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McCollough effect

A Ferrero, B Chen, A Huang, J Montoya, L Yu, C McCollough
PURPOSE: In order to investigate novel methods to more accurately estimate the mineral composition of kidney stones using dual energy CT, it is desirable to be able to combine digital stones of known composition with actual phantom and patient scan data. In this work, we developed and validated a method to insert digital kidney stones into projection data acquired on a dual-source, dual-energy CT system. METHODS: Attenuation properties of stones of different mineral composition were computed using tabulated mass attenuation coefficients, the chemical formula for each stone type, and the effective beam energy at each evaluated tube potential...
June 2016: Medical Physics
G Michalak, A Halaweish, B Krauss, J Fletcher, C McCollough
PURPOSE: Dual energy (DE) CT can be used to characterize tissue composition. One application of DE CT is to measure electron density (ED, rho) and atomic number (Z) for use in radiation therapy treatment planning. This work evaluated the accuracy and stability of ED estimation as patient size varied for both single-energy (SE) and DE CT. METHODS: An ED phantom (CIRS) and four torso-shaped water tanks (lateral widths 15, 25, 35 and 45 cm) containing 8 tissue-simulating cylinders of known ED were scanned on a dual-source CT system (Siemens Somatom Force) in SE (120 kV) and DE (90/150Sn) modes...
June 2016: Medical Physics
Shuai Leng, Zhicong Yu, Ahmed Halaweish, Steffen Kappler, Katharina Hahn, Andre Henning, Zhoubo Li, John Lane, David L Levin, Steven Jorgensen, Erik Ritman, Cynthia McCollough
An ultrahigh-resolution (UHR) data collection mode was enabled on a whole-body, research photon counting detector (PCD) computed tomography system. In this mode, 64 rows of [Formula: see text] detector pixels were used, which corresponded to a pixel size of [Formula: see text] at the isocenter. Spatial resolution and image noise were quantitatively assessed for the UHR PCD scan mode, as well as for a commercially available UHR scan mode that uses an energy-integrating detector (EID) and a set of comb filters to decrease the effective detector size...
October 2016: Journal of Medical Imaging
Shuai Leng, Naoki Takahashi, Daniel Gomez Cardona, Kazuhiro Kitajima, Brian McCollough, Zhoubo Li, Akira Kawashima, Bradley C Leibovich, Cynthia H McCollough
PURPOSE: The aim of this study was to assess the effect of denoising on objective heterogeneity scores and its diagnostic capability for the diagnosis of angiomyolipoma (AML) and renal cell carcinoma (RCC). MATERIALS AND METHODS: A total of 158 resected renal masses ≤4 cm [98 clear cell (cc) RCCs, 36 papillary (pap)-RCCs, and 24 AMLs] from 139 patients were evaluated. A representative contrast-enhanced computed tomography (CT) image for each mass was selected by a genitourinary radiologist...
December 26, 2016: Abdominal Radiology
Steven M Jorgensen, Andrew J Vercnocke, David S Rundle, Philip H Butler, Cynthia H McCollough, Erik L Ritman
We assessed the performance of a cadmium zinc telluride (CZT)-based Medipix3RX x-ray detector as a candidate for micro-computed tomography (micro-CT) imaging. This technology was developed at CERN for the Large Hadron Collider. It features an array of 128 by 128, 110 micrometer square pixels, each with eight simultaneous threshold counters, five of which utilize real-time charge summing, significantly reducing the charge sharing between contiguous pixels. Pixel response curves were created by imaging a range of x-ray intensities by varying x-ray tube current and by varying the exposure time with fixed x-ray current...
August 28, 2016: Proceedings of SPIE
Maria Z Alfaradhi, Laura C Kusinski, Denise S Fernandez-Twinn, Lucas C Pantaleão, Sarah K Carr, David Ferland-McCollough, Giles S H Yeo, Martin Bushell, Susan E Ozanne
Obesity during pregnancy has a long-term effect on the health of the offspring including risk of developing the metabolic syndrome. Using a mouse model of maternal diet-induced obesity, we employed a genome-wide approach to investigate the microRNA (miRNA) and miRNA transcription profile in adipose tissue to understand mechanisms through which this occurs. Male offspring of diet-induced obese mothers, fed a control diet from weaning, showed no differences in body weight or adiposity at 8 weeks of age. However, offspring from the obese dams had up-regulated cytokine (Tnfα; P < ...
November 2016: Endocrinology
Zhicong Yu, Shuai Leng, Zhoubo Li, Ahmed F Halaweish, Steffen Kappler, Erik L Ritman, Cynthia H McCollough
PURPOSE: A research photon-counting computed tomography (CT) system that consists of an energy-integrating detector (EID) and a photon-counting detector (PCD) was installed in our laboratory. The scanning fields of view of the EID and PCD at the isocenter are 500 and 275 mm, respectively. When objects are larger than the PCD scanning field of view, a data-completion scan (DCS) using the EID subsystem is needed to avoid truncation artifacts in PCD images. The goals of this work were to (1) find the impact of a DCS on noise of PCD images and (2) determine the lowest possible dose for a DCS such that truncation artifacts are negligible in PCD images...
July 2016: Journal of Computer Assisted Tomography
Zhicong Yu, Shuai Leng, Steven M Jorgensen, Zhoubo Li, Ralf Gutjahr, Baiyu Chen, Ahmed F Halaweish, Steffen Kappler, Lifeng Yu, Erik L Ritman, Cynthia H McCollough
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...
February 21, 2016: Physics in Medicine and Biology
Baiyu Chen, Shuai Leng, Lifeng Yu, Zhicong Yu, Chi Ma, Cynthia McCollough
PURPOSE: To perform task-based image quality assessment in CT, it is desirable to have a large number of realistic patient images with known diagnostic truth. One effective way of achieving this objective is to create hybrid images that combine patient images with inserted lesions. Because conventional hybrid images generated in the image domain fails to reflect the impact of scan and reconstruction parameters on lesion appearance, this study explored a projection-domain approach. METHODS: Lesions were segmented from patient images and forward projected to acquire lesion projections...
December 2015: Medical Physics
Joshua Grimes, Xinhui Duan, Lifeng Yu, Ahmed F Halaweish, Nicole Haag, Shuai Leng, Cynthia McCollough
PURPOSE: The objective of this work was to investigate focal spot blooming effects on the spatial resolution of CT images and to evaluate an x-ray tube that uses dynamic focal spot control for minimizing focal spot blooming. METHODS: The influence of increasing tube current at a fixed tube potential of 80 kV on high-contrast spatial resolution of seven different CT scanner models (scanners A-G), including one scanner that uses dynamic focal spot control to reduce focal spot blooming (scanner A), was evaluated...
October 2015: Medical Physics
Barbara F M Marino, Anna M Borghi, Luca Gemmi, Cristina Cacciari, Lucia Riggio
We investigated the conceptual processing of nouns referring to objects characterized by a highly typical color and orientation. We used a go/no-go task in which we asked participants to categorize each noun as referring or not to natural entities (e.g., animals) after a selective adaptation of color-edge neurons in the posterior LV4 region of the visual cortex was induced by means of a McCollough effect procedure. This manipulation affected categorization: the green-vertical adaptation led to slower responses than the green-horizontal adaptation, regardless of the specific color and orientation of the to-be-categorized noun...
2015: Behavioral Sciences
Mingliang Qu, Lifeng Yu, Daniel Gomez Cardona, Yu Liu, Xinhui Duan, Songtao Ai, Shuai Leng, Maria Shiung, Cynthia H McCollough
OBJECTIVE: The purpose of this article is to assess the effect of radiation dose reduction in dual-energy CT (DECT) on the performance of renal stone characterization using a patient cohort. MATERIALS AND METHODS: CT data from 39 unenhanced DECT examinations performed for stone characterization were retrospectively analyzed in this study. Reduced-dose images were simulated at 75%, 50%, and 25% of the routine dose using a previously validated noise-insertion algorithm...
August 2015: AJR. American Journal of Roentgenology
Baiyu Chen, Zhicong Yu, Shuai Leng, Lifeng Yu, Cynthia McCollough
To perform task-based image quality assessment in CT, it is desirable to have a large number of realistic patient images with known diagnostic truth. One effective way to achieve this objective is to create hybrid images that combine patient images with simulated lesions. Because conventional hybrid images generated in the image-domain fails to reflect the impact of scan and reconstruction parameters on lesion appearance, this study explored a projection-domain approach. Liver lesion models were forward projected according to the geometry of a commercial CT scanner to acquire lesion projections...
February 21, 2015: Proceedings of SPIE
K McMillan, M Bostani, C McCollough, M McNitt-Gray
PURPOSE: Most patient models used in Monte Carlo-based estimates of CT dose, including computational phantoms, do not have tube current modulation (TCM) data associated with them. While not a problem for fixed tube current simulations, this is a limitation when modeling the effects of TCM. Therefore, the purpose of this work was to develop and validate methods to estimate TCM schemes for any voxelized patient model. METHODS: For 10 patients who received clinically-indicated chest (n=5) and abdomen/pelvis (n=5) scans on a Siemens CT scanner, both CT localizer radiograph ("topogram") and image data were collected...
June 2015: Medical Physics
Christopher P Favazza, Lifeng Yu, Shuai Leng, James M Kofler, Cynthia H McCollough
OBJECTIVE: To compare computed tomography dose and noise arising from use of an automatic exposure control (AEC) system designed to maintain constant image noise as patient size varies with clinically accepted technique charts and AEC systems designed to vary image noise. MATERIALS AND METHODS: A model was developed to describe tube current modulation as a function of patient thickness. Relative dose and noise values were calculated as patient width varied for AEC settings designed to yield constant or variable noise levels and were compared to empirically derived values used by our clinical practice...
May 2015: Journal of Computer Assisted Tomography
Shuai Leng, Maria Shiung, Xinhui Duan, Lifeng Yu, Yi Zhang, Cynthia H McCollough
PURPOSE: To develop software to automatically calculate size-specific dose estimates (SSDEs) and to assess the effect of variations in water-equivalent diameter (Dw) along the z-axis on SSDE for computed tomographic (CT) examinations of the torso. MATERIALS AND METHODS: In this institutional review board-approved, HIPAA-compliant, retrospective study, a software program was used to calculate Dw at each image position in 102 consecutive CT examinations of the combined chest, abdomen, and pelvis...
July 2015: Radiology
S Gabriel, L J Eckel, D R DeLone, K N Krecke, P H Luetmer, C H McCollough, J G Fletcher, L Yu
BACKGROUND AND PURPOSE: CT is a ubiquitous, efficient, and cost-effective method to evaluate pediatric ventricular size, particularly in patients with CSF shunt diversion who often need emergent imaging. We therefore sought to determine the minimum dose output or CT dose index required to produce clinically acceptable examinations. MATERIALS AND METHODS: Using a validated noise insertion method and CT projection data from 22 patients, standard pediatric head CT images were reconstructed with weighted filtered back-projection and sinogram-affirmed iterative reconstruction corresponding to routine, 25%, and 10% dose...
December 2014: AJNR. American Journal of Neuroradiology
S E Lea, D C Earle, C M Ryan
Eight pigeons were trained on a conditional discrimination using red and green saturated and desaturated fields, and red and green saturated and desaturated vertical and horizontal black-on-colour gratings. The pigeons learned to discriminate the stimuli on the basis of colour, to a high level of accuracy, regardless of saturation or the presence of gratings. The pigeons were then repeatedly exposed to stimuli in which colour and grating orientation were correlated, following which they were tested for the presence of the McCollough orientation-contingent colour after-effect, using black-on-white vertical and horizontal gratings...
August 1999: Behavioural Processes
Yi Zhang, Shuai Leng, Lifeng Yu, Rickey E Carter, Cynthia H McCollough
Although physical metrics can objectively characterize computed tomography (CT) image quality, quantitative approaches to predict human observer performance are more accurate and clinically relevant. This study compared a modified channelized Hotelling model observer (CHO) with human observers in a shape discrimination task. Eight lesion-mimicking rods (two contrasts, two sizes and two shapes) were inserted into a 35 × 26 cm(2) torso-shaped water phantom and scanned 100 times on a 128-slice CT scanner at five dose levels...
July 7, 2014: Physics in Medicine and Biology
Denise S Fernandez-Twinn, Maria Z Alfaradhi, Malgorzata S Martin-Gronert, Daniella E Duque-Guimaraes, Ana Piekarz, David Ferland-McCollough, Martin Bushell, Susan E Ozanne
We determined the effects of maternal diet-induced obesity on offspring adipose tissue insulin signalling and miRNA expression in the aetiology of insulin resistance in later life. Although body composition and glucose tolerance of 8-week-old male offspring of obese dams were not dysregulated, serum insulin was significantly (p<0.05) elevated. Key insulin signalling proteins in adipose tissue were down-regulated, including the insulin receptor, catalytic (p110β) and regulatory (p85α) subunits of PI3K as well as AKT1 and 2 (all p<0...
June 2014: Molecular Metabolism
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