Measurement Of Local Variations Research Articles

Abstract A040: CT Radiomics to predict early recurrence of margin-negative resectable pancreatic ductal adenocarcinoma

Abstract Radiographic CT/MRI staging is pivotal to accurate therapeutic decision-making, and guides the surgical resectability of pancreatic ductal adenocarcinoma (PDAC). The extent of vascular involvement of the lesion as seen through radiographic imaging, which differentiates the regional versus locally advanced disease, and therefore upfront resectability. Following standard criteria, only about 20% of PDAC patients qualify for an upfront surgery but half of them recur within a year, despite the complete removal (margin-negative R0 resection) of the primary tumor It underscores the necessity for a better deciphering of the CT/MRI-based clinical imaging of PDAC using radiomics—the process of extracting high dimensional quantitative imaging information from radiographic images. We have previously described a prospective cohort of resected PDAC (n=161) at Memorial Sloan Kettering Cancer Center for preoperative CT angiography collected between 2009 and 2012. We demonstrated that CT texture features are associated with overall survival. Utilizing the same cohort of resected PDAC, the current study aims to develop a much deeper case-controlled algorithm to further identify the texture features are predictive of early recurrence for margin-negative PDAC patients. We selected all patients following these criteria: margin negative (R0), Gemcitabine/nab-paclitaxel adjuvant chemotherapy (excluding neoadjuvant), clinical-stage IIB, moderate tumor differentiation by histopathology, and no lymph node and distant metastasis. Based on these criteria, a total of 27 patients were selected, where 16 patients had recurred within a year of surgery (high-risk group) and the remaining 11 patients did not recur in 2-years (low-risk group). We focused on Gray-level co-occurrence (GLCM) based on Haralick’s features. GLCM is most extensively used to characterize the texture of a tumor via encoding the spatial distribution of voxels—neighboring pixels of an image. A total of 18 GLCM features were extracted from manually segmented CT of PDAC primary tumors. Univariate analysis with Wilcoxon-rank-sum test (p<0.05) revealed 4 features –energy (GLCM1) and entropy (GLCM9, GLCM17, and GLCM18) based were associated with early recurrence. Energy, or angular speed moment, is a measure of local variation in an image; higher energy represents homogeneity between neighboring pixels. On the contrary, entropy characterizes randomness within an image; higher entropy represents more heterogeneity. The energy feature GLCM1 was significantly lower in high-risk group, whereas the entropy features (GLCM 9, 17, and 18) were significantly higher in high-risk group compared to the low-risk group – suggesting the relationship of tumor heterogeneity with early recurrence. While proposing these GLCM features as the measure of tumor heterogeneity and early recurrence, we are validating them on a larger independent cohort, estimating their benchmark measures of predictive ability. The long-term goal is to develop these as radiomic biomarkers for better guiding the therapeutic decision-making of PDAC. Citation Format: Anwesha Dhara, Liana Langdon-Embry, Michael I. D’Angelica, T. Peter Kingham, Natally Horvat, William R. Jarnagin, Alice C. Wei, Jayasree Chakraborty. CT Radiomics to predict early recurrence of margin-negative resectable pancreatic ductal adenocarcinoma [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer; 2022 Sep 13-16; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2022;82(22 Suppl):Abstract nr A040.

Site-Specific Structural Variations Accompanying Tubular Assembly of the HIV-1 Capsid Protein

The 231-residue capsid (CA) protein of human immunodeficiency virus type 1 (HIV-1) spontaneously self-assembles into tubes with a hexagonal lattice that is believed to mimic the surface lattice of conical capsid cores within intact virions. We report the results of solid-state nuclear magnetic resonance (NMR) measurements on HIV-1 CA tubes that provide new information regarding changes in molecular structure that accompany CA self-assembly, local dynamics within CA tubes, and possible mechanisms for the generation of lattice curvature. This information is contained in site-specific assignments of signals in two- and three-dimensional solid-state NMR spectra, conformation-dependent 15N and 13C NMR chemical shifts, detection of highly dynamic residues under solution NMR conditions, measurements of local variations in transverse spin relaxation rates of amide 1H nuclei, and quantitative measurements of site-specific 15N–15N dipole–dipole couplings. Our data show that most of the CA sequence is conformationally ordered and relatively rigid in tubular assemblies and that structures of the N-terminal domain (NTD) and the C-terminal domain (CTD) observed in solution are largely retained. However, specific segments, including the N-terminal β-hairpin, the cyclophilin A binding loop, the inter-domain linker, segments involved in intermolecular NTD–CTD interactions, and the C-terminal tail, have substantial static or dynamical disorder in tubular assemblies. Other segments, including the 310-helical segment in CTD, undergo clear conformational changes. Structural variations associated with curvature of the CA lattice appear to be localized in the inter-domain linker and intermolecular NTD–CTD interface, while structural variations within NTD hexamers, around local 3-fold symmetry axes, and in CTD–CTD dimerization interfaces are less significant.

The Measurement of Local Variation in Shape.

Geometric morphometrics comprises tools for measuring and analyzing shape as captured by an entire set of landmark configurations. Many interesting questions in evolutionary, genetic, and developmental research, however, are only meaningful at a local level, where a focus on "parts" or "traits" takes priority over properties of wholes. To study variational properties of such traits, current approaches partition configurations into subsets of landmarks which are then studied separately. This approach is unable to fully capture both variational and spatial characteristics of these subsets because interpretability of shape differences is context-dependent. Landmarks omitted from a partition usually contain information about that partition's shape. We present an interpolation-based approach that can be used to model shape differences at a local, infinitesimal level as a function of information available globally. This approach belongs in a large family of methods that see shape differences as continuous "fields" spanning an entire structure, for which landmarks serve as reference parameters rather than as data. We show, via analyses of simulated and real data, how interpolation models provide a more accurate representation of regional shapes than partitioned data. A key difference of this interpolation approach from current morphometric practice is that one must assume an explicit interpolation model, which in turn implies a particular kind of behavior of the regions between landmarks. This choice presents novel methodological challenges, but also an opportunity to incorporate and test biomechanical models that have sought to explain tissue-level processes underlying the generation of morphological shape.

Collagen Content and Organization Relate to Bone Nanomechanical Properties

AbstractCancellous bone plays an important load-bearing role in the skeleton, yet relatively little is known about the microstructure-mechanical property relationships of the tissue at the sub-10 [.proportional]m level. Cancellous tissue is characterized by a layered microstructure with variable proportions of collagen and mineral. The lamellar material is substantially stiffer than the interlamellar material at the nanomechanical level. However, the microstructural origin of the observed differences in mechanical properties of these structures has not been investigated. In this study, second harmonic generation microscopy was used to examine collagen in human vertebral cancellous bone. At the same location in the tissue, nanoindentation was used to assess the indentation modulus of lamellar and interlamellar bone. The stiff lamellae corresponded to areas of highly ordered, collagen-rich material, while the compliant interlamellar regions corresponded to areas of unoriented or collagen-poor material. The lamellar bone was approximately 30% stiffer and contained approximately 50% more oriented collagen than the interlamellar bone. These observed differences in the mechanical properties and collagen content and organization of lamellar and interlamellar tissue are consistent with previous scanning electron microscopy studies showing greater mineral and collagen content and organization in lamellar bone. Given the well-known coupling between collagen and mineral in bone tissue, the mineral distribution may mirror that of the aligned collagen. However, similar measurements of local variations in mineral content are needed to confirm this hypothesis and may provide additional insights into the tissue nanomechanical behavior.

Measurement of local variations in atmospheric nitrogen dioxide levels in Sapporo, Japan, using a new method with high spatial and high temporal resolution

A nitrogen dioxide (NO 2) monitoring system with an irreversible sensor has been developed. The sensor consists of a porous glass substrate impregnated with Saltzman reagents and the NO 2 concentration is determined from the sensor’s light transmittance. The correlation coefficient for the NO 2 concentration obtained with this device and that obtained with a commercial NO x analyzer was 0.79. A number of these devices were set up at the Sapporo Experimental Area in July 2001. Atmospheric NO 2 concentrations recorded from 9 to 22 July 2001 are described in terms of local spatial variations and in relation to differences in distance from a roadway intersection. At most sites the NO 2 level fluctuated throughout the day, and the general pattern consisted of a high level in the morning and evening and a low level during the night and in the afternoon. Proximity to road traffic increased the mean NO 2 concentration level, and the concentration decreased with distance from the intersection. The NO 2 gradient generally tended to decrease with distance from the intersection, and the average NO 2 concentrations over half a day and over 1 day at the intersection were respectively 50% and 36% higher than the concentration 150 m from the intersection. We also investigated the relationships between NO 2 levels, local meteorological conditions and the location conditions. At a measurement point on the side of a high building, the concentration was high when the measurement point was sheltered and low when it was exposed to the wind. The influence of a high building extends over a range of tens of meters, which is equal to the height of the building.

Micron-Resolution Photocurrent of CdTe Solar Cells Using Multiple Wavelengths

ABSTRACTAn apparatus developed recently at Colorado State University utilizes a diffractionlimited optics system and a high-resolution translation system to measure the laser-induced photocurrent at resolutions of 1 μm and equivalent incident laser intensities of 1 sun (100 mW/cm2). Multiple lasers in the 635-830 nm range can be easily selected by changing the fiberoptic connectors. The spot profile and location are unchanged when different lasers are selected. In addition, a laser temperature tuned through the 825-857 nm range allows measurement of local variations in the quantum efficiency near the CdTe band gap, which track intermixing of CdS/CdTe. This capability extends the previous analysis, which includes the separation of series resistance and shunting effects. The effect of post-deposition processing and elevated temperature stress on local variations in electrical and optical parameters, especially using the near-bandgap wavelengths, are examined using a series of samples fabricated at NREL.

Measurement of local variations in spacing and orientation of lattice plane of synthetic quartz

Local variations in spacing and orientation of lattice plane (01 1 0) of quartz in Y-cut plates cut from synthetic crystals were determined with high accuracy from X-ray topographs taken successively at various angular positions around the Bragg position using the double crystal arrangement of parallel setting. The lattice spacing varies with the growth sectors of the crystal in the range of 0 < Δ d/ d < 1.5 × 10 -5 ( d is the lattice spacing and Δ d is the lattice spacing variation) except the seed area. The orientation of the lattice plane varies by a few seconds of arc over the whole Y-plates in characteristics ways. The contents of impurities A1, Fe and Na in each growth sector were analyzed and related with the lattice spacing variation. The variation in the A1 and Na concentrations corresponds well with that in the lattice spacing. From the comparison of the variation both in the spacing and orientation of the lattice plane, the existence of the internal stress is deduced, which arises from the cell dimension difference among various parts of the crystal. The effect of the internal stress on the spacing and orientation of the lattice plane is discussed qualitatively.

The use of geophysical methods in engineering geology. Part 2: Electrical resistivity, magnetic and gravity methods : Higginbottom, IE 8F, 8R Ground Engng, V9, N2, Mar. 1976, P34–38

Although electrical is more versatile than other shallow geophysical exploration methods in respect of the range of geophysical situations with which it can contend, its many practical and interpretative limitations restrict its success to comparatively simple cases on land. Magnetic and gravity methods, on the other hand can be used over water. The many variations of the electrical techniques are all based on passing a current through the ground between certain electrodes and measuring the potential difference resulting between other (potential) electrodes set up in the path of the current, from which a quantity termed apparent resistivity can be calculated. The detection of changes in is described, and the ascribing of geological meaning to the recorded variations is discussed. The detailed interpretation (carried out by curve-matching techniques) of a can be complicated and expensive, calling for the highest degree of experience and objective data. The advantages of the method over other methods are noted. The details are outlined of the magnetic method which depends on the measurement of local variations in the earth's total magnetic field strength. Mechanical magnometers and fluxgate magnetometers are described. Gravity methods are generally restricted to the location of faults and for the detection of large subsurface voids. The observation and reduction of gravity readings are discussed.

A far-ultraviolet photometer for planetary surface analysis

The measurement of local variations in the far-ultraviolet albedo is explored as a means of detecting changes in the refractive index of rocks and dust on the surface of atmosphereless planets and satellites. Far-ultraviolet spectrophotometric measurements of the lunar surface which were obtained on the Apollo 17 orbital mission are presented to demonstrate that significant albedo variations occur in the spectral range 120 to 170 nm. These data also confirm the hypothesis that the albedo variations represent refractive index differences in the surface materials. A three-band photometer is described which, when put in orbit around a solar system object, is capable of providing refractive index maps with a sensitivity of 1 part in the second decimal place and with kilometer resolution. Comparative surface composition and surface history analyses based on such maps are discussed.