Abstract:
PURPOSE:As radiation therapy evolves toward more adaptive techniques, image guidance plays an increasingly important role, not only in patient setup but also in monitoring the delivered dose and adapting the treatment to patient changes. This study aimed to validate a method for evaluation of delivered intensity modulated radiotherapy (IMRT) dose based on multimodal deformable image registration (dir) for prostate treatments. METHODS:A pelvic phantom was scanned with CT and cone-beam computed tomography (CBCT). Both images were digitally deformed using two realistic patient-based deformation fields. The original CT was then registered to the deformed CBCT resulting in a secondary deformed CT. The registration quality was assessed as the ability of the dir method to recover the artificially induced deformations. The primary and secondary deformed CT images as well as vector fields were compared to evaluate the efficacy of the registration method and it's suitability to be used for dose calculation. plastimatch, a free and open source software was used for deformable image registration. A B-spline algorithm with optimized parameters was used to achieve the best registration quality. Geometric image evaluation was performed through voxel-based Hounsfield unit (HU) and vector field comparison. For dosimetric evaluation, IMRT treatment plans were created and optimized on the original CT image and recomputed on the two warped images to be compared. The dose volume histograms were compared for the warped structures that were identical in both warped images. This procedure was repeated for the phantom with full, half full, and empty bladder. RESULTS:The results indicated mean HU differences of up to 120 between registered and ground-truth deformed CT images. However, when the CBCT intensities were calibrated using a region of interest (ROI)-based calibration curve, these differences were reduced by up to 60%. Similarly, the mean differences in average vector field lengths decreased from 10.1 to 2.5 mm when CBCT was calibrated prior to registration. The results showed no dependence on the level of bladder filling. In comparison with the dose calculated on the primary deformed CT, differences in mean dose averaged over all organs were 0.2% and 3.9% for dose calculated on the secondary deformed CT with and without CBCT calibration, respectively, and 0.5% for dose calculated directly on the calibrated CBCT, for the full-bladder scenario. Gamma analysis for the distance to agreement of 2 mm and 2% of prescribed dose indicated a pass rate of 100% for both cases involving calibrated CBCT and on average 86% without CBCT calibration. CONCLUSIONS:Using deformable registration on the planning CT images to evaluate the IMRT dose based on daily CBCTs was found feasible. The proposed method will provide an accurate dose distribution using planning CT and pretreatment CBCT data, avoiding the additional uncertainties introduced by CBCT inhomogeneity and artifacts. This is a necessary initial step toward future image-guided adaptive radiotherapy of the prostate.
journal_name
Med Physjournal_title
Medical physicsauthors
Moteabbed M,Sharp GC,Wang Y,Trofimov A,Efstathiou JA,Lu HMdoi
10.1118/1.4903292subject
Has Abstractpub_date
2015-01-01 00:00:00pages
196-205issue
1eissn
0094-2405issn
2473-4209journal_volume
42pub_type
杂志文章相关文献
MEDICAL PHYSICS文献大全abstract:PURPOSE:The ionizing radiation imparted to patients during computed tomography exams is raising concerns. This paper studies the performance of a scheme called dose reduction using prior image constrained compressed sensing (DR-PICCS). The purpose of this study is to characterize the effects of a statistical model of x...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4773866
更新日期:2013-02-01 00:00:00
abstract:PURPOSE:The purpose of this study is to estimate the effect of edema, developed during implant procedure, on tumor cell surviving fraction(SF) and tumor control probability(TCP) in the patients of prostate cancer who underwent 131 Cs permanent seed implants. METHODS:The impact of edema on SF and TCP, was calculated us...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4735061
更新日期:2012-06-01 00:00:00
abstract:PURPOSE:A long-standing conundrum is why photoacoustic tomography (PAT) possesses the unique ability to produce images devoid of speckle artifacts while all other coherent imaging technologies do not. METHODS:In this paper, we explain the inherent mechanism that suppresses speckle in PAT, and the analysis was validate...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3187231
更新日期:2009-09-01 00:00:00
abstract::The performance of a diode array (Profiler) was evaluated by comparing its enhanced dynamic wedge (EDW) profiles measured at various depths with point measurements using a 0.03 cm3 ionization chamber on a commercial linear accelerator. The Profiler, which covers a 22.5 cm width, was used to measure larger field widths...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.598019
更新日期:1997-07-01 00:00:00
abstract::When an (exposure) calibrated ionization chamber is used for the determination of absorbed dose from a photon beam, the reading of the instrument must be multiplied by a number of factors, one of which is an attenuation correction for phantom material displaced by the chamber. the magnitude of this correction must dep...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.594817
更新日期:1980-11-01 00:00:00
abstract:PURPOSE:Target localization accuracy of cone-beam CT (CBCT) images used in radiation treatment of respiratory disease sites is affected by motion artifacts (blurring and streaking). The authors have previously reported on a method of respiratory motion correction in thoracic CBCT at end expiration (EE). The previous re...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4896101
更新日期:2014-10-01 00:00:00
abstract::Backscatter factors for kVps and half-value layers typical of mammographic beams have been determined as a function of beam diameter and half-value layer. The method utilized thin TLD-100 chips with the scattering medium alternately present and absent. Results indicate that the field-size dependence of the backscatter...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.594312
更新日期:1977-09-01 00:00:00
abstract::We applied Monte Carlo methods for the simulation of x-ray scattering in water phantoms. The phantom thickness was varied from 5 to 20 cm, and the monoenergetic incident x rays were varied from 15 to 100 keV. Eight screen pairs and a total absorption system were used as x-ray receptors. We determined the angular, spec...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.595771
更新日期:1985-03-01 00:00:00
abstract:PURPOSE:In current clinical practice, there is no integrated 3D ultrasound (3DUS) guidance system clinically available for breast brachytherapy. In this study, the authors present a novel robot-assisted 3DUS system for real-time planning and guidance of breast interstitial high dose rate (HDR) brachytherapy treatment. ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4934832
更新日期:2015-12-01 00:00:00
abstract::In previous work it has been shown that a standard backpropagation neural network can be trained to reconstruct sections of single photon emission computed tomography (SPECT) images based on the planar image projections as inputs. In this study, it is demonstrated that an artificial neural network (ANN) trained on a s...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.597586
更新日期:1995-05-01 00:00:00
abstract::The verification of dose distributions with high dose gradients as appearing in brachytherapy or stereotactic radiotherapy for example, calls for dosimetric methods with sufficiently high spatial resolution. Polymer gels in combination with a MR or optical scanner as a readout device have the potential of performing t...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2898173
更新日期:2008-05-01 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::Single kernel scatter correction algorithms are based on the model that the scatter field can be predicted by convolution of the primary intensity (Iprim) with a spatially invariant scatter point-spread function (PSF). Practical limitations (Iprim unknown) suggest the substitution of the total detected intensity (Idet...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.597297
更新日期:1994-02-01 00:00:00
abstract:PURPOSE:To present a noninvasive technique for directly measuring the CT bow-tie filter attenuation with a linear array x-ray detector. METHODS:A scintillator based x-ray detector of 384 pixels, 307 mm active length, and fast data acquisition (model X-Scan 0.8c4-307, Detection Technology, FI-91100 Ii, Finland) was use...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4932364
更新日期:2015-11-01 00:00:00
abstract:PURPOSE:Positron emission tomography (PET) is an important tool for nuclear medical imaging. It has been widely used in clinical diagnosis, scientific research, and drug testing. PET is a kind of emission computed tomography. Its basic imaging principle is to use the positron annihilation radiation generated by radionu...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.13804
更新日期:2019-11-01 00:00:00
abstract::Multimodality NIR spectroscopy systems offer the possibility of region-based vascular and molecular characterization of tissue in vivo. However, computationally efficient 3D image reconstruction algorithms specific to these image-guided systems currently do not exist. Image reconstruction is often based on finite-elem...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2795832
更新日期:2007-11-01 00:00:00
abstract:PURPOSE:Repeated brain MRI scans are performed in many clinical scenarios, such as follow up of patients with tumors and therapy response assessment. In this paper, the authors show an approach to utilize former scans of the patient for the acceleration of repeated MRI scans. METHODS:The proposed approach utilizes the...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4928148
更新日期:2015-09-01 00:00:00
abstract::This study compared air exposures during conventional dental and maxillofacial radiography and similar views using free-focus radiography with conventional image receptors. The results show that periapical type surveys on nonscreen film placed extraorally or in the buccal fold may be carried out with an exposure to th...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.594690
更新日期:1980-07-01 00:00:00
abstract:PURPOSE:In fractionated radiation therapy, image guidance with daily tomographic imaging becomes more and more clinical routine. In principle, this allows for daily computation of the delivered dose and for accumulation of these daily dose distributions to determine the actually delivered total dose to the patient. How...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3697524
更新日期:2012-04-01 00:00:00
abstract:PURPOSE:Flattening filter free (FFF) beams generated by medical linear accelerators have recently started to be used in radiotherapy clinical practice. Such beams present fundamental differences with respect to the standard filter flattened (FF) beams, making the generally used dosimetric parameters and definitions not...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4754799
更新日期:2012-10-01 00:00:00
abstract::In this paper, we describe an algorithm to segment a needle from a three-dimensional (3D) ultrasound image by using two orthogonal two-dimensional (2D) image projections. Not only is the needle more conspicuous in a projected (volume-rendered) image, but its direction in 3D lies in the plane defined by the projection ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1538231
更新日期:2003-02-01 00:00:00
abstract::An investigation was performed of the changes in image quality and patient dose as a result of increasing filtration for fluoroscopy performed under automatic brightness control. Filtration was added either at the x-ray tube housing (i.e., scatter-free geometry) or adjacent to a tissue equivalent phantom simulating th...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.597906
更新日期:1997-03-01 00:00:00
abstract::In this work, we present a calcification-detection scheme that automatically localizes calcifications in a previously detected cluster in order to generate the input for a cluster-classification scheme developed in the past. The calcification-detection scheme makes use of three pieces of a priori information: the loca...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1559884
更新日期:2003-05-01 00:00:00
abstract::Currently, two classes of the computational phantoms have been developed for dosimetry calculation: (1) stylized (or mathematical) and (2) voxel (or tomographic) phantoms describing human anatomy through mathematical surface equations and three-dimensional labeled voxel matrices, respectively. Mathematical surface equ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2912178
更新日期:2008-06-01 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:PURPOSE:Contrast-enhanced imaging of the breast is frequently used in breast MRI and has recently become more common in mammography. The purpose of this study was to make single-scan contrast-enhanced imaging feasible for photon-counting breast CT (pcBCT) and to assess the spectral performance of a pcBCT scanner by eva...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.14133
更新日期:2020-07-01 00:00:00
abstract::Cone beam transmission CT (CB-CT) improves SPECT imaging by providing high-quality attenuation maps for attenuation compensation and for correlated SPECT and CT imaging. The present work measures the detection nonuniformity for CB-CT implemented with a gamma camera, and applies nonuniformity corrections to make CB-CT ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.596838
更新日期:1992-03-01 00:00:00
abstract::Inverse treatment planning of intensity-modulated radiation therapy (IMRT) is complicated by several sources of error, which can cause deviations of optimized plans from the true optimal solution. These errors include the systematic and convergence error, the local minima error, and the optimizer convergence error. We...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2896070
更新日期:2008-05-01 00:00:00
abstract:PURPOSE:In this work, the fabrication, operation, and evaluation of a probe-format graphite calorimeter - herein referred to as Aerrow - as an absolute clinical dosimeter of high-energy photon beams while in the presence of a B = 1.5 T magnetic field is described. Comparable to a cylindrical ionization chamber (IC) in ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.13968
更新日期:2020-03-01 00:00:00
abstract:PURPOSE:The accuracy and precision of computed tomography (CT) pulmonary ventilation imaging with conventional CT scanners are limited by breathing variations. We propose a method to correct for the effect of breathing variations in CT ventilation imaging based on external respiratory signals acquired throughout a scan...
journal_title:Medical physics
pub_type: 临床试验,杂志文章
doi:10.1002/mp.12634
更新日期:2018-01-01 00:00:00