Abstract:
PURPOSE:An improved method of image guidance for lung tumor biopsies could help reduce the high rate of false negatives. The aim of this work is to optimize the geometry of the scanning-beam digital tomography system (SBDX) for providing real-time 3D tomographic reconstructions for target verification. The unique geometry of the system requires trade-offs between patient dose, imaging field of view (FOV), and tomographic angle. METHODS:Tomosynthetic angle as a function of tumor-to-detector distance was calculated. Monte Carlo Software (PCXMC) was used to calculate organ doses and effective dose for source-to-detector distances (SDDs) from 90 to 150 cm, patient locations with the tumor at 20 cm from the source to 20 cm from the detector, and FOVs centered on left lung and right lung as well as medial and distal peripheries of the lungs. These calculations were done for two systems, a SBDX system and a GE OEC-9800 C-arm fluoroscopic unit. To evaluate the dose effect of the system geometry, results from PCXMC were calculated using a scan of 300 mAs for both SBDX and fluoroscopy. The Rose Criterion was used to find the fluence required for a tumor SNR of 5, factoring in scatter, air-gap, system geometry, and patient position for all models generated with PCXMC. Using the calculated fluence for constant tumor SNR, the results from PCXMC were used to compare the patient dose for a given SNR between SBDX and fluoroscopy. RESULTS:Tomographic angle changes with SDD only in the region near the detector. Due to their geometry, the source array and detector have a peak tomographic angle for any given SDD at a source to tumor distance that is 69.7% of the SDD assuming constant source and detector size. Changing the patient location in order to increase tomographic angle has a significant effect on organ dose distribution due to geometrical considerations. With SBDX and fluoroscopy geometries, the dose to organs typically changes in an opposing manner with changing patient location. When tumor SNR is held constant (i.e., x-ray fluence is scaled appropriately), SBDX gives 2-10 times less dose than fluoroscopy for the same conditions within the typical range of patient locations. The relative position of the patient (as a percent of SDD) has a much more significant impact on dose than either SDD or patient position. The patient position providing the minimum dose for a given tumor SNR and SDD is approximately the same as the position of maximum tomographic angle. CONCLUSIONS:SBDX offers a significant dose advantage over currently used C-arm fluoroscopy. The patient location with lowest dose coincides with the location of maximum tomographic angle. In order to provide adequate space for the patient and for the pulmonologists' equipment, a SDD of 100 cm is recommended.
journal_name
Med Physjournal_title
Medical physicsauthors
Nelson G,Yoon S,Krishna G,Wilfley B,Fahrig Rdoi
10.1118/1.4826159subject
Has Abstractpub_date
2013-11-01 00:00:00pages
111917issue
11eissn
0094-2405issn
2473-4209journal_volume
40pub_type
杂志文章相关文献
MEDICAL PHYSICS文献大全abstract::Depth dose distributions for a d(14)Be neutron beam, measured separately for total and gamma absorbed dose, are presented for nine tissue substitutes and for two field sizes. These data are used to examine methods to transform depth dose curves from one material to another. Best results are found when the local depths...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.595695
更新日期:1985-05-01 00:00:00
abstract::Deformable image registration is an important tool for image-guided radiotherapy. Physics-model-based deformable image registration using finite element analysis is one of the methods currently being investigated. The calculation accuracy of finite element analysis is dependent on given boundary conditions, which are ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1774131
更新日期:2004-09-01 00:00:00
abstract::An analytic representation proposed for the relative intensity distribution of the extra-focal source in a two-component x-ray source model serves as the basis for calculation. From this representation, a closed-form expression for head scatter factors defined on the central beam axis is derived by integrating over th...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.597494
更新日期:1995-12-01 00:00:00
abstract:PURPOSE:To implement the DMAIC (Define-Measure-Analyze-Improve-Control) can be used for customizing the patient-specific QA by designing site-specific range tolerances. METHODS:The DMAIC framework (process flow diagram, cause and effect, Pareto chart, control chart, and capability analysis) were utilized to determine ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.12721
更新日期:2018-02-01 00:00:00
abstract::A simple noninvasive method is described for determining the backscatter to a monitor chamber of a medical accelerator based on the measurement of charge deposited in the target. This method is compared quantitatively to the more elaborate telescopic method for photon beams of 6 MV and 15 MV on linear accelerators hav...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.598203
更新日期:1998-03-01 00:00:00
abstract:PURPOSE:To measure patient-specific maximum skin dose (MSD) associated with CT fluoroscopy (CTF) lung biopsies and to compare measured MSD with the MSD estimated from phantom measurements, as well as with the CTDIvol of patient examinations. METHODS:Data from 50 patients with lung lesions who underwent a CT fluoroscop...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4884231
更新日期:2014-07-01 00:00:00
abstract::A new approach to the calculation of the x-ray spectrum emerging from an x-ray tube is proposed. Theoretical results for the bremsstrahlung cross section appearing in the literature are summarized. Four different treatments of electron penetration, based on the work presented in Part I, are then used to generate brems...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2734726
更新日期:2007-06-01 00:00:00
abstract:PURPOSE:To develop a new biological equivalent dose (BED) formulism that includes repair, repopulation and resensitization (redistribution and reoxygenation), and can be used to calculate prescribed dose for permanent implant with Cs-131. METHODS:Because of lack of sufficient clinical data, the prescribed dose with ne...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4735551
更新日期:2012-06-01 00:00:00
abstract:PURPOSE:To develop an automatic segmentation algorithm integrating imaging information from computed tomography (CT), positron emission tomography (PET), and magnetic resonance imaging (MRI) to delineate target volume in head and neck cancer radiotherapy. METHODS:Eleven patients with unresectable disease at the tonsil...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4928485
更新日期:2015-09-01 00:00:00
abstract::Permanent implantation of 125I (iodine) or 103Pd (palladium) sources is a popular treatment option in the management of early stage prostate cancer. New sources are being developed, some of which are being marketed for different clinical applications. A new technique of adjuvant stereotactic permanent seed breast impl...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3006151
更新日期:2008-12-01 00:00:00
abstract:PURPOSE:In this abstract, we discuss a biomechanical head and neck model that will be able to represent patient setup variations as well as physiologic changes and subsequently enable dose calculations on the deformed anatomy. METHODS:We selected Multi Pose MRI as the imaging modality to aid in model development and v...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4734893
更新日期:2012-06-01 00:00:00
abstract::Permanent implants of 125I seeds at Memorial Sloan-Kettering Cancer Center are performed by the method of "dimension averaging" to determine the total activity to be implanted; that is, the activity (in mCi) is taken to be five times the average dimension (in cm) of the target region. A nomograph has recently been dev...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.594269
更新日期:1976-01-01 00:00:00
abstract:PURPOSE:Stereotactic ablative body radiotherapy (SABR) for lung patients can be performed with volumetric-modulated arc therapy (VMAT) plans using off-axis target geometry to allow treatment in their CBCT verified position. For patient-specific quality assurance measurements using the PTW Octavius 4D phantom (PTW, Frei...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.12805
更新日期:2018-04-01 00:00:00
abstract::We have developed a new method for optimization in intensity modulated radiation therapy (IMRT) that makes use of simulated dynamics in a classical system of interacting particles. An analogy is drawn between intensity profile optimization in IMRT and relaxation to the equilibrium configuration in a dynamic system. Th...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1528179
更新日期:2003-01-01 00:00:00
abstract::Computed tomography is sensitive to changes in the imaged distribution during acquisition of the projection data. Previous investigations have emphasized discrete or discontinuous changes in the imaged object. Recent advances have motivated our investigation of object time-dependence characterized by a continuous func...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.594458
更新日期:1978-11-01 00:00:00
abstract::Clinical and biological evidence suggest that the success of GRID therapy in debulking large tumors depends on the high peak-to-valley contrast in the dose distribution. In this study, we show that the peaks and valleys can be significantly blurred out by respiration-induced tumor motion, possibly affecting the clinic...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2977538
更新日期:2008-10-01 00:00:00
abstract::Computer-aided diagnostic (CAD) schemes have been developed to assist radiologists in the early detection of lung cancer in radiographs and computed tomography (CT) images. In order to improve sensitivity for nodule detection, many researchers have employed a filter as a preprocessing step for enhancement of nodules. ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1581411
更新日期:2003-08-01 00:00:00
abstract::The photon spectra in vacuum around four types of 192Ir HDR brachytherapy sources are calculated using the Monte Carlo code EGS4 and the most recent spectral information on 192Ir decay. The air-kerma strengths per unit activity are calculated based on the photon fluence around a bare 192Ir source and around each of fo...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.598763
更新日期:1999-11-01 00:00:00
abstract:PURPOSE:A major challenge of four dimensional computed tomography (4DCT) in treatment planning and delivery has been the lack of respiration amplitude and phase reproducibility during image acquisition. The implementation of a prospective gating algorithm would ensure that images would be acquired only during user-spec...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3556589
更新日期:2011-03-01 00:00:00
abstract:PURPOSE:To balance dose reduction and image registration accuracy in breast setup imaging. In particular, the authors demonstrate the relationship between scan angle and dose delivery for cone beam tomosynthesis (CBTS) when employed for setup verification of breast cancer patients with surgical clips. METHODS:The dose...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3464716
更新日期:2010-08-01 00:00:00
abstract::A technique was developed to reduce the size and magnitude of the hot and cold spots in the abutting regions of photon and electron fields. The photon and electron fields were set up such that the photon field extended approximately 2 cm into the electron field in the abutting region. The region of the photon beam tha...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.598753
更新日期:1999-11-01 00:00:00
abstract:PURPOSE:The objective of this study was to evaluate organ dose and the effective dose to patients undergoing tomosynthesis (TS) and C-arm cone-beam computed tomography (CBCT) examinations and to compare the doses to those in multidetector CT (MDCT) scans. METHODS:Patient doses were measured with small sized silicon-ph...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3465045
更新日期:2010-08-01 00:00:00
abstract:PURPOSE:To develop a new design of an x-ray beam shaper for helical computed tomography (CT) that increases the dose utilization. METHODS:For typical reconstruction algorithms in helical CT, different data are utilized with different weights during back-projection. In particular, data of the outer detector rows, i.e.,...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3577766
更新日期:2011-07-01 00:00:00
abstract:PURPOSE:To compare and evaluate intensity-based registration methods for computation of serial x-ray mammogram correspondence. METHODS:X-ray mammograms were simulated from MRIs of 20 women using finite element methods for modeling breast compressions and employing a MRI/x-ray appearance change model. The parameter con...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3457470
更新日期:2010-09-01 00:00:00
abstract:PURPOSE:To introduce a novel laser-based optical-CT scanner for the readout of three-dimensional (3D) radiation dosimeters. METHODS:The scanner employs a diode laser, a cylindrical lens, a motorized linear rail, a rotation stage, and a charge-coupled device camera. The scanner operates in a translate-rotate fashion an...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3538924
更新日期:2011-02-01 00:00:00
abstract::Many problems in physics involve imaging objects with high spatial frequency content in a limited amount of time. The limitation of available experimental data leads to the infamous problem of diffraction limited data which manifests itself by causing ringing in the image. This ringing is due to the interference pheno...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.596427
更新日期:1989-05-01 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:To analyze the noise performance of the edge illumination phase-based x-ray imaging technique when applying "single-shot" phase retrieval. The latter consists in applying a sample-specific low-pass filter to the raw data, leading to "hybrid" images in which phase and attenuation contrast are merged with each ot...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.14366
更新日期:2020-09-01 00:00:00
abstract::In this paper, two new boundary tracing algorithms for segmentation of breast masses are presented. These new algorithms are based on the dynamic programming-based boundary tracing (DPBT) algorithm proposed in Timp and Karssemeijer, [S. Timp and N. Karssemeijer, Med. Phys. 31, 958-971 (2004)] The DPBT algorithm contai...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2791034
更新日期:2007-11-01 00:00:00
abstract:PURPOSE:To develop a pencil beam dose calculation algorithm for scanned proton beams that improves modeling of scatter events. METHODS:Our pencil beam algorithm (PBA) was developed for calculating dose from monoenergetic, parallel proton beams in homogeneous media. Fermi-Eyges theory was implemented for pencil beam tr...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4735624
更新日期:2012-06-01 00:00:00