Clinical Factors Associated with Time-Specific Distribution of 18F-Fluorodeoxyglucose in Large-Vessel Vasculitis

Dual-Time-Point 18F-FDG PET/CT in Infective Endocarditis: Impact of Delayed Imaging in the Definitive Diagnosis of Endocarditis

Infective endocarditis (IE) is a major public health condition due to the associated high morbidity and mortality. Our objective was to evaluate the utility of dual-time 2-deoxy-2-[18F] fluoro-D-glucose (18F-FDG) Positron Emission Tomography/Computed Tomography (PET/CT) imaging in the diagnosis of active IE in patients with suspected native valve endocarditis (NVE) and prosthetic valve endocarditis (PVE). For this purpose, a retrospective study was carried out, including patients suspicious of NVE or PVE who underwent a dual-time-point 18F-FDG PET/CT. A final diagnosis was established by the Endocarditis Team after patient follow-up using all the available findings. Sixty-nine patients were assessed. A final diagnosis of NVE was established in 3 patients of the 34 by 18F-FDG PET/CT and in the case of PVE was established in 20 patients of the 35. A statistically significant association was found when evaluating the association between PET diagnosis at early acquisition and final diagnosis of IE (χ2 = 30.198, p < 0.001) and PET diagnosis at delayed acquisition for final diagnosis of IE (χ2 = 9.412, p = 0.002). Delayed PET/CT imaging determined the IE diagnosis in 16/58 of the studies. In conclusion, delayed 18F-FDG PET/CT imaging seems to be useful in improving the definitive diagnosis of IE.

Diagnostic values of delayed additional FDG PET/CT scan in the evaluation of cardiac sarcoidosis

OBJECTIVE

This study aimed to compare the contribution of 18F-fluorodepxyglucose (FDG) positron (PET)/ computed tomography (CT) acquisition of early and delayed scans in patients with cardiac sarcoidosis (CS).

METHODS

Twenty-three patients with CS (median age: 69 years; 11 women) were retrospectively evaluated using dual-phase FDG PET/CT. All patients were instructed to consume a low-carbohydrate diet followed by fasting for 18 h before FDG injection to reduce physiological myocardial uptake. PET/CT was acquired at 60 min (early) and 100 min (delayed) after FDG administration. Focal and focal on diffuse uptake on visual analysis was considered positive for CS. A semi-quantitative analysis was performed using the maximum standardized uptake value (SUVmax) of the cardiac lesion and the mean SUV (SUVmean) of the blood pool.

RESULTS

Significant myocardial FDG uptake was observed in 21 patients (91.3%) in the early acquisition group and in 23 patients in the delayed scan group (100%). Compared to the early scan, the delayed scan showed a significantly higher SUVmax of the cardiac lesion [median, 4.0; IQR (interquartile range, 2.9 to 7.0) vs. 5.8 (IQR 3.7 to 10.1); P = 0.0030] and a significantly lower SUVmean of blood pool [median, 1.3 (IQR, 1.2 to 1.4) vs. 1.1 (IQR, 0.9 to 1.2); P < 0.0001].

CONCLUSION

Delayed FDG PET/CT acquisition improves detection accuracy in patients with CS compared to early scans with washout of the blood pool activity. Therefore, it can contribute to a more accurate assessment of CS.

Role of splenic and bone marrow uptake at 18 F-FDG PET/CT for the assessment of large vessels vasculitis and the influence of glucocorticoids therapy on their values

INTRODUCTION

To assess the relationship between splenic and bone marrow (BM) uptake with the presence of large vessel vasculitis (LVV) at 18 F-FDG PET/CT and to evaluate the influence of glucocorticoid (GC) therapy on these uptakes.

METHODS

One hundred and one subjects with LVV and 18 F-FDG PET/CT were included in the study. Clinical features, including blood samples and duration of GC therapy, were collected. Standardized uptake value body weight max (SUVmax) of the spleen, BM, liver and arterial walls were extracted; spleen/liver (SL) and BM/liver (BML) ratios were calculated. Chi-square and T-test were used to assess the relationship between PET/CT parameters and clinical features with the presence of LVV. Rank correlation was used to evaluate the correlation between PET/CT parameters and clinical parameters. Receiver operating curve (ROC) analysis was used to find the best parameter able to discriminate between positive and negative PET/CT. All analyses were performed considering the duration of GC therapy.

RESULTS

Significant correlation for PET/CT results with spleen uptake (P-value = 0.001), SL (P-value < 0.001) and BML (P-value = 0.005) were reported in patients with no more than 3 days of therapy; the correlation with SL was confirmed in the total cohort of patients. A value of 0.92 for SL had an AUC of 0.959, a sensitivity of 92.6% and a specificity of 96.6% (P-value < 0.001) in predicting PET/CT results.

CONCLUSION

Higher splenic and BM uptake in patients with positive PET/CT for LVV were reported. A long duration of GC therapy is able to reduce such uptakes.

Differentiation of lower limb vasculitis from physiological uptake on FDG PET/CT imaging

PURPOSES

To analyze the difference of 2-deoxy-2-[¹⁸F]fluoro-D-glucose (¹⁸F-FDG) uptake between vasculitis and non-vasculitic patients in PET/CT imaging and the factors related to vascular uptake in non-vasculitic patients. To investigate the feasibility of identifying vasculitis of the lower limb and physiological uptake with delayed imaging.

PROCEDURES

Among 244 patients who underwent PET/CT examination, imaging features of patients with or without vasculitis were retrospectively analyzed. The factors related to FDG uptake in the lower limb vessels of non-vasculitic patients were analyzed. Another 44 patients with suspected systemic vasculitis in PET/CT were prospectively studied to analyze the efficacy of delayed imaging on differentiating vascular uptake in lower limbs.

RESULTS

In PET/CT imaging of patients with vasculitis, involvement of trunk vessels showed segmental or diffuse FDG distribution. Lower limb vascular involvement showed reticular uptake accompanied by nodular or patchy changes. In non-vasculitic patients, vascular uptake mainly showed linear uptake in lower limb vessels and there was no significant difference in uptake degree compared with vasculitis patients. Body weight and interval time were the independent influence factors of vascular uptake in lower limbs of non-vasculitic patients. In delayed imaging, lower limb vasculitis all showed reticular uptake and physiological uptake all showed a linear pattern. ROC analysis showed the change rate of SUV_max (≥ 20%) between early and delayed imaging could delineate physiological vascular uptake with a sensitivity of 100% and specificity of 81.0%.

CONCLUSIONS

When PET/CT is used for the diagnosis and classification of vasculitis, the physiological uptake of lower limb vessels may mislead the diagnosis. PET/CT imaging features or delayed imaging improved diagnostic efficacy.

Updates on the diagnosis and monitoring of giant cell arteritis

This mini-review offers a critical appraisal of the currently employed imaging or histopathological tools to diagnose and monitor giant cell arteritis (GCA). An overview of the most updated evidence and current application of color duplex ultrasonography (US), temporal artery biopsy (TAB), 18-fluorodeoxyglucose [18F] FDG-PET/CT, magnetic resonance imaging, and computed tomography angiography is provided. The main limitations of each tool, and the most relevant research developments are discussed. The review highlights the complementary value of the available modalities to ensure a correct diagnosis of GCA, and to provide valuable prognostic information. Novel evidence is accumulating to support the role of imaging, and particularly US, as a monitoring tool for the disease, opening new perspectives for the future management of large vessel vasculitis.

Semi-Quantitative [18F]FDG-PET/CT ROC-Analysis-Based Cut-Offs for Aortitis Definition in Giant Cell Arteritis

[18F]fluorodeoxyglucose-positron emission tomography/computed tomography ([18F]FDG-PET/CT) is used to diagnose large vessel vasculitis in giant cell arteritis (GCA). We aimed to define a semi-quantitative threshold for identifying GCA aortitis from aortic atheroma or the control. Contrast enhanced computed tomography (CECT) was used as the reference imaging for aortic evaluation and to define aortitis, aortic atheroma and control aortas. [18F]FDG-PET/CT was performed on 35 GCA patients and in two different control groups (aortic atheroma (n = 70) and normal control (n = 35)). Aortic semi-quantitative features were compared between the three groups. GCA patients without aortitis on CECT were excluded. Of the GCA patients, 19 (54.3%) were not on glucocorticoids (GC) prior to [18F]FDG-PET/CT. The SUVmax, TBRblood and TBRliver aortic values were significantly higher in the GCA aortitis group than in the aortic atheroma and control groups (p < 0.001). Receiver operating characteristic curve analyses brought to light quantitative cut-off values allowing GCA aortitis diagnosis with optimal sensitivity and specificity versus control or aortic atheroma patients for each PET-based feature analyzed. Considering the overall aorta, a SUVmax threshold of 3.25 and a TBRblood threshold of 1.75 had a specificity of 83% and 75%, respectively, a sensitivity of 81% and 81%, respectively, and the area under the ROC curve (AUC) was 0.86 and 0.83, respectively, for aortitis detection compared to control groups in GCA cases with GC. A SUVmax threshold of 3.45 and a TBRblood threshold of 1.97 had a specificity of 90% and 93%, respectively, a sensitivity of 89% and 89%, respectively, with an AUC of 0.89 and 0.96, respectively, for aortitis detection compared to the control in GC-free GCA cases. Discriminative thresholds of SUVmax and TBRblood for the diagnosis of GCA aortitis were established using CECT as the reference imaging.

Large vessel vasculitis with rare presentation of acute rhabdomyolysis: A case report and review of literature

BACKGROUND

Musculoskeletal involvement in primary large vessel vasculitis (LVV), including giant cell arteritis and Takayasu's arteritis (TAK), tends to be subacute. With the progression of arterial disease, patients may develop polyarthralgia and myalgias, mainly involving muscle stiffness, limb/jaw claudication, cold/swelling extremities, etc. Acute development of rhabdomyolysis in addition to aortic aneurysm is uncommon in LVV. Herein, we report a rare case of LVV with the first presentation of acute rhabdomyolysis.

CASE SUMMARY

A 70-year-old Asian woman suffering from long-term low back pain was hospitalized due to limb claudication, dark urine and an elevated creatine kinase (CK) level. After treatment with fluid resuscitation and antibiotics, the patient remained febrile. Her workup showed persistent elevated levels of inflammatory markers, and imaging studies revealed an aortic aneurysm. A decreasing CK was evidently combined with elevated inflammatory markers and negativity for anti-neutrophilic cytoplasmic antibodies. LVV was suspected and confirmed by magnetic resonance angiography and positron emission tomography with 18F-fluorodeoxyglucose/computed tomography. With a favourable response to immunosuppressive treatment, her symptoms resolved, and clinical remission was achieved one month later. However, after failing to follow the tapering schedule, the patient was readministered 25 mg/d prednisolone due to disease relapse. Follow-up examinations showed decreased inflammatory markers and substantial improvement in artery lesions after 6 mo of treatment. At the twelve-month follow-up, she was clinically stable and maintained on corticosteroid therapy.

CONCLUSION

An exceptional presentation of LVV with acute rhabdomyolysis is described in this case, which exhibited a good response to immunosuppressive therapy, suggesting consideration for a differential diagnosis when evaluating febrile patients with myalgia and elevated CK. Timely use of high-dose steroids until a diagnosis is established may yield a favourable outcome.

ACR Appropriateness Criteria® Noncerebral Vasculitis

Noncerebral vasculitis is a wide-range noninfectious inflammatory disorder affecting the vessels. Vasculitides have been categorized based on the vessel size, such as large-vessel vasculitis, medium-vessel vasculitis, and small-vessel vasculitis. In this document, we cover large-vessel vasculitis and medium-vessel vasculitis. Due to the challenges of vessel biopsy, imaging plays a crucial role in diagnosing this entity. While CTA and MRA can both provide anatomical details of the vessel wall, including wall thickness and enhancement in large-vessel vasculitis, FDG-PET/CT can show functional assessment based on the glycolytic activity of inflammatory cells in the inflamed vessels. Given the size of the vessel in medium-vessel vasculitis, invasive arteriography is still a choice for imaging. However, high-resolution CTA images can depict small-caliber aneurysms, and thus can be utilized in the diagnosis of medium-vessel vasculitis. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Toward Reliable Uptake Metrics in Large Vessel Vasculitis Studies

The aim of this study is to investigate the influence of sex, age, fat mass, fasting blood glucose level (FBGL), and estimated glomerular filtration rate (eGFR) on blood pool activity in patients with large vessel vasculitis (LVV). Blood pool activity was measured in the superior caval vein using mean, maximum, and peak standardized uptake values corrected for body weight (SUVs) and lean body mass (SULs) in 41 fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) scans of LVV patients. Sex influence on the blood pool activity was assessed with t-tests, while linear correlation analyses were used for age, fat mass, FBGL, and eGFR. Significantly higher SUVs were found in women compared with men, whereas SULs were similar between sexes. In addition, higher fat mass was associated with increased SUVs (r = 0.56 to 0.65; all p < 0.001) in the blood pool, but no correlations were found between SULs and fat mass (r = −0.25 to −0.15; all p > 0.05). Lower eGFR was associated with a higher FDG blood pool activity for all uptake values. In FDG-PET/CT studies with LVV patients, we recommend using SUL over SUV, while caution is advised in interpreting SUV and SUL measures when patients have impaired kidney function.

Vascular Uptake on 18F-FDG PET/CT During the Clinically Inactive State of Takayasu Arteritis Is Associated with a Higher Risk of Relapse

PURPOSE

To evaluate whether vascular uptake on ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) during the clinically inactive state of Takayasu arteritis (TAK) is associated with disease relapse.

MATERIALS AND METHODS

Patients with TAK who underwent ¹⁸F-FDG PET/CT during the clinically inactive state of the disease between 2006 and 2019 were included. Clinically inactive disease was defined as a status not fulfilling the National Institutes of Health (NIH) criteria for active disease in TAK. Relapse was defined as recurrence of clinically active disease after a clinically inactive period, requiring change in the treatment regimen. Vascular uptake on ¹⁸F-FDG PET/CT was assessed using target/background ratio (TBR), calculated as arterial maximum standardized uptake value (SUV)/mean SUV in venous blood pool. Multivariable Cox regression analysis was performed to identify factors associated with relapse.

RESULTS

A total of 33 patients with clinically inactive TAK were included. During a median observation period of 4.5 (0.9-8.1) years, relapse occurred in 9 (27.3%) patients at median 1.3 (0.7-6.9) years. Notably, TBR [1.5 (1.3-1.8) vs. 1.3 (1.1-1.4), p=0.044] was significantly higher in patients who relapsed than in those who did not. On multivariable Cox regression analysis, the presence of NIH criterion 2 [adjusted hazard ratio (HR): 7.044 (1.424-34.855), p=0.017] and TBR [adjusted HR: 11.533 (1.053-126.282), p=0.045] were significantly associated with an increased risk of relapse.

CONCLUSION

Vascular uptake on ¹⁸F-FDG PET/CT and the presence of NIH criterion 2 are associated with future relapse in patients with clinically inactive TAK.

Resolution of vascular inflammation in patients with new-onset giant cell arteritis: data from the RIGA study

OBJECTIVES

Efficacy evaluation of GCA treatment is primarily based on non-specific symptoms and laboratory markers. We aimed to assess the change in vascular inflammation in patients with large vessel (LV)-GCA under different treatments using [18F]FDG PET/CT.

METHODS

Observational study on patients with new-onset, active LV-GCA starting treatment with either prednisolone monotherapy (PRED) or combination with MTX or tocilizumab (TOC). All patients underwent baseline and follow-up PET/CT. The aorta and its major branches were assessed using PET vascular activity score (PETVAS) by independent readers. Cumulative glucocorticoid doses and cessation of glucocorticoid treatment were documented in all patients.

RESULTS

We included 88 LV-GCA patients, 27 were treated with PRED, 42 with MTX and 19 with TOC. PETVAS decreased from 18.9-8.0 units at follow-up in the overall population (P <0.001). PETVAS changes were numerically higher in patients receiving MTX (-12.3 units) or TOC (-11.7 units) compared with PRED (-8.7). Mean cumulative prednisolone dosages were 5637, 4418 and 2984 mg in patients treated with PRED, MTX and TOC (P =0.002). Risk ratios for glucocorticoid discontinuation at the time of follow-up PET/CT were 6.77 (95% CI: 1.01, 45.29; P =0.049) and 16.25 (95% CI: 2.60, 101.73; P =0.003) for MTX and TOC users compared with PRED users.

CONCLUSION

Treatment of LV-GCA inhibits vascular inflammation in the aorta and its major branches. While similar control of vascular inflammation was achieved with PRED, MTX and TOC treatments, TOC showed a strong glucocorticoid sparing effect, supporting the concept of initial combination therapy.

Imaging Tests in the Early Diagnosis of Giant Cell Arteritis

Early recognition of giant cell arteritis (GCA) is crucial to avoid the development of ischemic vascular complications, such as blindness. The classic approach to making the diagnosis of GCA is based on a positive temporal artery biopsy, which is among the criteria proposed by the American College of Rheumatology (ACR) in 1990 to classify a patient as having GCA. However, imaging techniques, particularly ultrasound (US) of the temporal arteries, are increasingly being considered as an alternative for the diagnosis of GCA. Recent recommendations from the European League Against Rheumatism (EULAR) for the use of imaging techniques for large vessel vasculitis (LVV) included US as the first imaging option for the diagnosis of GCA. Furthermore, although the ACR classification criteria are useful in identifying patients with the classic cranial pattern of GCA, they are often inadequate in identifying GCA patients who have the extracranial phenotype of LVV. In this sense, the advent of other imaging techniques, such as magnetic resonance imaging (MRI), computed tomography (CT), and positron emission tomography (PET)/CT, has made it possible to detect the presence of extracranial involvement of the LVV in patients with GCA presenting as refractory rheumatic polymyalgia without cranial ischemic manifestations. Imaging techniques have been the key elements in redefining the diagnostic work-up of GCA. US is currently considered the main imaging modality to improve the early diagnosis of GCA.

Multimodality Imaging of Large Vessel Vasculitis, From the AJR Special Series on Inflammation

Large vessel vasculitis (LVV) is a non-infectious inflammation of the large vessels, including the aorta and its main branches. Imaging plays an essential role in diagnosing LVV, given the challenges of tissue biopsy. This article reviews the types of LVV, and the multimodality imaging tools available to establish the diagnosis in patients with LVV. The cornerstone of imaging diagnosis is morphologic assessment using grey-scale ultrasound, combined grey-scale US with color Doppler US, CTA, or MRA. In the last decade, substantial progress has been made in functional and molecular imaging with FDG PET/CT for the diagnosis of LVV. Investigation is ongoing to develop novel MRA techniques and new PET tracers to assess disease activity and to differentiate the various vasculitides. An algorithm is provided to guide imaging technique selection based on the patient's specific clinical presentation.

Comparing Semi-quantitative and Qualitative Methods of Vascular FDG-PET Activity Measurement in Large-Vessel Vasculitis

The study rationale was to assess the performance of qualitative and semi-quantitative scoring methods for ¹⁸F-fluorodeoxyglucose positron emission tomography (FDG-PET) assessment in large-vessel vasculitis (LVV). Methods: Patients with giant cell arteritis (GCA) or Takayasu's arteritis (TAK) underwent clinical and imaging assessment, blinded to each other, within a prospective observational cohort. FDG-PET-CT scans were interpreted for active vasculitis by central reader assessment. Arterial FDG uptake was scored by qualitative visual assessment using the PET vascular activity score (PETVAS) and by semi-quantitative assessment using standardized uptake values (SUV) and target-to-background ratios (TBR) relative to liver/blood activity. Performance of each scoring method was assessed by intra-rater reliability using the intra-class coefficient (ICC) and area under receiver-operator characteristic curves (AUC), using physician assessment of clinical disease activity and reader interpretation of vascular PET activity as independent reference standards. Wilcoxon signed-rank test was used to analyze change in arterial FDG uptake over time. Results: Ninety-five patients (GCA=52; TAK=43) contributed 212 FDG-PET studies. The ICC for semi-quantitative evaluation [0.99 (range 0.98-1.00)] was greater than the ICC for qualitative evaluation [0.82 (range 0.56-0.93)]. PETVAS and TBR metrics were more strongly associated with reader interpretation of PET activity than SUV metrics. All assessment methods were significantly associated with physician assessment of clinical disease activity, but the semi-quantitative metric TBRLiver¬ achieved the highest AUC (0.66). Significant but weak correlations with C-reactive protein were observed for SUV metrics (r = 0.19, p<0.01) and TBRLiver (r = 0.20, p<0.01) but not for PETVAS. In response to increased treatment in 56 patients, arterial FDG uptake was significantly reduced when measured by semi-quantitative (TBRLiver 1.31 to 1.23, 6.1% ∆, p<0.0001) or qualitative (PETVAS 22 to 18, p<0.0001) methods. Semi-quantitative metrics provided complementary information to qualitative evaluation in cases of severe vascular inflammation. Conclusion: Both qualitative and semi-quantitative methods to measure arterial FDG uptake are useful to assess and monitor vascular inflammation in LVV. Compared to qualitative metrics, semi-quantitative methods have superior reliability and better discriminate treatment response in cases of severe inflammation.

Systemic vasculitides and the role of multitechnique imaging in the diagnosis

Vasculitis, a systemic disease characterised by inflammation of the blood vessels, remains challenging to diagnose and manage. Vessel size has been the basis for classifying systemic vasculitides. Imaging plays a vital role in diagnosing this challenging disease. This review article aims (a) to summarise up-to-date literature in this field, as well as include classification updates and (b) to review available imaging techniques, recent advances, and emphasis on imaging findings to diagnose large vessel vasculitides.

The Utility of 18F-FDG PET/CT in Patients With Clinical Suspicion of Polymyalgia Rheumatica and Giant Cell Arteritis: A Prospective, Observational, and Cross-sectional Study

Objective

To define the proportions of agreement between fluorine‐18‐fluorodeoxyglucose (18F‐FDG) positron emission tomography/computed tomography (PET/CT), clinical diagnosis, and temporal artery biopsy (TAB) in patients with polymyalgia rheumatica (PMR) and giant cell arteritis (GCA). Furthermore, the association of 18F‐FDG PET/CT uptake patterns and clinical presentation of newly diagnosed PMR and GCA was investigated.

Methods

Eighty patients newly suspected of having PMR, GCA, or concomitant PMR and GCA were included and followed for 40 weeks. Every patient underwent an 18F‐FDG PET/CT scan before or within 3 days of initiation of steroids in case of GCA. FDG uptakes in 8 paired articular/periarticular sites and 14 arterial segments were evaluated based on a 4‐point visual grading scale.

Results

Of the 80 patients (female: 50 [62.5%]; mean age ± SD: 72.0 ± 7.9), 64 (80.0%) patients were diagnosed with pure PMR, 3 (3.7%) with pure GCA, and 10 (12.5%) with concomitant PMR and GCA. Additionally, three (3.7%) patients were diagnosed with seronegative rheumatoid arthritis during the follow‐up period. For the diagnosis of PMR, 18F‐FDG PET/CT had a proportion of agreement of 75.3 (64.2‐84.4), compared with clinical diagnosis. When comparing findings of 18F‐FDG PET/CT with TAB, 18F‐FDG PET/CT had a proportion of agreement of 93.0 (84.3‐97.7) in all included patients and 69.2 (38.6‐90.9) in the subgroup of patients with vasculitis. C‐reactive protein was significantly higher in patients with PMR activity on 18F‐FDG PET/CT compared with those without 18F‐FDG PET/CT activity (P value = 0.006).

Conclusions

18F‐FDG PET/CT is a powerful imaging technique in PMR and GCA that was in good agreement with clinical diagnosis and TAB.

Procedural recommendations of cardiac PET/CT imaging: standardization in inflammatory-, infective-, infiltrative-, and innervation (4Is)-related cardiovascular diseases: a joint collaboration of the EACVI and the EANM

With this document, we provide a standard for PET/(diagnostic) CT imaging procedures in cardiovascular diseases that are inflammatory, infective, infiltrative, or associated with dysfunctional innervation (4Is). This standard should be applied in clinical practice and integrated in clinical (multicenter) trials for optimal procedural standardization. A major focus is put on procedures using [¹⁸F]FDG, but 4Is PET radiopharmaceuticals beyond [¹⁸F]FDG are also described in this document. Whilst these novel tracers are currently mainly applied in early clinical trials, some multicenter trials are underway and we foresee in the near future their use in clinical care and inclusion in the clinical guidelines. Finally, PET/MR applications in 4Is cardiovascular diseases are also briefly described. Diagnosis and management of 4Is-related cardiovascular diseases are generally complex and often require a multidisciplinary approach by a team of experts. The new standards described herein should be applied when using PET/CT and PET/MR, within a multimodality imaging framework both in clinical practice and in clinical trials for 4Is cardiovascular indications.