Comparative studies of the sensitivities of sparse and full geometries of Total-Body PET scanners built from crystals and plastic scintillators

BACKGROUND

Alongside the benefits of Total-Body imaging modalities, such as higher sensitivity, single-bed position, low dose imaging, etc., their final construction cost prevents worldwide utilization. The main aim of this study is to present a simulation-based comparison of the sensitivities of existing and currently developed tomographs to introduce a cost-efficient solution for constructing a Total-Body PET scanner based on plastic scintillators.

METHODS

For the case of this study, eight tomographs based on the uEXPLORER configuration with different scintillator materials (BGO, LYSO), axial field-of-view (97.4 cm and 194.8 cm), and detector configurations (full and sparse) were simulated. In addition, 8 J-PET scanners with different configurations, such as various axial field-of-view (200 cm and 250 cm), different cross sections of plastic scintillator, and multiple numbers of plastic scintillator layers (2, 3, and 4), based on J-PET technology have been simulated by GATE software. Furthermore, Siemens' Biograph Vision has been simulated to compare the results with standard PET scans. Two types of simulations have been performed. The first one with a centrally located source with a diameter of 1 mm and a length of 250 cm, and the second one with the same source inside a water-filled cylindrical phantom with a diameter of 20 cm and a length of 183 cm.

RESULTS

With regards to sensitivity, among all the proposed scanners, the ones constructed with BGO crystals give the best performance ([Formula: see text] 350 cps/kBq at the center). The utilization of sparse geometry or LYSO crystals significantly lowers the achievable sensitivity of such systems. The J-PET design gives a similar sensitivity to the sparse LYSO crystal-based detectors while having full detector coverage over the body. Moreover, it provides uniform sensitivity over the body with additional gain on its sides and provides the possibility for high-quality brain imaging.

CONCLUSION

Taking into account not only the sensitivity but also the price of Total-Body PET tomographs, which till now was one of the main obstacles in their widespread clinical availability, the J-PET tomography system based on plastic scintillators could be a cost-efficient alternative for Total-Body PET scanners.

Efficiency determination of J-PET: first plastic scintillators-based PET scanner

BACKGROUND

The Jagiellonian Positron Emission Tomograph is the 3-layer prototype of the first scanner based on plastic scintillators, consisting of 192 half-metre-long strips with readouts at both ends. Compared to crystal-based detectors, plastic scintillators are several times cheaper and could be considered as a more economical alternative to crystal scintillators in future PETs. JPET is also a first multi-photon PET prototype. For the development of multi-photon detection, with photon characterized by the continuous energy spectrum, it is important to estimate the efficiency of J-PET as a function of energy deposition. The aim of this work is to determine the registration efficiency of the J-PET tomograph as a function of energy deposition by incident photons and the intrinsic efficiency of the J-PET scanner in detecting photons of different incident energies. In this study, 3-hit events are investigated, where 2-hits are caused by 511 keV photons emitted in [Formula: see text] annihilations, while the third hit is caused by one of the scattered photons. The scattered photon is used to accurately measure the scattering angle and thus the energy deposition. Two hits by a primary and a scattered photon are sufficient to calculate the scattering angle of a photon, while the third hit ensures the precise labeling of the 511 keV photons.

RESULTS

By comparing experimental and simulated energy distribution spectra, the registration efficiency of the J-PET scanner was determined in the energy deposition range of 70-270 keV, where it varies between 20 and 100[Formula: see text]. In addition, the intrinsic efficiency of the J-PET was also determined as a function of the energy of the incident photons.

CONCLUSION

A method for determining registration efficiency as a function of energy deposition and intrinsic efficiency as a function of incident photon energy of the J-PET scanner was demonstrated. This study is crucial for evaluating the performance of the scanner based on plastic scintillators and its applications as a standard and multi-photon PET systems. The method may be also used in the calibration of Compton-cameras developed for the ion-beam therapy monitoring and simultaneous multi-radionuclide imaging in nuclear medicine.

0905 Obstructive Sleep Apnea In Pediatric Patients With Early Onset Scoliosis

Introduction

Early onset scoliosis (EOS), defined as curvature of the spine >10 degrees with onset before 10 years of age, is associated with increased rates of restrictive lung disease, pain, and other factors that increase risk of poor sleep. We compared the polysomnographic findings of children with EOS to those of children without EOS. We postulated that children with EOS would have a higher rate of OSA than patients without EOS, and differences in sleep stage distribution, arousals, and limb movements.

Methods

Single-center retrospective chart review performed on 58 subjects with EOS (ages 1-17yr) who underwent PSG from 2003-2019; comparison group of 58 subjects without scoliosis who underwent diagnostic PSG was chosen consecutively (ages 1-18yr). Polysomnographic parameters compared include: sleep stage distribution, arousal index (AI), obstructive/central AHI, mean and nadir oxygen saturation in REM/NREM, and periodic leg movement index. All p-values were adjusted for multiple comparisons.

Results

There was no difference in age or sex distribution between the two groups, though subjects with EOS had lower BMI than those without EOS (median 16.3 (IQR 14.7-19.3) vs. 17.5 (IQR 16.2-21.6), p=0.019). 84% of subjects with EOS had OSA, compared to 66% without EOS. Subjects with EOS and OSA had higher obstructive AHI than the OSA group without EOS, and longer duration of hypopneas. There was no significant difference in sleep stage distribution, AI, or PLMI.

Conclusion

Of pediatric patients referred for polysomnography at our institution, those with EOS had a higher rate of OSA, more severe OSA where present, and lower BMI. We advocate for routine polysomnography for children with EOS due to the high risk of OSA amongst those tested, and further study to better understand the pathophysiology of sleep disordered breathing in this population.

Support

This project is supported by the Health Resources and Services Administration (HRSA) of the US Department of Health and Human Services under grant #T72MC00007/University of Washington Pediatric Pulmonary Center/PI: Redding. The content and conclusions are those of the author and should not be construed as the official position or policy of, nor should any endorsements be inferred by HRSA, HHS or the U.S. Government.

Voice pathology classification based on High-Speed Videoendoscopy

This work presents a method for automatical and objective classification of patients with healthy and pathological vocal fold vibration impairments using High-Speed Videoendoscopy of the larynx. We used an image segmentation and extraction of a novel set of numerical parameters describing the spatio-temporal dynamics of vocal folds to classification according to the normal and pathological cases and achieved 73,3% cross-validation classification accuracy. This approach is promising to develop an automatic diagnosis tool of voice disorders.

Drug development from natural products: exploiting synergistic effects

Drug development in phytomedicine has been focused in the past on the discovery and analysis of new structures from natural products. The search aimed at the determination of the single "active principle" in plants, based on the assumption that a plant has one or a few ingredients which determine its therapeutic effects. But traditional systems of medicines like Ayurveda, traditional Chinese medicine or the European phytotherapy generally assume that a synergy of all ingredients of the plants will bring about the maximum of therapeutic efficacy. This approach has for long been impossible to investigate since adequate methods to standardize complex plant mixtures as well as to rationalize complex mode of actions were lacking. The introduction of high throughput technologies provides the opportunity to determine profiles of plants and to systematically explore the mode of action of combinatory drug regimes. The present review highlights the concept of synergy and gives examples of synergistic effects of plant constituents. It elaborates on how the high throughput technologies can be used in drug development from natural products with the aim of creating evidence-based plant medications in prevention and treatment of different diseases in the form of new single treatments or new combinatory drug regimes while exploiting synergy-effects.

New perspectives for synergy research with the "omic"-technologies

Synergistic effects, understood as true overadditive effects, are often observed in experimental and clinical studies using phytopharmaceuticals. The introduction of the "omic"-technologies is now opening new perspectives in rationalizing these effects and making use of them in the development of a new generation of phytopharmaceuticals. This review describes possible mechanism of synergistic actions of herbal drugs by mono- and multitargeting and by the activation of signal cascades. It examines the possibilities of the standardization of single and multi component plant extracts and the prediction and assessment of the toxicity and safety of plant extracts with the support of the "omic"-technologies. It further discusses the use of phytopharmaceuticals in the context of an "individualized medicine". It makes proposals how to use the "omic"-technologies to rationalize and develop combination therapies of phytopharmaceuticals and synthetic drugs to minimize adverse reactions (ARs) or improve the therapeutic efficacy. Examples of clinical studies are given which explore already the potential of such co-medications. Modern medical therapy has acknowledged for quite some time the usefulness of combination therapies in the treatment of multifactorial diseases like cancer, cardiovascular or rheumatic diseases. The term "synergy" is rarely used in this context, the combinatory mechanisms of actions seldom completely understood and the potentially occurring adverse reactions feared. A systematic exploitation of synergy effects of phytomedical interventions alone or in combination with synthetic drugs should lead in a long term perspective to the discovery and development of more rational evidence-based interventions in the prevention and therapy of multifactorial diseases and should thereby enrich modern pharmacotherapy.

Application of the "-Omic-" technologies in phytomedicine

The proof of efficacy of phytopreparations and the determination of their mode of action are permanent challenges for an evidence-based phytotherapy. The technology platform of genomics, proteomics and metabolomics ("-omic-" technologies) are high-throughput technologies. They increase substantially the number of proteins/genes that can be detected simultaneously and have the potential to relate complex mixtures to complex effects in the form of gene/protein expression profiles. Provided that phytopreparation-specific signatures in the form of gene/protein expression profiles can be developed, these technologies will be useful for the chemical and pharmacological standardization and the proof of the toxicological potential of a plant extract. Over a long-term perspective they may economize the proof of efficacy, the determination of the mode of action of phytomedicines and allow to investigate herbal extracts without prominent active principle(s). The application of this genomics revealed already that gene expression profiles induced by single drugs and the ones induced by the combination of the same drugs can be entirely different. These results make the information of the mode of action of isolated "active principles/lead substances" of phytopreparations questionable. The application of the "-omic-" technologies may lead to a change of paradigms towards the application of complex mixtures in medicine and open the new field of phytogenomics, -proteomics and -metabolomics.

Regulation of trehalose metabolism in Saccharomyces cerevisiae mutants during temperature shifts

Temperature shifts from 23 degrees C to 36 degrees C resulted in trehalose accumulation in Saccharomyces independently of genetic lesions in the cAMP-protein kinase cascade. In parallel, trehalose 6-phosphate synthase activity increased about 3-fold in all strains; the increase could be inhibited by cycloheximide, suggesting that protein synthesis was required. Heat shock treatment after the temperature shift led to a drastic increase in trehalose activity, and deactivation of the biosynthetic enzyme with a consequent drop in trehalose. Up to now no definite correlation between acquisition of thermotolerance and trehalose accumulation has been made.

The influence of oestrogen and oestrogen metabolites on the sensitivity of the isolated rabbit aorta to catecholamines

In the present study the influence of oestradiol, catechol oestrogens, and O-methylated oestrogens was determined on the contractile responses of the isolated rabbit aorta to (-)-adrenaline. Oestradiol (40 mumol/l), 2-hydroxyoestradiol (2OHE2) (20 mumol/l), and 2-methoxyoestradiol (2MeOE2) (20 mumol/l) all sensitized the rabbit aorta to contractile responses to (-)-adrenaline. Similarly, the 2-hydroxy and 2-methoxy derivatives of oestrone and oestriol also sensitized the aorta to (-)-adrenaline-induced contractions. The largest degree of sensitization was seen in the presence of the 2-methoxysteroids. Oestradiol and 2OHE2 did not increase responses of the aorta to (-)-noradrenaline, while slight potentiation of contraction was seen in the presence of 2MeOE3. The potentiating effect of 2OHE2 on contractile responses to (-)-adrenaline was abolished by prior treatment of the tissue with a COMT inhibitor (U-0521, 55 mumol/l). Conversely, pretreatment of the tissue with 2OHE2 prevented the augmented aortic contraction to (-)-adrenaline usually seen after inhibition of COMT. The non-additive nature of the sensitization seen after combined treatment with 2OHE2 and U-0521 was qualitatively similar to that seen following combined exposure to maximally effective concentrations of U-0521 and an inhibitor of extraneuronal uptake (hydrocortisone 100 mumol/l). Oestradiol and 2MeOE2 reduced the formation of both the 3H-O-methylated, 3H-deaminated and the 3H-O-methylated deaminated metabolites of 3H-(-)-adrenaline (0.15 mumol/l) during exposure of the aorta to the tritiated catecholamine.(ABSTRACT TRUNCATED AT 250 WORDS)