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 Australasian Physical & Engineering Sciences in Medicine   [SJR: 0.293]   [H-I: 19]   [1 followers]  Follow         Hybrid journal (It can contain Open Access articles)    ISSN (Print) 0158-9938 - ISSN (Online) 1879-5447    Published by Springer-Verlag  [2352 journals]
• Erratum to: Short tangential arcs in VMAT based breast and chest wall
radiotherapy lead to conformity of the breast dose with lesser cardiac and
lung doses: a prospective study of breast conservation and mastectomy
patients
• Authors: Anusheel Munshi; Biplab Sarkar; Satheeshkumar Anbazhagan; Upendra K. Giri; Harpreet Kaur; Kanan Jassal; Tharmar Ganesh; Bidhu Kalyan Mohanti
Pages: 737 - 737
PubDate: 2017-09-01
DOI: 10.1007/s13246-017-0562-2
Issue No: Vol. 40, No. 3 (2017)

• Assessment of the relative contribution of volume and concentration
changes in Yttrium-90 labelled resin microspheres on ionization chamber
measurements
• Authors: Nicholas Forwood; Kathy P. Willowson; Michael Tapner; Dale L. Bailey
PubDate: 2017-11-17
DOI: 10.1007/s13246-017-0601-z

• Design of an optimum Poincaré plane for extracting meaningful samples
from eeg signals
• Authors: Babak Sharif; Amir Homayoun Jafari
Abstract: Biosignals are considered as important sources of data for diagnosing and detecting abnormalities, and modeling dynamics in the body. These signals are usually analyzed using features taken from time and frequency domain. In theory‚ these dynamics can also be analyzed utilizing Poincaré plane that intersects system’s trajectory. However‚ selecting an appropriate Poincaré plane is a crucial part of extracting best Poincaré samples. There is no unique way to choose a Poincaré plane‚ because it is highly dependent to the system dynamics. In this study, a new algorithm is introduced that automatically selects an optimum Poincaré plane able to transfer maximum information from EEG time series to a set of Poincaré samples. In this algorithm‚ EEG time series are first embedded; then a parametric Poincaré plane is designed and finally the parameters of the plane are optimized using genetic algorithm. The presented algorithm is tested on EEG signals and the optimum Poincaré plane is obtained with more than 99% data information transferred. Results are compared with some typical method of creating Poinare samples and showed that the transferred information using with this method is higher. The generated samples can be used for feature extraction and further analysis.
PubDate: 2017-11-16
DOI: 10.1007/s13246-017-0599-2

• Optimization of a shorter variable-acquisition time for legs to achieve
true whole-body PET/CT images
• Authors: Takuro Umeda; Kenta Miwa; Taisuke Murata; Noriaki Miyaji; Kei Wagatsuma; Kazuki Motegi; Takashi Terauchi; Mitsuru Koizumi
Abstract: The present study aimed to qualitatively and quantitatively evaluate PET images as a function of acquisition time for various leg sizes, and to optimize a shorter variable-acquisition time protocol for legs to achieve better qualitative and quantitative accuracy of true whole-body PET/CT images. The diameters of legs to be modeled as phantoms were defined based on data derived from 53 patients. This study analyzed PET images of a NEMA phantom and three plastic bottle phantoms (diameter, 5.68, 8.54 and 10.7 cm) that simulated the human body and legs, respectively. The phantoms comprised two spheres (diameters, 10 and 17 mm) containing fluorine-18 fluorodeoxyglucose solution with sphere-to-background ratios of 4 at a background radioactivity level of 2.65 kBq/mL. All PET data were reconstructed with acquisition times ranging from 10 to 180, and 1200 s. We visually evaluated image quality and determined the coefficient of variance (CV) of the background, contrast and the quantitative %error of the hot spheres, and then determined two shorter variable-acquisition protocols for legs. Lesion detectability and quantitative accuracy determined based on maximum standardized uptake values (SUVmax) in PET images of a patient using the proposed protocols were also evaluated. A larger phantom and a shorter acquisition time resulted in increased background noise on images and decreased the contrast in hot spheres. A visual score of ≥ 1.5 was obtained when the acquisition time was ≥ 30 s for three leg phantoms, and ≥ 120 s for the NEMA phantom. The quantitative %errors of the 10- and 17-mm spheres in the leg phantoms were ± 15 and ± 10%, respectively, in PET images with a high CV (scan < 30 s). The mean SUVmax of three lesions using the current fixed-acquisition and two proposed variable-acquisition time protocols in the clinical study were 3.1, 3.1 and 3.2, respectively, which did not significantly differ. Leg acquisition time per bed position of even 30–90 s allows axial equalization, uniform image noise and a maximum ± 15% quantitative accuracy for the smallest lesion. The overall acquisition time was reduced by 23–42% using the proposed shorter variable than the current fixed-acquisition time for imaging legs, indicating that this is a useful and practical protocol for routine qualitative and quantitative PET/CT assessment in the clinical setting.
PubDate: 2017-11-02
DOI: 10.1007/s13246-017-0596-5

• A model based on the Pennes bioheat transfer equation is valid in normal
brain tissue but not brain tissue suffering focal ischaemia
• Authors: Thomas Lillicrap; Murat Tahtalı; Andrew Neely; Xiaofei Wang; Andrew Bivard; Christian Lueck
Abstract: Ischaemic stroke is a major public health issue in both developed and developing nations. Hypothermia is believed to be neuroprotective in cerebral ischaemia. Conversely, elevated brain temperature is associated with poor outcome after ischaemic stroke. Mechanisms of heat exchange in normally-perfused brain are relatively well understood, but these mechanisms have not been studied as extensively during focal cerebral ischaemia. A finite element model (FEM) of heat exchange during focal ischaemia in the human brain was developed, based on the Pennes bioheat equation. This model incorporated healthy (normally-perfused) brain tissue, tissue that was mildly hypoperfused but not at risk of cell death (referred to as oligaemia), tissue that was hypoperfused and at risk of death but not dead (referred to as penumbra) and tissue that had died as a result of ischaemia (referred to as infarct core). The results of simulations using this model were found to match previous in-vivo temperature data for normally-perfused brain. However, the results did not match what limited data are available for hypoperfused brain tissue, in particular the penumbra, which is the focus of acute neuroprotective treatments such as hypothermia. These results suggest that the assumptions of the Pennes bioheat equation, while valid in the brain under normal circumstances, are not valid during focal ischaemia. Further investigation into the heat exchange profiles that do occur during focal ischaemia may yield results for clinical trials of therapeutic hypothermia.
PubDate: 2017-11-02
DOI: 10.1007/s13246-017-0595-6

• Assessment for facial nerve paralysis based on facial asymmetry
• Authors: Song Anping; Xu Guoliang; Ding Xuehai; Song Jiaxin; Xu Gang; Zhang Wu
Abstract: Facial nerve paralysis (FNP) is a loss of facial movement due to facial nerve damage, which will lead to significant physical pain and abnormal function in patients. Traditional FNP grading methods are solely based on clinician’s judgment and are time-consuming and subjective. Hence, an accurate, quantitative and objective method of evaluating FNP is proposed for constructing a standard system, which will be an invaluable tool for clinicians who treat the patient with FNP. In this paper, we introduce a novel method for quantitative assessment of FNP which combines an effective facial landmark estimation (FLE) algorithm and facial asymmetrical feature (FAF) by processing facial movement image. The facial landmarks can be detected automatically and accurately using FLE. The FAF is based on the angle of key facial landmark connection and mirror degree of multiple regions on human face. Our method provides significant contribution as it describes the displacement of facial organ and the changes of facial organ exposure during performing facial movements. Experiments show that our method is effective, accurate and convenient in practice, which is beneficial to FNP diagnosis and personalized rehabilitation therapy for each patient.
PubDate: 2017-10-31
DOI: 10.1007/s13246-017-0597-4

• Investigating the impact of treatment delivery uncertainties on treatment
effectiveness for lung SABR
• Authors: Samuel J Blake; Sankar Arumugam; Lois Holloway; Shalini Vinod; Cesar Ochoa; Penny Phan; Christian Rønn Hansen; David I Thwaites
Abstract: To quantify the impact of treatment delivery uncertainties on lung stereotactic ablative body radiotherapy (SABR) plans for step-and-shoot intensity-modulated radiotherapy (ssIMRT) and volumetric modulated arc therapy (VMAT). Baseline ssIMRT and VMAT treatment plans were generated for a cohort of 18 lung SABR patients. Modified plans were generated for each baseline plan by systematically varying gantry and collimator angles between − 5 and + 5 degrees, as well as multi-leaf collimator (MLC) leaf position errors of magnitude between 1 and 5 mm in both directions (i.e. leaf banks shifted either in the same (Type 1) or opposite (Type 2) directions). Planning target volume (PTV), spinal cord and healthy lung dose-volume histogram (DVH) metrics were compared between the modified and baseline plans. Collimator and gantry angle uncertainties did not significantly impact any of the PTV DVH metrics considered. MLC shifts of 5 mm resulted in average V95% changes of $$-\,10\%$$ (Type 1) and $$-\,33\%$$ (Type 2) and average $$\text{V}_{100\%}$$ changes of $$-\,17\%$$ (Type 1) and $$-\,44\%$$ (Type 2) for ssIMRT and VMAT plans. Comparatively, MLC shifts of − 2 mm resulted in average $$\text{V}_{95\%}$$ changes of $$-\,1\%$$ (Type 1) and $$-\,3.5\%$$ (Type 2) and average $$\text{V}_{100\%}$$ changes of $$-\,3\%$$ (Type 1) and $$-\,12\%$$ (Type 2) for ssIMRT and VMAT plans. ssIMRT gantry angle uncertainties impacted spinal cord DVH metrics the most, with increases in $$\text{D} 0.1 \text{cc}$$ of $$9\%$$ occurring for a 1 degree shift. Type 2 MLC modifications impacted all OAR DVH metrics substantially with differences in spinal cord $$\text{D}_{\text{max}}$$ (ssIMRT) and healthy lung $$\text{V} 20 \text{Gy}$$ (VMAT) exceeding $$40\%$$ for 5 mm shifts. Uncertainties in MLC leaf positions affected target and OAR DVH metrics more than collimator or gantry angle uncertainties for lung SABR plans. Less patient-to-patient variation occurred from delivery uncertainties in VMAT than ssIMRT.
PubDate: 2017-10-30
DOI: 10.1007/s13246-017-0591-x

• Grid mapping: a novel method of signal quality evaluation on a single lead
electrocardiogram
• Authors: Yanjun Li; Xiaoying Tang
Abstract: Diagnosis of long-term electrocardiogram (ECG) calls for automatic and accurate methods of ECG signal quality estimation, not only to lighten the burden of the doctors but also to avoid misdiagnoses. In this paper, a novel waveform-based method of phase-space reconstruction for signal quality estimation on a single lead ECG was proposed by projecting the amplitude of the ECG and its first order difference into grid cells. The waveform of a single lead ECG was divided into non-overlapping episodes (Ts = 10, 20, 30 s), and the number of grids in both the width and the height of each map are in the range [20, 100] (NX = NY = 20, 30, 40, … 90, 100). The blank pane ratio (BPR) and the entropy were calculated from the distribution of ECG sampling points which were projected into the grid cells. Signal Quality Indices (SQI) bSQI and eSQI were calculated according to the BPR and the entropy, respectively. The MIT-BIH Noise Stress Test Database was used to test the performance of bSQI and eSQI on ECG signal quality estimation. The signal-to-noise ratio (SNR) during the noisy segments of the ECG records in the database is 24, 18, 12, 6, 0 and − 6 dB, respectively. For the SQI quantitative analysis, the records were divided into three groups: good quality group (24, 18 dB), moderate group (12, 6 dB) and bad quality group (0, − 6 dB). The classification among good quality group, moderate quality group and bad quality group were made by linear support-vector machine with the combination of the BPR, the entropy, the bSQI and the eSQI. The classification accuracy was 82.4% and the Cohen’s Kappa coefficient was 0.74 on a scale of NX = 40 and Ts = 20 s. In conclusion, the novel grid mapping offers an intuitive and simple approach to achieving signal quality estimation on a single lead ECG.
PubDate: 2017-10-26
DOI: 10.1007/s13246-017-0594-7

• Accuracy of the Garmin 920 XT HRM to perform HRV analysis
• Authors: Johan Cassirame; Romain Vanhaesebrouck; Simon Chevrolat; Laurent Mourot
Abstract: Heart rate variability (HRV) analysis is widely used to investigate autonomous cardiac drive. This method requires periodogram measurement, which can be obtained by an electrocardiogram (ECG) or from a heart rate monitor (HRM), e.g. the Garmin 920 XT device. The purpose of this investigation was to assess the accuracy of RR time series measurements from a Garmin 920 XT HRM as compared to a standard ECG, and to verify whether the measurements thus obtained are suitable for HRV analysis. RR time series were collected simultaneously with an ECG (Powerlab system, AD Instruments, Castell Hill, Australia) and a Garmin XT 920 in 11 healthy subjects during three conditions, namely in the supine position, the standing position and during moderate exercise. In a first step, we compared RR time series obtained with both tools using the Bland and Altman method to obtain the limits of agreement in all three conditions. In a second step, we compared the results of HRV analysis between the ECG RR time series and Garmin 920 XT series. Results show that the accuracy of this system is in accordance with the literature in terms of the limits of agreement. In the supine position, bias was 0.01, − 2.24, + 2.26 ms; in the standing position, − 0.01, − 3.12, + 3.11 ms respectively, and during exercise, − 0.01, − 4.43 and + 4.40 ms. Regarding HRV analysis, we did not find any difference for HRV analysis in the supine position, but the standing and exercise conditions both showed small modifications.
PubDate: 2017-10-20
DOI: 10.1007/s13246-017-0593-8

• Successful implementation of Virtual Environment for Radiotherapy Training
(VERT) in Medical Physics education: The University of Sydney’s initial
experience and recommendations
• Authors: Yobelli A. Jimenez; Christian Rønn Hansen; Prabhjot Juneja; David I. Thwaites
Abstract: This report outlines the University of Sydney’s initial experience with the Virtual Environment for Radiotherapy Training (VERT) system in the Master of Medical Physics program. VERT is a commercially available system, simulating linear accelerators, patient computed tomography (CT) sets, plans and treatment delivery. It was purpose built for radiation therapy (RT) education and offers learners the opportunity to gain knowledge and skills within an interactive, risk-free environment. The integration of VERT into the RT physics module of the Master of Medical Physics program was intended to enhance student knowledge and skills relevant to the curriculum’s learning objectives, and to alleviate some of the burden associated with student access to clinical equipment. Three VERT practical sessions were implemented: “RT treatment planning systems”, “(CT) Anatomy for physicists” and “Linear accelerator measurements”. Our experience and student evaluations were positive and demonstrated the viability of VERT for medical physics (MP) student education. We anticipate that integration of VERT into MP teaching is a valuable addition to traditional methods and can aid MP students’ understanding and readiness for practice. Additional evaluations should be conducted to ascertain VERT’s role in delivering efficient quantity and quality of MP education, and its potential in alleviating burdens placed on clinical departments.
PubDate: 2017-10-13
DOI: 10.1007/s13246-017-0592-9

• A survey of modulated radiotherapy use in Australia &amp; New Zealand
in 2015
• Authors: Jeffrey Barber; Philip Vial; Paul White; Nick Menzies; Shrikant Deshpande; Regina Bromley; Nick Bennie; Shan Yau; Kristie Harrison
Abstract: A survey of radiation oncology medical physics departments across Australia and New Zealand was conducted to assess the usage, commissioning and quality assurance of modulated radiotherapy techniques such as IMRT and VMAT. Survey responses were collected in April–May 2015 to snapshot current practice and historical implementation. The survey asked 142 questions, and is the most detailed survey of its kind published to date. Analysis of results at overall department level, as well as sub-analysis for different equipment and techniques in use, was performed. Results show a high prevalence of IMRT and VMAT in use, and demonstrate the large heterogeneity in clinical practice and experience across the region.
PubDate: 2017-10-12
DOI: 10.1007/s13246-017-0590-y

• Proposed patient motion monitoring system using feature point tracking
with a web camera
• Authors: Hideharu Miura; Shuichi Ozawa; Takaaki Matsuura; Kiyoshi Yamada; Yasushi Nagata
Abstract: Patient motion monitoring systems play an important role in providing accurate treatment dose delivery. We propose a system that utilizes a web camera (frame rate up to 30 fps, maximum resolution of 640 × 480 pixels) and an in-house image processing software (developed using Microsoft Visual C++ and OpenCV). This system is simple to use and convenient to set up. The pyramidal Lucas–Kanade method was applied to calculate motions for each feature point by analysing two consecutive frames. The image processing software employs a color scheme where the defined feature points are blue under stable (no movement) conditions and turn red along with a warning message and an audio signal (beeping alarm) for large patient movements. The initial position of the marker was used by the program to determine the marker positions in all the frames. The software generates a text file that contains the calculated motion for each frame and saves it as a compressed audio video interleave (AVI) file. We proposed a patient motion monitoring system using a web camera, which is simple and convenient to set up, to increase the safety of treatment delivery.
PubDate: 2017-10-06
DOI: 10.1007/s13246-017-0589-4

• Shielding of medical imaging X-ray facilities: a simple and practical
method
• Authors: Giovanni Bibbo
Abstract: The most widely accepted method for shielding design of X-ray facilities is that contained in the National Council on Radiation Protection and Measurements Report 147 whereby the computation of the barrier thickness for primary, secondary and leakage radiations is based on the knowledge of the distances from the radiation sources, the assumptions of the clinical workload, and usage and occupancy of adjacent areas. The shielding methodology used in this report is complex. With this methodology, the shielding designers need to make assumptions regarding the use of the X-ray room and the adjoining areas. Different shielding designers may make different assumptions resulting in different shielding requirements for a particular X-ray room. A more simple and practical method is to base the shielding design on the shielding principle used to shield X-ray tube housing to limit the leakage radiation from the X-ray tube. In this case, the shielding requirements of the X-ray room would depend only on the maximum radiation output of the X-ray equipment regardless of workload, usage or occupancy of the adjacent areas of the room. This shielding methodology, which has been used in South Australia since 1985, has proven to be practical and, to my knowledge, has not led to excess shielding of X-ray installations.
PubDate: 2017-10-05
DOI: 10.1007/s13246-017-0586-7

• The effect of beam interruption during FFF-VMAT plans for SBRT
• Authors: Seongjong Oh; Benjamin Lewis; Amy Watson; Siyong Kim; Taeho Kim
Abstract: To investigate the dosimetric effect of intended beam interruption during volumetric modulated arc therapy (VMAT) with flattening filter free (FFF) beam for exploring the possibility of deep inspiration breath hold stereotactic body radiation therapy (SBRT). A total of ten SBRT plans with 6 and 10 MV FFF beams were retrospectively selected. All plans consisted of four partial arcs, except one plan with six partial arcs. We delivered the plans using a Varian Truebeam™ with three different scenarios; without interruption (0int), with one intentional interruption (1int), or with two intentional interruptions (2int), per each partial arc. The treatment log files were exported from the treatment console, and the variations in delivered MU were evaluated at the beam interruption angles. The dose distributions were also measured using a 3D cylindrical diode array detector, ArcCHECK™. The 2D global gamma evaluations were performed, compared to the planned dose distribution, with 3%/3 and 4%/2 mm passing criterion. The dose difference (DD) was also determined between uninterrupted and interrupted data with 3, 2, 1, and 0.5% of global maximum dose. The interruption caused a total increase of 0.14 ± 0.05% and 0.25 ± 0.08% of the total planned MU, ranging from 1746 to 3261 MU, at the interrupted angles in 1int and 2int, respectively. All global gamma passing rates satisfied our clinical threshold of 90%, and the differences of passing rates were less than 0.3% on average with both criterions. All measured 1int and 2int data were within 3% DD from 0int measured data. For 6 MV FFF beams, the average passing rate with 2, 1, and 0.5% DD were 99.9 ± 0.2%, 92.3 ± 12.0%, and 81.9 ± 24.9%, respectively, between 0int and 1int, and 99.8 ± 0.4%, 92.1%12.4%, and 80.7 ± 26.5%, respectively, between 0int and 2int. For 10 MV FFF beams, the average passing rate with 2, 1, and 0.5% DD were 100.0 ± 0.2%, 95.4 ± 9.4% and 87.0 ± 19.8%, respectively, between 0int and 1int, and 99.9 ± 0.3%, 95.4 ± 9.7%, and 87.2 ± 21.3% between 0int and 2int. The dosimetric impact of beam interruption was investigated with small field and high dose rate FFF-VMAT SBRT plans. The delivered dose distributions with up to 12 interruptions per plan were still clinically acceptable. Only minimal changes were observed in Gamma, DD, and log file analysis.
PubDate: 2017-10-02
DOI: 10.1007/s13246-017-0588-5

• Validating an image segmentation program devised for staging lymphoma
• Authors: Anthony Slattery
Abstract: Hybrid positron emission tomography–computed tomography (PET–CT) imaging systems are an important tool for assessing the progression of lymphoma. PET–CT systems offer the ability to quantitatively assess lymphocytic bone involvement throughout the body. There is no standard methodology for staging lymphoma patients using PET–CT images. Automatic image segmentation algorithms could offer medical specialists a means to evaluate bone involvement from PET–CT images in a consistent manner. To devise and validate an image segmentation program that may assist staging lymphoma by determining the degree of bone involvement based from PET–CT studies. A custom-made program was developed to segment regions-of-interest from images by utilising an enhanced fuzzy clustering technique that incorporates spatial information. The program was subsequently tested on digital and physical phantoms using four different performance metrics before being employed to extract the bony regions of clinical PET–CT images acquired from 248 patients staged for lymphoma. The algorithm was satisfactorily able to delineate regions-of-interest within all phantoms. When applied to the clinical PET–CT images, the algorithm was capable of accurately segmenting bony regions in less than half of the subjects (n = 103). The performance of the algorithm was adversely affected by the presence of oral contrast, metal implants and the poor image quality afforded by low dose CT images in general. Significant changes are necessary before the algorithm can be employed clinically in an unsupervised fashion. However, with further work performed, the algorithm could potentially prove useful for medical specialists staging lymphoma in the future.
PubDate: 2017-10-02
DOI: 10.1007/s13246-017-0587-6

• Heartbeat detection in multimodal physiological signals using signal
quality assessment based on sample entropy
• Abstract: This paper presents a novel technique to identify heartbeats in multimodal data using electrocardiogram (ECG) and arterial blood pressure (ABP) signals. Multiple physiological signals such as ECG, ABP, and Respiration are often recorded in parallel from the activity of heart. These signals generally possess related information as they are generated by the same physical system. The ECG and ABP correspond to the same phenomenon of contraction and relaxation activity of heart. Multiple signals acquired from various sensors are generally processed independently, thus discarding the information from other measurements. In the estimation of heart rate and heart rate variability, the R peaks are generally identified from ECG signal. Efficient detection of R-peaks in electrocardiogram (ECG) is a key component in the estimation of clinically relevant parameters from ECG. However, when the signal is severely affected by undesired artifacts, this becomes a challenging task. Sometimes in clinical environment, other physiological signals reflecting the cardiac activity such as ABP signal are also acquired simultaneously. Under the availability of such multimodal signals, the accuracy of R peak detection methods can be improved using sensor-fusion techniques. In the proposed method, the sample entropy (SampEn) is used as a metric for assessing the noise content in the physiological signal and the R peaks in ECG and the systolic peaks in ABP signals are fused together to enhance the efficiency of heartbeat detection. The proposed method was evaluated on the 100 records from the computing in cardiology challenge 2014 training data set. The performance parameters are: sensitivity (Se) and positive predictivity (PPV). The unimodal R peaks detector achieved: Se gross = 99.40%, PPV gross = 99.29%, Se average = 99.37%, PPV average = 99.29%. Similarly unimodal BP delineator achieved Se gross = 99.93%, PPV gross = 99.99%, Se average = 99.93%, PPV average = 99.99% whereas, the proposed multimodal beat detector achieved: Se gross = 99.65%, PPV gross = 99.91%, Se average = 99.68%, PPV average = 99.91%.
PubDate: 2017-09-08
DOI: 10.1007/s13246-017-0585-8

• Diagnosis of multiple sclerosis from EEG signals using nonlinear methods
• Abstract: EEG signals have essential and important information about the brain and neural diseases. The main purpose of this study is classifying two groups of healthy volunteers and Multiple Sclerosis (MS) patients using nonlinear features of EEG signals while performing cognitive tasks. EEG signals were recorded when users were doing two different attentional tasks. One of the tasks was based on detecting a desired change in color luminance and the other task was based on detecting a desired change in direction of motion. EEG signals were analyzed in two ways: EEG signals analysis without rhythms decomposition and EEG sub-bands analysis. After recording and preprocessing, time delay embedding method was used for state space reconstruction; embedding parameters were determined for original signals and their sub-bands. Afterwards nonlinear methods were used in feature extraction phase. To reduce the feature dimension, scalar feature selections were done by using T-test and Bhattacharyya criteria. Then, the data were classified using linear support vector machines (SVM) and k-nearest neighbor (KNN) method. The best combination of the criteria and classifiers was determined for each task by comparing performances. For both tasks, the best results were achieved by using T-test criterion and SVM classifier. For the direction-based and the color-luminance-based tasks, maximum classification performances were 93.08 and 79.79% respectively which were reached by using optimal set of features. Our results show that the nonlinear dynamic features of EEG signals seem to be useful and effective in MS diseases diagnosis.
PubDate: 2017-09-08
DOI: 10.1007/s13246-017-0584-9

• Winning images from the Photography in Medical Physics (PiMP) competition
• PubDate: 2017-09-04
DOI: 10.1007/s13246-017-0581-z

• A comprehensive dose assessment of irradiated hand by iridium-192 source
• Authors: S. M. Hosseini Pooya; M. R. Dashtipour; R. Paydar; F. Mianji; B. Pourshahab
Abstract: Among the various incidents in industrial radiography, inadvertent handling of sources by hands is one of the most frequent incidents in which some parts of the hands may be locally exposed to high doses. An accurate assessment of extremity dose assists medical doctors in selecting appropriate treatments, preventing the injury expansion in the region. In this study, a phantom was designed to simulate a fisted hand of a radiographer when the worker holds a radioactive source in their hands. The local doses were measured using implanted TLDs in the phantom at different distances from a source. Furthermore, skin dose distribution was measured by Gaf-chromic films in the palm region of the phantom. The reliability of the measurements has been studied via analytical as well as Monte-Carlo simulation methods. The results showed that the new phantom design can be used reliably in extremity dose assessments, particularly at the points next to the source.
PubDate: 2017-09-04
DOI: 10.1007/s13246-017-0568-9

• Differences in grip force control between young and late middle-aged
• Authors: Lianrong Zheng; Kunyang Li; Qian Wang; Wenhui Chen; Rong Song; Guanzheng Liu
Abstract: Grip force control is a crucial function for human to guarantee the quality of life. To examine the effects of age on grip force control, 10 young adults and 11 late middle-aged adults participated in visually guided tracking tasks using different target force levels (25, 50, and 75% of the subject’s maximal grip force). Multiple measures were used to evaluate the tracking performance during force rising phase and force maintenance phase. The measurements include the rise time, fuzzy entropy, mean force percentage, coefficient of variation, and target deviation ratio. The results show that the maximal grip force was significantly lower in the late middle-aged adults than in the young adults. The time of rising phase was systematically longer among late middle-aged adults. The fuzzy entropy is a useful indicator for quantitating the force variability of the grip force signal at higher force levels. These results suggest that the late middle-aged adults applied a compensatory strategy that allow allows for sufficient time to reach the required grip force and reduce the impact of the early and subtle degenerative changes in hand motor function.
PubDate: 2017-08-22
DOI: 10.1007/s13246-017-0567-x

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