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Special Issue "Medical & Biological Imaging"

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A special issue of Sensors (ISSN 1424-8220).

Deadline for manuscript submissions: closed (31 January 2013)

Special Issue Editor

Guest Editor
Dr. Yudong Zhang (Website)

Brain Imaging Lab, Division of Child Psychiatry, Unit 74, New York State Psychiatric Institute, 1051 Riverside Drive, New York, NY 10032, USA
Interests: magnetic resonance imaging; magnetic resonance spectroscopy imaging

Special Issue Information

Dear Colleagues,

“Medical & Biological Imaging” is a discipline and in its widest sense, it incorporates radiology, nuclear medicine, investigative radiological sciences, endoscopy, thermography, medical photography and microscopy.

In the clinical context, "invisible light" medical imaging is generally equated to radiology or "clinical imaging" and the medical practitioner responsible for interpreting the images is a radiologist. "Visible light" medical imaging involves digital video or still pictures that can be seen without special equipment. Dermatology and wound care are two modalities that utilize visible light imagery. Diagnostic radiography designates the technical aspects of medical imaging and in particular the acquisition of medical images. The radiographer or radiologic technologist is usually responsible for acquiring medical images of diagnostic quality, although some radiological interventions are performed by radiologists. While radiology is an evaluation of anatomy, nuclear medicine provides functional assessment.

As a field of scientific investigation, medical imaging constitutes a sub-discipline of biomedical engineering, medical physics or medicine depending on the context: Research and development in the area of instrumentation, image acquisition, modeling and quantification are usually the preserve of biomedical engineering, medical physics and computer science; Research into the application and interpretation of medical images is usually the preserve of radiology and the medical sub-discipline relevant to medical condition or area of medical science under investigation. Many of the techniques developed for medical imaging also have scientific and industrial applications.

Dr. Yudong Zhang
Guest Editor

Submission

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are refereed through a peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Sensors is an international peer-reviewed Open Access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs).


Keywords

  • bioluminescence imaging
  • calcium imaging
  • diffuse Optical imaging
  • diffusion-weighted imaging
  • fluorescence lifetime imaging
  • gallium imaging
  • magnetic resonance imaging
  • medical imaging
  • microscopy
  • molecular imaging
  • optical imaging
  • optoacoustic imaging
  • photoacoustic imaging
  • ultrasound imaging
  • image processing and analysis
  • compressed sensing
  • artificial intelligence
  • pattern recognition
  • data mining

Published Papers (25 papers)

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Open AccessArticle An Early Underwater Artificial Vision Model in Ocean Investigations via Independent Component Analysis
Sensors 2013, 13(7), 9104-9131; doi:10.3390/s130709104
Received: 8 June 2013 / Revised: 6 July 2013 / Accepted: 8 July 2013 / Published: 16 July 2013
Cited by 3 | PDF Full-text (4525 KB) | HTML Full-text | XML Full-text
Abstract
Underwater vision is one of the dominant senses and has shown great prospects in ocean investigations. In this paper, a hierarchical Independent Component Analysis (ICA) framework has been established to explore and understand the functional roles of the higher order statistical structures [...] Read more.
Underwater vision is one of the dominant senses and has shown great prospects in ocean investigations. In this paper, a hierarchical Independent Component Analysis (ICA) framework has been established to explore and understand the functional roles of the higher order statistical structures towards the visual stimulus in the underwater artificial vision system. The model is inspired by characteristics such as the modality, the redundancy reduction, the sparseness and the independence in the early human vision system, which seems to respectively capture the Gabor-like basis functions, the shape contours or the complicated textures in the multiple layer implementations. The simulation results have shown good performance in the effectiveness and the consistence of the approach proposed for the underwater images collected by autonomous underwater vehicles (AUVs). Full article
(This article belongs to the Special Issue Medical & Biological Imaging)
Open AccessArticle Two Phase Non-Rigid Multi-Modal Image Registration Using Weber Local Descriptor-Based Similarity Metrics and Normalized Mutual Information
Sensors 2013, 13(6), 7599-7617; doi:10.3390/s130607599
Received: 3 April 2013 / Revised: 24 May 2013 / Accepted: 5 June 2013 / Published: 13 June 2013
Cited by 2 | PDF Full-text (1054 KB) | HTML Full-text | XML Full-text
Abstract
Non-rigid multi-modal image registration plays an important role in medical image processing and analysis. Existing image registration methods based on similarity metrics such as mutual information (MI) and sum of squared differences (SSD) cannot achieve either high registration accuracy or high registration [...] Read more.
Non-rigid multi-modal image registration plays an important role in medical image processing and analysis. Existing image registration methods based on similarity metrics such as mutual information (MI) and sum of squared differences (SSD) cannot achieve either high registration accuracy or high registration efficiency. To address this problem, we propose a novel two phase non-rigid multi-modal image registration method by combining Weber local descriptor (WLD) based similarity metrics with the normalized mutual information (NMI) using the diffeomorphic free-form deformation (FFD) model. The first phase aims at recovering the large deformation component using the WLD based non-local SSD (wldNSSD) or weighted structural similarity (wldWSSIM). Based on the output of the former phase, the second phase is focused on getting accurate transformation parameters related to the small deformation using the NMI. Extensive experiments on T1, T2 and PD weighted MR images demonstrate that the proposed wldNSSD-NMI or wldWSSIM-NMI method outperforms the registration methods based on the NMI, the conditional mutual information (CMI), the SSD on entropy images (ESSD) and the ESSD-NMI in terms of registration accuracy and computation efficiency. Full article
(This article belongs to the Special Issue Medical & Biological Imaging)
Open AccessArticle 3D Preoperative Planning in the ER with OsiriX®: When There is No Time for Neuronavigation
Sensors 2013, 13(5), 6477-6491; doi:10.3390/s130506477
Received: 1 April 2013 / Revised: 1 May 2013 / Accepted: 8 May 2013 / Published: 16 May 2013
Cited by 5 | PDF Full-text (1787 KB) | HTML Full-text | XML Full-text
Abstract
The evaluation of patients in the emergency room department (ER) through more accurate imaging methods such as computed tomography (CT) has revolutionized their assistance in the early 80s. However, despite technical improvements seen during the last decade, surgical planning in the ER [...] Read more.
The evaluation of patients in the emergency room department (ER) through more accurate imaging methods such as computed tomography (CT) has revolutionized their assistance in the early 80s. However, despite technical improvements seen during the last decade, surgical planning in the ER has not followed the development of image acquisition methods. The authors present their experience with DICOM image processing as a navigation method in the ER. The authors present 18 patients treated in the Emergency Department of the Hospital das Clínicas of the University of Sao Paulo. All patients were submitted to volumetric CT. We present patients with epidural hematomas, acute/subacute subdural hematomas and contusional hematomas. Using a specific program to analyze images in DICOM format (OsiriX®), the authors performed the appropriate surgical planning. The use of 3D surgical planning made it possible to perform procedures more accurately and less invasively, enabling better postoperative outcomes. All sorts of neurosurgical emergency pathologies can be treated appropriately with no waste of time. The three-dimensional processing of images in the preoperative evaluation is easy and possible even within the emergency care. It should be used as a tool to reduce the surgical trauma and it may dispense methods of navigation in many cases. Full article
(This article belongs to the Special Issue Medical & Biological Imaging)
Open AccessArticle Performance Evaluation of a Modular Detector Unit for X-Ray Computed Tomography
Sensors 2013, 13(4), 5167-5180; doi:10.3390/s130405167
Received: 6 February 2013 / Revised: 15 April 2013 / Accepted: 16 April 2013 / Published: 18 April 2013
Cited by 1 | PDF Full-text (808 KB) | HTML Full-text | XML Full-text
Abstract
A research prototype CT scanner is currently under development in our lab. One of the key components in this project is the CT detector. This paper describes the design and performance evaluation of the modular CT detector unit for our proposed scanner. [...] Read more.
A research prototype CT scanner is currently under development in our lab. One of the key components in this project is the CT detector. This paper describes the design and performance evaluation of the modular CT detector unit for our proposed scanner. It consists of a Photodiode Array Assembly which captures irradiating X-ray photons and converts the energy into electrical current, and a mini Data Acquisition System which performs current integration and converts the analog signal into digital samples. The detector unit can be easily tiled together to form a CT detector. Experiments were conducted to characterize the detector performance both at the single unit level and system level. The noise level, linearity and uniformity of the proposed detector unit were reported and initial imaging studies were also presented which demonstrated the potential application of the proposed detector unit in actual CT scanners. Full article
(This article belongs to the Special Issue Medical & Biological Imaging)
Open AccessArticle A Low-Cost, Computer-Interfaced Drawing Pad for fMRI Studies of Dysgraphia and Dyslexia
Sensors 2013, 13(4), 5099-5108; doi:10.3390/s130405099
Received: 20 March 2013 / Revised: 10 April 2013 / Accepted: 11 April 2013 / Published: 17 April 2013
Cited by 2 | PDF Full-text (877 KB) | HTML Full-text | XML Full-text
Abstract
We have developed a pen and writing tablet for use by subjects during fMRI scanning. The pen consists of two jacketed, multi-mode optical fibers routed to the tip of a hollowed-out ball-point pen. The pen has been further modified by addition of [...] Read more.
We have developed a pen and writing tablet for use by subjects during fMRI scanning. The pen consists of two jacketed, multi-mode optical fibers routed to the tip of a hollowed-out ball-point pen. The pen has been further modified by addition of a plastic plate to maintain a perpendicular pen-tablet orientation. The tablet is simply a non-metallic frame holding a paper print of continuously varying color gradients. The optical fibers are routed out of the MRI bore to a light-tight box in an adjacent control room. Within the box, light from a high intensity LED is coupled into one of the fibers, while the other fiber abuts a color sensor. Light from the LED exits the pen tip, illuminating a small spot on the tablet, and the resulting reflected light is routed to the color sensor. Given a lookup table of position for each color on the tablet, the coordinates of the pen on the tablet may be displayed and digitized in real-time. While simple and inexpensive, the system achieves sufficient resolution to grade writing tasks testing dysgraphic and dyslexic phenomena. Full article
(This article belongs to the Special Issue Medical & Biological Imaging)
Figures

Open AccessArticle Nonlinear Detection for a High Rate Extended Binary Phase Shift Keying System
Sensors 2013, 13(4), 4327-4347; doi:10.3390/s130404327
Received: 5 March 2013 / Revised: 16 March 2013 / Accepted: 28 March 2013 / Published: 28 March 2013
Cited by 4 | PDF Full-text (430 KB) | HTML Full-text | XML Full-text
Abstract
The algorithm and the results of a nonlinear detector using a machine learning technique called support vector machine (SVM) on an efficient modulation system with high data rate and low energy consumption is presented in this paper. Simulation results showed that the [...] Read more.
The algorithm and the results of a nonlinear detector using a machine learning technique called support vector machine (SVM) on an efficient modulation system with high data rate and low energy consumption is presented in this paper. Simulation results showed that the performance achieved by the SVM detector is comparable to that of a conventional threshold decision (TD) detector. The two detectors detect the received signals together with the special impacting filter (SIF) that can improve the energy utilization efficiency. However, unlike the TD detector, the SVM detector concentrates not only on reducing the BER of the detector, but also on providing accurate posterior probability estimates (PPEs), which can be used as soft-inputs of the LDPC decoder. The complexity of this detector is considered in this paper by using four features and simplifying the decision function. In addition, a bandwidth efficient transmission is analyzed with both SVM and TD detector. The SVM detector is more robust to sampling rate than TD detector. We find that the SVM is suitable for extended binary phase shift keying (EBPSK) signal detection and can provide accurate posterior probability for LDPC decoding. Full article
(This article belongs to the Special Issue Medical & Biological Imaging)
Open AccessArticle A Support-Based Reconstruction for SENSE MRI
Sensors 2013, 13(4), 4029-4040; doi:10.3390/s130404029
Received: 1 March 2013 / Revised: 22 March 2013 / Accepted: 22 March 2013 / Published: 25 March 2013
Cited by 6 | PDF Full-text (605 KB) | HTML Full-text | XML Full-text
Abstract
A novel, rapid algorithm to speed up and improve the reconstruction of sensitivity encoding (SENSE) MRI was proposed in this paper. The essence of the algorithm was that it iteratively solved the model of simple SENSE on a pixel-by-pixel basis in the [...] Read more.
A novel, rapid algorithm to speed up and improve the reconstruction of sensitivity encoding (SENSE) MRI was proposed in this paper. The essence of the algorithm was that it iteratively solved the model of simple SENSE on a pixel-by-pixel basis in the region of support (ROS). The ROS was obtained from scout images of eight channels by morphological operations such as opening and filling. All the pixels in the FOV were paired and classified into four types, according to their spatial locations with respect to the ROS, and each with corresponding procedures of solving the inverse problem for image reconstruction. The sensitivity maps, used for the image reconstruction and covering only the ROS, were obtained by a polynomial regression model without extrapolation to keep the estimation errors small. The experiments demonstrate that the proposed method improves the reconstruction of SENSE in terms of speed and accuracy. The mean square errors (MSE) of our reconstruction is reduced by 16.05% for a 2D brain MR image and the mean MSE over the whole slices in a 3D brain MRI is reduced by 30.44% compared to those of the traditional methods. The computation time is only 25%, 45%, and 70% of the traditional method for images with numbers of pixels in the orders of 103, 104, and 105–107, respectively. Full article
(This article belongs to the Special Issue Medical & Biological Imaging)
Figures

Open AccessArticle Evaluation of Moisture-Related Attenuation Coefficient and Water Diffusion Velocity in Human Skin Using Optical Coherence Tomography
Sensors 2013, 13(4), 4041-4050; doi:10.3390/s130404041
Received: 24 January 2013 / Revised: 9 March 2013 / Accepted: 20 March 2013 / Published: 25 March 2013
Cited by 2 | PDF Full-text (1420 KB) | HTML Full-text | XML Full-text
Abstract
In this study, time-resolved optical coherence tomography (OCT) scanning images of the process of water diffusion in the skin that illustrate the enhancement in the backscattered intensities due to the increased water concentration are presented. In our experiments, the water concentration in [...] Read more.
In this study, time-resolved optical coherence tomography (OCT) scanning images of the process of water diffusion in the skin that illustrate the enhancement in the backscattered intensities due to the increased water concentration are presented. In our experiments, the water concentration in the skin was increased by soaking the hand in water, and the same region of the skin was scanned and measured with the OCT system and a commercial moisture monitor every three minutes. To quantitatively analyze the moisture-related optical properties and the velocity of water diffusion in human skin, the attenuation coefficients of the skin, including the epidermis and dermis layers, were evaluated. Furthermore, the evaluated attenuation coefficients were compared with the measurements made using the commercial moisture monitor. The results demonstrate that the attenuation coefficient increases as the water concentration increases. Furthermore, by evaluating the positions of center-of mass of the backscattered intensities from OCT images, the diffusion velocity can be estimated. In contrast to the commercial moisture monitor, OCT can provide three-dimensional structural images of the skin and characterize its optical property, which together can be used to observe morphological changes and quantitatively evaluate the moisture-related attenuation coefficients in different skin layers. Full article
(This article belongs to the Special Issue Medical & Biological Imaging)
Open AccessCommunication Rank Awareness in Group-Sparse Recovery of Multi-Echo MR Images
Sensors 2013, 13(3), 3902-3921; doi:10.3390/s130303902
Received: 1 February 2013 / Revised: 21 February 2013 / Accepted: 7 March 2013 / Published: 20 March 2013
Cited by 5 | PDF Full-text (4117 KB) | HTML Full-text | XML Full-text
Abstract
This work addresses the problem of recovering multi-echo T1 or T2 weighted images from their partial K-space scans. Recent studies have shown that the best results are obtained when all the multi-echo images are reconstructed by simultaneously exploiting their intra-image spatial redundancy [...] Read more.
This work addresses the problem of recovering multi-echo T1 or T2 weighted images from their partial K-space scans. Recent studies have shown that the best results are obtained when all the multi-echo images are reconstructed by simultaneously exploiting their intra-image spatial redundancy and inter-echo correlation. The aforesaid studies either stack the vectorised images (formed by row or columns concatenation) as columns of a Multiple Measurement Vector (MMV) matrix or concatenate them as a long vector. Owing to the inter-image correlation, the thus formed MMV matrix or the long concatenated vector is row-sparse or group-sparse respectively in a transform domain (wavelets). Consequently the reconstruction problem was formulated as a row-sparse MMV recovery or a group-sparse vector recovery. In this work we show that when the multi-echo images are arranged in the MMV form, the thus formed matrix is low-rank. We show that better reconstruction accuracy can be obtained when the information about rank-deficiency is incorporated into the row/group sparse recovery problem. Mathematically, this leads to a constrained optimization problem where the objective function promotes the signal’s groups-sparsity as well as its rank-deficiency; the objective function is minimized subject to data fidelity constraints. The experiments were carried out on ex vivo and in vivo T2 weighted images of a rat's spinal cord. Results show that this method yields considerably superior results than state-of-the-art reconstruction techniques. Full article
(This article belongs to the Special Issue Medical & Biological Imaging)
Open AccessArticle Multipass Active Contours for an Adaptive Contour Map
Sensors 2013, 13(3), 3724-3738; doi:10.3390/s130303724
Received: 5 February 2013 / Revised: 5 March 2013 / Accepted: 11 March 2013 / Published: 15 March 2013
Cited by 5 | PDF Full-text (2308 KB) | HTML Full-text | XML Full-text
Abstract
Isocontour mapping is efficient for extracting meaningful information from a biomedical image in a topographic analysis. Isocontour extraction from real world medical images is difficult due to noise and other factors. As such, adaptive selection of contour generation parameters is needed. This [...] Read more.
Isocontour mapping is efficient for extracting meaningful information from a biomedical image in a topographic analysis. Isocontour extraction from real world medical images is difficult due to noise and other factors. As such, adaptive selection of contour generation parameters is needed. This paper proposes an algorithm for generating an adaptive contour map that is spatially adjusted. It is based on the modified active contour model, which imposes successive spatial constraints on the image domain. The adaptability of the proposed algorithm is governed by the energy term of the model. This work focuses on mammograms and the analysis of their intensity. Our algorithm employs the Mumford-Shah energy functional, which considers an image’s intensity distribution. In mammograms, the brighter regions generally contain significant information. Our approach exploits this characteristic to address the initialization and local optimum problems of the active contour model. Our algorithm starts from the darkest region; therefore, local optima encountered during the evolution of contours are populated in less important regions, and the important brighter regions are reserved for later stages. For an unrestricted initial contour, our algorithm adopts an existing technique without re-initialization. To assess its effectiveness and robustness, the proposed algorithm was tested on a set of mammograms. Full article
(This article belongs to the Special Issue Medical & Biological Imaging)
Open AccessArticle Fluorescent Imaging for Assessment of the Effect of Combined Application of Electroporation and Rifampicin on HaCaT Cells as a New Therapeutic Approach for Psoriasis
Sensors 2013, 13(3), 3625-3634; doi:10.3390/s130303625
Received: 11 January 2013 / Revised: 13 February 2013 / Accepted: 6 March 2013 / Published: 14 March 2013
PDF Full-text (637 KB) | HTML Full-text | XML Full-text
Abstract
The study aimed to clarify the role of electric pulses in combination with chemotherapy on the viability of keratinocyte cell line HaCaT, in the context of its application as a new therapeutic approach for psoriasis. The data show that electroporation of HaCaT [...] Read more.
The study aimed to clarify the role of electric pulses in combination with chemotherapy on the viability of keratinocyte cell line HaCaT, in the context of its application as a new therapeutic approach for psoriasis. The data show that electroporation of HaCaT cells in combination with rifampicin induces cytoskeleton disruption and increases permeability of cell monolayer due to cell-cell junctions’ interruption, visualized by fluorescent imaging of E-cadherin and actin integrity. This was accompanied with synergistic reduction of cell viability. The study proposes a new opportunity for more effective skin treatment than chemotherapy. The future application of this electrochemotherapeutic approach for combined local treatment of psoriasis may have serous benefits because of a high possibility to avoid side-effects of conventional chemotherapy. Full article
(This article belongs to the Special Issue Medical & Biological Imaging)
Open AccessArticle Noninvasive Vascular Displacement Estimation for Relative Elastic Modulus Reconstruction in Transversal Imaging Planes
Sensors 2013, 13(3), 3341-3357; doi:10.3390/s130303341
Received: 14 February 2013 / Revised: 7 March 2013 / Accepted: 8 March 2013 / Published: 11 March 2013
Cited by 6 | PDF Full-text (689 KB) | HTML Full-text | XML Full-text
Abstract
Atherosclerotic plaque rupture can initiate stroke or myocardial infarction. Lipid-rich plaques with thin fibrous caps have a higher risk to rupture than fibrotic plaques. Elastic moduli differ for lipid-rich and fibrous tissue and can be reconstructed using tissue displacements estimated from intravascular [...] Read more.
Atherosclerotic plaque rupture can initiate stroke or myocardial infarction. Lipid-rich plaques with thin fibrous caps have a higher risk to rupture than fibrotic plaques. Elastic moduli differ for lipid-rich and fibrous tissue and can be reconstructed using tissue displacements estimated from intravascular ultrasound radiofrequency (RF) data acquisitions. This study investigated if modulus reconstruction is possible for noninvasive RF acquisitions of vessels in transverse imaging planes using an iterative 2D cross-correlation based displacement estimation algorithm. Furthermore, since it is known that displacements can be improved by compounding of displacements estimated at various beam steering angles, we compared the performance of the modulus reconstruction with and without compounding. For the comparison, simulated and experimental RF data were generated of various vessel-mimicking phantoms. Reconstruction errors were less than 10%, which seems adequate for distinguishing lipid-rich from fibrous tissue. Compounding outperformed single-angle reconstruction: the interquartile range of the reconstructed moduli for the various homogeneous phantom layers was approximately two times smaller. Additionally, the estimated lateral displacements were a factor of 2–3 better matched to the displacements corresponding to the reconstructed modulus distribution. Thus, noninvasive elastic modulus reconstruction is possible for transverse vessel cross sections using this cross-correlation method and is more accurate with compounding. Full article
(This article belongs to the Special Issue Medical & Biological Imaging)
Open AccessArticle Creation of 3D Multi-Body Orthodontic Models by Using Independent Imaging Sensors
Sensors 2013, 13(2), 2033-2050; doi:10.3390/s130202033
Received: 24 December 2012 / Revised: 22 January 2013 / Accepted: 1 February 2013 / Published: 5 February 2013
Cited by 18 | PDF Full-text (1049 KB) | HTML Full-text | XML Full-text
Abstract
In the field of dental health care, plaster models combined with 2D radiographs are widely used in clinical practice for orthodontic diagnoses. However, complex malocclusions can be better analyzed by exploiting 3D digital dental models, which allow virtual simulations and treatment planning [...] Read more.
In the field of dental health care, plaster models combined with 2D radiographs are widely used in clinical practice for orthodontic diagnoses. However, complex malocclusions can be better analyzed by exploiting 3D digital dental models, which allow virtual simulations and treatment planning processes. In this paper, dental data captured by independent imaging sensors are fused to create multi-body orthodontic models composed of teeth, oral soft tissues and alveolar bone structures. The methodology is based on integrating Cone-Beam Computed Tomography (CBCT) and surface structured light scanning. The optical scanner is used to reconstruct tooth crowns and soft tissues (visible surfaces) through the digitalization of both patients’ mouth impressions and plaster casts. These data are also used to guide the segmentation of internal dental tissues by processing CBCT data sets. The 3D individual dental tissues obtained by the optical scanner and the CBCT sensor are fused within multi-body orthodontic models without human supervisions to identify target anatomical structures. The final multi-body models represent valuable virtual platforms to clinical diagnostic and treatment planning. Full article
(This article belongs to the Special Issue Medical & Biological Imaging)
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Open AccessArticle Design of the Dual Stone Locating System on an Extracorporeal Shock Wave Lithotriptor
Sensors 2013, 13(1), 1319-1328; doi:10.3390/s130101319
Received: 13 November 2012 / Revised: 4 January 2013 / Accepted: 17 January 2013 / Published: 21 January 2013
Cited by 2 | PDF Full-text (476 KB) | HTML Full-text | XML Full-text
Abstract
Extracorporeal Shock Wave Lithotriptors are very popular for the treatment of urinary stones all over the world. They depend basically upon either X-ray fluoroscopy or ultrasound scans to detect the stones before therapy begins. To increase the effectiveness of treatment this study [...] Read more.
Extracorporeal Shock Wave Lithotriptors are very popular for the treatment of urinary stones all over the world. They depend basically upon either X-ray fluoroscopy or ultrasound scans to detect the stones before therapy begins. To increase the effectiveness of treatment this study took advantage of both X-ray and ultrasound to develop a dual stone locating system with image processing modules. Its functions include the initial stone locating mode with stone detection by fluorescent images and the follow-up automatic stone tracking mode made by constant ultrasound scanning. The authors have integrated both apparatus and present the operating principles for both modes. The system used two in vitro experiments to justify its abilities of stone location in all procedures. Full article
(This article belongs to the Special Issue Medical & Biological Imaging)
Open AccessArticle Repeatability, Reproducibility and Standardisation of a Laser Doppler Imaging Technique for the Evaluation of Normal Mouse Hindlimb Perfusion
Sensors 2013, 13(1), 500-515; doi:10.3390/s130100500
Received: 3 November 2012 / Revised: 11 December 2012 / Accepted: 20 December 2012 / Published: 28 December 2012
Cited by 3 | PDF Full-text (565 KB) | HTML Full-text | XML Full-text
Abstract
Background. Preclinical perfusion studies are useful for the improvement of diagnosis and therapy in dermatologic, cardiovascular and rheumatic human diseases. The Laser Doppler Perfusion Imaging (LDPI) technique has been used to evaluate superficial alterations of the skin microcirculation in surgically induced [...] Read more.
Background. Preclinical perfusion studies are useful for the improvement of diagnosis and therapy in dermatologic, cardiovascular and rheumatic human diseases. The Laser Doppler Perfusion Imaging (LDPI) technique has been used to evaluate superficial alterations of the skin microcirculation in surgically induced murine hindlimb ischemia. We assessed the reproducibility and the accuracy of LDPI acquisitions and identified several critical factors that could affect LDPI measurements in mice. Methods. Twenty mice were analysed. Statistical standardisation and a repeatability and reproducibility analysis were performed on mouse perfusion signals with respect to differences in body temperature, the presence or absence of hair, the type of anaesthesia used for LDPI measurements and the position of the mouse body. Results. We found excellent correlations among measurements made by the same operator (i.e., repeatability) under the same experimental conditions and by two different operators (i.e., reproducibility). A Bland-Altman analysis showed the absence of bias in repeatability (p = 0.29) or reproducibility (p = 0.89). The limits of agreement for repeatability were –0.357 and –0.033, and for reproducibility, they were –0.270 and 0.238. Significant differences in perfusion values were observed in different experimental groups. Conclusions. Different experimental conditions must be considered as a starting point for the evaluation of new drugs and strategic therapies. Full article
(This article belongs to the Special Issue Medical & Biological Imaging)
Open AccessArticle Detectability of Absorption and Reduced Scattering Coefficients in Frequency-Domain Measurements Using a Realistic Head Phantom
Sensors 2013, 13(1), 152-164; doi:10.3390/s130100152
Received: 7 November 2012 / Revised: 17 December 2012 / Accepted: 18 December 2012 / Published: 24 December 2012
Cited by 3 | PDF Full-text (240 KB) | HTML Full-text | XML Full-text
Abstract
Detection limits of the changes in absorption and reduced scattering coefficients were investigated using a frequency-domain near-infrared system in a realistic head phantom. The results were quantified in terms of the maximum detectable depth for different activation volumes in the range of [...] Read more.
Detection limits of the changes in absorption and reduced scattering coefficients were investigated using a frequency-domain near-infrared system in a realistic head phantom. The results were quantified in terms of the maximum detectable depth for different activation volumes in the range of 0.8–20 microliters. The non-linear relation between the maximum detectable depth and the magnitude of changes in the absorption coefficient conform well with the Born approximation to the diffusion equation. The minimal detectable changes in the reduced scattering coefficient measured in terms of the phase signal were found to be approximately twice as large as that of the absorption coefficient using the AC signal for the same volume and at the same depth. The phase delay, which can be used to quantify the fast neuronal optical response in the human brain, showed a linear dependence on the reciprocal of the reduced scattering coefficient, as predicted by the Rytov approximation. Full article
(This article belongs to the Special Issue Medical & Biological Imaging)
Open AccessArticle A Wireless Accelerometer-Based Body Posture Stability Detection System and Its Application for Meditation Practitioners
Sensors 2012, 12(12), 17620-17632; doi:10.3390/s121217620
Received: 19 October 2012 / Revised: 12 December 2012 / Accepted: 12 December 2012 / Published: 18 December 2012
Cited by 1 | PDF Full-text (373 KB) | HTML Full-text | XML Full-text
Abstract
The practice of meditation has become an interesting research issue in recent decades. Meditation is known to be beneficial for health improvement and illness reduction and many studies on meditation have been made, from both the physiological and psychological points of view. [...] Read more.
The practice of meditation has become an interesting research issue in recent decades. Meditation is known to be beneficial for health improvement and illness reduction and many studies on meditation have been made, from both the physiological and psychological points of view. It is a fundamental requirement of meditation practice to be able to sit without body motion. In this study, a novel body motion monitoring and estimation system has been developed. A wireless tri-axis accelerometer is used to measure body motion. Both a mean and maximum motion index is derived from the square summation of three axes. Two experiments were conducted in this study. The first experiment was to investigate the motion index baseline among three leg-crossing postures. The second experiment was to observe posture dynamics for thirty minute’s meditation. Twenty-six subjects participated in the experiments. In one experiment, thirteen subjects were recruited from an experienced meditation group (meditation experience > 3 years); and the other thirteen subjects were beginners (meditation experience < 1 years). There was a significant posture stability difference between both groups in terms of either mean or maximum parameters (p < 0.05), according to the results of the experiment. Results from another experiment showed that the motion index is different for various postures, such as full-lotus < half-lotus < non-lotus. Full article
(This article belongs to the Special Issue Medical & Biological Imaging)
Open AccessArticle Simultaneous Measurement of Neural Spike Recordings and Multi-Photon Calcium Imaging in Neuroblastoma Cells
Sensors 2012, 12(11), 15281-15291; doi:10.3390/s121115281
Received: 9 August 2012 / Revised: 5 November 2012 / Accepted: 6 November 2012 / Published: 8 November 2012
PDF Full-text (754 KB) | HTML Full-text | XML Full-text
Abstract
This paper proposes the design and implementation of a micro-electrode array (MEA) for neuroblastoma cell culturing. It also explains the implementation of a multi-photon microscope (MPM) customized for neuroblastoma cell excitation and imaging under ambient light. Electrical signal and fluorescence images were [...] Read more.
This paper proposes the design and implementation of a micro-electrode array (MEA) for neuroblastoma cell culturing. It also explains the implementation of a multi-photon microscope (MPM) customized for neuroblastoma cell excitation and imaging under ambient light. Electrical signal and fluorescence images were simultaneously acquired from the neuroblastoma cells on the MEA. MPM calcium images of the cultured neuroblastoma cell on the MEA are presented and also the neural activity was acquired through the MEA recording. A calcium green-1 (CG-1) dextran conjugate of 10,000 D molecular weight was used in this experiment for calcium imaging. This study also evaluated the calcium oscillations and neural spike recording of neuroblastoma cells in an epileptic condition. Based on our observation of neural spikes in neuroblastoma cells with our proposed imaging modality, we report that neuroblastoma cells can be an important model for epileptic activity studies. Full article
(This article belongs to the Special Issue Medical & Biological Imaging)
Open AccessArticle Classification of Fruits Using Computer Vision and a Multiclass Support Vector Machine
Sensors 2012, 12(9), 12489-12505; doi:10.3390/s120912489
Received: 16 July 2012 / Revised: 7 September 2012 / Accepted: 7 September 2012 / Published: 13 September 2012
Cited by 26 | PDF Full-text (712 KB) | HTML Full-text | XML Full-text
Abstract
Automatic classification of fruits via computer vision is still a complicated task due to the various properties of numerous types of fruits. We propose a novel classification method based on a multi-class kernel support vector machine (kSVM) with the desirable goal of [...] Read more.
Automatic classification of fruits via computer vision is still a complicated task due to the various properties of numerous types of fruits. We propose a novel classification method based on a multi-class kernel support vector machine (kSVM) with the desirable goal of accurate and fast classification of fruits. First, fruit images were acquired by a digital camera, and then the background of each image was removed by a split-and-merge algorithm; Second, the color histogram, texture and shape features of each fruit image were extracted to compose a feature space; Third, principal component analysis (PCA) was used to reduce the dimensions of feature space; Finally, three kinds of multi-class SVMs were constructed, i.e., Winner-Takes-All SVM, Max-Wins-Voting SVM, and Directed Acyclic Graph SVM. Meanwhile, three kinds of kernels were chosen, i.e., linear kernel, Homogeneous Polynomial kernel, and Gaussian Radial Basis kernel; finally, the SVMs were trained using 5-fold stratified cross validation with the reduced feature vectors as input. The experimental results demonstrated that the Max-Wins-Voting SVM with Gaussian Radial Basis kernel achieves the best classification accuracy of 88.2%. For computation time, the Directed Acyclic Graph SVMs performs swiftest. Full article
(This article belongs to the Special Issue Medical & Biological Imaging)
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Review

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Open AccessReview Dental Optical Coherence Tomography
Sensors 2013, 13(7), 8928-8949; doi:10.3390/s130708928
Received: 28 May 2013 / Revised: 20 June 2013 / Accepted: 20 June 2013 / Published: 12 July 2013
Cited by 14 | PDF Full-text (1481 KB) | HTML Full-text | XML Full-text
Abstract
This review paper describes the applications of dental optical coherence tomography (OCT) in oral tissue images, caries, periodontal disease and oral cancer. The background of OCT, including basic theory, system setup, light sources, spatial resolution and system limitations, is provided. The comparisons [...] Read more.
This review paper describes the applications of dental optical coherence tomography (OCT) in oral tissue images, caries, periodontal disease and oral cancer. The background of OCT, including basic theory, system setup, light sources, spatial resolution and system limitations, is provided. The comparisons between OCT and other clinical oral diagnostic methods are also discussed. Full article
(This article belongs to the Special Issue Medical & Biological Imaging)
Open AccessReview Optoacoustic Imaging and Tomography: Reconstruction Approaches and Outstanding Challenges in Image Performance and Quantification
Sensors 2013, 13(6), 7345-7384; doi:10.3390/s130607345
Received: 21 March 2013 / Revised: 29 May 2013 / Accepted: 31 May 2013 / Published: 4 June 2013
Cited by 32 | PDF Full-text (1212 KB) | HTML Full-text | XML Full-text
Abstract
This paper comprehensively reviews the emerging topic of optoacoustic imaging from the image reconstruction and quantification perspective. Optoacoustic imaging combines highly attractive features, including rich contrast and high versatility in sensing diverse biological targets, excellent spatial resolution not compromised by light scattering, [...] Read more.
This paper comprehensively reviews the emerging topic of optoacoustic imaging from the image reconstruction and quantification perspective. Optoacoustic imaging combines highly attractive features, including rich contrast and high versatility in sensing diverse biological targets, excellent spatial resolution not compromised by light scattering, and relatively low cost of implementation. Yet, living objects present a complex target for optoacoustic imaging due to the presence of a highly heterogeneous tissue background in the form of strong spatial variations of scattering and absorption. Extracting quantified information on the actual distribution of tissue chromophores and other biomarkers constitutes therefore a challenging problem. Image quantification is further compromised by some frequently-used approximated inversion formulae. In this review, the currently available optoacoustic image reconstruction and quantification approaches are assessed, including back-projection and model-based inversion algorithms, sparse signal representation, wavelet-based approaches, methods for reduction of acoustic artifacts as well as multi-spectral methods for visualization of tissue bio-markers. Applicability of the different methodologies is further analyzed in the context of real-life performance in small animal and clinical in-vivo imaging scenarios. Full article
(This article belongs to the Special Issue Medical & Biological Imaging)
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Open AccessReview In vivo X-Ray Computed Tomographic Imaging of Soft Tissue with Native, Intravenous, or Oral Contrast
Sensors 2013, 13(6), 6957-6980; doi:10.3390/s130606957
Received: 27 March 2013 / Revised: 16 May 2013 / Accepted: 23 May 2013 / Published: 27 May 2013
Cited by 8 | PDF Full-text (701 KB) | HTML Full-text | XML Full-text
Abstract
X-ray Computed Tomography (CT) is one of the most commonly utilized anatomical imaging modalities for both research and clinical purposes. CT combines high-resolution, three-dimensional data with relatively fast acquisition to provide a solid platform for non-invasive human or specimen imaging. The primary [...] Read more.
X-ray Computed Tomography (CT) is one of the most commonly utilized anatomical imaging modalities for both research and clinical purposes. CT combines high-resolution, three-dimensional data with relatively fast acquisition to provide a solid platform for non-invasive human or specimen imaging. The primary limitation of CT is its inability to distinguish many soft tissues based on native contrast. While bone has high contrast within a CT image due to its material density from calcium phosphate, soft tissue is less dense and many are homogenous in density. This presents a challenge in distinguishing one type of soft tissue from another. A couple exceptions include the lungs as well as fat, both of which have unique densities owing to the presence of air or bulk hydrocarbons, respectively. In order to facilitate X-ray CT imaging of other structures, a range of contrast agents have been developed to selectively identify and visualize the anatomical properties of individual tissues. Most agents incorporate atoms like iodine, gold, or barium because of their ability to absorb X-rays, and thus impart contrast to a given organ system. Here we review the strategies available to visualize lung, fat, brain, kidney, liver, spleen, vasculature, gastrointestinal tract, and liver tissues of living mice using either innate contrast, or commercial injectable or ingestible agents with selective perfusion. Further, we demonstrate how each of these approaches will facilitate the non-invasive, longitudinal, in vivo imaging of pre-clinical disease models at each anatomical site. Full article
(This article belongs to the Special Issue Medical & Biological Imaging)
Open AccessReview Advanced Respiratory Motion Compensation for Coronary MR Angiography
Sensors 2013, 13(6), 6882-6899; doi:10.3390/s130606882
Received: 15 April 2013 / Revised: 15 May 2013 / Accepted: 21 May 2013 / Published: 24 May 2013
Cited by 7 | PDF Full-text (573 KB) | HTML Full-text | XML Full-text
Abstract
Despite technical advances, respiratory motion remains a major impediment in a substantial amount of patients undergoing coronary magnetic resonance angiography (CMRA). Traditionally, respiratory motion compensation has been performed with a one-dimensional respiratory navigator positioned on the right hemi-diaphragm, using a motion model [...] Read more.
Despite technical advances, respiratory motion remains a major impediment in a substantial amount of patients undergoing coronary magnetic resonance angiography (CMRA). Traditionally, respiratory motion compensation has been performed with a one-dimensional respiratory navigator positioned on the right hemi-diaphragm, using a motion model to estimate and correct for the bulk respiratory motion of the heart. Recent technical advancements has allowed for direct respiratory motion estimation of the heart, with improved motion compensation performance. Some of these new methods, particularly using image-based navigators or respiratory binning, allow for more advanced motion correction which enables CMRA data acquisition throughout most or all of the respiratory cycle, thereby significantly reducing scan time. This review describes the three components typically involved in most motion compensation strategies for CMRA, including respiratory motion estimation, gating and correction, and how these processes can be utilized to perform advanced respiratory motion compensation. Full article
(This article belongs to the Special Issue Medical & Biological Imaging)
Open AccessReview Quantitative Phase Imaging Techniques for the Study of Cell Pathophysiology: From Principles to Applications
Sensors 2013, 13(4), 4170-4191; doi:10.3390/s130404170
Received: 19 February 2013 / Revised: 11 March 2013 / Accepted: 18 March 2013 / Published: 28 March 2013
Cited by 61 | PDF Full-text (689 KB) | HTML Full-text | XML Full-text
Abstract
A cellular-level study of the pathophysiology is crucial for understanding the mechanisms behind human diseases. Recent advances in quantitative phase imaging (QPI) techniques show promises for the cellular-level understanding of the pathophysiology of diseases. To provide important insight on how the QPI [...] Read more.
A cellular-level study of the pathophysiology is crucial for understanding the mechanisms behind human diseases. Recent advances in quantitative phase imaging (QPI) techniques show promises for the cellular-level understanding of the pathophysiology of diseases. To provide important insight on how the QPI techniques potentially improve the study of cell pathophysiology, here we present the principles of QPI and highlight some of the recent applications of QPI ranging from cell homeostasis to infectious diseases and cancer. Full article
(This article belongs to the Special Issue Medical & Biological Imaging)
Open AccessReview Opening up the Window into “Chemobrain”: A Neuroimaging Review
Sensors 2013, 13(3), 3169-3203; doi:10.3390/s130303169
Received: 1 January 2013 / Revised: 5 February 2013 / Accepted: 16 February 2013 / Published: 6 March 2013
Cited by 13 | PDF Full-text (278 KB) | HTML Full-text | XML Full-text
Abstract
As more chemotherapy-treated cancer patients are reaching survivorship, side-effects such as cognitive impairment warrant research attention. The advent of neuroimaging has helped uncover a neural basis for these deficits. This paper offers a review of neuroimaging investigations in chemotherapy-treated adult cancer patients, [...] Read more.
As more chemotherapy-treated cancer patients are reaching survivorship, side-effects such as cognitive impairment warrant research attention. The advent of neuroimaging has helped uncover a neural basis for these deficits. This paper offers a review of neuroimaging investigations in chemotherapy-treated adult cancer patients, discussing the benefits and limitations of each technique and study design. Additionally, despite the assumption given by the chemobrain label that chemotherapy is the only causative agent of these deficits, other factors will be considered. Suggestions are made on how to more comprehensively study these cognitive changes using imaging techniques, thereby promoting generalizability of the results to clinical applications. Continued investigations may yield better long-term quality of life outcomes by supporting patients’ self-reports, and revealing brain regions being affected by chemotherapy. Full article
(This article belongs to the Special Issue Medical & Biological Imaging)

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