An optimized imaging protocol for [99mTc]Tc-DPD scintigraphy and SPECT/CT quantification in cardiac transthyretin (ATTR) amyloidosis

Background In [99mTc]Tc-DPD scintigraphy for myocardial ATTR amyloidosis, planar images 3 hour p.i. and SPECT/CT acquisition in L-mode are recommended. This study investigated if earlier planar images (1 hour p.i.) are beneficial and if SPECT/CT acquisition should be preferred in H-mode (180° detector angle) or L-mode (90°). Methods In SPECT/CT phantom measurements (NaI cameras, N = 2; CZT, N = 1), peak contrast recovery (CRpeak) was derived from sphere inserts or myocardial insert (cardiac phantom; signal-to-background ratio [SBR], 10:1 or 5:1). In 25 positive and 38 negative patients (reference: endomyocardial biopsy or clinical diagnosis), Perugini scores and heart-to-contralateral (H/CL) count ratios were derived from planar images 1 hour and 3 hour p.i. Results In phantom measurements, accuracy of myocardial CRpeak at SBR 10:1 (H-mode, 0.95-0.99) and reproducibility at 5:1 (H-mode, 1.02-1.14) was comparable for H-mode and L-mode. However, L-mode showed higher variability of background counts and sphere CRpeak throughout the field of view than H-mode. In patients, sensitivity/specificity were ≥ 95% for H/CL ratios at both time points and visual scoring 3 hour. At 1 hour, visual scores showed specificity of 89% and reduced reader’s confidence. Conclusions Early DPD images provided no additional value for visual scoring or H/CL ratios. In SPECT/CT, H-mode is preferred over L-mode, especially if quantification is applied apart from the myocardium.

A Method of Film Retroreflection Index Calculated by Reflectance Spectrum

Retroreflective film are used widely in traffic and municipal field as information carrier, the retroreflection index is considered the most important parameter, test methods of this parameter including absolute and relative method, traditional instruments are consisted of light source, photometric detector, angle adjust device, etc. The complex structure of instrument add the uncertainty component, so reflectance spectrum is used to calculated the film retroreflection index, this method would improve the testament accuracy and provide more light sources choices without structure adjustment.

The Si/SiO2 Interface: Atomic Structures, Composition, Strain and Energetics

A number of recent studies of grain boundaries and heterophase interfaces have demonstrated the power of combining Z-contrast STEM imaging, EELS and first-principles theoretical modeling to give an essentially complete atomic scale description of structure, bonding and energetics. Impurity sites and valence can be determined experimentally and configurations determined through calculations.Here we present an investigation of the Si/SiO2 interface. The Z-contrast image in Fig. la, taken with the VG Microscopes HB603U STEM, shows that the atomic structure of Si is maintained up to the last layers visible. The decrease in intensity near the interface could originate from interfacial roughness of around one unit cell (∼0.5 nm), or may represent dechanneling in the slightly buckled columns induced by the oxide. Fig. lb, taken from a sample with ∼1 nm interface roughness, shows a band of bright contrast near the interface. This is not due to impurities or thickness variation since it disappears on increasing the detector angle from 25 mrad to 45 mrad (Fig. lc), and is therefore due to induced strain.

The Si/SiO2 Interface: Atomic Structures, Composition, Strain And Energetics

A number of recent studies of grain boundaries and heterophase interfaces have demonstrated the power of combining Z-contrast STEM imaging, EELS and first-principles theoretical modeling to give an essentially complete atomic scale description of structure, bonding and energetics. Impurity sites and valence can be determined experimentally and configurations determined through calculations.Here we present an investigation of the Si/SiO2 interface. The Z-contrast image in Fig. la, taken with the VG Microscopes HB603U STEM, shows that the atomic structure of Si is maintained up to the last layers visible. The decrease in intensity near the interface could originate from interfacial roughness of around one unit cell (∼0.5 nm), or may represent dechanneling in the slightly buckled columns induced by the oxide. Fig. lb, taken from a sample with ∼1 nm interface roughness, shows a band of bright contrast near the interface. This is not due to impurities or thickness variation since it disappears on increasing the detector angle from 25 mrad to 45 mrad (Fig. lc), and is therefore due to induced strain.

Z-contrast imaging of catalysts in the 300 kV STEM

Z-contrast imaging in the scanning transmission electron microscope has become the accepted technique for imaging sub-nanometer catalyst clusters, utilizing the high angle annular detector introduced by Howie. The lack of coherent phase contrast effects greatly assists the identification of small clusters, especially near the resolution limit of the microscope. The choice of inner detector angle depends on the system being studied. The highest signal to noise ratio is obtained with the smallest inner detector angle, but increasing this angle significantly reduces the contribution of coherently scattered electrons, which is advantageous for crystalline support materials. In this case, small metal clusters may be unambiguosly distinguished from diffracting regions of the support, and their size distributions determined. Fig 1 compares two preparations of 1 wt% Pd on γ-Al2O3, prepared from palladium nitrate solution, and aged at 600°C for (a) 6 hours, and (b) 24 hours. Images were taken with a VG Microscopes HB501UX 100 kV STEM, using a probe size of ∼3Å The narrower size distribution resulting from the longer aging time is clearly observed.

The Importance of the Detector Angle in STEM Imaging of Crystals

The image obtained in a scanning transmission electron microscope (STEM) is related to that obtained, under otherwise identical conditions, in the conventional transmission electron microscope (CTEM) by the principle of reciprocity. This principle is only applicable under rigorously defined mathematical conditions which are difficult to achieve in practice, nevertheless its general validity has been demonstrated experimentally for both amorphous and crystalline materials. The principle of reciprocity states, in part, that if equivalent beam cone angles are utilized then the STEM and CTEM images should be similar. Conversely, for a given set of electron-optical conditions in the STEM mode, the expected form of the images can be deduced from a knowledge of the CTEM image under reciprocally related conditions.

Simplified Calculation of Phase Contrast for Finite Detector and Illumination Angles

Modern microscopes are capable of resolutions of the order of 2 Å. To fully utilize this capability, the experimentalist must turn to reliable calculations of contrast to optimize the various parameters available.However, until recently (e.g. Ref. 1), most calculations of phase contrast were performed using restricted conditions such as parallel illumination in the CTEM and a point detector in the STEM, because exact calculations using general geometries became rather involved. This can be seen from Eq. (1) for phase contrast in the general case of finite illumination angle, αO, as a function of distance from and finite detector angle βO.