High Spatial Resolution Acquisition Research Articles

Impact of the confluence of cardiac motion and high spatial resolution on performance of ECG-gated imaging with an investigational photon-counting CT system: A phantom study

PurposePhoton-counting CT (PCCT) has higher spatial resolution that conventional EID CT which improves imaging of stationary coronary plaques and stents.. In this work, we evaluated the relationship between higher spatial resolution and motion acquisition on an investigational PCCT system. MethodsAn investigational photon-counting CT scanner (Siemens CounT) with ECG gating was used to image a coronary tree phantom with models of healthy, stenotic, and stented arteries using a motion simulator. Images were acquired with matched clinical parameters at rest and 60 beats per minute. An additional set of high dose stationary images were averaged to generate a motion-free, reduced noise reference. Scans were completed at standard (0.5 mm2) and high-resolution (0.25 mm2). Motion images were reconstructed at multiple phases. Regions of interest were drawn around vessels and segmented. Percentage difference from the reference standard was evaluated for vessel diameter and circularity. Mutual information between the reference and stationary and motion datasets was used as a measure of volumetric similarity. ResultsThe stenotic vessel showed the most variation from the reference when compared to healthy or stented vessels. Compared to standard resolution, high-resolution images had lower bias for diameter (-0.012 ± 0.19% vs −0.052 ± 0.14%) and lower variability for circularity (-0.13 ± 0.138% vs −0.12 ± 0.144%). Both differences were found to be statistically significant. High-resolution images had a slightly lower mutual information (1.28) than standard resolution (1.31). ConclusionThe higher spatial resolution enabled by photon-counting CT can be harnessed for cardiac imaging as the benefits of high spatial resolution acquisitions remain relevant in the presence of motion.

First measurements of a scintillator-based fast-ion loss detector in reversed Ip/Bt at the ASDEX Upgrade tokamak

Fast-α losses in future fusion power plants are expected to follow the co- and counter-current directions due to the isotropy of the fusion reaction. At the ASDEX Upgrade tokamak, the co-current direction (achieved with positive plasma current and negative toroidal magnetic field) has been extensively studied thanks to an array of five fast-ion loss detectors (FILD). A new fast-ion loss detector compatible with reversed Ip/Bt (negative plasma current and positive magnetic toroidal field, defining positive as counter-clockwise when the machine is viewed from the top), namely RFILD, has been designed and commissioned to study the behaviour of counter-current fast-ion losses and to expand our knowledge on QH-mode, I-mode, and the L-H transition. The detector is a modified version of the midplane manipulator fast-ion loss detector that features a new probe head orientation and collimator geometry, optimised using the FILDSIM code. A fast CMOS camera is used as a high spatial resolution acquisition system, while an array of photomultipliers (up to 1 MHz) serves as a fast channel.First measurements have been taken in I-mode, QH-mode, L-mode and H-mode with core densities ranging between 4·1019 and 9·1019 m−3, IP between -0.8 and -0.6 MA and Bt of 2.5 T approximately. NBI fast-ion losses were observed for the first time in reversed Ip/Bt, producing high pitch (60 – 80°) losses. ICRH losses in H-minority heating configuration have also been observed in I-mode experiments. These losses correspond to the outer leg of banana particle trajectories. An upgraded double collimator detector design is also presented, that will increase the measurable particle range in future experimental campaigns (co- and counter-current particles simultaneously). Thus, we expand our understanding on the mechanisms behind fast-ion losses at the ASDEX Upgrade tokamak in the reversed Ip/Bt configuration.

Quantitative Assessment of Low-Dose Photodynamic Therapy Effects on Diabetic Wound Healing Using Raman Spectroscopy

One of challenges that faces diabetes is the wound healing process. The delayed diabetic wound healing is caused by a complicated molecular mechanism involving numerous physiological variables. Low-dose photodynamic therapy (LDPDT) provides excellent results in rejuvenation and wound healing. In this study, the LDPDT effect on diabetic wounds in mice was studied using two photosensitizers, 5-aminolevulinic acid and methylene blue, and two laser dose expositions of 1 J/cm2 and 4 J/cm2 by Raman spectroscopy (RS). The latter was used as a noninvasive method, providing specific information about tissue state based on the fundamental vibrational modes of its molecular components. RS allows high spatial resolution acquisition of biochemical and structural information through the generation of point spectra or spectral images. An approach to in vivo quantitative assessment of diabetic wound healing state was developed. This approach is based on an application of the principal component analysis combined with the Mahalanobis metrics to skin Raman spectra, in particular, intensities of the amide I and CH2 bands.

Guided Deep Generative Model-Based Spatial Regularization for Multiband Imaging Inverse Problems.

When adopting a model-based formulation, solving inverse problems encountered in multiband imaging requires to define spatial and spectral regularizations. In most of the works of the literature, spectral information is extracted from the observations directly to derive data-driven spectral priors. Conversely, the choice of the spatial regularization often boils down to the use of conventional penalizations (e.g., total variation) promoting expected features of the reconstructed image (e.g., piece-wise constant). In this work, we propose a generic framework able to capitalize on an auxiliary acquisition of high spatial resolution to derive tailored data-driven spatial regularizations. This approach leverages on the ability of deep learning to extract high level features. More precisely, the regularization is conceived as a deep generative network able to encode spatial semantic features contained in this auxiliary image of high spatial resolution. To illustrate the versatility of this approach, it is instantiated to conduct two particular tasks, namely multiband image fusion and multiband image inpainting. Experimental results obtained on these two tasks demonstrate the benefit of this class of informed regularizations when compared to more conventional ones.

Deep Learning Approach for Dynamic Sampling for Multichannel Mass Spectrometry Imaging.

Mass Spectrometry Imaging (MSI), using traditional rectilinear scanning, takes hours to days for high spatial resolution acquisitions. Given that most pixels within a sample's field of view are often neither relevant to underlying biological structures nor chemically informative, MSI presents as a prime candidate for integration with sparse and dynamic sampling algorithms. During a scan, stochastic models determine which locations probabilistically contain information critical to the generation of low-error reconstructions. Decreasing the number of required physical measurements thereby minimizes overall acquisition times. A Deep Learning Approach for Dynamic Sampling (DLADS), utilizing a Convolutional Neural Network (CNN) and encapsulating molecular mass intensity distributions within a third dimension, demonstrates a simulated 70% throughput improvement for Nanospray Desorption Electrospray Ionization (nano-DESI) MSI tissues. Evaluations are conducted between DLADS, a Supervised Learning Approach for Dynamic Sampling, with Least-Squares regression (SLADS-LS), and a Multi-Layer Perceptron (MLP) network (SLADS-Net). When compared with SLADS-LS, limited to a single channel, as well as multichannel SLADS-LS and SLADS-Net, DLADS respectively improves regression performance by 36.7%, 7.0%, and 6.2%, resulting in gains to reconstruction quality of 6.0%, 2.1%, and 3.4% for acquisition of targeted .

Ultra-high resolution, 3-dimensional magnetic resonance imaging of the atherosclerotic vessel wall at clinical 7T.

Accurate quantification and characterization of atherosclerotic plaques with MRI requires high spatial resolution acquisitions with excellent image quality. The intrinsically better signal-to-noise ratio (SNR) at high-field clinical 7T compared to the widely employed lower field strengths of 1.5 and 3T may yield significant improvements to vascular MRI. However, 7T atherosclerosis imaging also presents specific challenges, related to local transmit coils and B1 field inhomogeneities, which may overshadow these theoretical gains. We present the development and evaluation of 3D, black-blood, ultra-high resolution vascular MRI on clinical high-field 7T in comparison lower-field 3T. These protocols were applied for in vivo imaging of atherosclerotic rabbits, which are often used for development, testing, and validation of translatable cardiovascular MR protocols. Eight atherosclerotic New Zealand White rabbits were imaged on clinical 7T and 3T MRI scanners using 3D, isotropic, high (0.63 mm3) and ultra-high (0.43 mm3) spatial resolution, black-blood MR sequences with extensive spatial coverage. Following imaging, rabbits were sacrificed for validation using fluorescence imaging and histology. Image quality parameters such as SNR and contrast-to-noise ratio (CNR), as well as morphological and functional plaque measurements (plaque area and permeability) were evaluated at both field strengths. Using the same or comparable imaging parameters, SNR and CNR were in general higher at 7T compared to 3T, with a median (interquartiles) SNR gain of +40.3 (35.3–80.1)%, and a median CNR gain of +68.1 (38.5–95.2)%. Morphological and functional parameters, such as vessel wall area and permeability, were reliably acquired at 7T and correlated significantly with corresponding, widely validated 3T vessel wall MRI measurements. In conclusion, we successfully developed 3D, black-blood, ultra-high spatial resolution vessel wall MRI protocols on a 7T clinical scanner. 7T imaging was in general superior to 3T with respect to image quality, and comparable in terms of plaque area and permeability measurements.

Association Between Body Mass Index (BMI) And Cardiac Chamber Size As Measured By A Novel Artificial Intelligence (AI) System On Cardiac Computed Tomography Angiography (CCTA) Images

Introduction: Contrast-enhanced cardiac computed tomography (CCTA) with its ability to perform 3D, high spatial resolution acquisition on a range of anatomic structures, has been established as an integral tool in the assessment of cardiovascular disease. Attempts to quantify cardiac structures have been hampered by time-consuming, tedious manual segmentation methods. We examined the effect of body mass index (BMI) and on cardiac chamber size in a real-world referral population using a novel artificial intelligence system for fully automated CCTA image segmentation.

Ontology-Guided Image Interpretation for GEOBIA of High Spatial Resolution Remote Sense Imagery: A Coastal Area Case Study

Image interpretation is a major topic in the remote sensing community. With the increasing acquisition of high spatial resolution (HSR) remotely sensed images, incorporating geographic object-based image analysis (GEOBIA) is becoming an important sub-discipline for improving remote sensing applications. The idea of integrating the human ability to understand images inspires research related to introducing expert knowledge into image object–based interpretation. The relevant work involved three parts: (1) identification and formalization of domain knowledge; (2) image segmentation and feature extraction; and (3) matching image objects with geographic concepts. This paper presents a novel way that combines multi-scaled segmented image objects with geographic concepts to express context in an ontology-guided image interpretation. Spectral features and geometric features of a single object are extracted after segmentation and topological relationships are also used in the interpretation. Web ontology language–query language (OWL-QL) formalize domain knowledge. Then the interpretation matching procedure is implemented by the OWL-QL query-answering. Compared with a supervised classification, which does not consider context, the proposed method validates two HSR images of coastal areas in China. Both the number of interpreted classes increased (19 classes over 10 classes in Case 1 and 12 classes over seven in Case 2), and the overall accuracy improved (0.77 over 0.55 in Case 1 and 0.86 over 0.65 in Case 2). The additional context of the image objects improved accuracy during image classification. The proposed approach shows the pivotal role of ontology for knowledge-guided interpretation.

Ultrafast Bilateral DCE-MRI of the Breast with Conventional Fourier Sampling: Preliminary Evaluation of Semi-quantitative Analysis

The study aimed to evaluate the feasibility and advantages of a combined high temporal and high spatial resolution protocol for dynamic contrast-enhanced magnetic resonance imaging of the breast. Twenty-three patients with enhancing lesions were imaged at 3T. The acquisition protocol consisted of a series of bilateral, fat-suppressed "ultrafast" acquisitions, with 6.9- to 9.9-second temporal resolution for the first minute following contrast injection, followed by four high spatial resolution acquisitions with 60- to 79.5-second temporal resolution. All images were acquired with standard uniform Fourier sampling. A filtering method was developed to reduce noise and detect significant enhancement in the high temporal resolution images. Time of arrival (TOA) was defined as the time at which each voxel first satisfied all the filter conditions, relative to the time of initial arterial enhancement. Ultrafast images improved visualization of the vasculature feeding and draining lesions. A small percentage of the entire field of view (<6%) enhanced significantly in the 30 seconds following contrast injection. Lesion conspicuity was highest in early ultrafast images, especially in cases with marked parenchymal enhancement. Although the sample size was relatively small, the average TOA for malignant lesions was significantly shorter than the TOA for benign lesions. Significant differences were also measured in other parameters descriptive of early contrast media uptake kinetics (P < 0.05). Ultrafast imaging in the first minute of dynamic contrast-enhanced magnetic resonance imaging of the breast has the potential to add valuable information on early contrast dynamics. Ultrafast imaging could allow radiologists to confidently identify lesions in the presence of marked background parenchymal enhancement.

Fast Abdominal Magnetic Resonance Imaging.

Abdominal imaging is the driving force that necessitates the development of numerous techniques for accelerated image acquisition in magnetic resonance imaging (MRI). Today, numerous techniques are available that enablerapid, high spatial resolution acquisition forboth T1 and T2 weighted images. Thesetechniques open new opportunities in the detection and classification of numerous pathologies in the abdomen. However, there is still ongoing progress in the development of fast and ultrafast sequences and promising techniques are currently close to clinical application. With these 4D-technologies, MRI is becoming the central imaging modality for dynamic, motion-compensated imaging of the parenchymal abdominal organs such as liver, pancreas and kidney. • Fast imaging techniques are especially valuable in the upper abdomen, as this region is particularly affected by respiratory motion.• Parallel imaging and k-space-based acceleration techniques are the basic components of fast 3 D sequences.• By further accelerating 3 D imaging with high spatial resolution, 4 D techniques become available. Citation Format: • Budjan J., Schoenberg S. O., Riffel P. Fast Abdominal Magnetic Resonance Imaging. Fortschr Röntgenstr 2016; 188: 551 - 558.

Comprehensive MRA of the lower limbs including high-resolution extended-phase infra-inguinal imaging with gadobenate dimeglumine: Initial experience with inter-individual comparison to the blood-pool contrast agent gadofosveset trisodium

To compare extended-phase imaging using an extracellular space contrast agent, gadobenate dimeglumine, to imaging with a blood-pool contrast agent, gadofosveset, for magnetic resonance angiography. A lower-limb magnetic resonance angiography (MRA) protocol (dynamic crural, three-station bolus chase, and infra-inguinal high resolution) designed for blood-pool agent imaging was adapted for use with the extracellular agent, gadobenate dimeglumine, primarily by using a triphasic injection protocol. Ten patients scanned with gadofosveset were compared to 10 patients scanned with gadobenate. The dynamic, bolus chase, and high-resolution images were scored for quality on a Likert scale (from 1-5). Signal- and contrast-to-noise ratios were analysed, and Mann-Whitney U statistical analysis performed. There was no significant difference for the dynamic imaging or the aorto-iliac station of the bolus chase. Infra-inguinal bolus chase images were higher quality (p < 0.05 Mann-Whitney U test) with gadobenate. Signal analysis confirmed lower signal and contrast for venous imaging on the high spatial resolution acquisitions with gadobenate; however, this allowed improved arterial conspicuity. Extended-phase imaging using an extracellular space contrast agent is feasible and provides image quality to equal imaging with a blood-pool contrast agent.

High resolution navigated three‐dimensional T1‐weighted hepatobiliary MRI using gadoxetic acid optimized for 1.5 tesla

To determine optimal delay times and flip angles for T1-weighted hepatobiliary imaging at 1.5 Tesla (T) with gadoxetic acid and to demonstrate the feasibility of using a high-resolution navigated optimized T1-weighted pulse sequence to evaluate biliary disease. Eight healthy volunteers were scanned at 1.5T using a T1-weighted three-dimensional (3D)-SPGR pulse sequence following the administration of 0.05 mmol/kg of gadoxetic acid. Navigator-gating enabled acquisition of high spatial resolution (1.2 × 1.4 × 1.8 mm(3) , interpolated to 0.7 × 0.7 × 0.9 mm(3) ) images in approximately 5 min of free-breathing. Multiple breath-held acquisitions were performed at flip angles between 15° and 45° to optimize T1 weighting. To evaluate the performance of this optimized sequence in the setting of biliary disease, the image quality and biliary excretion of 51 consecutive clinical scans performed to assess primary sclerosing cholangitis (PSC) were evaluated. Optimal hepatobiliary imaging occurs at 15-25 min, using a 40° flip angle. The image quality and visualization of biliary excretion in the PSC scans were excellent, despite the decreased liver function in some patients. Visualization of reduced excretion often provided diagnostic information that was unavailable by conventional magnetic resonance cholangiopancreatography (MRCP). High-resolution navigated 3D-SPGR hepatobiliary imaging using gadoxetic acid and optimized scan parameters is technically feasible and can be clinically useful, even in patients with decreased hepatobiliary function.

Design and image-quality performance of high resolution CMOS-based X-ray imaging detectors for digital mammography

In digital X-ray imaging systems, X-ray imaging detectors based on scintillating screens with electronic devices such as charge-coupled devices (CCDs), thin-film transistors (TFT), complementary metal oxide semiconductor (CMOS) flat panel imagers have been introduced for general radiography, dental, mammography and non-destructive testing (NDT) applications. Recently, a large-area CMOS active-pixel sensor (APS) in combination with scintillation films has been widely used in a variety of digital X-ray imaging applications. We employed a scintillator-based CMOS APS image sensor for high-resolution mammography. In this work, both powder-type Gd2O2S:Tb and a columnar structured CsI:Tl scintillation screens with various thicknesses were fabricated and used as materials to convert X-ray into visible light. These scintillating screens were directly coupled to a CMOS flat panel imager with a 25 × 50 mm2 active area and a 48 μm pixel pitch for high spatial resolution acquisition. We used a W/Al mammographic X-ray source with a 30 kVp energy condition. The imaging characterization of the X-ray detector was measured and analyzed in terms of linearity in incident X-ray dose, modulation transfer function (MTF), noise-power spectrum (NPS) and detective quantum efficiency (DQE).

Po-topic IV-08: 4-dimensional CT imaging of free breathing motion

Modeling of breathing motion is important for the definition of conformal therapy radiation portal boundaries and will be critical to the development of intensity modulated radiation therapy of the thorax and upper abdomen. Development of motion models based on free breathing have been hampered by a lack of volumetric, high-resolution, free-breathing gated image data. We have developed a method for the acquisition of high spatial resolution, tidal volume gated computed tomography (CT) scans acquired during free breathing. A multislice CT scanner is used in ciné mode, where multiple CT scans are acquired without couch motion. After acquisition of a user-specified number of scans (15 scans using a 4-slice scanner in our current studies), the couch is advanced to the next abutting position and another set is acquired. This process is repeated until the entire region of interest is scanned. The patient undergoes quantitative spirometry monitoring during the scanning. The time stamps on the CT scans are used with the spirometry data to determine the patient’s tidal volume during scan acquisition. 3D CT scans are reconstructed for user-specified free breathing tidal volumes by selecting the CT scans at each couch position that were acquired at tidal volumes closest to the desired reconstruction volume. Movie loops can be created by reconstructing a sequence of tidal volumes. Because a finite number of scans are acquired, reconstruction is imperfect. Nevertheless, the desired tidal volume differs only slightly from the closest scanned volume. To date, three patients have been scanned. The breathing tidal volume ranged from 400 mL–600 mL and the standard deviation between desired and scanned tidal volumes ranged from 22 mL-33 mL. Comparisons between the total lung volume change of the reconstructed CT scan datasets and spirometry-measured tidal volume showed excellent agreement. Reconstructed sagittal and coronal images showed remarkably few motion artifacts, even in mid-inspiration tidal volumes. Motion movies of tumors showed nonrigid motion, with tumors deflecting, rotating, and stretching during breathing. This indicates that accurate definition of tumor motion will require nonrigid deformation modeling. Preliminary motion models were developed by manually localizing bronchial branches for a sequence of tidal volume-reconstructed CT scans. First- and second-order polynomial fits of the positions as a function of tidal volume were conducted and compared against the directly measured positions. The typical standard deviation of the fit and measured positions were 2.0 and 1.0 mm for first and second-order fits, respectively. Sources of these differences are the finite tidal volume resolution based on the 15-scan acquisitions, and errors in spirometry drift correction. In conclusion, we have developed a feasible and accurate method for gating computed CT scans to user-specified tidal volumes to construct 3D imaging datasets that reflect lung motion during free breathing. Future projects include automation of the deformable image registration process and IMRT dose calculations in the presence of breathing motion.

Magnetic resonance imaging of focal articular cartilage lesions.

Lesions of the articular cartilage now are recognized as a common, often treatable source of joint disability. Magnetic resonance imaging (MRI) of articular cartilage is a sensitive, noninvasive method for the detection of focal articular cartilage lesions. Advancement in imaging technology now allows for high spatial resolution acquisitions that are able to identify most cartilage lesions, and these acquisitions can be incorporated into everyday clinical imaging protocols. Thus, screening for cartilage abnormalities can be accomplished, along with routine evaluation for ligament and meniscal abnormalities. Familiarity with the appearances of normal cartilage and the full spectrum of cartilage lesions will aid in specific diagnoses. Grading and sizing of cartilage lesions and any underlying bony abnormalities on MRI can help the surgeon in treatment planning; however, some significant cartilage lesions can be difficult to identify and grade by MRI.

Improved spectral quality for 3D MR spectroscopic imaging using a high spatial resolution acquisition strategy

Spectral quality in 1H MR spectroscopic imaging (MRSI) of the brain is often significantly degraded in regions subject to local magnetic susceptibility variations, which results in broadened and distorted spectral lineshapes. In this report, a modified acquisition strategy for volumetric echo-planar spectroscopic imaging (3D EPSI) is presented that extends the region of the brain that can be observed. The data are sampled at higher spatial resolution, then corrected for local B 0 shifts and reconstructed such that the final spatial resolution matches that of 3D EPSI data acquired with the conventional lower spatial resolution. Comparison of in vivo data obtained at 1.5 T with these two acquisition schemes shows that the high spatial resolution acquisition provides considerable reduction of spectral linewidths in many problematic brain regions, though with a reduction in signal-to-noise ratio by a factor of approximately 1.4 to 1.6 for the matrix sizes used in this study. However, the effect of the increased noise was largely offset by the improved spectral quality, leading to an overall improvement of the metabolite image quality obtained using automated spectral analysis.

MOMS-02/D2: First results and future applications

Abstract The Modular Opto-electronic Multi-spectral Stereo Scanner MOMS-02 experimental data acquired during the German Spacelab D2 mission will be used for a broad range of geoscientific objectives. The simultaneous acquisition of high spatial resolution, multi-spectral and stereo scenic data enables a real combination of thematic and topographic information, thus considerably improving the verification and interpretation of dynamic changes of the Earth's surface by means of remote sensing. This paper gives a first assessment of the MOMS-02/D2 mission, the data quality and an overview on the planned methodological and application-oriented investigations for various test sites. On the basis of a few examples the possibilities of this system for future thematic applications is shown.