Abstract：
:When treating prostate cancer using high dose rate (HDR) brachytherapy, overdosing the rectal wall may lead to post-treatment rectal complications. An area of concern is related to how the rectal wall dose is calculated by treatment planning systems (TPSs). TPSs are used to calculate the dose delivered to the rectal wall, but they assume that the rectum is a water-equivalent homogeneous medium of infinite size and do not consider the effect that an air-filled "empty" rectal cavity would have on the dose absorbed along the rectal wall. The aim of this research is to quantify the effect that an air cavity has on the rectal wall dose, as its presence changes the backscatter conditions in the region. The MO Skin and RADFET dosimeters proved capable of measuring absolute dose with increasing distance from the HDR Ir-192 brachytherapy source. However, the anterior rectal wall doses measured by the MOSkin and RADFET in an empty rectal cavity were 14.7 +/- 0.2% and 13.7 +/- 0.6% lower than the dose measured in a homogeneous rectal phantom. Monte Carlo simulations corroborated the experimentally obtained results, reporting a -13.2 +/- 0.6% difference. The dose measured at the posterior wall of an empty rectal cavity was between 22% and 26% greater than the dose measured in a full rectal cavity. The heterogeneity of the rectal volume appears to have a significant effect on the rectal dose when compared to calculated rectal dose.
journal_name
Med Physjournal_title
Medical physicsauthors
Kwan IS,Wilkinson D,Cutajar D,Lerch M,Rosenfeld A,Howie A,Bucci J,Chin Y,Perevertaylo VLdoi
10.1118/1.3031111subject
Has Abstractpub_date
2009-01-01 00:00:00pages
224-32issue
1eissn
0094-2405issn
2473-4209journal_volume
36pub_type
杂志文章相关文献
MEDICAL PHYSICS文献大全abstract：PURPOSE:We describe the acceptance testing, commissioning, periodic quality assurance, and workflow procedures developed for the first clinically implemented magnetic resonance imaging-guided radiation therapy (MR-IGRT) system for real-time tracking and beam control. METHODS:The system utilizes real-time cine imaging ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.13002
更新日期：2018-05-28 00:00:00
abstract：PURPOSE:Wide bore CT scanners use extended field-of-view (eFOV) reconstruction algorithms to attempt to recreate tissue truncated due to large patient habitus. Radiation therapy planning systems rely on accurate CT numbers in order to correctly plan and calculate radiation dose. This study looks at the impact of eFOV r...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.13299
更新日期：2019-02-01 00:00:00
abstract：:Compared with slice-by-slice approaches for SPECT reconstruction, three-dimensional iterative methods provide a more accurate physical model and an improved SPECT image. Clinical application of these methods, however, is limited primarily to their computational demands. This paper investigates the methods for approxim...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.598030
更新日期：1997-09-01 00:00:00
abstract：PURPOSE:To design an efficient method for utilizing phase-space source models in the GPU-based Monte Carlo (MC) dose calculation engine gDPM. METHODS:In GPU-based MC algorithms, particles are transported in parallel on different threads. Particles of different types and energies can require significantly different exe...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4735565
更新日期：2012-06-01 00:00:00
abstract：:Several investigators have approximated the scatter component of digital radiographic images by applying a constant weighting factor to a convolved version of the detected image. The scatter approximation is then subtracted from the detected image. When a constant weighting factor is used, the scatter in areas of low ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.596088
更新日期：1987-05-01 00:00:00
abstract：:The dosimetric characteristics of a new dedicated radiosurgical treatment unit are systematically measured in terms of its percent depth dose, beam profile, and relative scatter factor. High-resolution diode detector, mini-ion-chamber detector, and conventional Kodak XV films are used to measure dosimetric data for a ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.1494830
更新日期：2002-08-01 00:00:00
abstract：:Modern linear accelerators contain multiple isocentres, defined by the mechanical motions of gantry, collimator and table. Isocentre localization for these motions has been performed using film and manual evaluations which have difficulty in relating the individual motions. To address these limitations, we have develo...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.2965950
更新日期：2008-07-01 00:00:00
abstract：PURPOSE:Silicon photodetectors are of significant interest for use in positron emission tomography (PET) systems due to their compact size, insensitivity to magnetic fields, and high quantum efficiency. However, one of their main disadvantages is fluctuations in temperature cause strong shifts in gain of the devices. P...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4903889
更新日期：2015-01-01 00:00:00
abstract：:In this study, we present an algorithm for three-dimensional (3-D) dose reconstruction using portal images obtained with an electronic portal imaging device (EPID). For this purpose an algorithm for 2-D dose reconstruction, which was previously developed in our institution, was adapted. The external contour of the pat...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.1589496
更新日期：2003-09-01 00:00:00
abstract：:A statistical analysis has been made of ionometrically measured parameters related to the central-axis output, the beam symmetry, the beam flatness, and the depth dose for the 6-MV x-ray beam from the Therac-6 linear accelerator. The means and coefficients of variation of the measurements are determined on a monthly b...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.595642
更新日期：1984-09-01 00:00:00
abstract：PURPOSE:Plastic scintillation detectors are used for dosimetry in small radiation fields with high dose gradients, e.g., provided by β-emitting sources like 106 Ru/106 Rh eye plaques. A drawback is a background signal caused by Cerenkov radiation generated by electrons passing the optical fibers (light guides) of this ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.12374
更新日期：2017-09-01 00:00:00
abstract：:An important aspect of the intensity modulated radiotherapy (IMRT) process is that of optimizing the beam intensity profiles. Most such methods use a comparison between the defined dose distribution (including prescription dose and dose limits for critical structures) and the current distribution. The comparison may i...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.1428756
更新日期：2002-01-01 00:00:00
abstract：PURPOSE:Upgrade and benchmarking of a research 4D treatment planning system (4DTPS) suitable for realistic patient treatment planning and treatment simulations taking into account specific requirements for scanned ion beam therapy, i.e., modeling of dose heterogeneities due to interplay effects and range changes caused...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4800802
更新日期：2013-05-01 00:00:00
abstract：PURPOSE:Scatter is a major factor degrading the image quality of cone beam computed tomography (CBCT). Conventional scatter correction strategies require handcrafted analytical models with ad hoc assumptions, which often leads to less accurate scatter removal. This study aims to develop an effective scatter correction ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.13583
更新日期：2019-07-01 00:00:00
abstract：PURPOSE:To develop a probabilistic treatment planning (PTP) method which is robust to systematic patient setup errors and to compare PTP plans with plans generated using a planning target volume (PTV) margin optimized to give the same target coverage probability as the PTP plan. METHODS:Plans adhering to the RTOG-0126...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3679856
更新日期：2012-02-01 00:00:00
abstract：:New in vivo dosimetry methods would be useful for clinical HDR brachytherapy. An implantable MOSFET Dose Verification System designed by Sicel Technologies, Inc. was examined for use with 192Ir HDR applications. This investigation demonstrated that varying the dose rate from 22 to 84 cGy/min did not change detector re...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3013574
更新日期：2008-12-01 00:00:00
abstract：PURPOSE:Over the last ten years, there has been an extensive growth in the development of microSPECT imagers. Most of the systems are based on the combination of conventional, relatively large gamma cameras with poor intrinsic spatial resolution and multipinhole collimators working in large magnification mode. Spatial ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4822621
更新日期：2013-11-01 00:00:00
abstract：:The use of dedicated magnetic resonance simulation (MR-SIM) platforms in Radiation Oncology has expanded rapidly, introducing new equipment and functionality with the overall goal of improving the accuracy of radiation treatment planning. However, this emerging technology presents a new set of challenges that need to ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.14695
更新日期：2021-01-01 00:00:00
abstract：:The purpose of this study is to understand the effect of pitch on raw data interpolation in multislice spiral/helical computed tomography (CT) and provide guidelines for scanner design and protocol optimization. Multislice spiral CT is mainly characterized by the three parameters: the number of detector arrays, the de...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.598804
更新日期：1999-12-01 00:00:00
abstract：:In many of brachytherapy procedures, a large amount of radioactive sources are used to deliver desired doses to the target volume. It is both the federal regulation recommendation (U.S. Nuclear Regulatory Commission, 10 CFR 35.432) and recommendations of the American Association of Physicists in Medicine (AAPM) [Kutch...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.2734723
更新日期：2007-06-01 00:00:00
abstract：:Magnetic resonance images can be compromised by constant frequency (CF) noise, such as radio frequency (RF) noise. We investigate the effects of CF noise in four imaging methods with non-uniform k-space sampling: single-shot echo-planar imaging (EPI) with sinusoidal readout gradients, phase-encoded echo-planar spectro...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.1496096
更新日期：2002-08-01 00:00:00
abstract：:A contrast-detail (CD) experiment was performed to study the effect of lossy compression on computed radiographic (CR) images. Digital CR images of a phantom were compressed by quantizing the full-frame discrete cosine transform and Huffman encoding the result. Since low-contrast detectability is directly linked to an...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.597489
更新日期：1995-06-01 00:00:00
abstract：INTRODUCTION:Ultrasound (US) guidance of the prostate has long been conducted using a transabdominal (TA) approach. More recently, a transperineal (TP) approach has been made available for image guidance. Our aim was to determine if both methods produced similar alignments within the same patients. MATERIALS AND METHO...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.14522
更新日期：2020-12-01 00:00:00
abstract：PURPOSE:To overcome the problem of organ motion in intensity-modulated radiation therapy (IMRT), gated IMRT is often used for the treatment of lung cancer. In this study, the authors investigated the accuracy of the delivered monitor units (MUs) from each segment during gated IMRT using a two-dimensional detector array...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3310806
更新日期：2010-03-01 00:00:00
abstract：PURPOSE:Although x-ray projection mammography has been very effective in early detection of breast cancer, its utility is reduced in the detection of small lesions that are occult or in dense breasts. One drawback is that the inherent superposition of parenchymal structures makes visualization of small lesions difficul...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3312435
更新日期：2010-03-01 00:00:00
abstract：:In this report we describe an improvement upon the design by Stanton and Lightfoot for a simple photographic null method to determine the kVp of a diagnostic region x-ray source. The new version has two primary advantages over the Ardran and Crooks design in that it is both simpler and less expensive to produce. ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.595716
更新日期：1985-03-01 00:00:00
abstract：:A very important issue in contemporary inverse treatment radiotherapy planning is the specification of proper dose-volume constraints limiting the treatment planning algorithm from delivering high doses to the normal tissue surrounding the tumor. Recently we have proposed a method called reverse mapping of normal tiss...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.2198307
更新日期：2006-09-01 00:00:00
abstract：:It is shown that in narrow monoenergetic photon beams under conditions of lateral electron disequilibrium, primary absorbed dose P(r) is a simple function of beam radius r: P(r) = P lambda.(1 - e(-gamma.r)), where P lambda is the primary dose in broad beams for which complete lateral electron equilibrium exists, and g...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.596741
更新日期：1991-07-01 00:00:00
abstract：PURPOSE:To evaluate a simple, semi-automated lung mass estimation method on CT scans from a variety of acquisition techniques for mass correction of MIRD dose estimates. METHODS:CT scans from ten patients undergoing stereotactic body radiation therapy treatment planning on a GE DST PET/CT scanner were analyzed retrosp...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4734654
更新日期：2012-06-01 00:00:00
abstract：PURPOSE:Magnetic resonance imaging (MRI) is increasingly used for radiotherapy target delineation, image guidance, and treatment response monitoring. Recent studies have shown that an entire external x-ray radiotherapy treatment planning (RTP) workflow for brain tumor or prostate cancer patients based only on MRI refer...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4958677
更新日期：2016-08-01 00:00:00
