Complex Inferior Vena Cava Filter Retrievals: Success Rate and Predictors of Adverse Events at a Large Specialized Referral Center.

BACKGROUND. Specialized inferior vena cava (IVC) filter referral centers can achieve improved retrieval outcomes, potentially facilitating complex retrievals after long filter dwell times. OBJECTIVE. The purpose of this study was to determine the success rate of complex IVC filter retrievals at a large specialized IVC filter referral center and to identify predictors of adverse events during complex retrievals. METHODS. This retrospective study included patients who underwent complex IVC filter retrieval from March 2014 to June 2018 at a large regional health system with specialized complex retrieval referral centers and interventional radiologists with expertise in such procedures. Complex retrievals methods included a range of loop snare, coaxial sheath, forceps, and snare techniques. Data were collected from the electronic medical record. The success rate of complex retrieval was determined. Factors associated with adverse events during retrieval procedures were explored. RESULTS. The study included 125 patients (51 women, 74 men; mean age, 60 years). The mean filter dwell time at retrieval was 47.5 months (median, 21.8 months). The complex retrieval success rate was 99.2% on the first attempt and 100.0% overall. A total of 11.2% (14/125) of patients experienced an adverse event during retrieval, including 10.4% (13/125) with minor and 0.8% (1/125) with major events. Prolonged dwell time was the only indication for complex retrieval that was significantly associated with adverse events (adverse event rate, 16.7% for patients with this indication vs 5.1% for patients without this indication; p = .04). In multiple regression analysis, the only significant independent predictor of adverse events was a filter dwell time of 5 years or longer (odds ratio, 6.98 [95% CI, 1.64-29.81]; p = .009). CONCLUSION. In a specialized referral system with expertise in complex retrieval methods, high retrieval success rates can be achieved in patients who have filters with long dwell times. Nonetheless, longer dwell times are associated with adverse events during retrieval procedures. CLINICAL IMPACT. The observations support performing early filter retrieval and referring patients who have filters with prolonged dwell times to specialized centers.

A critical review of radiotracers in the positron emission tomography imaging of traumatic brain injury: FDG, tau, and amyloid imaging in mild traumatic brain injury and chronic traumatic encephalopathy.

PURPOSE: Positron emission tomography (PET) has been widely utilized in the study of traumatic brain injury (TBI) for decades. While most applications of PET have attempted to assess neuronal function after TBI, more recently, novel radiotracers have sought to image biomarkers in the context of TBI and chronic traumatic encephalopathy (CTE). METHODS: This review will begin with an overview of TBI and CTE along with the acute and chronic pathophysiological consequences of TBI. Next, glycolysis, beta-amyloid, and tau protein radiotracers will be critically assessed in light of the most recent imaging studies available. CONCLUSIONS: Based on the scientific relevance of such radiotracers to the molecular processes of TBI and CTE along with the broader evidence of radiotracer specificity and selectivity, this review will weigh the strengths and weaknesses of each radiotracer. Nonetheless, the evidence indicates that PET will continue to be a powerful modality in the diagnosis of TBI-related conditions.

Thrombotic Risk Associated with Inferior Vena Cava Filter Placement in Patients with Heparin-Induced Thrombocytopenia.

PURPOSE: This study sought to define thromboembolic risk and mortality in patients with heparin-induced thrombocytopenia (HIT) undergoing inferior vena cava filter (IVCF) placement, in light of the American Society of Hematology's 2018 guidelines against routine use of IVCFs in this population. METHODS: A total of 26 patients with HIT who received IVCFs were retrospectively reviewed, and the outcomes of this group were compared with those of 4,707 controls with either HIT or IVCFs alone and with reported outcomes in prior studies. RESULTS: The patient group demonstrated 6- and 12-month mortality rates of 26.9% and 30.8%, respectively, which did not differ significantly from those of the control groups and were in line with published mortality rates in the literature. The measured thromboembolic risk of 19.2% in the patient group was also within the range of published rates for patients with HIT or IVCF alone. CONCLUSIONS: IVCF placement did not significantly increase the risk of thromboembolism or death in patients with HIT and may be a viable option in the subset of these patients who are not candidates for anticoagulation.

18F-NaF and 18F-FDG as molecular probes in the evaluation of atherosclerosis.

The early detection of atherosclerotic disease is vital to the effective prevention and management of life-threatening cardiovascular events such as myocardial infarctions and cerebrovascular accidents. Given the potential for positron emission tomography (PET) to visualize atherosclerosis earlier in the disease process than anatomic imaging modalities such as computed tomography (CT), this application of PET imaging has been the focus of intense scientific inquiry. Although 18F-FDG has historically been the most widely studied PET radiotracer in this domain, there is a growing body of evidence that 18F-NaF holds significant diagnostic and prognostic value as well. In this article, we review the existing literature on the application of 18F-FDG and 18F-NaF as PET probes in atherosclerosis and present the findings of original animal and human studies that have examined how well 18F-NaF uptake correlates with vascular calcification and cardiovascular risk.

Effects of age and cardiovascular risk factors on (18)F-FDG PET/CT quantification of atherosclerosis in the aorta and peripheral arteries.

OBJECTIVE: To quantify fluorine-18 fluorodeoxyglucose ((18)F-FDG) uptake in the aorta and peripheral arteries and assess the variation of (18)F-FDG uptake with age and cardiovascular risk factors. METHODS: The subject population of this retrospective study comprises melanoma patients who underwent whole-body (18)F-FDG PET/CT scans. The patients' medical records were examined for cardiovascular risk factors and for a history of coronary artery disease or peripheral artery disease. Fluorine-18-FDG uptake in the peripheral arteries (iliac and femoral) and aorta was semi-quantified as a weighted-average mean standardized uptake value (wA-SUVmean), while background noise was accounted for by measuring mean venous blood pool SUV (V-SUVmean) in the superior vena cava. Atherosclerosis was semi-quantified by the tissue-to-background ratio (TBR) (wA-SUVmean divided by V-SUVmean). A regression model and t-test were used to evaluate the effect of age and location on the degree of atherosclerosis. To assess the effect of cardiovascular risk factors on atherosclerotic burden, the wA-SUVmean of patients with at least one of these risk factors was compared to that of patients without any risk factors. RESULTS: A total of 76 patients (46 men, 30 women; 22-91 years old) were included in this study. The average TBR of the aorta and peripheral arteries were 2.68 and 1.43, respectively, and increased with age in both locations. In regression analysis, the beta coefficients of age for TBR in the aorta and peripheral arteries were 0.55 (P<0.001) and 0.03 (P<0.001), respectively. In all age groups, the TBR of the aorta was significantly greater than that of the peripheral arteries. The Pearson correlation coefficients between the four age groups and the TBR of the aorta and peripheral arteries were 0.83 (P<0.001) and 0.75 (P<0.001), respectively. The wA-SUVmean of patients with cardiovascular risk factors was only significant (P<0.05) in the aorta. CONCLUSION: An increase in (18)F-FDG uptake was observed in the peripheral arteries and aorta with increasing age. Cardiovascular risk factors were significantly correlated with (18)F-FDG uptake in aorta. The early detection of atherosclerosis with (18)F-FDG PET may allow for the initiation of preventative interventions prior to the manifestation of significant structural abnormalities or symptoms of disease.

Abass Alavi. A distinguished physician scientist and a pioneer in molecular imaging.

Abass Alavi is a world renowned physician-scientist and has made substantial contributions to development and translation of modern imaging techniques to the day-to-day practice of medicine. Among his accomplishments, the introduction of fluorine-18-fluorodeoxyglucose ((18)F-FDG )-positron emission tomography (PET) has truly revolutionized the field of medicine worldwide. The impact of using (18)F-FDG -PET along with computed tomography (CT) (and soon magnetic resonance imaging-MRI) in managing so many serious diseases and disorders is unparalleled by any other technique in recent history. He has received many awards for his outstanding contributions to the field of molecular imaging. Currently, he is actively involved in conducting research on a full time basis.

Tau Imaging in Head Injury.

Tau proteins play a significant role in a variety of degenerative neurologic conditions. Postmortem neuropathology studies of victims of repeat and severe head trauma have defined a unique spatial expression of neurologic tauopathies in these individuals, known as chronic traumatic encephalopathy. Established and newly developed radiotracers are now being applied to head injury populations with the intent of diagnosis and disease monitoring. This review assesses the role of tau in head injury, the state of tau radiotracer development, and the potential clinical value of tau-PET as derived from head injury studies.

An Artificial Intelligence-Based Chest X-ray Model on Human Nodule Detection Accuracy From a Multicenter Study.

Importance: Most early lung cancers present as pulmonary nodules on imaging, but these can be easily missed on chest radiographs. Objective: To assess if a novel artificial intelligence (AI) algorithm can help detect pulmonary nodules on radiographs at different levels of detection difficulty. Design, Setting, and Participants: This diagnostic study included 100 posteroanterior chest radiograph images taken between 2000 and 2010 of adult patients from an ambulatory health care center in Germany and a lung image database in the US. Included images were selected to represent nodules with different levels of detection difficulties (from easy to difficult), and comprised both normal and nonnormal control. Exposures: All images were processed with a novel AI algorithm, the AI Rad Companion Chest X-ray. Two thoracic radiologists established the ground truth and 9 test radiologists from Germany and the US independently reviewed all images in 2 sessions (unaided and AI-aided mode) with at least a 1-month washout period. Main Outcomes and Measures: Each test radiologist recorded the presence of 5 findings (pulmonary nodules, atelectasis, consolidation, pneumothorax, and pleural effusion) and their level of confidence for detecting the individual finding on a scale of 1 to 10 (1 representing lowest confidence; 10, highest confidence). The analyzed metrics for nodules included sensitivity, specificity, accuracy, and receiver operating characteristics curve area under the curve (AUC). Results: Images from 100 patients were included, with a mean (SD) age of 55 (20) years and including 64 men and 36 women. Mean detection accuracy across the 9 radiologists improved by 6.4% (95% CI, 2.3% to 10.6%) with AI-aided interpretation compared with unaided interpretation. Partial AUCs within the effective interval range of 0 to 0.2 false positive rate improved by 5.6% (95% CI, -1.4% to 12.0%) with AI-aided interpretation. Junior radiologists saw greater improvement in sensitivity for nodule detection with AI-aided interpretation as compared with their senior counterparts (12%; 95% CI, 4% to 19% vs 9%; 95% CI, 1% to 17%) while senior radiologists experienced similar improvement in specificity (4%; 95% CI, -2% to 9%) as compared with junior radiologists (4%; 95% CI, -3% to 5%). Conclusions and Relevance: In this diagnostic study, an AI algorithm was associated with improved detection of pulmonary nodules on chest radiographs compared with unaided interpretation for different levels of detection difficulty and for readers with different experience.

Imaging Atherosclerosis by PET, With Emphasis on the Role of FDG and NaF as Potential Biomarkers for This Disorder.

Molecular imaging has emerged in the past few decades as a novel means to investigate atherosclerosis. From a pathophysiological perspective, atherosclerosis is characterized by microscopic inflammation and microcalcification that precede the characteristic plaque buildup in arterial walls detected by traditional assessment methods, including anatomic imaging modalities. These processes of inflammation and microcalcification are, therefore, prime targets for molecular detection of atherosclerotic disease burden. Imaging with positron emission tomography/computed tomography (PET/CT) using 18F-fluorodeoxyglucose (FDG) and 18F-sodium fluoride (NaF) can non-invasively assess arterial inflammation and microcalcification, respectively. FDG uptake reflects glucose metabolism, which is particularly increased in atherosclerotic plaques retaining macrophages and undergoing hypoxic stress. By contrast, NaF uptake reflects the exchange of hydroxyl groups of hydroxyapatite crystals for fluoride producing fluorapatite, a key biochemical step in calcification of atherosclerotic plaque. Here we review the existing literature on FDG and NaF imaging and their respective values in investigating the progression of atherosclerotic disease. Based on the large volume of data that have been introduced to the literature and discussed in this review, it is clear that PET imaging will have a major role to play in assessing atherosclerosis in the major and coronary arteries. However, it is difficult to draw definitive conclusions on the potential role of FDG in investigating atherosclerosis given the vast number of studies with different designs, image acquisition methods, analyses, and interpretations. Our experience in this domain of research has suggested that NaF may be the tool of choice over FDG in assessing atherosclerosis, especially in the setting of coronary artery disease (CAD). Specifically, global NaF assessment appears to be superior in detecting plaques in tissues with high background FDG activity, such as the coronary arteries.

Detection of pulmonary artery atherosclerosis by FDG-PET/CT: a new observation.

The aim of this study was to investigate the feasibility of FDG-PET/CT imaging to detect pulmonary artery atherosclerosis and to assess the correlation between pulmonary function testing (PFT) results and the overall pulmonary artery metabolic activity. Twenty-nine subjects between the ages of 57-75, with a history of clinical suspicion of lung cancer, underwent PET/CT imaging at 3 hours following the administration of FDG. Global FDG uptake in the central pulmonary artery branches was determined. Average SUVmax, SUVmean, and tissue-to-background (TBR) mean and maximum were calculated within each vessel. The degree of FDG uptake in non-COPD and COPD patients and its correlation with PFT were examined in this population. Furthermore, the results from patients were compared with those of 10 age-matched controls. Based on these data, the number of lesions with varying degrees of FDG uptake among patients was higher than that in the normal control group. However, there was no statistically significant difference in average SUVmax, average SUVmean, average TBRmax, or average TBRmean between non-COPD and COPD patients. This indicates that the atherosclerotic process is focal and is not diffuse in nature. Although the global quantitative data generated did not reveal evidence for diffuse artery inflammation in patients with COPD, qualitative examination showed clear-cut evidence for focally increased FDG uptake in the pulmonary arteries. This observation indicates the presence of atherosclerotic plaques which are prevalent in patients with COPD. Future prospective studies with larger numbers of subjects are needed to confirm this important observation.

Evolving Role of PET in Detecting and Characterizing Atherosclerosis.

Cardiovascular molecular imaging has focused on assessing myocardial perfusion and ventricular ejection fraction. These modalities target late downstream effects of the atherosclerotic disease process; this calls for a change of focus toward methods that can detect early arterial wall changes before macrocalcifications become visible on computed tomography angiography and provide a better understanding of the disease process. We summarize current knowledge on PET in atherosclerosis and highlight pertinent questions relating to the early detection of atherosclerosis. The future of PET in atherosclerosis may be early individualized quantification of the arteriosclerotic disease burden rather than exploration of features of individual arterial plaques.

Comparison Between Different PET and CT-Based Imaging Interpretation Criteria at Interim Imaging in Patients With Diffuse Large B-Cell Lymphoma.

OBJECTIVE: To evaluate the predictive value of interim PET (iPET) in diffuse large B-cell lymphoma (DLBCL) using 5 different imaging interpretation criteria: Deauville 5-point scale criteria, International Harmonization Project (IHP) criteria, Response Evaluation Criteria In Solid Tumors (RECIST) 1.1, European Organization for Research and Treatment of Cancer, and PET Response Criteria in Solid Tumors (PERCIST) 1.0. METHODS: We retrospectively reviewed records from 38 patients with DLBCL who underwent baseline and iPET at our institution. Imaging was interpreted according to the previously mentioned criteria. Results were correlated with end-of-treatment response, based on reports at the end of treatment radiological examinations, overall survival (OS), and progression-free survival (PFS) to assess and compare the predictive value of iPET according to each criterion. We also evaluated the concordance between different criteria. RESULTS: The Deauville and PERCIST criteria were the most reliable for predicting end-of-treatment response, reporting an accuracy of 81.6%. They also correlated with OS and PFS (P = 0.0004 and P = 0.0001, and P = 0.0007 and P = 0.0002, for Deauville and PERCIST, respectively). Interim PET according to European Organization for Research and Treatment of Cancer also predicted the end-of-treatment response with an accuracy of 73.7% and had a significant correlation with OS (P = 0.007) and PFS (P = 0.007). In contrast, the IHP criteria and RECIST did not predict outcomes: the accuracy for end-of-treatment response was 34.2% and 36.8%, respectively, with no significant correlation with OS or PFS (P = 0.182 and P = 0.357, and P = 0.341 and P = 0.215, for OS and PFS, respectively). CONCLUSIONS: The predictive value of iPET in DLBCL patients is most reliable using the Deauville and PERCIST criteria. Criteria that rely on anatomical characteristics, namely, RECIST and IHP criteria, are less accurate in predicting patient outcomes in DLBCL.

The Role of PET in Evaluating Atherosclerosis: A Critical Review.

Atherosclerosis is a common age-related disorder and is the major cause of morbidity and mortality in the developed countries. Structural imaging techniques, such as CT and MRI, have been of limited value in early detection of atherosclerotic plaques, and therefore, there is a dire need for techniques that are highly sensitive and specific for this purpose. Over the past decade, PET imaging with FDG and NaF has been tested for detection and characterization of atherosclerotic plaques in the major coronary arteries. While FDG uptake reflects inflammation in the plaques, NaF uptake is related to micro-calcification at the site. Recent data have revealed higher sensitivity for NaF compared to that of FDG-PET imaging for assessing this age-related disorder. Therefore, it is conceivable that detection of micro-calcification by NaF may become the study of choice in the future. Also, small volume of plaques even in the major arteries poses a significant challenge for optimal visualization and quantification of the disease process. Based on animal and human data, it has become apparent that global assessment of disease activity may overcome the physical limitations of PET imaging for optimal quantification of plaque burden in the arteries. The role of other tracers for detection of atherosclerosis is limited at this time and it is unlikely that other compounds will play a role in assessing plaques in the near future.

Pre-treatment partial-volume-corrected TLG is the best predictor of overall survival in patients with relapsing/refractory non-hodgkin lymphoma following radioimmunotherapy.

The role of fluorodeoxyglucose-positron emission tomography (FDG-PET) has been well established in assessment of lymphoma, including non-Hodgkin lymphoma (NHL). The aim of this study was to compare changes and survival predictive values of various quantification parameters of FDG-PET/CT in patients with relapsing/refractory lymphoma before and after radioimmunotherapy (RIT). Data from 17 patients with relapsing/refractory NHL, treated with targeted RIT after chemotherapy/radiotherapy, were retrospectively collected. FDG-PET/CT scans were performed approximately three months before and six months after RIT. An adaptive contrast-oriented thresholding algorithm was used to segment lesions on the FDG-PET images. Wilcoxon signed-rank tests were used to assess changes in SUVmax, SUVmean, partial volume-corrected SUVmean (pvcSUVmean), total lesion glycolysis (TLG), and pvcTLG before and after treatment. The patients were followed up after completing RIT for up to 10 years. Kaplan-Meier and Cox regression analyses evaluated the association between the quantification parameters and survival data. In the survived group, the decrease in mean percentage of change for TLG and pvcTLG was greater than SUVmax, SUVmean and pvcSUVmean [TLG: 253.9 to 106.9, -81.4%; P = 0.052 and pvcTLG: 368.9 to 153.3, -58.4%; P = 0.04]. In addition, overall survival (OS) was shorter in patients with pre-RIT pvcTLG more than 644 compared to those below this value (log-rank P < 0.01). In univariate Cox regression for OS, a higher baseline pvcTLG was a significant prognostic factor (HR: 6.8, P = 0.02). Our results showed that pre-treatment pvcTLG was the best predictor of OS in patients with relapsing/refractory NHL following RIT.

Response Assessment Criteria and Their Applications in Lymphoma: Part 2.

Interim and end-of-treatment PET/CT have become central to the evaluation of Hodgkin and non-Hodgkin lymphoma. This review article seeks to aid clinical decision making by providing an overview of available data on the diagnostic and prognostic value of PET/CT imaging for response assessment and pretransplant evaluation in lymphoma. The relative strengths and limitations of these techniques in various disease subtypes and clinical scenarios are explored, along with their current standards for reporting and latest developments. Particular attention is given to response-adapted therapy, which is emerging as a cornerstone of clinical management.

A Study of the Feasibility of FDG-PET/CT to Systematically Detect and Quantify Differential Metabolic Effects of Chronic Tobacco Use in Organs of the Whole Body-A Prospective Pilot Study.

RATIONALE AND OBJECTIVES: The aim of this study was to assess the feasibility of 18F-fluorodeoxyglucose (FDG)-positron emission tomography/computed tomography (PET/CT) to systematically detect and quantify differential effects of chronic tobacco use in organs of the whole body. MATERIALS AND METHODS: Twenty healthy male subjects (10 nonsmokers and 10 chronic heavy smokers) were enrolled. Subjects underwent whole-body FDG-PET/CT, diagnostic unenhanced chest CT, mini-mental state examination, urine testing for oxidative stress, and serum testing. The organs of interest (thyroid, skin, skeletal muscle, aorta, heart, lung, adipose tissue, liver, spleen, brain, lumbar spinal bone marrow, and testis) were analyzed on FDG-PET/CT images to determine their metabolic activities using standardized uptake value (SUV) or metabolic volumetric product (MVP). Measurements were compared between subject groups using two-sample t tests or Wilcoxon rank-sum tests as determined by tests for normality. Correlational analyses were also performed. RESULTS: FDG-PET/CT revealed significantly decreased metabolic activity of lumbar spinal bone marrow (MVPmean: 29.8 ± 9.7 cc vs 40.8 ± 11.6 cc, P = 0.03) and liver (SUVmean: 1.8 ± 0.2 vs 2.0 ± 0.2, P = 0.049) and increased metabolic activity of visceral adipose tissue (SUVmean: 0.35 ± 0.10 vs 0.26 ± 0.06, P = 0.02) in chronic smokers compared to nonsmokers. Normalized visceral adipose tissue volume was also significantly decreased (P = 0.04) in chronic smokers. There were no statistically significant differences in the metabolic activity of other assessed organs. CONCLUSIONS: Subclinical organ effects of chronic tobacco use are detectable and quantifiable on FDG-PET/CT. FDG-PET/CT may, therefore, play a major role in the study of systemic toxic effects of tobacco use in organs of the whole body for clinical or research purposes.

Positron emission tomography: ligand imaging.

Since it was first used to image the brain in 1976, positron emission tomography (PET) has been utilized in a wide range of neurologic and psychiatric applications. From cerebral metabolism to receptor concentration, various PET imaging techniques involving a host of radiopharmaceuticals have provided insight into countless facets of both the normal and diseased brain. Although the majority of these radiopharmaceuticals are still limited to the realm of research, one PET ligand in particular has gained widespread clinical use: (18)F-fluorodeoxyglucose, a radiolabeled analog of glucose, has become an exceedingly prevalent clinical tool for the measurement of metabolism in organs throughout the body, including the brain. In recent years, a number of novel PET ligands have also made it through the US Food and Drug Administration approval process and been used clinically. However, gaining approval is by no means the only challenge facing these radiopharmaceuticals. Traversing the blood-brain barrier is a formidable obstacle in drug delivery, and accurately modeling tracer kinetics and correcting for the partial-volume effect are among the difficult tasks that remain once the ligand reaches its intended target. Even so, the use of PET imaging in neurology and psychiatry can be expected to expand in the coming years as novel radiopharmaceuticals continue to be developed.

Response Assessment Criteria and Their Applications in Lymphoma: Part 1.

The effectiveness of cancer therapy, both in individual patients and across populations, requires a systematic and reproducible method for evaluating response to treatment. Early efforts to meet this need resulted in the creation of numerous guidelines for quantifying posttherapy changes in disease extent, both anatomically and metabolically. Over the past few years, criteria for disease response classification have been developed for specific cancer histologies. To date, the spectrum of disease broadly referred to as lymphoma is perhaps the most common for which disease response classification is used. This review article provides an overview of the existing response assessment criteria for lymphoma and highlights their respective methodologies and validities. Concerns over the technical complexity and arbitrary thresholds of many of these criteria, which have impeded the long-standing endeavor of standardizing response assessment, are also discussed.