Abstract：
PURPOSE:To demonstrate an objective approach to determining if a negative report from the Radiological Physics Center (RPC) of greater than 10% error is valid or has clinical significance. METHODS:The discrepancy involved the clinical activity (mgRaEq) of Cs-137 sources, some manufactured by 3M and some by Amersham. Measurements were made in the proprietary RPC Well Counter calibrated by the MD Anderson ADCL and our Well Counter (CNMC, Model 44D) calibrated by the same laboratory as well as the University of Wisconsin ADCL. In addition, we possess an Amersham Cs-137 Check Source that had been calibrated by the UW-ADCL in 2002. All clinical sources were checked in both Well Counters on the first visit. One clinical source and the Check Source were measured in a second visit that occurred 51 days later. RESULTS:On the initial RPC visit, 9 of 25 sources had a minimum of an 8% discrepancy between the RPC and the Institution, with a maximum of 11%. Contributing errors included using the incorrect straw position by us, an unexplained 2.3% error in the RPC data identified 73 days post-visit, a 2% variation in Chamber Factors for our Well Counter from the two ADCL's. When we use the 2004 value of Air Kerma Strength for the Check Source to determine a Calibration Factor of the Well Counter, all sources were within 0.5% of their decayed value established in 2002. CONCLUSIONS:This work emphasizes the value of having simple Constancy Check systems in a Quality Assurance program as 'Accuracy' has error bars. The disagreement in calibration data between the ADCL Laboratories, which was at the 2% maximum quoted in their Calibration Reports, is a reminder that there is uncertainty in measurements. Constancy Checks allow one to sort out discrepancies and to answer challenges to the validity of your program.
journal_name
Med Physjournal_title
Medical physicsauthors
Grant W 3rd,Mcgary J,Rosen I,Nitsch P,Davidson Sdoi
10.1118/1.4735271subject
Has Abstractpub_date
2012-06-01 00:00:00pages
3751issue
6Part13eissn
0094-2405issn
2473-4209journal_volume
39pub_type
杂志文章相关文献
MEDICAL PHYSICS文献大全abstract：:The absorbed dose values determined with the Exradin and PTW-Markus plane-parallel chambers were compared to the values obtained with the ferrous sulphate dosimetry for a number of the Philips SL25 and the Therac 20 electron beams. For the plane-parallel chambers, the cavity-gas calibration factor Ngaspp, was derived ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.597800
更新日期：1996-03-01 00:00:00
abstract：PURPOSE:Most modern radiotherapy machines are built with a 2D kV imaging system. Combining this imaging system with a 2D-3D inference method would allow for a ready-made option for real-time 3D tumor tracking. This work investigates and compares the accuracy of four existing 2D-3D inference methods using both motion tr...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.12765
更新日期：2018-03-01 00:00:00
abstract：PURPOSE:The pulse line ion accelerator (PLIA) is a low-cost accelerator concept originally designed to accelerate heavy ions. Our group has been investigating the use of PLIA to accelerate light ions and believe a multi-stage PLIA could be useful for short half-life PET isotope production. The goal of this work was to ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.13875
更新日期：2019-12-01 00:00:00
abstract：:The purpose of this study was to investigate the effect of z overscanning on eye lens dose and effective dose received by pediatric patients undergoing head CT examinations. A pediatric patient study was carried out to obtain the exposure parameters and data regarding the eye lens position with respect to imaged volum...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.2207212
更新日期：2006-07-01 00:00:00
abstract：PURPOSE:Imaging the knee under realistic load-bearing conditions can be carried out in a horizontal plane using a C-arm CT scanner. Human subjects can be scanned in a standing position and acquired data successfully reconstructed. However, reconstructing this data is a challenge due to significant artifacts that are in...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4736213
更新日期：2012-06-01 00:00:00
abstract：:The 1983 AAPM protocol for the determination of absorbed dose from high-energy photon and electron beams recommends using Pion (the reciprocal of collection efficiency), as determined by the two-voltage technique, to correct for recombination losses in ionization chambers. Methods and data for the determination of ion...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.595574
更新日期：1984-11-01 00:00:00
abstract：:Mammography is the most effective method for breast cancer screening available today. However, the low positive predictive value of breast biopsy resulting from mammogram interpretation leads to approximately 70% unnecessary biopsies with benign outcomes. To reduce the high number of unnecessary breast biopsies, sever...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.2786864
更新日期：2007-11-01 00:00:00
abstract：:Several updated Monte Carlo (MC) codes are available to perform calculations of voxel S values for radionuclide targeted therapy. The aim of this work is to analyze the differences in the calculations obtained by different MC codes and their impact on absorbed dose evaluations performed by voxel dosimetry. Voxel S val...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3103401
更新日期：2009-05-01 00:00:00
abstract：:An experiment to determine the peak of the energy spectrum of the photon beam from a Toshiba LMR-15 medical linear accelerator is described. It is found that the flattening filters removed much of the bremsstrahlung spectrum below approximately 1 MeV, resulting in a photon spectrum which peaks around 1.2 MeV. ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.595582
更新日期：1984-11-01 00:00:00
abstract：:We present a theoretical development and experimental verification of a description of power loss and sample resistance for a lossy sample in a nuclear magnetic resonance radio frequency coil for a sample geometry where the eddy current streamlines are disrupted from their usually assumed circular paths. Specifically ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.596336
更新日期：1989-09-01 00:00:00
abstract：PURPOSE:This paper describes the low-kV spectral optimization of dual-energy CT (DECT) equipped with high-kV tin filtration for the quantitative acquisition of electron density information, which is essential for treatment planning in radiotherapy. In addition, an analytical DECT image simulation was preliminarily perf...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3584200
更新日期：2011-06-01 00:00:00
abstract：PURPOSE:To investigate the dosimetric robustness of dynamically collimated proton therapy (DCPT) treatment plans delivered using a dynamic collimation system (DCS) with respect to random uncertainties in beam spot and collimator position as well as systematic offsets in the DCS mounting alignment. This work also demons...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.14208
更新日期：2020-08-01 00:00:00
abstract：:The geometric accuracy and precision of an image-guided treatment system were assessed. Image guidance is performed using an x-ray volume imaging (XVI) system integrated with a linear accelerator and treatment planning system. Using an amorphous silicon detector and x-ray tube, volumetric computed tomography images ar...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.2143141
更新日期：2006-01-01 00:00:00
abstract：PURPOSE:A nanodosimeter is a type of detector which measures single ionizations in a small gaseous volume in order to obtain ionization cluster size probability distributions for characterization of radiation types. Working nanodosimeter detectors are usually bulky machines which require a lot of space. In this work, t...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.14738
更新日期：2021-01-28 00:00:00
abstract：:We designed a questionnaire to be filled out by the physicist at the time of planning treatment with the aid of a computer in order to assess what was learned during the course of the planning session. We analyzed the results to gauge the impact of the 70 treatment planning sessions conducted during the one month peri...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.596302
更新日期：1988-03-01 00:00:00
abstract：:Spread of invasive carcinoma throughout breast tissue is believed to occur at supramolecular levels, beyond the range of standard histopathology identification. Small angle x-ray scattering (SAXS) is capable of characterizing the structural properties of collagen and tissue found in the breast at the scale of tens to ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3147144
更新日期：2009-07-01 00:00:00
abstract：PURPOSE:Determine the effective point of measurement (EPOM) of 12 thimble ion chambers, including miniature chambers and three models widely used for clinical reference dosimetry. The EPOM is the point at which the measured dose would arise in the measurement medium in the absence of the probe: For cylindrical chambers...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3266750
更新日期：2010-01-01 00:00:00
abstract：PURPOSE:To develop an individually optimized contrast-enhanced (CE) 4D-computed tomography (CT) for radiotherapy simulation in pancreatic ductal adenocarcinomas (PDA). METHODS:Ten PDA patients were enrolled. Each underwent three CT scans: a 4D-CT immediately following a CE 3D-CT and an individually optimized CE 4D-CT ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4963213
更新日期：2016-10-01 00:00:00
abstract：PURPOSE:A novel 3D printing method has been developed, which employs human CT images to construct patient specific phantoms by controlling the filament extrusion rate. METHODS:An in-house software was developed comprising pixel-by-pixel (PbP) reading of the Hounsfield Units (HU) values in the original patient DICOM im...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.13154
更新日期：2018-10-01 00:00:00
abstract：PURPOSE:To evaluate the image quality of virtual monochromatic images synthesized from dual-source dual-energy computed tomography (CT) in comparison with conventional polychromatic single-energy CT for the same radiation dose. METHODS:In dual-energy CT, besides the material-specific information, one may also synthesi...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3658568
更新日期：2011-12-01 00:00:00
abstract：:Soft-tissue detectability in cone-beam computed tomography (CBCT) was evaluated via two-alternative forced-choice (2AFC) tests. Investigations included the dependence of detectability on radiation dose, the influence of the asymmetric three-dimensional (3D) noise-power spectrum (NPS) in axial and sagittal or coronal p...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.2790586
更新日期：2007-11-01 00:00:00
abstract：:Simultaneous rest 99mTc-Sestamibi/ 123I-BMIPP cardiac SPECT imaging has the potential to replace current clinical 99mTc-Sestamibi rest/stress imaging and therefore has great potential in the case of patients with chest pain presenting to the emergency department. Separation of images of these two radionuclides is diff...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3063544
更新日期：2009-02-01 00:00:00
abstract：:Radiographic magnification is often employed in mammography to improve detection of small anatomical details of clinical interest, such as microcalcifications. The image size depends on the conventional magnification factor, on the focal spot size, and on the x-ray angulation. In this paper magnification effects are i...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.597288
更新日期：1994-02-01 00:00:00
abstract：:A scintillation dosemeter is calibrated for 90Sr/90Y beta rays from an ophthalmic applicator, using an extrapolation ionization chamber as a reference instrument. The calibration factor for the scintillation dosemeter agrees with that given by the manufacturer of the dosemeter within ca. 2%. The estimated overall unce...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.1709490
更新日期：2004-05-01 00:00:00
abstract：PURPOSE:Mammography is known to be one of the most difficult radiographic exams to interpret. Mammography has important limitations, including the superposition of normal tissue that can obscure a mass, chance alignment of normal tissue to mimic a true lesion and the inability to derive volumetric information. It has b...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3562901
更新日期：2011-04-01 00:00:00
abstract：PURPOSE:We present a simple, practical framework for truly 4D lung IMRT planning based on a weighted individual-phase optimization paradigm. This strategy is specifically developed for use in real-time tumor tracking delivery systems so as to utilize respiratory motion as an additional degree of freedom rather than a c...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4735644
更新日期：2012-06-01 00:00:00
abstract：:Effectiveness of an oral presentation depends on the ability of the speaker to communicate with the audience. An important part of this communication is focusing on two to five key points and emphasizing those points during the presentation. Every aspect of the presentation should be purposeful and directed at facilit...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4735944
更新日期：2012-06-01 00:00:00
abstract：:A computer program was implemented to predict mammography x-ray beam parameters in the range 20-40 kV for Mo/Mo, Mo/Rh, Rh/Rh, and W/Al target/filter combinations. The computation method used to simulate mammography x-ray spectra is based on the Boone et al. model. The beam quality parameters such as the half-value la...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.1608498
更新日期：2003-10-01 00:00:00
abstract：:Nowadays, digital subtraction angiography systems must be able to sustain real-time acquisition (30 frames per second) of 512 x 512 x 8 bit images and store several sequences of such images on low cost and general-purpose mass memories. Concretely, that means a 7.8 Mbytes per second rate and about 780 Mbytes disk spac...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.596309
更新日期：1989-11-01 00:00:00
abstract：PURPOSE:Radiochromic film provides dose measurement at high spatial resolution, but often is not preferred for routine evaluation of patient-specific intensity modulated radiation therapy (IMRT) plans owing to ease-of-use factors. The authors have established an efficient protocol that combines calibration and measurem...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4754797
更新日期：2012-10-01 00:00:00
