Abstract:
PURPOSE:Compton camera imaging (CCI) systems are currently under investigation for radiotherapy dose reconstruction and verification. The ability of such a system to provide real-time images during dose delivery will be limited by the computational speed of the image reconstruction algorithm. In this work, the authors present a fast and simple method by which to generate an initial back-projected image from acquired CCI data, suitable for use in a filtered back-projection algorithm or as a starting point for iterative reconstruction algorithms, and compare its performance to the current state of the art. METHODS:Each detector event in a CCI system describes a conical surface that includes the true point of origin of the detected photon. Numerical image reconstruction algorithms require, as a first step, the back-projection of each of these conical surfaces into an image space. The algorithm presented here first generates a solution matrix for each slice of the image space by solving the intersection of the conical surface with the image plane. Each element of the solution matrix is proportional to the distance of the corresponding voxel from the true intersection curve. A threshold function was developed to extract those pixels sufficiently close to the true intersection to generate a binary intersection curve. This process is repeated for each image plane for each CCI detector event, resulting in a three-dimensional back-projection image. The performance of this algorithm was tested against a marching algorithm known for speed and accuracy. RESULTS:The threshold-based algorithm was found to be approximately four times faster than the current state of the art with minimal deficit to image quality, arising from the fact that a generically applicable threshold function cannot provide perfect results in all situations. The algorithm fails to extract a complete intersection curve in image slices near the detector surface for detector event cones having axes nearly parallel to the image plane. This effect decreases the sum of the image, thereby also affecting the mean, standard deviation, and SNR of the image. All back-projected events associated with a simulated point source intersected the voxel containing the source and the FWHM of the back-projected image was similar to that obtained from the marching method. CONCLUSIONS:The slight deficit to image quality observed with the threshold-based back-projection algorithm described here is outweighed by the 75% reduction in computation time. The implementation of this method requires the development of an optimum threshold function, which determines the overall accuracy of the method. This makes the algorithm well-suited to applications involving the reconstruction of many large images, where the time invested in threshold development is offset by the decreased image reconstruction time. Implemented in a parallel-computing environment, the threshold-based algorithm has the potential to provide real-time dose verification for radiation therapy.
journal_name
Med Physjournal_title
Medical physicsauthors
Mundy DW,Herman MGdoi
10.1118/1.3519873subject
Has Abstractpub_date
2011-01-01 00:00:00pages
15-22issue
1eissn
0094-2405issn
2473-4209journal_volume
38pub_type
杂志文章相关文献
MEDICAL PHYSICS文献大全abstract:PURPOSE:The purpose of this study is to evaluate the feasibility of kilovoltage cone-beam CT (CBCT) images that are obtained with the Varian On-Board Imager in dose calculation at each radiation therapy. METHODS:CBCT images are commonly degraded by scattered radiations originating in the patient's body, and so the CT ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4734936
更新日期:2012-06-01 00:00:00
abstract::An adaptive linear element (Adaline) was developed to estimate the two-dimensional scatter exposure distribution in digital portable chest radiographs (DPCXR). DPCXRs and quantitative scatter exposure measurements at 64 locations throughout the chest were acquired for ten radiographically normal patients. The Adaline ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.596978
更新日期:1993-07-01 00:00:00
abstract::The dosimetry for radiocolloid therapy of cystic craniopharyngiomas is investigated. Analytical calculations based on the Loevinger and the Berger formulas for electrons and photons, respectively, are compared with Monte Carlo simulations. The role of the material of which the colloid introduced inside the craniophary...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1599653
更新日期:2003-09-01 00:00:00
abstract:PURPOSE:The aim of this study was to use MRI gel dosimetry to determine the dose profile of 50kV MAGNUM® X-ray tube, MOXTEK Inc., in order to calibrate small solid dosimeters of alanine, tooth enamel and LiF-TLDs, commonly used in clinical quality assurance and datation dosimetry. METHODS:MAGIC-f polymer gel was kept ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4735203
更新日期:2012-06-01 00:00:00
abstract:PURPOSE:There is significant current interest in the use of biological image guidance in radiotherapy planning. In lung-cancer treatment, tumor motion due to respiration is known to be a limitation. This is particularly true in PET, where image data are collected over a number of minutes. An in-house-developed 4D PET a...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3276776
更新日期:2010-02-01 00:00:00
abstract:PURPOSE:Design and optimization of medical imaging systems benefit from accurate theoretical modeling that identifies the physical factors governing image quality, particularly in the early stages of system development. This work extends Fourier metrics of imaging performance and detectability index (d') to tomosynthes...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3560428
更新日期:2011-04-01 00:00:00
abstract:PURPOSE:The overall goal of this work is to improve the computed tomography (CT) image quality for patients with metal implants or fillings by completing the missing kilovoltage (kV) projection data with selectively acquired megavoltage (MV) data that do not suffer from photon starvation. When both of these imaging sys...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4901551
更新日期:2014-12-01 00:00:00
abstract::The dose distribution for an ovoid with a new tungsten shielding design was determined using Monte Carlo simulation. Standard Cesium-137 tube sources, tungsten shielding, and aluminum ovoid applicator were each modeled as a collection of solid objects. Dose was calculated in planes above, below, in front of, and on th...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.598459
更新日期:1998-12-01 00:00:00
abstract:PURPOSE:The objectives of this study were (a) to devise a technique for measuring quantum noise in clinical body computed tomography (CT) images and (b) to develop a model for predicting that noise with high accuracy. METHODS:The study included 83 clinical image sets at two dose levels (clinical and 50% reduced dose l...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4938588
更新日期:2016-01-01 00:00:00
abstract:PURPOSE:Stereotactic body radiation therapy (SBRT) is a radiotherapy technique which uses high dose fractions with multiple coplanar and noncoplanar beams. Due to the large fractional doses, treatments are typically protracted and there are more fields than in conventional radiation treatment schemes. The effect of tem...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4709605
更新日期:2012-06-01 00:00:00
abstract:PURPOSE:Since the first publications on intensity modulated radiation therapy (IMRT) in the early 1980s almost all efforts have been focused on fairly time consuming dynamic or segmental multileaf collimation. With narrow fast scanned photon beams, the flexibility and accuracy in beam shaping increases, not least in co...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3615059
更新日期:2011-08-01 00:00:00
abstract:PURPOSE:To develop a novel three-dimensional (3D) hybrid-encoding framework using compressed sensing (CS) and Toeplitz encoding with variable phase-scrambled radio-frequency (RF) excitation, which has the following advantages: low power deposition of RF pulses, reduction of the signal dynamic range, no additional hardw...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.13987
更新日期:2020-04-01 00:00:00
abstract:PURPOSE:Cone-beam computed tomography (CBCT) is an increasingly utilized imaging modality for the diagnosis and treatment planning of the patients with craniomaxillofacial (CMF) deformities. Accurate segmentation of CBCT image is an essential step to generate three-dimensional (3D) models for the diagnosis and treatmen...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4868455
更新日期:2014-04-01 00:00:00
abstract::Electron-beam characteristics of a Philips SL25 linear accelerator have been studied. Central-axis percentage depth doses, cross-beam profiles and beam output factors of 6-, 10-, and 20-MeV beams, selected from the available energy range of 4 to 22 MeV, are reported in this paper. The main thrust of this work is to de...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.596471
更新日期:1990-07-01 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:A series of examples are presented in which potential errors in the delivery of radiation therapy were prevented through use of incident learning. These examples underscore the value of reporting near miss incidents. METHODS:Using a departmental incident learning system, eight incidents were noted over a two-y...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4760774
更新日期:2012-11-01 00:00:00
abstract:PURPOSE:A preobject grid can reduce and correct scatter in cone beam computed tomography (CBCT). However, half of the signal in each projection is blocked by the grid. A synchronized moving grid (SMOG) has been proposed to acquire two complimentary projections at each gantry position and merge them into one complete pr...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4937934
更新日期:2016-01-01 00:00:00
abstract:PURPOSE:Treatments like radiotherapy and focused ultrasound in the abdomen require accurate motion tracking, in order to optimize dosage delivery to the target and minimize damage to critical structures and healthy tissues around the target. 4D ultrasound is a promising modality for motion tracking during such treatmen...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4890091
更新日期:2014-08-01 00:00:00
abstract::The purpose of this work is to calculate the dose perturbations due to the presence of iodine contrast media in catheter-based intravascular brachytherapy (IVBT). The EGSnrc Monte Carlo system was used to perform the calculation for the two most commonly used beta and gamma sources (90Sr and 192Ir as well as for a var...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1367279
更新日期:2001-05-01 00:00:00
abstract::Empirical functions that describe primary beam profiles for radiotherapy treatment planning systems generally account for finite source size only on beams unmodified by blocks, wedges, or compensating filters. To incorporate the effects of extended sources on such modified beams and to treat the effect of an extended ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.596222
更新日期:1988-09-01 00:00:00
abstract:PURPOSE:Radiotherapy, especially with charged particles, is sensitive to executional and preparational uncertainties that propagate to uncertainty in dose and plan quality indicators, for example, dose-volume histograms (DVHs). Current approaches to quantify and mitigate such uncertainties rely on explicitly computed e...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.14414
更新日期:2020-10-01 00:00:00
abstract:PURPOSE:Recent guidance by The Joint Commission and CRCPD recommendations require establishing CT reference dose levels (RDLs) for clinical protocols and recording CT dose metrics in the patient's medical record. This presentation addresses which dose values in the CT report should be recorded for the purposes of monit...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4734773
更新日期:2012-06-01 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::The concept of equivalent uniform dose (EUD) has been suggested as a means to quantitatively consider heterogeneous dose distributions within targets. Tumor cell density/function is typically assumed to be uniform. We herein propose to use 18F-labeled 2-deoxyglucose (FDG) positron emission tomography (PET) tumor imagi...
journal_title:Medical physics
pub_type: 临床试验,杂志文章
doi:10.1118/1.1779372
更新日期:2004-09-01 00:00:00
abstract:PURPOSE:To improve the performance of a computer-aided detection (CAD) system for mass detection by using four-view information in screening mammography. METHODS:The authors developed a four-view CAD system that emulates radiologists' reading by using the craniocaudal and mediolateral oblique views of the ipsilateral ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3560462
更新日期:2011-04-01 00:00:00
abstract:PURPOSE:Stringent quality assurance is required in MRI breast screening to ensure that different scanners and imaging protocols reach similar diagnostic performance. The authors propose a methodology, based on power spectrum analysis (PSA), to evaluate spatial resolution in clinical images. To demonstrate this approach...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4966704
更新日期:2016-12-01 00:00:00
abstract::Effects of changes in the physics of EGSnrc compared to EGS4/PRESTA on energy deposition kernels for monoenergetic photons and on dose point kernels for beta sources in water are investigated. In the diagnostic energy range, Compton binding corrections were found to increase the primary energy fraction up to 4.5% at 3...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1861412
更新日期:2005-03-01 00:00:00
abstract:PURPOSE:The authors investigated the potential of optimized noncoplanar irradiation trajectories for volumetric modulated arc therapy (VMAT) treatments of nasopharyngeal patients and studied the trade-off between treatment plan quality and delivery time in radiation therapy. METHODS:For three nasopharyngeal patients, ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4914863
更新日期:2015-05-01 00:00:00
abstract:PURPOSE:To eliminate or reduce the error to Pareto optimality that arises in Pareto surface navigation when the Pareto surface is approximated by a small number of plans. METHODS:The authors propose to project the navigated plan onto the Pareto surface as a postprocessing step to the navigation. The projection attempt...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4930252
更新日期:2015-10-01 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