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At least 19 recordsLinked to original sources
arXiv2009

Endogenous versus Exogenous Origins of Diseases

Many illnesses are associated with an alteration of the immune system homeostasis due to any combination of factors, including exogenous bacterial insult, endogenous breakdown (e.g., development of a disease that results in immuno suppression), or an exogenous hit like surgery that simultaneously alters immune responsiveness and provides access to bacteria, or genetic disorder. We conjecture that, as a consequence of the co-evolution of the immune system of individuals with the ecology of pathogens, the homeostasis of the immune system requires the influx of pathogens. This allows the immune system to keep the ever present pathogens under control and to react and adjust fast to bursts of infections. We construct the simplest and most general system of rate equations which describes the dynamics of five compartments: healthy cells, altered cells, adaptive and innate immune cells, and pathogens. We study four regimes obtained with or without auto-immune disorder and with or without spontaneous proliferation of infected cells. Over all regimes, we find that seven different states are naturally described by the model: (i) strong healthy immune system, (ii) healthy organism with evanescent immune cells, (iii) chronic infections, (iv) strong infections, (v) cancer, (vi) critically ill state and (vii) death. The analysis of stability conditions demonstrates that these seven states depend on the balance between the robustness of the immune system and the influx of pathogens.

physics.bio-ph↗
arXiv2007

Towards 3D ultrasound image based soft tissue tracking: a transrectal ultrasound prostate image alignment system

The emergence of real-time 3D ultrasound (US) makes it possible to consider image-based tracking of subcutaneous soft tissue targets for computer guided diagnosis and therapy. We propose a 3D transrectal US based tracking system for precise prostate biopsy sample localisation. The aim is to improve sample distribution, to enable targeting of unsampled regions for repeated biopsies, and to make post-interventional quality controls possible. Since the patient is not immobilized, since the prostate is mobile and due to the fact that probe movements are only constrained by the rectum during biopsy acquisition, the tracking system must be able to estimate rigid transformations that are beyond the capture range of common image similarity measures. We propose a fast and robust multi-resolution attribute-vector registration approach that combines global and local optimization methods to solve this problem. Global optimization is performed on a probe movement model that reduces the dimensionality of the search space and thus renders optimization efficient. The method was tested on 237 prostate volumes acquired from 14 different patients for 3D to 3D and 3D to orthogonal 2D slices registration. The 3D-3D version of the algorithm converged correctly in 96.7% of all cases in 6.5s with an accuracy of 1.41mm (r.m.s.) and 3.84mm (max). The 3D to slices method yielded a success rate of 88.9% in 2.3s with an accuracy of 1.37mm (r.m.s.) and 4.3mm (max).

cs.OH↗
arXiv2007

Design, construction and tests of a 3 GHz proton linac booster (LIBO) for cancer therapy

In the last ten years the use of proton beams in radiation therapy has become a clinical tool for treatment of deep-seated tumours. LIBO is a RF compact and low cost proton linear accelerator (SCL type) for hadrontherapy. It is conceived by TERA Foundation as a 3 GHz Linac Booster, to be mounted downstream of an existing cyclotron in order to boost the energy of the proton beam up to 200 MeV, needed for deep treatment (~25 cm) in the human body. With this solution it is possible to transform a low energy commercial cyclotron, normally used for eye melanoma therapy, isotope production and nuclear physics research, into an accelerator for deep-seated tumours. A prototype module of LIBO has been built and successfully tested with full RF power at CERN and with proton beam at INFN Laboratori Nazionali del Sud (LNS) in Catania, within an international collaboration between TERA Foundation, CERN, the Universities and INFN groups of Milan and Naples. The mid-term aim of the project is the technology transfer of the accumulated know-how to a consortium of companies and to bring this novel medical tool to hospitals. The design, construction and tests of the LIBO prototype are described in detail.

physics.acc-ph↗
arXiv2008

Amplified Dispersive Optical Tomography

Optical coherence tomography (OCT) has proven to be a powerful technique for studying tissue morphology in ophthalmology, cardiology, and endomicroscopy. Its performance is limited by the fundamental trade-off between the imaging sensitivity and acquisition speed -- a predicament common in virtually all imaging systems. In this paper, we circumvent this limit by using distributed Raman post-amplification of the reflection from the sample. We combine the amplification with simultaneously performed dispersive Fourier transformation, a process that maps the optical spectrum into an easily measured time-domain waveform. The Raman amplification enables measurement of weak signals which are otherwise buried in noise. It extends the depth range without sacrificing the acquisition speed or causing damage to the sample. As proof of concept, single-shot imaging with 15 dB improvement in sensitivity at an axial scan rate of 36.6 MHz is demonstrated.

physics.optics↗
arXiv2008

Use of a biomechanical tongue model to predict the impact of tongue surgery on speech production

This paper presents predictions of the consequences of tongue surgery on speech production. For this purpose, a 3D finite element model of the tongue is used that represents this articulator as a deformable structure in which tongue muscles anatomy is realistically described. Two examples of tongue surgery, which are common in the treatment of cancers of the oral cavity, are modelled, namely a hemiglossectomy and a large resection of the mouth floor. In both cases, three kinds of possible reconstruction are simulated, assuming flaps with different stiffness. Predictions are computed for the cardinal vowels /i, a, u/ in the absence of any compensatory strategy, i.e. with the same motor commands as the one associated with the production of these vowels in non-pathological conditions. The estimated vocal tract area functions and the corresponding formants are compared to the ones obtained under normal conditions

physics.med-ph↗
arXiv2008

Tongue pressure recordings during speech using complete denture

This paper describes an original experimental procedure to measure mechanical interactions between tongue and teeth during speech production. Using edentulous people as subjects, pressure transducers are inserted in their complete denture duplicate. Physiology is respected during sound and pressure recording as with standard complete denture. Original calibration device is also described in order to know what kind of information can be extracted from the data. The measurements are realized in different experimental conditions in order to remove the auditory and the orosensory feedbacks. Then the first results of the pilot study are presented

physics.med-ph↗
arXiv2008

Measuring Value in Healthcare

A statistical description and model of individual healthcare expenditures in the US has been developed for measuring value in healthcare. We find evidence that healthcare expenditures are quantifiable as an infusion-diffusion process, which can be thought of intuitively as a steady change in the intensity of treatment superimposed on a random process reflecting variations in the efficiency and effectiveness of treatment. The arithmetic mean represents the net average annual cost of healthcare; and when multiplied by the arithmetic standard deviation, which represents the effective risk, the result is a measure of healthcare cost control. Policymakers, providers, payors, or patients that decrease these parameters are generating value in healthcare. The model has an average absolute prediction error of approximately 10-12% across the range of expenditures which spans 6 orders of magnitude over a nearly 10-year period. For the top 1% of the population with the largest expenditures, representing 20%-30% of total spending on healthcare, a power-law relationship emerges. This relationship also applies to the most expensive medical conditions in the US. A fundamental connection between healthcare expenditures and mathematical finance is found by showing that the process healthcare expenditures follow is similar to a widely used model for managing financial assets, leading to the conclusion that a combination of these two fields may yield useful results.

physics.soc-ph↗
arXiv2009

Vega library for processing DICOM data required in Monte Carlo verification of radiotherapy treatment plans

Monte Carlo (MC) methods provide the most accurate to-date dose calculations in heterogeneous media and complex geometries, and this spawns increasing interest in incorporating MC calculations into treatment planning quality assurance process. This involves MC dose calculations for clinically produced treatment plans. To perform these calculations, a number of treatment plan parameters specifying radiation beam and patient geometries need to be transferred to MC codes, such as BEAMnrc and DOSXYZnrc. Extracting these parameters from DICOM files is not a trivial task, one that has previously been performed mostly using Matlab-based software. This paper describes the DICOM tags that contain information required for MC modeling of conformal and IMRT plans, and reports the development of an in-house DICOM interface, through a library (named Vega) of platform-independent, object-oriented C++ codes. The Vega library is small and succinct, offering just the fundamental functions for reading/modifying/writing DICOM files in a C++ program. The library, however, is flexible enough to extract all MC required data from DICOM files, and write MC produced dose distributions into DICOM files that can then be processed in a treatment planning system environment. The library can be made available upon request to the authors.

physics.med-ph↗
arXiv2009

Predicting the Drug Release Kinetics of Matrix Tablets

In this paper we develop two mathematical models to predict the release kinetics of a water soluble drug from a polymer/excipient matrix tablet. The first of our models consists of a random walk on a weighted graph, where the vertices of the graph represent particles of drug, excipient and polymer, respectively. The graph itself is the contact graph of a multidisperse random sphere packing. The second model describes the dissolution and the subsequent diffusion of the active drug out of a porous matrix using a system of partial differential equations. The predictions of both models show good qualitative agreement with experimental release curves. The models will provide tools for designing better controlled release devices.

physics.med-ph↗
arXiv2008

Collimator effects in proton planning

The present paper pertains to corrections which are due to the presence of beam-limiting and beam-shaping devices in proton planning. Two types of corrections are considered: those which are due to the nonzero thickness of such devices (geometrical effects) and those relating to the scattering of beam particles off their material. The application of these two types of corrections is greatly facilitated by decomposing the physical effects (i.e., the contribution to the fluence) of two-dimensional objects (i.e., of the apertures of the devices) into one-dimensional, easily-calculable contributions. To minimise the time requirements in the derivation of the scattering corrections, a two-step process is introduced. The first step occurs at beam-configuration phase and comprises the analysis of half-block fluence measurements and the extraction of the one parameter of the model which is used in the description of the beamline characteristics; subsequently, a number of Monte-Carlo runs lead to the determination of the parameters of a convenient parameterisation of the relevant fluence contributions. The second step involves (at planning time) the reconstruction of the parameters (which are used in the description of the scattering contributions) via simple interpolations, performed on the results obtained during the beam-configuration phase. It is shown that the inclusion of the scattering effects leads to substantial improvement in the reproduction of the experimental data. The contributions from the block-thickness and block-scattering effects have been presented separately in the case of a simple water phantom. In this example, the maximal contribution of the block-relating effects amounts to a few percent of the prescribed dose.

physics.med-ph↗
arXiv2011

Measurement Limits to 134Cs Concentration in Soil

We investigate the caesium concentrations in soils in mountain areas near Gori nuclear power plant in Korea, focusing on the measurement limits to the 134Cs. In order to lower the minimum detectable amount (MDA) of activity for the 134Cs, we have used the ammonium molybdophosphase (AMP) precipitation method to get rid of the 40K existing in natural radioactivity, which reduces the MDA activity about ten times smaller than those without the AMP precipitation method. The MDA results for the 134Cs were found to be in the range between 0.015 and 0.044 Bq/kg-dry weight. In order to diminish the background, we also have measured a part of the soil samples in Yangyang, a small town in the east coast of Korea. However, it turns out that in order to detect the 134Cs in the samples the MDA should be reduced to the level of mBq/kg-dry weight.

physics.med-ph↗
arXiv2014

The effects of using Cesium-137 teletherapy sources as a radiological weapon (dirty bomb)

While radioactive sources used in medical diagnosis do not pose a great security risk due to their low level of radioactivity, therapeutic sources are extremely radioactive and can presumably be used as a radiological weapon. Cobalt-60 and Cesium-137 sources are the most common ones used in radiotherapy with over 10,000 of such sources currently in use worldwide, especially in the developing world, which cannot afford modern accelerators. The present study uses computer simulations to investigate the effects of using Cesium-137 sources from teletherapy devices as a radiological weapon. Assuming a worst-case terrorist attack scenario, we estimate the ensuing cancer mortality, land contamination, evacuation area, as well as the relevant evacuation, decontamination, and health costs in the framework of the linear risk model. The results indicate that an attack with a Cesium-137 dirty bomb in a large metropolitan city (especially one that would involve several teletherapy sources) although would not cause any statistically significant cancer mortality current radiation safety standards would impose the evacuation of large areas and the relocation of thousands of people.

physics.med-ph↗
arXiv2009

Distribution Principle of Bone Tissue

Using the analytic and experimental techniques we present an exploratory study of the mass distribution features of the high coincidence of centre of mass of heterogeneous bone tissue in vivo and its centroid of geometry position. A geometric concept of the average distribution radius of bone issue is proposed and functional relation of this geometric distribution feature between the partition density and its relative tissue average distribution radius is observed. Based upon the mass distribution feature, our results suggest a relative distance assessment index between the center of mass of cortical bone and the bone center of mass and establish a bone strength equation. Analysing the data of human foot in vivo, we notice that the mass and geometric distribution laws have expanded the connotation of Wolff's law, which implies a leap towards the quantitative description of bone strength. We finally conclude that this will not only make a positive contribution to help assess osteoporosis, but will also provide guidance to exercise prescription to the osteoporosis patients.

physics.bio-ph↗
arXiv2009

Comparison of Fluid Attenuated Inversion Recovery Sequence with Spin Echo T2-Weighted MRI for Characterization of Brain Pathology

Twenty cases of different brain pathology have been studied via MRI using an open resistive magnet with magnetic field strength of 0.2 Tesla. The relative signal intensity with respect to the repetition time (TR) at fixed echo time (TE) 0.117 sec. has been studied. It was found that the signal intensity saturates for most lesions beyond a certain TR~6 sec in the T2 - weighted image. The signal intensity differs with respect to the inversion time (TI) for fat and cerebrospinal fluid (CSF). It was found that the intensity is nulled for CSF at TI ~1.5 sec. and for Fat at TI~0.10 sec in the FLAIR imaging sequence. Thus the intensity of the lesions is qualitatively different for the two sequences. From the radiological diagnostic point of view, it was concluded that the FLAIR sequence is more useful for the detection of lesions compared to T2 sequences.

physics.med-ph↗
arXiv2009

Anomalous Light Absorption by Small Particles

A new type of resonant light absorption by a small particle (nanocluster) is reported. The problem cannot be described within the commonly used dipole scattering approximation and should be studied with methods based upon the exact Mie solution. It is shown that the absorption cross-section has giant maxima realized at small values of the imaginary part of the complex dielectric permittivity of the particle. The maxima are situated in the vicinity of the plasmon (polariton) resonances and correspond to the regions where the dissipative damping equals the radiative one. The case is similar to the recently introduced anomalous scattering [PRL vol. 97, 263902 (2006)] and exhibits similar peculiarities.

physics.optics↗
arXiv2010

Measurement of Nuchal Translucency Thickness for Detection of Chromosomal Abnormalities using First Trimester Ultrasound Fetal Images

The Nuchal Translucency thickness measurement is made to identify the Down Syndrome in screening first trimester fetus and presented in this paper. The mean shift analysis and canny operators are utilized for segmenting the nuchal translucency region and the exact thickness has been estimated using Blob analysis. It is observed from the results that the fetus in the 14th week of Gestation is expected to have a nuchal translucency thickness of 1.87 plus or minus 0.25mm.

cs.OH↗
arXiv2010

Modulation of Autonomous Nervous System activity by gyrosonic stimulation

A novel audio binaural stimulus that generates rotational perceptions of sound movement in brain at a particular predetermined frequency is referred as gyrosonics. The influence of gyrosonics on autonomic nervous system of healthy subjects has been examined by analyzing heart rate variability (HRV) in time- and frequency- domain. The M-lagged Poincare plot shows that the parameters SD1, SD2 and ratio SD12 (SD1/SD2) increases with lagged number M, and M-dependence is well described by Pade' approximant $χ\frac{1+βM}{1+γM}$ where values of $χ$, $β$ and $ γ$ depend on parameters SD1,SD2 and SD12. The values of these parameters for different M are augmented after gyrosonic stimulation. The slope and magnitude of curvature of SD1 and SD12 vs M plot increase considerably due to stimulation. The DFA analysis exhibits decrease in value of exponent $α$ due to stimulation. This stimulation results slower Heart rate, higher values of the standard deviation SD and the root-mean squared successive differences (RMSSD) in RR-interval. The spectral power of both low (LF) - and high (HF) - frequency go up due to the stimulation. The results suggest an improvement of the sympatho-vagal balance due to this novel audio stimulus.

physics.med-ph↗