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Low field MRI

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https://www.readbyqxmd.com/read/28081157/simultaneous-quantitative-mri-mapping-of-t1-t2-and-magnetic-susceptibility-with-multi-echo-mp2rage
#1
Riccardo Metere, Tobias Kober, Harald E Möller, Andreas Schäfer
The knowledge of relaxation times is essential for understanding the biophysical mechanisms underlying contrast in magnetic resonance imaging. Quantitative experiments, while offering major advantages in terms of reproducibility, may benefit from simultaneous acquisitions. In this work, we demonstrate the possibility of simultaneously recording relaxation-time and susceptibility maps with a prototype Multi-Echo (ME) Magnetization-Prepared 2 RApid Gradient Echoes (MP2RAGE) sequence. T1 maps can be obtained using the MP2RAGE sequence, which is relatively insensitive to inhomogeneities of the radio-frequency transmit field, [Formula: see text]...
2017: PloS One
https://www.readbyqxmd.com/read/28079398/feasibility-evaluation-of-diffusion-weighted-imaging-using-an-integrated-mri-radiotherapy-system-for-response-assessment-to-neoadjuvant-therapy-in-rectal-cancer
#2
Narek Shaverdian, Yingli Yang, Peng Hu, Steven Hart, Ke Sheng, James Lamb, Minsong Cao, Nzhde Agazaryan, David Thomas, Michael Steinberg, Daniel A Low, Percy Lee
OBJECTIVES: To evaluate the feasibility of on-board DWI with an integrated low-field MRI-radiotherapy system to assess responses to neoadjuvant chemoradiation (NAC) in rectal cancer. METHODS: A spin echo-based planar imaging diffusion sequence on a 0.35 T MRI-radiotherapy system was acquired over the course of NAC. The apparent diffusion coefficients (ADC) from the tumor region of interest (ROIs) were calculated. A functional diffusion map (fDM) was created showing a pixel-wise ADC analysis of the ROI over the course of treatment...
January 12, 2017: British Journal of Radiology
https://www.readbyqxmd.com/read/28074903/alterations-in-the-brain-adenosine-metabolism-cause-behavioral-and-neurological-impairment-in-ada-deficient-mice-and-patients
#3
Aisha V Sauer, Raisa Jofra Hernandez, Francesca Fumagalli, Veronica Bianchi, Pietro L Poliani, Chiara Dallatomasina, Elisa Riboni, Letterio S Politi, Antonella Tabucchi, Filippo Carlucci, Miriam Casiraghi, Nicola Carriglio, Manuela Cominelli, Carlo Alberto Forcellini, Federica Barzaghi, Francesca Ferrua, Fabio Minicucci, Stefania Medaglini, Letizia Leocani, Giancarlo la Marca, Lucia D Notarangelo, Chiara Azzari, Giancarlo Comi, Cristina Baldoli, Sabrina Canale, Maria Sessa, Patrizia D'Adamo, Alessandro Aiuti
Adenosine Deaminase (ADA) deficiency is an autosomal recessive variant of severe combined immunodeficiency (SCID) caused by systemic accumulation of ADA substrates. Neurological and behavioral abnormalities observed in ADA-SCID patients surviving after stem cell transplantation or gene therapy represent an unresolved enigma in the field. We found significant neurological and cognitive alterations in untreated ADA-SCID patients as well as in two groups of patients after short- and long-term enzyme replacement therapy with PEG-ADA...
January 11, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28053326/scanning-the-horizon-towards-transparent-and-reproducible-neuroimaging-research
#4
Russell A Poldrack, Chris I Baker, Joke Durnez, Krzysztof J Gorgolewski, Paul M Matthews, Marcus R Munafò, Thomas E Nichols, Jean-Baptiste Poline, Edward Vul, Tal Yarkoni
Functional neuroimaging techniques have transformed our ability to probe the neurobiological basis of behaviour and are increasingly being applied by the wider neuroscience community. However, concerns have recently been raised that the conclusions that are drawn from some human neuroimaging studies are either spurious or not generalizable. Problems such as low statistical power, flexibility in data analysis, software errors and a lack of direct replication apply to many fields, but perhaps particularly to functional MRI...
January 5, 2017: Nature Reviews. Neuroscience
https://www.readbyqxmd.com/read/28048790/su-f-j-112-clinical-feasibility-test-of-an-rf-pulse-based-mri-method-for-the-quantitative-fat-water-segmentation
#5
S Yee, J Wloch, M Pirkola
PURPOSE: Quantitative fat-water segmentation is important not only because of the clinical utility of fat-suppressed MRI images in better detecting lesions of clinical significance (in the midst of bright fat signal) but also because of the possible physical need, in which CT-like images based on the materials' photon attenuation properties may have to be generated from MR images; particularly, as in the case of MR-only radiation oncology environment to obtain radiation dose calculation or as in the case of hybrid PET/MR modality to obtain attenuation correction map for the quantitative PET reconstruction...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048364/we-fg-207a-01-introduction-to-dedicated-breast-ct-early-studies
#6
S Vedantham
: Mammography-based screening has been a valuable imaging tool for the early detection of non-palpable lesions and has contributed to significant reduction in breast cancer associated mortality. However, the breast imaging community recognizes that mammography is not ideal, and in particular is inferior for women with dense breasts. Also, the 2-D projection of a 3-D organ results in tissue superposition contributing to false-positives. The sensitivity of mammography is breast-density dependent...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048141/su-f-j-153-acr-mri-phantom-test-on-a-1-5t-mr-simulator-with-flexible-coils-setting-and-performance-comparison-to-volumetric-head-coil-setting
#7
J Yuan, O Wong, K Cheung, S Yu
PURPOSE: To accommodate head-and-neck (HN) RT simulation scan with immobilization, sub-optimized flexible radiofrequency coils have to be used on an MR-sim rather than a volumetric head coil for diagnostic radiological (DR) applications. In this study, we present and compare ACR MRI phantom test with flexible coils setting (RT-setting) and volumetric head coil setting (DR-setting). METHODS: Two 8-channel array coils were wrapped close to an ACR MRI phantom placed on a flat couch-top in RT-setting for acquisition...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048119/su-f-t-102-automatic-curation-for-a-scalable-registry-using-machine-learning
#8
D Ruan, W Shao, J Wong, D Veruttipong, M Steinberg, D Low, P Kupelian
PURPOSE: growing partnership and contributors to registry efforts an efficient way to perform data integration, de-duplication, and cleansing, amongst other tasks. This project aims to develop an automatic curation module to discover, clean, and transform new data, and semantically integrate them with the composite hosting registry upon de-duplication. METHODS: We have investigated various similarity metrics for various attributes and value types in the registry...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048061/mo-fg-campus-jep2-01-4d-mri-with-3d-radial-sampling-and-self-gating-based-k-space-sorting-image-quality-improvement-by-slab-selective-excitation
#9
Z Deng, W Yang, J Pang, R Tuli, X Bi, B Hakimian, B Fraass, D Li, Z Fan
PURPOSE: A recent 4D MRI technique based on 3D radial sampling and self-gating-based K-space sorting has shown promising results in characterizing respiratory motion. However due to continuous acquisition and potentially drastic k-space undersampling resultant images could suffer from low blood-to-tissue contrast and streaking artifacts. In this study 3D radial sampling with slab-selective excitation (SS) was proposed in attempt to enhance blood-to-tissue contrast by exploiting the in-flow effect and to suppress the excess signal from the peripheral structures particularly in the superior-inferior direction...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28047811/th-ab-bra-12-experimental-results-from-the-first-high-field-inline-mri-linac
#10
P Keall, B Dong, P Vial, A Walker, K Zhang, J Begg, R Rai, L Holloway, M Barton, S Crozier, G Liney
PURPOSE: The pursuit of real-time image guided radiotherapy using optimal tissue contrast has seen the development of several hybrid MRI-treatment systems, high field and low field, and inline and perpendicular configurations. As part of a new MRI-Linac program, an MRI scanner was integrated with a linear accelerator to enable investigations of a coupled inline MRI-Linac system. This work describes our experimental results from the first high-field inline MRI-Linac. METHODS: A 1...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28047787/th-ab-bra-02-automated-triplet-beam-orientation-optimization-for-mri-guided-co-60-radiotherapy
#11
D Nguyen, D Thomas, M Cao, D O'Connor, J Lamb, K Sheng
PURPOSE: MRI guided Co-60 provides daily and intrafractional MRI soft tissue imaging for improved target tracking and adaptive radiotherapy. To remedy the low output limitation, the system uses three Co-60 sources at 120° apart, but using all three sources in planning is considerably unintuitive. We automate the beam orientation optimization using column generation, and then solve a novel fluence map optimization (FMO) problem while regularizing the number of MLC segments. METHODS: Three patients-1 prostate (PRT), 1 lung (LNG), and 1 head-and-neck boost plan (H&NBoost)-were evaluated...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28047717/we-fg-207a-02-why-we-need-breast-ct-clinical-perspective
#12
A O'Connell
: Mammography-based screening has been a valuable imaging tool for the early detection of non-palpable lesions and has contributed to significant reduction in breast cancer associated mortality. However, the breast imaging community recognizes that mammography is not ideal, and in particular is inferior for women with dense breasts. Also, the 2-D projection of a 3-D organ results in tissue superposition contributing to false-positives. The sensitivity of mammography is breast-density dependent...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28047520/we-fg-207a-05-dedicated-breast-ct-as-a-diagnostic-imaging-tool-physics-and-clinical-feasibility
#13
A Karellas
: Mammography-based screening has been a valuable imaging tool for the early detection of non-palpable lesions and has contributed to significant reduction in breast cancer associated mortality. However, the breast imaging community recognizes that mammography is not ideal, and in particular is inferior for women with dense breasts. Also, the 2-D projection of a 3-D organ results in tissue superposition contributing to false-positives. The sensitivity of mammography is breast-density dependent...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28047460/su-f-j-143-initial-assessment-of-image-quality-of-an-integrated-mr-linac-system-with-acr-phantom
#14
J Wang, J Yung, M Kadbi, Y Ding, C Fuller, G Ibbott
PURPOSE/OBJECTIVE(S): To assess the image quality of an integrated MR-Linac system and compare with other MRI systems that are primarily used for diagnostic purposes. MATERIALS/METHODS: An ACR MRI quality control (QC) phantom was used to evaluate the image quality of a fully integrated 1.5T MRI-Linac system recently installed at our institution. This system has a new split magnet design which gives the magnetic field strength of 1.5T. All images were acquired with a set of phased-array surface coils which are designed to have minimal attention of radiation beam...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28047215/tu-h-bra-01-the-physics-of-high-power-radiofrequency-isolation-in-a-novel-compact-linear-accelerator-based-mri-guided-radiation-therapy-system
#15
J Lamb, D Low, S Mutic, S Shvartsman, T Chmielewski, G Fought, A Sharma, J Dempsey
PURPOSE: To develop a method for isolating the radiofrequency waves emanating from linear accelerator components from the magnetic resonance imaging (MRI) system of an integrated MRI-linac. METHODS: An MRI-guided radiation therapy system has been designed that integrates a linear accelerator with simultaneous MR imaging. The radiofrequency waves created by the accelerating process would degrade MR image quality, so a method for containing the radiofrequency waves and isolating the MR imager from them was developed...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28047162/tu-h-bra-08-the-design-and-characteristics-of-a-novel-compact-linac-based-mri-guided-radiation-therapy-mr-igrt-system
#16
S Mutic, D Low, T Chmielewski, G Fought, M Hernandez, I Kawrakow, A Sharma, S Shvartsman, J Dempsey
PURPOSE: To describe the design and characteristics of a novel linac-based MRI guided radiation therapy system that addresses RF and magnetic field interference and that can be housed in conventional radiotherapy vaults. METHODS: The MR-IGRT system will provide simultaneous MR imaging combined with both simple (3D) and complex (IMRT, SBRT, SRS) techniques. The system is a combination of a) double-donut split solenoidal superconducting 0.345T MRI; and b) a 90 cm isocenter ring-gantry mounted 6MV, flattening filter-free linac coupled with a stacked doubly-focused multileaf collimator with 4 mm resolution...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28047083/su-c-bra-01-interactive-auto-segmentation-for-bowel-in-online-adaptive-mri-guided-radiation-therapy-by-using-a-multi-region-labeling-algorithm
#17
Y Lu, I Chen, R Kashani, H Wan, N Maughan, D Muccigrosso, P Parikh
PURPOSE: In MRI-guided online adaptive radiation therapy, re-contouring of bowel is time-consuming and can impact the overall time of patients on table. The study aims to auto-segment bowel on volumetric MR images by using an interactive multi-region labeling algorithm. METHODS: 5 Patients with locally advanced pancreatic cancer underwent fractionated radiotherapy (18-25 fractions each, total 118 fractions) on an MRI-guided radiation therapy system with a 0.35 Tesla magnet and three Co-60 sources...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28047068/we-fg-207a-03-low-dose-cone-beam-breast-ct-physics-and-technology-development
#18
J Boone
: Mammography-based screening has been a valuable imaging tool for the early detection of non-palpable lesions and has contributed to significant reduction in breast cancer associated mortality. However, the breast imaging community recognizes that mammography is not ideal, and in particular is inferior for women with dense breasts. Also, the 2-D projection of a 3-D organ results in tissue superposition contributing to false-positives. The sensitivity of mammography is breast-density dependent...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28047052/th-ab-bra-10-the-physics-of-interface-effects-for-radiation-treatments-in-a-mri-linac-a-monte-carlo-study
#19
S Ahmad, A Sarfehnia, A Kim, M Wronski, A Sahgal, B Keller
PURPOSE: To investigate and explain the interface effects for clinically relevant materials being irradiated in the presence of a 1.5 T transverse magnetic field. METHODS: Interface effects were investigated using Geant4.10.1 both with (B-On) and without (B-Off) a magnetic field for an Elekta MRI-Linac. A slab of thickness 8 cm, representing inhomogeneity, was placed at a depth of 4 cm in a 20×20×20 cm water phantom. Backscattered electron fluence was calculated through a 20×20 cm plane aligned with the surface of the inhomogeneity...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28047048/su-f-t-662-feasibility-study-of-fe3o4-taox-nano-particles-as-a-radiosensitizer-for-radiation-therapy
#20
S Ahn, N Lee, S Shin, C Choi, Y Han, H Park, D Choi, D Lim
PURPOSE: To investigate the feasibility of using multifunctional Fe3 O4 /TaOx(core / shell) nano particles developed for CT and MRI contrast agent as dose enhancing radiosensitizers. METHODS: Firstly, to verify the imaging detectability of Fe3 O4 /TaOx nano particles, in-vivo tests were conducted. Approximately 600 mg/kg of 19 nm diameter Fe3 O4 /TaOx nano particles dispersed in phosphate buffered saline(PBS) were injected to ten nude Balb/c mice through the tail vein...
June 2016: Medical Physics
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