Recommendations of the French Society of Rheumatology for the management in current practice of patients with Polymyalgia Rheumatica

OBJECTIVE

To develop recommendations for the routine management of patients with polymyalgia rheumatica (PMR) Methods: Following standard procedures, a systematic review of the literature by 5 supervised junior rheumatologists, based on the questions selected by the steering committee (5 senior rheumatologists), was used as the basis for working meetings, followed by a one-day plenary meeting with the working group (15 members), leading to the development of the wording and determination of the strength of the recommendations and the level of agreement of the experts.

RESULTS

Five general principles and 19 recommendations were drawn up. Three recommendations relate to diagnosis and the use of imaging, and 5 to the assessment of the disease, its activity and co-morbidities. Non-pharmacological therapies are the subject of one recommendation. Three recommendations concern initial treatment based on general corticosteroid therapy, 5 concern the reduction of corticosteroid therapy and follow-up, and 2 concern corticosteroid dependence and steroid-sparing treatments (anti-IL-6).

CONCLUSION

These recommendations take account of current data on PMR, with the aim of reducing exposure to corticosteroid therapy and its side effects in a fragile population. They are intended to be practical, to help practitioners in the day-to-day management of patients with PMR.

PET KinetiX-A Software Solution for PET Parametric Imaging at the Whole Field of View Level

Kinetic modeling represents the ultimate foundations of PET quantitative imaging, a unique opportunity to better characterize the diseases or prevent the reduction of drugs development. Primarily designed for research, parametric imaging based on PET kinetic modeling may become a reality in future clinical practice, enhanced by the technical abilities of the latest generation of commercially available PET systems. In the era of precision medicine, such paradigm shift should be promoted, regardless of the PET system. In order to anticipate and stimulate this emerging clinical paradigm shift, we developed a constructor-independent software package, called PET KinetiX, allowing a faster and easier computation of parametric images from any 4D PET DICOM series, at the whole field of view level. The PET KinetiX package is currently a plug-in for Osirix DICOM viewer. The package provides a suite of five PET kinetic models: Patlak, Logan, 1-tissue compartment model, 2-tissue compartment model, and first pass blood flow. After uploading the 4D-PET DICOM series into Osirix, the image processing requires very few steps: the choice of the kinetic model and the definition of an input function. After a 2-min process, the PET parametric and error maps of the chosen model are automatically estimated voxel-wise and written in DICOM format. The software benefits from the graphical user interface of Osirix, making it user-friendly. Compared to PMOD-PKIN (version 4.4) on twelve 18F-FDG PET dynamic datasets, PET KinetiX provided an absolute bias of 0.1% (0.05-0.25) and 5.8% (3.3-12.3) for KiPatlak and Ki2TCM, respectively. Several clinical research illustrative cases acquired on different hybrid PET systems (standard or extended axial fields of view, PET/CT, and PET/MRI), with different acquisition schemes (single-bed single-pass or multi-bed multipass), are also provided. PET KinetiX is a very fast and efficient independent research software that helps molecular imaging users easily and quickly produce 3D PET parametric images from any reconstructed 4D-PET data acquired on standard or large PET systems.

A systematic review for the evidence of recommendations and guidelines in hybrid nuclear cardiovascular imaging

OBJECTIVES

This study aimed to evaluate the level of evidence of expert recommendations and guidelines for clinical indications and procedurals in hybrid nuclear cardiovascular imaging.

METHODS

From inception to August 2023, a PubMed literature analysis of the latest version of guidelines for clinical hybrid cardiovascular imaging techniques including SPECT(/CT), PET(/CT), and PET(/MRI) was performed in two categories: (1) for clinical indications for all-in primary diagnosis; subgroup in prognosis and therapy evaluation; and for (2) imaging procedurals. We surveyed to what degree these followed a standard methodology to collect the data and provide levels of evidence, and for which topic systematic review evidence was executed.

RESULTS

A total of 76 guidelines, published between 2013 and 2023, were included. The evidence of guidelines was based on systematic reviews in 7.9% of cases, non-systematic reviews in 47.4% of cases, a mix of systematic and non-systematic reviews in 19.7%, and 25% of guidelines did not report any evidence. Search strategy was reported in 36.8% of cases. Strengths of recommendation were clearly reported in 25% of guidelines. The notion of external review was explicitly reported in 23.7% of cases. Finally, the support of a methodologist was reported in 11.8% of the included guidelines.

CONCLUSION

The use of evidence procedures for developing for evidence-based cardiovascular hybrid imaging recommendations and guidelines is currently suboptimal, highlighting the need for more standardized methodological procedures.

PET FDG CT is useful for giant-cell arteritis with isolated cough

Giant cell arteritis (GCA) is a chronic vasculitis of large- and medium-sized vessels. The most frequent symptoms are temporal headaches, scalp tenderness, jaw claudication and polymyalgia rheumatica in 35% of patients. Atypical presentation with dry cough is very rare and could be isolated making the diagnosis difficult. Initial imaging including PET-CT could be helpful. Literature review yielded 13 case reports with available data and one case series which focused on cough and which were all be included in this study. Most of the cases included males (n = 8), with mostly isolated cough or associated to fever and weight loss. Angio-CT of aortic wall was mostly normal, whereas FDG PET-CT showed in all available cases abnormal arterial thoracic uptake. Temporal artery biopsy was almost suggestive of GCA in all available cases. Cough was steroid responsive usually within few days in all cases without any need of combined therapy. Giant cell arteritis is the most common large-vessel vasculitis over the age of 50 in western countries. Isolated dry cough is extremely rare and encountered in less than 5% of cases.

[18F]FDG-PET/CT in Polymyalgia Rheumatica: An Update and Future Aspects

Polymyalgia rheumatica (PMR) is an inflammatory disorder usually diagnosed in patients older than 50 years of age. It is characterized by sudden onset pain and prolonged morning stiffness in the scapular and/or pelvic girdle, sometimes debilitating and accompanied by constitutional symptoms such as weight loss. In approximately 20% of the cases, it is linked to giant cell arteritis (GCAV) representing a disease continuum. The diagnosis is mainly clinical and noninvasive imaging such as ultrasound of joints may be helpful. In atypical PMR cases, whole body imaging using [18F]FDG-PET/CT may be useful. First, to confirm or rule out the diagnosis of PMR, secondly, to assess the coexistence of a GCA, and thirdly to establish the differential diagnosis with other types of arthritides encountered in this age group, such as elderly-onset rheumatoid arthritis, spondyloarthropathies, crystal-induced arthropathies or the rare remittent seronegative symmetrical synovitis with pitting edema. Relatively typical patterns of [18F]FDG-PET/CT are well known, based on the clinical distribution of the disease (eg, scapular and pelvic girdle, interspinous bursae, sterno-costoclavicular joints, entheses), especially the hypermetabolism at the interspinous lumbar bursae that has shown the best post-test likelihood ratio in a meta-analysis. This article focuses on the differential diagnosis and on the visual and semi-quantitative tools that can be used to guide to the correct diagnosis of PMR as an add-on to the clinical picture. Further, we briefly discuss the options that can improve molecular imaging in the future for inflammatory rheumatisms in elderly.

PET/CT in Inflammatory and Auto-immune Disorders: Focus on Several Key Molecular Concepts, FDG, and Radiolabeled Probe Perspectives

Chronic immune diseases mainly include autoimmune and inflammatory diseases. Managing chronic inflammatory and autoimmune diseases has become a significant public health concern, and therapeutic advancements over the past 50 years have been substantial. As therapeutic tools continue to multiply, the challenge now lies in providing each patient with personalized care tailored to the specifics of their condition, ushering in the era of personalized medicine. Precise and holistic imaging is essential in this context to comprehensively map the inflammatory processes in each patient, identify prognostic factors, and monitor treatment responses and complications. Imaging of patients with inflammatory and autoimmune diseases must provide a comprehensive view of the body, enabling the whole-body mapping of systemic involvement. It should identify key cellular players in the pathology, involving both innate immunity (dendritic cells, macrophages), adaptive immunity (lymphocytes), and microenvironmental cells (stromal cells, tissue cells). As a highly sensitive imaging tool with vectorized molecular probe capabilities, PET/CT can be of high relevance in the management of numerous inflammatory and autoimmune diseases. Relying on key molecular concepts of immunity, the clinical usefulness of FDG-PET/CT in several relevant inflammatory and immune-inflammatory conditions, validated or emerging, will be discussed in this review, together with radiolabeled probe perspectives.

[18F]DPA-714 PET Imaging in the Presurgical Evaluation of Patients With Drug-Resistant Focal Epilepsy

BACKGROUND AND OBJECTIVES

Translocator protein 18 kDa (TSPO) PET imaging is used to monitor glial activation. Recent studies have proposed TSPO PET as a marker of the epileptogenic zone (EZ) in drug-resistant focal epilepsy (DRFE). This study aims to assess the contributions of TSPO imaging using [18F]DPA-714 PET and [18F]FDG PET for localizing the EZ during presurgical assessment of DRFE, when phase 1 presurgical assessment does not provide enough information.

METHODS

We compared [18F]FDG and [18F]DPA-714 PET images of 23 patients who had undergone a phase 1 presurgical assessment, using qualitative visual analysis and quantitative analysis, at both the voxel and the regional levels. PET abnormalities (increase in binding for [18F]DPA-714 vs decrease in binding for [18F]FDG) were compared with clinical hypotheses concerning the localization of the EZ based on phase 1 presurgical assessment. The additional value of [18F]DPA-714 PET imaging to [18F]FDG for refining the localization of the EZ was assessed. To strengthen the visual analysis, [18F]DPA-714 PET imaging was also reviewed by 2 experienced clinicians blind to the EZ location.

RESULTS

The study included 23 patients. Visual analysis of [18F]DPA-714 PET was significantly more accurate than [18F]FDG PET to both, show anomalies (95.7% vs 56.5%, p = 0.022), and provide additional information to refine the EZ localization (65.2% vs 17.4%, p = 0.019). All 10 patients with normal [18F]FDG PET had anomalies when using [18F]DPA-714 PET. The additional value of [18F]DPA-714 PET seemed to be greater in patients with normal brain MRI or with neocortical EZ (especially if insula is involved). Regional analysis of [18F]DPA-714 and [18F]FDG PET provided similar results. However, using voxel-wise analysis, [18F]DPA-714 was more effective than [18F]FDG for unveiling clusters whose localization was more often consistent with the EZ hypothesis (87.0% vs 39.1%, p = 0.019). Nonrelevant bindings were seen in 14 of 23 patients in visual analysis and 9 patients of 23 patients in voxel-wise analysis.

DISCUSSION

[18F]DPA-714 PET imaging provides valuable information for presurgical assessments of patients with DRFE. TSPO PET could become an additional tool to help to the localization of the EZ, especially in patients with negative [18F]FDG PET.

TRIAL REGISTRATION INFORMATION

Eudract 2017-003381-27. Inclusion of the first patient: September 24, 2018.

CLASSIFICATION OF EVIDENCE

This study provides Class IV evidence on the utility of [18F]DPA-714 PET compared with [18F]FDG PET in identifying the epileptic zone in patients undergoing phase 1 presurgical evaluation for intractable epilepsy.

Towards refining the utility of dual (18F-FDG / 18F-Choline) PET/CT for the management of hepatocellular carcinoma: a tertiary center study

BACKGROUND

The role of positron emission tomography/computed tomography (PET/CT) in hepatocellular carcinoma (HCC) management is not clearly defined. Our objective was to analyze the utility of dual-PET/CT (18F-FDG + 18F-Choline) imaging findings on the BCLC staging and treatment decision for HCC patients.

METHODS

Between January 2011 and April 2019, 168 consecutive HCC patients with available baseline dual-PET/CT imaging data were retrospectively analyzed. To identify potential refinement criteria for surgically-treated patients, survival Kaplan-Meier curves of various standard-of-care and dual-PET/CT baseline parameters were estimated. Finally, multivariate cox proportional hazard ratios of the most relevant clinico-biological and/or PET parameters were estimated.

RESULTS

Dual-PET/CT findings increased the score of BCLC staging in 21 (12.5%) cases. In 24.4% (N.=41) of patients, the treatment strategy was modified by the PET findings. Combining AFP levels at a threshold of 10 ng/mL with 18F-FDG or 18F-Choline N status significantly impacted DFS (P<0.05). In particular, the combined criteria of the N+ status assessed by 18F-Choline with AFP threshold of 10 ng/mL provided a highly predictive composite parameter for estimation of DFS according to multivariate analysis (HR=10.6, P<0.05).

CONCLUSIONS

The 18F-Choline / AFP composite parameter appears promising, and further prospective studies are mandatory to validate its oncological impact.

Is 18 F-FDG/ 18 F-Choline Dual-Tracer PET Behavior a Surrogate of Tumor Differentiation in Hepatocellular Carcinoma : A Tertiary Center Dedicated Study

BACKGROUND

In hepatocellular carcinoma (HCC) setting, 18 F-FDG and 18 F-choline PET/CT radiotracers are classically considered surrogates of the degree of differentiation, a strong predictor of disease recurrence after curative treatment. Because the corresponding level of evidence has never been assessed as primary end point, the aim of this retrospective study was to specifically assess the relevance of 18 F-FDG combined to 18 F-choline PET imaging as a surrogate of tumor differentiation in HCC.

PATIENTS AND METHODS

A total of 49 histologically proven HCCs (46 patients treated by surgery or liver transplantation) with available baseline 18 F-FDG and 18 F-choline PET/CT, dedicated liver contrast-enhanced CT scan, and histological key features were retrospectively reviewed. Hepatocellular carcinoma tumors with well, moderately, and poorly differentiation (grades I, II, and III of the World Health Organization classification) were compared on their PET findings (double-blinded visual analysis and 8 usual semiquantitative metrics) by using nonparametric Kruskal-Wallis analyses of variance. In the case of statistical significance, pairwise post hoc tests with family-wise error rate adjustment were performed.

RESULTS

No statistical difference between the grades was observed for any of the patients' or lesions' characteristics ( P > 0.05), except for the macrovascular invasion between the grades I and II (adjusted P = 0.03). None of the PET findings showed statistical difference between the grades, except the tumor-to-background ratio of 18 F-FDG, higher for the grade III compared with grades I (adjusted P = 0.02) and II (adjusted P = 0.01). For less than one third of cases (14 lesions; 28.5%), the regional uptake was judged visually heterogeneous, but none of the related semiquantitative PET metrics were statistically discriminant ( P > 0.05).

CONCLUSIONS

Contrary to a common belief, 18 F-FDG/ 18 F-choline dual-tracer PET behavior is not a relevant surrogate of tumor differentiation in HCC. Future multitracer PET studies are mandatory to refine our knowledges of their deep biological meaning in this field.

Relevance of 18F-DOPA visual and semi-quantitative PET metrics for the diagnostic of Parkinson disease in clinical practice: a machine learning-based inference study

PURPOSE

To decipher the relevance of visual and semi-quantitative 6-fluoro-(18F)-L-DOPA (¹⁸F-DOPA) interpretation methods for the diagnostic of idiopathic Parkinson disease (IPD) in hybrid positron emission tomography (PET) and magnetic resonance imaging.

MATERIAL AND METHODS

A total of 110 consecutive patients (48 IPD and 62 controls) with 11 months of median clinical follow-up (reference standard) were included. A composite visual assessment from five independent nuclear imaging readers, together with striatal standard uptake value (SUV) to occipital SUV ratio, striatal gradients and putamen asymmetry-based semi-quantitative PET metrics automatically extracted used to train machine learning models to classify IPD versus controls. Using a ratio of 70/30 for training and testing sets, respectively, five classification models-k-NN, LogRegression, support vector machine, random forest and gradient boosting-were trained by using 100 times repeated nested cross-validation procedures. From the best model on average, the contribution of PET parameters was deciphered using the Shapley additive explanations method (SHAP). Cross-validated receiver operating characteristic curves (cv-ROC) of the most contributive PET parameters were finally estimated and compared.

RESULTS

The best machine learning model (k-NN) provided final cv-ROC of 0.81. According to SHAP analyses, visual PET metric was the most important contributor to the model overall performance, followed by the minimum between left and right striatal to occipital SUV ratio. The 10-time cv-ROC curves of visual, min SUVr or both showed quite similar performance (mean area under the ROC of 0.81, 0.81 and 0.79, respectively, for visual, min SUVr or both).

CONCLUSION

Visual expert analysis remains the most relevant parameter to predict IPD diagnosis at 11 months of median clinical follow-up in ¹⁸F-FDOPA. The min SUV ratio appears interesting in the perspective of simple semi-automated diagnostic workflows.

Influence of key histological characteristics on 18F-fluorodeoxyglucose /18F-choline positron emission tomography positivity in hepatocellular carcinoma: A machine learning study

Purpose

To determine the characteristics influence of key histological on 18F-fluorodeoxyglucose (18F-FDG) and 18F-choline positron emission tomography (PET) positivity in hepatocellular carcinoma (HCC).

Materials and methods

The 18F-FDG/18F-choline PET imaging findings of 103 histologically proven HCCs (from 62 patients, of which 47 underwent hepatectomy and 15 received liver transplantation) were retrospectively examined to assess the following key histological parameters: Grade, capsule, microvascular invasion (mVI), macrovascular invasion (MVI), and necrosis. Using a ratio of 70/30 for training and testing sets, respectively, a penalized classification model (Elastic Net) was trained using 100 repeated cross-validation procedures (10-fold cross-validation for hyperparameter optimization). The contribution of each histological parameter to the PET positivity was determined using the Shapley Additive Explanations method. Receiver operating characteristic curves with and without dimensionality reduction were finally estimated and compared.

Results

Among the five key histological characteristics of HCC (Grade, capsule, mVI, MVI, and necrosis), mVI and tumor Grade (I-III) showed the highest relevance and robustness in explaining HCC uptake of 18F-FDG and 18F-choline. MVI and necrosis status both showed high instability in outcome predictions. Tumor capsule had a minimal influence on the model predictions. On retaining only mVI and Grades I-III for the final analysis, the area under the receiver operating characteristic (ROC) curve values were maintained (0.68 vs. 0.63, 0.65 vs. 0.64, and 0.65 vs. 0.64 for 18F-FDG, 18F-choline, and their combination, respectively).

Conclusion

18F-FDG/18F-choline PET positivity appears driven by both the Grade and mVI components in HCC. Consideration of the tumor microenvironment will likely be necessary to improve our understanding of multitracer PET positivity.

Isotopic Radiolabeling of Crizotinib with Fluorine-18 for In Vivo Pet Imaging

Crizotinib is a tyrosine kinase inhibitor approved for the treatment of non-small-cell lung cancer, but it is inefficient on brain metastases. Crizotinib is a substrate of the P-glycoprotein, and non-invasive nuclear imaging can be used to assess the brain penetration of crizotinib. Positron emission tomography (PET) imaging using fluorine-18-labeled crizotinib would be a powerful tool for investigating new strategies to enhance the brain distribution of crizotinib. We have synthesized a spirocyclic hypervalent iodine precursor for the isotopic labeling of crizotinib in a 2.4% yield. Because crizotinib is an enantiomerically pure drug, a chiral separation was performed to afford the (R)-precursor. A two-step radiolabeling process was optimized and automated using the racemic precursor to afford [18F](R,S)-crizotinib in 15 ± 2 radiochemical yield and 103 ± 18 GBq/µmol molar activity. The same radiolabeling process was applied to the (R)-precursor to afford [18F](R)-crizotinib with comparable results. As a proof-of-concept, PET was realized in a single non-human primate to demonstrate the feasibility of [18F](R)-crizotinib in in vivo imaging. Whole-body PET highlighted the elimination routes of crizotinib with negligible penetration in the brain (SUVmean = 0.1). This proof-of-concept paves the way for further studies using [18F](R)-crizotinib to enhance its brain penetration depending on the P-glycoprotein function.

18F-FDG PET molecular imaging: A relevant tool to investigate chronic inflammatory rheumatisms in clinical practice?

18F-Labeled Fluorodeoxyglucose-Positron Emission Tomography (18F-FDG PET) is a molecular imaging tool commonly used in practice for the assessment of many cancers. Thanks to its properties, its use has been progressively extended to numerous inflammatory conditions, including chronic inflammatory rheumatism (CIR) such as rheumatoid arthritis (RA), spondylarthritis (SpAs) and polymyalgia rheumatica (PMR). 18F-FDG PET is currently not recommended for the diagnostic of CIRs. However, this whole-body imaging tool has emerged in clinical practice, providing a general overview of systemic involvement occurring in CIRs. Numerous studies have highlighted the capacity of 18F-FDG PET to detect articular and extra articular involvements in RA and PMR. However, the lack of specificity of 18F-FDG limits its use for diagnosis purpose. Finally, the key question is the definition of the best way to integrate this whole-body imaging tool in the patient's management workflow.

18F-FDG /18F-Choline Dual-Tracer PET Behavior and Tumor Differentiation in HepatoCellular Carcinoma. A Systematic Review

Background

Post-operative recurrence remains the strongest prognostic factor of resected hepatocellular carcinoma (HCC), making the accurate selection of patients with curable HCC a crucial issue. PET imaging combining both 18F-FDG and fatty acid synthase (FAS) radiotracers—such as Choline—has shown its interest for the initial staging and therapeutic management of patients with HCC, but its use is still not consensual. Importantly, the very first dual-tracer PET studies suggested 18F-FDG/FAS PET behavior be linked to the degree of differentiation of HCC, a major predictive factor of post-operative recurrence. Although this key molecular imaging concept may impact how dual-tracer PET will be used in early-stage HCC, its level of evidence remains largely unexplored. In this study, we conducted a systematic review of the available evidence-based data to clarify the relevance of dual 18F-FDG/18F-Choline PET in characterizing the degree of differentiation of HCC tumors.

Methods

A systematic search of the PubMed/Medline and Embase databases was performed up to November 2021. A systematic review of the dual-tracer 18F-FDG/18F-Choline PET behavior of histology-proven HCC according to their degree of differentiation was conducted. The overall quality of the included studies was critically assessed based on the STROBE guidelines. Information on study date, design, patient cohort characteristics, grade of differentiation of HCC tumors, and the dual-tracer PET behavior per HCC was independently extracted and summarized.

Results

From 440 records initially available, 6 full-text articles (99 histology-proven HCC) provided dual-tracer 18F-FDG/18F-Choline PET behavior per HCC tumor grade were included in the systematic review. Based on our analysis, 43/99 HCCs were reported to be well-differentiated, and 56/99 HCCs were reported to be less-differentiated tumors. In the well-differentiated subgroup, more than half were exclusively positive for 18F-Choline (51%), whereas 39% were positive for both 18F-FDG and 18F-Choline. In the less-differentiated subgroup, 37% of HCC patients were positive exclusively for FDG, 36% were positive for both 18F-FDG and 18F-Choline, and 25% were positive exclusively for 18F-Choline.

Conclusion

The 18F-FDG/18F-Choline dual-tracer PET behavior of uptake shows high overlap between well- and less differentiated HCC, making the characterization of tumors challenging based on such PET combination alone. Given our growing knowledge of the molecular complexity of HCC, further studies are necessary to refine our understanding of radiotracers’ behavior in this field and improve the usefulness of PET imaging in the clinical decision process of HCC.

Features of non-Hodgkin’s lymphoma diagnosed in minor salivary gland biopsies from primary Sjögren’s syndrome patients

Objective

To evaluate the contribution of minor salivary gland biopsy (mSGB) histology to diagnosing primary Sjögren’s syndrome (pSS)-associated non-Hodgkin B cell lymphoma (NHL).

Methods

pSS patients with mSGB at NHL diagnosis were included.

Results

Among the 24 patients (92.3% female; mean age: 61.3 years) with an mSGB at NHL diagnosis, 13 (54.2%) had mSGB-histology–revealed NHL (mSGB+); it was the only site enabling NHL diagnosis in 10/13 (76.9%) patients. Mucosa-associated lymphoid tissue (MALT) lymphoma was found in 23/24 (95.8%) patients; 100% of mSGB+ identified MALT lymphomas. pSS and lymphoma characteristics were comparable for mSGB+ and mSGB– patients. Eight (61.5%) of the 13 mSGB+ patients and all 11 mSGB– patients were treated for lymphoma. Between diagnosis and 1 year of follow-up, ESSDAI without the NHL item remained stable (7.4 vs 5.0; p = 0.33) for the five untreated patients, while it decreased significantly for the 19 treated patients (15.8 vs 5.1; p = 0.004).

Conclusion

For pSS patients with suspected NHL, mSGB histology enabled NHL diagnosis in half of them, MALT was found in 95.8% and all mSGBs+ were MALT lymphomas, thereby avoiding more invasive biopsy. Our results suggest that mSGB should be obtained at pSS diagnosis and repeated during follow-up, when NHL is suspected.

Use of 18F FDG PET-CT to discriminate polymyalgia rheumatica and atypical spondylarthritis in clinical practice

OBJECTIVE

To evaluate the relevance of ¹⁸F-labeled fluorodeoxyglucose-positron emission tomography/computed tomography (¹⁸F-FDG PET-CT) for discriminating polymyalgia rheumatica (PMR) and spondylarthritis (SpA) in atypical presentations.

METHODS

In 2 rheumatology departments, we identified PMR and atypical SpA patients who underwent ¹⁸F-FDG PET-CT and compared the 2 groups. The relevant ¹⁸F-FDG PET-CT findings identified on univariate analyses as discriminant for both groups were entered into a multivariable logistic regression model to derive a composite musculoskeletal score.

RESULTS

Between September 2012 and August 2018, we enrolled 35 PMR and 27 SpA patients (median [interquartile range] age 71 years [63.5-74.5] and 54 years [41.5-63], p < 0.001). ¹⁸F-FDG uptake in enthesis/bursae was more frequent in PMR than SpA (ischial tuberosities: 88.6% vs 48.1%, p < 0.001; interspinous processes: 91.4% vs 51.9%, p < 0.001). ¹⁸F-FDG uptake in sacroiliac joints was specific to SpA but rare (14.8% vs 0 in PMR, p < 0.05). The intensity of ¹⁸F-FDG uptake was similar in both conditions. The musculoskeletal score, including ¹⁸F-FDG uptake of the shoulders, ischial tuberosities and interspinous process, was higher for PMR than SpA patients (2.74 vs 1.11, p < 0.001). A score ≥ 2 provided sensitivity and specificity of 74.1% and 77.1% for the diagnosis of PMR.

CONCLUSION

¹⁸F-FDG PET-CT patterns of atypical SpA and PMR widely overlap, so differentiating the conditions is challenging. The use of the proposed PET-CT composite score could improve the diagnostic performance of ¹⁸F-FDG PET-CT to discriminate these 2 entities in clinical practice.

Fully Integrated Quantitative Multiparametric Analysis of Non-Small Cell Lung Cancer at 3-T PET/MRI: Toward One-Stop-Shop Tumor Biological Characterization at the Supervoxel Level

INTRODUCTION

The aim of this study was to study the feasibility of a fully integrated multiparametric imaging framework to characterize non-small cell lung cancer (NSCLC) at 3-T PET/MRI.

PATIENTS AND METHODS

An 18F-FDG PET/MRI multiparametric imaging framework was developed and prospectively applied to 11 biopsy-proven NSCLC patients. For each tumor, 12 parametric maps were generated, including PET full kinetic modeling, apparent diffusion coefficient, T1/T2 relaxation times, and DCE full kinetic modeling. Gaussian mixture model-based clustering was applied at the whole data set level to define supervoxels of similar multidimensional PET/MRI behaviors. Taking the multidimensional voxel behaviors as input and the supervoxel class as output, machine learning procedure was finally trained and validated voxelwise to reveal the dominant PET/MRI characteristics of these supervoxels at the whole data set and individual tumor levels.

RESULTS

The Gaussian mixture model-based clustering clustering applied at the whole data set level (17,316 voxels) found 3 main multidimensional behaviors underpinned by the 12 PET/MRI quantitative parameters. Four dominant PET/MRI parameters of clinical relevance (PET: k2, k3 and DCE: ve, vp) predicted the overall supervoxel behavior with 97% of accuracy (SD, 0.7; 10-fold cross-validation). At the individual tumor level, these dimensionality-reduced supervoxel maps showed mean discrepancy of 16.7% compared with the original ones.

CONCLUSIONS

One-stop-shop PET/MRI multiparametric quantitative analysis of NSCLC is clinically feasible. Both PET and MRI parameters are useful to characterize the behavior of tumors at the supervoxel level. In the era of precision medicine, the full capabilities of PET/MRI would give further insight of the characterization of NSCLC behavior, opening new avenues toward image-based personalized medicine in this field.

Denosumab in active Charcot neuro-osteoarthropathy of the foot

OBJECTIVE

Active Charcot Neuro-osteoarthropathy (CN) is a rare and severe complication of peripheral neuropathy that leads to deformity and disability. No pharmacological treatment is available. Increased osteoclastic activity plays a central role in active CN, particularly via receptor activator of nuclear factor ligand (RANK-L). We aimed to describe clinical, morphological and metabolic imaging effects of denosumab, a fully human monoclonal anti- RANK-L antibody, in active CN.

METHODS

In this open-label study, we included all consecutive patients with active refractory CN treated with denosumab in our tertiary center. Baseline and follow-up assessment included clinical examination, biological and imaging procedures (morphological and metabolic) before and after treatment.

RESULTS

Seven patients were treated with denosumab between 2017 and 2020 and followed for a median of 16 months [6-39]. All patients clinically improved, 4 further relapsed after a median of 4 months [3-33]. Four patients were retreated with the same efficacy. Imaging follow-up available in 5 patients showed stability of structural damage (radiography) and a significant decrease of metabolic activity (FDG PET-CT) in 4 of them. No adverse event or hypocalcemia was observed.

CONCLUSION

In patients with refractory active CN, denosumab had a clinical effect, prevented bone and joint destruction, together with a metabolic effect, as assessed by FDG PET-CT. These results justify the conduction of a randomized controlled trial to assess the efficacy of denosumab in acute CN.

PET Molecular Imaging: A Holistic Review of Current Practice and Emerging Perspectives for Diagnosis, Therapeutic Evaluation and Prognosis in Clinical Oncology

PET/CT molecular imaging has been imposed in clinical oncological practice over the past 20 years, driven by its two well-grounded foundations: quantification and radiolabeled molecular probe vectorization. From basic visual interpretation to more sophisticated full kinetic modeling, PET technology provides a unique opportunity to characterize various biological processes with different levels of analysis. In clinical practice, many efforts have been made during the last two decades to standardize image analyses at the international level, but advanced metrics are still under use in practice. In parallel, the integration of PET imaging with radionuclide therapy, also known as radiolabeled theranostics, has paved the way towards highly sensitive radionuclide-based precision medicine, with major breakthroughs emerging in neuroendocrine tumors and prostate cancer. PET imaging of tumor immunity and beyond is also emerging, emphasizing the unique capabilities of PET molecular imaging to constantly adapt to emerging oncological challenges. However, these new horizons face the growing complexity of multidimensional data. In the era of precision medicine, statistical and computer sciences are currently revolutionizing image-based decision making, paving the way for more holistic cancer molecular imaging analyses at the whole-body level.

AZTEK: Adaptive zero TE k-space trajectories

PURPOSE

Because of short signal lifetimes and respiratory motion, 3D lung MRI is still challenging today. Zero-TE (ZTE) pulse sequences offer promising solutions as they overcome the issue of short T 2 ∗ . Nevertheless, as they rely on continuous readout gradients, the trajectories they follow in k-space are not adapted to retrospective gating and inferred motion correction.

THEORY AND METHODS

We propose AZTEK (adaptive ZTE k-space trajectories), a set of 3D radial trajectories featuring three tuning parameters, to adapt the acquisition to any moving organ while keeping seamless transitions between consecutive spokes. Standard ZTE and AZTEK trajectories were compared for static and moving phantom acquisitions as well as for human thoracic imaging performed on 3 volunteers (1 healthy and 2 patients with lung cancer).

RESULTS

For the static phantom, we observe comparable image qualities with standard and AZTEK trajectories. For the moving phantom, spatially coherent undersampling artifacts observed on gated images with the standard trajectory are alleviated with AZTEK. The same improvement in image quality is obtained in human, so details are more delineated in the lung with the use of the adaptive trajectory.

CONCLUSION

The AZTEK technique opens the possibility for 3D dynamic ZTE lung imaging with retrospective gating. It enables us to uniformly sample the k-space for any arbitrary respiratory motion gate, while preserving static image quality, improving dynamic image quality and guaranteeing continuous readout gradient transitions between spokes, which makes it appropriate to ZTE.

18F-FDG PET and DCE kinetic modeling and their correlations in primary NSCLC: first voxel-wise correlative analysis of human simultaneous [18F]FDG PET-MRI data

OBJECTIVES

To decipher the correlations between PET and DCE kinetic parameters in non-small-cell lung cancer (NSCLC), by using voxel-wise analysis of dynamic simultaneous [18F]FDG PET-MRI.

MATERIAL AND METHODS

Fourteen treatment-naïve patients with biopsy-proven NSCLC prospectively underwent a 1-h dynamic [18F]FDG thoracic PET-MRI scan including DCE. The PET and DCE data were normalized to their corresponding T1-weighted MR morphological space, and tumors were masked semi-automatically. Voxel-wise parametric maps of PET and DCE kinetic parameters were computed by fitting the dynamic PET and DCE tumor data to the Sokoloff and Extended Tofts models respectively, by using in-house developed procedures. Curve-fitting errors were assessed by computing the relative root mean square error (rRMSE) of the estimated PET and DCE signals at the voxel level. For each tumor, Spearman correlation coefficients (rs) between all the pairs of PET and DCE kinetic parameters were estimated on a voxel-wise basis, along with their respective bootstrapped 95% confidence intervals (n = 1000 iterations).

RESULTS

Curve-fitting metrics provided fit errors under 20% for almost 90% of the PET voxels (median rRMSE = 10.3, interquartile ranges IQR = 8.1; 14.3), whereas 73.3% of the DCE voxels showed fit errors under 45% (median rRMSE = 31.8%, IQR = 22.4; 46.6). The PET-PET, DCE-DCE, and PET-DCE voxel-wise correlations varied according to individual tumor behaviors. Beyond this wide variability, the PET-PET and DCE-DCE correlations were mainly high (absolute rs values > 0.7), whereas the PET-DCE correlations were mainly low to moderate (absolute rs values < 0.7). Half the tumors showed a hypometabolism with low perfused/vascularized profile, a hallmark of hypoxia, and tumor aggressiveness.

CONCLUSION

A dynamic "one-stop shop" procedure applied to NSCLC is technically feasible in clinical practice. PET and DCE kinetic parameters assessed simultaneously are not highly correlated in NSCLC, and these correlations showed a wide variability among tumors and patients. These results tend to suggest that PET and DCE kinetic parameters might provide complementary information. In the future, this might make PET-MRI a unique tool to characterize the individual tumor biological behavior in NSCLC.

Diffusion-weighted Imaging Voxelwise-matched Analyses of Lung Cancer at 3.0-T PET/MRI: Reverse Phase Encoding Approach for Echo-planar Imaging Distortion Correction

Background PET/MRI has drawn increasing interest in thoracic oncology due to the simultaneous acquisition of PET and MRI data. Geometric distortions related to diffusion-weighted imaging (DWI) limit the evaluation of voxelwise multimodal analyses. Purpose To assess the effectiveness of reverse phase encoding in correcting DWI geometric distortion for multimodal PET/MRI voxelwise lung tumor analyses. Materials and Methods In this prospective study, reverse phase encoding method was implemented with 3.0-T PET/MRI to correct geometric distortions related to DWI. The method was validated in dedicated phantom and then applied to 12 consecutive patients (mean age, 66 years ± 13 [standard deviation]; 10 men) suspected of having lung cancer who underwent fluorodeoxyglucose PET/MRI between October 2018 and April 2019. The effects on DWI-related image matching and apparent diffusion coefficient (ADC) regional map computation were assessed. Consequences on multimodal PET/MRI voxelwise lung tumor analyses were evaluated. Spearman correlation coefficients (r_s) between the standardized uptake value (SUV) and ADC data corrected for distortion were computed from optimal realigned DWI PET data, along with bootstrap confidence intervals. Results Phantom results showed that in highly distorted areas, correcting the distortion significantly reduced the mean error against the ground truth (-25% ± 10.6 to -18.4% ± 12.6; P < .001) and the number of voxels with more than 20% error (from 85.3% to 31.4%). In the 12 patients, the coregistration of multimodal PET/MRI tumor data was improved by using the reverse phase encoding method (0.4%-44%). In all tumors, voxelwise correlations (r_s) between ADC and SUV revealed null or weak monotonic relationships (mean r_s of 0.016 ± 0.24 with none above 0.5). Conclusion Reverse phase encoding is a simple-to-implement method for improved diffusion-weighted multimodal PET/MRI voxelwise-matched analyses in lung cancer. © RSNA, 2020 Online supplemental material is available for this article. See also the editorial by Colletti in this issue.

Imaging-guided precision medicine in glioblastoma patients treated with immune checkpoint modulators: research trend and future directions in the field of imaging biomarkers and artificial intelligence

Immunotherapies that employ immune checkpoint modulators (ICMs) have emerged as an effective treatment for a variety of solid cancers, as well as a paradigm shift in the treatment of cancers. Despite this breakthrough, the median survival time of glioblastoma patients has remained at about 2 years. Therefore, the safety and anti-cancer efficacy of combination therapies that include ICMs are being actively investigated. Because of the distinct mechanisms of ICMs, which restore the immune system’s anti-tumor capacity, unconventional immune-related phenomena are increasingly being reported in terms of tumor response and progression, as well as adverse events. Indeed, immunotherapy response assessments for neuro-oncology (iRANO) play a central role in guiding cancer patient management and define a “wait and see strategy” for patients treated with ICMs in monotherapy with progressive disease on MRI. This article deciphers emerging research trends to ameliorate four challenges unaddressed by the iRANO criteria: (1) patient selection, (2) identification of immune-related phenomena other than pseudoprogression (i.e., hyperprogression, the abscopal effect, immune-related adverse events), (3) response assessment in combination therapies including ICM, and (4) alternatives to MRI. To this end, our article provides a structured approach for standardized selection and reporting of imaging modalities to enable the use of precision medicine by deciphering the characteristics of the tumor and its immune environment. Emerging preclinical or clinical innovations are also discussed as future directions such as immune-specific targeting and implementation of artificial intelligence algorithms.

EULAR recommendations for the use of imaging in large vessel vasculitis in clinical practice

To develop evidence-based recommendations for the use of imaging modalities in primary large vessel vasculitis (LVV) including giant cell arteritis (GCA) and Takayasu arteritis (TAK). European League Against Rheumatism (EULAR) standardised operating procedures were followed. A systematic literature review was conducted to retrieve data on the role of imaging modalities including ultrasound, MRI, CT and [18F]-fluorodeoxyglucose positron emission tomography (PET) in LVV. Based on evidence and expert opinion, the task force consisting of 20 physicians, healthcare professionals and patients from 10 EULAR countries developed recommendations, with consensus obtained through voting. The final level of agreement was voted anonymously. A total of 12 recommendations have been formulated. The task force recommends an early imaging test in patients with suspected LVV, with ultrasound and MRI being the first choices in GCA and TAK, respectively. CT or PET may be used alternatively. In case the diagnosis is still in question after clinical examination and imaging, additional investigations including temporal artery biopsy and/or additional imaging are required. In patients with a suspected flare, imaging might help to better assess disease activity. The frequency and choice of imaging modalities for long-term monitoring of structural damage remains an individual decision; close monitoring for aortic aneurysms should be conducted in patients at risk for this complication. All imaging should be performed by a trained specialist using appropriate operational procedures and settings. These are the first EULAR recommendations providing up-to-date guidance for the role of imaging in the diagnosis and monitoring of patients with (suspected) LVV.

Effect of CRP value on 18F-FDG PET vascular positivity in Takayasu arteritis: a systematic review and per-patient based meta-analysis

PURPOSE

The aim of this study was to quantify the association between the CRP value and ¹⁸F-FDG PET vascular positivity in Takayasu arteritis (TAK) through a structured dedicated systematic review and meta-analysis.

METHODS

From January 2000 to December 2016, the PubMed/MEDLINE database was searched for articles specifically dealing with the assessment of vascular inflammation using ¹⁸F-FDG PET and CRP biomarkers in TAK. Inclusion criteria for the qualitative analysis were (1) ¹⁸F-FDG PET used to assess the disease activity, (2) The use of the ACR criteria for the diagnosis of TAK, (3) No case mixed vasculitis (i.e., no giant cell arteritis), and (4) CRP concentration and clinical disease activity available. For the meta-analysis, PET-positive and PET-negative subgroups with the corresponding CRP concentrations were generated based on per patient data. The standard mean difference, which represents the effect of the CRP concentrations on the ¹⁸F-FDG PET vascular uptake, was computed for all studies, and then the results were pooled together.

RESULTS

Among the 33 initial citations, nine complete articles including 210 patients fulfilled the inclusion criteria. Five studies found a significant correlation between the ¹⁸F-FDG PET and CRP concentration, one provided a trend towards association and three did not find any association between the two biomarkers. Six studies found a significant association between ¹⁸F-FDG PET and clinical disease activity, one found a trend towards association and the last two studies did not evaluate this correlation. The meta-analysis (121 patients) provided the following results: Standard Mean Deviation = 0.54 [0.15;0.92]; Chi² = 3.35; I² = 0%; Test for overall effect: Z = 2.70 (P = 0.007).

CONCLUSION

The CRP concentration only moderately reflects the ¹⁸F-FDG PET vascular positivity in TAK, suggesting dissociated information. Standardized longitudinal prospective studies are necessary to assess the value of ¹⁸F-FDG PET as an independent biomarker for subtle vascular wall inflammation detection.

Myocardial innervation and perfusion imaging during LVAD implantation: a nuclear imaging approach

In recent years, heart failure has been recognized as a major and increasing public health issue. In the context of the shortage of heart donors and increasing waiting time on the transplantation list, nonpulsatile left ventricular assist devices (LVAD) have shown their efficiency in reducing mortality and improving quality of life in patients with end-stage heart failure. Among LVAD recipients, a minority of patients will recover a normal cardiac function, allowing pump weaning. However, the evaluation of intrinsic cardiac function is particularly challenging and still a matter of debate in LVAD recipients.