Abstract：
:The computed tomography (CT) radiation dose to pediatric patients has received considerable attention recently. Moreover, it is important to be able to determine CT radiation doses for various patient sizes ranging from infants to large adults. The current AAPM protocol only measures CT radiation dose using a 16 cm acrylic phantom to represent an adult head and a 32 cm acrylic phantom to represent an adult body. The goal of this paper is to study the dependence of the computed tomography dose index (CTDI) upon the size of the phantom, the kVp selected and the scan mode employed. Our measurements were done on phantom sizes ranging from 6 cm to 32 cm. The x-ray tube potential ranged from 80 to 140 kVp. The scan modes utilized for the measurements included: consecutive axial scans, single-slice helical scans with variable pitch and multislice helical scans with variable pitch. The results were consolidated into simplified equations which related the phantom diameter and kVp to the measured CTDI. Some generalizations were made about the relationship between the scan modes of the various CT units to the measured radiation doses. The CTDI appears to be an exponential function of phantom diameter. For the same kVp and mAs, the radiation doses for smaller phantoms are much greater than for larger sizes. The derived relationship can be used to estimate the radiation doses for a variety of scan conditions and modes from measurements with the two standard reference phantoms. A method was also given for converting axial CT dose measurements to appropriate MSAD values for helical CT scans.
journal_name
Med Physjournal_title
Medical physicsauthors
Nickoloff EL,Dutta AK,Lu ZFdoi
10.1118/1.1543149subject
Has Abstractpub_date
2003-03-01 00:00:00pages
395-402issue
3eissn
0094-2405issn
2473-4209journal_volume
30pub_type
杂志文章相关文献
MEDICAL PHYSICS文献大全abstract：PURPOSE:Partial scan reconstruction (PSR) artifacts are present in myocardial perfusion imaging using dynamic multidetector computed tomography (MDCT). PSR artifacts appear as temporal CT number variations due to inconsistencies in the angular data range used to reconstruct images and compromise the quantitative value ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3665767
更新日期：2012-01-01 00:00:00
abstract：:A slat collimator in single photon emission computed tomography consists of a set of parallel slats. As the collimator spins, the detector measures a one-dimensional projection data set. A complete data set can be obtained by rotating the detector/collimator assembly around the object (patient) while the collimator sp...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.1485057
更新日期：2002-07-01 00:00:00
abstract：:The relative sensitivity of the half-value layer (HVL) method as a quality index for megavoltage x-ray beams is examined by theoretical calculation and experimental measurements for 4-, 6-, 10-, and 25-MV x-ray beams. It is shown that lower atomic number materials are more sensitive to beam quality changes than higher...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.595794
更新日期：1985-01-01 00:00:00
abstract：:The BEAMnrc/EGSnrc Monte Carlo code system is employed to develop a model of the National Research Council of Canada primary standard of absorbed dose to tissue in a beta radiation field, comprising an extrapolation chamber and 90Sr/90Y beta source. We benchmark the model against the measured response of the chamber i...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.1997347
更新日期：2005-10-01 00:00:00
abstract：PURPOSE:The performance of a newly developed, high resolution, microangiographic fluoroscope (MAF) (35 μm pixel pitch and 300 μm thick CsI phosphor) was evaluated using a generalized linear system analysis and compared with that of a standard amorphous Si thin film transistor flat panel detector (FPD) (194 μm pixel pit...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4792460
更新日期：2013-03-01 00:00:00
abstract：:Beam hardening is a well-known phenomenon for therapeutic accelerator beams passing through matter in narrow beam geometry. This study assesses quantitatively the magnitude of beam hardening of therapeutic beams in water. A formal concept of beam hardening is proposed which is based on the decrease of the mean attenua...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.598704
更新日期：1999-09-01 00:00:00
abstract：PURPOSE:Tumor grading is an important part of breast cancer diagnosis and currently requires biopsy as its standard. Here, the authors investigate quantitative ultrasound parameters in locally advanced breast cancers that can potentially separate tumors from normal breast tissue and differentiate tumor grades. METHODS...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4852875
更新日期：2014-01-01 00:00:00
abstract：:A test device which can indirectly measure the performance of an automatic exposure control system and which offers the potential to reduce the time and film requirements for such tests has been evaluated. Evaluation results demonstrate that the device can successfully predict image optical density to within +/- 0.10 ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.597252
更新日期：1994-01-01 00:00:00
abstract：PURPOSE:Radiopharmaceutical applications in nuclear medicine require a detailed dosimetry estimate of the radiation energy delivered to the human tissues. Over the past years, several publications addressed the problem of internal dose estimate in volumes of several sizes considering photon and electron sources. Most o...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3242304
更新日期：2009-11-01 00:00:00
abstract：PURPOSE:Given its sensitivity to anatomical variations, proton therapy is expected to benefit greatly from integration with magnetic resonance imaging for online anatomy monitoring during irradiation. Such an integration raises several challenges, as both systems mutually interact. The proton beam will experience quasi...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.12961
更新日期：2018-07-01 00:00:00
abstract：:This paper proposes a new respiratory gated radiation treatment system that allows real-time tumor localization while avoiding invasive operation to a patient. The proposed system employs a three-dimensional (3D) ultrasound device, a 3D digital localizer, and a real-time image processing system. At the planning time, ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.1634482
更新日期：2004-02-01 00:00:00
abstract：:Computer-aided diagnosis (CAD) has been a major field of research for the past few decades. CAD uses machine learning methods to analyze imaging and/or nonimaging patient data and makes assessment of the patient's condition, which can then be used to assist clinicians in their decision-making process. The recent succe...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.13764
更新日期：2020-06-01 00:00:00
abstract：PURPOSE:Most clinically deployed strategies for respiratory motion management in lung radiotherapy (e.g., gating and tracking) use external markers that serve as surrogates for tumor motion. However, typical lung phantoms used to validate these strategies are based on a rigid exterior and a rigid or a deformable-interi...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4918581
更新日期：2015-05-01 00:00:00
abstract：:Pixel size is of great interest in the flat-panel detector design because of its potential impact on image quality. In the particular case of angiographic x-ray fluoroscopy, small pixels are required in order to adequately visualize interventional devices such as guidewires and stents which have wire diameters as smal...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.2169907
更新日期：2006-03-01 00:00:00
abstract：PURPOSE:Dynamic myocardial perfusion computed tomography (DM-PCT) imaging offers benefits over quantitative assessment of myocardial blood flow (MBF) for diagnosis and risk stratification of coronary artery disease. However, one major drawback of DM-PCT imaging is that a high radiation level is imparted by repeated sca...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.12285
更新日期：2017-09-01 00:00:00
abstract：PURPOSE:Compton camera imaging (CCI) systems are currently under investigation for radiotherapy dose reconstruction and verification. The ability of such a system to provide real-time images during dose delivery will be limited by the computational speed of the image reconstruction algorithm. In this work, the authors ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3519873
更新日期：2011-01-01 00:00:00
abstract：:In this investigation, five experimental data sets are used to evaluate the ability of the EGSnrc Monte Carlo code to calculate the change in chamber response associated with changes in wall material and cavity dimension at 60Co energies. Calculations of the ratios of response per unit mass of air as a function of cav...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3013701
更新日期：2008-12-01 00:00:00
abstract：PURPOSE:Different approaches have been used in dynamic elastography to assess mechanical properties of biological tissues. Most techniques are based on a simple inversion based on the measurement of the shear wave speed to assess elasticity, whereas some recent strategies use more elaborated analytical or finite elemen...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4942813
更新日期：2016-04-01 00:00:00
abstract：PURPOSE:It is important to enhance image quality for low-dose CT acquisitions to push the ALARA boundary. Current state-of-the-art block-matching three-dimensional (BM3D) denoising scheme assumes white Gaussian noise (WGN) model. This study proposes a novel filtering module to be incorporated into the BM3D framework fo...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.13252
更新日期：2019-01-01 00:00:00
abstract：PURPOSE:Photoacoustic imaging has proven to be able to detect vascularization-driven optical absorption contrast associated with tumors. In order to detect breast tumors located a few centimeter deep in tissue, a sensitive ultrasound detector is of crucial importance for photoacoustic mammography. Further, because the ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4792462
更新日期：2013-03-01 00:00:00
abstract：PURPOSE:Accurate segmentation of lung and infection in COVID-19 computed tomography (CT) scans plays an important role in the quantitative management of patients. Most of the existing studies are based on large and private annotated datasets that are impractical to obtain from a single institution, especially when radi...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.14676
更新日期：2020-12-23 00:00:00
abstract：:Noise characterization through estimation of the noise power spectrum (NPS) is a central component of the evaluation of digital x-ray systems. We begin with a brief review of the fundamentals of NPS theory and measurement, derive explicit expressions for calculation of the one- and two-dimensional (1D and 2D) NPS, and...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.598623
更新日期：1999-07-01 00:00:00
abstract：PURPOSE:In using flat panel detectors (FPD) for cone beam computed tomography (CBCT), pixel gain variations may lead to structured nonuniformities in projections and ring artifacts in CBCT images. Such gain variations can be caused by change in detector entrance exposure levels or beam hardening, and they are not accou...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4893278
更新日期：2014-09-01 00:00:00
abstract：:Encapsulated, cylindrical sources containing 2, 5, and 8 Ci of 241Am have been designed and fabricated for intracavitary irradiation of uterine cancers. Exposure rates in air and dose rates in water around these sources have been measured using an ionization chamber and a lithium fluoride thermoluminescent dosimetry s...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.596007
更新日期：1987-09-01 00:00:00
abstract：PURPOSE:As hypoxic cells are more resistant to photon radiation, it is desirable to obtain information about the oxygen distribution in tumors prior to the radiation treatment. Noninvasive techniques are currently not able to provide reliable oxygenation maps with sufficient spatial resolution; therefore mathematical m...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4812431
更新日期：2013-08-01 00:00:00
abstract：PURPOSE:New technology has been developed to treat age-related macular degeneration (AMD) using 100 kVp pencil-beams that enter the patient through the radio-resistant sclera with a depth of interest between 1.6 and 2.6 cm. Measurement of reference and relative dose in a kilovoltage x-ray beam with a 0.42 cm diameter f...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4863482
更新日期：2014-02-01 00:00:00
abstract：:The purpose of this work is to show the feasibility of using in vivo proton radiography of a radiotherapy patient for the patient individual optimization of the calibration from CT-Hounsfield units to relative proton stopping power. Water equivalent tissue (WET) calibrated proton radiographs of a dog patient treated f...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.1833041
更新日期：2005-01-01 00:00:00
abstract：PURPOSE:The purpose of this study was to evaluate the effect of various computed tomography (CT) thresholds on trapping volumetric measurements by multidetector CT in chronic obstructive pulmonary disease (COPD). METHODS:Twenty-three COPD patients were scanned with a 64-slice CT scanner in both the inspiratory and exp...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4813906
更新日期：2013-08-01 00:00:00
abstract：PURPOSE:To model X-ray coherent scatter diffraction patterns in GEANT4 for simulating experiments involving material detection through diffraction pattern measurement. Although coherent scatter cross-sections are modeled accurately in GEANT4, diffraction patterns for crystalline materials are not yet included. Here we ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4734794
更新日期：2012-06-01 00:00:00
abstract：:Lag and residual contrast have been quantified in an amorphous selenium (a-Se) active-matrix flat-panel imager (AMFPI) as a function of frame time, kilovoltage (kV) and megavoltage (MV) x-ray photon energies and amount of radiation incident on the detector. The AMFPI contains a 200 microm thick a-Se layer deposited on...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.1713298
更新日期：2004-05-01 00:00:00
