Abstract:
PURPOSE:In medical imaging, data scaling is sometimes desired to handle the system complexity, such as uniformity calibration. Since the data are usually saved in short integer, conventional data scaling will first scale the data in floating point format and then truncate or round the floating point data to short integer data. For example, when using truncation, scaling of 9 by 1.1 results in 9 and scaling of 10 by 1.1 results in 11. When the count level is low, such scaling may change the local data distribution and affect the intended application of the data. METHODS:In this work, the authors use an example gated cardiac SPECT study to illustrate the effect of conventional scaling by factors of 1.1 and 1.2. The authors then scaled the data with the same scaling factors using a randomization approach, in which a random number evenly distributed between 0 and 1 is generated to determine how the floating point data will be saved as short integer data. If the random number is between 0 and 0.9, then 9.9 will be saved as 10, otherwise 9. In other words, the floating point value 9.9 will be saved in short integer value as 10 with 90% probability or 9 with 10% probability. For statistical analysis of the performance, the authors applied the conventional approach with rounding and the randomization approach to 50 consecutive gated studies from a clinical site. RESULTS:For the example study, the image reconstructed from the original data showed an apparent perfusion defect at the apex of the myocardium. The defect size was noticeably changed by scaling with 1.1 and 1.2 using the conventional approaches with truncation and rounding. Using the randomization approach, in contrast, the images from the scaled data appeared identical to the original image. Line profile analysis of the scaled data showed that the randomization approach introduced the least change to the data as compared to the conventional approaches. For the 50 gated data sets, significantly more studies showed quantitative differences between the original images and the images from the data scaled by 1.2 using the rounding approach than the randomization approach [46/50 (92%) versus 3/50 (6%), p < 0.05]. Likewise, significantly more studies showed visually noticeable differences between the original images and the images from the data scaled by 1.2 using the rounding approach than randomization [29/50 (58%) versus 1/50 (2%), p < 0.05]. CONCLUSIONS:In conclusion, the proposed randomization approach minimizes the scaling-introduced local data change as compared to the conventional approaches. It is preferred for nuclear medicine data scaling.
journal_name
Med Physjournal_title
Medical physicsauthors
Bai C,Conwell R,Kindem Jdoi
10.1118/1.3431573subject
Has Abstractpub_date
2010-06-01 00:00:00pages
2796-803issue
6eissn
0094-2405issn
2473-4209journal_volume
37pub_type
杂志文章相关文献
MEDICAL PHYSICS文献大全abstract::We discuss a formalism for clinical proton beam dosimetry based on the use of ionization chamber absorbed dose-to-water calibration and beam quality correction factors. A quantity kQ, the beam quality correction factor, is defined which corrects the absorbed dose-to-water calibration factor ND,w in a reference beam of...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.597768
更新日期:1996-01-01 00:00:00
abstract::With intensity-modulated radiotherapy (IMRT), a variety of user-defined dose distribution can be produced using inverse planning. The generalized equivalent uniform dose (gEUD) has been used in IMRT optimization as an alternative objective function to the conventional dose-volume-based criteria. The purpose of this st...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1897464
更新日期:2005-05-01 00:00:00
abstract::An analytic expression is derived for the transmission of isotropic scattered radiation incident upon an ideal parallel grid. It is found that the expression for the transmission usually found in the literature overestimates the transmission by approximately a factor of two. ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.594877
更新日期:1981-11-01 00:00:00
abstract::A beam intensity monitor was tested in a 230-MeV proton beam at the Loma Linda Proton Therapy Accelerator during its commissioning at Fermi National Accelerator Laboratory. The intensity monitor was designed to regulate the beam intensity extracted from the proton synchrotron. The proton beam is tunable between 70 and...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.596636
更新日期:1991-07-01 00:00:00
abstract:PURPOSE:In this report, the authors introduce the general concept of the completeness map, as a means to evaluate the completeness of data acquired by a given CT system design (architecture and scan mode). They illustrate the utility of completeness map by applying the completeness map concept to a number of candidate ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3700172
更新日期:2012-05-01 00:00:00
abstract:PURPOSE:Radiation treatments are trending toward delivering higher doses per fraction under stereotactic radiosurgery and hypofractionated treatment regimens. There is a need for accurate 3D in vivo patient dose verification using electronic portal imaging device (EPID) measurements. This work presents a model-based te...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4935199
更新日期:2015-12-01 00:00:00
abstract::The image artifacts characteristic of a scanning chest radiographic system are reviewed. The technique employs a pulsed beam of radiation swept in an overlapping raster pattern that can result in severe ripple and scan line artifacts with improper scanning parameters. A one-dimensional treatment of the scanner geometr...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.595492
更新日期:1984-03-01 00:00:00
abstract::Conventional chest radiography is limited by the presence of scattered radiation and the small useful exposure range of radiographic film. A computer-assisted scanning system to minimize these two effects is outlined. The system uses a small beam of radiation swept over the patient's chest in a raster pattern to expos...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.595327
更新日期:1983-09-01 00:00:00
abstract:PURPOSE:Color images are visualized on medical monitors that are adjusted by a grayscale standard display function (GSDF) or γ2.2. Although the GSDF is visually displayed as a linear graded grayscale, it does not specify how color medical images should be presented. On the other hand, the usual gamma setting for color ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.13532
更新日期:2019-06-01 00:00:00
abstract::Variation of the photoactivation rate across radiation fields of three different bremsstrahlung beams of two medical accelerators has been measured, making use of the photonuclear reactions in natural indium probes: 115In(y,y')115mIn and 115In(y,n)114mIn. The third nuclear reaction, 115In(n,y)116mIn, was used to detec...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.598558
更新日期:1999-04-01 00:00:00
abstract::Analytic microdosimetry using Fourier transform techniques has been applied to internal alpha emitters. These techniques need revision and simplification for use with short-lived radionuclides such as those which may be useful for radioimmunotherapy. Analytic methods may have advantages over Monte Carlo methods in som...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.596770
更新日期:1992-11-01 00:00:00
abstract::Preclinical experiments are carried out with approximately 20-30 microm wide, approximately 10 mm high parallel microbeams of hard, broad-"white"-spectrum x rays (approximately 50-600 keV) to investigate microbeam radiation therapy (MRT) of brain tumors in infants for whom other kinds of radiotherapy are inadequate an...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1562169
更新日期:2003-04-01 00:00:00
abstract::Studies suggest that clinical outcomes are improved in repeat trigeminal neuralgia (TN) Gamma Knife radiosurgery if a different part of the nerve from the previous radiosurgery is treated. The MR images taken in the first and repeat radiosurgery need to be coregistered to map the first radiosurgery volume onto the sec...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1944287
更新日期:2005-07-01 00:00:00
abstract:PURPOSE:Intraventricular hemorrhage (IVH) is a major cause of brain injury in preterm neonates. Three dimensional ultrasound (US) imaging systems have been developed to visualize 3D anatomical structure of preterm neonatal intracranial ventricular system with IVH and ventricular dilation. To allow quantitative analysis...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4932366
更新日期:2015-11-01 00:00:00
abstract::The relatively precise placement of brachytherapy sources afforded by stereotactic frames for brain implants is not generally achievable for other sites, which lack the fixed geometry of the cranium and its contents. An exception is a source-containing rigid mold that delivers brachytherapy when inserted securely in a...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.597454
更新日期:1995-03-01 00:00:00
abstract:PURPOSE:Spirometry exhibits baseline drift and frequent measurement errors so it cannot be used by itself to provide tidal volume-based image sorting or breathing motion modeling. Other breathing surrogates, in this study an abdominal bellows system, are drift free but do not measure tidal volume. Simultaneously using ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3284282
更新日期:2010-02-01 00:00:00
abstract::Cone-beam computed tomography systems have been developed to provide in situ imaging for the purpose of guiding radiation therapy. Clinical systems have been constructed using this approach, a clinical linear accelerator (Elekta Synergy RP) and an iso-centric C-arm. Geometric calibration involves the estimation of a s...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1869652
更新日期:2005-04-01 00:00:00
abstract:PURPOSE:Accurate, patient-specific radiation dosimetry for CT scanning is critical to optimize radiation doses and balance dose against image quality. While Monte Carlo (MC) simulation is often used to estimate doses from CT, comparison of estimates to experimentally measured values is lacking for advanced CT scanners ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.13780
更新日期:2019-11-01 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:PURPOSE:On-board MRI can provide superb soft tissue contrast for improving liver SBRT localization. However, the availability of on-board MRI in clinics is extremely limited. On the contrary, on-board kV imaging systems are widely available on radiotherapy machines, but its capability to localize tumors in soft tissue ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.12998
更新日期:2018-07-01 00:00:00
abstract:PURPOSE:To apply the recent code of practice from the IAEA/AAPM, TRS 483, to helical tomotherapy (HT) for reference and relative dosimetry obtaining correction factors for the Exradin A1SL ionization chamber. METHODS:The beam quality correction factor for the A1SL chamber was obtained through three different approache...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.13855
更新日期:2019-12-01 00:00:00
abstract:OBJECTIVES:To evaluate the performance of RapidArc® (Eclipse 10.0.28) and SmartArc® (Pinnacle 9.0) radiotherapy plans for lung stereotactic body radiation therapy (SBRT) in terms of dosimetric plan quality, delivery efficiency, inhomogeneity corrections and accuracy of dose delivery using a custom-built heterogeneity i...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4740172
更新日期:2012-07-01 00:00:00
abstract::The authors present an alternative approach to inverse planning optimization and apply it to volumetric modulated are therapy (VMAT) in one rotation with a prior knowledge about the type of leaf motions. The optimization is based on the projection theorem in inner product spaces. MLC motion is directly considered in t...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3173815
更新日期:2009-08-01 00:00:00
abstract:PURPOSE:To validate GPUMCD, a new package for fast Monte Carlo dose calculations based on the GPU (graphics processing unit), as a tool for low-energy single seed brachytherapy dosimetry for specific seed models. As the currently accepted method of dose calculation in low-energy brachytherapy computations relies on sev...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3598441
更新日期:2011-07-01 00:00:00
abstract:PURPOSE:X-ray phase-contrast tomography (PCT) is a rapidly emerging imaging modality for reconstructing estimates of an object's three-dimensional x-ray refractive index distribution. Unlike conventional x-ray computed tomography methods, the statistical properties of the reconstructed images in PCT remain unexplored. ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3267548
更新日期:2010-01-01 00:00:00
abstract:PURPOSE:The authors use reduced-order constrained optimization (ROCO) to create clinically acceptable IMRT plans quickly and automatically for advanced lung cancer patients. Their new ROCO implementation works with the treatment planning system and full dose calculation used at Memorial Sloan-Kettering Cancer Center (M...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3575416
更新日期:2011-05-01 00:00:00
abstract:PURPOSE:To determine the accuracy and test-retest repeatability of fast radiofrequency (RF) transmit measurement approaches used in Dynamic Contrast Enhanced Magnetic Resonance Imaging (DCE-MRI). Spatial variation in the transmitted RF field introduces bias and increased variance in quantitative DCE-MRI metrics includi...
journal_title:Medical physics
pub_type: 杂志文章,多中心研究
doi:10.1002/mp.13518
更新日期:2019-06-01 00:00:00
abstract::This study evaluates the effects of respiratory motion on breast radiotherapy delivered using segmented multileaf collimator (SMLC) intensity modulation. An anthropomorphic breast phantom was constructed of polystyrene plates between which radiographic films were inserted. The phantom was mounted on a moving platform ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2405323
更新日期:2007-01-01 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
abstract::When parallel-plate chambers are used for dosimetry in electron fields, the AAPM dosimetry protocol recommends a value of 1.0 for the replacement correction factor, P(repl),pp,E, until further data become available. Here, P(repl),pp,E for five commercially available parallel-plate chambers was measured as a function o...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.596740
更新日期:1991-11-01 00:00:00