Restricted Regions Of Interest Research Articles

Angiography and optical coherence tomography derived shear stress: are they equivalent in my opinion?

Advances in image reconstruction using either single or multimodality imaging data provide increasingly accurate three-dimensional (3D) patient's arterial models for shear stress evaluation using computational fluid dynamics (CFD). We aim to evaluate the impacts on endothelial shear stress (ESS) derived from a simple image reconstruction using 3D-quantitative coronary angiography (3D-QCA) versus a multimodality reconstruction method using optical coherence tomography (OCT) in patients' vessels treated with bioresorbable scaffolds. Seven vessels at baseline and five-year follow-up of seven patients from a previous CFD investigation were retrospectively selected for a head-to-head comparison of angiography-derived versus OCT-derived ESS. 3D-QCA significantly underestimated the minimum stent area [MSA] (-2.38mm2) and the stent length (-1.46mm) compared to OCT-fusion method reconstructions. After carefully co-registering the region of interest for all cases with a sophisticated statistical method, the difference in MSA measurements as well as the inability of angiography to visualise the strut footprint in the lumen surface have translated to higher angiography-derived ESS than OCT-derived ESS (1.76Pa or 1.52 times for the overlapping segment). The difference in ESS widened with a more restricted region of interest (1.97Pa or 1.63 times within the scaffold segment). Angiography and OCT offer two distinctive methods of ESS calculation. Angiography-derived ESS tends to overestimate the ESS compared to OCT-derived ESS. Further investigations into ESS analysis resolution play a vital role in adopting OCT-derived ESS.

The use of broad vs restricted regions of interest in functional near-infrared spectroscopy for measuring cortical activation to auditory-only and visual-only speech

As an alternative to fMRI, functional near-infrared spectroscopy (fNIRS) is a relatively new tool for observing cortical activation. However, spatial resolution is reduced compared to fMRI and often the exact locations of fNIRS optodes and specific anatomical information is not known. The aim of this study was to explore the location and range of specific regions of interest that are sensitive to detecting cortical activation using fNIRS in response to auditory- and visual-only connected speech.Two approaches to a priori region-of-interest selection were explored. First, broad regions corresponding to the auditory cortex and occipital lobe were analysed. Next, the fNIRS Optode Location Decider (fOLD) tool was used to divide the auditory and visual regions into two subregions corresponding to distinct anatomical structures. The Auditory-A and -B regions corresponded to Heschl's gyrus and planum temporale, respectively. The Visual-A region corresponded to the superior occipital gyrus and the cuneus, and the Visual-B region corresponded to the middle occipital gyrus. The experimental stimulus consisted of a connected speech signal segmented into 12.5-sec blocks and was presented in either an auditory-only or visual-only condition.Group-level results for eight normal-hearing adult participants averaged over the broad regions of interest revealed significant auditory-evoked activation for both the left and right broad auditory regions of interest. No significant activity was observed for any other broad region of interest in response to any stimulus condition. When divided into subregions, there was a significant positive auditory-evoked response in the left and right Auditory-A regions, suggesting activation near the primary auditory cortex in response to auditory-only speech. There was a significant positive visual-evoked response in the Visual-B region, suggesting middle occipital gyrus activation in response to visual-only speech. In the Visual-A region, however, there was a significant negative visual-evoked response. This result suggests a significant decrease in oxygenated hemoglobin in the superior occipital gyrus as well as the cuneus in response to visual-only speech. Distinct response characteristics, either positive or negative, in adjacent subregions within the temporal and occipital lobes were fairly consistent on the individual level.Results suggest that temporal regions near Heschl's gyrus may be the most advantageous location in adults for identifying hemodynamic responses to complex auditory speech signals using fNIRS. In the occipital lobe, regions corresponding to the facial processing pathway may prove advantageous for measuring positive responses to visual speech using fNIRS.

Automatic cardiac cine MRI segmentation and heart disease classification

Cardiac cine magnetic resonance imaging (MRI) continues to be recognized as an established modality for non-invasive assessment of the function and structure of the cardiovascular system. Making full use of fully convolutional neural networks CNNs ability to operate pixel-wise classification, cine MRI sequences can be segmented and volumetric features of three key heart structures are computed for disease prediction. The three key heart structures are the left ventricle cavity, right ventricle cavity and the left ventricle myocardium. In this paper, we suggest an automated pipeline for both cardiac segmentation and diagnosis. The study was conducted on a dataset of 150 patients from Dijon Hospital in the context of the post-2017 Medical Image Computing and Computer Assisted Intervention MICCAI, Automated Cardiac Diagnosis Challenge (ACDC). The challenge consists in two phases: (i) a segmentation contest, where performance is evaluated on dice overlap coefficient and Hausdorff distance metrics, and a (ii) diagnosis contest for heart disease classification. For this aim, we propose the use of a deep learning based network for segmentation of the three key cardiac structures within short-axis cine MRI sequences and a classifier ensemble for heart disease classification. The deep learning segmentation network is a UNet fully convolutional neural network variant with fewer trainable parameters. The classifier ensemble consists in combining three classifiers, namely a multilayer perceptron, a random forest and a support vector machine. Before feeding the segmentation network, a preliminary step consists in localizing heart region and cropping input images to a restricted region of interest (ROI). This is achieved by a signal processing based approach and aims at reducing multi-class imbalance and computational load. We achieved nearly state of the art accuracy performances for both the segmentation and disease classification challenges. Reporting a mean dice overlap coefficient of 0.92 for the three cardiac structures segmentation, along with good limits of agreement for the various derived clinical indices, leading to an accuracy of 0.92 for the disease classification on unseen data.

Decoding the Traumatic Memory among Women with PTSD: Implications for Neurocircuitry Models of PTSD and Real-Time fMRI Neurofeedback.

Posttraumatic Stress Disorder (PTSD) is characterized by intrusive recall of the traumatic memory. While numerous studies have investigated the neural processing mechanisms engaged during trauma memory recall in PTSD, these analyses have only focused on group-level contrasts that reveal little about the predictive validity of the identified brain regions. By contrast, a multivariate pattern analysis (MVPA) approach towards identifying the neural mechanisms engaged during trauma memory recall would entail testing whether a multivariate set of brain regions is reliably predictive of (i.e., discriminates) whether an individual is engaging in trauma or non-trauma memory recall. Here, we use a MVPA approach to test 1) whether trauma memory vs neutral memory recall can be predicted reliably using a multivariate set of brain regions among women with PTSD related to assaultive violence exposure (N=16), 2) the methodological parameters (e.g., spatial smoothing, number of memory recall repetitions, etc.) that optimize classification accuracy and reproducibility of the feature weight spatial maps, and 3) the correspondence between brain regions that discriminate trauma memory recall and the brain regions predicted by neurocircuitry models of PTSD. Cross-validation classification accuracy was significantly above chance for all methodological permutations tested; mean accuracy across participants was 76% for the methodological parameters selected as optimal for both efficiency and accuracy. Classification accuracy was significantly better for a voxel-wise approach relative to voxels within restricted regions-of-interest (ROIs); classification accuracy did not differ when using PTSD-related ROIs compared to randomly generated ROIs. ROI-based analyses suggested the reliable involvement of the left hippocampus in discriminating memory recall across participants and that the contribution of the left amygdala to the decision function was dependent upon PTSD symptom severity. These results have methodological implications for real-time fMRI neurofeedback of the trauma memory in PTSD and conceptual implications for neurocircuitry models of PTSD that attempt to explain core neural processing mechanisms mediating PTSD.

WE‐C‐BRB‐06: Analyzing the Impact of Intra‐Fraction Motion: Correlation of IMRT QA Metrics with D95%

Purpose: Motion‐encoded dose distributions, taking into account intra‐fraction motion during intensity modulated radiation therapy (IMRT), can be determined both computationally and experimentally, with a number of analysis techniques available to quantify the dosimetric changes. The analysis results can provide important information regarding the clinical impact of motion and the appropriateness of a given treatment plan. This study provides a comparison of different analysis techniques performed on computationally predicted motion‐encoded dose distributions. Methods: A total of 3,768 motion‐encoded dose distributions were calculated computationally for 38 step‐and‐shoot and 38 compensator IMRT plans across 9 lung patients. The motion‐encoded dose distributions were compared to static dose distributions using four analysis techniques: 2D and 3D gamma, histogram (looking at the fraction of voxels with a dose deviation exceeding 3% of the prescription dose) and dose volume histogram (DVH) analyses. Tests were also implemented to separate failing voxels caused by either over‐dosing or under‐dosing. In addition tests were performed both globally (not taking into account the planning regions of interest) and within restricted regions of interest, such as the target volume. Results: Global analysis techniques did not accurately predict clinically relevant dosimetric changes in the target D<sub>95%</sub>. Three‐dimensional gamma and histogram analyses, localized within the target and considering only voxels experiencing decreased doses due to motion, provided the strongest correlations with changes in D<sub>95%</sub> (r,2</sup>=0.68 and r,2</sup>=0.71 respectively). A global 2D gamma analysis correlated less well with changes in D<sub>95%</sub> (r,2</sup>=0.44), and was both less specific and sensitive. Conclusions: This study suggests that any clinical decisions based solely on 2D or global measurement techniques may not provide adequate dosimetric information about the effect of motion on IMRT delivery. Care needs to be taken in determining the appropriate analysis technique and in interpreting the results in order to understand the relevant dosimetric changes caused by motion.This work was supported in part by .decimal, Inc.

The effect of large veins on spatial localization with GE BOLD at 3 T: Displacement, not blurring

We used two different methods of region of interest (ROI) definition to investigate the spatial accuracy of functional magnetic resonance imaging (fMRI) at low and high spatial resolution. The “single-condition localizer” consisted of block alternation between a target stimulus and a mean gray background. The “differential localizer” consisted of block alternation between the target stimulus and another stimulus that filled the complement of the visual field. A separate series of scans, in which the target stimulus was presented briefly with long inter-stimulus intervals, was used to measure the hemodynamic impulse response function (HIRF). As expected, the differential localizer defined more restricted ROIs that better matched the predicted cortical representation of the target stimulus. However, at low resolution (3-mm isotropic) many voxels that responded positively to the target stimulus in the differential protocol responded negatively to the target stimulus in the single-condition localizer and in the HIRF measurements. The localization errors were attributed to voxels near large veins, which were identified based on low mean intensity and high variance. At high resolution (1.2-mm isotropic), the effects of large veins were present, but affected a smaller number of voxels. Thus, the use of differential localizers does not necessarily result in a more accurate indication of the underlying neural activity. Localization errors are reduced at higher spatial resolutions and can be eliminated by identification and removal of voxels dominated by large veins.

1928: Drawing Restricted Regions of Interest Allows for Correct Identification of Stone Composition Using Helical Computed Tomography (CT)

1928: Drawing Restricted Regions of Interest Allows for Correct Identification of Stone Composition Using Helical Computed Tomography (CT)

Application of Doppler ultrasonography in congenital vascular lesions of the head and neck.

To evaluate the value of Doppler ultrasonography in the assessment of congenital vascular lesions of the maxillofacial region. 27 new patients with 36 congenital vascular lesions in the maxillofacial region as well as 10 patients previously treated with cryotherapy underwent ultrasonography (US) with a 6.0-10.0 MHz broadband linear transducer (reference Doppler frequency 7.5 MHz). Initial grey-scale US was followed by Color Doppler, Power Doppler and spectral Doppler studies. The presence or absence of flow was noted. In areas of high vascularity the number of vessels within a 1 cm(2) restricted region of interest were increased by spectral Doppler. US allowed differentiation of seven hemangiomas from other congenital vascular lesions and thus appropriate treatment of patients. Low flow vessels were demonstrated within the scars of five lesions previously treated with cryotherapy, requiring further intervention. Doppler US is a widely available, non-invasive and relatively inexpensive technique which can be used to characterize the flow of head and neck vascular anomalies and thus differentiate hemangiomas from other vascular malformations.

Implications of beta energy and quench level for alpha/beta liquid scintillation spectrometry calibration

Alpha/beta separation is achieved by the use of pulse shape discrimination (PSD), calibrated by quantifying event misclassification at any given setting for pure α and β emitters. Previous studies have shown that the degree of misclassification is affected by quenching, but with no attempt made to understand the causes for this phenomenon. This study examines the potential effects of β energy and quench on PSD calibration. PSD was shown to be energy dependent, with misclassification increasing with β event energy. Therefore, PSD calibration requires the use of a β emitter with the same energy distribution as is present in the sample, or a restricted region of interest should be employed. For gross α/gross β analysis of samples containing unknown β emitters, a stepwise calibration procedure is proposed for both PSD and efficiency calibration. Quenching by carbon tetrachloride, nitromethane and 9 M hydrochloric acid was shown to affect PSD by suppression of the delayed component of the scintillation pulse, although to variable extents, and therefore having a range of effects on misclassification. Acetone quenching had little impact on PSD. Standard quench calibration procedures using either carbon tetrachloride or nitromethane are inappropriate for applications utilising α/β separation by PSD. Instead, a quench calibration procedure based on overspiking samples encompassing a range of quench conditions is recommended. The influence of oxygen quenching on PSD was investigated through purging samples with either oxygen or nitrogen. PSD was found to be unaffected by the small amounts of oxygen normally dissolved in the diisopropylnaphthalene based cocktail used in this study.