (GMA).

METHODS

This study was conducted in 12 patients with CD who were receiving treatment with 10 once-a-week GMA sessions with the Adacolumn. The response to treatment was monitored by measuring standard laboratory variables, Crohn's Disease Activity Index (CDAI) score, International Organization for the Study of Inflammatory Bowel Diseases (IOIBD) score, and regional and global bowel uptakes on FDG-PET.

RESULTS

In 6 of the 12 patients, significant improvement of the CDAI was observed after the final session of GMA. The patients who showed clinical response to GMA had a decrease in the regional and global bowel uptakes on FDG-PET, whereas those who did not respond showed no change. In the patients who responded to the GMA, the decrease in regional bowel uptake on FDG-PET in each disease area of the same patient varied in parallel. There was a significant correlation between decrease in the global bowel uptake on FDG-PET and improvement of the CDAI and IOIBD scores.

CONCLUSIONS

The longitudinal changes in FDG-PET uptakes are of potential clinical interest for assessing the regional and global bowel disease activity in CD patients undergoing GMA therapy.

Comparison of FDG and FDG-labeled leukocytes PET/CT in diagnosis of infection

The aim of this study is to compare FDG and FDG-labeled leukocyte (WBC) PET/CT in the diagnosis of infection using different SUV and visual thresholds for interpretation. Patients, material, method: 49 consecutive patients (27 men, 22 women, mean age: 55.7 years, range: 16-89 years) with suspected musculoskeletal infection (n = 34), vascular graft infection (n = 5), aortitis (n =1 ), endocarditis (n = 1), mass lesion which is suspicious for infection or malignity (n = 6), and fever of unknown origin (n = 2) underwent both FDG and WBC-PET/CT. Images were evaluated by both visual analysis (grade 1-3) according to uptake intensity and quantitative grading (grade 1-3) based on lesion to background SUVmax values. Final diagnosis was made by histopathological, microbiological analysis or clinical-radiological work-up.

RESULTS

The diagnosis of infection was made in total 24 patients, of whom 14 were diagnosed by histopathological and the rest by clinical-radiological work-up. WBC-PET/CT imaging with the visual threshold of 1b as infection positivity (for truncal lesions uptake equivalent to liver or lumbar vertebrae uptake; for extremity lesions uptake significantly higher than neighbouring soft tissue uptake or higher than neighbouring bone marrow uptake) was found to have the highest diagnostic accuracy (AUC: 0.874, CI: 0.771-0.997, p < 0.001). The optimal SUV threshold was found to be 8.8 (p = 0.006; sensitivity: 72.7%, specificity: 82.8) and 5.3 (p < 0.001; sensitivity: 81.8%, specificity: 79.3%) for FDG and WBC-PET/CT, respectively by ROC curve analysis.

CONCLUSION

WBC-PET/CT is more valuable than FDG PET/CT in the imaging of infection. Visual threshold of >1b seems to be more suitable for detection of infection.

Development of a specific tracer for metabolic imaging of alveolar echinococcosis: A preclinical study

Positron emission tomography (PET)-computed tomography (CT) using [18F]-fluorodeoxyglucose (FDG) (FDG-PET/CT) is a valuable method for initial staging and follow up of patients with alveolar echinococcosis (AE). However, the cells responsible for FDG uptake have not been clearly identified. The main goal of our study was to evaluate the uptake of PET tracers by the cells involved in the host-parasite reaction around AE lesions as the first step to develop a specific PET tracer that would allow direct assessment of parasite viability in AE. Candidate molecules ([18F]-fluorotyrosine (FET), [18F]-fluorothymidine (FLT), and [18F]-fluorometylcholine (FMC), were compared to FDG by in vitro studies on human leukocytes and parasite vesicles. Our results confirmed that FDG was mainly consumed by immune cells and showed that FLT was the best candidate tracer for parasite metabolism. Indeed, parasite cells exhibited high uptake of FLT. We also performed PET/CT scans in mice infected intraperitoneally with E. multilocularis metacestodes. PET images showed no FDG or FLT uptake in parasitic lesions. This preliminary study assessed the metabolic activity of human leukocytes and AE cells using radiolabeling. Future studies could develop a specific PET tracer for AE lesions to improve lesion detection and echinococcosis treatment in patients. Our results demonstrated that a new animal model is needed for preclinical PET imaging to better mimic human hepatic and/or periparasitic metabolism.

Quantification of the chromosomal radiation damage induced by labelling of leukocytes with [18F]FDG

INTRODUCTION

The aim of our work is to quantify the radiation damage in lymphocytes after labelling with [18F]FDG. Comparison with gold standard [99mTc]HMPAO labelling is established. An approach to cellular dosimetry is proposed.

METHODS

Mixed leukocytes were separated from fresh venous blood and labelled with [18F]FDG and [99mTc]HMPAO following published guidelines. Cytokinesis-block micronucleus (CBMN) assay was performed for both sets of experiments. Tests for quality control of labelling described in guidelines were followed. Cellular dosimetry was calculated according to MIRD.

RESULTS

MN scored after labelling with 37 MBq of [18F]FDG were 956 ± 172 and 347 ± 26 for [99mTc]HMPAO (p < 0.05). Absorbed dose in cell nucleus was of 0.23 Gy for [18F]FDG and 0.08 Gy for [99mTc]HMPAO labelling. The CBMN assay after labelling with ~290 MBq of [18F]FDG showed radiation induced inhibition of proliferation capacity of the lymphocytes, confirmed by proliferation study.

CONCLUSIONS

[18F]FDG labelling of mixed leukocytes causes severe radiation damage to the cell, higher than with [99mTc]HMPAO in accordance with the absorbed dose. Labelling of mixed leukocytes for clinical purpose induces high cytotoxicity reflected in the loss of proliferation capacity in lymphocytes this statement allows us to consider a low oncogenic risk however the association between MN formation in the PBL and subsequent risk of cancer is not well established.

ADVANCES IN KNOWLEDGE

This is the first work about radiation damage with [18F]FDG labelled cells. We focused on [18F]FDG labelling of leukocytes due to the growing number of research and review articles about this technique.

IMPLICATIONS FOR PATIENT CARE

The possibility of an increased risk of lymphoid malignancies associated with the administration of radiolabelled lymphocytes is a very controversial subject. Studies on radiation damage on new labelling procedures as the one exposed in this work must be considered.

Growing applications of FDG PET-CT imaging in non-oncologic conditions

As the number of clinical applications of 2-[fluorine 18]fluoro-2-deoxy-D-glucose (FDG) positron emission tomography/computed tomography (PET-CT) grows, familiarity with the conditions that can be diagnosed by this modality and when relevant pieces of additional information can be obtained becomes increasingly important for both requesting physicians and nuclear medicine physicians or radiologists who interpret the findings. Apart from its heavy use in clinical oncology, FDG PET-CT is widely used in a variety of non-oncologic conditions interconnecting to such disciplines as general internal medicine, infectious diseases, cardiology, neurology, surgery, traumatology, orthopedics, pediatrics, endocrinology, rheumatology, psychiatry, neuropsychology, and cognitive neuroscience. The aim of this review was to summarize the current evidence of FDG PET-CT applications in evaluating non-oncologic pathologies and the relevant information it can add to achieve a final diagnosis.

PET/CT with 18F-FDG-labeled autologous leukocytes for the diagnosis of infected fluid collections in acute pancreatitis

Early detection of infection in acute pancreatitis (AP) affects the choice of treatment and clinical outcome. We used PET/CT with (18)F-FDG-labeled autologous leukocytes to detect infection in pancreatic or peripancreatic fluid collections in patients with AP.

METHODS

Forty-one patients (28 men and 13 women) who were 21-69 y old (mean ± SD, 41 ± 11.5) and had AP and radiologic evidence of a fluid collection in or around the pancreas were studied. Leukocytes were separated from the patient's venous blood, labeled with (18)F-FDG, and reinjected intravenously; PET/CT images were acquired 2 h later. A final diagnosis of infection was based on microbiologic culture of fluid aspirated from the collection. Patients were treated with supportive care and antibiotics; percutaneous drainage or laparotomy was performed when indicated.

RESULTS

Blood glucose level, total leukocyte count, neutrophil count, and leukocyte labeling efficiency varied from 83 to 212 mg/100 mL (118 ± 30), 4,600 to 24,200/mm(3) (11,648 ± 5,376), 55% to 90% (73 ± 10), and 31% to 97% (81 ± 17), respectively. Increased tracer uptake in the fluid collection was seen in 12 of 41 patients; 10 had culture-proven infection and underwent percutaneous drainage, and aspiration was unsuccessful in 2. The scan results were negative for infection in 29 patients; 25 had fluid culture results that were negative for infection, and aspiration was unsuccessful in 4. The sensitivity, specificity, and accuracy of the scan were all 100% in 35 patients for whom fluid culture reports were available.

CONCLUSION

PET/CT with (18)F-FDG-labeled leukocytes is a noninvasive and reliable method for the diagnosis of infection in pancreatic or peripancreatic fluid collections in patients with AP.

FDG and FDG-labelled leucocyte PET/CT in the imaging of prosthetic joint infection

PURPOSE

The demand for arthroplasty is rapidly growing as a result of the ageing of the population. Although complications such as heterotrophic ossification, fracture and dislocation are relatively rare, differentiating aseptic loosening, the most common complication of arthroplasty from infection, is a major challenge for clinicians. Radionuclide imaging is currently the imaging modality of choice since it is not affected by orthopaedic hardware. Whereas FDG PET/CT imaging has been widely used in periprosthetic infection, it cannot discriminate aseptic from septic inflammation. In this study we aimed to evaluate the role of FDG PET/CT and FDG-labelled leucocyte PET/CT in the diagnosis of periprosthetic infection.

METHODS

Of 54 patients with painful joint arthroplasty who were imaged by FDG PET/CT for diagnosis of periprosthetic infection examined, 46 (36 women, 10 men; mean age 61.04 ± 12.2 years, range 32-89 years) with 54 painful joint prostheses (19 hip, 35 knee) with grade 2 (above liver uptake) FDG accumulation on FDG PET/CT were included in the study and these 46 patients also underwent FDG-labelled leucocyte PET/CT. Final diagnoses were made by histopathological-microbiological culture or clinical follow-up.

RESULTS

The final diagnosis showed infection in 15 (28%) and aseptic loosening in 39 (72%) of the 54 prostheses. FDG PET/CT was found to have a positive predictive value of 28% (15/54). Since patients with no FDG uptake on FDG PET/CT were excluded from the study, the sensitivity, specificity, negative predictive value and accuracy could not be calculated. The sensitivity, specificity, and positive and negative predictive values of FDG-labelled leucocyte PET/CT were 93.3% (14/15), 97.4% (38/39), 93.3% and 97.4%, respectively.

CONCLUSION

Since FDG is not specific to infection, the specificity of FDG PET/CT was very low. FDG-labelled leucocyte PET/CT with its high specificity may be a useful method and better than labelled leucocyte scintigraphy in periprosthetic infection imaging.

Orbital positron emission tomography/computed tomography (PET/CT) imaging findings in Graves ophthalmopathy

Background

We aimed to describe orbital positron emission tomography/computed tomography (PET/CT) imaging findings, both structural and metabolic, in different clinical stages of Graves ophthalmopathy (GO). This prospective, observational, cross-sectional study examined 32 eyes of 16 patients with GO.

Methods

Patients were assessed with a complete ophthalmological evaluation and assigned a VISA classification for GO. All patients underwent serum thyroid hormone measurement, antibody profile, and 18-fluorodeoxyglucose positron emission tomography/computed tomography (18-FDG PET/CT) of the orbits. The 18-FDG uptake on PET images was expressed in terms of maximum standard uptake value (SUV_max). CT images were analyzed, and orbital structures were measured in millimeters. Vision, inflammation, strabismus, and overall appearance were assessed according to the VISA classification system, thyroid hormone levels, antibody values, 18-FDG uptake, and thickness of orbital structures.

Results

Altogether, 32 eyes of 16 patients (10 women, 6 men; mean age 44.31 ± 13 years, range 20–71 years) were included. Three patients were hypothyroid, seven were euthyroid, and six were hyperthyroid. CT measurements of extraocular muscle diameter were elevated (P < 0.05), and muscle 18-FDG uptake values were increased. Eyes with a clinical VISA inflammation score of ≤ 4 had an average extraocular muscle SUV_max of 3.09, and those with a score of ≥ 5 had an average SUV_max of 3.92 (P = 0.09), showing no clear correlation between clinically observed inflammation and 18-FDG uptake. 18-FDG uptake values also did not show a correlation with extraocular muscle diameter as measured by CT (R² = 0.0755, P > 0.05).

Conclusions

We demonstrated a lack of correlation between 18-FDG extraocular muscle uptake and either clinical inflammation score or muscle diameter. Although 18-FDG uptake has been used as an inflammation marker in other pathologies, inflammation in GO may be clinically detected in PET/CT-negative cases, and cases with negative clinical findings may show inflammation on PET/CT. Clinical evaluation is mandatory but may be insufficient and inaccurate for classifying GO. A larger and homogeneous sample size and further research is needed to define the role of PET/CT in detecting, grading, and follow-up of GO to optimize treatment of the inflammatory stage respect clinical methods currently used.

18-Fluorodeoxyglucose Uptake by Positron Emission Tomography in Extraocular Muscles of Patients with and without Graves' Ophthalmology

Objective. To compare 18-fluorodeoxyglucose (FDG) uptake by positron emission tomography (PET) in extraocular muscles (EOMs) of patients with Graves' ophthalmopathy (GO) versus patients without GO. Design. Prospective, observational, comparative, and cross-sectional study. Participants. Thirty-two eyes of patients with GO and seventy eyes of patients without GO. Methods. We prospectively included patients older than 18 years of age with and without GO. FDG-PET imaging study was performed; standardized unit value (SUV_max) was quantified in EOMs. Standard deviation and significant statistical difference (P < 0.05) were calculated. Results. Thirty-two eyes of sixteen patients of the GO group were included, with a mean age of 44.31 (20–71) years. Seventy eyes of thirty-five patients of the group without GO were included, with a mean age of 49.20 (24–77) years. EOMs average uptake of the groups with and without GO were 3.38 ± 1.31 and 1.89 ± 0.51 SUV_max (P < 0.05), respectively. Conclusion. FDG uptake was significantly increased in EOMs of patients with GO. PET gives valuable information and may be a helpful tool in detecting, localizing, and quantifying GO inflammation. Further research is needed to define the role of PET in detecting, grading, and following up GO in order to optimize treatment in the inflammatory stage.

In vivo cell tracking via ¹⁸F-fluorodeoxyglucose labeling: a review of the preclinical and clinical applications in cell-based diagnosis and therapy

The rising interest in using functional cells for diagnosis and treatment has created an urgent need for in vivo cell-tracking techniques. Certain advanced techniques, such as those involving reporter genes or nanoparticles, are still awaiting confirmation of their safety and feasibility in human patients. Tracking cells by labeling them with (18)F-fluorodeoxyglucose, a tracer clinically used in positron emission tomography (PET), may be one way to rapidly translate some of these principles from bench to bedside. The preliminary results are exciting, although further development, optimization, and validation are required. Here, several applications of the technique are surveyed: finding inflammatory foci, targeting cancer immunotherapies, tracking transplanted islet cells, and monitoring cardiac stem cells. Advantages, limitations, and prospects of the technique are discussed. These early experiences only highlight the existing need to improve cell-labeling techniques using PET tracers. This method may finally lead to the development of effective and convenient methods for clinical cell-tracking techniques involving PET/computed tomography.

PET/CT imaging in infectious conditions

New aggressive pathogens are responsible for the increasing incidence and difficult management of infections. Modern epidemics such as diabetes are frequently complicated by severe infections with subsequent high morbidity. Diagnosis (essentially early detection of infection) and also management decision making pose clinical challenges. Many resources are invested in developing precise, noninvasive diagnostic tests and efficient therapies for infectious processes. Nuclear medicine procedures are part of the evaluation armamentarium of patients with suspected or confirmed infection. Their strength relies on the fact that they are noninvasive tests that provide both functional as well as metabolic information early in the course of disease. Their limitations relate to the need for specific radiotracers and the rather low resolution of images. These limitations have been largely overcome by the hybrid PET/CT and SPECT/CT technology. PET/CT, primarily using FDG, is redefining the diagnostic work up and is currently leading to changes in the management of patients with suspected or known infections. The main indications for FDG PET/CT in infection, as well as updated literature results, are presented in the following review.

Dynamic 11C-methionine PET analysis has an additional value for differentiating malignant tumors from granulomas: an experimental study using small animal PET

PURPOSE

We evaluated whether the dynamic profile of L-(11)C-methionine (11C-MET) may have an additional value in differentiating malignant tumors from granulomas in experimental rat models by small animal positron emission tomography (PET).

METHODS

Rhodococcus aurantiacus and allogenic rat C6 glioma cells were inoculated, respectively, into the right and left calf muscles to generate a rat model bearing both granulomas and tumors (n=6). Ten days after the inoculations, dynamic 11C-MET PET was performed by small animal PET up to 120 min after injection of 11C-MET. The next day, after overnight fasting, the rats were injected with 18F-2-deoxy-2-fluoro-D-glucose (18F-FDG), and dynamic 18F-FDG PET was performed up to 180 min. The time-activity curves, static images, and mean standardized uptake value (SUV) in the lesions were calculated.

RESULTS

11C-MET uptake in the granuloma showed a slow exponential clearance after an initial distribution, while the uptake in the tumor gradually increased with time. The dynamic pattern of 11C-MET uptake in the granuloma was significantly different from that in the tumor (p<0.001). In the static analysis of 11C-MET, visual assessment and SUV analysis could not differentiate the tumor from the granuloma in all cases, although the mean SUV in the granuloma (1.48±0.09) was significantly lower than that in the tumor (1.72±0.18, p<0.01). The dynamic patterns, static images, and mean SUVs of 18F-FDG in the granuloma were similar to those in the tumor (p=NS).

CONCLUSION

Dynamic 11C-MET PET has an additional value for differentiating malignant tumors from granulomatous lesions, which deserves further elucidation in clinical settings.

Distribution of adoptively transferred porcine T-lymphoblasts tracked by (18)F-2-fluoro-2-deoxy-D-glucose and position emission tomography

INTRODUCTION

Autologous or allogeneic transfer of tumor-infiltrating T-lymphocytes is a promising treatment for metastatic cancers, but a major concern is the difficulty in evaluating cell trafficking and distribution in adoptive cell therapy. This study presents a method of tracking transfusion of T-lymphoblasts in a porcine model by (18)F-2-fluoro-2-deoxy-d-glucose ([(18)F]FDG) and positron emission tomography.

METHODS

T-lymphoblasts were labeled with the positron-emitting tracer [(18)F]FDG through incubation. The T-lymphoblasts were administered into the bloodstream, and the distribution was followed by positron emission tomography for 120 min. The cells were administered either intravenously into the internal jugular vein (n=5) or intraarterially into the ascending aorta (n=1). Two of the pigs given intravenous administration were pretreated with low-molecular-weight dextran sulphate.

RESULTS

The cellular kinetics and distribution were readily quantifiable for up to 120 min. High (78.6% of the administered cells) heterogeneous pulmonary uptake was found after completed intravenous transfusion. The pulmonary uptake was decreased either by preincubating and coadministrating the T-lymphoblasts with low-molecular-weight dextran sulphate or by administrating them intraarterially.

CONCLUSIONS

The present work shows the feasibility of quantitatively monitoring and evaluating cell trafficking and distribution following administration of [(18)F]FDG-labeled T-lymphoblasts. The protocol can potentially be transferred to the clinical setting with few modifications.

Nuclear imaging of autoimmunity: focus on IBD and RA

There is a need for methods to improve the diagnosis, patient staging and evaluation of therapeutic response in patients with autoimmune conditions to improve patient care. Inflammatory bowel disease (IBD) and rheumatoid arthritis (RA) are two inflammatory diseases characterized by involvement of innate and adaptive immune components that change the metabolic state of their respective target tissues, thus providing an opportunity for molecular imaging probes to detect such changes. Optimally, such probes and the imaging methods employed would be non-invasive, robust and reproducible, give a quantitative result, report on the status of the affected tissue(s) and respond to the effects of a therapeutic molecule. Positron emission tomography (PET) and single photon emission computed tomography (SPECT) are nuclear imaging approaches that have the potential to satisfy such requirements. In this review, the work to date and the potential of PET and SPECT imaging probes in these two inflammatory conditions, IBD and RA, are discussed.

Diagnostic value of noninvasive combined fluorine-18 labeled fluoro-2-deoxy-D-glucose positron emission tomography and computed tomography enterography in active Crohn's disease

BACKGROUND

The role of combined localized positron emission tomography (lPET) and computed tomography enterography (CTe) in Crohn's disease is unclear. We examined if this imaging modality using fluorine-18 labeled-fluoro-2-deoxy-D-glucose (FDG) could more effectively identify disease activity.

METHODS

52 lPET-CTe scans were analyzed in this retrospective study. CTe scores and FDG uptake were quantified. Correlations of CTe scores and standard uptake value (SUV) with C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), short Inflammatory Bowel Disease Questionnaire (sIBDq), and Harvey-Bradshaw index (HBI) were estimated using Pearson analysis. Imaging scores were compared to medical outcome by logistics regression model.

RESULTS

CTe scores correlated with SUV, but additional abnormal segments of small bowel were not identified. In all, 38 (79%) abnormal CTe segments demonstrated increased FDG uptake with mean SUVmax 4.77; 10 (21%) abnormal CTe segments lacked FDG accumulation, with mean SUVmax 1.27. There was no correlation between SUVmax and CRP, ESR, sIBDq, or HBI. There were no significant differences in clinical indices, biochemical parameters, and presence of multiple abnormal segments between medical responders and uptake were associated with failed medical therapy (P = 0.001).

CONCLUSIONS

PET scanning added to CTe did not identify additional abnormal segments when compared to CTe alone. Abnormal segments with mucosal enhancement on CTe that did not accumulate FDG were significantly associated with failure of medical therapy. A larger trial is warranted to confirm if combined lPET-CTe has an important role in the clinical management of stricturing Crohn's disease.

Micro-positron emission tomography in the evaluation of Trypanosoma cruzi-induced heart disease: Comparison with other modalities

Noninvasive assessment of cardiac structure and function is essential to understand the natural course of murine infection with Trypanosoma cruzi. Magnetic resonance imaging (MRI) and echocardiography have been used to monitor anatomy and function; positron emission tomography (PET) is ideal for monitoring metabolic events in the myocardium. Mice infected with T. cruzi (Brazil strain) were imaged 15-100 days post infection (dpi). Quantitative (18)F-FDG microPET imaging, MRI and echocardiography were performed and compared. Tracer ((18)F-FDG) uptake was significantly higher in infected mice at all days of infection, from 15 to 100 dpi. Dilatation of the right ventricular chamber was observed by MRI from 30 to 100 dpi in infected mice. Echocardiography revealed significantly reduced ejection fraction by 60 dpi. Combination of these three complementary imaging modalities makes it possible to noninvasively quantify cardiovascular function, morphology, and metabolism from the earliest days of infection through the chronic phase.

In vitro human leukocyte labeling with (64)Cu: an intraindividual comparison with (111)In-oxine and (18)F-FDG

We investigated labeling human leukocytes [white blood cells (WBCs)] in vitro with copper-64 (Cu) comparing labeling efficiency, viability and stability of Cu-WBCs with (111)In-oxine (In) WBCs and (18)F-FDG (FDG) WBCs.

METHODS

Leukocytes from 10 volunteers were labeled with Cu, In and FDG. Forty milliliters of venous blood was collected and leukocyte separation was performed according to standard methods. In-WBCs and FDG-WBCs were labeled according to published methods. For Cu-WBCs, tropolone initially was used as a single chelating agent. Because of poor intracellular Cu retention (54+/-4% at 3 h and 24+/-5% at 24 h), the fluorinated, membrane-permeable divalent cation chelator quin-MF was added. WBCs were incubated in 5 ml saline containing 100 microl of 1mM quin-MF/AM in 2% dimethyl sulfoxide and 74-185 MBq Cu-tropolone for 45 min at 37 degrees C. Labeling efficiencies; in vitro cellular viabilities at 1, 3 and 24 h; and in vitro stabilities at 1, 2, 3, 4 and 24 h (except FDG-WBCs) were determined.

RESULTS

Mean Cu-WBCs (87+/-4%) and In-WBCs (86+/-4%) labeling efficiencies were comparable and were significantly higher than FDG-WBCs (60+/-19%, P<.001). Cell viabilities, similar at 1 h, were significantly higher for (64)Cu-WBCs at 3 and 24 h. Intracellular retention of activity was always significantly higher for In-WBCs than for Cu-WBCs and FDG-WBCs. At 24 h, intracellular retention was 88+/-4% for In-WBCs and 79+/-6% for Cu-WBCs.

CONCLUSION

Cu-WBC labeling efficiency and viability were comparable or superior to In-WBCs and significantly higher than FDG-WBCs. Although significantly more activity eluted from Cu-WBCs than from In-WBCs, Cu-WBC probably is adequate for imaging. These data suggest that further investigation of in vitro copper-64-labeled leukocytes for PET imaging of infection is warranted.

Recent trends in soft-tissue infection imaging

This article discusses the current techniques and future directions of infection imaging with particular attention to respiratory, central nervous system, abdominal, and postoperative infections. The agents currently in use localize to areas of infection and inflammation. An infection-specific imaging agent would greatly improve the utility of scintigraphy in imaging occult infections. The superior spatial resolution of (18)F-fluorodeoxyglucose positron emission tomography ((18)F-FDG-PET) and its lack of reliance on a functional immune system, gives this agent certain advantages over the other radiopharmaceuticals. In respiratory tract infection imaging, an important advancement would be the ability to quantitatively delineate lung inflammation, allowing one to monitor the therapeutic response in a variety of conditions. Current studies suggest PET should be considered the most accurate quantitative method. Scintigraphy has much to offer in localizing abdominal infection as well as inflammation. We may begin to see a gradual increase in the usage of (18)F-FDG-PET in detecting occult abdominal infections. Commonly used modalities for imaging inflammatory bowel disease are scintigraphy with (111)In-oxine/(99m)Tc-HMPAO labeled autologous white blood cells. The literature on central nervous system infection imaging is relatively scarce. Few clinical studies have been performed and numerous new agents have been developed for this use with varying results. Further studies are needed to more clearly delineate the future direction of this field. In evaluating the postoperative spine, (99m)Tc-ciprofloxacin single-photon emission computed tomography (SPECT) was reported to be >80% sensitive in patients more than 6 months after surgery. FDG-PET has also been suggested for this purpose and may play a larger role than originally thought. It appears PET/computed tomography (CT) is gaining support, especially in imaging those with fever of unknown origin or nonfunctional immune systems. Although an infection-specific agent is lacking, the development of one would greatly advance our ability to detect, localize, and quantify infections. Overall, imaging such an agent via SPECT/CT or PET/CT will pave the way for greater clinical reliability in the localization of infection.

Myocardial imaging with 18F-fluoro-2-deoxyglucose positron emission tomography and magnetic resonance imaging in sarcoidosis

PURPOSE

Despite accumulating reports on the clinical value of (18)F-fluoro-2-deoxyglucose positron emission tomography (18F-FDG PET) and magnetic resonance imaging (MRI) in the assessment of cardiac sarcoidosis, no studies have systematically compared the images of these modalities.

METHODS

Twenty-one consecutive patients with suspected cardiac sarcoidosis underwent cardiac examinations that included 18F-FDG PET and MRI. The association of 18F-FDG PET and MRI findings with blood sampling data such as serum angiotensin converting enzyme levels was also evaluated.

RESULTS

Eight of 21 patients were diagnosed as having cardiac sarcoidosis according to the Japanese Ministry of Health and Welfare Guidelines for Diagnosing Cardiac Sarcoidosis. Sensitivity and specificity for diagnosing cardiac sarcoidosis were 87.5 and 38.5%, respectively, for 18F-FDG PET, and 75 and 76.9%, respectively, for MRI. When the 18F-FDG PET and MRI images were compared, 16 of 21 patients showed positive findings in one (n = 8) or both (n = 8) of the two modalities. In eight patients with positive findings on both images, the distribution of the findings differed among all eight cases. The presence of positive findings on 18F-FDG PET was associated with elevated serum angiotensin-converting enzyme levels; this association was not demonstrated on MRI.

CONCLUSIONS

Both 18F-FDG PET and MRI provided high sensitivity for diagnosing cardiac sarcoidosis in patients with suspected cardiac involvement, but the specificity of (18)F-FDG PET was not as high as previously reported. The different distributions of the findings in the two modalities suggest the potential of 18F-FDG PET and MRI in detecting different pathological processes in the heart.

Usefulness of 11C-methionine for differentiating tumors from granulomas in experimental rat models: a comparison with 18F-FDG and 18F-FLT

Many clinical PET studies have shown that increased (18)F-FDG uptake is not specific to malignant tumors. (18)F-FDG is also taken up in inflammatory lesions, particularly in granulomatous lesions such as sarcoidosis or active inflammatory processes after chemoradiotherapy, making it difficult to differentiate malignant tumors from benign lesions, and is the main source of false-positive (18)F-FDG PET findings in oncology. These problems may be overcome by multitracer studies using 3'-deoxy-3'-(18)F-fluorothymidine ((18)F-FLT) or l-(11)C-methionine. However, (18)F-FLT or (11)C-methionine uptake in granulomatous lesions remains unclarified. In this study, the potentials of (18)F-FLT and (11)C-methionine in differentiating malignant tumors from granulomas were compared with (18)F-FDG using experimental rat models.

METHODS

Dual-tracer tissue distribution studies using (18)F-FDG and (3)H-FLT (groups I and III) or (18)F-FDG and (14)C-methionine (groups II and IV) were performed on rats bearing both granulomas (Mycobacterium bovis bacillus Calmette-Guérin [BCG]-induced) and hepatomas (KDH-8-induced) (groups I and II) or on rats bearing both turpentine oil-induced inflammation and hepatomas (groups III and IV). One hour after the injection of a mixture of (18)F-FDG and (3)H-FLT or of (18)F-FDG and (14)C-methionine, tissues were excised to determine the radioactivities of (18)F-FDG, (3)H-FLT, and (14)C-methionine (differential uptake ratio).

RESULTS

Mature epithelioid cell granuloma formation and massive lymphocyte infiltration were observed in the granuloma tissue induced by BCG, histologically similar to sarcoidosis. The granulomas showed high (18)F-FDG uptake comparable to that in the hepatomas (group I, 8.18 +/- 2.40 vs. 9.13 +/- 1.52, P = NS; group II, 8.43 +/- 1.45 vs. 8.91 +/- 2.32, P = NS). (14)C-Methionine uptake in the granuloma was significantly lower than that in the hepatoma (1.31 +/- 0.22 vs. 2.47 +/- 0.60, P < 0.01), whereas (3)H-FLT uptake in the granuloma was comparable to that in the hepatoma (1.98 +/- 0.70 vs. 2.30 +/- 0.67, P = NS). Mean uptake of (18)F-FDG, (3)H-FLT, and (14)C-methionine was markedly lower in the turpentine oil-induced inflammation than in the tumor.

CONCLUSION

(14)C-Methionine uptake was significantly lower in the granuloma than in the tumor, whereas (18)F-FDG and (3)H-FLT were not able to differentiate granulomas from tumors. These results suggest that (14)C-methionine has the potential to accurately differentiate malignant tumors from benign lesions, particularly granulomatous lesions, providing a biologic basis for clinical PET studies.

Nonprosthesis orthopedic applications of (18)F fluoro-2-deoxy-D-glucose PET in the detection of osteomyelitis

This article describes the impact of [(18)F]2-fluoro-2-deoxy-D-glucose (FDG) PET in the diagnosis of non-prosthesis-related orthopedic infections and inflammation. FDG-PET has an excellent sensitivity in the detection of osteomyelitis (OM). Early data indicate that FDG-PET may be more specific than MRI in diagnosing OM. The role of the combination of FDG and PET-CT in the diagnosis of OM is likely to be determined as this combination is used on a routine basis. Early data from studies in rheumatoid arthritis indicate that FDG-PET is highly accurate in early diagnosis and that it provides results comparable to the most advanced conventional techniques.

Extensive FDG uptake and its modification with corticosteroid in a granuloma rat model: an experimental study for differentiating granuloma from tumors

INTRODUCTION

Increased (18)F-fluorodeoxyglucose (FDG) uptake in inflammatory lesions, particularly in granulomatous inflammation (e.g., sarcoidosis), makes it difficult to differentiate malignant tumors from benign lesions and is the main source of false-positive FDG-PET findings in oncology. Here, we developed a rat granuloma model and examined FDG uptake in the granuloma. The effects of corticosteroid on FDG uptake in the granuloma were compared with those in a malignant tumor.

METHODS

Rats were inoculated with Mycobacterium bovis bacillus Calmette-Guérin (BCG) or allogenic hepatoma cells, and subdivided into control and pretreated (methylprednisolone acetate, 8 mg/kg i.m.) groups. Radioactivity in tissues was determined 1 h after the FDG injection. FDG-PET was performed in rats bearing BCG granulomas or tumors before and after prednisolone treatment.

RESULTS

Mature epithelioid cell granuloma-formation and massive lymphocyte-infiltration were observed in the control group of granuloma, histologically similar to sarcoidosis. The mean FDG uptake in the granuloma was comparable to that in the hepatoma. Prednisolone reduced epithelioid cell granuloma-formation and lymphocyte-infiltration. Prednisolone significantly decreased the level of FDG uptake in the granuloma (52% of control), but not in the hepatoma. The FDG uptake levels in the granulomas and tumors were clearly imaged with PET.

CONCLUSION

We developed an intramuscular granuloma rat model that showed a high FDG uptake comparable to that of the tumor. The effect of prednisolone pretreatment on FDG uptake was greater in the granuloma than in the tumor. These results suggest that BCG-induced granuloma may be a valuable model and may provide a biological basis for FDG studies.

Nanosystems for simultaneous imaging and drug delivery to T cells

The T-cell response defines the pathogenesis of many common chronic disease states, including diabetes, rheumatoid arthritis, and transplant rejection. Therefore, a diagnostic strategy that visualizes this response can potentially lead to early therapeutic intervention, avoiding catastrophic organ failure or prolonged sickness. In addition, the means to deliver a drug dose to those cells in situ with the same specificity used to image those cells would provide for a powerful therapeutic alternative for many disease states involving T cells. In this report, we review emerging nanosystems that can be used for simultaneous tracking and drug delivery to those cells. Because of their versatility, these systems--which combine specific receptor targeting with an imaging agent and drug delivery--are suited to both basic science and applications, from developing therapeutic strategies for autoimmune and alloimmune diseases, to noninvasive tracking of pathogenic T-cell migration.

In vivo cellular imaging of lymphocyte trafficking by MRI: A tumor model approach to cell-based anticancer therapy

The aim of this study was to demonstrate the feasibility of in vivo cell tracking to monitor anticancer cell therapy by means of a high-resolution noninvasive MRI method. Ovalbumin-specific splenocytes (OT-1) labeled with anionic gamma-Fe2O3 superparamagnetic iron oxide (SPIO) nanoparticles were adoptively transferred into C57BL/6 mice with growing ovalbumin-expressing tumors. OT-1 cells were tracked in vivo by 7 T MRI 24, 48, and 72 hr after they were injected. The results showed significant negative enhancement of the spleen at 24 hr, and of the tumor at 48 and 72 hr, after labeled cell injection. This suggests that the lymphocytes initially homed toward the spleen and were then recruited by the tumor. The presence of labeled cells was confirmed in ex vivo by 9.4 T microimaging of tumors and magnetic sorting of spleen cells. These results confirm that MR tracking of lymphocytes is feasible in vivo. This high-resolution imaging method could be used to improve the monitoring of immune cell therapy.