Dopamine Transporter SPECT with 12-Minute Scan Duration Using Multiple-Pinhole Collimators.

This study evaluated the potential to reduce the scan duration in dopamine transporter (DAT) SPECT when using a second-generation multiple-pinhole (MPH) collimator designed for brain SPECT with improved count sensitivity and improved spatial resolution compared with parallel-hole and fanbeam collimators. Methods: The retrospective study included 640 consecutive clinical DAT SPECT studies that had been acquired in list mode with a triple-head SPECT system with MPH collimators and a 30-min net scan duration after injection of 181 ± 10 MBq of [123I]FP-CIT. Raw data corresponding to scan durations of 20, 15, 12, 8, 6, and 4 min were obtained by restricting the events to a proportionally reduced time interval of the list-mode data for each projection angle. SPECT images were reconstructed iteratively with the same parameter settings irrespective of scan duration. The resulting 5,120 SPECT images were assessed for a neurodegeneration-typical reduction in striatal signal by visual assessment, conventional specific binding ratio analysis, and a deep convolutional neural network trained on 30-min scans. Results: Regarding visual interpretation, image quality was considered diagnostic for all 640 patients down to a 12-min scan duration. The proportion of discrepant visual interpretations between 30 and 12 min (1.2%) was not larger than the proportion of discrepant visual interpretations between 2 reading sessions of the same reader at a 30-min scan duration (1.5%). Agreement with the putamen specific binding ratio from the 30-min images was better than expected for 5% test-retest variability down to a 10-min scan duration. A relevant change in convolutional neural network-based automatic classification was observed at a 6-min scan duration or less. Conclusion: The triple-head SPECT system with MPH collimators allows reliable DAT SPECT after administration of about 180 MBq of [123I]FP-CIT with a 12-min scan duration.

Performance evaluation of a novel multi-pinhole collimator on triple-NaI-detector SPECT/CT for dedicated myocardial imaging.

BACKGROUND: In this study we evaluated the imaging capabilities of a novel Multi-pinhole collimator (MPH-Cardiac) specially designed for nuclear cardiology imaging on a Triple-NaI-detector based SPECT/CT system. METHODS: 99mTc point source measurements covering the field of view (FOV) were used to determine tomographic sensitivity (TSpointsource) and spatial resolution. Organ-size tomographic sensitivity (TSorgan) was measured with a left ventricle (LV) phantom filled with typical myocardial activity of a patient scan. Reconstructed image uniformity was measured with a 140 mm diameter uniform cylinder phantom. Using the LV phantom once filled with 99mTc and after with 123I, Contrast-to-noise ratio (CNR) was measured on the reconstructed images by ROI analysis on the myocardium activity and on the LV cavity. Furthermore, a polar map analysis was performed determining Spill-Over-Ratio in water (SORwater) and image noise. The results were compared with that of a dual-head parallel-hole low energy high resolution (LEHR) collimator system. A patient with suspected coronary artery disease (CAD) was scanned on the LEHR system using local protocol of 16 min total acquisition time, followed by a 4-min MPH-Cardiac scan. RESULTS: Peak TSpointsource was found to be 1013 cps/MBq in the axial center of the FOV while it was decreasing toward the radial edges. TSorgan in the CFOV was found to be 134 cps/MBq and 700 cps/MBq for the LEHR and MPH-Cardiac, respectively. Average spatial resolution throughout the FOV was 4.38 mm FWHM for the MPH-Cardiac collimator. Reconstructed image uniformity values were found to be 0.292% versus 0.214% for the LEHR and MPH-Cardiac measurements, respectively. CNR was found to be higher in case of MPH-Cardiac than for LEHR in case of 99mTc (15.5 vs. 11.7) as well as for 123I (13.5 vs. 8.3). SORwater values were found to be 28.83% and 21.1% for the 99mTc measurements, and 31.44% and 24.33% for the 123I measurements for LEHR and MPH-Cardiac, respectively. Pixel noise of the 99mTc polar maps resulted in values of 0.38% and 0.24% and of the 123I polar maps 0.62% and 0.21% for LEHR and MPH-Cardiac, respectively. Visually interpreting the patient scan images, MPH-Cardiac resulted in better image contrast compared to the LEHR technique with four times shorter scan duration. CONCLUSIONS: The significant image quality improvement achieved with dedicated MPH-Cardiac collimator on triple head SPECT/CT system paves the way for short acquisition and low-dose cardiovascular SPECT applications.

Multiple-pinhole collimators improve intra- and between-rater agreement and the certainty of the visual interpretation in dopamine transporter SPECT.

BACKGROUND: Multiple-pinhole (MPH) collimators improve the resolution-sensitivity trade-off compared to parallel-hole collimators. This study evaluated the impact of MPH collimators on intra- and between-rater agreement, and on the certainty of visual interpretation in dopamine transporter (DAT)-SPECT. METHODS: The study included 71 patients (62.1 ± 12.7 y). Two SPECT acquisitions were performed in randomized order after a single injection of 182 ± 9 MBq 123I-FP-CIT, one with MPH and one with low-energy-high-resolution-high-sensitivity (LEHRHS) collimators. MPH projections were reconstructed with an iterative 3d Monte Carlo algorithm. LEHRHS projections were reconstructed with filtered backprojection (FBP) or with ordered-subsets expectation-maximization and resolution recovery (OSEM). Images were visually evaluated twice by three independent raters with respect to presence/absence of Parkinson-typical reduction of striatal 123I-FP-CIT uptake using a Likert 6-score (- 3 = clearly normal, …, 3 = clearly reduced). In case of intra-rater discrepancy, an intra-rater consensus was obtained. Intra- and between-rater agreement with respect to the Likert score (6-score and dichotomized score) was characterized by Cohen's kappa. RESULTS: Intra-rater kappa of visual scoring of MPH/LEHRHS-OSEM/LEHRHS-FBP images was 0.84 ± 0.12/0.73 ± 0.06/0.73 ± 0.08 (6-score, mean of three raters) and 1.00 ± 0.00/0.96 ± 0.04/0.97 ± 0.03 (dichotomized score). Between-rater kappa of visual scoring (intra-rater consensus) of MPH/LEHRHS-OSEM/LEHRHS-FBP images was 0.70 ± 0.06/0.63 ± 0.08/0.48 ± 0.05 (6-score, mean of three pairs of raters) and 1.00 ± 0.00/0.92 ± 0.04/0.90 ± 0.06 (dichotomized score). There was a decrease of (negative) Likert scores in normal DAT-SPECT by 0.87 ± 0.18 points from the LEHRHS-OSEM to the MPH setting. The (positive) Likert scores of reduced DAT-SPECT did not change on average. CONCLUSIONS: MPH collimators improve intra- and between-rater agreement as well as the certainty of the visual interpretation of DAT-SPECT.

Initial clinical experience with dedicated multi-pinhole (MPH) collimator for 99mTc-HMPAO brain perfusion SPECT.

OBJECTIVE: Dedicated multi-pinhole (MPH) collimators have been successfully tested in selected clinical investigations. The aim of our work was to report initial experiences with an MPH collimator set designed for brain perfusion single photon emission tomography (SPECT). SUBJECTS AND METHODS: Ten patients underwent sequential technetium-99m-hexamethylpropyleneamineoxime (99mTc-HMPAO) SPECT with a dual-head SPECT camera equipped with conventional low-energy parallel hole collimators (LEHR), and with a triple-head system equipped with MPH collimators. Low-energy parallel hole collimators data were reconstructed by filtered back projection (FBP), ordered subset expectation maximization (OSEM), software for tomographic image reconstruction (STIR). In addition, both the parallel hole data and MPH data were reconstructed by Tera-TomoTM 3D iterative reconstruction denoted LEHR_TT3D and MPH_TT3D, respectively. Five medical experts visually compared the reconstructed images of the five data sets and defined a ranking sequence from the lowest (1) to the highest (5) image quality. Results were compared using the Friedman test. P values below 0.05 were considered significant. RESULTS: Low-energy parallel hole collimators acquisition resulted in 5 million, while MPH acquisition in 13 million total counts with 30 and 34 minutes of acquisition time, respectively. Mean rank coefficients of the reconstruction methods were 1.96±0.52, 2.66±0.46, 2.86±0.60, 3.62±0.55, 3.9±0.68 for FBP, STIR, LEHR_TT3D, LEHR_OSEM, MPH_TT3D respectively. The differences between MPH_TT3D-FBP (P<0.01); MPH_TT3D-STIR (P<0.05); LEHR_OSEM-FBP (P<0.01) were significant. CONCLUSION: Image quality provided by MPH collimator is comparable to that provided by conventional LEHR imaging. Higher sensitivity has the potential to shorten acquisition time or to reduce the amount of administered activity.

Unusual perfusion patterns on perfusion-only SPECT/CT scans in COVID-19 patients.

PURPOSE: We aimed at examining both the incidence and extent of different lung perfusion abnormalities as well as the relationship between them on Tc-99m macroaggregated albumin (MAA) perfusion-only SPECT/CT scans in COVID-19 patients. METHODS: Ninety-one patients (71.4 ± 13.9 years; range: 29-98 years, median age: 74 years; 45 female and 46 male) with confirmed SARS-CoV-2 virus infection were included in this retrospective study. After performing perfusion-only Tc-99m MAA SPECT/CT scans, visual, semi-quantitative assessment of the subsequent perfusion abnormalities was carried out: mismatch lesions (MM; activity defects on SPECT images identical to apparently healthy parenchyma on CT images), matched lesions (MA; activity defects with corresponding parenchymal lesions on CT scans), and reverse mismatch lesions (RM; parenchymal lesions with preserved or increased tracer uptake). Lesion-based and patient-based analysis were performed to evaluate the extent, severity, and incidence of each perfusion abnormality. Statistical tests were applied to investigate the association between the experienced perfusion impairments. RESULTS: Moderately severe parenchymal lesions were detected in 87 (95.6%) patients. Although, 50 (54.95%) patients were depicted to have MM lesions, the whole patient cohort was mildly affected by this abnormality. MA lesions of average moderate severity were seen in most of the patients (89.01%). In 65 (71.43%) patients RM lesions were found with mild severity on average. Positive association was detected between total CT score and total RM score and between total CT score and total MA score. Significantly higher total CT scores were experienced in the subgroup, where RM lesions were present. CONCLUSIONS: Heterogeneous perfusion abnormalities were found in most of COVID-19 patients: parenchymal lesions with normal, decreased or increased perfusion and perfusion defects in healthy lung areas. These phenomena may be explained by the failure of the hypoxic pulmonary vasoconstriction mechanism and presence of pulmonary thrombosis and embolism.

3D printed anthropomorphic left ventricular myocardial phantom for nuclear medicine imaging applications.

BACKGROUND: Anthropomorphic torso phantoms, including a cardiac insert, are frequently used to investigate the imaging performance of SPECT and PET systems. These phantom solutions are generally featuring a simple anatomical representation of the heart. 3D printing technology paves the way to create cardiac phantoms with more complex volume definition. This study aimed to describe how a fillable left ventricular myocardium (LVm) phantom can be manufactured using geometry extracted from a patient image. METHODS: The LVm of a healthy subject was segmented from 18F-FDG attenuation corrected PET image set. Two types of phantoms were created and 3D printed using polyethylene terephthalate glycol (PETG) material: one representing the original healthy LVm, and the other mimicking myocardium with a perfusion defect. The accuracy of the LVm phantom production was investigated by high-resolution CT scanning of 3 identical replicas. 99mTc SPECT acquisitions using local cardiac protocol were performed, without additional scattering media ("in air" measurements) for both phantom types. Furthermore, the healthy LVm phantom was inserted in the commercially available DataSpectrum Anthropomorphic Torso Phantom ("in torso" measurement) and measured with hot background and hot liver insert. RESULTS: Phantoms were easy to fill without any air-bubbles or leakage, were found to be reproducible and fully compatible with the torso phantom. Seventeen segments polar map analysis of the "in air" measurements revealed that a significant deficit in the distribution appeared where it was expected. 59% of polar map segments had less than 5% deviation for the "in torso" and "in air" measurement comparison. Excluding the deficit area, neither comparison had more than a 12.4% deviation. All the three polar maps showed similar apex and apical region values for all configurations. CONCLUSIONS: Fillable anthropomorphic 3D printed phantom of LVm can be produced with high precision and reproducibility. The 3D printed LVm phantoms were found to be suitable for SPECT image quality tests during different imaging scenarios. The flexibility of the 3D printing process presented in this study provides scalable and anthropomorphic image quality phantoms in nuclear cardiology imaging.

Interaction of Aqueous Bovine Serum Albumin with Silica Aerogel Microparticles: Sorption Induced Aggregation.

Mesoporous silica aerogels have a wide range of potential applications in biotechnology, the food industry, pharmacy and medicine. Understanding the nature of the interactions of biomolecules with these porous nanostructured materials is essential for achieving optimum performance in the targeted applications. In this study, the well-characterized bovine serum albumin (BSA) was chosen as a model protein to probe protein-aerogel interactions in the solution phase. Aqueous BSA was mixed with suspended silica aerogel microparticles, and the colloid system was monitored on-line by UV-vis spectrophotometry and turbidimetry. The global mathematical analysis of the time-resolved data reveals that the fast sorption of the protein on the aerogel microparticles follows a multistep binding mechanism. The extensive sorption of the protein eventually induces the aggregation of the covered aerogel due to the alteration of the electrical double layer of the particles. The interaction of BSA and silica aerogel is the strongest between pH = 4 and 5, because their native surface charges are the opposite in this pH range, as indicated by their respective zeta potentials.

DEM-Based Approach for the Modeling of Gelation and Its Application to Alginate.

The gelation of biopolymers is of great interest in the material science community and has gained increasing relevance in the past few decades, especially in the context of aerogels─lightweight open nanoporous materials. Understanding the underlying gel structure and influence of process parameters is of great importance to predict material properties such as mechanical strength. In order to improve understanding of the gelation mechanism in aqueous solution, this work presents a novel approach based on the discrete element method for the mesoscale for modeling gelation of hydrogels, similarly to an extremely coarse-grained molecular dynamics (MD) approach. For this, polymer chains are abstracted as dimer units connected by flexible bonds and interactions between units and with the environment, that is, diffusion in implicit water, are described. The model is based on Langevin dynamics and includes an implicit probabilistic ion model to capture the effects of ion availability during ion-mediated gelation. The model components are fully derived and parameterized using literature data and theoretical considerations based on a simplified representation of atomistic processes. The presented model enables investigations of the higher-scale network formation during gelation on the micrometer and millisecond scale, which are beyond classical modeling approaches such as MD. As a model system, calcium-mediated alginate gelation is investigated including the influence of ion concentration, polymer composition, polymer concentration, and molecular weight. The model is verified against numerous literature data as well as own experimental results for the corresponding Ca-alginate hydrogels using nitrogen porosimetry, NMR cryoporometry, and small-angle neutron scattering. The model reproduces both bundle size and pore size distribution in a reasonable agreement with the experiments. Overall, the modeling approach paves the way to physically motivated design of alginate gels.

Homocysteine-related alterations of 18F-FDG brain pattern in metabolic diseases.

Since hyperhomocysteinaemia (HHcys) is implicated as a risk factor for the development of neurodegeneration, and is associated with the development of metabolic diseases,we aimed at analysing the effect of homocysteine (Hcys) on regional fluorine-18-fluorodeoxyglucose (18F-FDG) brain metabolismin 51 controlled type 2 diabetic and in 48 non-DM obese participants. Plasma Hcys levels were measured by an immunoassay. Homocysteine-related 18F-FDG regional brain metabolism was evaluated applying 18F-FDG PET/CT using magnetic resonance imaging (MRI)-based brain template for statistical parametric mapping (SPM) analysis. Homocysteine-related decreased 18F-FDG uptake was shown in the right middle temporal gyrus in the whole population. Diabetics with Hcys above the reference limit expressed decreased glucose metabolismin the left calcarine cortex compared to the obese with HHcys. Regional metabolic alterations evoked on the basis of HHcys draw attention to the potential risk of neurodegeneration caused by metabolic disturbances.

Effect of grey-level discretization on texture feature on different weighted MRI images of diverse disease groups.

PURPOSE: Many studies of MRI radiomics do not include the discretization method used for the analyses, which might indicate that the discretization methods used are considered irrelevant. Our goals were to compare three frequently used discretization methods (lesion relative resampling (LRR), lesion absolute resampling (LAR) and absolute resampling (AR)) applied to the same data set, along with two different lesion segmentation approaches. METHODS: We analyzed the effects of altering bin widths or bin numbers for the three different sampling methods using 40 texture indices (TIs). The impact was evaluated on brain MRI studies obtained for 71 patients divided into three different disease groups: multiple sclerosis (MS, N = 22), ischemic stroke (IS, N = 22), cancer patients (N = 27). Two different MRI acquisition protocols were considered for all patients, a T2- and a post-contrast 3D T1-weighted MRI sequence. Elliptical and manually drawn VOIs were employed for both imaging series. Three different types of gray-level discretization methods were used: LRR, LAR and AR. Hypothesis tests were done among all diseased and control areas to compare the TI values in these areas. We also did correlation analyses between TI values and lesion volumes. RESULTS: In general, no significant differences were reported in the results when employing the AR and LAR discretization methods. It was found that employing 38 TIs introduced variation in the results when the number of bin parameters was altered, suggesting that both the degree and direction of monotonicity between each TI value and binning parameters were characteristic for each TI. Furthermore, while TIs were changing with altering binning values, no changes correlated to neither disease nor the MRI sequence. We found that most indices correlated weakly with the volume, while the correlation coefficients were independent of both diseases analyzed and MR contrast. Several cooccurrence-matrix based texture parameters show a definite higher correlation when employing the LRR discretization method However, with the best correlations obtained for the manually drawn VOI. Hypothesis tests among all disease and control areas (co-lateral hemisphere) revealed that the AR or LAR discretization techniques provide more suitable texture features than LRR. In addition, the manually drawn segmentation gave fewer significantly different TIs than the ellipsoid segmentations. In addition, the amount of TIs with significant differences was increasing with increasing the number of bins, or decreasing bin widths. CONCLUSION: Our findings indicate that the AR discretization method may offer the best texture analysis in MR image assessments. Employing too many bins or too large bin widths might reduce the selection of TIs that can be used for differential diagnosis. In general, more statistically different TIs were observed for elliptical segmentations when compared to the manually drawn VOIs. In the texture analysis of MR studies, studies and publications should report on all important parameters and methods related to data collection, corrections, normalization, discretization, and segmentation.

Q-Bot: automatic DICOM metadata monitoring for the next level of quality management in nuclear medicine.

BACKGROUND: Regular and precise inspection of the realization of the local nuclear medicine standard operation procedures (SOPs) is very complex and time-consuming, especially when large amount of patient data is obtained from a wide scale of different scan procedures on a daily basis. DICOM metadata comprise a complete set of data related to the patient and the imaging procedure, and consequently all information necessary to evaluate the compliance with the actual SOP. METHODS: Q-Bot, an automatic DICOM metadata monitoring tool which is capable to verify SOP conformities, was tested for 11 months at two nuclear medicine departments. Relevant parameters, such as patient ID, patient mass and height, injected activity, and uptake time, were investigated in the case of adult 18F-FDG whole-body PET/CT and 99mTc-MDP gamma camera bone scans on a daily basis. Q-Bot automatically inspected the actual SOP compliance of these relevant DICOM parameters. Q-Bot graphical user interface (GUI) provided a summary of the outliers in a table format to be investigated by a dedicated technologist. In addition, information related to the error handling was also collected for retrospective analysis of long-term tendencies. RESULTS: In total, 6702 PET/CT and 2502 gamma camera scans were inspected, from which 8581 were confirmed as valid patient study without errors. Discrepancies related to the lack of a parameter, not appropriate format, or improper scan procedures were found in 623 cases, and 156 out of these were corrected before the medical reading and reporting. SOP non-conformities explored with Q-Bot were found to be non-correctable in 467 cases. Systematic errors to our practice turned out to be the manual radiopharmaceutical injection, the allowance to use both SI and non-SI units, and the clear definition of decimal point symbol to use. CONCLUSION: The daily evaluation of Q-Bot results provided early detection of errors and consequently ensured the minimization of error propagation. Integration of a QM software that inspects protocol compliance at a nuclear medicine department provides significant support to detect non-conformities for technologists, and much higher confidence in image quality for physicians.

Mechanism of Hydration and Hydration Induced Structural Changes of Calcium Alginate Aerogel.

The most relevant properties of polysaccharide aerogels in practical applications are determined by their microstructures. Hydration has a dominant role in altering the microstructures of these hydrophilic porous materials. To understand the hydration induced structural changes of monolithic Ca-alginate aerogel, produced by drying fully cross-linked gels with supercritical CO2, the aerogel was gradually hydrated and characterized at different states of hydration by small-angle neutron scattering (SANS), liquid-state nuclear magnetic resonance (NMR) spectroscopy, and magic angle spinning (MAS) NMR spectroscopy. First, the incorporation of structural water and the formation of an extensive hydration sphere mobilize the Ca-alginate macromolecules and induce the rearrangement of the dry-state tertiary and quaternary structures. The primary fibrils of the original aerogel backbone form hydrated fibers and fascicles, resulting in the significant increase of pore size, the smoothing of the nanostructured surface, and the increase of the fractal dimension of the matrix. Because of the formation of these new superstructures in the hydrated backbone, the stiffness and the compressive strength of the aerogel significantly increase compared to its dry-state properties. Further elevation of the water content of the aerogel results in a critical hydration state. The Ca-alginate fibers of the backbone disintegrate into well-hydrated chains, which eventually form a quasi-homogeneous hydrogel-like network. Consequently, the porous structure collapses and the well-defined solid backbone ceases to exist. Even in this hydrogel-like state, the macroscopic integrity of the Ca-alginate monolith is intact. The postulated mechanism accounts for the modification of the macroscopic properties of Ca-alginate aerogel in relation to both humid and aqueous environments.

[Gd(AAZTA)]- Derivatives with n-Alkyl Acid Side Chains Show Improved Properties for Their Application as MRI Contrast Agents*.

Herein, the synthesis and an extensive characterization of two novel Gd(AAZTA) (AAZTA=6-amino-6-methylperhydro-1,4-diazepine tetra acetic acid) derivatives functionalized with short (C2 and C4 ) n-alkyl acid functions are reported. The carboxylate functionality is the site for further conjugations for the design of more specific contrast agents (CAs). Interestingly, it has been found that the synthesized complexes display enhanced properties for use as MRI contrast agents on their own. The stability constants determined by using potentiometric titration and UV/Vis spectrophotometry were slightly higher than the one reported for the parent Gd(AAZTA) complex. This observation might be accounted for by the larger sigma-electron donation of the acyl substituents with respect to the one provided by the methyl group in the parent complex. As far as concerns the kinetic stability, transmetallation experiments with endogenous ions (e.g. Cu2+ ) implied that the Gd3+ ions present in these Gd(AAZTA) derivatives show somewhat smaller susceptibility to chemical exchange towards these ions at 25 °C, close to the physiological condition. The 1 H NMR spectra of the complexes with EuIII and YbIII displayed a set of signals consistent with half the number of methylene protons present on each ligand. The number of resonances was invariant over a large range of temperatures, suggesting the occurrence of a fast interconversion between structural isomers. The relaxivity values (298 K, 20 MHz) were consistent with q=2 being equal to 8.8 mm-1 s-1 for the C2 derivative and 9.4 mm-1 s-1 for the C4 one, that is, sensibly larger than the one reported for Gd(AAZTA) (7.1 mm-1 s-1 ). Variable-temperature (VT)-T2 17 O NMR measurements showed, for both complexes, the presence of two populations of coordinated water molecules, one in fast and one in slow exchange with the bulk water. As the high-resolution 1 H NMR spectra of the analogs with EuIII and YbIII did not show the occurrence of distinct isomers (as frequently observed in other macrocyclic lanthanide(III)-containing complexes), we surmised the presence of two fast-interconverting isomers in solution. The analysis of the 17 O NMR VT-T2 profiles versus temperature allowed their relative molar fraction to be established as 35 % for the isomer with the fast exchanging water and 65 % for the isomer with the water molecules in slower exchange. Finally, 1 H NMRD profiles over an extended range of applied magnetic field strengths have been satisfactory fitted on the basis of the occurrence of the two interconverting species.

[The value of artificial and human intelligence - the example of bone scintigraphy]. / A mesterséges és emberi intelligencia értéke a csontszcintigráfia példáján keresztül.

We present a possible method of Artificial Intelligence (AI) based applications that can effectively filter noise-sensitive bone scintigraphy images. The use of special AI, based on preliminary examinations, allows us to significantly reduce study time or activity administered to the patient, thus reducing the patient, assistant, and physician radiation. We present the features of the AI filtering application, its teaching process, which is important to understand, so that the physician can safely take the processed image of the AI as a "secondary reliable opinion" to help them make a more accurate diagnosis. We also examine the robustness of the algorithm, the specificities and challenges of complex clinical control.

[Methods and feasibilities of texture analysis in PET diagnostics]. / A textúraanalízis módszere és lehetoségei a PET-diagnosztikában.

One of the current research objectives of medical imaging is to determine the prognostic value of tumor textures and related numerical values. In PET/CT studies the diagnostic and prognostic values of specific texture parameters were confirmed at several tumor types (lung, prostate, cervix, colon, head and neck). However, the results are often contradictory, various publications find different texture parameters useful for the same tumor type. The reason for the contradictions is partly methodological, since the definition and the calculation of texture data is a multi-step process. Such steps include scan protocol, image reconstruction, tumor segmentation, re-sampling the voxel values and the form of texture algorithms. Recent publications show that by harmonizing these steps, the prognostic power and reliability of the texture features can be improved. The most optimal way of harmonization would be a special phantom application that could simulate inhomogeneous distributions typical for tumor tissues, with high reproducibility.

Gelatin content governs hydration induced structural changes in silica-gelatin hybrid aerogels - Implications in drug delivery.

Silica-gelatin hybrid aerogels of varying gelatin content (from 4 wt.% to 24 wt.%) can be conveniently impregnated with hydrophobic active agents (e.g. ibuprofen, ketoprofen) in supercritical CO2 and used as drug delivery systems. Contrast variation neutron scattering (SANS) experiments show the molecular level hybridization of the silica and the gelatin components of the aerogel carriers. The active agents are amorphous, and homogeneously dispersed in these porous, hybrid matrices. Importantly, both fast and retarded drug release can be achieved with silica-gelatin hybrid aerogels, and the kinetics of drug release is governed by the gelatin content of the carrier. In this paper, for the first time, a molecular level explanation is given for the strong correlation between the composition and the functionality of a family of aerogel based drug delivery systems. Characterization of the wet aerogels by SANS and by NMR diffusiometry, cryoporometry and relaxometry revealed that the different hydration mechanisms of the aerogels are responsible for the broad spectrum of release kinetics. Low-gelatin (4-11 wt.%) aerogels retain their open-porous structure in water, thus rapid matrix erosion dictates fast drug release from these carriers. In contrast to this, wet aerogels of high gelatin content (18-24 wt.%) show well pronounced hydrogel-like characteristics, and a wide gradual transition zone forms in the solid-liquid interface. The extensive swelling of the high-gelatin hybrid backbone results in the collapse of the open porous structure, that limits mass transport towards the release medium, resulting in slower, diffusion controlled drug release. STATEMENT OF SIGNIFICANCE: Developing new drug delivery systems is a key aspect of pharmaceutical research. Supercritically dried mesoporous aerogels are ideal carriers for small molecular weight drugs due to their open porous structures and large specific surface areas. Hybrid silica-gelatin aerogels can display both fast and retarded drug release properties based on the gelatin contents of their backbones. The structural characterization of the aerogels by SANS and by NMR diffusiometry, cryoporometry and relaxometry revealed that the different hydration mechanisms of the hybrid backbones are responsible for the broad spectrum of release kinetics. The molecular level understanding of the functionality of these hybrid inorganic-biopolymer drug delivery systems facilitates the realization of quality-by-design in this research field.

Impact of intensity discretization on textural indices of [18F]FDG-PET tumour heterogeneity in lung cancer patients.

Quantifying tumour heterogeneity from [18F]FDG-PET images promises benefits for treatment selection of cancer patients. Here, the calculation of texture parameters mandates an initial discretization step (binning) to reduce the number of intensity levels. Typically, three types of discrimination methods are used: lesion relative resampling (LRR) with fixed bin number, lesion absolute resampling (LAR) and absolute resampling (AR) with fixed bin widths. We investigated the effects of varying bin widths or bin number using 27 commonly cited local and regional texture indices (TIs) applied on lung tumour volumes. The data set were extracted from 58 lung cancer patients, with three different and robust tumour segmentation methods. In our cohort, the variations of the mean value as the function of the bin widths were similar for TIs calculated with LAR and AR quantification. The TI histograms calculated by LRR method showed distinct behaviour and its numerical values substantially effected by the selected bin number. The correlations of the AR and LAR based TIs demonstrated no principal differences between these methods. However, no correlation was found for the interrelationship between the TIs calculated by LRR and LAR (or AR) discretization method. Visual classification of the texture was also performed for each lesion. This classification analysis revealed that the parameters show statistically significant correlation with the visual score, if LAR or AR discretization method is considered, in contrast to LRR. Moreover, all the resulted tendencies were similar regardless the segmentation methods and the type of textural features involved in this work.

Activity painting: PET images of freely defined activity distributions applying a novel phantom technique.

The aim of this work was to develop a novel phantom that supports the construction of highly reproducible phantoms with arbitrary activity distributions for PET imaging. It could offer a methodology for answering questions related to texture measurements in PET imaging. The basic idea is to move a point source on a 3-D trajectory in the field of view, while continuously acquiring data. The reconstruction results in a 3-D activity concentration map according to the pathway of the point source. A 22Na calibration point source was attached to a high precision robotic arm system, where the 3-D movement was software controlled. 3-D activity distributions of a homogeneous cube, a sphere, a spherical shell and a heart shape were simulated. These distributions were used to measure uniformity and to characterize reproducibility. Two potential applications using the lesion simulation method are presented: evaluation in changes of textural properties related to the position in the PET field of view; scanner comparison based on visual and quantitative evaluation of texture features. A lesion with volume of 50x50x50 mm3 can be simulated during approximately 1 hour. The reproducibility of the movement was found to be >99%. The coefficients of variation of the voxels within a simulated homogeneous cube was 2.34%. Based on 5 consecutive and independent measurements of a 36 mm diameter hot sphere, the coefficient of variation of the mean activity concentration was 0.68%. We obtained up to 18% differences within the values of investigated textural indexes, when measuring a lesion in different radial positions of the PET field of view. In comparison of two different human PET scanners the percentage differences between heterogeneity parameters were in the range of 5-55%. After harmonizing the voxel sizes this range reduced to 2-16%. The general activity distributions provided by the two different vendor show high similarity visually. For the demonstration of the flexibility of this method, the same pattern was also simulated on a small animal PET scanner giving similar results, both quantitatively and visually. 3-D motion of a point source in the PET field of view is capable to create an irregular shaped activity distribution with high reproducibility.

[Potential relationship between juice cleanse diets and eating disorders. A qualitative pilot study]. / A léböjtkúrák és az atípusos evészavarok lehetséges kapcsolata. Kvalitatív elotanulmány.

INTRODUCTION AND AIM: There are two notable eating behaviors that are not far from having their own category as a mental disorder: the purging disorder, that is already among the DSM-5 non-specific eating disorders, and orthorexia nervosa, when a person is fixating too much on healthy foods. Our purpose is to describe how these can be observed in recreational juice cleanse camps, which are very popular today as an alternative health trend. METHOD: The first author recorded her data during multisited ethnographic observations in two Hungarian juice cleanse camps. Based on the diary logs, notes and interviews collected, we will present the motives of eating anomalies that the participants had shown. RESULTS: The main motive of the camp is "detoxification". The lack of solid food, drastically low calorie intake and lots of physical activity will bring an inevitable change in the body, that is interpreted as toxins leaving the body. Participants have also included deliberate use of laxatives in their everyday routines, with which they associate positive connotations and are linked to the spiritual processes of "letting it go" and "renewal" in the spirit of a holistic approach. The use of symbols in the physiological processes was highly noticeable. Rapid weight loss due to diuresis, the desire for "clean" meals, and "self-rewarding" borrowed from the esoteric-self-help culture are also common motives. Due to the refeeding complications, so far two deaths have been reported by camp organizers. CONCLUSIONS: Both purging disorder and orthorexia nervosa can be well-identified in our observations. This shows that also in the non-clinical environment, there is an institutionalization of eating habits that are dangerous to the health. This "detox" is not only physiologically harmful, but it is not proved to provide long-term help in mental health either. As a solution, we advocate developing an appropriate health communication plan for misconceptions about healthy lifestyle and eating, and also a promotion of psychotherapeutic opportunities. Orv Hetil. 2018; 159(28): 1153-1157.

Equilibrium Thermodynamics, Formation, and Dissociation Kinetics of Trivalent Iron and Gallium Complexes of Triazacyclononane-Triphosphinate (TRAP) Chelators: Unraveling the Foundations of Highly Selective Ga-68 Labeling.

In order to rationalize the influence of FeIII contamination on labeling with the 68Ga eluted from 68Ge/68Ga-generator, a detailed investigation was carried out on the equilibrium properties, formation and dissociation kinetics of GaIII- and FeIII-complexes of 1,4,7-triazacyclononane-1,4,7-tris(methylene[2-carboxyethylphosphinic acid]) (H6TRAP). The stability and protonation constants of the [Fe(TRAP)]3- complex were determined by pH-potentiometry and spectrophotometry by following the competition reaction between the TRAP ligand and benzhydroxamic acid (0.15 M NaNO3, 25°C). The formation rates of [Fe(TRAP)] and [Ga(TRAP)] complexes were determined by spectrophotometry and 31P-NMR spectroscopy in the pH range 4.5-6.5 in the presence of 5-40 fold HxTRAP(x-6) excess (x = 1 and 2, 0.15 M NaNO3, 25°C). The kinetic inertness of [Fe(TRAP)]3- and [Ga(TRAP)]3- was examined by the trans-chelation reactions with 10 to 20-fold excess of HxHBED(x-4) ligand by spectrophotometry at 25°C in 0.15 M NaCl (x = 0,1 and 2). The stability constant of [Fe(TRAP)]3- (logKFeL = 26.7) is very similar to that of [Ga(TRAP)]3- (logKGaL = 26.2). The rates of ligand exchange reaction of [Fe(TRAP)]3- and [Ga(TRAP)]3- with HxHBED(x-4) are similar. The reactions take place quite slowly via spontaneous dissociation of [M(TRAP)]3-, [M(TRAP)OH]4- and [M(TRAP)(OH)2]5- species. Dissociation half-lives (t1/2) of [Fe(TRAP)]3- and [Ga(TRAP)]3- complexes are 1.1 × 105 and 1.4 × 105 h at pH = 7.4 and 25°C. The formation reactions of [Fe(TRAP)]3- and [Ga(TRAP)]3- are also slow due to the formation of the unusually stable monoprotonated [*M(HTRAP)]2- intermediates [*logKGa(HL) = 10.4 and *logKFe(HL) = 9.9], which are much more stable than the [*Ga(HNOTA)]+ intermediate [*logKGa(HL) = 4.2]. Deprotonation and transformation of the monoprotonated [*M(HTRAP)]2- intermediates into the final complex occur via OH--assisted reactions. Rate constants (kOH) characterizing the OH--driven deprotonation and transformation of [* Ga(HTRAP)]2- and [*Fe(HTRAP)]2- intermediates are 1.4 × 105 M-1s-1 and 3.4 × 104 M-1s-1, respectively. In conclusion, the equilibrium and kinetic properties of [Fe(TRAP)] and [Ga(TRAP)] complexes are remarkably similar due to the close physico-chemical properties of FeIII and GaIII-ions. However, a slightly faster formation of [Ga(TRAP)] over [Fe(TRAP)] provides a rationale for a previously observed, selective complexation of 68GaIII in presence of excess FeIII.