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Chumin Zhao, Nikita Vassiljev, Anastasios Konstantinidis, Robert Speller, Jerzy Kanicki
High-resolution, low-noise x-ray detectors based on the complementary metal-oxide-semiconductor (CMOS) active pixel sensor (APS) technology have been developed and proposed for digital breast tomosynthesis (DBT). In this study, we evaluated the three-dimensional (3D) imaging performance of a 50 ��m pixel pitch CMOS APS x-ray detector named DynAMITe (Dynamic Range Adjustable for Medical Imaging Technology). The two-dimensional (2D) angle-dependent modulation transfer function (MTF), normalized noise power spectrum (NNPS), and detective quantum efficiency (DQE) were experimentally characterized and modeled using the cascaded system analysis at oblique incident angles up to 30��...
January 10, 2017: Physics in Medicine and Biology
Nalan Kozaci, Mehmet Oguzhan Ay, Mustafa Avci, Inan Beydilli, Sadullah Turhan, Eda Donertas, Ertan Ararat
OBJECTIVE: It was aimed to compare the efficacy of point-of-care ultrasonography (POCUS) with radiography in the diagnosis and management of metatarsal fracture (MTF). METHODS: Patients aged 5-55 years admitted to emergency room due to low-energy, simple extremity trauma and had a suspected MTF, were included in this prospective study. Patients were evaluated by two different emergency physicians in the emergency room. The first physician performed POCUS examination...
December 23, 2016: Injury
Tae-Hoon Kim, Jong-Hyun Ryu, Chang-Won Jeong, Hong Young Jun, Dong-Woon Heo, Seung Hyun Lee, Yeon Kyun Oh, Mi-Jung Lee, Kwon-Ha Yoon
This study was aimed to assess the radiation dose and image quality of a mini-mobile digital imaging (mini-DI) system for neonatal chest radiography and compared to conventional digital radiography (DR). A total of 64 neonates were examined and anatomical landmarks were assessed. The entrance surface dose of mini DI and conventional DR was 26.64±0.15 μGy and 49.11±1.46 μGy, respectively (p<0.001). The mean SNR values for mini-DI and DR were 233.2±5.1 and 31.6±1.2, and 10% MTF values were 131 and 161μm...
December 6, 2016: Clinical Imaging
Yi Xue, Ruoshui Ruan, Xiuhua Hu, Yu Kuang, Jing Wang, Yong Long, Tianye Niu
PURPOSE: Dual-energy CT (DECT) enhances tissue characterization because of its basis material decomposition capability. In addition to conventional two-material decomposition from DECT measurements, multi-material decomposition (MMD) is required in many clinical applications. To solve the ill-posed problem of reconstructing multiple-material images from dual-energy measurements, additional constraints are incorporated into the formulation, including volume and mass conservation and the assumptions that at most three materials in each pixel and various material types among pixels...
January 6, 2017: Medical Physics
Y Hu, R Fueglistaller, J Rottmann, M Myronakis, A Wang, D Shedlock, D Morf, J Star-Lack, R Berbeco
PURPOSE: The purpose of this study was to validate the use of a cascaded linear system model for MV cone-beam CT (CBCT) using a multi-layer (MLI) electronic portal imaging device (EPID) and provide experimental insight into image formation. A validated 3D model provides insight into salient factors affecting reconstructed image quality, allowing potential for optimizing detector design for CBCT applications. METHODS: A cascaded linear system model was developed to investigate the potential improvement in reconstructed image quality for MV CBCT using an MLI EPID...
June 2016: Medical Physics
Tia E Plautz, R P Johnson, H F-W Sadrozinski, A Zatserklyaniy, V Bashkirov, R F Hurley, R W Schulte, P Piersimoni, V Giacometti
PURPOSE: To characterize the modulation transfer function (MTF) of the pre-clinical (phase II) head scanner developed for proton computed tomography (pCT) by the pCT collaboration. To evaluate the spatial resolution achievable by this system. METHODS: Our phase II proton CT scanner prototype consists of two silicon telescopes that track individual protons upstream and downstream from a phantom, and a 5-stage scintillation detector that measures a combination of the residual energy and range of the proton...
June 2016: Medical Physics
M Myronakis, J Rottmann, Y Hu, A Wang, D Shedlock, D Morf, J Star-Lack, R Berbeco
PURPOSE: To develop and validate a Monte Carlo (MC) model of a novel multi-layer imager (MLI) for megavolt (MV) energy beams. The MC model will enable performance optimization of the MLI design for clinical applications including patient setup verification, tumor tracking and MVCBCT. METHODS: The MLI is composed of four layers of converter, scintillator and light detector, each layer similar to the current clinical AS1200 detector (Varian Medical Systems, Inc). The MLI model was constructed using the Geant4 Application for Tomographic Emission (GATE v7...
June 2016: Medical Physics
Y Hu, J Rottmann, M Myronakis, R Berbeco
PURPOSE: The purpose of this study was to quantify the improvement in tumor tracking, with and without fiducial markers, afforded by employing a multi-layer (MLI) electronic portal imaging device (EPID) over the current state-of-the-art, single-layer, digital megavolt imager (DMI) architecture. METHODS: An ideal observer signal-to-noise ratio (d') approach was used to quantify the ability of an MLI EPID and a current, state-of-the-art DMI EPID to track lung tumors from the treatment beam's-eye-view...
June 2016: Medical Physics
S J Blake, J Cheng, P Vial, M Lu, S Atakaramians, S Meikle, Z Kuncic
PURPOSE: To evaluate the megavoltage imaging performance of a novel, water-equivalent electronic portal imaging device (EPID) developed for simultaneous imaging and dosimetry applications in radiotherapy. METHODS: A novel EPID prototype based on active matrix flat panel imager technology has been developed by our group and previously reported to exhibit a water-equivalent dose response. It was constructed by replacing all components above the photodiode detector in a standard clinical EPID (including the copper plate and phosphor screen) with a 15 × 15 cm(2) array of plastic scintillator fibers...
June 2016: Medical Physics
M Russ, C Ionita, D Bednarek, S Rudin
PURPOSE: The Generalized Relative Object Detectability (G-ROD) family of ideal observer metrics are a well-characterized set of task-based metrics used for quantitatively comparing imaging systems that include the detector, focal spot geometry and scatter characteristics on the basis of system abilities in imaging a given simulated object. The G-ROD metric takes the integral over spatial frequencies of the Fourier transform of a simulated object function weighted with the detector generalized DQE (GDQE), divided by the comparable integral for another detector...
June 2016: Medical Physics
O Ozguner, S Halliburton, A Dhanantwari, G Wen, S Utrup, D Jordan
PURPOSE: To obtain objective reference data for the spectral performance on a dual-layer detector CT platform (IQon, Philips) and compare virtual monoenergetic to conventional CT images. METHODS: Scanning was performed using the hospital's clinical adult body protocol: helical acquisition at 120kVp, with CTDIvol=15mGy. Multiple modules (591, 515, 528) of a CATPHAN 600 phantom and a 20 cm diameter cylindrical water phantom were scanned. No modifications to the standard protocol were necessary to enable spectral imaging...
June 2016: Medical Physics
S Vedantham, S Shrestha, L Shi, G Vijayaraghavan, A Karellas
PURPOSE: To optimize the cesium iodide (CsI:Tl) scintillator thickness in a complimentary metal-oxide semiconductor (CMOS)-based detector for use in dedicated cone-beam breast CT. METHODS: The imaging task considered was the detection of a microcalcification cluster comprising six 220µm diameter calcium carbonate spheres, arranged in the form of a regular pentagon with 2 mm spacing on its sides and a central calcification, similar to that in ACR-recommended mammography accreditation phantom, at a mean glandular dose of 4...
June 2016: Medical Physics
D A Scaduto, M Goodsitt, H-P Chan, H Olafsdottir, M Das, E Fredenberg, W Geiser, D Goodenough, P Heid, Y-H Hu, B Liu, J Mainprize, I Reiser, R Van Engen, V Varchena, S Vecchio, S Glick, W Zhao
PURPOSE: Spatial resolution in digital breast tomosynthesis (DBT) is affected by inherent/binned detector resolution, oblique entry of x-rays, and focal spot size/motion; the limited angular range further limits spatial resolution in the depth-direction. While DBT is being widely adopted clinically, imaging performance metrics and quality control protocols have not been standardized. AAPM Task Group 245 on Tomosynthesis Quality Control has been formed to address this deficiency. METHODS: Methods of measuring spatial resolution are evaluated using two prototype quality control phantoms for DBT...
June 2016: Medical Physics
J Solomon, Y Zhang, D Marin, E Samei
PURPOSE: Dose optimization studies in CT have a need for images acquired at multiple dose levels. This presents ethical and logistical challenges for performing such research with human subjects. As a result, most studies rely on phantom data. The purpose of this study was to perform a physics-based validation of a method to obtain images of the same patient at multiple dose levels using a single CT acquisition on a dual-source CT system. METHODS: The Dose Split (DS) method relies on acquiring raw projection data simultaneously from two separate sources/detectors (denoted Tube A and Tube B) on a dual-source system...
June 2016: Medical Physics
S Bache, J Rong
PURPOSE: To quantify a radiology team's assessment of image quality differences between two CT scanner models currently in clinical use, with emphasis on spatial resolution that could be impacted by focal spot size. METHODS: Modulation Transfer Functions (MTF) measurements were performed by scanning the impulse source insert module of the Catphan 600 at 120/140 kVp with both large (LFS) and small (SFS) focal spots and reconstructed to 2.5mm and 5.0mm thicknesses on a GE Discovery CT750 HD and a LightSpeed VCT CT scanner...
June 2016: Medical Physics
T Richards, S Mann, E Samei
PURPOSE: Measure the temporal modulation transfer function (TMTF) of clinical fluoroscopic flat panel imaging systems in order to accurately quantify their performance for temporally sensitive clinical tasks. METHODS: Copper blades (0.76 mm thick, 6 cm radius) with precision-machined edges were manufactured and mounted on a voltage regulated DC motor apparatus. Images were acquired with the blade apparatus positioned at the center of the detector matrix and set in motion at a constant rotational velocity (0...
June 2016: Medical Physics
A Shankar, M Russ, S Vijayan, D Bednarek, S Rudin
PURPOSE: Signal and noise aliasing are major issues with high resolution direct and indirect detectors for which the Apodized Aperture Pixel (AAP) design provides an alternative solution. METHODS: High resolution detectors for neurovascular interventions have MTFs that remain significant even at the Nyquist frequency. Under-sampling in such detectors, leads to aliasing of object frequencies and noise. Frequencies above the Nyquist wrap into the lower frequency range leading to aliasing...
June 2016: Medical Physics
J Rottmann, M Myronakis, Y Hu, D Shedlock, A Wang, D Humber, D Morf, R Fueglistaller, J Star-Lack, R Berbeco
PURPOSE: Beams-eye-view imaging applications such as real-time soft-tissue motion estimation and MV-CBCT are hindered by the inherently low image contrast of electronic portal imaging devices (EPID) currently in clinical use. We investigate a cost effective scintillating glass that provides substantially increased detective quantum efficiency (DQE) and contrast to noise ratio (CNR). METHODS: A pixelated scintillator prototype was built from LKH-5 glass. The array is 12mm thick; 42...
June 2016: Medical Physics
Yue-Houng Hu, David A Scaduto, Wei Zhao
PURPOSE: Contrast-enhanced (CE) breast imaging involves the injection contrast agents (i.e., iodine) to increase conspicuity of malignant lesions. CE imaging may be used in conjunction with digital mammography (DM) or digital breast tomosynthesis (DBT) and has shown promise in improving diagnostic specificity. Both CE-DM and CE-DBT techniques require optimization as clinical diagnostic tools. Physical factors including x-ray spectra, subtraction technique, and the signal from iodine contrast, must be considered to provide the greatest object detectability and image quality...
November 21, 2016: Medical Physics
Pu Zhang, Guoqing Wan, Fei Li, Xingdong Li, Wenli Liu, Guangzhi Wang
PURPOSE: In China, most quality assessments (QAs) of the high contrast resolution of medical computed tomography (CT) equipment is performed by subjective evaluation, which is simple but dependent on observer expertise. The purpose of this study was to compare the accuracy and degree of dispersion of evaluation results from observers with different expertise and to develop an objective, easily understandable new approach to minimize the error caused by the subjective nature of observer evaluation...
December 26, 2016: Medical Physics
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