Ultrashort Oncologic Whole-Body [18F]FDG Patlak Imaging Using LAFOV PET.

Methods to shorten [18F]FDG Patlak PET imaging procedures ranging from 65-90 to 20-30 min after injection, using a population-averaged input function (PIF) scaled to patient-specific image-derived input function (IDIF) values, were recently evaluated. The aim of the present study was to explore the feasibility of ultrashort 10-min [18F]FDG Patlak imaging at 55-65 min after injection using a PIF combined with direct Patlak reconstructions to provide reliable quantitative accuracy of lung tumor uptake, compared with a full-duration 65-min acquisition using an IDIF. Methods: Patients underwent a 65-min dynamic PET acquisition on a long-axial-field-of-view (LAFOV) Biograph Vision Quadra PET/CT scanner. Subsequently, direct Patlak reconstructions and image-based (with reconstructed dynamic images) Patlak analyses were performed using both the IDIF (time to relative kinetic equilibrium between blood and tissue concentration (t*) = 30 min) and a scaled PIF at 30-60 min after injection. Next, direct Patlak reconstructions were performed on the system console using only the last 10 min of the acquisition, that is, from 55 to 65 min after injection, and a scaled PIF using maximum crystal ring difference settings of both 85 and 322. Tumor lesion and healthy-tissue uptake was quantified and compared between the differently obtained parametric images to assess quantitative accuracy. Results: Good agreement was obtained between direct- and image-based Patlak analyses using the IDIF (t* = 30 min) and scaled PIF at 30-60 min after injection, performed using the different approaches, with no more than 8.8% deviation in tumor influx rate value (Ki ) (mean difference ranging from -0.0022 to 0.0018 mL/[min × g]). When direct Patlak reconstruction was performed on the system console, excellent agreement was found between the use of a scaled PIF at 30-60 min after injection versus 55-65 min after injection, with 2.4% deviation in tumor Ki (median difference, -0.0018 mL/[min × g]; range, -0.0047 to 0.0036 mL/[min × g]). For different maximum crystal ring difference settings using the scan time interval of 55-65 min after injection, only a 0.5% difference (median difference, 0.0000 mL/[min × g]; range, -0.0004 to 0.0013 mL/[min × g]) in tumor Ki was found. Conclusion: Ultrashort whole-body [18F]FDG Patlak imaging is feasible on an LAFOV Biograph Vision Quadra PET/CT system without loss of quantitative accuracy to assess lung tumor uptake compared with a full-duration 65-min acquisition. The ultrashort 10-min direct Patlak reconstruction with PIF allows for its implementation in clinical practice.

Current and Emerging Radiotracers in Molecular Cardiovascular Imaging.

Cardiovascular imaging has rapidly advanced over the past decades. Traditional imaging techniques such as echocardiography, computed tomography, and cardiovascular magnetic resonance are essential for assessing the structural and functional aspects of the cardiovascular system but often fall short in providing direct insights into disease activity. This gap is increasingly being bridged by molecular nuclear imaging techniques, including positron emission tomography and single-photon emission computed tomography, which enable the visualization of disease processes at the molecular and cellular levels. This review highlights the role of cardiovascular molecular imaging, emphasizing its current and potential applications in diagnosing and managing cardiovascular disease. With advancements in positron emission tomography scanners, novel radiotracers, and sophisticated imaging software, molecular imaging is set to play an essential role in precision medicine by enhancing our understanding of disease mechanisms, accelerating the development of targeted therapies, and facilitating personalized patient care.

Updated practice guideline for dual-energy X-ray absorptiometry (DXA).

The introduction of dual-energy X-ray absorptiometry (DXA) technology in the 1980s revolutionized the diagnosis, management and monitoring of osteoporosis, providing a clinical tool which is now available worldwide. However, DXA measurements are influenced by many technical factors, including the quality control procedures for the instrument, positioning of the patient, and approach to analysis. Reporting of DXA results may be confounded by factors such as selection of reference ranges for T-scores and Z-scores, as well as inadequate knowledge of current standards for interpretation. These points are addressed at length in many international guidelines but are not always easily assimilated by practising clinicians and technicians. Our aim in this report is to identify key elements pertaining to the use of DXA in clinical practice, considering both technical and clinical aspects. Here, we discuss technical aspects of DXA procedures, approaches to interpretation and integration into clinical practice, and the use of non-bone mineral density measurements, such as a vertebral fracture assessment, in clinical risk assessment.

Circulating ECM proteins decorin and alpha-L-iduronidase differentiate ATTRwt-CM from ATTRwt-negative HFpEF/HFmrEF.

AIMS: Wild-type transthyretin cardiac amyloidosis (ATTRwt-CM) is an under-recognized aetiology of heart failure (HF), necessitating early detection for timely treatment. Our study aimed to differentiate patients with ATTRwt-CM from ATTRwt-negative HFpEF/HFmrEF patients by identifying and validating circulating protein biomarkers. In addition, we measured the same biomarkers in patients with cardiomyopathy due to light chain amyloidosis (AL)-CM to gain disease-specific insights. METHODS AND RESULTS: In this observational study, serum concentrations of 363 protein biomarkers were measured in a discovery cohort consisting of 73 ATTRwt-CM, 55 AL-CM, and 59 ATTRwt-negative HFpEF/HFmrEF patients, using multiplex proximity extension assays. Sparse partial least squares analyses showed overlapping ATTRwt-CM and AL-CM biomarker profiles with clear visual differentiation from ATTRwt-negative patients. Pathway analyses with g:Profiler revealed significantly up-regulated proteoglycans (PG) and cell adhesion pathways in both ATTRwt-CM and AL-CM. Penalized regression analysis revealed that the proteoglycan decorin (DCN), lysosomal hydrolase alpha-L-iduronidase (IDUA) and glycosyl hydrolase galactosidase ß-1 (GLB-1) most effectively distinguished ATTRwt-CM from ATTRwt-negative patients (R2 = 0.71). In a prospective validation cohort of 35 ATTRwt-CM patients and 25 ATTRwt-negative patients, DCN and IDUA significantly predicted ATTRwt-CM in the initial analysis (DCN: OR 3.3, IDUA: OR 0.4). While DCN remained significant after correcting for echocardiographic parameters, IDUA did not. DCN showed moderate discriminative ability (AUC, 0.74; 95% CI, 0.61-0.87; sensitivity, 0.91; specificity, 0.52) as did IDUA (AUC, 0.78; 95% CI, 0.65-0.91; sensitivity, 0.91; specificity, 0.61). A model combining clinical factors (AUC 0.92) outperformed DCN but not IDUA, a combination of the biomarkers was not significantly better. Neither DCN nor IDUA correlated with established disease markers. CONCLUSION: ATTRwt-CM has a distinctly different biomarker profile compared with HFpEF/HFmrEF, while ATTRwt-CM patients share a similar biomarker profile with AL-CM patients characterized by up-regulation of proteoglycans and cell-adhesion pathways. The biomarkers DCN and IDUA show the potential to serve as an initial screening tool for ATTTRwt-CM. Further research is needed to determine the clinical usefulness of these and other extracellular matrix components in identifying ATTRwt-CM.

Prognostic value of single photon emission computed tomography myocardial perfusion imaging for the prediction of MACE in pre- kidney transplant recipients: A systematic review and meta-analysis.

BACKGROUND: Kidney transplantation provides substantial benefits in extending survival and improving quality of life for patients with end-stage renal disease. The incidence of major adverse cardiac events (MACE) increases with a decline of kidney function in patients with chronic kidney disease. After kidney transplantation, the incidence of MACE remains high. The objective of this study was to assess the prognostic significance of pre-transplant single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) in kidney transplant recipients. METHODS: A systematic literature search was performed between January 1st 2015 and March 26th 2024 in PubMed, EMBASE, Web of Science and The Cochrane Library to identify the prognostic value of SPECT MPI for developing MACE (primary outcome) and mortality (secondary outcome) in kidney transplant recipients (PROSPERO CRD42020188610). Risk of bias was assessed. Meta-analyses and subgroup analyses were performed using random-effects models. RESULTS: Six studies comprising 2090 SPECT MPI scans were included. Abnormal SPECT MPI scans were associated with an increased risk of MACE post-transplantation (HR 1.62, 95% CI 1.27-2.06, p < 0.001). Subgroup analyses showed consistent findings across various patient populations and methodological differences. Sensitivity analyses supported the robustness of our findings. CONCLUSIONS: Current evidence showed that pre-transplant SPECT MPI has significant prognostic value in identifying kidney transplant candidates at risk for MACE post-transplantation. Integrating SPECT MPI into preoperative assessments might enhance risk stratification and guide clinical decision-making. Prospective studies are needed to refine risk prediction models.

Clinical Performance Comparison of a Long Versus a Short Axial Field-of-View PET/CT Using EARL-Compliant Reconstructions.

PURPOSE: To ensure comparable PET/CT image quality between or within centres, clinical inter-system performance comparisons following European Association of Nuclear Medicine Research Ltd. (EARL) guidelines is required. In this work the performance of the long axial field-of-view Biograph Vision Quadra is compared to its predecessor, the short axial field-of-view Biograph Vision. PROCEDURES: To this aim, patients with suspected tumour lesions received a single weight-based (3 MBq/kg) 2-deoxy-2-[18F]fluoro-D-glucose injection and underwent routine clinical ( ∼ 15 min) scans on the Vision and 3-min scans on the Quadra in listmode in balanced order. Image quality (IQ), image noise (IN), and tumour demarcation (TD) were assessed visually by four nuclear medicine physicians using a 5-point Likert scale and semiquantitative analysis was performed using standardised uptake values (SUVs). Inter-reader agreement was tested using Wilcoxon's signed rank test and the SUVs were statistically compared using a paired t-test. RESULTS: Twenty patients (mean age, 60 years ± 8.8 [standard deviation], 16 male) were enrolled. Inter-reader agreement ranged from good to very good for IQ and IN (0.62 ≤ W ≤ 0.81), and fair for TD (0.29 ≤ W ≤ 0.39). Furthermore, a significant difference was found for TD (p = 0.015) between the systems, showing improved TD for the Quadra. CONCLUSION: This study demonstrates that the Quadra can be used in routine clinical practice with multiple PET/CT systems or in multicentre studies. This system provides comparable diagnostic image quality and semiquantitative accuracy, improved TD, and has the advantage of shorter scan durations.

Diagnostic performance of liver stiffness as marker of liver involvement in systemic immunoglobulin light chain (AL) amyloidosis.

OBJECTIVE: To investigate the diagnostic performance of liver stiffness for detecting liver involvement in immunoglobulin light chain (AL) amyloidosis. METHODS: Liver stiffness was measured using transient elastography in 71 patients with systemic AL amyloidosis and 18 patients with wild type transthyretin (ATTRwt) amyloidosis with cardiomyopathy. Both non-invasive consensus criteria and serum amyloid P component (SAP) scintigraphy were used as substitute standards instead of liver biopsy for establishing liver involvement. RESULTS: Liver stiffness was higher in AL amyloidosis patients with liver involvement than in those without: this was observed using both consensus criteria (median 14.4 kPa vs. 8.1 kPa; p = 0.001) and SAP scintigraphy (median 20.9 kPa vs. 6.2 kPa; p < 0.001). Liver stiffness was also higher in AL amyloidosis patients with liver involvement compared to AL and ATTRwt amyloidosis patients with cardiac involvement. Based on receiver operating characteristic (ROC) curves a cut-off value of 14.4 kPa for stiffness was optimal to indicate liver involvement, providing sensitivity and specificity of 50% and 74%, respectively, using the consensus criteria and 63% and 90%, respectively, using SAP scintigraphy as standard. CONCLUSION: Liver stiffness is a promising tool to establish liver involvement in AL amyloidosis having potential to become part of updated criteria for liver involvement.

[99mTc]Tc-hydroxydiphosphonate uptake in soft tissue is associated with amyloid load in subcutaneous abdominal fat tissue and mortality in wild-type transthyretin amyloidosis patients.

PURPOSE: Bone scintigraphy is key to non-invasively diagnosing wild-type transthyretin (ATTRwt) amyloidosis, and is mainly used to assess cardiac radiotracer uptake. However, extracardiac radiotracer uptake is also observed. We investigated whether intensity of soft tissue radiotracer uptake is associated with amyloid load in subcutaneous abdominal fat tissue and with mortality. METHODS: This prospective cohort study included 94 ATTRwt amyloidosis patients and 26 amyloid-negative heart failure controls who underwent whole-body [99mTc]Tc-hydroxydiphosphonate scintigraphy. Site-to-background ratios were calculated for heart, elbows, subcutaneous tissue, shoulders and wrists on anterior planar bone scintigraphy images using rib and whole-body radiotracer uptake as background. Fat tissue aspirates were stained with Congo red to grade amyloid load. Site-to-rib ratios were compared between ATTRwt amyloidosis patients and controls, and associations of site-to-background ratio with Congo red score and all-cause mortality were studied. RESULTS: ATTRwt amyloidosis patients had higher soft tissue-to-rib, heart-to-rib and heart-to-whole body ratios compared with controls. The intensity of soft tissue uptake was positively associated with amyloid load in fat tissue in ATTRwt amyloidosis patients. Estimated glomerular filtration rate, N-terminal brain natriuretic propeptide, high-sensitivity cardiac troponin T (hs-cTnT), and the prognostic Mayo and NAC staging system were associated with all-cause mortality in univariable models. Soft tissue/rib ratio, hs-cTnT and the prognostic staging systems were the only two variables that were independently associated withall-cause mortality. CONCLUSION: Soft tissue radiotracer uptake on bone scintigraphy in ATTRwt amyloidosis patients is positively associated with amyloid load in abdominal fat tissue and is independently associated with mortality.

Calciprotein particle counts associate with vascular remodelling in chronic kidney disease.

AIMS: Calciprotein particles (CPPs) are circulating calcium and phosphate nanoparticles associated with development of vascular calcification (VC) in chronic kidney disease (CKD). Although recent studies have been focusing on associations of CPPs with presence of VC in CKD, insights in the underlying processes and mechanisms by which CPPs might aggravate VC and vascular dysfunction in vivo are currently lacking. Here, we assessed overall burden of abdominal VC in healthy kidney donors and CKD patients, and subsequently performed transcriptome profiling in vascular tissue obtained from these subjects, linking outcome to CPP counts and calcification propensity. METHODS AND RESULTS: Calcification scores were quantified in renal arteries, iliac arteries and abdominal aorta, using computed tomography (CT) scans of kidney donors and CKD patients. Vascular tissue was collected from kidney donors (renal artery) and CKD patients (iliac artery), after which bulk RNA sequencing and gene set enrichment analysis (GSEA) was performed on a subset of patients. Calcification propensity (crystallization time, T50) was measured using nephelometry, and CPP counts with microparticle flow cytometric analysis. Increased calcification scores (based on CT) were found in CKD patients compared to kidney donors. Transcriptome profiling revealed enrichment for processes related to endothelial activation, inflammation, extracellular matrix (ECM) remodelling and ossification in CKD vascular biopsies compared to kidney donors. Calcification propensity was increased in CKD, as well as CPP counts, of which the latter significantly associated with markers of vascular remodelling. CONCLUSIONS: Our findings reveal that CKD is characterized by systemic VC with increased calcification propensity and CPP counts. Transcriptome profiling showed altered vascular gene expression with enrichment for endothelial activation, inflammation, ECM remodelling and ossification. Moreover, we demonstrate for the first time that vascular remodelling processes are associated with increased circulating CPP counts. Interventions targeting CPPs are promising avenues for alleviating vascular remodelling and VC in CKD.

Osteoporotic Fractures: Diagnosis, Evaluation, and Significance From the International Working Group on DXA Best Practices.

Osteoporotic fractures, also known as fragility fractures, are reflective of compromised bone strength and are associated with significant morbidity and mortality. Such fractures may be clinically silent, and others may present clinically with pain and deformity at the time of the injury. Unfortunately, and even at the time of detection, most individuals sustaining fragility fractures are not identified as having underlying metabolic bone disease and are not evaluated or treated to reduce the incidence of future fractures. A multidisciplinary international working group with representation from international societies dedicated to advancing the care of patients with metabolic bone disease has developed best practice recommendations for the diagnosis and evaluation of individuals with fragility fractures. A comprehensive narrative review was conducted to identify key articles on fragility fractures and their impact on the incidence of further fractures, morbidity, and mortality. This document represents consensus among the supporting societies and harmonizes best practice recommendations consistent with advances in research. A fragility fracture in an adult is an important predictor of future fractures and requires further evaluation and treatment of the underlying osteoporosis. It is important to recognize that most fragility fractures occur in patients with bone mineral density T scores higher than -2.5, and these fractures confirm the presence of skeletal fragility even in the presence of a well-maintained bone mineral density. Fragility fractures require further evaluation with exclusion of contributing factors for osteoporosis and assessment of clinical risk factors for fracture followed by appropriate pharmacological intervention designed to reduce the risk of future fracture. Because most low-trauma vertebral fractures do not present with pain, dedicated vertebral imaging and review of past imaging is useful in identifying fractures in patients at high risk for vertebral fractures. Given the importance of fractures in confirming skeletal fragility and predicting future events, it is recommended that an established classification system be used for fracture identification and reporting.

Improved Diagnostic Accuracy for Polymyalgia Rheumatica using FDG-PET/CT with Clinical Diagnosis or 2012 ACR/EULAR Classification Criteria.

PURPOSE: In routine care, clinicians may employ 2-[18F]fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET) computed tomography (CT) to validate their initial clinical diagnosis of polymyalgia rheumatica (PMR). Nevertheless, the diagnostic utility of combining FDG-PET/CT findings with clinical presentation has not been explored. Therefore, this study aimed to investigate whether the diagnostic accuracy for PMR could be enhanced by combining FDG-PET/CT findings with the clinical baseline diagnosis or the 2012 ACR/EULAR clinical classification criteria for PMR. METHODS: An investigation and a validation cohort were included from two countries, encompassing 66/27 and 36/21 PMR/non-PMR patients, respectively. The cohorts comprised treatment-naïve patients suspected of PMR, who initially received a clinical baseline diagnosis and underwent FDG-PET/CT scans. The FDG-PET/CT Leuven-score was applied to classify patients as either PMR or non-PMR and combined with the clinical baseline diagnosis. Final diagnoses were established through clinical follow-up after twelve or six months in the investigation and validation cohorts, respectively. RESULTS: In the investigation cohort, a clinical baseline diagnosis yielded a sensitivity/specificity of 94%/82%, compared with 78%/70% using the ACR/EULAR criteria. Combining the clinical baseline diagnosis with a positive Leuven-score showed a sensitivity/specificity of 80%/93%, compared with 80%/82% for an ACR/EULAR-Leuven-score. In the validation cohort, the baseline diagnosis revealed a sensitivity/specificity of 100%/91%, compared with 92%/76% using the ACR/EULAR criteria. Combining FDG-PET/CT with the baseline diagnosis demonstrated a sensitivity/specificity of 83%/95% compared with 89%/81% for the ACR/EULAR-Leuven-score. CONCLUSION: Combining FDG-PET/CT findings with the clinical baseline diagnosis or ACR/EULAR clinical classification criteria can improve the diagnostic specificity for PMR.

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

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

The Role of Fibroblast Activation Protein Inhibitor Positron Emission Tomography in Inflammatory and Infectious Diseases: An Updated Systematic Review.

The role of fibroblast activation protein inhibitor (FAPI) positron emission tomography/computed tomography (PET/CT) is emerging for the assessment of non-oncological diseases, such as inflammatory and infectious diseases, even if the evidence in the literature is still in its initial phases. We conducted a systematic search of Scopus, PubMed/MEDLINE, Embase, and Cochrane library databases for studies published before 31 December 2023 reporting infectious and inflammatory disease imaging with FAPI PET/CT. We included twenty-one studies for a total of 1046 patients. The most frequent disease studied was lung interstitial disease, investigated in six studies for a total of 200 patients, followed by bone and joint diseases in two studies and 185 patients, IgG4-related disease in 53 patients, and Crohn's disease in 30 patients. Despite the heterogeneity of studies in terms of study design and technical features, FAPI PET/CT showed a high detection rate and diagnostic role. Moreover, when compared with 2-[18F]FDG PET/CT (n = 7 studies), FAPI PET/CT seems to have better diagnostic performances. The presence of chronic inflammation and tissue remodeling, typical of immune-mediated inflammatory conditions, may be the underlying mechanism of FAPI uptake.

Feasibility of virtual non-iodine coronary calcium scoring on dual source photon-counting coronary CT angiography: a dynamic phantom study.

BACKGROUND: The aim of our current systematic dynamic phantom study was first, to optimize reconstruction parameters of coronary CTA (CCTA) acquired on photon counting CT (PCCT) for coronary artery calcium (CAC) scoring, and second, to assess the feasibility of calculating CAC scores from CCTA, in comparison to reference calcium scoring CT (CSCT) scans. METHODS: In this phantom study, an artificial coronary artery was translated at velocities corresponding to 0, < 60, and 60-75 beats per minute (bpm) within an anthropomorphic phantom. The density of calcifications was 100 (very low), 200 (low), 400 (medium), and 800 (high) mgHA/cm3, respectively. CCTA was reconstructed with the following parameters: virtual non-iodine (VNI), with and without iterative reconstruction (QIR level 2, QIR off, respectively); kernels Qr36 and Qr44f; slice thickness/increment 3.0/1.5 mm and 0.4/0.2 mm. The agreement in risk group classification between CACCCTA and CACCSCT scoring was measured using Cohen weighted linear κ with 95% CI. RESULTS: For CCTA reconstructed with 0.4 mm slice thickness, calcium detectability was perfect (100%). At < 60 bpm, CACCCTA of low, and medium density calcification was underestimated by 53%, and 15%, respectively. However, CACCCTA was not significantly different from CACCSCT of very low, and high-density calcifications. The best risk agreement was achieved when CCTA was reconstructed with QIR off, Qr44f, and 0.4 mm slice thickness (κ = 0.762, 95% CI 0.671-0.853). CONCLUSION: In this dynamic phantom study, the detection of calcifications with different densities was excellent with CCTA on PCCT using thin-slice VNI reconstruction. Agatston scores were underestimated compared to CSCT but agreement in risk classification was substantial. CLINICAL RELEVANCE STATEMENT: Photon counting CT may enable the implementation of coronary artery calcium scoring from coronary CTA in daily clinical practice. KEY POINTS: Photon-counting CTA allows for excellent detectability of low-density calcifications at all heart rates. Coronary artery calcium scoring from coronary CTA acquired on photon counting CT is feasible, although improvement is needed. Adoption of the standard acquisition and reconstruction protocol for calcium scoring is needed for improved quantification of coronary artery calcium to fully employ the potential of photon counting CT.

Multimodality imaging to assess diagnosis and evaluate complications of large vesselarteritis.

Different types of vasculitis can be distinguished according to the blood vessel's size that is preferentially affected: large-vessel, medium-vessel, and small-vessel vasculitides. Giant cell arteritis (GCA) and Takayasu's arteritis (TAK) are the main forms of large-vessel vasculitis, and may lead to lumen narrowing. Clinical manifestations of arterial narrowing on the short- and long term include vision loss, stroke, limb ischemia, and heart failure. Imaging tools are well established diagnostic tests for large-vessel vasculitis and may aid therapy monitoring in selected cases while providing important information regarding the occurrence of vascular damage, tissue and organ complications. This review aims to provide the current status of multimodality imaging for the diagnosis and identification of vascular complications in the field of large vessel vasculitis.

Large vessel giant cell arteritis.

Giant cell arteritis is the principal form of systemic vasculitis affecting people over 50. Large-vessel involvement, termed large vessel giant cell arteritis, mainly affects the aorta and its branches, often occurring alongside cranial giant cell arteritis, but large vessel giant cell arteritis without cranial giant cell arteritis can also occur. Patients mostly present with constitutional symptoms, with localising large vessel giant cell arteritis symptoms present in a minority of patients only. Large vessel giant cell arteritis is usually overlooked until clinicians seek to exclude it with imaging by ultrasonography, magnetic resonance angiography (MRA), computed tomography angiography (CTA), or [18F]fluorodeoxyglucose-PET-CT. Although the role of imaging in treatment monitoring remains uncertain, imaging by MRA or CTA is crucial for identifying aortic aneurysm formation during patient follow up. In this Series paper, we define the large vessel subset of giant cell arteritis and summarise its clinical challenges. Furthermore, we identify areas for future research regarding the management of large vessel giant cell arteritis.

Reliability, costs, and radiation dose of dual-energy X-ray absorptiometry in diagnosis of radiologic sarcopenia in surgically menopausal women.

OBJECTIVE: The aim of this study was to evaluate and compare reliability, costs, and radiation dose of dual-energy X-ray absorptiometry (DXA) to MRI and CT in measuring muscle mass for the diagnosis of sarcopenia. METHODS: Thirty-four consecutive DXA scans performed in surgically menopausal women from November 2019 until March 2020 were analyzed by two observers. Observers analyzed muscle mass of the lower limbs in every scan twice. Reliability was assessed by calculating inter- and intra-observer variability. Reliability from CT and MRI as well as radiation dose from CT and DXA were collected from literature. Costs for each type of scan were calculated according to the guidelines for economic evaluation of the Dutch National Health Care Institute. RESULTS: The 34 participants had a median age of 58 years (IQR 53-65) and a median body mass index of 24.6 (IQR 21.7-29.7). Inter-observer variability had an intraclass correlation coefficient (ICC) of 0.997 (95% CI 0.994-0.998) with a relative variability of 0.037 ± 0.022%. Regarding intra-observer variability, observer 1 had an ICC of 0.998 (95% CI 0.996-0.999) with a relative variability of 0.019 ± 0.016% and observer 2 had an ICC of 0.997 (95% CI 0.993-0.998) with a relative variability of 0.016 ± 0.011%. DXA costs were €62, CT €77, and MRI €195. The estimated radiation dose of CT was 2.5-3.0 mSv, for DXA this was 2-4 µSv. CONCLUSIONS: DXA has lower costs and a lower radiation dose, with low inter- and intra-observer variability, compared to CT and MRI for assessing lower limb muscle mass. TRIAL REGISTRATION: Netherlands Trial Register; NL8068. CRITICAL RELEVANCE STATEMENT: DXA is a good alternative for CT and MRI in assessing lower limb muscle mass, with lower costs and lower radiation dose, while inter-observer and intra-observer variability are low. KEY POINTS: • Screening for sarcopenia should be optimized as the population ages. • DXA outperformed CT and MRI in the measured metrics. • DXA validity should be further evaluated as an alternative to CT and MRI for sarcopenia evaluation.

A direct comparison in diagnostic performance of CDUS, FDG-PET/CT and MRI in patients suspected of giant cell arteritis.

OBJECTIVES: This study directly compares diagnostic performance of Colour Duplex Ultrasound (CDUS), Fluor-18-deoxyglucose Positron Emission Tomography Computed Tomography (FDG-PET/CT) and Magnetic Resonance Imaging (MRI) in patients suspected of giant cell arteritis (GCA). METHODS: Patients with suspected GCA were included in a nested-case control pilot study. CDUS, whole body FDG-PET/CT and cranial MRI were performed within 5 working days after initial clinical evaluation. Clinical diagnosis after six months follow-up by experienced rheumatologists in the field of GCA, blinded for imaging, was used as reference standard. Diagnostic performance of the imaging modalities was determined. Stratification for GCA subtype was performed and imaging results were evaluated in different risk stratification groups. RESULTS: In total, 23 patients with GCA and 19 patients suspected of but not diagnosed with GCA were included. Sensitivity was 69.6% (95%CI 50.4%-88.8%) for CDUS, 52.2% (95%CI 31.4%-73.0%) for FDG-PET/CT and 56.5% (95%CI 35.8%-77.2%) for MRI. Specificity was 100% for CDUS, FDG-PET/CT and MRI. FDG-PET/CT was negative for GCA in all isolated cranial GCA patients (n = 8), while MRI was negative in all isolated extracranial GCA patients (n = 4). In 4 GCA patients with false-negative (n = 2; intermediate and high risk) or inconclusive (n = 2; low and intermediate risk) CDUS results, further imaging confirmed diagnosis. CONCLUSIONS: Sensitivity of CDUS was highest, while specificity was excellent in all imaging modalities. Nevertheless, confidence intervals of all imaging modalities were overlapping. Following EULAR recommendations, CDUS can be used as a first test to diagnose GCA. With insufficient evidence for GCA, further testing considering GCA subtype is warranted.