Emission Tomography Research Articles

Earth concrete under cyclic loadings: Stress-strain curves and damage assessment by means of acoustic emission and digital image correlation techniques

Cyclic compressive tests were conducted on recycled sand (RS) earth concrete mixtures of different amounts of clay conserved previously at wet and dry curing conditions (relative humidity (RH) = 90% and 50%, respectively). The loops of the stress-strain curves were analyzed. In addition, Kaiser Effect investigation and acoustic emission (AE) damage assessment were carried out. The evaluation showed a successful correlation between the AE indices and cracking progression which was captured by means of digital image correlation (DIC) technique. The results reveal that Kaiser Effect was achieved at wet curing condition whereas it was not attained at the dry one. The RS specimen of highest clay content at dry curing condition demonstrated the highest degree of damage. In line with the journal's aims and scope and as a novelty, this paper finally examines Kaiser Effect by means of DIC. The results revealed that this aspect which is known to be linked with damage occurrence is not necessarily affected by the evolution of crack width.

Investigation of TG-43 Dosimetric Parameters for 192Ir Brachytherapy Source Using GATE Monte Carlo Code

Purpose: According to the revised Task Group number 43 recommendations, a brachytherapy source must be validated against a similar or identical source before its clinical application. The purpose of this investigation is to verify the dosimetric data of the high dose rate (HDR) BEBIG 192Ir source (Ir2.A85-2). Materials and Methods: The HDR 192Ir encapsulated seed was simulated and its main dosimetric data were calculated using Geant4 Application for Tomographic Emission (GATE) simulation code. Cubic cells were used for the calculation of dose rate constant and radial dose function while for anisotropy function ring cells were used. DoseActors were simulated and attached to the respective cells to obtain the required data. Results: The dose rate constant was obtained as 1.098 ± 0.003 cGy.h − 1.U − 1, differing by 1.0% from the reference value reported by Granero et al. Similarly, the calculated values for radial dose and anisotropy functions presented good agreement with the results obtained by Granero et al. Conclusion: The results of this study suggest that the GATE Monte Carlo code is a valid toolkit for benchmarking brachytherapy sources and can be used for brachytherapy simulation-based studies and verification of brachytherapy treatment planning systems.

Synthetic Attenuation Correction Maps for SPECT Imaging Using Deep Learning: A Study on Myocardial Perfusion Imaging.

(1) Background: The CT-based attenuation correction of SPECT images is essential for obtaining accurate quantitative images in cardiovascular imaging. However, there are still many SPECT cameras without associated CT scanners throughout the world, especially in developing countries. Performing additional CT scans implies troublesome planning logistics and larger radiation doses for patients, making it a suboptimal solution. Deep learning (DL) offers a revolutionary way to generate complementary images for individual patients at a large scale. Hence, we aimed to generate linear attenuation coefficient maps from SPECT emission images reconstructed without attenuation correction using deep learning. (2) Methods: A total of 384 SPECT myocardial perfusion studies that used 99mTc-sestamibi were included. A DL model based on a 2D U-Net architecture was trained using information from 312 patients. The quality of the generated synthetic attenuation correction maps (ACMs) and reconstructed emission values were evaluated using three metrics and compared to standard-of-care data using Bland-Altman plots. Finally, a quantitative evaluation of myocardial uptake was performed, followed by a semi-quantitative evaluation of myocardial perfusion. (3) Results: In a test set of 66 test patients, the ACM quality metrics were MSSIM = 0.97 ± 0.001 and NMAE = 3.08 ± 1.26 (%), and the reconstructed emission quality metrics were MSSIM = 0.99 ± 0.003 and NMAE = 0.23 ± 0.13 (%). The 95% limits of agreement (LoAs) at the voxel level for reconstructed SPECT images were: [-9.04; 9.00]%, and for the segment level, they were [-11; 10]%. The 95% LoAs for the Summed Stress Score values between the images reconstructed were [-2.8, 3.0]. When global perfusion scores were assessed, only 2 out of 66 patients showed changes in perfusion categories. (4) Conclusion: Deep learning can generate accurate attenuation correction maps from non-attenuation-corrected cardiac SPECT images. These high-quality attenuation maps are suitable for attenuation correction in myocardial perfusion SPECT imaging and could obviate the need for additional imaging in standalone SPECT scanners.

Dosimetric assessment of Gadolinium-159 for hepatic radioembolization: Tomographic images and Monte Carlo simulation

A common therapeutic radionuclide used in hepatic radioembolization is yttrium-90 (90Y). However, the absence of gamma emissions makes it difficult to verify the post-treatment distribution of 90Y microspheres. Gadolinium-159 (159Gd) has physical properties that are suitable for therapy and post-treatment imaging in hepatic radioembolization procedures. The current study is innovative for conducting a dosimetric investigation of the use of 159Gd in hepatic radioembolization by simulating tomographic images using the Geant4 application for tomographic emission (GATE) Monte Carlo (MC) simulation. For registration and segmentation, tomographic images of five patients with hepatocellular carcinoma (HCC) who had undergone transarterial radioembolization (TARE) therapy were processed using a 3D slicer. The tomographic images with 159Gd and 90Y separately were simulated using the GATE MC Package. The output of simulation (dose image) was uploaded to 3D slicer to compute the absorbed dose for each organ of interests. 159Gd were able to provide a recommended dose of 120 Gy to the tumour, with normal liver and lungs absorbed doses close to that of 90Y and less than the respective maximum permitted doses of 70 Gy and 30 Gy, respectively. Compared to 90Y, 159Gd requires higher administered activity approximately 4.92 times to achieve a tumour dose of 120 Gy. Thus; this research gives new insights into the use of 159Gd as a theranostic radioisotope, with the potential to be used as a90Y alternative for liver radioembolization.

Effect of triaxial woven fabric on bending properties of unidirectional composites

AbstractThis study investigates the impact of incorporating a triaxial woven fabric (TWF) into a unidirectional ply structure on the bending performance of the structure. The failure processes of the different ply structures were recorded using video analysis and acoustic emission. The experimental results indicated that incorporating a layer of carbon fiber TWF between the second and third layers (GGTGG) or between the third and fourth layers (GGGTG) of the four‐layer unidirectional fabric significantly improved the flexural strengths by 79.5% and 213.7%, respectively, and the flexural toughness by 480.3% and 324.8%, respectively. In addition, the incorporation of TWF in the structure resulted in a shift in the overall failure mode from brittle to ductile. When the TWF was closer to the lower surface of the sample, the crack was more uniform and the distribution range was wider. In contrast when the TWF was in the middle, the range of cracks generated by the sample was narrower. However, some of these cracks affected the stability of the material structure. Furthermore, the damage process was confirmed using images of crack growth and acoustic emission during the destruction process. This study provides valuable insights into enhancing the bending performance of unidirectional fiber layup in the non‐load direction.

Neutron Pinhole Characterization and Analysis for Three-Dimensional As-Built Model Reconstruction

The neutron pinhole array, used to collect neutron burn, X-ray, and more recently, gamma emission images, has been in use at the National Ignition Facility since 2011. Since then, there has been the ever-continuing challenge of meeting tighter alignment and resolution requirements. Part of that challenge is being able to accurately characterize the as-built variances from the nominal design associated with the manufacturing and assembly of the pinhole array. To overcome this specific challenge, multiple processes are taken to obtain high-precision profiles of the various features of each pinhole array. This paper highlights the processes used as well as the steps taken to compile the significant amount of data and turn it into an accurate as-built reconstructed model of the NIS1-U–assembled pinhole array.

Updating 90Y Voxel S-Values including internal Bremsstrahlung: Monte Carlo study and development of an analytical model

PurposeInternal Bremsstrahlung (IB) is a process accompanying β-decay but neglected in Voxel S-Values (VSVs) calculation. Aims of this work were to calculate, through Monte Carlo (MC) simulation, updated 90Y-VSVs including IB, and to develop an analytical model to evaluate 90Y-VSVs for any voxel size of practical interest. MethodsGATE (Geant4 Application for Tomographic Emission) was employed for simulating voxelized geometries of soft tissue, with voxels sides l ranging from 2 to 6 mm, in steps of 0.5 mm. The central voxel was set as a homogeneous source of 90Y when IB photons are not modelled. For each l, the VSVs were computed for 90Y decays alone and for 90Y + IB. The analytical model was then built through fitting procedures of the VSVs including IB contribution. ResultsComparing GATE-VSVs with and without IB, differences between + 25% and + 30% were found for distances from the central voxel larger than the maximum β-range. The analytical model showed an agreement with MC simulations within ± 5% in the central voxel and in the Bremsstrahlung tails, for any l value examined, and relative differences lower than ± 40%, for other distances from the source. ConclusionsThe presented 90Y-VSVs include for the first time the contribution due to IB, thus providing a more accurate set of dosimetric factors for three-dimensional internal dosimetry of 90Y-labelled radiopharmaceuticals and medical devices. Furthermore, the analytical model constitutes an easy and fast alternative approach for 90Y-VSVs estimation for non-standard voxel dimensions.

Refueling the post COVID-19 brain: potential role of ketogenic medium chain triglyceride supplementation: an hypothesis.

COVID-19 infection causes cognitive changes in the acute phase, but also after apparent recovery. Over fifty post (long)-COVID symptoms are described, including cognitive dysfunction ("brain fog") precluding return to pre-COVID level of function, with rates twice as high in females. Additionally, the predominant demographic affected by these symptoms is younger and still in the workforce. Lack of ability to work, even for six months, has significant socio-economic consequences. This cognitive dysfunction is associated with impaired cerebral glucose metabolism, assessed using 18F-fluorodeoxyglucose-positron emission tomography (FDG-PET), showing brain regions that are abnormal compared to age and sex matched controls. In other cognitive conditions such as Alzheimer's disease (AD), typical patterns of cerebral glucose hypometabolism, frontal hypometabolism and cerebellar hypermetabolism are common. Similar FDG-PET changes have also been observed in post-COVID-19, raising the possibility of a similar etiology. Ketone bodies (B-hydroxybutyrate, acetoacetate and acetone) are produced endogenously with very low carbohydrate intake or fasting. They improve brain energy metabolism in the face of cerebral glucose hypometabolism in other conditions [mild cognitive impairment (MCI) and AD]. Long-term low carbohydrate intake or prolonged fasting is not usually feasible. Medium chain triglyceride (MCT) is an exogenous route to nutritional ketosis. Research has supported their efficacy in managing intractable seizures, and cognitive impairment in MCI and AD. We hypothesize that cerebral glucose hypometabolism associated with post COVID-19 infection can be mitigated with MCT supplementation, with the prediction that cognitive function would also improve. Although there is some suggestion that post COVID-19 cognitive symptoms may diminish over time, in many individuals this may take more than six months. If MCT supplementation is able to speed the cognitive recovery, this will impact importantly on quality of life. MCT is readily available and, compared to pharmaceutical interventions, is cost-effective. Research shows general tolerability with dose titration. MCT is a component of enteral and parenteral nutrition supplements, including in pediatrics, so has a long record of safety in vulnerable populations. It is not associated with weight gain or adverse changes in lipid profiles. This hypothesis serves to encourage the development of clinical trials evaluating the impact of MCT supplementation on the duration and severity of post COVID-19 cognitive symptoms.

Study on Acoustic Emission Characteristics of Fatigue Damage of A7N01 Aluminum Alloy for High-Speed Trains.

Online monitoring of the fatigue damage process of A7N01 aluminum alloy base metal and weld seam was conducted based on acoustic emission (AE) and digital microscopic imaging technology. The AE signals were recorded during the fatigue tests and analyzed using the AE characteristic parameter method. Fatigue fracture was observed using scanning electron microscopy (SEM) to analyze the source mechanism of AE. The AE results show that the AE count and rise time can effectively predict the initiation of fatigue microcracks in A7N01 aluminum alloy. The digital image monitoring results of a notch tip verified the prediction of fatigue microcracks using the AE characteristic parameters. In addition, the AE characteristics of the A7N01 aluminum alloy under different fatigue parameters were studied, and the relationships between the AE characteristic values of the base metal and weld seam and the crack propagation rate were calculated using the seven-point recurrence polynomial method. These provide a basis for predicting the remaining fatigue damage in the A7N01 aluminum alloy. The present work indicates that AE technology can be used to monitor the fatigue damage evolution of welded aluminum alloy structures.

Monte Carlo simulation of the system performance of a long axial field-of-view PET based on monolithic LYSO detectors

BackgroundIn light of the milestones achieved in PET design so far, further sensitivity improvements aim to optimise factors such as the dose, throughput, and detection of small lesions. While several longer axial field-of-view (aFOV) PET systems based on pixelated detectors have been installed, continuous monolithic scintillation detectors recently gained increased attention due to their depth of interaction capability and superior intrinsic resolution. As a result, the aim of this work is to present and evaluate the performance of two long aFOV, monolithic LYSO-based PET scanner designs.MethodsGeant4 Application for Tomographic Emission (GATE) v9.1 was used to perform the simulations. Scanner designs A and B have an aFOV of 36.2 cm (7 rings) and 72.6 cm (14 rings), respectively, with 40 detector modules per ring each and a bore diameter of 70 cm. Each module is a 50 × 50 × 16 mm3 monolithic LYSO crystal. Sensitivity, noise equivalent count rate (NECR), scatter fraction, spatial resolution, and image quality tests were performed based on NEMA NU-2018 standards.ResultsThe sensitivity of design A was calculated to be 29.2 kcps/MBq at the centre and 27 kcps/MBq at 10 cm radial offset; similarly, the sensitivity of design B was found to be 106.8 kcps/MBq and 98.3 kcps/MBq at 10 cm radial offset. NECR peaks were reached at activity concentrations beyond the range of activities used for clinical studies. In terms of spatial resolution, the values for the point sources were below 2 mm for the radial, tangential, and axial full width half maximum. The contrast recovery coefficient ranged from 53% for design B and 4:1 contrast ratio to 90% for design A and 8:1 ratio, with a reasonably low background variability.ConclusionsLonger aFOV PET designs using monolithic LYSO have superior spatial resolution compared to current pixelated total-body PET (TB-PET) scanners. These systems combine high sensitivity with improved contrast recovery.

Fatigue damage monitoring of composite laminates based on acoustic emission and digital image correlation techniques

Timely and effective health evaluation of carbon fiber reinforced polymer (CFRP) structures under dynamic fatigue loading is one of the key issues of CFRP in practical engineering applications. This paper uses a combination of acoustic emission (AE) and digital image correlation (DIC) to study the fatigue behavior of CFRP open-hole laminated beams with different stacking sequences under pure tensile loading, and analyze the influence of different damage mechanisms on the ultimate fatigue failure of the specimens. Two parameters, AE hit rate and absolute AE energy, are used to characterize the stiffness degradation behavior of CFRP structures. The strain field distribution characteristics during the damage failure of specimens with different stacking sequences are discussed in association with DIC. Based on the data obtained by AE and DIC, the damage modes of two types of layered CFRP laminated beams are identified by combining principal component analysis (PCA) and the K-means++ algorithm. The clustering results are consistent with the microscopic image results of the fracture surface. The identified modes are employed to characterize the dynamic evolution of fatigue damage in CFRP, and the contribution of different damage modes to the ultimate fatigue failure of the specimens is analyzed using cumulative damage index (CDI) values.

Post-treatment 18F-fludeoxyglocuse-positron emission tomography in human papillomavirus-associated oropharyngeal cancer.

Human papillomavirus association has changed the landscape of treatment for oropharyngeal squamous cell carcinoma; it remains to be seen whether current post-treatment surveillance schedules are effective. Evaluate whether post-treatment surveillance of oropharyngeal cancer through FDG-PET imaging is modified by human papillomavirus association. A prospective cohort analysis of retrospective data was conducted for patients undergoing treatment of oropharyngeal cancer between 2016 and 2018. This study was conducted at a single large tertiary referral center in Brisbane, Australia. Two-hundred and twenty-four patients were recruited for the purposes of the study, 193 (86%) with HPV-associated disease. In this cohort FDG-PET had a sensitivity of 48.3%, specificity of 72.6%, positive predictive value of 23.7%, and negative predictive value of 88.8% in detecting disease recurrence. FDG-PET in HPV-associated oropharyngeal cancer has significantly lower positive predictive value when compared to non-HPV-associated oropharyngeal cancer. Caution should be used when interpreting positive post-treatment FDG-PET.

New Insights from Imaging Spectroscopy of Solar Radio Emission

Newly available high-resolution imaging of solar radio emission at many closely spaced frequencies and times provides new physical insight into the processes, structure, and dynamics of the solar atmosphere. The observational advances have spurred renewed interest in topics dating from the early days of solar radio astronomy and have led to considerable advances in our knowledge. Highlights of recent advances include the following: ▪Quantitatively measuring the dynamic magnetic field strength, particle acceleration, and hot thermal plasma at the heart of solar flares and hinting at the processes that relate them.▪Resolving in space and time the energization and transport of electrons in a wide range of contexts.▪Mapping the magnetized thermal plasma structure of the solar chromosphere and corona over a substantial range of heights in active and quiet regions of the Sun. This review explains why solar radio imaging spectroscopy is so powerful, describes the body of recent results, and outlines the future work needed to fully realize its potential. The application of radio imaging spectroscopy to stars and planets is also briefly reviewed.

Fracture performance and damage behavior of fly ash-based geopolymers toughened by molybdenum tailings based on acoustic emission and digital image correlation

This research proposes the utilization of molybdenum tailings (MT) to toughen fly ash-based geopolymers. To fully understand the effect of MT on the fracture performance and damage behavior of fly ash-based geopolymers, the effect of mode I fracture toughness and fracture energy of fly ash-based geopolymers with different MT contents were researched by using semi-circular bending (SCB) tests. The damage and strain behavior of the semi-circular bending with notches (NSCB) specimens during the fracture process were evaluated by acoustic emission (AE) technology and digital image correlation (DIC) technology, and finally the micromorphology of the fracture surface of NSCB specimens after the loading finished were observed by scanning electron microscopy (SEM). The results show that the tensile strength, fracture toughness and fracture energy of fly ash-based geopolymers were significantly increased with the addition of MT, and the peak value was reached at 30 wt% MT contents, with the increase amplitude reaching 77%, 31% and 45% respectively. This was attributed to the filling effect of MT, which made the structure of fly ash-based geopolymers more dense, reduced the formation and expansion of internal microcracks, shifted the growth direction of microcracks from the pore structure to the gel phase and the interface between the gel phase and glassy microspheres during the fracture process, improved the stability of the structure and the fracture resistance.

Mapping and litho‐geophysical classification of potential mining areas by spatial remote sensing and helicopter‐borne gamma‐ray spectrometry (Tikirt, Anti‐Atlas, Morocco)

AbstractThe primary focus of this study is to explore the potential mineral areas. Advanced Spaceborne Thermal Emission and Reflection Radiometer images and radiometric data were combined in the Tikirt region to map hydrothermal alteration zones associated with mineralized deposits. Advanced Spaceborne Thermal Emission and Reflection Radiometer images were analysed using band ratios, principal component analysis and a fuzzy logic model to discover argillic, phyllic, propylitic and iron oxide alterations and to generate a mineral prospectivity map. In addition, mono‐element maps of radiometric elements (K in %, eU in ppm, eTh in ppm) and their behaviour in the ternary image have been elaborated to determine the concentrations of radiometric elements and the variation of radiometric character along the exposed terrains. The F parameter was calculated to target high potassium concentration areas associated with hydrothermal alteration zones. Combining the two methods highlighted four hydrothermal alteration zones considered very promising from a mining point of view. These zones are generally linked to the magma bodies affected by normal faults and exhibit a clear spatial correlation with mineral occurrences.

Activating ultralow upconversion nanothermometry in neodymium sublattice for heart tissue imaging rapid-responsive

The fields of biosensitivity and biological imaging have received a lot of attention from rare earth-doped upconversion nanoparticles (UCNPs). However, owing to the relatively large energy difference of rare earth ions, biological sensitivity based on UCNPs is restricted to detect at low temperature. Here, we design core-shell-shell NaErF4:Yb@Nd2O3@SiO2 UCNPs as a dual-mode bioprobe that produces blue, green, and red multi-color upconversion emissions at extremely low temperatures between 100 K and 280 K. Based on the thermally coupled energy levels (TCELs) of Er3+ (2H11/2 and 4S3/2) and Nd3+ (4F5/2 and 4F3/2) at 100 K, the greatest relative sensitivity (SR) approaches 12.7% K−1. NaErF4:Yb@Nd2O3@SiO2 injection is used to achieve blue upconversion emission imaging of frozen heart tissue, showing that this UCNP can serve as a low-temperature sensitive biological fluorescence.

Strain field evolution and crack coalescence mechanism of composite strength rock-like specimens with sawtooth interface

The mechanical behaviors of composite rock masses containing a complex interface widely distributed in nature are significantly different from those of monolithic rock masses. The objective of this study is to perform a series of uniaxial compression tests to study the influence of sawtooth interface parameters on the fracture behavior of rock-like composite specimens. Meantimes, the acoustic emission (AE) and digital image correlation (DIC) technique were used to classify damage stages and record strain field evolution, respectively. The results of this study demonstrate that stress–strain curves of composite rock-like specimens with different sawtooth interfaces display characteristics of plastic failure, friction failure characteristics and two different brittle failure characteristics in the post-peak phase. The peak strength of the specimen first decreases and then increases as the inclination of the interface increases, achieving the maximum value of 28.29 MPa at the inclined interface of 90°. The strain concentration zone is mainly generated and expanded around the interface. The parameters of the sawtooth have a significant influence on the type and location of cracks developed along the interface. In addition, there is a strong relationship between the mode of failure of the specimen and the strength of the rock layer and the inclination of the interface. According to the relative positional relationship between the coalescence path of the specimen and the interface, the failure modes of the specimen are classified as single weak rock layer failure (S-AB-0, S-AB-15), oblique failure through rock layer interface (S-AB-30, S-AB-45), slip failure along the interface (S-AB-60, S-AB-75) and axisymmetric failure along the interface (S-AB-90). This result is of great importance for a thorough understanding of the crack coalescence mechanism and strain field evolution of rock-like composite specimens.

Machine vision inspection of early failure and line-shaped defects of blue InGaN/GaN light emitting diodes soaked in liquid nitrogen for cryogenic tests

Cryogenic tests were conducted on blue InGaN/GaN light-emitting diodes (LEDs) by immersing the device in liquid nitrogen (LN2). To study the degradation of the LEDs, a combination of optical, electrical, and material characterizations were performed on the LN2-soaked device. The results indicate that noticeable emission spectral shifts were observed during the LED immersion due to lattice deformation. Moreover, clustering of cracks was generated in the cross-section, and line-shaped defects appeared on the surface of the GaN LED, which was different from the defects on AlInGaP LEDs after LN2 immersion. To track the trend of device damage, computer-assisted OpenCV-Python software was used to zoom in on nuanced variations in certain areas of the emission images. Early degradation of certain areas can be detected by computer-assisted machine vision, which has the potential to provide an early warning and protective circuits for the system consisting of the initial degraded LEDs. Reliability studies on LN2-soaked InGaN/GaN LEDs show promise in studying the reliability issues of GaN device applications in Arctic regions and space exploration.

A longitudinal 18F‐FDG PET study in asymptomatic stage of genetic Creutzfeldt–Jakob disease

AbstractBackgroundPathogenic prion protein may start to deposit in some brain regions and cause functional alterations in the asymptomatic stages in Creutzfeldt–Jakob disease patients. However, the disease trajectory of Creutzfeldt–Jakob disease in the asymptomatic stage and when and where the degenerative process begins are still not clear.MethodsAt baseline, we enrolled five asymptomatic mutation carriers, six affected genetic Creutzfeldt–Jakob diseasepatients, and 23 healthy controls from whom 18F fluorodeoxyglucose‐positron emission tomography, clinical, and neuropsychological measures were acquired. Only five asymptomatic mutation carriers had completed longitudinal follow‐up. We set three‐time points to identify the changing trajectory in asymptomatic carriers group including baseline, 2‐year and 4‐year follow‐up.ResultsAt baseline, the cerebral glucose metabolic rate, measured as the standardized uptake value rate ratio, clinical and neuropsychological scales in all 5 asymptomatic cases were normal. In the 4‐years follow‐up, hypometabolic brain regions in asymptomatic genetic Creutzfeldt–Jakob disease group were found in the insula, frontal, parietal, and temporal lobes (false discovery rate corrected p<0.01). The standardized uptake value rate ratio changing trajectories of all asymptomatic cases were within the range between the healthy controls and affected patients. Notably, the metabolism values of one asymptomatic individual whose baseline age was older than the expected age of onset showed a rapid decline and approached the mean value of genetic Creutzfeldt–Jakob disease condition at the last follow‐up.ConclusionOur study illustrates that neurodegenerative process associated with genetic Creutzfeldt–Jakob disease may involve the insula, frontal, temporal, and parietal lobes before clinical presentation of the disease, and the decline will accelerate when close to the expected age of onset. Although there are no effective means to cure this fatal disease, the time interval before clinical disease onset may aid important trials or therapies intended to slow or halt the disease process.

“Probable 4R‐tauopathy” criteria in a Corticobasal Syndrome cohort: diagnostic accuracy, clinical, metabolic and volumetric patterns in a multimodal PET/MRI study

AbstractBackgroundCorticobasal syndrome (CBS) is a neurodegenerative disease related to multiple underlying pathologies, including four‐repeat (4R) tauopathies, namely corticobasal degeneration (CBD) and progressive supranuclear palsy (PSP), Alzheimer’s disease (AD), among others. The Movement Disorders Society‐PSP clinical criteria proposed a diagnostic category “probable 4R‐tauopathy” to include the phenotypic overlap between PSP and CBD. These criteria were specific for 4R‐tauopathies in a previous post‐mortem validation study. We aimed to investigate this proposed criteria in a cohort of patients clinically diagnosed with probable CBS, comparing the CBS‐4R tau group regarding neurological assessment, brain atrophy patterns, functional and disease‐specific imaging biomarkers. Also, we compared this group with CBS patients that matched the clinical research (cr) criteria for CBD.MethodThirty‐two patients diagnosed with probable CBS were prospectively enrolled and clinically evaluated. They were split into those who fulfilled criteria for probable 4R‐tauopathy (CBS‐4RT = 12) and probable CBD (CBS‐CBD = 28). They underwent [18F]fluorodeoxyglucose‐positron emission tomography (FDG‐PET) and [11C]Pittsburgh Compound‐B (PIB‐PET) on a hybrid PET‐MRI to assess their amyloid status. PIB‐PET images were classified individually based on visual and 3D‐SSP semi‐quantitative analysis. Quantitative group analyses were performed with SPM12, to check both brain atrophy patterns using voxel‐based morphometry (VBM), and regional brain hypometabolism patterns with FDG‐PET. A healthy control group of 30 subjects, matched by age and education, was also included.ResultOnly one patient classified as CBS‐4RT was positive at PIB‐PET (p = 0.010), compared to 12 among 28 CBS‐CBD subjects (p = 0.458). The CBS‐4RT clinical classification had 52.6% sensitivity, 92.3% specificity, and 68.7% accuracy in predicting a negative PIB‐PET result. Also, CBS‐4RT patients presented dysarthria (p = 0.017) and motor perseveration (p = 0.032) more often than the whole group. CBS‐4RT patients showed asymmetric hypometabolism in the inferior, middle, and superior frontal gyri, supplementary motor area, and caudate compared to controls. They also demonstrated brain atrophy in the superior and inferior frontal gyri and basal ganglia.ConclusionThe new proposed clinical 4R‐tauopathies criteria demonstrated high specificity to detect amyloid‐negative CBS patients. Patients fulfilling the criteria presented specific metabolic and volumetric patterns. Moreover, they presented clinical characteristics such as dysarthria and motor perseveration previously related to tauopathies.