(18)F-FDG and (18)F-NaF PET/CT demonstrate coupling of inflammation and accelerated bone turnover in rheumatoid arthritis

EXPLORing Arthritis with Total-body Positron Emission Tomography

Arthritis has significant adverse consequences on musculoskeletal tissues and often other organs of the body. Current methods for clinical evaluation of arthritis are suboptimal, and biomarkers that are objective and measurable indicators for monitoring of arthritis disease activity are in critical demand. Recently, total-body positron emission tomography (PET) has been developed that can collect imaging signals synchronously from the entire body at ultra-low doses and reduced scan times. These scanners have increased signal collection efficiency that overcomes several limitations of standard PET scanners in the evaluation of arthritis, and they may potentially provide biomarkers to assess local and systemic impact of the arthritis disease process. This article reviews current results from using total-body PET in the assessment of common arthritic conditions, and it outlines future opportunities and challenges.

The prognostic value of 99m Tc-glucosamine imaging in patients with rheumatoid arthritis: a single center prospective study

OBJECTIVES

Poor prognostic factors in rheumatoid arthritis (RA) are associated with a more severe form of the disease. Nuclear medicine functional imaging has shown remarkable merit at identifying active disease in patients with RA and is increasingly being used in this regard. However, its prognostic value has not been evaluated thoroughly. We aimed to assess the prognostic value of technetium-99m ( 99m Tc-) glucosamine imaging in patients with RA.

METHODS

Twenty-two participants diagnosed by an experienced rheumatologist with RA were recruited for inclusion in the study. Blood samples were obtained from each participant for baseline C-reactive protein, erythrocyte sedimentation rate, rheumatoid factor (RF) and anti-cyclic citrullinated peptide (anti-CCP) antibody titer. On the same day, each participant was injected with 20-25 millicurie (mCi) of 99m Tc-glucosamine. Planar and single-photon emission computed tomography images of known disease sites were acquired up to 2 hours after radiopharmaceutical administration. Affected joints were qualitatively assessed and graded for 99m Tc-glucosamine uptake and compared with blood results.

RESULTS

All participants affected joints had an increased uptake of the radiopharmaceutical, with 14 (63.6%) having elevated RF and anti-CCP antibody titers. Eight of the 14 patients with increased RF and anti-CCP antibodies had grade 3 uptake of 99m Tc-glucosamine. The remaining 6 had grade 2 uptake. A significant correlation between higher grade uptake and increased levels of RF and anti-CCP antibodies ( P  = 0.031) was observed.

CONCLUSION

We found a strong correlation between high-grade disease on imaging and the presence of RF and anti-CCP antibodies in patients with RA.

Imaging in inflammatory arthritis: progress towards precision medicine

Imaging techniques such as ultrasonography and MRI have gained ground in the diagnosis and management of inflammatory arthritis, as these imaging modalities allow a sensitive assessment of musculoskeletal inflammation and damage. However, these techniques cannot discriminate between disease subsets and are currently unable to deliver an accurate prediction of disease progression and therapeutic response in individual patients. This major shortcoming of today's technology hinders a targeted and personalized patient management approach. Technological advances in the areas of high-resolution imaging (for example, high-resolution peripheral quantitative computed tomography and ultra-high field MRI), functional and molecular-based imaging (such as chemical exchange saturation transfer MRI, positron emission tomography, fluorescence optical imaging, optoacoustic imaging and contrast-enhanced ultrasonography) and artificial intelligence-based data analysis could help to tackle these challenges. These new imaging approaches offer detailed anatomical delineation and an in vivo and non-invasive evaluation of the immunometabolic status of inflammatory reactions, thereby facilitating an in-depth characterization of inflammation. By means of these developments, the aim of earlier diagnosis, enhanced monitoring and, ultimately, a personalized treatment strategy looms closer.

18F-FDG and 18F-NaF PET/CT Global Assessment of Large Joint Inflammation and Bone Turnover in Rheumatoid Arthritis

Rheumatoid arthritis (RA) involves chronic inflammation of synovial joints, causing pain, stiffness, and limited mobility. ¹⁸F-sodium fluoride (NaF) is a PET tracer whose uptake reflects bone turnover, while ¹⁸F-fludeoxyglucose (FDG) shows glucose metabolism and can serve as a marker for inflammation. The aim of this study is to determine the feasibility of calculating the FDG and NaF mean standardized uptake value (SUVmean) in the knee joint, hip joint, and sacroiliac (SI) joint of RA patients and to determine their association with patient characteristics. Prospective FDG-PET/CT as well as NaF-PET/CT imaging was performed on 18 RA patients. The global SUVmean was calculated on FDG-PET/CT and NaF-PET/CT images using a semiautomated CT-based method of segmentation. FDG and NaF uptake were found to be significantly correlated in the knee (r = 0.77, p < 0.001), but not in the hip and SI joints. In the knee, both NaF SUVmean and FDG SUVmean were significantly correlated with body weight, BMI, leptin, and sclerostin levels (p < 0.05). NaF SUVmean was significantly positively correlated with BMI and leptin for both the hip and SI joints (p < 0.05). No significant correlation was observed between either PET parameter and age, height, erythrocyte sedimentation rate (ESR), and interleukins 1 and 6 (IL-1 and IL-6); however, FDG was correlated with inflammatory markers such as C-reactive protein (CRP) and patient global visual analogue scale (VAS-PtGlobal) in some joints. In this study, both FDG and NaF uptake were quantified in large joints of patients with RA using CT segmentation. NaF and FDG SUVmean were correlated with clinical variables related to body weight and adiposity, suggesting that degenerative joint disease may play a larger role in influencing the uptake of these tracers in large joints than RA disease activity. FDG and its correlation with markers of inflammation such as CRP and VAS-PtGlobal suggests that this tracer may serve as a more specific marker for RA disease activity than NaF. Larger prospective and longitudinal data are necessary to gain a better understanding of the roles of FDG and NaF in evaluating RA joint activity in these joints.

The effects of limb laterality and age on the inflammation and bone turnover of the acromioclavicular shoulder joint: 18 F-fluorodeoxyglucose and 18 F-sodium-fluoride-PET/computed tomography study

PURPOSE

The acromioclavicular (AC) joint is a common site of injury and degenerative changes such as osteoarthritis (OA) of the shoulder. Physical manifestations of OA are preceded by molecular changes, detection of which may enhance early prophylaxis and monitoring of disease progression. In this study, we investigate the use of 18 F-FDG and 18 F-NaF-PET/CT to assess the effects of limb laterality and age on the inflammation and bone turnover of the AC shoulder joint.

METHODS

We analyzed FDG and NaF-PET/CT scans of 41 females (mean age of 43.9 ± 14.2 years) and 45 males (mean age of 44.5 ± 13.8 years) using a semiquantitative technique based on predefined ROI.

RESULTS

There was a greater NaF uptake in the right side of the AC joint compared with the left in both females (left: 2.22 ± 1.00; right: 3.08 ± 1.18; P < 0.0001) and males (left: 2.57 ± 1.49; right: 2.99 ± 1.40; P = 0.003). No consistent correlation between age and NaF or FDG uptakes were found in both females and males. There was also a positive correlation between FDG and NaF uptakes in both left ( P = 0.01; r = 0.37) and right ( P = 0.0006; r = 0.53) AC joints of male subjects.

CONCLUSION

Our study is the first to reveal the varying effect of right-left limb laterality and aging on FDG and NaF uptake at the AC joint. Future studies correlating the history of shoulder trauma, pain, and degenerative change with FDG and NaF-PET/CT findings will be critical in the adoption of molecular imaging in the clinical setting.

18F-Sodium Fluoride PET as a Diagnostic Modality for Metabolic, Autoimmune, and Osteogenic Bone Disorders: Cellular Mechanisms and Clinical Applications

In a healthy body, homeostatic actions of osteoclasts and osteoblasts maintain the integrity of the skeletal system. When cellular activities of osteoclasts and osteoblasts become abnormal, pathological bone conditions, such as osteoporosis, can occur. Traditional imaging modalities, such as radiographs, are insensitive to the early cellular changes that precede gross pathological findings, often leading to delayed disease diagnoses and suboptimal therapeutic strategies. ¹⁸F-sodium fluoride (¹⁸F-NaF)-positron emission tomography (PET) is an emerging imaging modality with the potential for early diagnosis and monitoring of bone diseases through the detection of subtle metabolic changes. Specifically, the dissociated ¹⁸F^- is incorporated into hydroxyapatite, and its uptake reflects osteoblastic activity and bone perfusion, allowing for the quantification of bone turnover. While ¹⁸F-NaF-PET has traditionally been used to detect metastatic bone disease, recent literature corroborates the use of ¹⁸F-NaF-PET in benign osseous conditions as well. In this review, we discuss the cellular mechanisms of ¹⁸F-NaF-PET and examine recent findings on its clinical application in diverse metabolic, autoimmune, and osteogenic bone disorders.

Clinical utility of F-18 sodium fluoride PET/CT for estimating disease activity in patients with rheumatoid arthritis

Background

The present study aimed to investigate the clinical implication of F-18 sodium fluoride (NaF) positron emission tomography/computed tomography (PET/CT) for assessing the disease activity of rheumatoid arthritis.

Methods

Seventeen patients with rheumatoid arthritis according to the 2010 American College of Rheumatology/European League Against Rheumatism classification criteria were prospectively enrolled. All enrolled patients underwent F-18 NaF PET/CT along with physical examination, blood test, and ultrasonography. On PET/CT images, two quantitative parameters, F-18 NaF uptake of the joint (joint SUV) and joint-to-bone uptake ratio, were measured for each of the 28 joints included in calculating the disease activity score in 28 joints using erythrocyte sedimentation rate (DAS28-ESR). The relationship between PET/CT parameters and clinical factors and the predictive values of PET/CT parameters for joints with synovitis and high disease activity were evaluated.

Results

Tender joints (joint SUV, 13.6±8.4; joint-to-bone uptake ratio, 1.70±1.02) and both tender and swollen joints (joint SUV, 13.9±5.4; joint-to-normal bone uptake ratio, 1.81±0.76) had significantly higher joint SUV and joint-to-bone uptake ratio than joints without synovitis (joint SUV, 6.0±2.4; joint-to-bone uptake ratio, 0.74±0.31; P<0.001). On correlation analysis, summed joint SUV (P=0.002, correlation coefficient=0.705) and summed joint-to-bone uptake ratio (P<0.001, correlation coefficient=0.861) of 28 joints showed strong positive correlation with DAS28-ESR after adjustment for age and body mass index. Summed joint SUV showed significant positive correlations with ultrasonography findings (grey scale ultrasonography: P=0.047, correlation coefficient =0.468; power Doppler ultrasonography: P=0.045, correlation coefficient =0.507). On the receiver operating characteristic curve analysis, the sensitivity and specificity for predicting synovitis were 83.2% and 92.7%, respectively, for joint SUV and 81.5% and 90.7%, respectively, for joint-to-bone uptake ratio. Moreover, the summation of both PET/CT parameters of 28 joints showed a diagnostic accuracy of 100.0% for predicting high disease activity in rheumatoid arthritis.

Conclusions

Summed joint uptake on F-18 NaF PET/CT had a strong positive correlation with DAS28-ESR and accurately predicted high disease activity. F-18 NaF PET/CT parameters might be used as an imaging biomarker for disease activity in rheumatoid arthritis.

Trial registration

This study was registered at the Clinical Research Information Service of the Korea (CRIS, http://cris.nih.go.kr/cris/en; registry number, KCT0002597; registered November 2017).

Imaging Inflammation with Positron Emission Tomography

The impact of inflammation on the outcome of many medical conditions such as cardiovascular diseases, neurological disorders, infections, cancer, and autoimmune diseases has been widely acknowledged. However, in contrast to neurological, oncologic, and cardiovascular disorders, imaging plays a minor role in research and management of inflammation. Imaging can provide insights into individual and temporospatial biology and grade of inflammation which can be of diagnostic, therapeutic, and prognostic value. There is therefore an urgent need to evaluate and understand current approaches and potential applications for imaging of inflammation. This review discusses radiotracers for positron emission tomography (PET) that have been used to image inflammation in cardiovascular diseases and other inflammatory conditions with a special emphasis on radiotracers that have already been successfully applied in clinical settings.

Novel Musculoskeletal and Orthopedic Applications of 18F-Sodium Fluoride PET

PET imaging with ¹⁸F-sodium fluoride (NaF), combined with computed tomography or magnetic resonance, is a sensitive method of assessing bone turnover. Although NaF-PET is gaining popularity in detecting prostate cancer metastases to bone marrow, osseous changes represent secondary effects of cancer cell growth. PET tracers more appropriate for assessing prostate cancer metastases directly portray malignant activity and include ¹⁸F-fluciclovine and prostatic specific membrane antigen ligands. Recent studies investigating NaF-PET suggest utility in the assessment of benign musculoskeletal disorders. Emerging applications in assessing traumatic injuries, joint disease, back pain, orthopedic complications, and metabolic bone disease are discussed.

Clinical Use of Quantitative Analysis of Bone Scintigraphy to Assess the Involvement of Arthritis Diseases in Patients with Joint Symptoms

We aimed to compare the diagnostic ability of quantitative analysis of bone scintigraphy with that of visual analysis for identifying arthritis disease involvement in patients with joint symptoms. We retrospectively included 93 patients with joint symptoms who underwent Tc-99m methylene diphosphonate bone scintigraphy for evaluating arthritis disease involvement. Bone scintigraphy images were visually and quantitatively analyzed using an in-house software by two reviewers. On quantitative analysis, joint uptake ratio was measured for 64 joints in 14 joints areas. The inter-rater agreement of visual and quantitative analyses was assessed, and diagnostic abilities were compared based on the area under the receiver operating characteristic (ROC) curve (AUC) values. Regarding visual analysis, there was a moderate degree of inter-rater agreement (kappa coefficient of 0.597), while there was a substantial inter-rater agreement (concordance correlation coefficient of 0.987) in the measurement of the joint uptake ratio. The comparisons of ROC curves for the total 5941 joints revealed that the joint uptake ratio had a significantly higher AUC value (0.789) to detect the affected joint than that of the visual analysis (p < 0.001). Quantitative analysis using joint uptake ratio showed substantial reproducibility and higher diagnostic ability to detect joints involving arthritis diseases than visual analysis on bone scintigraphy.

Diagnosis and Monitoring of Osteoporosis with Total-Body 18F-Sodium Fluoride-PET/CT

In recent years, ¹⁸F-Sodium Fluoride (NaF)-PET/CT has seen its role in the detection and management of osteoporosis increase. This article reviews the extent of this application in the literature, its efficacy compared with other comparable imaging tools, and how total-body PET/CT combined with global disease assessment can revolutionize measurement of total osteoporotic disease activity. NaF-PET/CT eventually can be the modality of choice for metabolic bone disorders, especially with these advances in technology and computation.

Infection and Inflammation Imaging: Beyond FDG

This review discusses nuclear imaging of inflammation using molecular probes beyond fluoro-d-glucose, is structured by cellular targets, and focuses on those tracers that have been successfully applied clinically.

Dose down-titration of biological disease-modifying antirheumatic drugs in daily clinical practice: Shared decision-making and patient treatment preferences in Japanese patients with rheumatoid arthritis

AIM

To determine characteristics of rheumatoid arthritis (RA) patients in Japan who received the same biological disease-modifying antirheumatic drugs (bDMARDs) for at least 6 months and to identify factors associated with successful down-titration of bDMARDs dependent on shared decision-making.

METHODS

We included consecutive RA patients who received the same bDMARD with low disease activity or remission for at least 6 months in our two university hospitals. Patients treated with the bDMARD standard dose were defined as SD, while those treated with bDMARD down-titration were defined as DT. We retrospectively reviewed clinical charts and compared data between the two groups.

RESULTS

Of 288 patients with RA, 204 (70.8%) and 84 (29.2%) continued standard dose treatment and underwent down-titration treatment, respectively. Sixty-six of 84 (78.6%) down-titration-treated patients continued to show low disease activity or remission, whereas 18 (21.4%) relapsed 18.9 ± 24.4 months after bDMARD down-titration was started. Univariate predictor analysis showed that the probable factors of down-titration were no history of bDMARD treatment (P = .001) and low initial Disease Activity Assessment of 28 joint score (P = .048). Other clinical characteristics had no significant relationship with successful down-titration.

CONCLUSIONS

Thus, bDMARD-naïve patients and those with low initial disease activity are more likely to agree to attempt down-titration. However, the timing and method of down-titration should be made in shared decision-making between patients and rheumatologists.

Multimodal [18 F]FDG PET/CT Is a Direct Readout for Inflammatory Bone Repair: A Longitudinal Study in TNFα Transgenic Mice

In rheumatoid arthritis (RA), chronic joint inflammation leading to bone and cartilage damage is the major cause of functional impairment. Whereas reduction of synovitis and blockade of joint damage can be successfully achieved by disease modifying antirheumatic therapies, bone repair upon therapeutic interventions has only been rarely reported. The aim of this study was to use fluorodeoxyglucose ([¹⁸ F]FDG) and [¹⁸ F]fluoride µPET/CT imaging to monitor systemic inflammatory and destructive bone remodeling processes as well as potential bone repair in an established mouse model of chronic inflammatory, erosive polyarthritis. Therefore, human tumor necrosis factor transgenic (hTNFtg) mice were treated with infliximab, an anti-TNF antibody, for 4 weeks. Before and after treatment period, mice received either [¹⁸ F]FDG, for detecting inflammatory processes, or [¹⁸ F]fluoride, for monitoring bone remodeling processes, for PET scans followed by CT scans. Standardized uptake values (SUV_mean ) were analyzed in various joints and histopathological signs of arthritis, joint damage, and repair were assessed. Longitudinal PET/CT scans revealed a significant decrease in [¹⁸ F]FDG SUVs in affected joints demonstrating complete remission of inflammatory processes due to TNF blockade. In contrast, [¹⁸ F]fluoride SUVs could not discriminate between different severities of bone damage in hTNFtg mice. Repeated in vivo CT images proved a structural reversal of preexisting bone erosions after anti-TNF therapy. Accordingly, histological analysis showed complete resolution of synovial inflammation and healing of bone at sites of former bone erosion. We conclude that in vivo multimodal [¹⁸ F]FDG µPET/CT imaging allows to quantify and monitor inflammation-mediated bone damage and reveals not only reversal of synovitis but also bone repair upon TNF blockade in experimental arthritis. © 2019 The Authors. Journal of Bone and Mineral Research Published by Wiley Periodicals, Inc.

Kinetic [18F]-Fluoride of the Knee in Normal Volunteers

PURPOSE

[F]-sodium fluoride ([F]NaF) is a well-established bone-seeking agent that has shown promise to assess bone turnover in a variety of disorders, but its distribution in healthy knee joints has not been explored. This study aimed to investigate parametric values for [F]NaF uptake in various bone tissues types of the knee and their spatial distributions.

METHODS

Twelve healthy subjects were hand-injected with 92.5 MBq of [F]NaF and scanned on a 3-T PET/MRI system. Listmode PET data for both knees were acquired for 50 minutes from injection simultaneously with MRI Dixon and angiography data. The image-derived input function was determined from the popliteal artery. Using the Hawkins model, Patlak analysis was performed to obtain Ki (Ki) values and nonlinear regression analysis to obtain Ki, K1, k3/(k2 + k3), and blood volume. Comparisons for the measured kinetic parameters, SUV, and SUVmax were made between tissue types (subchondral, cortical, and trabecular bone) and between regional subsections of subchondral bone.

RESULTS

Cortical bone had the highest [F]NaF uptake differing significantly in all measured parameters when compared with trabecular bone and significantly higher SUVmax and K1 than subchondral bone. Subchondral bone also had significantly higher SUV, SUVmax, and Ki than trabecular bone tissue. Regional differences were observed in K1 and k3/(k2 + k3) values.

CONCLUSIONS

Quantitative [F]NaF PET is sensitive to variations in bone vascularization and metabolism in the knee joint.

Diagnosis and Monitoring of Osteoporosis With 18F-Sodium Fluoride PET: An Unavoidable Path for the Foreseeable Future

The prevalence of metabolic bone diseases particularly osteoporosis and its precursor, osteopenia, continue to grow as serious global health issues today. On a worldwide perspective, 200million people suffer from osteoporosis and in 2005, over 2million fracture incidents were estimated due to osteoporosis in the United States. Currently, osteoporosis and other metabolic bone diseases are evaluated primarily through dual energy X-ray absorptiometry, and rarely by bone biopsy with tetracycline labeling or Technetium-99m (^99mTc) based bone scintigraphy. Deficiencies in these methods have prompted the use of more precise methods of assessment. This review highlights the use of ¹⁸F-sodium fluoride (NaF) with PET (NaF-PET), NaF-PET/CT, or NaF-PET/MRI in the evaluation of osteoporosis and osteopenia in the lumbar spine and hip. This imaging modality provides a molecular perspective with respect to the underlying metabolic alterations that lead to osseous disorders by measuring bone turnover through standardized uptake values. Its sensitivity and ability to examine the entire skeletal system make it a more superior imaging modality compared to standard structural imaging techniques. Further research is needed to determine its accuracy in reflecting the efficacy of therapeutic interventions in metabolic bone diseases.

Rituximab for refractory rapidly progressive interstitial lung disease related to anti-MDA5 antibody-positive amyopathic dermatomyositis

To report our experience in using rituximab (RTX) for treating refractory rapidly progressive interstitial lung disease (RP-ILD) complicating anti-melanoma differentiation-associated gene 5 antibody (anti-MDA5 Ab)-positive amyopathic dermatomyositis (ADM). Medical records of four ADM patients with refractory RP-ILD treated with RTX therapy were reviewed retrospectively. All four patients were tested positive for anti-MDA5 Ab and failed to respond to high-dose systemic steroid and other intensive immunosuppressive therapies. Respiratory symptoms, lung function tests, and high-resolution computed tomography (HRCT) of the chest were compared before and after the first course of RTX. After RTX treatment, all four patients had improvement in the respiratory symptoms in terms of New York Heart Association classification. Two patients successfully had their supplementary oxygen therapy weaned off. The lung function tests were significantly better in all patients. The HRCT showed improvement in three patients while the other one remained static. The recalcitrant vasculitic rashes associated with the anti-MDA5 Ab were also better in all patients. The average daily prednisolone dose dropped from 20 to 6.25 mg post-treatment. None of the patients died throughout the follow-up period which ranged from 6 months to 2 years. However, two patients developed chest infection and one wound infection within 6 months after the RTX infusion. Our results suggest that RTX may be a useful therapy for anti-MDA5 Ab-positive ADM associated with RP-ILD. However, infection is the major risk.

Molecular Imaging of Inflammatory Arthritis and Related Disorders

Rheumatic disorders comprise a number of diseases that range from benign, mildly symptomatic degenerative disease to severe systemic disorders such as giant-cell vasculitis with dramatic consequences such as acute blindness. The former is relatively common, whereas the latter is rare. In between, commonly encountered disorders such as rheumatoid arthritis and the various spondyloarthritides, with or without peripheral enthesitis, are daily challenges for the caring physician. Clinical evaluation is of utmost importance and is constantly described under the form of specialist guidelines in all parts of the world. Objective assessment of inflammatory arthritis and related disorders is of interest both for the care of the individual patient and for the assessment of the effects of the many novel experimental therapies proposed in this field, most of them being very expensive. High-resolution ultrasound, CT and spectral CT, MRI using various sequences, and molecular imaging using either gamma camera imaging (including SPECT-CT) or PET-CT are all proposed for a better assessment of these diseases. This review focuses on the several nuclear medicine techniques that are or may become useful to helping provide better patient care in this field and is mainly oriented to inflammatory rheumatic disorders, excluding mechanical degenerative diseases.

Spectrum of Benign Bone Conditions on NaF-PET

Fluoride imaging with ¹⁸F (NaF-PET), although not a new technique, is becoming increasingly utilized for evaluation of skeletal metastatic disease using PET/CT. As its use becomes more widespread, a variety of nonmalignant bone disorders will be encountered by the interpreting physician. It is important, therefore, to recognize these nonmalignant conditions to avoid errors in interpretation. Beyond this, there is increasing evidence in the literature that NaF-PET/CT imaging may provide valuable information for the primary diagnosis of these nonmalignant conditions, and furthermore may provide insight into the underlying biology leading to management decisions. In this article, we review a spectrum of benign bone conditions that can be visualized on NaF-PET.

Diagnosis and management of rheumatoid arthritis; What is the current role of established and new imaging techniques in clinical practice?

Ultrasound and magnetic resonance imaging (MRI) have become established imaging techniques for the management of rheumatoid arthritis. Several publications have pointed out the advantages of these techniques for a more complete evaluation of the inflammation and structural damage at joint level. Recently new imaging techniques as the positron emission tomography (PET) associated with computed tomography (CT) or MRI scan, and the optical imaging have been introduced in the panorama. This article presents the advantages and limitations of each imaging techniques in light with the recent publications.

Recurrent surgical site infection of the spine diagnosed by dual (18)F-NaF-bone PET/CT with early-phase scan

We report a case of a 31-year-old man who showed recurrently elevated level of the serum inflammatory marker C-reactive protein (CRP) after spinal operation. He underwent (18)F-flurodeoxyglucose ((18)F-FDG) positron emission tomography/computed tomography (PET/CT) and dual (18)F-sodium-fluoride ((18)F-NaF) PET/CT with an additional early-phase scan to find a hidden inflammation focus. Only mildly increased (18)F-FDG was found at the surgical site of T11 spine on (18)F-FDG PET/CT. In contrast, dual (18)F-NaF bone PET/CT with early-phase scan demonstrated focal active inflammation at the surgical site of T11 spine. After a revision operation of the T11 spine, serum CRP level decreased to the normal range without any symptom or sign of inflammation. Inflammatory focus in the surgical site of the spine can be detected with using dual (18)F-NaF bone PET/CT scan with early-phase scan.