bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reduction of excitation light leakage to improve near‐infrared fluorescence imaging for tissue surface and deep tissue imaging
Authors: Zhu Banghe , Rasmussen John C. , Lu Yujie , Sevick‐Muraca Eva M. 
Published: November 2010

Purpose:Fluorescence‐enhanced optical imaging using near‐infrared (NIR) light developed forin vivo molecular targeting and reporting of various diseases provides promising opportunities for diagnostic imaging. However, the measurement sensitivity of NIR fluorescence (NIRF) optical imaging systems is limited by the leakage of the strong backscattered excitation light through rejection filters. In this article, the authors present a systematic method for improving sensitivity and validating the NIRF optical imager currently used for clinical imaging of human lymphatic function.Methods:The proposed systemic method consists of an appropriate filter combination and a collimation optics adapted to an NIRF optical imager. The spectral contributions were first assessed due to the excitation light backscattered from the tissue and from non‐normal‐incidence of the excitation light on the optical filters used in the authors' NIRF clinical imaging system. Then two tests were conducted to assess the system with and without the components of appropriate filters combination and collimation optics using: (1) a phantom to evaluate excitation light leakage as a function of target depth and (2) deployment in an actual human study.Results:The phantom studies demonstrate as much as two to three orders of magnitude reduction in the transmission ratio, indicating that the excitation light leakage can be reduced upon using the appropriate filter combination and collimation optics while anin vivo investigatory human study confirms improved imaging.Conclusions:The method for reducing the excitation light leakage is presented for validating collected signals for fluorescence imaging.
Photoacoustic angiography of the breast
Authors: Kruger Robert A. , Lam Richard B. , Reinecke Daniel R. , Del Rio Stephen P. , Doyle Ryan P. 
Published: November 2010

Purpose:The authors report a noninvasive technique and instrumentation for visualizing vasculature in the breast in three dimensions without using either ionizing radiation or exogenous contrast agents, such as iodine or gadolinium. Vasculature is visualized by virtue of its high hemoglobin content compared to surrounding breast parenchyma. The technique is compatible with dynamic contrast‐enhanced studies.Methods:Photoacoustic sonic waves were stimulated in the breast with a pulsed laser operating at 800 nm and a mean exposure of 20 mJ/pulse over an area of. These waves were subsequently detected by a hemispherical array of piezoelectric transducers, the temporal signals from which were filtered and backprojected to form three‐dimensional images with nearly uniform k‐space sampling.Results:Three‐dimensional vascular images of a human volunteer demonstrated a clear visualization of vascular anatomy with submillimeter spatial resolution to a maximum depth of 40 mm using a 24 s image acquisition protocol. Spatial resolution was nearly isotropic and approached over a field of view.Conclusions:The authors have successfully visualized submillimeter breast vasculature to a depth of 40 mm using an illumination intensity that is 32 times less than the maximum permissible exposure according to theAmerican National Standard for Safe Use of Lasers. Clearly, the authors can achieve greater penetration depth in the breast by increasing the intensity and the cross‐sectional area of the illumination beam. Given the 24 s image acquisition time without contrast agent, dynamic, contrast‐enhanced, photoacoustic breast imaging using optically absorbing contrast agents is conceivable in the future.
Performance of the NIRS fast scanning system for heavy‐ion radiotherapy
Authors: Furukawa Takuji , Inaniwa Taku , Sato Shinji , Shirai Toshiyuki , Takei Yuka , Takeshita Eri , Mizushima Kota , Iwata Yoshiyuki , Himukai Takeshi , Mori Shinichiro , Fukuda Shigekazu , Minohara Shinichi , Takada Eiichi , Murakami Takeshi , Noda Koji 
Published: November 2010

Purpose:A project to construct a new treatment facility, as an extension of the existing HIMAC facility, has been initiated for the further development of carbon‐ion therapy at NIRS. This new treatment facility is equipped with a 3D irradiation system with pencil‐beam scanning. The challenge of this project is to realize treatment of a moving target by scanning irradiation. To achieve fast rescanning within an acceptable irradiation time, the authors developed a fast scanning system.Methods:In order to verify the validity of the design and to demonstrate the performance of the fast scanning prior to use in the new treatment facility, a new scanning‐irradiation system was developed and installed into the existing HIMAC physics‐experiment course. The authors made strong efforts to develop (1) the fast scanning magnet and its power supply, (2) the high‐speed control system, and (3) the beam monitoring. The performance of the system including 3D dose conformation was tested by using the carbon beam from the HIMAC accelerator.Results:The performance of the fast scanning system was verified by beam tests. Precision of the scanned beam position was less than ±0.5 mm. By cooperating with the planning software, the authors verified the homogeneity of the delivered field within ±3% for the 3D delivery. This system took only 20 s to deliver the physical dose of 1 Gy to a spherical target having a diameter of 60 mm with eight rescans. In this test, the average of the spot‐staying time was considerably reduced to, while the minimum staying time was .Conclusions:As a result of this study, the authors verified that the new scanning delivery system can produce an accurate 3D dose distribution for the target volume in combination with the planning software.
Flow measurement in MRI using arterial spin labeling with cumulative readout pulses—Theory and validation
Authors: Wang Yi , Kim Seong‐Eun , DiBella Edward V. R. , Parker Dennis L. 
Published: November 2010

Purpose:This article systematically examines arterial spin labeling (ASL) as a flow quantification technique through theoretical simulation,in vitro, and in vivo experiment. The authors present a novel imaging pulse sequence design consisting of a single ASL magnetization preparation followed by Look‐Locker‐like image readouts. Bloch‐equation‐based modeling has been developed and validated using a hemodialyzer as a tissue‐mimicking flow phantom.Methods:After the single in‐plane slice‐selective double inversion magnetization preparation, multiple TFL readouts are acquired with linear k‐space ordering, causing a signal variation that depends on through‐slice flow velocity. Computer simulations were performed to assess the behavior of the flow‐dependent ASL signal as a function of varying imaging parameters. The signal was optimized by choosing imaging parameters that maximize the simulated flow‐sensitive signal. Furthermore, a hemodialyzer which mimics blood flow in human tissues was tested with a wide range of flow rates. An exponential curve fitting of the flow‐sensitive dynamics to the model derived from Bloch equations provides a method to estimate through‐slice velocity for varying flow rates on the hemodialyzer andin vivo human brain.Results:The flow dependency of the ASL signal and the sensitivity of the ASL signal to imaging parameters were demonstrated. Experimental results from a hemodialyzer when fitted with a Bloch‐equation‐based model provide flow measurements that are consistent with ground truth velocities. Human brain velocity mapping was obtained as well.Conclusions:The results provide evidence that the proposed pulse sequence design is an effective technique to measure total fluid flow through image voxels. The unique combination of the two main features, multiple‐image readout after a single ASL preparation and linear acquisition ordering in the phase encoding direction in TFL imaging, make this technique an appealing flow imaging method to quantify through‐plane flow in a time‐efficient manner.
Exploring the potential of context‐sensitive CADe in screening mammography
Authors: Tourassi Georgia D. , Mazurowski Maciej A. , Harrawood Brian P. , Krupinski Elizabeth A. 
Published: November 2010

Purpose:Conventional computer‐assisted detection (CADe) systems in screening mammography provide the same decision support to all users. The aim of this study was to investigate the potential of a context‐sensitive CADe system which provides decision support guided by each user's focus of attention during visual search and reporting patterns for a specific case.Methods:An observer study for the detection of malignant masses in screening mammograms was conducted in which six radiologists evaluated 20 mammograms while wearing an eye‐tracking device. Eye‐position data and diagnostic decisions were collected for each radiologist and case they reviewed. These cases were subsequently analyzed with an in‐house knowledge‐based CADe system using two different modes: Conventional mode with a globally fixed decision threshold and context‐sensitive mode with a location‐variable decision threshold based on the radiologists' eye dwelling data and reporting information.Results:The CADe system operating in conventional mode had 85.7% per‐image malignant mass sensitivity at 3.15 false positives per image (FPsI). The same system operating in context‐sensitive mode provided personalized decision support at 85.7%–100% sensitivity and 0.35–0.40 FPsI to all six radiologists. Furthermore, context‐sensitive CADe system could improve the radiologists' sensitivity and reduce their performance gap more effectively than conventional CADe.Conclusions:Context‐sensitive CADe support shows promise in delineating and reducing the radiologists' perceptual and cognitive errors in the diagnostic interpretation of screening mammograms more effectively than conventional CADe.
Geometrical and Monte Carlo projectors in 3D PET reconstruction
Authors: Aguiar Pablo , Rafecas Magdalena , Ortuño Juan Enrique , Kontaxakis George , Santos Andrés , Pavía Javier , Ros Domènec 
Published: November 2010

Purpose: In the present work, the authors compare geometrical and Monte Carlo projectors in detail. The geometrical projectors considered were the conventional geometrical Siddon ray‐tracer (S‐RT) and the orthogonal distance‐based ray‐tracer (OD‐RT), based on computing the orthogonal distance from the center of image voxel to the line‐of‐response. A comparison of these geometrical projectors was performed using different point spread function (PSF) models. The Monte Carlo‐based method under consideration involves an extensive model of the system response matrix based on Monte Carlo simulations and is computed off‐line and stored on disk.Methods: Comparisons were performed using simulated and experimental data of the commercial small animal PET scanner rPET.Results: The results demonstrate that the orthogonal distance‐based ray‐tracer and Siddon ray‐tracer using PSF image‐space convolutions yield better images in terms of contrast and spatial resolution than those obtained after using the conventional method and the multiray‐based S‐RT. Furthermore, the Monte Carlo‐based method yields slight improvements in terms of contrast and spatial resolution with respect to these geometrical projectors.Conclusions: The orthogonal distance‐based ray‐tracer and Siddon ray‐tracer using PSF image‐space convolutions represent satisfactory alternatives to factorizing the system matrix or to the conventional on‐the‐fly ray‐tracing methods for list‐mode reconstruction, where an extensive modeling based on Monte Carlo simulations is unfeasible.
Thoracic target volume delineation using various maximum‐intensity projection computed tomography image sets for radiotherapy treatment planning
Authors: Zamora David A. , Riegel Adam C. , Sun Xiaojun , Balter Peter , Starkschall George , Mawlawi Osama , Pan Tinsu 
Published: November 2010

Purpose:Four‐dimensional computed tomography (4D‐CT) is commonly used to account for respiratory motion of target volumes in radiotherapy to the thorax. From the 4D‐CT acquisition, a maximum‐intensity projection (MIP) image set can be created and used to help define the tumor motion envelope or the internal gross tumor volume (iGTV). The purpose of this study was to quantify the differences in automatically contoured target volumes for usage in the delivery of stereotactic body radiation therapy using MIP data sets generated from one of the four methods: (1) 4D‐CT phase‐binned (PB) based on retrospective phase calculations, (2) 4D‐CT phase‐corrected phase‐binned (PC‐PB) based on motion extrema, (3) 4D‐CT amplitude‐binned (AB), and (4) cine CT built from all available images.Methods:MIP image data sets using each of the four methods were generated for a cohort of 28 patients who had prior thoracic 4D‐CT scans that exhibited lung tumor motion of at least 1 cm. Each MIP image set was automatically contoured on commercial radiation treatment planning system. Margins were added to the iGTV to observe differences in the final simulated planning target volumes (PTVs).Results:For all patients, the iGTV measured on the MIP generated from the entire cine CT data set was the largest. Expressed as a percentage of , 4D‐CT iGTV (all sorting methods) ranged from 83.8% to 99.1%, representing differences in the absolute volume ranging from 0.02 to ; the largest average and range of 4D‐CT iGTV measurements was from the PC‐PB data set. Expressed as a percentage of (expansions applied to ), the 4D‐CT PTV ranged from 87.6% to 99.6%, representing differences in the absolute volume ranging from 0.08 to . Regions of the measured respiratory waveform corresponding to a rapid change of phase or amplitude showed an increased susceptibility to the selection of identical images for adjacent bins. Duplicate image selection was most common in the AB implementation, followed by the PC‐PB method. The authors also found that the image associated with the minimum amplitude measurement did not always correlate with the image that showed maximum tumor motion extent.Conclusions:The authors identified cases in which the MIP generated from a 4D‐CT sorting process under‐represented the iGTV by more than 10% or up to when compared to the . They suggest utilization of a MIP generated from the full cine CT data set to ensure maximum inclusive tumor extent.
Strategies for scatter correction in dual source CT
Authors: Petersilka M. , Stierstorfer K. , Bruder H. , Flohr T. 
Published: November 2010

Purpose:Dual source CT (DSCT) systems utilize two measurement systems (A) and (B) offset by about 90°. A special challenge in DSCT is cross‐scattered radiation, i.e., scattered radiation from x‐ray tube (B) detected in detector (A) and vice versa. Cross‐scattered radiation can produce artifacts and degrade the contrast‐to‐noise ratio (CNR) of the images. Correction algorithms are mandatory to mitigate the negative effects of cross‐scattered radiation. The purpose of this work is to describe and evaluate different methods for cross‐scatter correction in DSCT.Methods:The authors present two techniques for cross‐scatter correction in DSCT. The first technique (1) is model‐based. Assuming that cross‐scatter is predominantly surface scatter, adequate knowledge about the surface of the scattering object is sufficient to describe the magnitude and distribution of cross‐scatter. The relevant surface information is derived from an analysis of the raw‐data sinogram during the CT‐scan. The correction is performed by a table look‐up into previously measured and stored cross‐scatter distributions for a variety of objects with different surface characteristics. The second technique (2) is measurement‐based. Dedicated sensors outside the penumbra of the fan beam in the z direction on both detectors (A) and (B) are used for an online measurement of both cross‐scattered and forward scattered radiation during the CT‐scan. In addition to the two scatter‐correction techniques, the authors describe a low‐pass filter method for the scatter‐correction term with the goal to improve the CNR of the corrected images. This filter can be applied to both model‐based (1) and measurement‐based (2) scatter correction. Both scatter‐correction techniques (1) and (2) are quantitatively assessed and the performance of the low‐pass filter method is evaluated using DSCT data of phantoms (water cylinders and anthropomorphic phantoms) and DSCT patient scan data.Results:Both scatter‐correction techniques restore image contrasts and reduce cross‐scatter induced artifacts in DSCT images. The measurement‐based technique results in higher CNR than the model‐based technique if the proposed low‐pass filtering of the scatter‐correction term is applied. Low‐pass filtering improves the CNR of cross‐scatter‐correction approaches beyond the limits published in the literature [Engel et al., “X‐ray scattering in single‐ and dual‐source CT,” Med. Phys. 35(1), 318–332 (2008)].Conclusions:Both model‐based and measurement‐based scatter correction can mitigate the negative effects of cross‐scatter in DSCT. The application of low‐pass filtering to the scatter‐correction term improves the CNR whenever the ratio of scattered radiation to total signal is high, as in larger patients.
Investigation of an implantable dosimeter for single‐point water equivalent path length verification in proton therapy
Authors: Lu Hsiao‐Ming , Mann Greg , Cascio Ethan 
Published: November 2010

Purpose:In vivo range verification in proton therapy is highly desirable. A recent study suggested that it was feasible to use point dose measurement for in vivo beam range verification in proton therapy, provided that the spread‐out Bragg peak dose distribution is delivered in a different and rather unconventional manner. In this work, the authors investigate the possibility of using a commercial implantable dosimeter with wireless reading for this particular application.Methods:The traditional proton treatment technique delivers all the Bragg peaks required for a SOBP field in a single sequence, producing a constant dose plateau across the target volume. As a result, a point dose measurement anywhere in the target volume will produce the same value, thus providing no information regarding the water equivalent path length to the point of measurement. However, the same constant dose distribution can be achieved by splitting the field into a complementary pair of subfields, producing two oppositely “sloped” depth‐dose distributions, respectively. The ratio between the two distributions can be a sensitive function of depth and measuring this ratio at a point inside the target volume can provide the water equivalent path length to the dosimeter location. Two types of field splits were used in the experiment, one achieved by the technique of beam current modulation and the other by manipulating the location and width of the beam pulse relative to the range modulator track. Eight MOSFET‐based implantable dosimeters at four different depths in a water tank were used to measure the dose ratios for these field pairs. A method was developed to correct the effect of the well‐known LET dependence of the MOSFET detectors on the depth‐dose distributions using the columnar recombination model. The LET‐corrected dose ratios were used to derive the water equivalent path lengths to the dosimeter locations to be compared to physical measurements.Results:The implantable dosimeters measured the dose ratios with a reasonable relative uncertainty of 1%–3% at all depths, except when the ratio itself becomes very small. In total, 55% of the individual measurements reproduced the water equivalent path lengths to the dosimeters within 1 mm. For three dosimeters, the difference was consistently less than 1 mm. Half of the standard deviations over the repeated measurements were equal or less than 1 mm.Conclusions:With a single fitting parameter, the LET‐correction method worked remarkably well for the MOSFET detectors. The overall results were very encouraging for a potential method ofin vivo beam range verification with millimeter accuracy. This is sufficient accuracy to expand range of clinical applications in which the authors could use the distal fall off of the proton depth dose for tight margins.
Sinogram preprocessing and binary reconstruction for determination of the shape and location of metal objects in computed tomography (CT)
Authors: Meng Bowen , Wang Jing , Xing Lei 
Published: November 2010

Purpose:To develop a binary image reconstruction method for the autolocalization of metallic object(s) in CT with sparse projections.Methods:The authors divide the system into two types of contents: Metal(s) and nonmetal(s). The boundaries of metallic objects are obtained by using a penalized weighted least‐squares algorithm with the adequate intensity gradient‐controlled. A novel mechanism of “amplifying” the difference between metal(s) and nonmetallic substances is introduced by preprocessing the sinogram data, which is shown to be necessary in dealing with a case with sparse projection data. A series of experimental studies are performed to evaluate the proposed approach.Results:A novel binary CT image reconstruction formalism is established for the autodetermination of the shape and location of metallic objects in the presence of limited number of projections. Experimental studies reveal that the presented algorithm works well even when the embedded metal object(s) has different shape(s). It is also shown that when the projection data are sparse, a differential manipulation of projection data can greatly facilitate the binary reconstruction process and allow the authors to obtain accurate binary CT images that would otherwise be unattainable.Conclusions:Binary CT reconstruction provides a viable method for determining the geometric distribution information of the implanted metal objects in CT imaging.
Sensitive
In Vitro
System To Assess Morphological and Biochemical Effects of Praziquantel and Albendazole on
Taenia solium
Cysts
Authors: Mahanty S. , Paredes A. , Marzal M. , Gonzalez E. , Rodriguez S. , Dorny P. , Guerra-Giraldez C. , Garcia H. H. , Nash T. 
Published: November 2010

ABSTRACT

Neurocysticercosis resulting from
Taenia solium
infections is a major cause of adult-acquired seizures worldwide. Disease is caused by larval cysts, and treatment consists of the anthelmintic drugs albendazole or praziquantel. There are no standard methods to assess drug activity to
T. solium
cysts
in vitro
. Morphological, functional, and biochemical changes that might reflect damaging (inhibiting, cytotoxic) drug effects were analyzed after exposure of cysts to albendazole sulfoxide (ABZ-SO), the major active metabolite of the drug
in vivo
, praziquantel (PZQ), or combinations of both. PZQ exposure led to a decrease in cyst size and inhibition of evagination, whereas ABZ-SO exposure resulted in minimal changes. Alkaline phosphatase (AP) is normally secreted by cysts, and both drugs inhibited AP secretion at concentrations of 5 and 50 ng/ml for PZQ and ABZ-SO, respectively. Some combinations of both drugs resulted in additive and/or synergistic activities. Parasite-specific antigen, detected in the cerebrospinal fluid and blood of infected patients, is also normally secreted by
T. solium
cysts. Antigen secretion was similarly inhibited by ABZ-SO and PZQ and a combination of both drugs, suggesting that inhibition of secretion is a common downstream consequence of the activities of both drugs. These studies establish quantitative methods to measure
in vitro
anthelmintic activity and suggest combination therapy with ABZ-SO and PZQ may have clinical benefit.