Optimization of [18F]-FDOPA Brain PET Acquisition Times for Assessment of Parkinsonism in the Clinical Setting.

BACKGROUND AND PURPOSE: Fluorine 18-fluoro-L-dopa ([18F]-FDOPA) was approved by the FDA in 2019 and reimbursed by the Centers for Medicare & Medicaid Services in 2022 for use with PET to visualize dopaminergic nerve terminals in the striatum for evaluation of parkinsonism. We sought to determine the optimal image acquisition time for [18F]-FDOPA PET by evaluating rater-estimated FDOPA positivity and image quality across 4 time points. MATERIALS AND METHODS: Brain PET/CT was acquired 90 minutes following injection of 185 megabecquerel (5 mCi) of [18F]-FDOPA. PET was acquired in list mode for 20 minutes, and data were replayed to represent 15-, 10-, and 5-minute acquisitions. By means of MIMneuro, PET/MR imaging or PET/CT was independently graded for FDOPA positivity and image quality by 2 readers, blinded to the clinical report and diagnosis. Expert neuroradiologist clinical reads were used as the criterion standard. RESULTS: Twenty patients were included, average age 65.6 years, 55% women. Image-quality ratings decreased with shorter acquisition times for both readers (reader 1, ρ = 0.23, P = .044; reader 2, ρ = 0.24, P = .036), but there was no association between abnormality confidence scores and acquisition time (reader 1, ρ = -0.13, P = .250; reader 2, ρ = -0.19, P = .100). There was a high degree of consistency in intra- and interrater agreement and agreement with the expert reads when using acquisition times of ≥10 minutes (maximal confidence score consistency [ρ = 0.92] and interrater agreement [κ = 0.90] were observed at 15 minutes), while image quality was consistently rated as low and FDOPA positivity ratings were inconsistent when using a 5-minute acquisition time. CONCLUSIONS: Our study suggests that image-quality ratings were stable after 15 minutes and that between-subject abnormality detection rates were highly consistent between the 2 readers when acquired for at least 10 and up to 20 minutes but were inconsistent at 5 minutes. Shorter [18F]-FDOPA PET acquisition times may help maximize patient comfort while increasing throughput in the clinical setting.

PET/MRI Applications in Pediatric Epilepsy.

Epilepsy neuroimaging assessment requires exceptional anatomic detail, physiologic and metabolic information. Magnetic resonance (MR) protocols are often time-consuming necessitating sedation and positron emission tomography (PET)/computed tomography (CT) comes with a significant radiation dose. Hybrid PET/MRI protocols allow for exquisite assessment of brain anatomy and structural abnormalities, in addition to metabolic information in a single, convenient imaging session, which limits radiation dose, sedation time, and sedation events. Brain PET/MRI has proven especially useful for accurate localization of epileptogenic zones in pediatric seizure cases, providing critical additional information and guiding surgical decision making in medically refractory cases. Accurate localization of seizure focus is necessary to limit the extent of the surgical resection, preserve healthy brain tissue, and achieve seizure control. This review provides a systematic overview with illustrative examples demonstrating the applications and diagnostic utility of PET/MRI in pediatric epilepsy.

18 F-FDG Brain PET/MRI in Amyotrophic Lateral Sclerosis- Frontotemporal Spectrum Disorder (ALS-FTSD).

Amyotrophic lateral sclerosis (ALS) is a fatal and progressive neurodegenerative disorder involving both upper and lower motor neurons. Interestingly, 15 to 41% of patients with ALS have concomitant frontotemporal dementia (FTD). Approximately, 50% of patients with ALS can copresent with a broader set of neuropsychological pathologies that do not meet FTD diagnostic criteria. This association resulted in revised and expanded criteria establishing the ALS-frontotemporal spectrum disorder (FTSD). In this case report, we review background information, epidemiology, pathophysiology, and structural and molecular imaging features of ALS-FTSD.

Semiquantitative Approach to Amyloid Positron Emission Tomography Interpretation in Clinical Practice.

Objective Amyloid positron emission tomography (PET) plays a vital role in the in vivo detection of ß-amyloid accumulation in Alzheimer's disease. Increasingly, trainees and infrequent readers are relying on semiquantitative analyses to support clinical diagnostic efforts. Our objective was to determine if the visual assessment of amyloid PET may be facilitated by relying on semiquantitative analysis. Methods We conducted a retrospective review of [ 18 F]-florbetaben PET/computed tomographies (CTs) from 2016 to 2018. Visual interpretation to determine Aß+ status was conducted by two readers blinded to each other's interpretation. Scans were then post-processed utilizing the MIMneuro software, which generated regional-based semiquantitative Z-scores indicating cortical Aß-burden. Results Of 167 [ 18 F]-florbetaben PET/CTs, 92/167 (reader-1) and 101/167 (reader-2) were positive for amyloid deposition (agreement = 92.2%, κ = 0.84). Additional nine scans were identified as possible Aß-positive based solely on semiquantitative analyses. Largest semiquantitative differences were identified in the left frontal lobe (Z = 7.74 in Aß + ; 0.50 in Aß - ). All unilateral regions showed large statistically significant differences in Aß-burden ( P ≤ 2.08E-28). Semiquantitative scores were highly sensitive to Aß+ status and accurate in their ability to identify amyloid positivity, defined as a positive scan by both readers (AUC ≥ 0.90 [0.79-1.00]). Spread analyses suggested that amyloid deposition was most severe in the left posterior cingulate gyrus. The largest differences between Aß +/Aß- were in the left frontal lobe. Analyses using region-specific cutoffs indicated that the presence of amyloid in the temporal and anterior cingulate cortex, while exhibiting relatively low Z-scores, was most common. Conclusion Visual assessment and semiquantitative analysis provide highly congruent results, thereby enhancing reader confidence and improving scan interpretation. This is particularly relevant, given recent advances in amyloid-targeting disease-modifying therapeutics.

Amyloid-Related Imaging Abnormalities: An Update.

Amyloid-related imaging abnormalities (ARIA) is a term introduced in 2010 to encompass a spectrum of MRI findings observed in patients receiving investigational anti-amyloid beta (Aß) immunotherapies for Alzheimer disease (AD). The entity can be broadly categorized into ARIA characterized by edema and effusion (ARIA-E) and ARIA characterized by microhemorrhages and superficial siderosis (ARIA-H). ARIA typically occurs early in the treatment course and has a higher incidence in patients who are apolipoprotein E ε4 allele carriers. ARIA-E has an additional dose dependence, with higher incidence in patients receiving higher doses of anti-Aß immuno-therapies. ARIA is often asymptomatic and self-resolving. The recognition of ARIA has implications for patient selection and monitoring for Aß immunotherapies, and its development can potentially lead to a pause or discontinuation of therapy. The FDA's first approval of an Aß-targeting monoclonal antibody for AD treatment in 2021 will lead to such therapy's expanded use beyond the clinical trial setting and to radiologists more commonly encountering ARIA in clinical practice. This review explores the theorized pathophysiologic mechanisms for ARIA, describes the MRI findings and grading schemes for ARIA-E and AREA-H, and summarizes relevant Aß immunotherapies. Through such knowledge, radiologists can optimally impact the management of patients receiving targeted AD therapies.

Assessment of Alzheimer's Disease Imaging Biomarkers in World Trade Center Responders with Cognitive Impairment at Midlife.

Purpose Incidence of early onset neurocognitive dysfunction has been reported in World Trade Center (WTC) responders. Ongoing studies are investigating the underlying etiology, as we are concerned that an underlying risk of neurodegenerative dementia may be occurring because of their stressful and neurotoxic exposures to particulate matter when they responded to the search and rescue efforts on September 11, 2001. The purpose of this study is to report preliminary results from two ongoing positron emission tomography (PET)/magnetic resonance imaging (MRI) imaging studies investigating the presence of Alzheimer's disease (AD) biomarkers, such as ß-amyloid, tau, and neurodegeneration, and compare our findings to published norms. Methods We present findings on 12 WTC responders diagnosed with either cognitive impairment (CI) or mild cognitive impairment (MCI), now at midlife, who underwent PET/MRI brain imaging as part of ongoing studies. Six responders with CI received [ 18 F] florbetaben (FBB) to detect ß-amyloidosis and six separate responders with MCI received [ 18 F] flortaucipir (FTP) to detect tauopathy. All 12 responders underwent concomitant MRI scans for gray matter volume analysis of neurodegeneration. Results PET analysis revealed 50% FBB and 50% of FTP scans were clinically read as positive and that 50% of FTP scans identified as consistent with Braak's stage I or II. Furthermore, one responder identified as centiloid positive for AD. Gray matter volumes from MRI analyses were compared with age/sex-matched norms (Neuroquant), identifying abnormally low cortical volumes in the occipital and temporal lobes, as well as the inferior temporal gyri and the entorhinal cortex. Conclusion These preliminary results suggest that WTC responders with neurocognitive dysfunction may be at increased risk for a neurodegenerative dementia process as a result of their exposures at September 11, 2001.

Extensive Nonsegmental Pulmonary Perfusion Defects on SPECT/CT as an Early Sign of COVID-19 Infection.

We describe a hospitalized patient with confirmed coronavirus disease 2019 in whom the initial chest computed tomography (CT) was negative, while subsequent perfusion single-photon emission computed tomography/computed tomography imaging revealed extensive nonsegmental perfusion defects in addition to newly developing parenchymal densities. Possible reasons for these findings and their relationship to the multisystem severe acute respiratory syndrome coronavirus 2 infection are discussed in this article.

Retrospective review COVID-19 vaccine induced thrombotic thrombocytopenia and cerebral venous thrombosis-what can we learn from the immune response.

INTRODUCTION: Cerebral Venous Thrombosis (CVT), prior to the COVID pandemic, was rare representing 0.5 of all strokes, with the diagnosis made by MRI or CT venography.1-,3 COVID-19 patients compared to general populations have a 30-60 times greater risk of CVT compared to non-affected populations, and up to a third of severe COVID patients may have thrombotic complications.4-8 Currently, vaccines are the best way to prevent severe COVID-19. In February 2021, reports of CVT and Vaccine-induced immune thrombotic thrombocytopenia (VITT) related to adenovirus viral vector vaccines including the Oxford-AstraZeneca vaccine (AZD1222 (ChAdOx1)) and Johnson & Johnson COVID-19 vaccine (JNJ-78436735 (Ad26.COV2·S)), were noted, with a 1/583,000 incidence from Johnson and Johnson vaccine in the United States.11, 12 This study retrospectively analyzed CVT and cross-sectional venography at an Eastern Medical Center from 2018 to 2021, and presents radiographic examples of CVT and what is learned from the immune response. METHODS: After IRB approval, a retrospective review of cross-sectional CTV and MRVs from January 1st 2018 to April 30th 2021, at a single health system was performed. Indications, vaccine status, patient age, sex, and positive finding incidence were specifically assessed during March and April for each year. A multivariable-adjusted trends analysis using Poisson regression estimated venogram frequencies and multivariable logistic regression compared sex, age, indications and vaccination status. RESULTS AND DISCUSSION: From January 1, 2018 to April 30, 2021, (Fig. 1), a total of n = 2206 in patient and emergency room cross-sectional venograms were obtained, with 322 CTVs and 1884 MRVs. In 2018, 2019, 2020, respective totals of cross-sectional venograms were 568, 657, 660, compared to 321 cross-sectional venograms in the first four months of 2021. CTV in 2018, 2019, 2020, respective totals were 51, 86, 97, MRV totals were 517, 571, 563, compared to the 2021 first four month totals of 88 CTVs and 233 MRVs. March, April 2018, 2019, 2020, CTVs respectively were 6, 17, 11, compared to the 2021 first four months of 59 CTVs, comprising 63% of the total 93 CTVs, respective MRVs were 79, 97, 52, compared to 143 MRVs in the first four months of 2021 for 39% of the total 371 MRVs. In March, April 2020 during the pandemic onset, cross-sectional imaging at the East Coast Medical Center decreased, as priorities were on maintaining patient ventilation, high level of care and limiting spread of disease. In March/April 2021, reports of VITT and CVT likely contributed to increased CTVs and MRVs, of 39.65% [1.20-1.63] increase (P < 0.001) from prior. In March, April 2021 of 202 venograms obtained, 158 (78.2.%) were unvaccinated patients, 16 positive for CVT (10.1%), 44 were on vaccinated patients (21.7%), 8 specifically ordered with vaccination as a clinical indication, 2 positive for CVT (4.5%), (odds ratio = 0.52 [0.12-2.38], p = 0.200). CONCLUSION: CTV prior to the COVID pandemic, was rare, responsible for 0.5 of all strokes, at the onset of the pandemic in the East Coast, overall cross-sectional imaging volumes declined due to maintaining ventilation, high levels of care and limiting disease spread, although COVID-19 patients have a 30-60 times greater risk of CVT compared to the general population, and vaccination is currently the best option to mitigate severe disease. In early 2021, reports of adenoviral vector COVID vaccines causing CTV and VITT, led to at 39.65% increase in cross-sectional venography, however, in this study unvaccinated patients in 2021 had higher incidence of CVT (10.1%), compared to the vaccinated patients (4.5%). Clinicians should be aware that VITT CVT may present with a headache 5-30 days post-vaccination with thrombosis best diagnosed on CTV or MRV. If thrombosis is present with thrombocytopenia, platelets <150 × 109, elevated D-Dimer >4000 FEU, and positive anti-PF4 ELISA assay, the diagnosis is definitive.13 VITT CVT resembles spontaneous autoimmune heparin induced thrombocytopenia (HIT), and is postulated to occur from platelet factor 4 (PF4) binding to vaccine adenoviral vectors forming a novel antigen, anti-PF4 memory B-cells and anti-PF4 (VITT) antibodies.14-17.

Overview of tau PET molecular imaging.

PURPOSE OF REVIEW: This article reviews tau PET imaging with an emphasis on first-generation and second-generation tau radiotracers and their application in neurodegenerative disorders, including Alzheimer's disease and non-Alzheimer's disease tauopathies. RECENT FINDINGS: Tau is a critical protein, abundant in neurons within the central nervous system, which plays an important role in maintaining microtubules by binding to tubulin in axons. In its abnormal hyperphosphorylated form, accumulation of tau has been linked to a variety of neurodegenerative disorders, collectively referred to as tauopathies, which include Alzheimer's disease and non-Alzheimer's disease tauopathies [e.g., corticobasal degeneration (CBD), argyrophilic grain disease, progressive supranuclear palsy (PSP), and Pick's disease]. A number of first-generation and second-generation tau PET radiotracers have been developed, including the first FDA-approved agent [18F]-flortaucipir, which allow for in-vivo molecular imaging of underlying histopathology antemortem, ultimately guiding disease staging and development of disease-modifying therapeutics. SUMMARY: Tau PET is an emerging imaging modality in the diagnosis and staging of tauopathies.

Factors Driving Resistance to Clinical Decision Support: Finding Inspiration in Radiology 3.0.

PURPOSE: The effectiveness of evidence-based guidelines (EBGs) and clinical decision support (CDS) is significantly hampered by widespread clinician resistance to it. Our study was designed to better understand the reasons for this resistance to CDS and explore the factors that drive it. METHODS: We used a mixed-methods approach to explore and identify the drivers of resistance for CDS among clinicians, including a web-based multispecialty survey exploring clinicians' impressions of the strengths and weaknesses of CDS, two clinician focus groups, and several one-on-one focused clinician interviews in which individual participants were asked to comment on their rationale for choosing imaging utilization that might not be supported by EBGs. Additionally, a unique electronic learning and assessment module known as Amplifire was used to probe clinician knowledge gaps regarding EBGs and CDS. RESULTS: In both the quantitative and qualitative portions of the study, the primary factor driving resistance to CDS was a desire to order studies not supported by EBGs, primarily for the purpose of reducing the clinician's diagnostic uncertainty. CONCLUSIONS: Our results suggest that to enhance the effectiveness of CDS, we must first address the issue of clinician discomfort with diagnostic uncertainty and the role of imaging via educational outreach and ongoing radiologist consultation.

Metabolic positron-emission tomography/magnetic resonance imaging in primary progressive aphasia and frontotemporal lobar degeneration subtypes: Reassessment of expected [18F]-fluorodeoxyglucose uptake patterns.

Clinical assessment of frontotemporal lobar degeneration (FTLD)/primary progressive aphasia (PPA) patients is challenging, given that common cognitive assessments rely extensively on language. Since asymmetry in neuroimaging biomarkers is often described as a central finding in these patients, our study evaluated [18F]-fluorodeoxyglucose (FDG) uptake patterns in patients meeting clinical and imaging criteria for FTLD, with emphasis on PPA. Fifty-one subjects underwent brain [18F]-FDG positron-emission tomography/magnetic resonance imaging (PET/MRI) as part of their routine clinical workup for dementia and neurodegenerative disease. Images were obtained using a Siemens Biograph mMR integrated 3T PET/MRI scanner. PET surface maps and fusion fluid-attenuated inversion recovery-PET images were generated utilizing MIMneuro software. Two board-certified neuroradiologists and one nuclear medicine physician blinded to patient history classified each FTLD/PPA subtype and assessed for left- versus right-side dominant hypometabolism. Qualitative and semiquantitative assessment demonstrated 18 cases of PPA, 16 behavioral variant frontotemporal dementia (bvFTD), 12 corticobasal degeneration, and 5 progressive supranuclear palsy. Among the 18 PPA subjects (11 svPPA, 5 lvPPA, and 2 agPPA), 12 (67%) demonstrated left-dominant hypometabolism and 6 (33%) right-dominant hypometabolism. While existing literature stresses left-dominant hypometabolism as a key imaging feature in the PPA subtypes, a third of our cases demonstrated right-dominant hypometabolism, suggesting that emphasis should be placed on the functionality of specific brain regions affected, rather than left versus right sidedness of hypometabolism patterns.

(18F)-Fluorodeoxyglucose positron emission tomography/magnetic resonance imaging assessment of hypometabolism patterns in clinical phenotypes of suspected corticobasal degeneration.

Corticobasal degeneration (CBD) is a rare neurodegenerative disorder presenting with atypical parkinsonian symptoms that characteristically involves the frontoparietal region including the primary sensorimotor cortex, ipsilateral basal ganglia, and thalamus, typically in an asymmetric pattern. We aim to evaluate the metabolic and volumetric abnormalities in patients with clinically suspected CBD phenotypes utilizing hybrid 18F-fluorodeoxyglucose (FDG) positron emission tomography-magnetic resonance (PET/ MR) brain imaging. A retrospective analysis was performed on 75 patients (mean age 74 years, 31 males and 44 females) who underwent 18F-FDG PET/MR imaging (MRI) as part of their clinical dementia workup. Images were obtained using an integrated Siemens mMR 3T PET/MRI scanner. Two board-certified neuroradiologists and a nuclear medicine physician evaluated the metabolic and volumetric data of each hemisphere to assess for symmetric or asymmetric involvement of regions of interest in the subset of patients with suspected CBD. Of the 75 patients, 12 were diagnosed with suspected CBD based on a combination of clinical symptoms, neurocognitive testing, and hybrid neuroimaging findings. Ten of 12 patients (87%) demonstrated asymmetrically decreased FDG uptake involving a single cerebral hemisphere and ipsilateral subcortical structures, whereas two of 12 patients (13%) demonstrated striking hypometabolism of the bilateral sensorimotor cortices. Our study highlights two characteristic patterns of hypometabolism in patients with clinical and neuroimaging findings suggestive of the underlying CBD. The first pattern is asymmetric hypometabolism and volume loss, particularly within the frontoparietal and occipital cortices with involvement of ipsilateral subcortical structures, including the basal ganglia and thalamus. The second, more atypical pattern, is symmetric hypometabolism with striking involvement of the bilateral sensorimotor cortices.

Olfactory Dysfunction in Neurodegenerative Disease.

ABSTRACT: Familiarity with the physiology of smell allows a deeper understanding of olfactory dysfunction in dementia and neurodegenerative disease. This manuscript reviews the characteristic clinical and advanced imaging findings in patients with neurodegenerative disorders presenting with olfactory dysfunction.

FDG PET/MRI for Visual Detection of Crossed Cerebellar Diaschisis in Patients With Dementia.

OBJECTIVE: Depressed regional metabolism and cerebellar blood flow may be caused by dysfunction in anatomically separate but functionally related regions, presumably related to disruption of the corticopontine-cerebellar pathway. The purpose of this study was to evaluate the prevalence of crossed cerebellar diaschisis (CCD) in patients undergoing 18F-FDG PET/MRI for suspected neurodegenerative disease. MATERIALS AND METHODS: In total, 75 patients (31 men, 44 women; mean age, 74 years) underwent hybrid FDG PET/MRI for clinical workup of neurodegenerative disease. Images were obtained with an integrated 3-T PET/MRI system. PET surface maps, fused T1-weighted magnetization-prepared rapid acquisition gradient echo and axial FLAIR/PET images were generated with postprocessing software. Two board-certified neuroradiologists and a nuclear medicine physician blinded to patient history evaluated for pattern of neurodegenerative disease and CCD. RESULTS: Qualitative assessment showed that 10 of 75 (7.5%) patients had decreased FDG activity in the cerebellar hemisphere contralateral to the supratentorial cortical hypometabolism consistent with CCD. Six of the 10 patients had characteristic imaging findings of frontotemporal dementia (three behavioral variant frontotemporal dementia, two semantic primary progressive aphasia, and one logopenic primary progressive aphasia), three had suspected corticobasal degeneration, and one had Alzheimer dementia. CONCLUSION: Our study results suggest that CCD occurs most commonly in frontotemporal dementia, particularly the behavioral variant, and in patients with cortico-basal degeneration. Careful attention to cerebellar metabolism may assist in the clinical evaluation of patients with cognitive impairment undergoing FDG PET/MRI as part of their routine dementia workup.

Incidental PET/CT Findings of Suspected COVID-19 in a Region of High Prevalence.

We describe a case of suspected COVID-19 pneumonia in a 61-year-old male with known primary central nervous system diffuse large B-cell lymphoma (DLBCL) who underwent restaging PET/CT during the initial peak of infection of COVID-19 pneumonia within the New York region. At the time of his routine PET-CT to assess for disease progression, typical CT imaging features of COVID-19 pneumonia were identified. Upon further investigation, the patient was asymptomatic, and his infection status remained unknown. He was subsequently lost to follow-up with his COVID-19 status pending.

Everything Every Radiologist Always Wanted (and Needs) to Know About Clinical Decision Support.

As of January 2020, clinical decision support needs to be implemented across US health systems for advanced diagnostic imaging services. This article reviews the history, importance, and hurdles of clinical decision support and discusses a few pearls and pitfalls regarding its implementation.

Gender Differences in Article Citations by Authors from American Institutions in Major Radiology Journals.

Objective To investigate gender difference patterns in article citations, by first and last authors, in four radiology journals. Materials and methods Articles by authors published in four major radiology journals from 1984, 1994, 2004, and 2014 were categorized into 12 subspecialties. The number of citations, references used, co-authors, and length of the article (number of pages) were documented. The genders of first/last authors were determined. Data were analyzed using chi-square and logistic regression. Results The gender of the first author was determined in 2679 articles and that of the last author in 2717 articles. Over the selected years, 1984 to 2014, female first authorship grew from 13.0% to 31.5% (p<0.001), and female last authorship grew from 9.3% to 22.1% (p<0.001). Primary female authorship papers were cited less often as compared to males (OR 0.9972, 95% CI: 0.9948-0.9996, p=0.021), after adjusting for publication year and subspecialty. Across most subspecialties, female first authorship received fewer citations. In 1984, primary female authorship papers received on average 28.9 citations versus males at 39.1; in 1994, 50.4 versus 60.8; in 2004, 41.5 versus 44.4; and in 2014, 7.0 versus 7.8. The mean difference in the number of citations received by male and female first authors decreased from 10.47±6.09 in 1984 and 9.49±7.12 in 1994 to 1.93±5.63 in 2004 and 0.79±0.39 in 2014. However, there was no statistical difference demonstrated in article citations between male and female last authorship (OR 0.9990, 95% CI: 0.9966-1.0013, p=0.392). Conclusions Primary female authorship garnered fewer citations than men, despite the increasing frequency of authorships. However, this differential in the number of citations is narrowing.

Comparison of hybrid 18F-fluorodeoxyglucose positron emission tomography/magnetic resonance imaging and positron emission tomography/computed tomography for evaluation of peripheral nerve sheath tumors in patients with neurofibromatosis type 1.

Rapidly enlarging, painful plexiform neurofibromas (PN) in neurofibromatosis type 1 (NF1) patients are at higher risk for harboring a malignant peripheral nerve sheath tumor (MPNST). Fludeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) has been used to support more invasive diagnostic and therapeutic interventions. However, PET/CT imparts an untoward radiation hazard to this population with tumor suppressor gene impairment. The use of FDG PET coupled with magnetic resonance imaging (MRI) rather than CT is a safer alternative but its relative diagnostic sensitivity requires verification. Ten patients (6 females, 4 males, mean age 27 years, range 8-54) with NF1 and progressive PN were accrued from our institutional NF Clinic. Indications for PET scanning included increasing pain and/or progressive disability associated with an enlarging PN on serial MRIs. Following a clinically indicated whole-body FDG PET/CT, a contemporaneous PET/MRI was obtained using residual FDG activity with an average time interval of 3-4 h FDG-avid lesions were assessed for both maximum standardized uptake value (SUVmax) from PET/CT and SUVmax from PET/MR and correlation was made between the two parameters. 26 FDG avid lesions were detected on both PET/CT and PET/MR with an accuracy of 100%. SUVmax values ranged from 1.4-10.8 for PET/CT and from 0.2-5.9 for PET/MRI. SUVmax values from both modalities demonstrated positive correlation (r = 0.45, P < 0.001). PET/MRI radiation dose was significantly lower (53.35% ± 14.37% [P = 0.006]). In conclusion, PET/MRI is a feasible alternative to PET/CT in patients with NF1 when screening for the potential occurrence of MPNST. Reduction in radiation exposure approaches 50% compared to PET/CT.

Visual detection of regional brain hypometabolism in cognitively impaired patients is independent of positron emission tomography-magnetic resonance attenuation correction method.

Fluorodeoxyglucose (FDG) positron emission tomography-magnetic resonance (PET/MR) is useful for the evaluation of cognitively-impaired patients. This study aims to assess two different attenuation correction (AC) methods (Dixon-MR and atlas-based) versus index-standard computed tomography (CT) AC for the visual interpretation of regional hypometabolism in patients with cognitive impairment. Two board-certified nuclear medicine physicians blindly scored brain region FDG hypometabolism as normal versus hypometabolic using two-dimensional (2D) and 3D FDG PET/MR images generated by MIM software. Regions were quantitatively assessed as normal versus mildly, moderately, or severely hypometabolic. Hypometabolism scores obtained using the different methods of AC were compared, and interreader, as well as intra-reader agreement, was assessed. Regional hypometabolism versus normal metabolism was correctly classified in 16 patients on atlas-based and Dixon-based AC map PET reconstructions (vs. CT reference AC) for 94% (90%-96% confidence interval [CI]) and 93% (89%-96% CI) of scored regions, respectively. The averaged sensitivity/specificity for detection of any regional hypometabolism was 95%/94% (P = 0.669) and 90%/91% (P = 0.937) for atlas-based and Dixon-based AC maps. Interreader agreement for detection of regional hypometabolism was high, with similar outcome assessments when using atlas- and Dixon-corrected PET data in 93% (Κ =0.82) and 93% (Κ =0.84) of regions, respectively. Intrareader agreement for detection of regional hypometabolism was high, with concordant outcome assessments when using atlas- and Dixon-corrected data in 93%/92% (Κ =0.79) and 92/93% (Κ =0.78). Despite the quantitative advantages of atlas-based AC in brain PET/MR, routine clinical Dixon AC yields comparable visual ratings of regional hypometabolism in the evaluation of cognitively impaired patients undergoing brain PET/MR and is similar in performance to CT-based AC. Therefore, Dixon AC is acceptable for the routine clinical evaluation of dementia syndromes.

Added Value of Including Entire Brain on Body Imaging With FDG PET/MRI.

OBJECTIVE: FDG PET/MRI examination of the body is routinely performed from the skull base to the mid thigh. Many types of brain abnormalities potentially could be detected on PET/MRI if the head was included. The objective of this study was therefore to identify and characterize brain findings incidentally detected on PET/MRI of the body with the head included. MATERIALS AND METHODS: We retrospectively identified 269 patients with FDG PET/MRI whole-body scans that included the head. PET/MR images of the brain were reviewed by a nuclear medicine physician and neuroradiologist, first individually and then concurrently. Both PET and MRI findings were identified, including abnormal FDG uptake, standardized uptake value, lesion size, and MRI signal characteristics. For each patient, relevant medical history and prior imaging were reviewed. RESULTS: Of the 269 subjects, 173 were women and 96 were men (mean age, 57.4 years). Only the initial PET/MR image of each patient was reviewed. A total of 37 of the 269 patients (13.8%) had abnormal brain findings noted on the PET/MRI whole-body scan. Sixteen patients (5.9%) had vascular disease, nine patients (3.3%) had posttherapy changes, and two (0.7%) had benign cystic lesions in the brain. Twelve patients (4.5%) had serious nonvascular brain abnormalities, including cerebral metastasis in five patients and pituitary adenomas in two patients. Only nine subjects (3.3%) had a new neurologic or cognitive symptom suggestive of a brain abnormality. CONCLUSION: Routine body imaging with FDG PET/MRI of the area from the skull base to the mid thigh may miss important brain abnormalities when the head is not included. The additional brain abnormalities identified on whole-body imaging may provide added clinical value to the management of oncology patients.