Abstract:
:The signal-to-noise ratio (SNR) in x-ray imaging can be increased using a photon counting detector which could allow for rejecting electronics noise and for weighting x-ray photons according to their energies. This approach, however, was not feasible for a long time because photon counting x-ray detectors with very high count rates, good energy resolution and a large number of small pixels were required. These problems have been addressed with the advent of new detector materials, fast readout electronics and powerful computers. In this work, we report on the experimental evaluation of projection x-ray imaging with a photon counting cadmium-zinc-telluride (CZT) detector with energy resolving capabilities. The detector included two rows of pixels with 128 pixels per row with 0.9 x 0.9 mm(2) pixel size, and a 2 Mcount pixel(-1) s(-1) count rate. The x-ray tube operated at 120 kVp tube voltage with 2 mm Al-equivalent inherent filtration. The x-ray spectrum was split into five regions, and five independent x-ray images were acquired at a time. These five quasi-monochromatic x-ray images were used for x-ray energy weighting and material decomposition. A tissue-equivalent phantom was used including contrast elements simulating adipose, calcifications, iodine and air. X-ray energy weighting improved the SNR of calcifications and iodine by a factor of 1.32 and 1.36, respectively, as compared to charge integrating. Material decomposition was performed by dual energy subtraction. The low- and high-energy images were generated in the energy ranges of 25-60 keV and 60-120 keV, respectively, by combining five monochromatic image data into two. X-ray energy weighting was applied to low- and high-energy images prior to subtraction, and this improved the SNR of calcifications and iodine in dual energy subtracted images by a factor of 1.34 and 1.25, respectively, as compared to charge integrating. The detector energy resolution, spatial resolution, linearity, count rate, noise and image uniformity were investigated. The limitations of this technology were emphasized and possible solutions were discussed.
journal_name
Phys Med Bioljournal_title
Physics in medicine and biologyauthors
Shikhaliev PMdoi
10.1088/0031-9155/54/16/009subject
Has Abstractpub_date
2009-08-21 00:00:00pages
4971-92issue
16eissn
0031-9155issn
1361-6560pii
S0031-9155(09)10960-0journal_volume
54pub_type
杂志文章abstract::This work aims to contribute to the study of the radiation dose distribution delivered to the hands of medical staff members during a general computed tomographic (CT) fluoroscopic guided procedure. In this study, both Monte Carlo simulations and measurements were performed. For free-in-air and computed tomography dos...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/58/16/5433
更新日期:2013-08-21 00:00:00
abstract::The electrostimulation excitation threshold of a nerve depends on temporal and frequency parameters of the stimulus. These dependences were investigated in terms of: (1) strength-duration (SD) curve for a single monophasic rectangular pulse, and (2) frequency dependence of the excitation threshold for a continuous sin...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/61/12/4364
更新日期:2016-06-21 00:00:00
abstract::A solid dynamic phantom with tissue-like optical properties is presented, which contains seven discrete targets impregnated with thermochromic pigment located at different depths from the surface. Changes in absorption are obtained in response to localized heating of the targets, simulating haemodynamic changes occurr...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/54/20/016
更新日期:2009-10-21 00:00:00
abstract::The stochastic nature of cavitation implies visualization of the cavitation cloud in real-time and in a discriminative manner for the safe use of focused ultrasound therapy. This visualization is sometimes possible with standard echography, but it strongly depends on the quality of the scanner, and is hindered by diff...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/aa4fe8
更新日期:2017-02-07 00:00:00
abstract::Estimation of a set of parameters that describe the geometry of the cone-beam computed tomography system plays an important role in the geometrical calibration. In the calibration process, the helical phantom consisting of spherical markers arranged on a helical trajectory has been widely applied. To directly determin...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/59/19/5667
更新日期:2014-10-07 00:00:00
abstract::Dosimetry of proton beams is generally evaluated in liquid water, or alternatively in solid phantoms via water equivalent ratios (WER). WER is defined as the ratio of proton range in liquid water to that in a phantom of certain material. Presently, WER is not available in the literature neither for a wide range of ene...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/aad0bd
更新日期:2018-07-27 00:00:00
abstract::The aim of the present work was to investigate how the native signal observed in the electron paramagnetic resonance (EPR) spectrum of tooth enamel and dentin is associated with the organic content of the two tissues. This was achieved by comparing the EPR native signal and the optical bands (Raman and infrared, IR) a...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/50/6/004
更新日期:2005-03-21 00:00:00
abstract::A full-field speckle interferometry method for non-contact and prospectively high speed Photoacoustic Tomography is introduced and evaluated as proof of concept. Thermoelastic pressure induced changes of the objects topography are acquired in a repetitive mode without any physical contact to the object. In order to ob...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/60/10/4045
更新日期:2015-05-21 00:00:00
abstract::In order (i) to evaluate the dose uncertainty of the mouthpiece in daily use during intensity-modulated radiotherapy of patients with head and neck cancer, and (ii) to present a system for in vivo dosimetry of the oral mucosa, we equipped the mouthpiece with alanine dosimeter probes for in vivo dosimetry. The aim was ...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/56/5/010
更新日期:2011-03-07 00:00:00
abstract::The accuracy of delivered radiation dose and the reproducibility of employed radiotherapy methods are key factors for preclinical radiobiology applications and research studies. In this work, ionization chamber (IC) measurements and Monte Carlo (MC) simulations were used to accurately determine the dose rate for total...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/aba40f
更新日期:2020-09-08 00:00:00
abstract::In proton scanning systems that employ active energy variation for depth modulation, a switch of the particle energy might typically require 1-2 s. For plans comprising many energy slices, these seconds could sum up to a non-negligible fraction of the total treatment duration. We have applied the Nyquist-Shannon sampl...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/53/9/N01
更新日期:2008-05-07 00:00:00
abstract::Quantification of nuclear medicine image data is a prerequisite for personalized absorbed dose calculations and quantitative biodistribution studies. The spatial response of a detector is a governing factor affecting the accuracy of image quantification, and the aim of this work was to model this impact. To simulate s...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/55/6/013
更新日期:2010-03-21 00:00:00
abstract::We show how the spectral imaging framework should be modified to account for a high fraction of Compton interactions in low Z detector materials such as silicon. Using this framework, where deposited energies differ from actual photon energies, we compare the performance of a silicon strip detector, including the infl...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/55/7/014
更新日期:2010-04-07 00:00:00
abstract::Ultrasound Doppler (UD) velocity measurements are commonly used to quantify blood flow velocities in vivo. The aim of our work was to investigate the accuracy of in vivo spectral Doppler measurements of velocity waveforms. Waveforms were derived from spectral Doppler signals and corrected for intrinsic spectral broade...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/56/6/015
更新日期:2011-03-21 00:00:00
abstract::The geometry of a permanent prostate implant varies over time. Seeds can migrate and edema of the prostate affects the position of seeds. Seed movements directly influence dosimetry which relates to treatment quality. We present a method that tracks all individual seeds over time allowing quantification of seed moveme...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/60/20/N391
更新日期:2015-10-21 00:00:00
abstract::Stereotactic Gamma Knife radiosurgery utilizes ionizing beams from (60)Co sources and relies on a combination of collimator sizes, weighting, etc to generate a high-dose region that is conformal with a designated target volume. Dose computation is typically performed by computer, but in this paper, single collimator d...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/53/8/003
更新日期:2008-04-21 00:00:00
abstract::Sensing and enumeration of specific types of circulating cells in small animals is an important problem in many areas of biomedical research. Microscopy-based fluorescence in vivo flow cytometry methods have been developed previously, but these are typically limited to sampling of very small blood volumes, so that ver...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/57/14/4627
更新日期:2012-07-21 00:00:00
abstract::We describe an improved algorithm for localising equivalent sources of biomagnetic fields in the human brain. The algorithm is an improvement over the sphere model in that it considers two distinct surfaces: an ellipsoid, to model the region of the skull on which the sensors are placed, and a sphere as the medium in w...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/32/1/017
更新日期:1987-01-01 00:00:00
abstract::It is difficult to test near-infrared spectrophotometry instruments in vivo. Therefore we constructed a liquid phantom which mimics the neonatal head. It consists of a spherical 3.5 mm thick layer of silicone rubber simulating skin and bone and a 0.5 mm thick clear layer of polypropylene imitating cerebrospinal fluid....
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/44/7/313
更新日期:1999-07-01 00:00:00
abstract::A multimodal micro-computed tomography (CT) and multi-spectral structured light imaging (SLI) system is introduced and systematically analyzed to test its feasibility to aid in margin delineation during breast conserving surgery (BCS). Phantom analysis of the micro-CT yielded a signal-to-noise ratio of 34, a contrast ...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/aa94b6
更新日期:2017-11-10 00:00:00
abstract::We model the heterogeneous response to radiation of multicellular tumour spheroids assuming position- and volume-dependent radiosensitivity. We propose a method to calculate the overall radiosensitivity parameters to obtain the surviving fraction of tumours. A mathematical model of a spherical tumour with a hypoxic co...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/50/8/005
更新日期:2005-04-21 00:00:00
abstract::Several methods of flip angle mapping for magnetic resonance imaging have been proposed. We evaluated the accuracy of five methods of flip angle measurement in the presence of measurement noise. Our analysis was performed in a closed form by propagation of probability density functions (PDFs). The flip angle mapping m...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/55/20/008
更新日期:2010-10-21 00:00:00
abstract::As a prerequisite for clinical treatments it was necessary to characterize the Elekta 1.5 T MRI-linac 7 MV FFF radiation beam. Following acceptance testing, beam characterization data were acquired with Semiflex 3D (PTW 31021), microDiamond (PTW 60019), and Farmer-type (PTW 30013 and IBA FC65-G) detectors in an Elekta...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/aab566
更新日期:2018-04-19 00:00:00
abstract::Dose to water (Dw) determination in clinical high-energy photon beams with ionization chambers calibrated in terms of absorbed dose to water has been proposed as an alternative to ionization chamber dosimetry based on air kerma calibrations. Dw in the clinical beam is derived using a kappaQ factor that scales the abso...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/44/3/002
更新日期:1999-03-01 00:00:00
abstract::In recent years, there has been an increase in the popularity of light-emitting diode (LED)-based, battery-powered transilluminators (BPTs) for facilitating transdermal vascular access in adults and neonates. BPTs are believed to have lower potential for inducing skin burns than prior devices based on high-power broad...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/54/22/008
更新日期:2009-11-21 00:00:00
abstract::Most tissue characterization methods use RF data originating from backscattering processes in the insonified tissue. Characterization of the tissue of a thin layer (e.g., an artery wall) poses problems because of the small amount of data available. The tissue layer may be so thin that there are no RF data that are not...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/36/10/002
更新日期:1991-10-01 00:00:00
abstract::For angiography using synchrotron radiation we measured the absorbed dose distribution in inhomogeneous phantoms with thin LiF:Mg, Cu, P, LiF:Mg, Ti thermoluminescent dosimeters (TLDs) in tissue and lung substitutes, and with Mg2SiO4:Tb TLDs in bone substitute for 33.32 keV monoenergetic photons from synchrotron radia...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/46/3/308
更新日期:2001-03-01 00:00:00
abstract::A clinical trial named PROMETHEUS is currently ongoing for inoperable hepatocellular carcinoma (HCC) at the Heidelberg Ion Beam Therapy Center (HIT, Germany). In this framework, 4D PET-CT datasets are acquired shortly after the therapeutic treatment to compare the irradiation induced PET image with a Monte Carlo PET p...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/61/11/4141
更新日期:2016-06-07 00:00:00
abstract::Margins are employed in radiotherapy treatment planning to mitigate the dosimetric effects of geometric uncertainties for the clinical target volume (CTV). Unfortunately, whilst the use of margins can increase the probability that sufficient dose is delivered to the CTV, it can also result in delivering high dose of r...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/aae658
更新日期:2018-10-29 00:00:00
abstract::This study aims to build a feasible mathematical model to analyze the mass evolution of NSCLC during standard fractionated radiotherapy. Seventy-three cases of NSCLC who were received radiotherapy with prescription dose of 2 Gy × 30 fx were selected retrospectively and divided into adenocarcinoma (ADC) group and squ...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/ab47c0
更新日期:2019-11-26 00:00:00