Preliminary Imaging Research Articles

460 Frame Navigation Guided Percutaneous Balloon Compression for Intractable Trigeminal Neuralgia Secondary to Multiple Sclerosis

INTRODUCTION: Patients with multiple sclerosis (MS) are more likely to develop trigeminal neuralgia (TN) compared to the regular population, due to scarring of the nerve and the development of a demyelination plaque. Despite treatment, approximately 10% of MS patients treated for TN experience symptom recurrence, including the development of MS-like symptoms such as optic neuritis and bilateral facial pain. METHODS: A computed tomography (CT) scan was performed preoperatively on two patients diagnosed with multiple sclerosis (MS) who experienced secondary trigeminal neuralgia (TN). The acquired images were then introduced into a navigation system for intraoperative navigation. The preliminary CT images were registered using the navigation system and the bony landmarks were set. Fluoroscopy-guided cannulation was performed under general anesthesia to complete the procedure. RESULTS: Two patients diagnosed with multiple sclerosis (MS) who experienced refractory trigeminal neuralgia (TN) underwent percutaneous balloon compression. The patients were 38 and 56 years old and complained of facial pain in the V1-V2 and V3 distribution. Initial conservative treatment and one dosage of Gamma Knife Radiosurgery (GKR) resulted in symptom control for a few weeks. However, both patients had an acute recurrence of pain; thus, percutaneous retrogasserian balloon compression was performed. During follow-up, the patients reported a 70% decrease in pain after the procedure, with minimal recurrence of shooting episodes. CONCLUSIONS: The management of trigeminal neuralgia secondary to drug-resistant multiple sclerosis presents a persistent challenge. The percutaneous technique for retrogasserian balloon compression may offer a solution for some patients, but it can be technically challenging. Microvascular decompression remains a debated approach for this population, given the complexity of the pathogenesis, target identification, and the potential absence of neurovascular conflict, while stereotactic radiosurgery may be a promising alternative.

Development of Pyridothiophene Compounds for PET Imaging of α-Synuclein.

Aggregated α-synuclein (α-syn) protein is a pathological hallmark of Parkinson's disease (PD) and Lewy body dementia (LBD). Development of positron emission tomography (PET) radiotracers to image α-syn aggregates has been a longstanding goal. This work explores the suitability of a pyridothiophene scaffold for α-syn PET radiotracers, where 47 derivatives of a potent pyridothiophene (asyn-44; Kd=1.85 nM) were synthesized and screened against [3H]asyn-44 in competitive binding assays using post-mortem PD brain homogenates. Equilibrium inhibition constant (Ki) values of the most potent compounds were determined, of which three had Ki's in the lower nanomolar range (12-15 nM). An autoradiography study confirmed that [3H]asyn-44 is promising for imaging brain sections from multiple system atrophy and PD donors. Fluorine-18 labelled asyn-44 was synthesized in 6±2 % radiochemical yield (decay-corrected, n=5) with a molar activity of 263±121 GBq/μmol. Preliminary PET imaging of [18F]asyn-44 in rats showed high initial brain uptake (>1.5 standardized uptake value (SUV)), moderate washout (~0.4 SUV at 60 min), and low variability. Radiometabolite analysis showed 60-80 % parent tracer in the brain after 30 and 60 mins. While [18F]asyn-44 displayed good in vitro properties and acceptable brain uptake, troublesome radiometabolites precluded further PET imaging studies. The synthesis and in vitro evaluation of additional pyridothiophene derivatives are underway, with the goal of attaining improved affinity and metabolic stability.

Rhenium fac-Tricarbonyl Bisimine Chalcogenide Complexes: Synthesis, Photophysical Studies, and Confocal and Time-Resolved Cell Microscopy.

We describe the preparation, characterization, and imaging studies of rhenium carbonyl complexes with a pyta (4-(2-pyridyl)-1,2,3-triazole) or tapy (1-(2-pyridyl)-1,2,3-triazole)-based heteroaromatic N∧N ligand and thiolate or selenoate X ligand. The stability and photophysical properties of the selenolate complexes are compared with parent chloride complexes and previously described analogues with benzenethiolate ligands. Two complexes were imaged in A549 cells upon excitation at 405 nm. Colocalization studies suggest a lysosomal accumulation, while one parent chloride complex was described to localize at the Golgi apparatus. Preliminary fluorescence lifetime measurements and imaging demonstrate potential for application in time-resolved microscopy techniques due to the long and variable lifetimes observed in cellular environments, including an increase in lifetime between the solution and solid state many times larger than previously reported.

Preparation and characterization of inactivated tick-borne encephalitis virus samples for single-particle imaging at the European XFEL.

X-ray imaging of virus particles at the European XFEL could eventually allow their complete structures to be solved, potentially approaching the resolution of other structural virology methods. To achieve this ambitious goal with today's technologies, about 1 ml of purified virus suspension containing at least 1012 particles per millilitre is required. Such large amounts of concentrated suspension have never before been obtained for enveloped viruses. Tick-borne encephalitis virus (TBEV) represents an attractive model system for the development of enveloped virus purification and concentration protocols, given the availability of large amounts of inactivated virus material provided by vaccine-manufacturing facilities. Here, the development of a TBEV vaccine purification and concentration scheme is presented combined with a quality-control protocol that allows substantial amounts of highly concentrated non-aggregated suspension to be obtained. Preliminary single-particle imaging experiments were performed for this sample at the European XFEL, showing distinct diffraction patterns.

Fraunhofer diffraction at the two-dimensional quadratically distorted (QD) grating.

A two-dimensional (2D) mathematical model of quadratically distorted (QD) grating is established with the principles of Fraunhofer diffraction and Fourier optics. A discrete sampling method is applied for finding a numerical solution of the diffraction pattern of QD grating. An optimized working phase term, which determines the balanced energies and high efficiency of multi-plane images, can be obtained by the bisection algorithm. To confirm the analytical approach described above, the results have been compared with those obtained using a classical numerical model based on Fraunhofer diffraction theory and a fast Fourier transform (FFT) algorithm. The results show that our analytical approach allows the precise design of QD grating and improves the optical performance of simultaneous multi-plane imaging system. An optical setup based on our well-designed QD grating has been appended to the camera port of a commercial microscope, and some preliminary microscopy images have been successfully obtained. Further upgrade of our analytical model is in progress to improve the image quality and promote the applications.

Cognitive sequealae of COVID‐19 is not predicted by SARS‐CoV‐2 variants

AbstractBackgroundThe long term sequelae of COVID‐19 in older adults are only beginning to be clarified, and its predictors and underlying molecular mechanisms may shed light on the relationship between viral infections and Alzheimer’s disease and related dementia.MethodA prospective cohort of 874 older adult Amerindians from Argentina with COVID‐19 illness confirmed by PCR of nasal swabs as well as controls, was established during the first year of the COVID‐19 pandemic. We obtained data on the severity of the acute illness, as well as extensive neuropsychiatric and cognitive assessments, neurological exams (including quantitative hyposmia/anosmia), plasma for biomarkers and preliminary brain MRI images using the ADNI‐3 protoco (n = 300)l,and whole genome sequencing (n = 300). Isolates from SARS‐CoV‐2 were obtained by the provincial Direction of Epidemiology and sequenced by the national Ministry of Health. Variants of interest/concern were allocated to each case on the basis of the prevalent community isolate at the time of confirmed positive PCR. A deep learning strategy was used to identify predictive factors of cognitive and clinical outcomes.ResultFour distinctive cognitive profiles were identified. Greater cognitive impairment was associated with older age (p = E−9), worse acute COVID‐19 illness (p = 0.008), unvaccinated status (p = E−7), and severity of anosmia (p = E−5). SARS‐CoV‐2 variant was associated with severity of acute illness ((p = E−6) but notably not with cognitive impairment. Preliminary analysis of genomic and brain imaging data will be presented.ConclusionOur data strongly suggest that all SARS‐CoV‐2 variants of interest up to the omicron wave seem equally likely to result in cognitive impairment in older adults, modulated by the severity of the acute illness.

Nanoscale analysis of magnetic chains consisting of cobalt mesospheres by full‐field transmission x‐ray tomography

AbstractFull‐field transmission x‐ray tomography can obtain 3D morphology and configurations of nanoscale materials. In this study, we further demonstrate the feasibility of this technique using magnetic chains consisting of cobalt mesospheres. The preliminary images presented in this article clearly reveal that three types of cobalt nanoparticles, namely, hollow, core–shell, and solid were found for magnetic chain synthesis. Furthermore, the tomographic analyses revealed the growth mechanism of magnetic chains self‐assembled by cobalt nanoparticles. We may claim that the spatial resolution and contrast characteristics of the full‐field transmission x‐ray tomography can satisfy the research requirements of nanomaterial science. Hence, transmission x‐ray tomography could be a powerful complementary method for imaging and analysis of nanoscale materials.

Compressive color ghost imaging based on pseudo-inverse matrix

In this paper, a compressive color ghost imaging method based on pseudo-inverse matrix is proposed, which improves the quality of imaging result via post-processing the measurement matrix. For a color ghost imaging utilizing compressive sensing algorithm, if we treat a color image as a form of grayscale image and perform pseudo-inverse operation on the measurement matrix, a new measurement model will be established and the preliminary ghost imaging reconstruction result can be obtained by the compressive sensing algorithm, then the preliminary result is converted into a superposition of three channels to form the final color image. The feasibility of this method is proved by numerical simulation and physical experiment, and comparations among our method and the latest typical improvement methods, i.e., the singular value decomposition compressive ghost imaging and the pseudo-inverse ghost imaging, are conducted. The results show that our method can achieve the better quality of reconstructed color image with a high structure similarity beyond 0.8.

Phytochemical fingerprinting and evaluation of in silico anti-thrombotic properties of Justicia adhatoda L. and Cordia dichotoma Frost.

The study aimed to characterize hydro-methanolic (25%) extracts of Justicia adhatoda L. (stem and flower) and Cordia dichotoma Frost. (Stem and fruit) and evaluate the in silico thrombolytic properties of the major phytocompounds present in the plants. In the preliminary fluorescence imaging through treatment by different reagents, both plants were found to be pharmacologically active. Further qualitative screening of phytochemicals, spectroscopy-based techniques, namely, UV-Vis Spectroscopy and FTIR, revealed various classes of compounds such as polyacetylenes, aglycones, quercetin, anthocyanins, anthraquinones, alkaloids, chalcones and aurones, flavanols, carotenoids, and flavanones. Further, by the application of Thin Layer Chromatography, phenols and flavonoids, namely Catechol, Kaempferol, Quercetin, and Lutein, along with other compounds like Chlorophyll b, Glutamic Acid, and Tryptophan were identified from the extracts. Finally, in the molecular docking study, three compounds, Datiscoside and Robinin of C. dichotoma and Daucosterol of J. adhatoda showed high binding energies (-10.224, -9.547 and -9.262 kcal mol-1 respectively) towards the G-protein coupled thrombotic platelet aggregation receptor P2Y1 when compared to that of the control MRS2500 (-7.148 kcal mol-1).

Preliminary PET Imaging of Microtubule-Based PET Radioligand [11C]MPC-6827 in a Nonhuman Primate Model of Alzheimer's Disease.

The microtubule (MT) instability observed in Alzheimer's disease (AD) is commonly attributed to hyperphosphorylation of the MT-associated protein, tau. In vivo PET imaging offers an opportunity to gain critical information about MT changes with the onset and development of AD and related dementia. We developed the first brain-penetrant MT PET ligand, [11C]MPC-6827, and evaluated its in vivo imaging utility in vervet monkeys. Consistent with our previous in vitro cell uptake and in vivo rodent imaging experiments, [11C]MPC-6827 uptake increased with MT destabilization. Radioactive uptake was inversely related to (cerebrospinal fluid) CSF Aβ42 levels and directly related to age in a nonhuman primate (NHP) model of AD. Additionally, in vitro autoradiography studies also corroborated PET imaging results. Here, we report the preliminary results of PET imaging with [11C]MPC-6827 in four female vervet monkeys with high or low CSF Aβ42 levels, which have been shown to correlate with the Aβ plaque burden, similar to humans.

Imaging characterization of myocardial function, fibrosis, and perfusion in a nonhuman primate model with heart failure-like features.

The availability of a human-like chronic heart failure (HF) animal model was critical for affiliating development of novel therapeutic drug treatments. With the close physiology relatedness to humans, the non-human primate (NHP) HF model would be valuable to better understand the pathophysiology and pharmacology of HF. The purpose of this work was to present preliminary cardiac image findings using echocardiography and cardiovascular magnetic resonance (CMR) in a HF-like cynomolgus macaque model. The NHP diet-induced model developed cardiac phenotypes that exhibited diastolic dysfunction with reduced left ventricular ejection fraction (LVEF) or preserved LVEF. Twenty cynomolgus monkeys with cardiac dysfunction were selected by echocardiography and subsequently separated into two groups, LVEF < 65% (termed as HFrEF, n = 10) and LVEF ≥ 65% with diastolic dysfunction (termed as HFpEF, n = 10). Another group of ten healthy monkeys was used as the healthy control. All monkeys underwent a CMR study to measure global longitudinal strain (GLS), myocardial extracellular volume (ECV), and late gadolinium enhancement (LGE). In healthy controls and HFpEF group, quantitative perfusion imaging scans at rest and under dobutamine stress were performed and myocardial perfusion reserve (MPR) was subsequently obtained. No LGE was observed in any monkey. Monkeys with HF-like features were significantly older, compared to the healthy control group. There were significant differences among the three groups in ECV (20.79 ± 3.65% in healthy controls; 27.06 ± 3.37% in HFpEF group, and 31.11 ± 4.50% in HFrEFgroup, p < 0.001), as well as for stress perfusion (2.40 ± 0.34 ml/min/g in healthy controls vs. 1.28 ± 0.24 ml/min/g in HFpEF group, p < 0.01) and corresponding MPR (1.83 ± 0.3 vs. 1.35 ± 0.29, p < 0.01). After adjusting for age, ECV (p = 0.01) and MPR (p = 0.048) still showed significant differences among the three groups. Our preliminary imaging findings demonstrated cardiac dysfunction, elevated ECV, and/or reduced MPR in this HF-like NHP model. This pilot study laid the foundation for further mechanistic research and the development of a drug testing platform for distinct HF pathophysiology.

Anatomical and macromorphological data support a new species of Phyllanthus (Phyllanthaceae) from Southeastern Brazil

Phyllanthus megastylus, a new species endemic from Southeastern Brazil, is described here based on anatomical and macromorphological data. It is known so far from the state of Espírito Santo and is morphologically similar to P. itamarajuensis, but differs by its densely papillose branches, pink pistillate flowers, disk pistillate with undulate margin and punctiform stigmas. We provide illustrations, preliminary conservation status, phenological data and images taken in habitat. In addition, the new species it is compared anatomically with similar species and its systematic positioning is discussed.

Defining how Antibiotic Treatments shape Host Immunity

Abstract Although antibiotics are clinically crucial, little is known about how they impact a patient’s immune response to infection. We address that gap by investigating how macrophages respond to bacteria treated with different classes of antibiotics. We treated a broadly susceptible E. coli strain with 8 separate antibiotics, infected macrophages, and compared how much TNF the various antibiotic-treated bacteria elicited from macrophages. We found that bacteria treated with cidal antibiotics (that kill bacteria) elicited ~2–3 fold more TNF than macrophages infected with equivalent amounts of bacteria treated with bacteriostatic (growth limiting) antibiotics. A panel of 12 clinical isolates from patients (4 each of E.coli, Enterobacter and Klebsiella) showed a similar pattern of antibiotic class-dependent inflammatory cytokine output. We then evaluated an in vivo IP injection model with antibiotic pre-treated bacteria, heat-killed bacteria, or vehicle alone. At two hr post infection, we saw ~35–200% increases in serum levels of pro-inflammatory cytokines induced by cidal-treated bacteria compared to static-treated bacteria. Consistent with prior data, both the vehicle and the killed bacteria elicited no inflammatory cytokines. Preliminary imaging data suggest that treatment with the cidal drugs causes most of the dead bacteria to form large aggregates, while treatment with the static drugs does not. We now aim to clarify the role of these aggregates in driving this inflammatory outcome. This may identify additional patterns of immune responses to antibiotic treated bacteria that could guide the development of improved antimicrobial treatment strategies. This work is supported by the Intramural Research Program of NIAID, NIH. Supported by Intramural Research Program of NIAID, NIH.

Imaging blood-brain barrier dysfunction: A state-of-the-art review from a clinical perspective.

The blood-brain barrier (BBB) consists of specialized cells that tightly regulate the in- and outflow of molecules from the blood to brain parenchyma, protecting the brain's microenvironment. If one of the BBB components starts to fail, its dysfunction can lead to a cascade of neuroinflammatory events leading to neuronal dysfunction and degeneration. Preliminary imaging findings suggest that BBB dysfunction could serve as an early diagnostic and prognostic biomarker for a number of neurological diseases. This review aims to provide clinicians with an overview of the emerging field of BBB imaging in humans by answering three key questions: (1. Disease) In which diseases could BBB imaging be useful? (2. Device) What are currently available imaging methods for evaluating BBB integrity? And (3. Distribution) what is the potential of BBB imaging in different environments, particularly in resource limited settings? We conclude that further advances are needed, such as the validation, standardization and implementation of readily available, low-cost and non-contrast BBB imaging techniques, for BBB imaging to be a useful clinical biomarker in both resource-limited and well-resourced settings.

Electroacupuncture and manual acupuncture at LR3 and ST36 have attenuating effects on hypertension and subsequent cognitive dysfunction in spontaneously hypertensive rats: A preliminary resting-state functional magnetic resonance imaging study.

Chronic hypertension may have a contributory role toward cognitive impairment. Acupuncture exerts protective effects on cognitive functions while controlling the blood pressure. However, the neural mechanism underlying the dual attenuating effect of acupuncture remains unclear. In this study, we investigated the effects of electroacupuncture (EA) and manual acupuncture (MA) on the functional activity of the brain regions of spontaneously hypertensive rats (SHRs) by through resting-state functional magnetic resonance imaging (rs-fMRI). We also evaluated the differences in these functional activities between the EA and MA groups. We randomly assigned 30 SHRs into the EA, MA, and model (SHR) groups. Wistar Kyoto rats (n = 10) were used as normal control (WKY). The interventions were administered once every alternate day for 12 weeks. The systolic blood pressure of all rats was recorded every 2 weeks until the end of the intervention. After the intervention, rs-fMRI scanning was performed to access the whole brain data of rats randomly selected from each group evenly. The amplitude of low frequency fluctuation (ALFF) analysis, regional homogeneity (ReHo) analysis, and functional connectivity (FC) analysis were also conducted. The Morris water maze (MWM) test was conducted to evaluate the learning and memory of the rats. Hematoxylin-eosin staining and Nissl staining were performed to observe histopathological changes in the key brain regions. We demonstrated that, when compared with the SHR group, the EA and MA groups had significantly lower blood pressure and better performance for behavioral test indices, and that the effect of EA was better than that of MA. ALFF and ReHo analyses revealed enhancement of the neuronal activity of some functionally impaired brain areas in the EA and MA groups. The main callback brain regions included the hypothalamus, entorhinal cortex, brain stem, prelimbic cortex, cingulate cortex, corpus callosum, and cerebellum. The FC analysis demonstrated that EA and MA enhanced the functional connectivity between the seeds and brain regions such as the brain stem, entorhinal cortex, hippocampus, prelimbic cortex, and cerebellum. The pathological test of the entorhinal cortex also verified the protective effect of acupuncture on the neuronal functional activity. Our findings suggested that EA and MA exhibited attenuating effects on hypertension and cognitive dysfunction by enhancing the functional activities in the corresponding brain regions. Moreover, EA activated more callback brain regions and functional connectivity than MA, which may explain why the effect of EA was better than that of MA.

A spectroscopic and imaging gamma-detector prototype towards dose monitoring in BNCT

We report the performances of a compact gamma-ray detection prototype, based on a 2” LaBr3 scintillator crystal coupled to a matrix of 64 SiPMs, designed as a single unit for a future SPECT system for dose monitoring in BNCT. The aim of the module is to detect the 478 keV gamma rays emitted by the boron neutron capture reactions, in order to map the 10B distribution in the patient. The spectroscopic capabilities of the module have been validated by irradiating borated vials with thermal neutrons fluxes in the order of 1 × 105 n/cm2/s. The good energy resolution of the detector (2.7% at 662 keV) has allowed to resolve the boron neutron capture photopeak, achieving excellent linear correlation between the number of detected events at 478 keV and the boron concentration in the vials irradiated. Preliminary imaging results based on a Convolutional Neural Network and obtained by irradiating a 5 cm × 5 cm × 2 cm square crystal with a 1 mm collimated 137Cs source (662 keV) are also reported.

Multimodule Deep Learning Scheme for Elastic Wave Inversion of Inhomogeneous Objects With High Contrasts

In elastic wave inverse scattering problems, the material-property reconstruction, e.g. distributions of mass density, compressional wave speed, and shear wave speed from a limited set of measurement data, has attracted considerable research interest. However, simultaneous inversion of multiple parameters endures high computation costs, and reconstructed compressional and shear speeds may become unrealistic if no physical constraint is imposed. Meanwhile, because large objects with high contrasts over the background medium tend to induce high nonlinearity during the inversion process, it is difficult to obtain high-quality high-contrast material properties. To overcome such difficulties, we have developed a multi-module deep learning scheme with physical constraint for multi-parameter elastic wave inversion of high-contrast objects in inhomogeneous media. This scheme consists of (1) a preliminary imaging module (PIM), in which a deep residual network (ResNet) is employed to convert the scattered field data into the preliminary inversion images, (2) an image-enhancement module (IEM), in which a U-Net is employed to further enhance the image quality, and (3) a convolutional neural network (CNN) that is employed as the physical constraint module (PCM) to allow elastic wave parameters to satisfy actual physical constraint. Numerical examples have demonstrated that the proposed scheme not only accurately achieves multi-parameter elastic wave inversion, but also has good generalizability. Finally, the scheme can be applied to complex objects with high contrasts in both noise-free and noisy environments.

Association of circumferential aneurysm wall enhancement with recurrence after coiling of unruptured intracranial aneurysms: a preliminary vessel wall imaging study.

Recent histopathological studies of unruptured intracranial aneurysms (UIAs) have confirmed that aneurysm wall enhancement (AWE) on MR vessel wall imaging (VWI) is related to wall degeneration with in vivo inflammatory cell infiltration. Therefore, pretreatment aneurysm wall status on VWI may be associated with recurrence after endovascular treatment. VWI with gadolinium was performed on 67 consecutive saccular UIAs before endovascular treatment between April 2017 and June 2021. The mean (range) follow-up period after treatment was 24.4 (6-54) months. AWE patterns were classified as circumferential AWE (CAWE), focal AWE (FAWE), and negative AWE (NAWE). The authors retrospectively investigated the relationship between aneurysm recurrence and AWE patterns, as well as conventional risk factors. Sixty-seven patients with 67 saccular UIAs were eligible for the present study. AWE patterns were as follows: 10 CAWE (14.9%), 20 FAWE (29.9%), and 37 NAWE (55.2%). Follow-up MRA detected aneurysm recurrence in 18 of 69 cases (26.1%). Univariate analysis identified maximum diameter (mean ± SD 5.8 ± 2.2 mm in patients with stable aneurysms vs 7.7 ± 3.8 mm in those with unstable aneurysms, p = 0.02), aspect ratio (1.4 ± 0.5 vs 1.1 ± 0.4, p < 0.01), aneurysm location in posterior circulation (4.1% vs 27.8%, p < 0.01), volume embolization ratio (29.6% ± 7.8% vs 25.2% ± 6.1%, p = 0.02), and AWE pattern (p = 0.04) as significant predictive factors of recurrence. Among the 3 AWE patterns, CAWE was significantly more frequent in the unstable group, but no significant differences in stability of the treated aneurysms were observed with the FAWE and NAWE patterns. In multivariate logistic regression analysis, CAWE pattern (OR 14.2, 95% CI 1.8-110.8, p = 0.01) and volume embolization ratio ≥ 25% (OR 8.6, 95% CI 2.1-34.3, p < 0.01) remained as significant factors associated with aneurysm stability after coiling. VWI before coiling provides novel insights into the stability of treated aneurysms. Aneurysms with the CAWE pattern on VWI before coiling may be less stable after treatment.

Automated production of [11C]butyrate for keto body PET imaging

The report describes an updated, fully automated method for the production of [11C]butyrate, validated for use in clinical studies. A commercially available GE Tracerlab FXM synthesis module was reconfigured to allow for air-free introduction of n-propyl magnesium chloride and to incorporate Sep-Pak cartridges to simplify and shorten the purification process, as compared to purifying the product using traditional HPLC. The method takes 20 min from end-of-bombardment and reliably produces injectable doses of [11C]butyrate (8029 ± 1628 MBq (217 ± 44 mCi), 14 % radiochemical yield based on [11C]CO2, non-decay corrected) in high radiochemical purity (>97 %), n = 3. With radiotracer in hand, PET scans of rats confirmed uptake of the radiopharmaceutical in the brain. Rat biodistribution data was obtained and used in conjunction with OLINDA software to determine an estimated human total body effective dose of 3.20 × 10−3 mSv/MBq (1.19 × 10−2 rem/mCi), along with preliminary rodent PET imaging that confirmed brain uptake. Lastly, our first human [11C]butyrate PET studies using a dynamic bolus injection technique (n = 5), with a graphical Logan analysis using a white matter reference region, confirmed good radiotracer uptake in the brain and with relatively more prominent uptake in the cerebellar hemispheres, vermis, cingulum cortex and the thalami.

Experimental Evaluation of a 3-D CZT Imaging Spectrometer for Potential Use in Compton-Enhanced PET Imaging.

We constructed a prototype positron emission tomography (PET) system and experimentally evaluated large-volume 3-D cadmium zinc telluride (CZT) detectors for potential use in Compton-enhanced PET imaging. The CZT spectrometer offers sub-0.5-mm spatial resolution, an ultrahigh energy resolution (~1% @ 511 keV), and the capability of detecting multiple gamma-ray interactions that simultaneously occurred. The system consists of four CZT detector panels with a detection area of around 4.4 cm × 4.4 cm. The distance between the front surfaces of the two opposite CZT detector panels is ~80 mm. This system allows us to detect coincident annihilation photons and Compton interactions inside the detectors and then, exploit Compton kinematics to predict the first Compton interaction site and reject chance coincidences. We have developed a numerical integration technique to model the near-field Compton response that incorporates Doppler broadening, detector's finite resolutions, and the distance between the first and second interactions. This method was used to effectively reject random and scattered coincidence events. In the preliminary imaging studies, we have used point sources, line sources, a custom-designed resolution phantom, and a commercial image quality (IQ) phantom to demonstrate an imaging resolution of approximately 0.75 mm in PET images, and Compton-based enhancement.