EANM/SNMMI guideline for 18F-FDG use in inflammation and infection

Diagnostic imaging of the diabetic foot: an EANM evidence-based guidance

PURPOSE

Consensus on the choice of the most accurate imaging strategy in diabetic foot infective and non-infective complications is still lacking. This document provides evidence-based recommendations, aiming at defining which imaging modality should be preferred in different clinical settings.

METHODS

This working group includes 8 nuclear medicine physicians appointed by the European Association of Nuclear Medicine (EANM), 3 radiologists and 3 clinicians (one diabetologist, one podiatrist and one infectious diseases specialist) selected for their expertise in diabetic foot. The latter members formulated some clinical questions that are not completely covered by current guidelines. These questions were converted into statements and addressed through a systematic analysis of available literature by using the PICO (Population/Problem-Intervention/Indicator-Comparator-Outcome) strategy. Each consensus statement was scored for level of evidence and for recommendation grade, according to the Oxford Centre for Evidence-Based Medicine (OCEBM) criteria.

RESULTS

Nine clinical questions were formulated by clinicians and used to provide 7 evidence-based recommendations: (1) A patient with a positive probe-to-bone test, positive plain X-rays and elevated ESR should be treated for presumptive osteomyelitis (OM). (2) Advanced imaging with MRI and WBC scintigraphy, or [18F]FDG PET/CT, should be considered when it is needed to better evaluate the location, extent or severity of the infection, in order to plan more tailored treatment. (3) In a patient with suspected OM, positive PTB test but negative plain X-rays, advanced imaging with MRI or WBC scintigraphy + SPECT/CT, or with [18F]FDG PET/CT, is needed to accurately assess the extent of the infection. (4) There are no evidence-based data to definitively prefer one imaging modality over the others for detecting OM or STI in fore- mid- and hind-foot. MRI is generally the first advanced imaging modality to be performed. In case of equivocal results, radiolabelled WBC imaging or [18F]FDG PET/CT should be used to detect OM or STI. (5) MRI is the method of choice for diagnosing or excluding Charcot neuro-osteoarthropathy; [18F]FDG PET/CT can be used as an alternative. (6) If assessing whether a patient with a Charcot foot has a superimposed infection, however, WBC scintigraphy may be more accurate than [18F]FDG PET/CT in differentiating OM from Charcot arthropathy. (7) Whenever possible, microbiological or histological assessment should be performed to confirm the diagnosis. (8) Consider appealing to an additional imaging modality in a patient with persisting clinical suspicion of infection, but negative imaging.

CONCLUSION

These practical recommendations highlight, and should assist clinicians in understanding, the role of imaging in the diagnostic workup of diabetic foot complications.

Role of F-18 FDG PET-CT in neuropsychiatric systemic lupus erythematosus

BACKGROUND

Neuropsychiatric systemic lupus erythematosus (NPSLE) is a major contributor to morbidity and mortality in systemic lupus erythematosus (SLE) patients. To date no single clinical, laboratory or imaging test has proven accurate for NPSLE diagnosis which is a testament to the intricate and multifactorial pathophysiological mechanisms suspected to exist. Functional imaging with FDG PET-CT has shown promise in NPSLE diagnosis, detecting abnormalities prior to changes evident on anatomical imaging. Research indicates that NPSLE may be more aggressive in people of African descent with higher mortality rates, making rapid and correct diagnosis even more important in the African context.

METHODS

In this narrative review, we provide a thorough appraisal of the current literature on the role of FDG PET-CT in NPSLE. Large, well-known databases were searched using appropriate search terms. Manual searches of references of retrieved literature were also included.

FINDINGS

A total of 73 article abstracts were assessed, yielding 26 papers that were directly relevant to the topic of FDG PET-CT in NPSLE. Results suggest that FDG PET-CT is a sensitive imaging test for NPSLE diagnosis and may play a role in assessing treatment response. It is complementary to routine anatomical imaging, particularly in diffuse manifestations of the disease. Newer quantitative analyses are commonly used for interpretation and can detect even subtle abnormalities, missed on visual inspection. Findings of group-wise analyses of FDG PET-CT scans in NPSLE patients are important in furthering our understanding of the complicated pathophysiological mechanisms involved. Limitations of FDG PET-CT include its lack of specificity, high cost and poor access.

CONCLUSION

FDG PET-CT is a sensitive test for NPSLE diagnosis but is hampered by lack of specificity. It is a valuable tool for clinicians managing SLE patients, particularly when anatomical imaging is negative. Its exact application will depend on the local context and clinical scenario.

18F-fluorodeoxyglucose uptake patterns in positron emission tomography/computed tomography caused by inflammation and/or infection after graft surgery for thoracic aortic dissection

BACKGROUND

To identify 18F-fluorodeoxyglucose (FDG) uptake patterns in positron emission tomography/computed tomography (PET/CT) caused by infection, inflammation, surgical material, and/or graft coating.

METHODS AND RESULTS

Of 610 consecutive patients with thoracic aortic graft surgery, 60 patients with 187 PET/CT were retrospectively included. We quantified FDG uptake in all grafts using maximum standardized uptake value (SUVmax) alone and in relation to liver background (SUVratio) and determined the uptake pattern. Mixed linear regression models with random slope and intercept were applied for the analysis of SUVratio over time and generalized estimating equations to analyze the associations with anastomosis uptake. FDG uptake was frequently focal (90%), higher in infected than in noninfected grafts (mean SUVratio 2.19; 95% CI 2.05-2.32 vs. 1.63; 1.46-1.79, P < 0.001), and decreasing slowly over time (SUVratio per year since surgery -0.048; 95% CI -0.15- 0.051, P = 0.34), without a difference in slope between infected and noninfected grafts (P = 0.52). There was no evidence of an interaction between SUVratio and use of BioGlue® surgical adhesive (intercept P = 0.73, slope P = 0.71), or graft coating (gelatin and collagen, all P > 0.7). FDG uptake at the anastomosis was more frequent in noninfected grafts than in infected grafts (66% vs. 21%, odds ratio (OR) 11.34; 95% CI 3.61-35.66, P < 0.001). This effect was attenuated by the use of BioGlue® (OR 5.05; 95% CI 0.45-56.9, P = 0.19).

CONCLUSIONS

FDG uptake in PET/CT after thoracic aortic graft surgery is higher in infected grafts than in noninfected grafts. In noninfected grafts, focal uptake is also frequent, mostly anastomosis-associated, not associated with graft coating, and possibly affected by the use of BioGlue®.

The Role of 18-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography (18F-FDG PET/CT) in the Diagnosis and Evaluation of Spondylodiscitis

Spondylodiscitis, characterized by inflammation of the intervertebral disc and adjacent vertebral bodies, presents a diagnostic challenge due to its nonspecific clinical manifestations and variable imaging findings. This review examines the role of PET-CT with FDG, in the evaluation of spondylodiscitis, focusing on its utility in diagnosis, assessment of disease extent, treatment response monitoring, and prognostication. FDG PET-CT, by combining metabolic and anatomical imaging modalities, offers superior sensitivity and specificity compared to conventional imaging techniques in detecting infectious foci, distinguishing between infection and post-treatment changes, and identifying occult sources of infection. Additionally, FDG PET-CT facilitates the localization of infection, aiding in targeted biopsy and guiding surgical intervention. Moreover, quantitative PET parameters, such as standardized uptake values (SUVs), hold promise for predicting treatment response and prognosis. Despite its advantages, FDG PET-CT has limitations, including false-positive results in the setting of inflammation and limited availability in resource-constrained settings. Collaborative efforts between radiologists, nuclear medicine specialists, infectious disease specialists, and spine surgeons are essential to optimize the role of FDG PET-CT in the multidisciplinary management of spondylodiscitis. Further research is warranted to elucidate the cost-effectiveness and clinical impact of FDG PET-CT in this challenging clinical entity.

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.

EANM consensus document on the use of [18F]FDG PET/CT in fever and inflammation of unknown origin

PURPOSE

Patients with fever and inflammation of unknown origin (FUO/IUO) are clinically challenging due to variable clinical presentations with nonspecific symptoms and many differential diagnoses. Positron emission tomography/computed tomography (PET/CT) with 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) is increasingly used in FUO and IUO, but the optimal diagnostic strategy remains controversial. This consensus document aims to assist clinicians and nuclear medicine specialists in the appropriate use of [18F]FDG-PET/CT in FUO and IUO based on current evidence.

METHODS

A working group created by the EANM infection and inflammation committee performed a systematic literature search based on PICOs with "patients with FUO/IUO" as population, "[18F]FDG-PET/CT" as intervention, and several outcomes including pre-scan characteristics, scan protocol, diagnostic yield, impact on management, prognosis, and cost-effectiveness.

RESULTS

We included 68 articles published from 2001 to 2023: 9 systematic reviews, 49 original papers on general adult populations, and 10 original papers on specific populations. All papers were analysed and included in the evidence-based recommendations.

CONCLUSION

FUO and IUO remains a clinical challenge and [18F]FDG PET/CT has a definite role in the diagnostic pathway with an overall diagnostic yield or helpfulness in 50-60% of patients. A positive scan is often contributory by directly guiding treatment or subsequent diagnostic procedure. However, a negative scan may be equally important by excluding focal disease and predicting a favorable prognosis. Similar results are obtained in specific populations such as ICU-patients, children and HIV-patients.

A practical approach to interpretation of 18F-fluorodeoxyglucose positron emission tomography/computed tomography for postoperative spine infection

OBJECTIVE

18F-fluorodeoxyglucose-PET/CT is the imaging modality of choice for the diagnosis of postoperative spine infection. Published interpretation criteria are variable and often incompletely described. The objective was to develop a practical and standardized approach.

MATERIALS AND METHODS

Two-hundred-twenty-seven FDG-PET/CTs performed on 140 postoperative patients over a 7-year period were reviewed retrospectively. The presence or absence of infection was determined from clinical history, microbiology, other investigations, and clinical outcome during a minimum 6-month follow-up.

RESULTS

No activity attributable to normal healing was seen in the post-discectomy space or at the bone-hardware interface in the absence of a complication at any stage. Within the incision, activity from normal healing persisted for months. Wound infections were diagnosed clinically, and most had already been treated before FDG-PET/CT was done to assess deep structures. With proven infection, 95% of cases had activity in bone or soft tissue outside the surgical field. The remaining 5% had activity confined to the post-discectomy space. Sterile hardware loosening may cause elevated activity which remains confined to the bone/hardware interface. Pathogens are introduced directly at the time of surgery and may be avirulent resulting in indolent infection with low-grade activity. At the same time, activity from non-infectious causes can be intense. A semi-quantitative method using SUVmax performed poorly compared with assessment of the distribution of activity.

CONCLUSION

These observations have been incorporated into a checklist which is now being used at the time of interpretation. The potential sensitivity and specificity in the diagnosis of infection are close to 100%.

Multimodal positron emission tomography (PET) imaging in non-oncologic musculoskeletal radiology

Musculoskeletal (MSK) disorders are associated with large impacts on patient's pain and quality of life. Conventional morphological imaging of tissue structure is limited in its ability to detect pain generators, early MSK disease, and rapidly assess treatment efficacy. Positron emission tomography (PET), which offers unique capabilities to evaluate molecular and metabolic processes, can provide novel information about early pathophysiologic changes that occur before structural or even microstructural changes can be detected. This sensitivity not only makes it a powerful tool for detection and characterization of disease, but also a tool able to rapidly assess the efficacy of therapies. These benefits have garnered more attention to PET imaging of MSK disorders in recent years. In this narrative review, we discuss several applications of multimodal PET imaging in non-oncologic MSK diseases including arthritis, osteoporosis, and sources of pain and inflammation. We also describe technical considerations and recent advancements in technology and radiotracers as well as areas of emerging interest for future applications of multimodal PET imaging of MSK conditions. Overall, we present evidence that the incorporation of PET through multimodal imaging offers an exciting addition to the field of MSK radiology and will likely prove valuable in the transition to an era of precision medicine.

Bones on fire: illuminating osteomyelitis through the radiant lens of 18F-FDG PET/CT

Osteomyelitis is an inflammatory process that is caused by an infecting microorganism and leads to progressive bone destruction and loss. Osteomyelitis can occur at any age and can involve any bone. The infection can be limited to a single portion of the bone or can involve several regions, such as marrow, cortex, periosteum, and the surrounding soft tissue. Early and accurate diagnosis plays a crucial role in reducing unnecessary treatment measures, improving the patient's prognosis, and minimizing time and financial costs. In recent years, the use of functional metabolic imaging has become increasingly widespread. Among them, 18F-FDG PET/CT has emerged as a cutting-edge imaging modality that combines anatomical and functional metabolic information. It has seen rapid development in the field of infectious diseases. 18F-FDG PET/CT has been demonstrated to yield acceptable diagnostic accuracy in a number of infectious and inflammatory diseases. This review aims to provide information about the 18F-FDGPET/CT in the use of chronic osteomyelitis,osteomyelitis secondary to a contiguous focus of infection and osteomyelitis associated with peripheral vascular disease.

Low incidence of malignancy in patients with suspected polymyalgia rheumatica or giant cell arteritis, examined with FDG-PET/CT

Introduction

The need to systematically examine patients suspected of polymyalgia rheumatica (PMR) and giant cell arteritis (GCA) for malignancy is controversial. The aim of this study was to assess the frequency of malignancy in patients with suspected PMR and/or GCA who have been referred to a 2-deoxy-2-[18F]fluoro-D-glucose positron emission tomography with computed tomography (FDG-PET/CT) as part of the diagnostic investigation.

Method

The records of all patients referred to FDG-PET/CT from Center for Rheumatology and Spine Diseases, Rigshospitalet, Glostrup with the suspicion of PMR and/or GCA during a two-year period, were retrospectively reviewed. Data was analyzed with descriptive statistics, and a standard incidence ratio was calculated based on background cancer incidences extracted from the NORDCAN database.

Results

220 patients were included in the study. Findings suspicious of malignancy were found in 19 of the examinations, and in seven cases (3.2%), malignancy was confirmed. In three out of the seven cases the patients were diagnosed with PMR concomitantly with malignancy. The estimated standardized incidence ratio (SIR) for cancer compared to the background incidence of cancer in Denmark was 1.58 (95% CI 0.63-2.97), i.e., not statistically significant. There were no statistically significant differences in characteristics of the patients that were diagnosed with malignancy compared with those that were not.

Conclusion

The frequency of malignancy in this cohort of patients with suspected PMR/GCA who underwent PET/CT was low. Our results, though based on a small cohort, do not suggest that all patients with suspected PMR/GCA should systematically be examined with FDG-PET/CT for excluding malignancy.

[18F]FDG PET/CT Findings of Mass-Forming Actinomycosis in an Uncontrolled Diabetic Patient

We report a case of cervicofacial actinomycosis mimicking malignant sarcoma in a 78-year-old man with diabetes. High lesion uptake and decreased cerebral uptake on [18F]FDG PET/CT provide a potentially important diagnostic clue suggesting infectious disease in a poorly controlled diabetic patient.

Exploring the potential of radiolabeled duramycin as an infection imaging probe

The continuous pursuit of designing an ideal infection imaging agent is a crucial and ongoing endeavor in the field of biomedical research. Duramycin, an antimicrobial peptide exerts its antimicrobial action on bacteria by specific recognition of phosphatidylethanolamine (PE) moiety present on most bacterial membranes, particularly Escherichia coli (E. coli). E. coli membranes contain more than 60% PE. Therefore, duramycin is an attractive candidate for the formulation of probes for in situ visualization of E. coli driven focal infections. The aim of the present study is to develop 99m Tc labeled duramycin as a single-photon emission computed tomography (SPECT)-based agent to image such infections. Duramycin was successfully conjugated with a bifunctional chelator, hydrazinonicotinamide (HYNIC). PE specificity of HYNIC-duramycin was confirmed by a dye release assay on PE-containing model membranes. Radiolabeling of HYNIC-duramycin with 99m Tc was performed with consistently high radiochemical yield (>90%) and radiochemical purity (>90%). [99m Tc]Tc-HYNIC-duramycin retained its specificity for E. coli, in vitro. SPECT and biodistribution studies showed that the tracer could specifically identify E. coli driven infection at 3 h post injection. While 99m Tc-labeled duramycin is employed for monitoring early response to cancer therapy and cardiotoxicity, the current studies have confirmed, for the first time, the potential of utilizing 99m Tc labeled duramycin as an imaging agent for detecting bacteria. Its application in imaging PE-positive bacteria represents a novel and promising advancement.

Usefulness of 18F-FDG PET-CT in the Management of Febrile Neutropenia: A Retrospective Cohort from a Tertiary University Hospital and a Systematic Review

Febrile neutropenia (FN) is a complication of hematologic malignancy therapy. An early diagnosis would allow optimization of antimicrobials. The 18F-FDG-PET-CT may be useful; however, its role is not well established. We analyzed retrospectively patients with hematological malignancies who underwent 18F-FDG-PET-CT as part of FN management in our university hospital and compared with conventional imaging. In addition, we performed a systematic review of the literature assessing the usefulness of 18F-FDG-PET-CT in FN. A total of 24 cases of FN underwent 18F-FDG-PET-CT. In addition, 92% had conventional CT. In 5/24 episodes (21%), the fever was of infectious etiology: two were bacterial, two were fungal, and one was parasitic. When compared with conventional imaging, 18F-FDG-PET-CT had an added value in 20 cases (83%): it diagnosed a new site of infection in 4 patients (17%), excluded infection in 16 (67%), and helped modify antimicrobials in 16 (67%). Antimicrobials could be discontinued in 10 (41.6%). We identified seven publications of low quality and one randomized trial. Our results support those of the literature. The available data suggest that 18F-FDG-PET-CT is useful in the management of FN, especially to diagnose fungal infections and rationalize antimicrobials. This review points out the low level of evidence and indicates the gaps in knowledge.

Quantifying 18F-Fluorodeoxyglucose Uptake in Perianal Fistulas on PET/CT: A Retrospective Analysis

RATIONALE AND OBJECTIVES

The use of 18F-fluorodeoxyglucose positron emission tomography-computed tomography (FDG-PET/CT) in assessing inflammatory diseases has shown significant promise. Uptake patterns in perianal fistulas, which may be an incidental finding on PET/CT, have not been purposefully studied. Our aim was to compare FDG uptake of perianal fistulas to that of the liver and anal canal in patients who underwent PET/CT for hematologic/oncologic diagnosis or staging.

MATERIALS AND METHODS

We retrospectively identified patients who underwent FDG-PET/CT imaging between January 2011 and May 2023, where the report described a perianal fistula or abscess. PET/CTs of patients included in the study were retrospectively analyzed to record the maximum standardized uptake value (SUVmax) of the fistula, abscess, anal canal, rectum, and liver. Fistula-to-liver and Fistula-to-anus SUVmax ratios were calculated. We statistically compared FDG activity among the fistula, liver, and anal canal. We also assessed FDG activity in patients with vs. without anorectal cancer, as well as across different St. James fistula grades.

RESULTS

The study included 24 patients with identifiable fistulas. Fistula SUVmax (mean=10.8 ± 5.28) was significantly higher than both the liver (mean=3.09 ± 0.584, p < 0.0001) and the anal canal (mean=5.98 ± 2.63, p = 0.0005). Abscess fistula SUVmax was 15.8 ± 4.91. St. James grade 1 fistulas had significantly lower SUVmax compared to grades 2 and 4 (p = 0.0224 and p = 0.0295, respectively). No significant differences existed in SUVmax ratios between anorectal and non-anorectal cancer groups.

CONCLUSION

Perianal fistulas have increased FDG avidity with fistula SUVmax values that are significantly higher than the anal canal.

The routine clinical use of fluorodeoxyglucose PET/CT to confirm treatment response in pyogenic spine infection

OBJECTIVE

Response of pyogenic spine infection to antibiotic therapy is usually based on nonspecific symptoms and inflammation markers. Abnormalities on MRI persist too long to influence therapy. Is FDG-PET/CT a timely and robust predictor of successful therapy?

MATERIALS AND METHODS

Retrospective study. Sequential FDG-PET/CTs done to assess treatment response over a 4-year period. Recurrence of infection after stopping treatment was the endpoint.

RESULTS

One hundred seven patients enrolled. First treatment response scan showed no signs of infection in 69 patients (low risk). Twenty-four additional patients underwent additional treatment after an initial positive scan with low-risk pattern on follow-up imaging. After stopping antibiotics, none had clinical recurrence of infection. One had positive cultures at surgery for negative predictive value of 0.99. Thirty-eight patients had evidence of residual infection. Abnormalities in 28 were comparable to what is seen with untreated infection (high-risk). Twenty-seven received additional treatment until resolution. Antibiotics were stopped in 1 who suffered recurrence. Ten had low-grade/localized abnormalities consistent with infection (intermediate-risk). Signs of infection resolved in 3 after additional treatment. Of the remaining 7 patients who had minor residual abnormalities when antibiotics were stopped, 1 had recurrent infection for a positive predictive value of 0.14.

CONCLUSION

Risk stratification proposed: A low-risk scan with only inflammation at a destroyed joint indicates negligible risk of recurrence. Unexplained activity in bone, soft tissue or spinal canal indicates high risk with further antibiotics recommended. Most patients with subtle or localized findings (intermediate risk) did not experience recurrence. Stopping therapy could be considered under careful observation.

The Role of Antigranulocyte Scintigraphy in Diagnosis of Aortic Graft Infection and Evaluation of Treatment Outcome

BACKGROUND

The aim of this study was to assess the eventual added benefit of antigranulocyte monoclonal antibodies scintigraphy for the diagnostic imaging of aortic graft infection (AGI) and its role in evaluation of treatment outcome.

METHODS

A population-based, retrospective, register-based analysis was carried out of all patients with infected aortic grafts after treatment for aneurysmal or aortoiliac occlusive disease at Karolinska University Hospital, covering the greater Stockholm area during November 2012-December 2020. Cases were based on the definitions in the 2016 Management of Aortic Graft Infection Collaborations consensus. Using the in-hospital electronic patient registry (Take Care®) and the Swedish National Registry for Vascular Surgery (Swedvasc), 835 patients who had been treated for aortic aneurysms or aortoiliac occlusive disease were identified. The diagnostic arsenal of laboratory tests, computed tomography (CT), and clinical signs has been supplemented by antigranulocyte monoclonal antibodies (anti-G mAb) scintigraphy. Data were analyzed using SPSS Statistics.

RESULTS

Eighteen cases of AGI out of 835 operations incorporating aortic grafts during the period were identified. Fourteen patients (78%) were categorized as diagnosed AGI (AGI-D), and the remaining 4 (22%) were classified as suspected AGI (AGI-S). In the AGI-D group (n = 14), 10 patients (71%) had positive CTs and 4 (29%) had low-probability CTs. In the group of 10 positive CTs, 9 patients also had positive scintigraphy scans with only one negative scintigraphy scan. There were no negative scintigraphy scans without ongoing antibiotic treatment at the time of investigation. In 15 of 18 cases, a culprit agent was identified, either preoperatively or perioperatively. Thirteen of the 18 patients were treated solely by antibiotics, whereas 5 underwent surgical treatment in addition to antibiotic treatment. The outcome has been divided into 3 groups: infection-free (n = 6; 33%), lifelong antibiotic treatment (n = 7; 39%), and deceased (n = 5; 28%).

CONCLUSIONS

The imaging modalities in AGI diagnostics are a cornerstone of the investigative work-up, complemented by clinical signs and laboratory methods. The main advantage conveyed by anti-G mAb scintigraphy is in postoperative imaging and its ability to differentiate between infection and general postoperative changes in the areas of concern. We have identified 6 patients in our cohort in whom antibiotic therapy was discontinued after a negative anti-G mAb scintigraphy scan. Anti-G mAb scintigraphy may fulfill a unique need for diagnosis in suspected cases, evaluation of therapeutic efficacy in patients requiring long-term antibiotic treatment, and aiding in the decision to discontinue antibiotic therapy.

Multimodality Imaging Diagnosis in Infective Endocarditis

Imaging is an important tool in the diagnosis and management of infective endocarditis (IE). Echocardiography is an essential examination, especially in native valve endocarditis (NVE), but its diagnostic accuracy is reduced in prosthetic valve endocarditis (PVE). The diagnostic ability is superior for transoesophageal echocardiography (TEE), but a negative test cannot exclude PVE. Both transthoracic echocardiography (TTE) and TEE can provide normal or inconclusive findings in up to 30% of cases, especially in patients with prosthetic devices. New advanced non-invasive imaging tests are increasingly used in the diagnosis of IE. Nuclear medicine imaging techniques have demonstrated their superiority over TEE for the diagnosis of PVE and cardiac implantable electronic device infective endocarditis (CIED-IE). Cardiac computed tomography angiography imaging is useful in PVE cases with inconclusive TTE and TEE investigations and for the evaluation of paravalvular complications. In the present review, imaging tools are described with their values and limitations for improving diagnosis in NVE, PVE and CIED-IE. Current knowledge about multimodality imaging approaches in IE and imaging methods to assess the local and distant complications of IE is also reviewed. Furthermore, a potential diagnostic work-up for different clinical scenarios is described. However, further studies are essential for refining diagnostic and management approaches in infective endocarditis, addressing limitations and optimizing advanced imaging techniques across different clinical scenarios.

Comparison of 18 F-FDG PET Findings of Pegfilgrastim-Induced Aortitis With Other Types of Large-Vessel Vasculitis : A Retrospective Observational Study

PURPOSE OF THE REPORT

To elucidate the PET/CT findings of pegfilgrastim-induced aortitis (PFIA) and compare them with those of other large-vessel vasculitis.

METHODS

We enrolled 45 patients diagnosed with the following: PFIA, n = 8; Takayasu arteritis (TA), n = 12; giant cell arteritis (GCA), n = 6; and immunoglobulin G4-related aortitis (IgG4-A), n = 19. Records of PET/CT performed before treatment initiation were collected. The aorta and its branches were divided into 16 anatomic regions. Presence of abnormal 18 F-FDG uptake in each region was determined and measured.

RESULTS

The 18 F-FDG-positive areas of PFIA were distributed in the regions of the ascending aorta to the suprarenal abdominal aorta, cervical branches of the aorta, and external iliac arteries, similar to those of TA. However, TA had a higher proportion of 18 F-FDG-positive areas than PFIA in almost all anatomic regions. These areas of GCA were widespread throughout the entire aorta and the upper and lower limbs, whereas those of IgG4-A were observed from the abdominal aorta to iliac arteries. SUV max , SUV peak , metabolic volume, and total lesion glycolysis were higher in GCA than in PFIA, TA, and IgG4-A.

CONCLUSIONS

Pegfilgrastim-induced aortitis distribution on PET/CT was frequently observed in the aorta, cervical branches, and extra iliac arteries. The low proportion of 18 F-FDG-positive areas in PFIA was different from that of TA, GCA, and IgG4-A. These findings may help identify and differentiate various aortitis types in clinical practice.

Operational and Performance Experience with uMI550 Digital PET-CT during Routine Quality Control Procedures

Introduction  The quality control (QC) procedures for positron emission tomography (PET) scanners are covered by National Electrical Manufacturers Association and International Electrotechnical Commission. QC must be carried out at regular intervals according to the specifications of the scanner manufacturer. Daily and weekly QC plays a valuable role in monitoring positron emission tomography (PET) scanner performance changes. This study shares operational and performance experience of QC procedures that do not require a radioactive Ge-68 source to perform daily QC and experience with fluorodeoxyglucose F18 ( 18 F-FDG) as a substitute for germanium-68/sodium-22 (Ge-68/Na-22) source for weekly QC. Method  This study was performed on an uMI550 digital positron emission tomography-computed tomography (PET-CT) scanner. In this scanner daily QC checks system temperature and humidity, system count rate, data link status, and voltage. QC was performed at the console control, the position of the scanner table was in the home position pulled out from the gantry, and the room was closed during the quick QC. Weekly full QC check items include look-up table drift, energy drift, time-of-flight status, C-map status, temperature and humidity, and voltage. Weekly full QC was performed with a 18 F-FDG source in a rod phantom source. Results  Over 200 daily QC tests without a radioactive source Ge-68 phantom and 50 full weekly QC tests using a 18 F-FDG rod phantom were performed with this scanner according to the manufacturer's instructions and a test report was generated. No daily QC errors or warnings were observed during this period. Conclusion  The new approach for the daily PET QC does not expose operators to radiation. This translates into commercial and operational merits with consistent performance and results. Implications for Practice  Reduction in radiation exposure to operating staff during QC procedure in PET-CT scanner.

Reappraisal of [18F]FDG-PET/CT for diagnosis and management of cardiac implantable electronic device infections

INTRODUCTION AND OBJECTIVES

The role of [18F]FDG-PET/CT in cardiac implantable electronic device (CIED) infections requires better evaluation, especially in the diagnosis of systemic infections. We aimed to determine the following: a) the diagnostic accuracy of [18F]FDG-PET/CT in each CIED topographical region, b) the added value of [18F]FDG-PET/CT over transesophageal echocardiography (TEE) in diagnosing systemic infections, c) spleen and bone marrow uptake in differentiating isolated local infections from systemic infections, and d) the potential application of [18F]FDG-PET/CT in follow-up.

METHODS

Retrospective single-center study including 54 cases and 54 controls from 2014 to 2021. The Primary endpoint was the diagnostic yield of [18F]FDG-PET/CT in each topographical CIED region. Secondary analyses described the performance of [18F]FDG-PET/CT compared with that of TEE in systemic infections, bone marrow and spleen uptake in systemic and isolated local infections, and the potential application of [18F]FDG-PET/CT in guiding cessation of chronic antibiotic suppression when completed device removal is not performed.

RESULTS

We analyzed 13 (24%) isolated local infections and 41 (76%) systemic infections. Overall, the specificity of [18F]FDG-PET/CT was 100% and sensitivity 85% (79% pocket, 57% subcutaneous lead, 22% endovascular lead, 10% intracardiac lead). When combined with TEE, [18F]FDG-PET/CT increased definite diagnosis o fsystemic infections from 34% to 56% (P=.04). Systemic infections with bacteremia showed higher spleen (P=.05) and bone marrow metabolism (P=.04) than local infections. Thirteen patients without complete device removal underwent a follow-up [18F]FDG-PET/CT, with no relapses after discontinuation of chronic antibiotic suppression in 6 cases with negative follow-up [18F]FDG-PET/CT.

CONCLUSIONS

The sensitivity of [18F]FDG-PET/CT for evaluating CIED infections was high in local infections but much lower in systemic infections. However, accuracy increased when [18F]FDG-PET/CT was combined with TEE in endovascular lead bacteremic infection. Spleen and bone marrow hypermetabolism could differentiate bacteremic systemic infection from local infection. Although further prospective studies are needed, follow-up [18F]FDG-PET/CT could play a potential role in the management of chronic antibiotic suppression therapy when complete device removal is unachievable.

Practice of 18F-FDG-PET/CT in ICU Patients: A Systematic Review

18F-FDG-PET/CT imaging has become a key tool to evaluate infectious and inflammatory diseases. However, application of 18F-FDG-PET/CT in patients in the intensive care unit (ICU) is limited, which is remarkable since the development of critical illness is closely linked to infection and inflammation. This limited use is caused by perceived complexity and risk of planning and executing 18F-FDG-PET/CT in such patients. The aim of this systematic review was to investigate the feasibility of 18F-FDG-PET/CT in ICU patients with special emphasis on patient preparation, transport logistics and safety. Therefore, a systematic search was performed in PubMed, Embase, and Web of Science using the search terms: intensive care, critically ill, positron emission tomography and 18F-FDG or derivates. A total of 1183 articles were found of which 10 were included. Three studies evaluated the pathophysiology of acute respiratory distress syndrome, acute lung injury and acute chest syndrome. Three other studies applied 18F-FDG-PET/CT to increase understanding of pathophysiology after traumatic brain injury. The remaining four studies evaluated infection of unknown origin. These four studies showed a sensitivity and specificity between 85%-100% and 57%-88%, respectively. A remarkable low adverse event rate of 2% was found during the entire 18F-FDG-PET/CT procedure, including desaturation and hypotension. In all studies, a team consisting of an intensive care physician and nurse was present during transport to ensure continuation of necessary critical care. Full monitoring during transport was used in patients requiring mechanical ventilation or vasopressor support. None of the studies used specific patient preparation for ICU patients. However, one article described specific recommendations in their discussion. In conclusion, 18F-FDG-PET/CT has been shown to be feasible and safe in ICU patients, even when ventilated or requiring vasopressors. Specific recommendations regarding patient preparation, logistics and scanning are needed. Including 18F-FDG-PET/CT in routine workup of infection of unknown origin in ICU patients showed potential to identify source of infection and might improve outcome.

The Development and Validation of Radiopharmaceuticals Targeting Bacterial Infection

The International Atomic Energy Agency organized a technical meeting at its headquarters in Vienna, Austria, in 2022 that included 17 experts representing 12 countries, whose research spanned the development and use of radiolabeled agents for imaging infection. The meeting focused largely on bacterial pathogens. The group discussed and evaluated the advantages and disadvantages of several radiopharmaceuticals, as well as the science driving various imaging approaches. The main objective was to understand why few infection-targeted radiotracers are used in clinical practice despite the urgent need to better characterize bacterial infections. This article summarizes the resulting consensus, at least among the included scientists and countries, on the current status of radiopharmaceutical development for infection imaging. Also included are opinions and recommendations regarding current research standards in this area. This and future International Atomic Energy Agency-sponsored collaborations will advance the goal of providing the medical community with innovative, practical tools for the specific image-based diagnosis of infection.

Variability of [18F]FDG-PET/LDCT reporting in vascular graft and endograft infection

PURPOSE

18F-fluoro-D-deoxyglucose positron emission tomography with low dose and/or contrast enhanced computed tomography ([18F]FDG-PET/CT) scan reveals high sensitivity for the diagnosis of vascular graft and endograft infection (VGEI), but lower specificity. Reporting [18F]FDG-PET/CT scans of suspected VGEI is challenging, reader dependent, and reporting standards are lacking. The aim of this study was to evaluate variability of [18F]FDG-PET/low dose CT (LDCT) reporting of suspected VGEI using a proposed standard reporting format.

METHODS

A retrospective cohort study was conducted including all patients with a suspected VGEI (according to the MAGIC criteria) without need for urgent surgical treatment who underwent an additional [18F]FDG-PET/LDCT scan between 2006 and 2022 at a tertiary referral centre. All [18F]FDG-PET/LDCT reports were scored following pre-selected criteria that were formulated based on literature and experts in the field. The aim was to investigate the completeness of [18F]FDG-PET/LDCT reports for diagnosing VGEI (proven according to the MAGIC criteria) and to evaluate if incompleteness of reports influenced the diagnostic accuracy.

RESULTS

Hundred-fifty-two patients were included. Median diagnostic interval from the index vascular surgical procedure until [18F]FDG-PET/LDCT scan was 35.5 (7.3-73.3) months. Grafts were in 65.1% located centrally and 34.9% peripherally. Based on the pre-selected reporting criteria, 45.7% of the reports included all items. The least frequently assessed criterion was FDG-uptake pattern (40.6%). Overall, [18F]FDG-PET/LDCT showed a sensitivity of 91%, a specificity of 72%, and an accuracy of 88% when compared to the gold standard (diagnosed VGEI). Lower sensitivity and specificity in reports including ≤ 8 criteria compared to completely evaluated reports were found (83% and 50% vs. 92% and 77%, respectively).

CONCLUSION

Less than half of the [18F]FDG-PET/LDCT reports of suspected VGEI met all pre-selected criteria. Incompleteness of reports led to lower sensitivity and specificity. Implementing a recommendation with specific criteria for VGEI reporting is needed in the VGEI-guideline update. This study provides a first recommendation for a concise and complete [18F]FDG-PET/LDCT report in patients with suspected VGEI.

SARS-CoV-2 Affects Thyroid and Adrenal Glands: An 18F-FDG PET/CT Study

BACKGROUND

Since most endocrine glands express ACE-2 receptors and can be infected by SARS-CoV-2 virus, this retrospective multicentre observational study aims to assess the metabolic activity of thyroid and adrenal glands of COVID-19 patients by 18F-FDG PET/CT.

METHODS

We retrospectively evaluated the 18F-FDG PET/CT scans of COVID-19 patients admitted by three different centres, either in a low-intensity department or in the intensive care unit (ICU). A visual assessment and a semi-quantitative evaluation of areas of interest in thyroid and adrenal glands were performed by recording SUVmax and SUVmean. The 18F-FDG PET/CT uptake in COVID-19 patients was compared with those observed in normal age-matched controls.

RESULTS

Between March 2020 and March 2022, 33 patients from three different centres (twenty-eight patients in a low-intensity department and five patients in ICU), were studied by 18F-FDG PET/CT during active illness. Seven of them were also studied after clinical remission (3-6 months after disease onset). Thirty-six normal subjects were used as age-matched controls. In the thyroid gland, no statistically significant differences were observed between control subjects and COVID-19 patients at diagnosis. However, at the follow-up PET/CT study, we found a statistically higher SUVmax and SUVmean (p = 0.009 and p = 0.004, respectively) in the thyroid of COVID-19 patients. In adrenal glands, we observed lower SUVmax and SUVmean in COVID-19 patients at baseline compared to control subjects (p < 0.0001) and this finding did not normalize after clinical recovery (p = 0.0018 for SUVmax and p = 0.002 for SUV mean).

CONCLUSIONS

In our series, we observed persistent low 18F-FDG uptake in adrenal glands of patients at diagnosis of COVID-19 and after recovery, suggesting a chronic hypofunction. By contrast, thyroid uptake was comparable to normal subjects at disease onset, but after recovery, a subgroup of patients showed an increased metabolism, thus possibly suggesting the onset of an inflammatory thyroiditis. Our results should alert clinicians to investigate the pituitary-adrenal axis and thyroid functionality at the time of infection and to monitor them after recovery.

Rheumatology experience with FDG PET / CT in inflammation of unknown origin: a single - centre report for determining factors associated with diagnostic precision

BACKGROUND / AIM: The use of PET / CT is becoming more common in the elucidation of inflammatory processes in which the underlying cause cannot be determined by conventional examinations. Although PET / CT is an effective method for detecting inflammatory foci, the precise diagnosis may not be obtained in all cases. In addition, considering factors such as radiation exposure and cost, it becomes important to identify patients who can get results with PET / CT. In this study, it was aimed to examine the factors that can predict the differential diagnostic value of PET / CT by retrospectively scanning patients who underwent PET / CT for inflammation of unknown origin (IUO) in rheumatology practice.

METHODS

Demographic, clinical and laboratory information of the patients followed up in our clinic and who underwent PET / CT for differential diagnosis were enrolled. Whether they were diagnosed after PET / CT and during the follow - up period, and their diagnoses were examined.

RESULTS

A total of 132 patients were included in the study. A previous diagnosis of rheumatic disease was present in 28.8 % of the patients, and a history of malignancy was present in 2.3 % . The patients were divided into three groups: group 1 patients with increased FDG uptake in PET / CT and diagnosis confirmed by PET / CT, group 2 patients with increased FDG uptake in PET / CT but diagnosis was not confirmed, and group 3 patients without increased FDG uptake in PET / CT. Increased FDG uptake in PET / CT was detected in 73 % of the patients. While PET / CT helped the diagnosis in 47 (35.6 %) patients (group 1), it did not help the diagnosis in 85 (64.4 %) (groups 2 and 3). Thirty - one (65.9 %) of the diagnosed patients were diagnosed with a rheumatologic disease. When the 3 groups were compared, male gender, advanced age, CRP levels, presence of constitutional symptoms, SUVmax values and number of different organs with increased FDG uptake were higher in Group 1. Sixty - six percent and 74 % of the patients in groups 2 and 3 were not diagnosed during the follow - up period. No patient in group 3 was diagnosed with malignancy during follow - up.

CONCLUSION

PET / CT has high diagnostic value when combined with clinical and laboratory data in the diagnosis of IUO. Our study revealed that various factors can affect the diagnostic value of PET / CT. Similar to the literature, the statistically significant difference in CRP levels shows that patients with high CRP levels are more likely to be diagnosed with an aetiology in PET / CT. Although detection of involvement in PET / CT is not always diagnostic, there was an important finding that no malignancy was detected in the follow - up in any patient without PET / CT involvement. Key points • PET / CT is an effective method for detecting inflammatory foci. • PET / CT has proven to be effective in the diagnosis of rheumatological diseases, the extent of disease and the evaluation of response to treatment. • Indications for the use of PET / CT in the field of rheumatology and the associated factors and clinical features supporting the diagnosis with PET / CT are still to be fully clarified. • In routine practice, with PET / CT, both delays in diagnosis and examinations performed during diagnosis and the cost can be reduced.

Development of lung cancer risk prediction models based on F-18 FDG PET images

OBJECTIVE

We aimed to evaluate whether the degree of F-18 fluorodeoxyglucose (FDG) uptake in the lungs is associated with an increased risk of lung cancer and to develop lung cancer risk prediction models using metabolic parameters on F-18 FDG positron emission tomography (PET).

METHODS

We retrospectively included 795 healthy individuals who underwent F-18 FDG PET/CT scans for a health check-up. Individuals who developed lung cancer within 5 years of the PET/CT scan were classified into the lung cancer group (n = 136); those who did not were classified into the control group (n = 659). The healthy individuals were then randomly assigned to either the training (n = 585) or validation sets (n = 210). Clinical factors including age, sex, body mass index (BMI), and smoking history were collected. The standardized uptake value ratio (SUVR) and metabolic heterogeneity (MH) index were obtained for the bilateral lungs. Logistic regression models including clinical factors, SUVR, and MH index were generated to quantify the probability of lung cancer development using a training set. The prediction models were validated using a validation set.

RESULTS

The lung SUVR and lung MH index in the lung cancer group were significantly higher than in the control group (p < 0.001 and p < 0.001, respectively). In the combined prediction model 1, age, sex, BMI, smoking history, and lung SUVR were significantly associated with lung cancer development (age: OR 1.07, p < 0.001; male: OR 2.08, p = 0.015; BMI: OR 0.93, p = 0.057; current or past smoker: OR 5.60, p < 0.001; lung SUVR: OR 1.13, p < 0.001). In the combined prediction model 2, age, sex, BMI, smoking history, and lung MH index showed a significant association with lung cancer development (age: OR 1.06, p < 0.001; male: OR 1.87, p = 0.045; BMI: OR 0.93, p = 0.010; current or past smoker: OR 4.78, p < 0.001; lung MH index: OR 1.33, p < 0.001). In the validation data, combined prediction models 1 and 2 exhibited very good discrimination [area under the receiver operator curve (AUC): 0.867 and 0.901, respectively].

CONCLUSIONS

The metabolic parameters on F-18 FDG PET are related to an increased risk of lung cancer. Metabolic parameters can be used as biomarkers to provide information independent of the clinical parameters, related to lung cancer risk.

How to combine CTA, 99mTc-WBC SPECT/CT, and [18F]FDG PET/CT in patients with suspected abdominal vascular endograft infections?

PURPOSE

We aimed at comparing 99mTc-HMPAO white blood cells (99mTc-WBC) scintigraphy, 18fluorine-fluorodeoxyglucose ([18F]FDG) positron emission tomography/computed tomography (PET/CT) and CT angiography (CTA) in patients with suspected abdominal vascular graft or endograft infection (VGEI). Moreover, we attempted to define a new visual score for interpreting [18F]FDG PET/CT scans aiming at increasing its specificity.

METHODS

We prospectively compared 99mTc-WBC SPECT/CT, [18F]FDG PET/CT, and CTA in 26 patients with suspected abdominal VGEI. WBC scans were performed and interpreted according to EANM recommendations. [18F]FDG PET/CT studies were assessed with both qualitative (Sah's scale and new visual score) and semi-quantitative analyses. CTA images were interpreted according to MAGIC criteria. Microbiology, histopathology or a clinical follow-up of at least 24 months were used to achieve final diagnosis.

RESULTS

Eleven out of 26 patients were infected. [18F]FDG PET/CT showed 100% sensitivity and NPV, with both scoring systems, thus representing an efficient tool to rule out the infection. The use of a more detailed scoring system provided statistically higher specificity compared to the previous Sah's scale (p = 0.049). 99mTc-WBC SPECT/CT provided statistically higher specificity and PPV than [18F]FDG PET/CT, regardless the interpretation criteria used and it can be, therefore, used in early post-surgical phases or to confirm or rule out a PET/CT finding.

CONCLUSIONS

After CTA, patients with suspected late VGEI should perform a [18F]FDG PET/CT given its high sensitivity and NPV. However, given its lower specificity, positive results should be confirmed with 99mTc-WBC scintigraphy. The use of a more detailed scoring system reduces the number of 99mTc-WBC scans needed after [18F]FDG PET/CT. Nevertheless, in suspected infections within 4 months from surgery, 99mTc-WBC SPECT/CT should be performed as second exam, due to its high accuracy in differentiating sterile inflammation from infection.

Appearance of aseptic vascular grafts after endovascular aortic repair on [(18)F]fluorodeoxyglucose positron emission tomography/computed tomography

BACKGROUND

Diagnosis of prosthetic vascular graft infection with [(18)F]fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) allows for early detection of functional changes associated with infection, based on increased glucose utilization by activated macrophages and granulocytes. Aseptic vascular grafts, like all foreign bodies, can stimulate an inflammatory response, which can present as increased activity on 18F-FDG PET/CT. Consequently, distinguishing aseptic inflammation from graft infection, though important, can be difficult. In the case of endovascular aneurysm repair (EVAR), a minimally invasive procedure involving the transfemoral insertion of an endoprosthetic stent graft, the normal postoperative appearance of these grafts on 18F-FDG PET/CT can vary over time, potentially confounding study interpretation.

AIM

To investigate the visual, semiquantitative, and temporal characteristics of aseptic vascular grafts in patients status post EVAR.

METHODS

In this observational retrospective cohort study, patients with history of EVAR who underwent 18F-FDG PET/CT for indications other than infection were identified retrospectively. All patients were asymptomatic for graft infection - no abdominal pain, fever of unknown origin, sepsis, or leukocytosis - at the time of imaging and for ≥ 2 mo after each PET/CT. Imaging studies such as CT for each patient were also reviewed, and any patients with suspected or confirmed vascular graft infection were excluded. One hundred two scans performed on 43 patients (34 males; 9 females; age = 77 ± 8 years at the time of the final PET/CT) were retrospectively reviewed. All 43 patients had an abdominal aortic (AA) vascular graft, 40 patients had a right iliac (RI) limb graft, and 41 patients had a left iliac (LI) limb graft. Twenty-two patients had 1 PET/CT and 21 patients had from 2 to 9 PET/CTs. Grafts were imaged between 2 mo to 168 mo (about 14 years) post placement. Eight grafts were imaged within 6 mo of placement, including three that were imaged within three months of placement. The mean interval between graft placement and PET/CT for all 102 scans was 51 ± 39 mo. PET/CT data was reconstructed with region-of-interest analysis of proximal, mid and distal portions of the grafts and background ascending aorta. Maximum standardized uptake value (SUVmax) was recorded for each region. SUVmax-to-background uptake ratios (URs) were calculated. Visual assessment was performed using a 2-pattern grading scale: Diffuse (homogeneous uptake less than liver uptake) and focal (one or more areas of focal uptake in any part of the graft). Statistical analysis was performed.

RESULTS

In total, there were 306 AA grafts, 285 LI grafts, 282 RI grafts, and 306 ascending aorta background SUVmax measurements. For all 102 scans, mean SUVmax values for AA grafts were 2.8-3.0 along proximal, mid, and distal segments. Mean SUVmax values for LI grafts and RI grafts were 2.7-2.8. Mean SUVmax values for background were 2.5 ± 0.5. Mean URs were 1.1-1.2. Visual analysis of the scans reflected results of quantitative analysis. On visual inspection, 98% revealed diffuse, homogeneous 18F-FDG uptake less than liver. Graft URs and visual pattern categories were significantly associated for AA graft URs (F-ratio = 21.5, P < 0.001), LI graft URs (F-ratio = 20.4, P < 0.001), and RI graft URs (F-ratio = 30.4, P < 0.001). Thus, visual patterns of 18F-FDG uptake corresponded statistically significantly to semiquantitative URs. The age of grafts showing focal patterns was greater than grafts showing diffuse patterns, 87 ± 89 vs 50 ± 37 mo, respectively (P = 0.02). URs were significantly associated with graft age for AA grafts (r = 0.19, P = 0.001). URs were also significantly associated with graft age for LI grafts (r = 0.25, P < 0.0001), and RI grafts (r = 0.31, P < 0.001). Quartiles of similar numbers of graft (n = 25-27) grouped by graft age indicated that URs were significantly higher for 4th quartile vs 2nd quartile URs (F-ratio = 19.5, P < 0.001). When evaluating URs, graft SUVmax values within 10%-20% of the ascending aorta SUVmax is evident in aseptic grafts, except for grafts in the oldest quartiles. In this study, grafts in the oldest quartiles (> 7 years post EVAR) showed SUVmax up to 30% higher than the ascending aorta SUVmax.

CONCLUSION

Characteristics of an aseptic vascular stent graft in the aorta and iliac vessels on 18F-FDG PET/CT include graft SUVmax values within 10%-20% of the ascending aorta background SUVmax. The SUVmax of older aseptic grafts can be as much as 30% above background. The visual uptake pattern of diffuse, homogeneous uptake less than liver was seen in 98% of aseptic vascular grafts, making this pattern particularly reassuring for clinicians.

Myocardial Functional Imaging in Pediatric Nuclear Cardiology

The role of nuclear medicine in pediatric cardiology has grown rapidly over the years, providing useful functional and prognostic information and playing a complementary role to morphological imaging in the evaluation of myocardial perfusion, cardiovascular inflammation and infections, and cardiac sympathetic innervation. The aim of this narrative review is to summarize and highlight the most important evidence on pediatric nuclear cardiology, describing clinical applications and the possibilities, advantages, and limitations of nuclear medicine techniques. Moreover, a special focus will be given to the minimization of radiation exposure in pediatric nuclear cardiology imaging, a critical topic in children.

FDG PET in Evaluation of Patients With Fever of Unknown Origin: AJR Expert Panel Narrative Review

Fever of unknown origin (FUO) is a diagnostic challenge, with its cause remaining undiagnosed in approximately half of patients. Nuclear medicine tests typically are performed after a negative or inconclusive initial workup. Gallium-67 citrate and labeled leukocytes were previous mainstays of radionuclide imaging for FUO, although they had limited diagnostic performance. FDG PET/CT has subsequently emerged as the nuclear medicine imaging test of choice, supported by a growing volume of evidence. A positive FDG PET/CT result contributes useful information by identifying potential causes of fever, localizing sites for further evaluation, and guiding further management; a negative result contributes useful information by excluding focal disease as the cause of fever and predicts a favorable prognosis. In 2021, CMS rescinded a prior national noncoverage determination for FDG PET for infection and inflammation, leading to increasing national utilization of FDG PET/CT for FUO workup. This article reviews the current status of the role of FDG PET/CT in the evaluation of patients with FUO. The literature reporting the diagnostic performance and yield of FDG PET/CT in FUO workup is summarized, with comparison with historically used nuclear medicine tests included. Attention is also given to the test's clinical impact; protocol, cost, and radiation considerations; and application in children.

The Role of Multimodality Imaging in Pediatric Cardiomyopathies

Cardiomyopathies are a heterogeneous group of myocardial diseases representing the first cause of heart transplantation in children. Diagnosing and classifying the different phenotypes can be challenging, particularly in this age group, where cardiomyopathies are often overlooked until the onset of severe symptoms. Cardiovascular imaging is crucial in the diagnostic pathway, from screening to classification and follow-up assessment. Several imaging modalities have been proven to be helpful in this field, with echocardiography undoubtedly representing the first imaging approach due to its low cost, lack of radiation, and wide availability. However, particularly in this clinical context, echocardiography may not be able to differentiate from cardiomyopathies with similar phenotypes and is often complemented with cardiovascular magnetic resonance. The latter allows a radiation-free differentiation between different phenotypes with unique myocardial tissue characterization, thus identifying the presence and extent of myocardial fibrosis. Nuclear imaging and computed tomography have a complementary role, although they are less used in daily clinical practice due to the concern related to the use of radiation in pediatric patients. However, these modalities may have some advantages in evaluating children with cardiomyopathies. This paper aims to review the strengths and limitations of each imaging modality in evaluating pediatric patients with suspected or known cardiomyopathies.

Time-Related Vascular Inflammatory Response to COVID-19 Assessed by 18F-FDG PET/CT in Follow-Up Tumor Patients

Purpose

This study aimed to assess COVID-19's effects on vascular inflammatory response, by evaluating 18-Fluorodeoxyglucose (¹⁸F-FDG) uptake via positron emission tomography/computed tomography (PET/CT) in the artery of diffuse large B cell lymphoma (DLBCL) patients before and after infection with COVID-19.

Patients and Methods

Thirty-five DLBCL patients administered the chemotherapy regimen R-CHOP and examined by oncological ¹⁸F-FDG PET/CT imaging twice from August 2022 to February 2023 for pre-treatment evaluation or assessment of treatment efficacy were enrolled. Seventeen patients were confirmed with COVID-19 within the study period. Arterial wall FDG uptake was semi-quantitatively analyzed as TBR (target-to-blood pool ratio) in 14 different vascular regions using oncological ¹⁸F-FDG PET/CT. Based on COVID-19 course and the two PET/CT scans, we further analyzed time-related FDG uptake for vascular walls in DLBCL patients with COVID-19.

Results

Arterial TBRs were higher in the last PET/CT examination than previous ones in all patients with or without COVID-19. Besides the ascending aorta, ΔTBR (last PET/CT scanning's TBR minus previous PET/CT scanning's TBR) were not significantly different between the COVID-19 and Control groups. However, cases scanned ≤30 days from infection had remarkably higher ΔTBRs in comparison with those assessed >30 days post-infection in the COVID-19 group (p<0.05). A moderate inverse correlation was observed between ∆Global TBR (last PET/CT scanning's average TBR value minus previous PET/CT scanning's average TBR value) and time distance from COVID-19 onset to ¹⁸F-FDG PET/CT scan (Spearman's rho=-0.591, P=0.012). Interestingly, there were no differences of changes of TBR between different purpose of PET/CT examination group.

Conclusion

This work firstly suggested vascular inflammation is elevated in the early post-COVID-19 phase in DLBCL cases compared with prolonged post-COVID-19 phase or controls. Increasing attention should be paid to these patients and the protection of their vascular function and complications in early COVID-19.

Determining the usefulness of systematic 18F-FDG PET/CT for the management of invasive fungal infection (PETIFI project): a prospective national multicentre cohort study protocol

INTRODUCTION

The evaluation of staging and activity of invasive fungal infection (IFI) is used to adjust the type and duration of antifungal therapy (AT). Typically anatomy-based imaging is used. Positron emission tomography/CT with 18F-fluorodeoxyglucose (18F-FDG PET/CT) not only evaluates more than one body area in one session, but adds functional information to the anatomic data provided by usual imaging techniques and can potentially improve staging of IFI and monitoring of the response to therapy. Our objective is to analyse the impact of the systematic use of 18F-FDG PET/CT in IFI diagnostic and therapeutic management.

METHODS AND ANALYSIS

Multicentre prospective cohort study of IFI with performance of systematic 18F-FDG PET/CT at diagnosis and follow-up that will be carried out in 14 Spanish tertiary hospitals. It is planned to include 224 patients with IFI over a 2-year study period. Findings and changes in management before and after 18F-FDG PET/CT will be compared. Additionally, the association of initial quantitative 18F-FDG PET/CT parameters with response to therapy will be evaluated.The primary endpoint is to compare the yield of 18F-FDG PET/CT with standard management without 18F-FDG PET/CT in IFI at initial assessment (staging) and in monitoring the response to treatment.The impact of the results of 18F-FDG PET/CT on the diagnostic-therapeutic management of patients with IFI (added value), as well as the prognostic ability of different quantification parameters of 18F-FDG PET/CT will be secondary endpoints.

ETHICS AND DISSEMINATION

The Clinical Research Ethics Committee of Puerta de Hierro-Majadahonda University Hospital approved the protocol of the study at the primary site. We plan to publish the results in high-impact journals.

TRIAL REGISTRATION NUMBER

NCT05688592.

18F-FDG/PET-CT imaging findings after sternotomy

BACKGROUND

The clinical diagnosis of deep sternal wound infection (DSWI) is supported by imaging findings including 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG-PET/CT). To avoid misinterpretation due to normal post-surgery inflammation we assessed normal imaging findings in non-infected patients after sternotomy.

METHODS

This is a prospective cohort study including non-infectious patients with sternotomy. All patients underwent 18F-FDG-PET/CT at either 5 weeks (group 1), 12 weeks (group 2) or 52 weeks (group 3) post-surgery. 18F-FDG uptake was scored visually in five categories and assessed quantitatively.

RESULTS

A total of 44 patients were included. Sternal mean SUVmax was 7.34 (± 1.86), 5.22 (± 2.55) and 3.20 (± 1.80) in group 1, 2 and 3, respectively (p < 0.01). Sternal mean SUVmean was 3.84 (± 1.00), 2.69 (± 1.32) and 1.71 (± 0.98) in group 1, 2 and 3 (p < 0.01). All patients in group 1 had elevated uptake whereas group 2 and 3 showed 2/15 (13%) and 11/20 (55%) patients respectively with no elevated uptake. Group 3 still showed an elevated uptake pattern in in 9/20 (45%) and in 3/9 (33%) with a high-grade diffuse uptake pattern.

CONCLUSION

This study shows significant lower sternal 18F-FDG at 55 weeks compared to 5 weeks post-sternotomy however elevated uptake patterns may persist.

Investigating the potential added value of [ 18 F]FDG-PET/CT in long COVID patients with persistent symptoms: a proof of concept study

OBJECTIVE

Since the end of 2019, the coronavirus disease 2019 (COVID-19) virus has infected millions of people, of whom a significant group suffers from sequelae from COVID-19, termed long COVID. As more and more patients emerge with long COVID who have symptoms of fatigue, myalgia and joint pain, we must examine potential biomarkers to find quantifiable parameters to define the underlying mechanisms and enable response monitoring. The aim of this study is to investigate the potential added value of [ 18 F]FDG-PET/computed tomography (CT) for this group of long COVID patients.

METHODS

For this proof of concept study, we evaluated [ 18 F]FDG-PET/CT scans of long COVID patients and controls. Two analyses were performed: semi-quantitative analysis using target-to-background ratios (TBRs) in 24 targets and total vascular score (TVS) assessed by two independent nuclear medicine physicians. Mann-Whitney U -test was performed to find significant differences between the two groups.

RESULTS

Thirteen patients were included in the long COVID group and 25 patients were included in the control group. No significant differences ( P  < 0.05) were found between the long COVID group and the control group in the TBR or TVS assessment.

CONCLUSION

As we found no quantitative difference in the TBR or TVS between long COVID patients and controls, we are unable to prove that [ 18 F]FDG is of added value for long COVID patients with symptoms of myalgia or joint pain. Prospective cohort studies are necessary to understand the underlying mechanisms of long COVID.

Anthracycline cardiotoxicity: current methods of diagnosis and possible role of 18F-FDG PET/CT as a new biomarker

Despite advances in chemotherapy, the drugs used in cancer treatment remain rather harmful to the cardiovascular system, causing structural and functional cardiotoxic changes. Positron-emission tomography associated with computed tomography (PET/CT) has emerged like a promising technique in the early diagnosis of these adverse drug effects as the myocardial tissue uptake of fluorodeoxyglucose labeled with fluorine-18 (¹⁸F-FDG), a glucose analog, is increased after their use. Among these drugs, anthracyclines are the most frequently associated with cardiotoxicity because they promote heart damage through DNA breaks, and induction of an oxidative, proinflammatory, and toxic environment. This review aimed to present the scientific evidence available so far regarding the use of ¹⁸F-FDG PET/CT as an early biomarker of anthracycline-related cardiotoxicity. Thus, it discusses the physiological basis for its uptake, hypotheses to justify its increase in the myocardium affected by anthracyclines, importance of ¹⁸F-FDG PET/CT findings for cardio-oncology, and primary challenges of incorporating this technique in standard clinical oncology practice.

The value of FDG-PET/CT imaging in the assessment, monitoring, and management of COVID-19

The pathogenesis of Coronavirus Disease 2019 (COVID-19) involves cytokine-driven recruitment and accumulation of inflammatory cells at sites of infection. These activated neutrophils, monocytes, and effector T cells are highly glycolytic and thus appear as [18]F-labeled fluorodeoxyglucose (FDG) avid sites on positron emission tomography (PET) imaging. FDG-PET-computed tomography (FDG-PET/CT) is a highly sensitive modality for the detection, monitoring, and assessing response related to COVID-19 disease activity that holds significant clinical relevance. To date, concerns over cost, access, and undue radiation exposure have limited the use of FDG-PET/CT in COVID-19 to a small number of individuals where PET-based interventions were already indicated. In this review, we summarize the existing literature on the use of FDG-PET in the detection and monitoring of COVID-19 with particular focus on several areas of clinical relevance that warrant future research: (1) incidental early detection of subclinical COVID-19 in patients who have undergone FDG-PET for other underlying diseases, (2) standardized quantitative assessment of COVID-19 disease burden at specific points in time, and (3) analysis of FDG-PET/CT data leading to better characterization of COVID-19 pathogenesis. Employing FDG-PET/CT for these purposes may allow for the earliest detection of COVID-19-associated venous thromboembolism (VTE), standardized monitoring of disease progression and response to treatment, and better characterization of the acute and chronic complications of this disease.

Is Imaging Bacteria with PET a Realistic Option or an Illusion?

The application of [¹⁸F]-fluorodeoxyglucose ([¹⁸F]FDG) as a radiotracer to detect sites of inflammation (either due to bacterial infection or primary inflammation) has led to exploring the role of PET in visualizing bacteria directly at sites of infection. However, the results from such efforts are controversial and inconclusive so far. We aimed to assess the limitations of PET as an effective modality in the diagnosis of bacterial infections. Inflammation due to bacterial infections can be visualized by using [¹⁸F]FDG-PET. However, the non-specificity of [¹⁸F]FDG makes it undesirable to visualize bacteria as the underlying cause of inflammation. Hence, more specific radiotracers that possibly bind to or accumulate in bacteria-specific receptors or enzymes are being explored. Several radiotracers, including 2-deoxy-2-[¹⁸F]fluorosorbitol ([¹⁸F]FDS), 6-[¹⁸F]-fluoromaltose, [¹¹C]para-aminobenzoic acid ([¹¹C]PABA), radiolabeled trimethoprim (¹¹C-TMP) and its analog fluoropropyl-trimethoprim (¹⁸F-FPTMP), other radiolabeled sugars, and antimicrobial drugs have been used to image microorganisms. Unfortunately, no progress has been made in translating the results to routine human use; feasibility and other factors have constrained their success in clinical settings. In the current article, we discuss the limitations of direct bacterial visualization with PET tracers, but emphasize the important role of [¹⁸F]FDG-PET as the only option for detecting evidence of infection.

Radionuclide Imaging of Infective Endocarditis

Infective endocarditis (IE) is associated with high morbidity and mortality. Early diagnosis is crucial for adequate patient management. Due to difficulties in the diagnosis, a multidisciplinary discussion in addition to the integration of clinical signs, microbiology data, and imaging data is used. Imaging, including echocardiography, molecular imaging techniques, and coronary CT angiography (CTA) is central to detect infections involving heart valves and implanted cardiovascular devices, also allowing for early detection of septic emboli and metastatic. This article describes the main clinical application of white blood cell SPECT/CT and [¹⁸F]FDG-PET/CT and CTA in IE and infections associated with cardiovascular implantable electronic devices.

Imaging of Endocarditis and Cardiac Device-Related Infections: An Update

IE is a deadly disease requiring prompt diagnosis for adequate patient's management. The diagnosis requires the integration of clinical signs, microbiology data and imaging data and proper discussion within a multidisciplinary team, the endocarditis team. Since the introduction of ¹⁸F-FDG-PET/CT and WBC SPECT/CT in the diagnostic algorithm of PVE the nuclear medicine imaging specialists is active part of the Endocarditis Team, requiring proper knowledge of dedicated imaging acquisition protocols, expertise for imaging reading and interpretations to select the best test or combination of tests for each specific clinical situation. In this manuscript, we will review the main technical aspects of each imaging procedure, the most recent literature with specific regards to special challenging populations and provide clinical examples.

Update on Imaging of Inflammatory Arthritis and Related Disorders

Arthritis and other rheumatic disorders are very frequent in the general population and responsible for a huge physical and disability burden to affected patients as well as a major cost to the society. Precise evaluation often relies on clinical data only but additional imaging may be required i) for a more objective assessment of the disease status, such as in rheumatoid arthritis (RA) or ankylosing spondyloarthritis (AS), ii) for providing prognostic information and evaluating response to treatment or iii) for establishing diagnosis, in patients with unclear clinical picture, such as polymyalgia rheumatica (PMR) and large-vessel vasculitis (LVV). Besides radiological techniques (x-rays, ultrasound, and MRI), functional and molecular imaging has emerged as a valid tool for this purpose in several disorders. Bone scanning has long been a method of choice but is now more used as a triage tool in patients with unclear complaints, including degenerative disorders (eg osteoarthritis). ¹⁸F-FDG-PET/CT (FDG) proved efficient in assessing the extent of the disease and response to treatment in RA and related disorders, and to provide accurate diagnosis in some systemic disorders, including PMR and LVV. Based on glucose metabolism, FDG-PET/CT is able to show increased metabolism in peripheral cells involved in inflammation (eg neutrophils, lymphocytes or monocytes/macrophages) but also in fibroblasts that proliferate in the pannus. The lack of specificity of FDG is a limitation and many alternative tracers were developed at the preclinical stage or applied in the clinics, especially within clinical trials. They include imaging of macrophages using translocator protein (TSPO), folate-receptors or other targets on activated cells. These new tools will undoubtedly become more and more available in the everyday clinical workup of patients with rheumatisms. Finally, it should be kept in mind that a very simple tracer, ¹⁸F-fluoride is widely more performant in AS than FDG.

Molecular Imaging in Inflammatory Bowel Disease

Inflammatory bowel diseases (IBD) are chronic immune-mediated inflammatory diseases affecting the gastrointestinal tract. Classically, two subtypes of IBD are recognized: Ulcerative colitis and Crohn's disease. There is not a single and reliable test for IBD diagnosis but the nuclear medicine techniques like ^99mTc-HMPAO autologous labelled leukocytes scintigraphy (WBCS) and PET/CT plays a role in the management of IBD. Leukocytes can be labelled "in vitro" (using ^99mTc-HMPAO in Europe or ¹¹¹In-oxine in America) or "in vivo" using antigranulocyte monoclonal antibodies. Nuclear medicine techniques are not the first choice to investigate IBD. Ultrasonography and magnetic resonance (radiation free) are probably the first option, and the diagnosis is commonly established by endoscopic biopsies. Nevertheless, WBCS is highly sensitive and accurate and represent a real option when other methods cannot used for whatever reason. In fact, a normal scan discards the presence of active IBD. The test is also useful to measure the extension and severity of the diseases and to evaluate the response to treatment. PET/CT imaging using ¹⁸F-FDG has recently been introduced and studied in both children and adults showing an excellent sensitivity for detecting active intestinal inflammation, but poor specificity in some studies. PET alone appears to be sufficient for the evaluation of ulcerative colitis, but PET/CT provides considerably more information than PET alone in the evaluation of Crohn's disease. Current clinical applications of PET in IBD include its use in the early evaluation of IBD, especially in children who may not tolerate an invasive test such as colonoscopy. Many questions remain to be answered, but PET appears to be a promising tool in the non-invasive evaluation of IBD. On the other hand, PET/MR could become in the near future a powerful tool in the evaluation of IBD patients. In addition, immuno-PET with antibodies targeting innate immune markers is also being investigated to detect colonic inflammation. The development of these technologies in humans could offer a less invasive method than endoscopy for the diagnosis and monitoring of IBD.

PET/MR imaging of inflammation in atherosclerosis

Myocardial infarction, stroke, mental disorders, neurodegenerative processes, autoimmune diseases, cancer and the human immunodeficiency virus impact the haematopoietic system, which through immunity and inflammation may aggravate pre-existing atherosclerosis. The interplay between the haematopoietic system and its modulation of atherosclerosis has been studied by imaging the cardiovascular system and the activation of haematopoietic organs via scanners integrating positron emission tomography and resonance imaging (PET/MRI). In this Perspective, we review the applicability of integrated whole-body PET/MRI for the study of immune-mediated phenomena associated with haematopoietic activity and cardiovascular disease, and discuss the translational opportunities and challenges of the technology.

Relationships Between Systemic Inflammatory Markers and 18F-FDG PET/CT Imaging and Clinical Findings in Pulmonary Sarcoidosis

Background and aim Sarcoidosis is a multisystem inflammatory disease of unknown aetiology. This study aimed to evaluate the relationship between systemic inflammatory parameters, the systemic immune-inflammation index (SII) and the lymphocyte-to-monocyte ratio (LMR), and disease stage, clinical findings, and 18F-fluoro-2-deoxy-D-glucose (18F-FDG) tomography/computed tomography (PET/CT) uptake. Materials and methods Our study included 73 patients. The general characteristics, radiological features, spirometric tests, PET/CT findings, and laboratory parameters of the patients were recorded. Results Relapse and parenchymal fibrosis were not associated with metabolic parameters, such as LMR and SII. Serum angiotensin-converting enzyme (ACE) levels were lower in the relapsed group than in the non-relapse group. However, the patients' PET/CT images indicated that 18F-FDG parenchym maximum standard uptake value (SUV max), lymph node SUV max, lymph node short axis dimension, SII, and LMR were similar between all patients, relapsed or not. Conclusion Although found to be significant in other inflammatory diseases, we found that SII and LMR alone did not indicate disease prognosis in sarcoidosis due to the small number of patients and the lack of homogeneity between the groups in our study. The usefulness of these markers for clinical use should be investigated by studies that include those with extrapulmonary sarcoidosis, and that calculate these markers at the time of disease diagnosis and during the post-treatment period.

18F-Fluoroestradiol: Current Applications and Future Directions

In the United States, breast cancer is the second leading cause of cancer death in all women and the leading cause of cancer death in Black women. The breast cancer receptor profile, assessed with immunohistochemical staining of tissue samples, allows prediction of outcomes and direction of patient treatment. Approximately 80% of newly diagnosed breast cancers are hormone receptor (HR) positive, which is defined as estrogen receptor (ER) and/or progesterone receptor (PR) positive. Patients with ER-positive disease can be treated with therapies targeting the ER; however, the assessment of ER expression with immunohistochemical staining of biopsy specimens has several limitations including sampling error, false-negative results, challenging or inaccessible biopsy sites, and the inability to synchronously and serially assess all metastatic sites to identify spatial and/or temporal ER heterogeneity. In May 2020, after decades of research, the U.S. Food and Drug Administration approved the PET radiotracer fluorine 18 (¹⁸F) fluoroestradiol (FES) for clinical use in patients with ER-positive recurrent or metastatic breast cancer as an adjunct to biopsy. FES binds to the ER in the nucleus of ER-expressing cells, enabling whole-body in vivo assessment of ER expression. This article is focused on the approved uses of FES in the United States, including identification of a target lesion for confirmatory biopsy, in vivo assessment of biopsy-proven ER-positive disease, and evaluation of spatial and temporal ER heterogeneity. FES is an example of precision medicine that has been leveraged to optimize the care of patients with breast cancer. ^© RSNA, 2023 See the invited commentary by Fowler in this issue. Quiz questions for this article are available through the Online Learning Center.

Added Value of Abnormal Lymph Nodes Detected with FDG-PET/CT in Suspected Vascular Graft Infection

Vascular graft and endograft infections (VGEI) cause a serious morbidity and mortality burden. ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) imaging is frequently used in the diagnostic workup, but the additional value of abnormal (¹⁸F-FDG active and/or enlarged) locoregional lymph nodes is unknown. In this retrospective study, the additional diagnostic value of abnormal locoregional lymph nodes on ¹⁸F-FDG PET/CT imaging for VGEI was evaluated, including 54 patients with a culture-proven VGEI (defined according to the Management of Aortic Graft Infection [MAGIC] group classification) and 25 patients without VGEI. ¹⁸F-FDG PET/CT was qualitatively and quantitatively assessed for tracer uptake and pattern at the location of the vascular graft, and locoregional lymph node uptake and enlargement (>10 mm). ¹⁸F-FDG uptake intensity and pattern independently predicted the presence of VGEI by logistic regression (Χ²: 46.19, p < 0.001), with an OR of 7.38 (95% CI [1.65, 32.92], p = 0.009) and 18.32 (95% CI [3.95, 84.88], p < 0.001), respectively. Single visual assessment of abnormal locoregional lymph nodes predicted the presence of VGEI with a sensitivity of 35%, specificity of 96%, PPV of 95%, and NPV of 41%. The visual assessment of abnormal lymph nodes after qualitative assessment of ¹⁸F-FDG uptake intensity and pattern at the vascular graft location did not independently predict the presence of VGEI by logistic regression (Χ²: 3.60, p = 0.058; OR: 8.25, 95% CI [0.74, 63.37], p = 0.096). In conclusion, detection of abnormal locoregional lymph nodes on ¹⁸F-FDG PET/CT has a high specificity (96%) and PPV (95%) for VGEI. However, it did not add to currently used ¹⁸F-FDG PET/CT interpretation criteria.

Positron Emission Tomography Imaging in Vasculitis

Systemic vasculitides comprise a group of autoimmune diseases affecting blood vessels. [18F]-fluoro-2-deoxy-d-glucose positron emission tomography/computed tomography (FDG-PET/CT) plays an important role in the diagnosis and therapeutic monitoring of vasculitides affecting large-sized and medium-sized vessels. FDG-PET/CT also provides complementary information to other vascular imaging tools. The resolution and sensitivity of newer generation scanners continues to increase, hereby improving the ability of FDG-PET/CT to accurately assess the full disease extent in patients with vasculitis. Novel tracers targeting specific immune cells will allow for more detailed detection of vascular infiltrates.

[18F]FDG Uptake in Non-Infected Endovascular Grafts: A Retrospective Study

Purpose: After endovascular aneurysm repair (EVAR), an increased [¹⁸F]FDG uptake may be observed at PET/CT, being common to both vascular graft/endograft infection (VGEI) and sterile post-surgical inflammation. Increased non-specific metabolic activity, due to foreign body reaction, can persist for several years after surgery, thus complicating the interpretation of PET/CT studies. In this paper, we aimed to assess [¹⁸F]FDG distribution at different time-points after the implant of abdominal Endurant^® endografts in patients without suspicion of infection. Methods: We retrospectively evaluated [¹⁸F]FDG/CT in 16 oncological patients who underwent abdominal aortic aneurysm exclusion with Endurant^® grafts. Patients had no clinical suspicion of infection and were followed up for at least 24 months after scan. [¹⁸F]FDG PET/CT scans were interpreted using both visual and semi-quantitative analyses. Results: The time between the EVAR procedure and [¹⁸F]FDG PET/CT ranged between 1 and 36 months. All grafts showed mild and diffuse [¹⁸F]FDG uptake without a focal pattern. Mean values of SUVmax were 2.63 ± 0.48 (95% CI 2.38-2.88); for SUVmean 1.90 ± 0.33 (95% CI 1.72-2.08); for T/B ratios 1.43 ± 0.41 (95% CI 1.21-1.65). SUVmax and SUVmean were not correlated to the time elapsed from the procedure, but we observed a declining trend in T/B ratio over time. Conclusions: Endovascular implant of Endurant^® grafts does not cause a significant inflammatory reaction. The evidence of faint and diffuse [¹⁸F]FDG uptake along the graft can reliably exclude an infection, even in early post-procedural phases. Therefore, in patients with a low probability of VGEI, [¹⁸F]FDG PET/CT can also be performed immediately after EVAR.

Imaging evaluation of lymphoma in pregnancy with review of clinical assessment and treatment options

Lymphoma-related malignancies can be categorized as Hodgkin's lymphoma (HL) or non-Hodgkin's lymphoma (NHL) based on histologic characteristics. Although quite rare during pregnancy, HL and NHL are the fourth and fifth most common malignancies during the pregnancy period, respectively. Given the rarity of lymphoma among pregnant patients, radiologists are usually unfamiliar with the modifications required for staging and treatment of this population, even those who work at centers with busy obstetrical services. Therefore, this manuscript serves to not only review the abdominopelvic imaging features of lymphoma in pregnancy, but it also discusses topics including birthing parent and fetal lymphoma-related prognosis, both antenatal and postpartum, current concepts in the management of pregnancy-related lymphoma, as well as the current considerations regarding birthing parent onco-fertility.

Vascular Graft Infection Imaging

Vascular graft infection is a rare, life threatening complication of vascular repair with synthetic or native material. The pathogenesis, causative microorganisms and clinical manifestations vary according to graft's location and time duration since surgery. The diagnosis of graft infection is challenging since there is no single "gold standard" test and diagnosis is based on clinical and radiological criteria. Early and accurate diagnosis are essential for patient management and prevention of further complications. The first-choice imaging modality is computed tomography angiography (CTA) that can demonstrate typical signs of graft infection but has limited sensitivity and specificity, especially in early and low-grade infections. Nuclear medicine imaging methods, including labeled white blood cell scintigraphy and FDG PET/CT demonstrate improved diagnostic accuracy and play a pivotal role in the diagnosis of vascular graft infection. The different radiologic and the nuclear medicine imaging techniques, their advantages and limitations, and the recent guidelines detailing their use are reviewed.