Abstract:
:Proton therapy with active scanning beam delivery has significant advantages compared to conventional radiotherapy. However, so far only static targets have been treated in this way, since moving targets potentially lead to interplay effects. For 4D treatment planning, information on the target motion is needed to calculate time-resolved dose distributions. In this study, respiratory liver motion has been extracted from 4D CT data using two deformable image registration algorithms. In moderately moving patient cases (mean motion range around 6 mm), the registration error was no more than 3 mm, while it reached 7 mm for larger motions (range around 13 mm). The obtained deformation fields have then been used to calculate different time-resolved 4D treatment plans. Averaged over both motion estimations, interplay effects can increase the D₅-D₉₅ value for the clinical target volume (CTV) from 8.8% in a static plan to 23.4% when motion is considered. It has also been found that the different deformable registration algorithms can provide different motion estimations despite performing similarly for the selected landmarks, which in turn can lead to differing 4D dose distributions. Especially for single-field treatments where no motion mitigation is used, a maximum (mean) dose difference (averaged over three cases) of 32.8% (2.9%) can be observed. However, this registration ambiguity-induced uncertainty can be reduced if rescanning is applied or if the treatment plan consists of multiple fields, where the maximum (mean) difference can decrease to 15.2% (0.57%). Our results indicate the necessity to interpret 4D dose distributions for scanned proton therapy with some caution or with error bars to reflect the uncertainties resulting from the motion estimation. On the other hand, rescanning has been found to be an appropriate motion mitigation technique and, furthermore, has been shown to be a robust approach to also deal with these motion estimation uncertainties.
journal_name
Phys Med Bioljournal_title
Physics in medicine and biologyauthors
Zhang Y,Boye D,Tanner C,Lomax AJ,Knopf Adoi
10.1088/0031-9155/57/7/1779subject
Has Abstractpub_date
2012-04-07 00:00:00pages
1779-95issue
7eissn
0031-9155issn
1361-6560journal_volume
57pub_type
杂志文章abstract::Densitometric quantification of coronary artery stenoses in angiographic images can be problematic for two reasons: (i) the x-rays are inadequately oriented with respect to the vessel segments of interest at image acquisition; (ii) non-linear effects due for instance to beam hardening, scattered radiation and veiling ...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/42/12/011
更新日期:1997-12-01 00:00:00
abstract::In conventional gating approaches for positron emission tomography (PET), a single number of gates is predetermined for the whole field of view (FOV) regardless of spatially variant motion blurring effects, which compromises image quality by under-gating regions of large motion and over-gating static regions. To achie...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/aac71b
更新日期:2018-08-10 00:00:00
abstract::The concepts of radiance and fluence are fundamental to the description of a radiation field. The International Commission on Radiological Units and Measurements (ICRU) has defined fluence in terms of the number of the radiation particles crossing a small sampling sphere. A second definition has been proposed in which...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/39/6/011
更新日期:1994-06-01 00:00:00
abstract::This paper presents a compressed sensing (CS)-inspired reconstruction method for limited-angle computed tomography (CT). Currently, CS-inspired CT reconstructions are often performed by minimizing the total variation (TV) of a CT image subject to data consistency. A key to obtaining high image quality is to optimize t...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/58/7/2119
更新日期:2013-04-07 00:00:00
abstract::Cavity theories are used to relate the dose in a medium to the dose in a cavity. No satisfactory analytical approach exists for the case of intermediate cavities, such as TLDs, when interface effects are important. Burlin proposed a general cavity theory that accounts for the cavity size but which ignores interface ef...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/46/4/320
更新日期:2001-04-01 00:00:00
abstract::Values of W (the mean energy required to create an ion pair when a charged particle is stopped in a gas) are needed in radiation dosimetry to convert ionisation chamber current readings to absorbed dose. For neutron dosimetry the most important W values are those for protons, and this paper describes absolute measurem...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/30/11/003
更新日期:1985-11-01 00:00:00
abstract::A circular scanning trajectory is and will likely remain a popular choice of trajectory in computed tomography (CT) imaging because it is easy to implement and control. Filtered-backprojection (FBP)-based algorithms have been developed previously for approximate and exact reconstruction of the entire image or a region...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/49/18/011
更新日期:2004-09-21 00:00:00
abstract::This work studies the effect of age on lung dose commitments arising from the inhalation of an atmosphere containing radionuclides of varying half-lives and physical sizes. This dependence is significant in many cases, approaching a ratio of 2 in several instances when the maximum dose at a given age is compared with ...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/27/4/005
更新日期:1982-04-01 00:00:00
abstract::Clinical diffusion MRI (dMRI) is sensitive to micrometer scale spin displacements, but the image resolution is ∼mm, so the biophysical interpretation of the signal relies on establishing appropriate subvoxel tissue models. A class of two-compartment exchange models originally proposed by Kärger have been used success...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/ab2aa6
更新日期:2019-08-01 00:00:00
abstract::Radiation dose calculation using models of the human anatomy has been a subject of great interest to radiation protection, medical imaging, and radiotherapy. However, early pioneers of this field did not foresee the exponential growth of research activity as observed today. This review article walks the reader through...
journal_title:Physics in medicine and biology
pub_type: 杂志文章,评审
doi:10.1088/0031-9155/59/18/R233
更新日期:2014-09-21 00:00:00
abstract::We have developed an impedance magnetocardiogram (IMCG) system to detect the change of magnetic field corresponding to changes in blood volume in the heart. A low magnetic field from the electrical activity of the human heart--the so-called magnetocardiogram (MCG)--can be simultaneously detected by using this system. ...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/46/2/403
更新日期:2001-02-01 00:00:00
abstract::The University of Washington (UW) Clinical Neutron Therapy System (CNTS) has been used to treat over 3300 patients. Treatment planning for these patients is currently performed using an MV x-ray model in Pinnacle® adapted to fit measurements of fast neutron output factors, wedge factors, depth-dose and lateral profile...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/ab9a85
更新日期:2020-08-31 00:00:00
abstract::The effect of the physical state (phase) of the absorbing medium and the energy straggling of the alpha particles on the calculation of the radiation dose due to the daughter products of radon deposited in the lung have been studied in detail. The stopping power data for alpha particles in water and water vapour have ...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/32/8/004
更新日期:1987-08-01 00:00:00
abstract::Intravascular coronary thermography is a method that may detect vulnerable, atherosclerotic plaques and is currently evaluated in a clinical setting. Active macrophages or enzymatic heat releasing processes in vulnerable plaques may act as heat sources. To better understand the parameters of influence on thermographic...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/49/19/001
更新日期:2004-10-07 00:00:00
abstract::Monte Carlo simulations are used to investigate skin dose resulting from chest wall radiotherapy with bolus. A simple model of a female thorax is developed, which includes a 2 mm-thick skin layer. Two representative 6 MV source models are considered: a tangents source model consisting of a parallel opposed pair of med...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/ab95dc
更新日期:2020-08-11 00:00:00
abstract::Dental tomographic cone-beam x-ray imaging devices record truncated projections and reconstruct a region of interest (ROI) inside the head. Image reconstruction from the resulting local tomography data is an ill-posed inverse problem. A new Bayesian multiresolution method is proposed for local tomography reconstructio...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/52/22/008
更新日期:2007-11-21 00:00:00
abstract::Compressed sensing (CS) aims to recover images from fewer measurements than that governed by the Nyquist sampling theorem. Most CS methods use analytical predefined sparsifying domains such as total variation, wavelets, curvelets, and finite transforms to perform this task. In this study, we evaluated the use of dicti...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/60/15/5853
更新日期:2015-08-07 00:00:00
abstract::A rotary positron-emission computed tomography system has been proposed in which detectors are mounted unequally spaced on a ring, so as to provide fine and uniform linear sampling during a 360 degree rotation of the ring around its centre. The usefulness of a simple iterative method for searching for a suitable arran...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/26/3/011
更新日期:1981-05-01 00:00:00
abstract::Radiation therapy is an image-guided process whose success critically depends on the imaging modality used for treatment planning and the level of integration of the available imaging information. In this work, we establish a dose optimization framework for incorporating metabolic information from functional imaging m...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/47/20/301
更新日期:2002-10-21 00:00:00
abstract::Enabling automated pipelines, image analysis and big data methodology in cancer clinics requires thorough understanding of the data. Automated quality assurance steps could improve the efficiency and robustness of these methods by verifying possible data biases. In particular, in head and neck (H&N) computed-tomograph...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/ab5427
更新日期:2020-01-10 00:00:00
abstract::Heavy-ion radiotherapy exploits the high biological effectiveness of localized energy deposition delivered by so-called Bragg-peak particles. Recent publications have challenged the established procedures to calculate biological effective dose distributions in treatment planning. They emphasize the importance of very ...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/54/7/N03
更新日期:2009-04-07 00:00:00
abstract::We present a comparison of simulated low-frequency electromagnetic fields in the human body, calculated by means of the electro-quasistatic formulation. The geometrical data in these simulations were provided by an anatomically realistic, high-resolution human body model, while the dielectric properties of the various...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/50/19/N02
更新日期:2005-10-07 00:00:00
abstract::Coronary computed tomography angiography (cCTA) is a commonly used imaging modality for the evaluation of coronary artery disease. cCTA is generally reconstructed in multiple cardiac phases because different coronary arteries may be better visualized in some phases than in others due to the periodic cardiac motion. We...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/59/16/4661
更新日期:2014-08-21 00:00:00
abstract::In medical imaging different techniques have been developed to gain information from inside a tissue. Optoacoustics is a method to generate tomography pictures of tissue using Q-switched laser pulses. Due to thermal and pressure confinement, a short light pulse generates a pressure distribution inside tissue, which mi...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/46/7/309
更新日期:2001-07-01 00:00:00
abstract::Our aim is to investigate the impact of respiratory motion on tumor quantification and delineation in static PET/CT imaging using a population of patient respiratory traces. A total of 1295 respiratory traces acquired during whole body PET/CT imaging were classified into three types according to the qualitative shape ...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/54/24/007
更新日期:2009-12-21 00:00:00
abstract::The aim of the study is to determine PTV margin for inter-observer variability in the volumetric modulated arc therapy (VMAT) prostate radiotherapy with high-dose volumetric CT (HDVCT) and conventional helical CT (CCT) for planning. Secondly to investigate the impact of geometric (PTV expansion) and dosimetric (confor...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/ab050f
更新日期:2019-03-14 00:00:00
abstract::We explore how the radioactive background from naturally occurring 176Lu affects single photon transmission imaging for lutetium orthosilicate (LSO) scintillator-based PET cameras by estimating the transmission noise equivalent count rate (NECR) including this background. Assuming a typical PET camera geometry (80 cm ...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/47/19/307
更新日期:2002-10-07 00:00:00
abstract::A near-field probe is described that enables high spatial resolution imaging with terahertz (THz) pulses. The spatial resolution capabilities of the system lie in the range of few microns and we demonstrate a resolution of 7 microm using broad-banded THz pulses with an intensity maximum near 0.5 THz. We present a stud...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/47/21/308
更新日期:2002-11-07 00:00:00
abstract::A method of measuring the image quality of medical imaging equipment is considered within the framework of statistical decision theory. In this approach, images are regarded as random vectors and image quality is defined in the context of the image information available for performing a specified detection or discrimi...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/38/1/006
更新日期:1993-01-01 00:00:00
abstract::This study investigates the dosimetric impact of using population-based Hounsfield units (HUs) and ICRU-based HUs as a function of the number of tissue segments for bulk density assignment toward MRI-based treatment planning in the abdomen. To avoid potential geometric differences between CT and MR images, CT images r...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/aacfb1
更新日期:2018-07-24 00:00:00