Longitudinal Spatial Resolution Research Articles

Plasmon waveguide resonance for tag-free selective Raman detection of biochemical composition in single-cell

Highly selective and non-radioactive Raman detection of the biochemical composition of living single-cell is a key method of evaluating complex biological reaction processes. Conventional selective Raman detection relies on tagging technology to separate the Raman signals from the different cell structures, which involves both a complex synthesis process and a long incubation time. To address this, we present a tag-free Raman selective detection with plasmon waveguide resonance (PWR). PWR biochemical composition detection exhibits a high longitudinal spatial resolution based on the surface and bulk response of low- and high-order modes. Hence, compared with conventional selective Raman detection with tagging technology, it can distinguish Raman signals from cell structures more effectively, without an antibody and label, providing effective tag-free selective detection with high spatial resolution. In addition, rapid selective detection can be achieved using the PWR Raman scattering biochemical composition detection, thereby improving the stability of a living single cell without a long incubation time. Moreover, the electromagnetic field of the evanescent field can be significantly amplified by the proposed PWR biochemical composition detection, which also enhances the Raman signal with high sensitivity without requiring a complicated fabrication process. The proposed PWR has potential applications in drug release and living-cell analysis.

Theoretical Foundations of Quantum Spectral-Domain Optical Coherence Tomography with Frequency Scanning

A quantum spectral-domain optical coherence tomography technique based on the control of the joint spectral amplitude of a biphoton has been developed. An analytical expression for a quantum spectral-domain optical coherence tomography signal has been obtained in the case of a Gaussian joint spectral amplitude. The effect of the shape of the joint spectral amplitude of the biphoton on the resulting interference signal has been analyzed. The possibility of improving the quality of the interference signal by controlling the parameters of the joint spectral amplitude has been considered. It has been shown theoretically that the proposed approach provides a higher longitudinal spatial resolution than other optical coherence tomography techniques.

Determination of the Spatial Resolution in the Case of Imaging Magnetic Fields by Polarized Neutrons

One of the most important parameters characterizing imaging systems (neutrons, X-rays, etc.) is their spatial resolution. In magnetic field imaging, the spatial resolution depends on the (magnetic) resolution of the depolarization of spin-polarized neutrons. This should be realized by different methods, but they all have in common that a spin-polarizing and spin-analyzing system is part of the resolution function. First a simple and useful method for determining the spatial resolution for unpolarized neutrons is presented, and then methods in the case of imaging with polarized neutrons. Spatial resolution in the case of polarized neutron imaging is fundamentally different from ‘classical’ spatial resolution. Because of π-periodicity, the shortest path along which a spin-flip can occur is a measure of ‘magnetic’ spatial resolution. Conversely, the largest detectable magnetic field (B-field) within a given path length is also a measure of magnetic spatial resolution. This refers to the spatial resolution in the flight direction of the neutrons (Δy). The Δx and Δz refers to the spatial resolution in x- or z-direction; however, in these cases a different method must be used. Therefore, two independent methods are used to distinguish longitudinal and lateral spatial resolution, one method to determine the modulation transfer function (MTF) by recording the frequency-dependent fringe contrast of magnetic field images of a coil (longitudinal spatial resolution), and the second method, to observe the fringe displacement at the detector as a function of magnetic motion, provided that the accuracy of the motion is much better than the pixel size (at least half the pixel size) of the detector (lateral spatial resolution). The second method is a convolution of the fringe pattern with the pixel array of the detector.

Reciprocating propagation of laser pulse intensity in free space

Constant-speed straight-line propagation in free space is a basic characteristic of light, and spatiotemporal couplings recently were used to control light propagation. In the method of flying focus, where temporal chirp and longitudinal chromatism were combined, tunable-velocities and even backward-propagation were demonstrated. We studied the transverse and longitudinal effects of the flying focus in space-time and found in a specific physics interval existing an unusual reciprocating propagation that was quite different from the previous result. By increasing the Rayleigh length in space and the temporal chirp in time, the created flying focus can propagate along a longitudinal axis firstly forward, secondly backward, and lastly forward again, and the longitudinal spatial resolution improves with increasing the temporal chirp. When this light is applied in a radiation pressure simulation, a reciprocating radiation-force can be produced accordingly. This finding extends the control of light and might enable important potential applications.

The EBSD spatial resolution of a Timepix-based detector in a tilt-free geometry

Performing EBSD with a horizontal sample and a parallel EBSD detector sensor, enables safer specimen movements for data collection of large specimen areas and improves the longitudinal spatial resolution. The collection of electron backscattering patterns (EBSPs) at normal incidence to the electron beam has been revisited via the use of a direct electron detection (DED) sensor. In this article we present a fully operational DED EBSD detection system in this geometry, referred to as the tilt-free geometry. A well-defined Σ=3[101]{121} twin boundary in a Molybdenum bicrystal was used to measure the physical spatial resolution of the EBSD detector in this tilt-free geometry. In this study, two separate methods for estimating the spatial resolution of EBSD, one based on a pattern quality metric and the other on a normalised cross correlation coefficient were used. The spatial resolution was determined at accelerating voltages of 8 kV, 10 kV, 12 kV, 15 kV and 20 kV ranging from ~22−38 nm using the pattern quality method and ~31−46 nm using the normalised cross correlation method.

Performance tests of boron-coated straw detectors with thermal and cold neutron beams

Prototypes of in-house developed boron-coated straw (BCS) detectors have been tested in the thermal and cold neutron energy ranges. Their neutron detection performance has been benchmarked against the industry standard (detector tubes filled with 3He gas). The tests show that the BCS detectors perform near their theoretical limit regarding the detection efficiency, which is adequate for scientific instruments in the cold neutron energy range. The BCS detectors perform on par with 3He tubes in terms of signal to noise and timing resolution, and superior regarding longitudinal spatial resolution.

Utilidad de técnicas de imagen en la valoración de la enfermedad coronaria - Tomografía de coherencia óptica

Optic coherence tomography is a high resolution imaging technique that enables the lumen and the walls of the structures of the coronary vessel to be examined. It offers a tissue penetration on a millimetre scale (1-2mm) and a longitudinal and lateral spatial resolution on a micrometre scale. The resolution is in the order of 10-20μm, approximately 10 times superior to the resolution of intravascular ultrasound, which is in the order of 100-150μm, and is another intra-coronary imaging technique widely used in current clinical practice.Since its introduction more than 20 years ago, it has been increasingly used in research, as well as in clinical practice. It has been especially useful in the evaluation of the natural history of atherosclerosis, the description of the mechanisms of acute coronary syndrome, and the optimisation of coronary interventions. It currently has a special use in the diagnosis of culprit lesions in cases where angiograph is limited, in the planning of complex percutaneous catheterisation (diffuse diseases, bifurcations, and calcified lesions), and in cases of stent failures (thrombosis and re-stenosis). The latter is probably one of the par excellence indications, with the aim of understanding the pathophysiology and to provide the appropriate percutaneous treatment.In this review, emphasis will be made on the considerations for using optic coherence tomography as an intracoronary imaging technique in the diagnosis and classification of atherosclerotic disease.

An optical fiber Fabry-Perot interferometric sensor based on functionalized diaphragm for ultrasound detection and imaging

A miniature optical fiber ultrasonic sensor based on the Fabry-Perot interferometer (FPI) is proposed and experimentally demonstrated. The cavity of the interferometer is based on a section of hollow core fiber coated with a 353ND diaphragm. A well-define interference pattern is achieved, and the spectral sideband filter technique is used to interrogate the sensor. Because the thin reflective diaphragm is extremely sensitive to sound pressure, the signal-to-noise ratio of the sensor response reaches to 31.22 dB with the pulse ultrasonic excitation of 300 kHz. A clear interface information can be distinguished in physical model imaging, and the longitudinal spatial resolution is 5 mm. This proposed sensor has the advantages of being simple to fabricate, ultracompact in size, cost effective, corrosion resistance, and being highly stable.

On the use of an optoacoustic and laser ultrasonic imaging system for assessing peripheral intravenous access

We describe a universal system for research in combined real-time optoacoustic (OA) and laser-ultrasonic (LU) imaging. The results of its testing on the task of needle insertion into the blood vessel model diagnostics are presented. In OA mode, where laser light is absorbed directly in the sample, the contents of blood vessel model is clearly visible. In LU mode, where the short ultrasonic probe pulse scattered on the sample is detected, the needle is clearly visible. The developed solution combining OA and LU imaging modalities due to the common detection system allowed real-time diagnostics of the position of medical needles (0.63mm and 0.7mm in diameter) inside blood vessel models (1.6mm and 2.4mm in diameter). Frame rate was 10Hz. High longitudinal spatial resolution of the system − 0.1mm − allows distinguishing the two walls of the vessel model and the position of the needle inside.

43. Evaluation of abdominal CT protocols using a mathematical model observer

Introduction In the last decade, technological breakthroughs in CT allow an improvement of optimization process. With the introduction of iterative algorithms, an adjustment of clinical protocols has been achieved. Classical metrics were become insufficient to assess image quality of clinical protocols. An objective method, based on a clinical task has to be used. The goal of this study is to evaluate abdominal protocols on two newest CT, using a mathematical model observer. We can also underline the impact of a fully model-based iterative reconstruction algorithm when dealing with low-contrast detectability tasks. Method An anthropomorphic abdominal phantom (equivalent o 24 cm) with 8 and 5 mm low contrast targets (20 HU) was scanned on two CT systems: Revolution CT and CT750 HD, GE Healthcare. Peripheral rings (2.5 and 5 cm in thickness) were added to simulate different patient sizes. The phantom was scanned 15 times using a routine abdominal protocol with a slice thickness of 2.5 mm (0.625 mm for VEO® (MBIR algorithm); avoiding any MPR processing). On both units, the noise index was adjusted with the phantom’s size (i.e. 20, 26 and 32 HU). Images were reconstructed using FBP, ASIR50% and VEO® for CT750HD and ASIR-V at 0% and 50% for Revolution CT. To assess low-contrast detectability, a Channelized Hotelling Observer (CHO; 10 DDOG channels) was used. The area under the curve (AUC) index was chosen as figure of merit (FOM). Results Scanning the phantom on the CT750 HD, no significant difference appeared between FBP and ASIR50%. For the largest phantom size, a significant increase of 6% in low contrast detectability was recorded on 5mm targets using VEO (with a longitudinal spatial resolution four times higher) compared to ASIR50%. Concerning the Revolution CT no difference in detectability was noted between ASIR-V at 0% and 50%. Comparing the two CT systems the displayed CTDIvol values for the Revolution CT were systematically lower than for the CT750HD (reaching 40% for the thickest phantom). Low contrast detectability performances were comparable between ASIR-V50% and VEO®. Conclusion Dealing with CT750HD, despite a significantly longer reconstruction time, the use of VEO® on large patients is of particular interest since it yields to high image quality performances. Lower CTDIvol values are required with the Revolution CT than CT750HD to produce comparable low contrast detectability levels.

Evaluation of conventional imaging performance in a research whole-body CT system with a photon-counting detector array

This study evaluated the conventional imaging performance of a research whole-body photon-counting CT system and investigated its feasibility for imaging using clinically realistic levels of x-ray photon flux. This research system was built on the platform of a 2nd generation dual-source CT system: one source coupled to an energy integrating detector (EID) and the other coupled to a photon-counting detector (PCD). Phantom studies were conducted to measure CT number accuracy and uniformity for water, CT number energy dependency for high-Z materials, spatial resolution, noise, and contrast-to-noise ratio. The results from the EID and PCD subsystems were compared. The impact of high photon flux, such as pulse pile-up, was assessed by studying the noise-to-tube-current relationship using a neonate water phantom and high x-ray photon flux. Finally, clinical feasibility of the PCD subsystem was investigated using anthropomorphic phantoms, a cadaveric head, and a whole-body cadaver, which were scanned at dose levels equivalent to or higher than those used clinically. Phantom measurements demonstrated that the PCD subsystem provided comparable image quality to the EID subsystem, except that the PCD subsystem provided slightly better longitudinal spatial resolution and about 25% improvement in contrast-to-noise ratio for iodine. The impact of high photon flux was found to be negligible for the PCD subsystem: only subtle high-flux effects were noticed for tube currents higher than 300 mA in images of the neonate water phantom. Results of the anthropomorphic phantom and cadaver scans demonstrated comparable image quality between the EID and PCD subsystems. There were no noticeable ring, streaking, or cupping/capping artifacts in the PCD images. In addition, the PCD subsystem provided spectral information. Our experiments demonstrated that the research whole-body photon-counting CT system is capable of providing clinical image quality at clinically realistic levels of x-ray photon flux.

Stimulated Raman gas sensing by backward UV lasing from a femtosecond filament.

We perform a proof-of-principle demonstration of chemically specific standoff gas sensing, in which a coherent stimulated Raman signal is detected in the direction anticollinear to a two-color laser excitation beam traversing the target volume. The proposed geometry is intrinsically free space as it does not involve back-scattering (reflection) of the signal or excitation beams at or behind the target. A beam carrying an intense mid-IR femtosecond (fs) pulse and a parametrically generated picosecond (ps) UV Stokes pulse is fired in the forward direction. A fs filament, produced by the intense mid-IR pulse, emits a backward-propagating narrowband ps laser pulse at the 337 and 357 nm transitions of excited molecular nitrogen, thus supplying a counter-propagating Raman pump pulse. The scheme is linearly sensitive to species concentration and provides both transverse and longitudinal spatial resolution.

Initial results from a prototype whole-body photon-counting computed tomography system.

X-ray computed tomography (CT) with energy-discriminating capabilities presents exciting opportunities for increased dose efficiency and improved material decomposition analyses. However, due to constraints imposed by the inability of photon-counting detectors (PCD) to respond accurately at high photon flux, to date there has been no clinical application of PCD-CT. Recently, our lab installed a research prototype system consisting of two x-ray sources and two corresponding detectors, one using an energy-integrating detector (EID) and the other using a PCD. In this work, we report the first third-party evaluation of this prototype CT system using both phantoms and a cadaver head. The phantom studies demonstrated several promising characteristics of the PCD sub-system, including improved longitudinal spatial resolution and reduced beam hardening artifacts, relative to the EID sub-system. More importantly, we found that the PCD sub-system offers excellent pulse pileup control in cases of x-ray flux up to 550 mA at 140 kV, which corresponds to approximately 2.5×1011 photons per cm2 per second. In an anthropomorphic phantom and a cadaver head, the PCD sub-system provided image quality comparable to the EID sub-system for the same dose level. Our results demonstrate the potential of the prototype system to produce clinically-acceptable images in vivo.

A direct time measurement technique for the two-dimensional precision coordinate detectors based on thin-walled drift tubes

This article presents the results of a study of the longitudinal spatial resolution by means of the direct timing method (DTM) using 2m long and 9.53mm diameter straw tubes. The feasibility of achieving the spatial resolution (r.m.s.) better than 2cm over full length of the straw is demonstrated. The spatial resolution changes little when measured by detecting gammas from a Fe-55 gamma ray source or minimum ionizing electrons from a Ru-106 source. The use of the same type of front end electronics (FEE) both for measuring the drift time of ionization electrons and propagation time of a signal along the anode wire allows one to construct a detector capable for measuring the two dimensional coordinates of charged particles.

High Time-Resolved Three-Dimensional Imaging Using Ultrafast Optical Kerr Gate of Bismuth Glass

We have demonstrated the high time-resolved three dimensional (3-D) imaging using a chirped supercontinuum (SC) and an ultrafast optical Kerr gate (OKG) generated with a femtosecond laser, in which a sapphire plate and a Bi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> -B <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> -SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> oxide glass (BI glass) were used to generate the chirped SC and the optical Kerr gate, respectively. The experimental results show that the 3-D imaging using BI glass offers better temporal and longitudinal spatial resolution compared with CS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> .

Current status of low dose multi-detector CT in the urinary tract

Over the past several years, advances in the technical domain of computed tomography (CT) have influenced the trend of imaging modalities used in the clinical evaluation of the urinary system. Renal collecting systems can be illustrated more precisely with the advent of multi-detector row CT through thinner slices, high speed acquisitions, and enhanced longitudinal spatial resolution resulting in improved reformatted coronal images. On the other hand, a significant increase in exposure to ionizing radiation, especially in the radiosensitive organs, such as the gonads, is a concern with the increased utilization of urinary tract CT. In this article, we discuss the strategies and techniques available for reducing radiation dose for a variety of urinary tract CT protocols with metabolic clinical examples. We also reviewed CT for hematuria evaluation and related scan parameter optimization such as, reducing the number of acquisition phases, CT angiography of renal donors and lowering tube potential, when possible.

SU‐GG‐J‐192: Use of Optimized Oblique Anatomical Planes for Efficient and Accurate Organ and Tumor Segmentation

Purpose: To improve the efficiency and accuracy of tumor and normal organ segmentation by using optimized anatomical planes. Method and Materials: Contouring of tumors and normal organs is typically conducted using transverse computed tomography (CT) planes. This is due to the historical relationship between diagnostic radiology and radiation oncology, as well as the relatively poor longitudinal spatial resolution of CT relative to the transverse plane. We hypothesize that the accuracy and efficiency of segmentation will be improved if the contouring planes are aligned to anatomical landmarks and planes, similar to the methods used in surgery. This advance is made possible by the state‐of‐the art in CT systems that provide high spatial‐resolution images that do not bias the resolution in favor of the transverse plane. This program has three phases: 1) Design an algorithm that generates contour surfaces from nonparallel obliquely oriented contours. 2) Select oblique planes corresponding to surgical exposure techniques and evaluate the improved efficiency of segmentation using a custom‐generated organ surface library. 3) Develop a contouring toolset that includes tools to aid in navigating the CT dataset in 3 dimensions. Results: Phase 1 has been completed. Phase 2 is underway, with data from parotid segmentation showing progress for selecting anatomical planes similar to a superficial parotidectomy. Toolsets are being developed for phase 3, including methods for aligning the contouring plane with the anatomical reference landmarks as used in surgery. Conclusion: This process promises to provide a more efficient and effective method for manually segmenting structures based on the hypothesis that aligning the contouring planes to anatomical landmarks and structures will provide a more accurate segmentation process, and allow radiation therapy to be delivered with similar anatomical precision as surgical therapy. We anticipate this will be especially true for nodal target volumes.

Development studies for the ILC: Measurements and simulations for a time projection chamber with GEM technology

A Time Projection Chamber (TPC) with Gas Electron Multiplier (GEM) technology is well suited for usage as central tracker at the International Linear Collider (ILC). To study the high potential of this detector type a small prototype of 25 cm length was built in Karlsruhe and used in several experimental setups. In this publication the results of these measurements and of additional Monte Carlo simulations are presented. By introducing the so-called equivalent drift distance a combination of all results was possible leading to a recommended configuration of the multi-GEM tower for the ILC–TPC. It will be shown that for conditions considered in the TESLA–TDR the transverse spatial resolution will be able to reach 65 μ m for 10 cm and 190 μ m for 200 cm drift at the ILC. This as well as the expectations for longitudinal spatial resolution, for energy resolutions of the specific ionization, and for single pad row efficiency should be able to meet the requirements of a future ILC–TPC.

Studies With a GEM-TPC Prototype for the ILC: Dependencies of Spatial Resolution for Short Drift Distances in a 4 T Magnetic Field

Time Projection Chambers (TPCs) with a micro pattern gas amplification stage are best suited for high precision tracking at a future linear collider. Among the major advantages of this technology are the vanishingly small distortions due to EtimesB effects. In order to prove the functionality of this concept, and to study the behavior of such TPCs in high magnetic fields, a small cylindrical TPC prototype has been equipped with two Gas Electron Multipliers (GEMs) and a micro pad readout plane. We discuss results of a test of this setup in high magnetic fields at DESY, where the prototype was placed into a solenoidal magnet with a field of up to 5.5 T. The studies include measurements of transverse and longitudinal spatial resolution using cosmic rays. Special interest is given to dependencies on drift distance, pad geometry, sampling rate, and on various cuts on angles and chi2. We also briefly describe a new method of data analysis and show that the spatial resolution can be improved by taking only a smaller fraction of all data points. With the used gas mixture of Ar:CH4:CO2-93:5:2, transverse spatial resolutions down to 100mum can be achieved

Multidetector CT (64 Slices) of the liver: examination techniques

Sixty-four-row MDCT, although developed primarily for cardiac imaging, has the potential to have a great impact on liver imaging as well. Liver-imaging protocols with sub-millimeter collimation improve longitudinal spatial resolution, making the acquired dataset a real isotropic volume perfectly designed for optimal three-dimensional rendering and accurate organ and lesion volumetry. The 64-row detector array offers a wide volumetric coverage (up to 40 mm), suitable not only for shortening scanning time and improving spatial resolution, but also for including a large volume per single rotation, particularly useful for accurate CT perfusion studies. In order to take full benefit from the enormous performance offered by new 64-row MDCT scanners, imaging protocols need to be redesigned. Due to the extremely short scanning window, contrast agent injection should be performed at high flow rate and followed by saline bolus chaser; the use of highly concentrated contrast media might be useful. Timing should be accurately calculated either by a test bolus or, better, by using an automatic bolus-detection technique. Radiation exposure is kept under control, using automatic device-modulating dose delivery according to the patient's anatomy. Finally, the evaluation of acquired volumetric datasets needs the extensive use of a dedicated workstation, with software with sophisticated rendering capabilities.