bluuebunny/crossref_metadata_2025_split huggingface dataset:
Extension from inpatients to outpatients: validity and reliability of the Oxford Knee Score in measuring health outcomes in patients with knee osteoarthritis
Authors: XIE Feng , YE Hua , ZHANG Yu , LIU Xia , LEI Ting , LI Shu‐Chuen 
Published: November 2010

AbstractObjective: To validate the Oxford Knee Score (OKS) in outpatients with knee osteoarthritis (OA).Methods: Eligible patients were interviewed using a pretested questionnaire containing the OKS, the Short Form (SF)‐6D, and the EuroQol Group 5‐Dimension Self‐Report Questionnaire score (EQ‐5D). Reliability was assessed using Cronbach’s alpha, dimensionality using principal component factor analysis and item‐total correlations, convergent and discriminant construct validity using expected correlations between the OKS and the SF‐6D and the EQ‐5D.Results: The OKS were well accepted by patients in a pilot testing. When administered to a convenient sample of 187 patients with knee OA (mean age 64 years, 74% female, mean duration of OA 7.6 years), Cronbach’s alpha exceeded 0.8 and factor analysis yielded two factors with eigenvalues > 1. Hypothesized item‐total correlations (ρ ≥ 0.4) were observed for all items. Convergent construct validity was supported by the presence of hypothesized moderate to strong correlations between the OKS and SF‐6D physical functioning, role limitation, social functioning and pain, EQ‐5D mobility, self‐care, usual activities, and pain/discomfort, and mobility visual analogue scale (ρ = 0.47–0.82). Discriminant construct validity was not satisfactory. The OKS correlated weakly with SF‐6D vitality (ρ = 0.35), but strongly with SF‐6D mental health and EQ‐5D anxiety/depression (ρ = 0.51 and 0.41, respectively).Conclusion: The OKS has demonstrated good psychometric properties and thus can be considered a reliable and valid measurement for outpatients with OA.
Alterations in cerebral blood flow and cerebrovascular reactivity during 14 days at 5050 m
Authors: Lucas Samuel J. E. , Burgess Keith R. , Thomas Kate N. , Donnelly Joseph , Peebles Karen C. , Lucas Rebekah A. I. , Fan Jui‐Lin , Cotter James D. , Basnyat Rishi , Ainslie Philip N. 
Published: November 2010

Non‐technical summaryBrain blood flow increases during the first week of living at high altitude. We do not understand completely what causes the increase or how the factors that regulate brain blood flow are affected by the high‐altitude environment. Our results show that the balance of oxygen (O2) and carbon dioxide (CO2) pressures in arterial blood explains 40% of the change in brain blood flow upon arrival at high altitude (5050 m). We also show that blood vessels in the brain respond to increases and decreases in CO2 differently at high altitude compared to sea level, and that this can affect breathing responses as well. These results help us to better understand the regulation of brain blood flow at high altitude and are also relevant to diseases that are accompanied by reductions in the pressure of oxygen in the blood.
Optimized pharmacokinetic modeling for the detection of perfusion differences in skeletal muscle with DCE‐MRI: Effect of contrast agent size
Authors: Jaspers Karolien , Leiner Tim , Dijkstra Petra , Oostendorp Marlies , van Golde Jolanda M. , Post Mark J. , Backes Walter H. 
Published: November 2010

Purpose:The goal of this study was to optimize dynamic contrast‐enhanced (DCE)‐MRI analysis for differently sized contrast agents and to evaluate the sensitivity for microvascular differences in skeletal muscle.Methods:In rabbits, pathophysiological perfusion differences between hind limbs were induced by unilateral femoral artery ligation. On days 14 and 21, DCE‐MRI was performed using a medium‐sized contrast agent (MCA) (Gadomer) or a small contrast agent (SCA) (Gd‐DTPA). Acquisition protocols were adapted to the pharmacokinetic properties of the contrast agent. Model‐based data analysis was optimized by selecting the optimal model, considering fit error, estimation uncertainty, and parameter interdependency from three two‐compartment pharmacokinetic models (normal and extended generalized kinetic models and Patlak model). Model‐based parameters were compared to the model‐free parameter area‐under‐curve (AUC). Finally, the sensitivity of transfer constant and AUC for physiological and pathophysiological microvascular differences was evaluated.Results:For the MCA, the optimal model included and plasma fraction . For the SCA, and interstitial fraction should be incorporated. For the MCA, were ( error) and for the red soleus and white tibialis muscle, respectively, . With the SCA, were (soleus) and (tibialis) . In the ischemic limb, was significantly decreased relative to the control limb (soleus: 15%–20%; tibialis: 5%–10%). Similar differences in AUC were found for both contrast agents.Conclusions:For optimal estimation of microvascular parameters, both model‐based and model‐free analysis should be adapted to the pharmacokinetic properties of the contrast agent. The detection of microvascular differences based on both and AUC was most sensitive when the analysis strategy was tailored to the contrast agent used. The MCA was equally sensitive for microvascular differences as the SCA, with the advantage of improved spatial resolution.
Physical effects of mechanical design parameters on photon sensitivity and spatial resolution performance of a breast‐dedicated PET system
Authors: Spanoudaki V. C. , Lau F. W. Y. , Vandenbroucke A. , Levin C. S. 
Published: November 2010

Purpose:This study aims to address design considerations of a high resolution, high sensitivity positron emission tomography scanner dedicated to breast imaging.Methods:The methodology uses a detailed Monte Carlo model of the system structures to obtain a quantitative evaluation of several performance parameters. Special focus was given to the effect of dense mechanical structures designed to provide mechanical robustness and thermal regulation to the minuscule and temperature sensitive detectors.Results:For the energies of interest around the photopeak (450–700 keV energy window), the simulation results predict a 6.5% reduction in the single photon detection efficiency and a 12.5% reduction in the coincidence photon detection efficiency in the case that the mechanical structures are interspersed between the detectors. However for lower energies, a substantial increase in the number of detected events (approximately 14% and 7% for singles at a 100–200 keV energy window and coincidences at a lower energy threshold of 100 keV, respectively) was observed with the presence of these structures due to backscatter. The number of photon events that involve multiple interactions in various crystal elements is also affected by the presence of the structures. For photon events involving multiple interactions among various crystal elements, the coincidence photon sensitivity is reduced by as much as 20% for a point source at the center of the field of view. There is no observable effect on the intrinsic and the reconstructed spatial resolution and spatial resolution uniformity.Conclusions:Mechanical structures can have a considerable effect on system sensitivity, especially for systems processing multi‐interaction photon events. This effect, however, does not impact the spatial resolution. Various mechanical structure designs are currently under evaluation in order to achieve optimum trade‐off between temperature stability, accurate detector positioning, and minimum influence on system performance.
Feature selection using factor analysis for Alzheimer's diagnosis using PET images
Authors: Salas‐Gonzalez D. , Górriz J. M. , Ramírez J. , Illán I. A. , López M. , Segovia F. , Chaves R. , Padilla P. , Puntonet C. G. ,   The Alzheimer's Disease Neuroimage Initiative
Published: November 2010

Purpose:This article presents a computer‐aided diagnosis technique for improving the accuracy of the early diagnosis of Alzheimer's disease (AD). Two hundred and ten PET images from the ADNI initiative [52 normal controls (NC), 114 mild cognitive impairment (MCI), and 53 AD subjects] are studied.Methods:The proposed methodology is based on the selection of voxels of interest using the t‐test and a posterior reduction of the feature dimension using factor analysis. Factor loadings are used as features for three different classifiers: Two multivariate Gaussian mixture model, with linear and quadratic discriminant function, and a support vector machine with linear kernel.Results:An accuracy rate up to 95% when NC and AD are considered and an accuracy rate up to 88% and 86% for NC‐MCI and NC‐MCI, AD, respectively, are obtained using SVM with linear kernel.Conclusions:Results are compared to the voxel‐as‐features and a PCA‐ based approach and the proposed methodology achieves better classification performance.
High frame rate ultrasound monitoring of high intensity focused ultrasound‐induced temperature changes: A novel asynchronous approach
Authors: Liu Hao‐Li , Huang Sheng‐Min , Li Meng‐Lin 
Published: November 2010

Purpose: When applying diagnostic ultrasound to guide focused ultrasound (FUS) thermal therapy, high frame rate ultrasonic temperature monitoring is valuable in better treatment control and dose monitoring. However, one of the potential problems encountered when performing ultrasonic temperature monitoring of a FUS procedure is interference between the FUS and imaging systems. Potential means of overcoming this problem include the switch between the FUS system and the imaging system (limited by a reduced frame rate of thermal imaging) or the development of complex synchronization protocols between the FUS therapeutic system and the ultrasonic imaging apparatus (limited by implementation efforts both for software and hardware designs, and low potential for widespread diffusion). In this paper, we apply an asynchronous idea to retrieving high frame rate and FUS‐interference‐free thermal imaging during FUS thermal therapy.Methods: Tone‐burst delivery mode of the FUS energy is employed in our method, and the imaging and FUS systems are purposely operated in an asynchronous manner. Such asynchronous operation causes FUS interference to saturate sequential image frames at different A‐lines; thus clean A‐lines from several image frames can be extracted by a total energy‐thresholding technique and then combined to reconstruct interference‐free B‐mode images at a high frame rate for temperature estimation. The performance of the proposed method is demonstrated by phantom experiments. Relationships of the FUS duty‐cycle with the maximum reconstructed frame rate of thermal imaging and the corresponding maximum temperature increase are also studied. Its performance was also evaluated and compared with the existing manually synchronous and synchronous approaches.Results: By proper selection of the FUS duty‐cycle, using our method, the frame rate of thermal imaging can be increased up to tenfold compared with that provided by the manually synchronous approach. Our method is capable of pushing the frame rate of thermal images to the same order as that of the synchronous approach while avoiding sacrificing the observable field of view (FOV) of temperature mapping.Conclusions: The asynchronous method can be easily implemented and allows thermal imaging at an improved frame rate, without the need for complex synchronization protocols between the FUS therapeutic system and the ultrasonic imaging apparatus and without sacrifice of observable FOV. This technology may provide an effective alternative for real‐time temperature measuring during thermal ablation procedures and can be easily integrated into current high intensity focused ultrasound systems.
Intensity inhomogeneity correction for the breast sonogram: Constrained fuzzy cell‐based bipartitioning and polynomial surface modeling
Authors: Lee Chia‐Yen , Chou Yi‐Hong , Huang Chiun‐Sheng , Chang Yeun‐Chung , Tiu Chui‐Mei , Chen Chung‐Ming 
Published: November 2010

Purpose:To develop an intensity inhomogeneity algorithm for breast sonograms in order to assist visual identification and automatic delineation of lesion boundaries.Methods:The proposed algorithm was composed of two essential ideas. One was decomposing the region of interest (ROI) into foreground and background regions by a cell‐based segmentation algorithm, called constrained fuzzy cell‐based bipartition‐EM (CFCB‐EM) algorithm. The CFCB‐EM algorithm deformed the contour in a fuzzy cell‐based deformation fashion with the cell structures derived by the fuzzy cell competition (FCC) algorithm as the deformation unit and the boundary estimated by the normalized cut (NC) algorithm as the reference contour. The other was modeling the intensity inhomogeneity in an ROI as a spatially variant normal distribution with a constant variance and spatially variant means, which formed a polynomial surface of order. The proposed algorithm was formulated as a nested EM algorithm comprising the outer‐layer EM algorithm, i.e., the intensity inhomogeneity correction‐EM (IIC‐EM) algorithm, and the inner‐layer EM algorithm, i.e., the CFCB‐EM algorithm. The E step of the IIC‐EM algorithm was to provide a reasonably good bipartition separating the ROI into foreground and background regions, which included three major component algorithms, namely, the FCC, the NC, and the CFCB‐EM. The M step of the IIC‐EM algorithm was to estimate and correct the intensity inhomogeneity field by least‐squared fitting the intensity inhomogeneity to an order polynomial surface. Forty‐nine breast sonograms with intensity inhomogeneity, each from a different subject, were randomly selected for performance analysis. Three assessments were carried out to evaluate the effectiveness of the proposed algorithm.Results:Based on the visual evaluation of two experienced radiologists, in the first assessment, 46 out of 49 breast lesions were considered to have better contrasts on the inhomogeneity‐corrected images by both radiologists. The interrater reliability for the radiologists was found to be . In the second assessment, the mean gradients of the low‐gradient boundary points before and after correction of the intensity inhomogeneity were compared by the paired t‐test, yielding a ‐value of 0.000, which suggested the proposed intensity inhomogeneity algorithm may enhance the mean gradient of the low‐gradient boundary points. By using the paired t‐test, the third assessment further showed that the Chan and Vese level set method could derive a much better lesion boundary on the inhomogeneity‐corrected image than on the original image .Conclusions:The proposed intensity inhomogeneity correction algorithm could not only augment the visibility of lesion boundary but also improve the segmentation result on a breast sonogram.
Optimization of a dual‐energy contrast‐enhanced technique for a photon‐counting digital breast tomosynthesis system: I. A theoretical model
Authors: Carton Ann‐Katherine , Ullberg Christer , Lindman Karin , Acciavatti Raymond , Francke Tom , Maidment Andrew D. A. 
Published: November 2010

Purpose:Dual‐energy (DE) iodine contrast‐enhanced x‐ray imaging of the breast has been shown to identify cancers that would otherwise be mammographically occult. In this article, theoretical modeling was performed to obtain optimally enhanced iodine images for a photon‐counting digital breast tomosynthesis (DBT) system using a DE acquisition technique.Methods:In the system examined, the breast is scanned with a multislit prepatient collimator aligned with a multidetector camera. Each detector collects a projection image at a unique angle during the scan. Low‐energy (LE) and high‐energy (HE) projection images are acquired simultaneously in a single scan by covering alternate collimator slits with Sn and Cu filters, respectively. Sn filters ranging from 0.08 to 0.22 mm thickness and Cu filters from 0.11 to 0.27 mm thickness were investigated. A tube voltage of 49 kV was selected. Tomographic images, hereafter referred to as DBT images, were reconstructed using a shift‐and‐add algorithm. Iodine‐enhanced DBT images were acquired by performing a weighted logarithmic subtraction of the HE and LE DBT images. The DE technique was evaluated for 20–80 mm thick breasts. Weighting factors,, that optimally cancel breast tissue were computed. Signal‐difference‐to‐noise ratios (SDNRs) between iodine‐enhanced and nonenhanced breast tissue normalized to the square root of the mean glandular dose (MGD) were computed as a function of the fraction of the MGD allocated to the HE images. Peak and optimal dose allocations were identified. and dose allocations were computed for several practical feasible system configurations (i.e., determined by the number of collimator slits covered by Sn and Cu). A practical system configuration and Sn–Cu filter pair that accounts for the trade‐off between SDNR, tube‐output, and MGD were selected.Results: depends on the Sn–Cu filter combination used, as well as on the breast thickness; to optimally cancel 0% with 50% glandular breast tissue, values were found to range from 0.46 to 0.72 for all breast thicknesses and Sn–Cu filter pairs studied. The optimal values needed to cancel all possible breast tissue glandularites vary by less than 1% for 20 mm thick breasts and 18% for 80 mm breasts. The system configuration where one collimator slit covered by Sn is alternated with two collimator slits covered by Cu delivers nearest to the peak value. A reasonable compromise is a 0.16 mm Sn–0.23 mm Cu filter pair, resulting in SDNR values between 1.64 and 0.61 and MGD between 0.70 and 0.53 mGy for 20–80 mm thick breasts at the maximum tube current.Conclusions:A DE acquisition technique for a photon‐counting DBT imaging system has been developed and optimized.
Level‐set segmentation of pulmonary nodules in megavolt electronic portal images using a CT prior
Authors: Schildkraut J. S. , Prosser N. , Savakis A. , Gomez J. , Nazareth D. , Singh A. K. , Malhotra H. K. 
Published: November 2010

Purpose:Pulmonary nodules present unique problems during radiation treatment due to nodule position uncertainty that is caused by respiration. The radiation field has to be enlarged to account for nodule motion during treatment. The purpose of this work is to provide a method of locating a pulmonary nodule in a megavolt portal image that can be used to reduce the internal target volume (ITV) during radiation therapy. A reduction in the ITV would result in a decrease in radiation toxicity to healthy tissue.Methods:Eight patients with nonsmall cell lung cancer were used in this study. CT scans that include the pulmonary nodule were captured with a GE Healthcare LightSpeed RT 16 scanner. Megavolt portal images were acquired with a Varian Trilogy unit equipped with an AS1000 electronic portal imaging device. The nodule localization method uses grayscale morphological filtering and level‐set segmentation with a prior. The treatment‐time portion of the algorithm is implemented on a graphical processing unit.Results:The method was retrospectively tested on eight cases that include a total of 151 megavolt portal image frames. The method reduced the nodule position uncertainty by an average of 40% for seven out of the eight cases. The treatment phase portion of the method has a subsecond execution time that makes it suitable for near‐real‐time nodule localization.Conclusions:A method was developed to localize a pulmonary nodule in a megavolt portal image. The method uses the characteristics of the nodule in a prior CT scan to enhance the nodule in the portal image and to identify the nodule region by level‐set segmentation. In a retrospective study, the method reduced the nodule position uncertainty by an average of 40% for seven out of the eight cases studied.
Evaluation of tear evaporation from ocular surface by functional infrared thermography
Authors: Tan Jen‐Hong , Ng E. Y. K. , Acharya U. Rajendra 
Published: November 2010

Purpose:A novel technique was developed to measure tear evaporation and monitor its variation with respect to time, for the studying of ocular physiology based on dynamic functional infrared thermography and the first law of thermodynamics using the measured ocular surface temperatures (OSTs). This is a noninvasive, noncontact temperature measuring method that is widely applied in the field of biomedicine.Methods:A simple method based on the ocular thermal data was proposed to measure the rate of tear evaporation. The OST of 60 normal subjects were recorded in the form of sequential thermal images. For each thermal sequence, the ocular region was selected and warped to a standard form. Thermal data within the regions were processed, on the basis of the first law of thermodynamics to derive the evaporation rate.Results:For elder subjects (aged above 35), the rate was determined to be and for younger subjects, the rate was . The corneal rate of evaporation in elder subjects was found statistically larger than their younger counterparts. The rate of blinking was observed to be related to the variation of evaporation rate.Conclusions:The authors have measured the evaporation rate on a sequence of thermographic images. A region of interest was selected at first and the same region on all the images were warped into a standard form. Calculations were performed based on the thermal data in those regions to obtain the values of interest. The authors found that the tear evaporation rate for subjects of all age groups was and the corneal tear evaporation was higher in elder subjects. The corneal rate of evaporation fluctuated in a larger magnitude in subjects who blinked more than average.
A feasibility study of photosensor charge signal transmission to preamplifier using long cable for development of hybrid PET‐MRI
Authors: Kang Jihoon , Choi Yong , Hong Key Jo , Jung Jin Ho , Hu Wei , Huh Yoon Suk , Lim Hyunkeong , Kim Byung‐Tae 
Published: November 2010

Purpose:A new positron emission tomography (PET) detector signal processing method, the charge signal transmission approach, is proposed for the development of a hybrid PET‐magnetic resonance imaging (MRI). A number of experiments were performed to demonstrate that the Geiger‐mode avalanche photodiode (GAPD) charge output could be transmitted to a preamplifier using a long cable without degrading the PET signal performance.Methods:A PET module consisted of LYSO and a GAPD with a array. The GAPD output was transmitted to the preamplifier through flexible flat cables. The effect of the cable length on the PET performance was examined using seven different lengths ranging from 10 to 300 cm outside and inside the 7 T animal MRI. Four parameters (rise time, fall time, amplitude, and area of the preamplifier output) were measured as a function of the cable length using a 10 GS/s oscilloscope and three parameters (photopeak position, energy resolution, and time resolution) were measured using a 100 MS/s DAQ unit. The effect of the cable length on the MR phantom images was investigated. In addition, the effect of the PET module configuration on its temperature stability was assessed by acquiring the energy and time spectra.Results:There were no significant changes in the PET module performance as a function of the cable length, both outside and inside MRI. The performance changes in energy information, such as the amplitude, area, photopeak position, and energy resolution, were with cable lengths ranging from 10 to 300 cm and the change in the time resolution was . There were no obvious artifacts or changes in the line profile in the MR phantom images. Moreover, no manifest changes in the photopeak position and coincidence counting rate were observed in the PET modules employing the charge signal transmission approach, whereas considerable degradation of the PET module performance was observed in the voltage signal transmission approach.Conclusions:This study demonstrated that it is feasible to design a hybrid PET‐MRI using the charge signal transmission approach, which is expected to have more advantages than other approaches.