Browsing by Author "Radiology & Imaging Sciences, School of Medicine"

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    Assessing the performance of ultrasound imaging systems using images from relatively high‐density random spherical void phantoms: A simulation study
    (Wiley, 2022-02) Holland, Mark R.; Radiology & Imaging Sciences, School of Medicine
    Background The development of clinically meaningful, objective, and quantitative methods for assessing the performance of ultrasound imaging systems represents a continuing area of interest. One approach has been to image phantoms with randomly distributed spherical voids. Purpose The objectives of this study were: (1) to explore the potential of using relatively high-volume fraction random spherical void (RSV) phantoms as an approach for quantitatively assessing the performance of ultrasound imaging systems; (2) to identify potential metrics that can be used to provide quantitative assessments of images obtained from relatively high-volume fraction RSV phantoms; and (3) to demonstrate changes in the quantitative metrics that can occur as image features are degraded. Methods A series (10 each) of computer-simulated RSV phantoms with a range of RSV volume fractions (0.05, 0.15, and 0.25) were generated. To determine the number of image planes necessary to provide robust measurements, a series of consecutive planes (ranging from 1 to 150) within each type of simulated phantom were analyzed. The observed circular cross-section radii histogram distributions (representing the intersection of each plane with the local distribution of spherical voids) were compared with the theoretical histogram distribution. Simulated phantom images were produced by adding speckle and degradation of imaging system performance was modeled by averaging 1 to 9 neighboring planes to represent increasing elevation plane thicknesses. Quantification of the performance of the imaging system was determined by measuring the: (1) mean number of circular cross-sections detected per image frame; (2) mean fractional area of circular cross-sections detected per image frame; (3) agreement of observed circular cross-section radii histogram distribution with the theoretical distribution (Chi-square statistic); and (4) contrast and contrast-to-noise ratio as a function of observed circular cross-section radius. Results Results suggest that analyses of a sufficient number of image planes (providing over approximately 3000 total circular cross-sectional areas) provides excellent agreement between the observed and theoretical histogram distributions (mean Chi-square < 0.004). For the 0.15 volume fraction series of simulated RSV phantoms, using 150 image plane analyses, phantom images show decreasing mean number of circle cross-sections detected per frame (31.5 ± 0.3, 28.4 ± 0.3, 28.2 ± 0.3, 26.3 ± 0.3, and 25.3 ± 0.3); decreasing mean fractional area of circle cross-sections per frame (0.157 ± 0.002, 0.133 ± 0.001, 0.133 ± 0.001, 0.111 ± 0.001, and 0.108 ± 0.001); and a decreasing agreement with the theoretical histogram distribution of radii (Chi-square values: 0.070 ± 0.004, 0.140 ± 0.005, 0.149 ± 0.007, 0.379 ± 0.011, and 0.518 ± 0.010) for 1, 3, 5, 7, and 9 plane averages, respectively. Contrast and contrast-to-noise measurements as a function of observed circular cross-section radius also demonstrate marked changes with simulated image degradation. Conclusions Results of this simulation study suggest that analyses of images obtained from relatively high-density RSV phantoms may offer a promising approach for assessing ultrasound imaging systems. The proposed measurements appear to provide reproducible, robust, quantitative metrics that can be compared with corresponding theoretical values to provide quantifiable, objective metrics of imaging system performance.
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    Genome-wide association study identifies susceptibility loci of brain atrophy to NFIA and ST18 in Alzheimer's disease
    (Elsevier, 2021-06) Kim, Bo-Hyun; Nho, Kwangsik; Lee, Jong-Min; Alzheimer's Disease Neuroimaging Initiative; Radiology & Imaging Sciences, School of Medicine
    To identify genetic variants influencing cortical atrophy in Alzheimer's disease (AD), we performed genome-wide association studies (GWAS) of mean cortical thicknesses in 17 AD-related brain. In this study, we used neuroimaging and genetic data of 919 participants from the Alzheimer's Disease Neuroimaging Initiative cohort, which include 268 cognitively normal controls, 488 mild cognitive impairment, 163 AD individuals. We performed GWAS with 3,041,429 single nucleotide polymorphisms (SNPs) for cortical thickness. The results of GWAS indicated that rs10109716 in ST18 (ST18 C2H2C-type zinc finger transcription factor) and rs661526 in NFIA (nuclear factor I A) genes are significantly associated with mean cortical thicknesses of the left inferior frontal gyrus and left parahippocampal gyrus, respectively. The rs661526 regulates the expression levels of NFIA in the substantia nigra and frontal cortex and rs10109716 regulates the expression levels of ST18 in the thalamus. These results suggest a crucial role of identified genes for cortical atrophy and could provide further insights into the genetic basis of AD.
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    Piloting a Graduate Medical Education Point-of-Care Ultrasound Curriculum
    (Springer, 2022-07) Ferre, Robinson M.; Russell, Frances M.; Peterson, Dina; Zakeri, Bita; Herbert, Audrey; Nti, Benjamin; Goldman, Mitchell; Wilcox, James G.; Wallach, Paul M.; Radiology & Imaging Sciences, School of Medicine
    Objective As point-of-care ultrasound (POCUS) use grows, training in graduate medical education (GME) is increasingly needed. We piloted a multispecialty GME POCUS curriculum and assessed feasibility, knowledge, and comfort with performing POCUS exams. Methods Residents were selected from the following residency programs: internal medicine, family medicine, emergency medicine, and a combined internal medicine/pediatrics program. Didactics occurred through an online curriculum that consisted of five modules: physics and machine operation, cardiac, lung, soft tissue, and extended focused sonography in trauma applications. Residents completed a pre- and post-curriculum questionnaire, as well as knowledge assessments before and after each module. One-hour hands-on training sessions were held for each module. Differences between pre- and post-participation questionnaire responses were analyzed using the Wilcoxon rank sum. Results Of the 24 residents selected, 21 (86%) were post-graduate year two or three, and 16 (65%) were from the internal medicine program. Eighteen (67%) residents reported limited prior POCUS experience. All pre- to post-knowledge assessment scores increased (p<0.05). Statistically significant increases pre- to post-curriculum were found for frequency of POCUS use (p = 0.003), comfort in using POCUS for assessing for abdominal aortic aneurysm, soft tissue abscess detection, undifferentiated hypotension and dyspnea, cardiac arrest and heart failure (p<0.025); and competency in machine use, acquiring and interpreting images and incorporating POCUS into clinical practice (p<0.001). All participants felt the skills learned during this curriculum were essential to their future practice. Conclusions In this pilot, we found using a combination of online and hands-on training to be feasible, with improvement in residents' knowledge, comfort, and use of POCUS.