Abstract:
:One of the methods currently being used to treat choroidal melanoma employs an episcleral plaque containing I-125 radioactive seeds. However, comprehensive dosimetry studies on the plaque are scarce and controversial. For this work, we use film to study the dosimetry outside the lip of the gold shield of the eye plaque. This lip around the gold shield was made to protect the critical structures behind and adjacent to the lesion. Since the changes of energy spectrum of I-125 in tissue are negligible, film dosimetry seems to be a logical choice because of high spatial resolution required around the lip of the gold plaque. For this study, we first established an H and D curve with dose expressed in a unit of specific dose rate constant. This avoids absolute dose measurements. All film density measurements are made with a 1-mm aperture scan, normalized to the density at the prescription point for tumor of 3-5-mm apical height, i.e., 5 mm from the interior surface of sclera, and converted to percentage isodose curves. With a gold shield, it is found that when the plaque is placed against the optical nerve, the optical disk and macula, located at 2 mm outside the lip, on the exterior surface of sclera, may receive 85% of the prescription dose for a 12-mm plaque and 58% for a 16-mm plaque. For tumors of 8-mm apical height, the optical nerve would receive more than the prescription dose.
journal_name
Med Physjournal_title
Medical physicsauthors
Wu A,Krasin Fdoi
10.1118/1.596556subject
Has Abstractpub_date
1990-09-01 00:00:00pages
843-6issue
5eissn
0094-2405issn
2473-4209journal_volume
17pub_type
杂志文章相关文献
MEDICAL PHYSICS文献大全abstract::The use of electronic portal imaging devices (EPIDs) is a promising method for the dosimetric verification of external beam, megavoltage radiation therapy-both pretreatment and in vivo. In this study, a previously developed EPID back-projection algorithm was modified for IMRT techniques and applied to an amorphous sil...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2147744
更新日期:2006-02-01 00:00:00
abstract::The gamma-ray dose component of a d(80) + Be neutron beam was measured with a 6Li-shielded Geiger-Mueller counter in a tissue-equivalent liquid phantom. The proportion of gamma-ray dose to total dose increased from 0.07 near the surface to 0.09 at 25 cm depth. Due to thermal neutron sensitivity, the G-M count rate inc...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.594571
更新日期:1979-05-01 00:00:00
abstract:PURPOSE:For the purpose of size-specific dose estimation, information regarding patient attenuation is required. The purpose of this work is to describe a method for measuring patient attenuation and expressing the results in terms of a water cylinder, with cross sectional area A(w), which would absorb the same average...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4754303
更新日期:2012-11-01 00:00:00
abstract::The contribution of a commercially available diode matrix (MapCHECK, provided by Sun Nuclear, Melbourne, FL) for the commissioning procedures of the voxel based Monte Carlo (VMC++) algorithm for electron beams of MasterPlan treatment planning system was investigated. The attention is mainly focused on the calculation ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3081414
更新日期:2009-04-01 00:00:00
abstract::Using superior localization and immobilization methods, stereotactic radiosurgery is capable of delivering spheres of dose as small as a few millimetres in diameter to intracranial targets. For targets abutting critical structures, the most conformal treatments minimize adverse radiation side effects and it is importa...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2965910
更新日期:2008-07-01 00:00:00
abstract:PURPOSE:Automated segmentation could improve the efficiency of modeling-based pelvic organ prolapse (POP) evaluations. However, segmentation performance is limited by the blurry soft tissue boundaries. In this study, we aimed to present a hybrid solution for uterus, rectum, bladder, and levator ani muscle segmentation ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.14377
更新日期:2020-09-01 00:00:00
abstract:PURPOSE:The x-ray performance evaluation of digital x-ray detectors is based on the calculation of the modulation transfer function (MTF), the noise power spectrum (NPS), and the resultant detective quantum efficiency (DQE). The flat images used for the extraction of the NPS should not contain any fixed pattern noise (...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3664003
更新日期:2011-12-01 00:00:00
abstract::High false-positive (FP) rate remains to be one of the major problems to be solved in CAD study because too many false-positively cued signals will potentially degrade the performance of detecting true-positive regions and increase the call-back rate in CAD environment. In this paper, we proposed a novel classificatio...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1344203
更新日期:2001-02-01 00:00:00
abstract:PURPOSE:This study introduces a new hybrid ZTE/Dixon MR-based attenuation correction (MRAC) method including bone density estimation for PET/MRI and quantifies the effects of bone attenuation on metastatic lesion uptake in the pelvis. METHODS:Six patients with pelvic lesions were scanned using fluorodeoxyglucose (18F-...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.12122
更新日期:2017-03-01 00:00:00
abstract::The introduction of negative pions into cancer therapy has required the construction of large new proton accelerators together with special magnetic systems to form and direct the pion beam to a patient. A summary is presented of the fundamental properties of pions and of the methods used to study the therapeutic beam...
journal_title:Medical physics
pub_type: 杂志文章,评审
doi:10.1118/1.594868
更新日期:1981-05-01 00:00:00
abstract::In the last 30 years, thousands of basic or clinical studies have been devoted to atherosclerosis or to the problem of restenosis after angioplasty. In these studies, axial stresses in the vessel wall have received practically no attention, contrary to circumferential stress and purely biological aspects. Based on a r...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1844432
更新日期:2005-02-01 00:00:00
abstract:PURPOSE:Four-dimensional volumetric modulated arc therapy (4D VMAT) and four-dimensional intensity-modulated radiotherapy (4D IMRT) are developing radiation therapy treatment strategies designed to maximize dose conformality, minimize normal tissue dose, and deliver the treatment as efficiently as possible. The patient...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.12778
更新日期:2018-04-01 00:00:00
abstract:PURPOSE:The segmentation accuracy of medical images was improved by increasing the number of training samples using a local image warping technique. The performance of the proposed method was evaluated in the segmentation of breast masses, prostate and brain tumors, and lung nodules. METHODS:We propose a simple data a...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.14651
更新日期:2020-12-10 00:00:00
abstract:PURPOSE:Osteoporosis is a common bone disease associated with increased risk of low-trauma fractures leading to substantial morbidity, mortality, and financial costs. Clinically, osteoporosis is defined by low bone mineral density (BMD); however, increasing evidence suggests that trabecular bone (TB) microarchitectural...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4928481
更新日期:2015-09-01 00:00:00
abstract::Skeletal dosimetry based on microCT images of trabecular bone has recently been introduced to calculate the red bone marrow (RBM) and the bone surface cell (BSC) equivalent doses in human phantoms for external exposure to photons. In order to use the microCT images for skeletal dosimetry, spongiosa voxels in the skele...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3242266
更新日期:2009-11-01 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::The proper evaluation of the accuracy of a new computer program for radiation-therapy dosimetry requires consideration of both the mathematical algorithm used in the program and the performance required in clinical applications. As an example, our evaluation of the irregular-fields dosimetry program currently marketed...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.594344
更新日期:1977-11-01 00:00:00
abstract::Luminance scatter fractions were measured for patients and phantoms in various regions of the chest film. Scatter fractions were found to be highly variable, being quite high in the regions of the chest with a large equivalent tissue thickness (e.g. mediastinum, chest wall, and subdiaphragmatic areas). For example, ap...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.595027
更新日期:1981-09-01 00:00:00
abstract::Monte Carlo (MC) simulations were performed to estimate brachytherapy dose distributions for Collaborative Ocular Melanoma Study (COMS) eye plaques. Brachytherapy seed models 200, 6711, and CS-1 Rev2 carrying 103Pd, 125I, and 131Cs radionuclides, respectively, were modeled and benchmarked against previously published ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2940604
更新日期:2008-07-01 00:00:00
abstract::Two side-by-side energy windows are sometimes employed in quantitative single photon emission computed tomography (SPECT) studies. The count-rate losses at high activities for a GE400AT camera were measured in such a dual-window-acquisition mode by imaging a decaying source composed of a hot sphere within a warm cylin...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.597008
更新日期:1993-07-01 00:00:00
abstract::The last 50 years have seen great advances in the accuracy of external beam radiation therapy. Geometrical uncertainties have been reduced from a centimeter or more in presimulation, skin-mark guided days to 1-2 mm in today's image-guided radiation therapy treatments. Medical physicists, with the support and guidance ...
journal_title:Medical physics
pub_type: 杂志文章,评审
doi:10.1118/1.2836420
更新日期:2008-03-01 00:00:00
abstract:PURPOSE:To formulate convex planning objectives of treatment plan multicriteria optimization with explicit relationships to the dose-volume histogram (DVH) statistics used in plan quality evaluation. METHODS:Conventional planning objectives are designed to minimize the violation of DVH statistics thresholds using pena...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.12146
更新日期:2017-06-01 00:00:00
abstract::Heat therapies such as hyperthermia and thermoablation are very promising approaches in the treatment of cancer. Compared with available hyperthermia modalities, magnetic fluid hyperthermia (MFH) yields better results in uniform heating of the deeply situated tumors. In this approach, fluid consisting of superparamagn...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3106343
更新日期:2009-05-01 00:00:00
abstract::Imaging parameters associated with a clinical magnetic resonance imaging (MRI) system, evaluated with the use of simple and inexpensive phantoms, are described in evaluation of a clinical MRI system. Images, obtained with a Diasonics 0.35-T MRI system using an elliptical whole-body radio frequency coil, are presented ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.595894
更新日期:1986-07-01 00:00:00
abstract::A direct data link between a CT scanner and a radiation treatment planning system has been developed. The link transmits the data serially over a coaxial cable using the pseudo-paper-tape punch and reader (serial PIO) interfaces. The data transmission rate with error-check is approximately 25,000 8-bit bytes/s. This t...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.594536
更新日期:1979-09-01 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:Respiratory motion compensation in PET/CT and PET/MRI is essential as motion is a source of image degradation (motion blur, attenuation artifacts). In previous work, we developed a direct method for joint image reconstruction/motion estimation (JRM) for attenuation-corrected (AC) respiratory-gated PET, which us...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.12253
更新日期:2017-06-01 00:00:00
abstract:PURPOSE:Particle therapy is becoming increasingly available world-wide for precise tumor targeting, its favorable depth dose deposition, and increased biological damage to tumor tissue compared to conventional photon therapy. As demand increases for improved robustness and conformality, next-generation secondary dose c...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.14417
更新日期:2020-10-01 00:00:00
abstract:PURPOSE:Accurate segmentation of lungs with severe interstitial lung disease (ILD) in thoracic computed tomography (CT) is an important and difficult task in the development of computer-aided diagnosis (CAD) systems. Therefore, we developed in this study a texture analysis-based method for accurate segmentation of lung...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3222872
更新日期:2009-10-01 00:00:00
abstract:PURPOSE:When designing a collimation system for pencil beam spot scanning proton therapy, a decision must be made whether or not to rotate, or focus, the collimator to match beamlet deflection as a function of off-axis distance. If the collimator is not focused, the beamlet shape and fluence will vary as a function of ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.14139
更新日期:2020-07-01 00:00:00