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The activity concentration of polonium-210 in the soft tissue of several species of mollusks of coastal areas from Tabasco, Mexico, has been determined. Polonium-210 is a natural radionuclide that may be bioaccumulated by flora and fauna, particularly by mollusks. Radioecological evaluation of polonium-210 in mollusks is of particular interest for environmental radioactivity surveillance and to understand the mechanisms of migration of this radionuclide from the environment to humans. In this work, an analysis of the levels of polonium-210 in mollusks from Mexico is presented. Methods include the use of alpha-particle spectrometry to measure polonium-210 in the soft tissue of the studied mollusks. Results show an average value of 158 Bq/kg in mollusks from Tabasco, Mexico. Mollusks from the taxonomic class Bivalvia bioaccumulate more polonium-210 than Gastropods. The activity concentration values of polonium-210 in mollusks from Mexico are of the same order as those reported internationally. A further work on the mechanisms of migration and bioaccumulation of polonium in these organisms is necessary. [ABSTRACT FROM AUTHOR]

The facial nerve is an array that encompasses motor and sensory fibers. It is one of the most common cranial nerves involved in disorders that considers congenital, traumatic, inflammatory and neoplastic disorders. Facial palsy is a common disease that results from the abnormal state of the facial nerve. In order to understand the full behavior, a quantification method for facial palsy is developed. The method that we propose uses the muscle trajectory information in order to perform a comparison between the right and left side of the face starting from the sagittal plane. To obtain such information, we developed an algorithm that will read a sensor array distributed across the face in order to read the state of the muscle in real time. Moreover, a statistical analysis is performed allowing us to know the state of the facial nerve. Accurate facial palsy measurement are key in the disorder treatment. According to the results found by our system, healthy faces must show a high correlation as well as a large standard deviation, correlation coefficient and a statistical mean. [ABSTRACT FROM AUTHOR]

The implementation in Mexico of the first integrated service in nuclear medicine in the Mexican Peninsula, including Vitalmex's first ABT BG-75 Self-Shielding Cyclotron service in the region, has presented great challenges in all stages of development. The following is a brief but complete summary. The most remarkable challenges, implementing the project are the processes of: project and business planning, construction site planning and licensing, along with the advice of a multidisciplinary professional expert team, this project has achieved the final stage of implementation, and has become fully operational. [ABSTRACT FROM AUTHOR]

Total body irradiation (TBI) is a well-established component of several conditioning regimens required before bone marrow or hematopoietic stem cell transplantation. In this work, we validate the imparted dose in the TBI technique using VMAT in Médica Sur. We used an anthropomorphic phantom ATOM 702-D, CIRS (Norfolk, Virginia), add the upper extremities using a homemade material and scanned it using a CT scanner GE 580RT (General Electric Company). The TBI-VMAT plan was calculated and optimized using Eclipse™ Treatment Planning System V.11.031 (Varian Medical Systems, Palo Alto, CA). We used and adapted the VMAT plan configuration proposed by Springer et al. [1]. The planned doses were compared with the delivered dose in the phantom using Gafchromic EBT3 film (Ashland ISP, Wayne, NJ), placed inside the phantom in planes corresponding to head, lungs, liver, and pelvic region, and irradiated with one single fraction (2 Gy). According to TPS dose-volume histograms, 97.8% of the PTV received 95% of the planned dose (12 Gy in 6 fractions). The mean dose in the plan to the phantom's lungs was 10.03 Gy. These values were consistent with what was measured using EBT3 films and the reported in reference [1], so TBI's clinical implementation using VMAT is feasible in Médica Sur. [ABSTRACT FROM AUTHOR]

One of the biggest challenges in modern radiotherapy such as intensity modulated radiotherapy (IMRT) and volumetric modulated arc radiotherapy (VMAT) is the use of high dose gradients to increase the tumor control and minimize the normal tissue complication probability [1, 2]. The Quality Assurance (QA) of the absorbed dose distribution delivered to each individual patient by the treatment planning system must be performed given the complexity for the dose delivery process by the modern treatment units [3]. For this purpose, high spatial resolution (up to 50 μm) optical computarized tomography (OCT) scanner could be useful, due to the 3D mapping of the absorbance generated in the radicromic gel by ionizing radiation. Before an OCT scanner can be used for clinical application or research purposes, its standard characteristics should be stablished. In this work we investigated the standard charasteristics of a new OCT scanner recentrly installed at Institute of Physics UNAM through the mean absorbance value, the noise, repeatability, and uniformity using a commissioning phantom. The results show the absorbance value is consistent to zero, as expected, and the reconstructions are uniform and reproducible. [ABSTRACT FROM AUTHOR]

Irradiation of blood components is currently one of the accepted methods for preventing Transfusion-Associated Graft-Versus-Host Disease (TA-GVHD) in immunosuppressed patients. The aim of this work was to evaluate the uniformity of the radiation field of a 137Cs irradiator (BIOBEAM GM 2000), through the dose distribution and verify that the irradiator imparts a dose greater than or equal to 25 Gy in the blood components, as part of the quality control of the equipment according to the Mexican norm NOM-253-SSA1-2012. In this study, dosimetry was performed by radiochromic EBT-XD film. It was found that much of the irradiation field does not receive the nominal dose (25 Gy) from the equipment and shows a uniformity (CV<5%) in the central region and tends to decrease in the peripheral areas due to the proximity of the source and the time of irradiation. The dosimetry in the blood components shows an average overdose of 47.2% with respect to the nominal dose. [ABSTRACT FROM AUTHOR]

Introduction: In addition to limited funding, one of the limitations of scientific research in developing countries with a small population, such as Costa Rica, is the lack of human resource with the expertise needed to tackle research challenges. This is particularly the case for emerging fields such as Medical Physics. At the University of Costa Rica (UCR), much of the support to research projects comes from undergraduate students. The main challenge for the principal investigators (PI) is to train these undergraduates to be able to develop not only their assigned tasks, but also their critical thinking skills and knowledge of the field, in order to contribute meaningfully to the research. [1] This work presents the experiences of the Computational Medical Physics Laboratory (FIMEC, Laboratorio de Física Médica Computacional) in training undergraduate students (sophomore and up) for advanced scientific research using innovative educational resources and experiences. All research conducted at FIMEC requires knowledge of graduate level topics and methods in Medical Physics, particularly for the development of Monte Carlo simulations of radiation transport. Methods: Incoming students undergo an induction training including the reading of textbook chapters, scientific articles and theses, with topics in basic concepts on radiation physics, statistics, and anatomy fundamentals. Students undergo a series of tutorials on the computer languages to be used as part of their work (C++, Fortran and others). The training activities are organized in a sequence of increasing difficulty by the PI, to allow the gradual development of skills and knowledge in the students according to their research topic. The students meet regularly with the PI to present their progress and discuss their work. Scientific discussions are aided with the use of educational materials, such as wooden blocks, anatomical models, and board games. These educational materials have been selected to help illustrate and discuss topics related to Monte Carlo modeling. The materials are also used in the design of experiments and the discussion of results. All students are given a laboratory book in which to keep their notes from meetings and their individual work. All exiting students are required to provide documentation on their work, including code manuals, usage guides and a summary of their results. Results and discussion: Since this methodology was implemented at FIMEC in early 2019, 9 undergraduate students have been involved with the laboratory. Three of those students have submitted original work to an international peer-reviewed conference during 2019. Two of those abstracts were derived from work started in 2018 and one of the abstracts was proposed by students who started working at FIMEC in 2019. Two new internal research grants were submitted to UCR for 2020 based on the preliminary work of two other students. In all these works the students involved participated actively in the experiment design, development of software, analysis of results and submission process. In our experience, the use of wooden blocks has resulted to be particularly useful in the discussion of simulation geometries and the analysis of results, as it helps convey ideas both from and to the students in a direct and unequivocal fashion. The remaining students are currently at different stages of their initial training. Conclusions: The implementation of a learning environment where students undergo a series of organized learning activities allows undergraduate students to obtain a minimum of necessary knowledge to become active participants in scientific research. The use of educational materials as aids in the discussion of abstract technical concepts and experimental design facilitates the transference of ideas between the PI and the students and provides a way in which students can convey their own ideas. [ABSTRACT FROM AUTHOR]

We present results of the development of two personal dosimetry devices, called 4-FRD and Koph/Shin, based on thermoluminescent dosimeters. 4-FRD uses TLD-100 and different filters, while Koph/Shin uses a TLD-100/TLD-300 combination. These devices were calibrated for 15-1250 keV photons (4-FRD) and 15-65 keV (Koph/Shin), in terms of air kerma. 4-FRD was able to determine Effective Dose (E) with ∼33% relative expanded uncertainty (k=2), while Koph/Shin determined E with ∼16% relative expanded uncertainty. Both fulfilled ICRP recommendations for personal dosimetry devices in terms of uncertainty. [ABSTRACT FROM AUTHOR]

Sleep in mammals is a dynamic process involving different stages of sleep intensity, which are associated with measurable changes in brain electrical activity. In this animal group two types of sleep have been described: rapid eye movement (REM) sleep and no-REM (NREM) sleep, each one has a specific brain electrical activity and is accompanied by variations in cardiac and respiratory frequencies. Sleep has been demonstrated only in a handful of invertebrates, and evidence for different sleep stages remains elusive. Crayfish sleep fulfills behavioral and electrophysiological criteria defined for mammals. Although no autonomic anatomical structures have been described in this animal, it is known that heart and respiratory frequencies are modified by diverse changes in its environment during wakefulness. Nonetheless, we do not know if this animal has sleep phases and what is the pattern of cardiorespiratory activity during sleep. Here, we studied physiological time series from crayfish based on brain and cardiorespiratory activity recordings in order to search for sleep phases. We used the wavelet transform to analyze brain and cardiorespiratory electrical activity. Our results show that the depth of sleep, measured as the power of electroencephalographic activity, changes over time and is accompanied by oscillations in cardiorespiratory signal amplitude and power. We propose that there are several phases of sleep in crayfish and that this invertebrate is a good biological model in order to achieve a better understanding of sleep. [ABSTRACT FROM AUTHOR]

For the commissioning of a treatment planning system (TPS) is substantial that the parameters of the radiation beam are adequately modeled and verified [1, 2]. In this work, we verified that Eclipse™ TPS V.11.031 reproduced the dose distributions of the Varian Clinac iX n/s 1227, in Médica Sur. For this, we use a PTW MP3 system and different models of dosimetry phantoms, ionization chambers and electrometers. The calculation algorithms to which quality assurance were applied were the Analytical Anisotropic Algorithm (AAA) and electron Monte Carlo (eMC). The basic photon and electron beams dose validation tests described in IAEA and AAPM guidelines [2, 3] were completed for each configured beam. For both algorithms, we have that the comparison between the measured and simulated data in the TPS is within the tolerance range specified in each validation test, being the measurements in the low dose regions and the measurements at larger depths the ones that present the greatest disagreement. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the viability of external beam methods in substitution or replacement of brachytherapy techniques, while maintaining similar dosimetric performance. Methods: Three original tandem and ring brachytherapy plans were re-planned using external beam techniques. A physician recreated the target volumes on CT scans without instruments present, and volumetric photon and intensity modulated proton plans were generated to deliver either a uniform dose or to emulate the brachytherapy distribution with the escalated dose core. Proton plans were additionally generated using several different planning parameters. Resultant plans were compared dosimetrically by evaluating the dose to 2 cm3 for critical organs, the dose coverage to 90% of the target volume, the low-dose normal tissue exposure at 20% and 50% of the prescription, and the target volume receiving 200% and 300% of the prescription for the escalated-dose plans. Results: External beam plans performed well, achieving comparable D90 coverage and critical structure dose to 2 cm3. Higher robustness distance settings increased the D100 for proton plans, along with increases to critical structure doses. Photon plans achieved good escalated dose patterns when emulating the brachytherapy distribution, with better result for the 200% volume than the 300% volume. Photon plans did not meet the 300% coverage in any plans. Escalated proton plans did not meet the brachytherapy dose volumes in any plan, and doses along the entry paths rose to over 150% of the prescription. Conclusion: Brachytherapy is still the preferred method for delivery of the local boost for cervical cancer, despite continued advancement of external beam technologies. Brachytherapy is able to achieve the highest target dose heterogeneity while still protecting organs at risk. External beam photon plans are superior to proton plans when attempting to emulate the brachytherapy dose heterogeneity. [ABSTRACT FROM AUTHOR]

Introduction: Accurate radiation dose measurements at non-target tissues in external beam radiation oncology treatments has become a relevant issue in modern clinical practice. In these cases, low doses out-of-the-treatment-field (OTF) were considered those less than 20% of the prescribed dose beyond 1 cm from field edge defined by jaws. In this work we compare dosimetric response of the optically stimulated luminescence dosimeter OSLD nanoDot versus ionization chamber (IC) and treatment planning system (TPS) Modular Integrated Radiotherapy System (MIRS) v.5.1 and Eclipse (AAA) in cases of water phantom, anthropomorphic phantom CIRS and in vivo tests on points OTF in IMRT with compensator filters. Method: I) in a water tank phantom using 6 MV photon beam (Varian Clinac iX). Exposures were carried out with open field and adding a scatter element (cerrobend compensator filter) at 2.5, 4.5 and 6.5 cm from field edge. II) in anthropomorphic thorax CIRS phantom for an IMRT plan with compensator filters, measurements were made at 4 cm OTF. III) in IMRT plans for 20 intracavitary in vivo dosimetry (IVD) measurements were carried out (on average 9 cm distance OTF). Dosimeters were placed in the oral cavity and rectum. Results: I) In water phantom, OSL response closely followed the IC measured dose: absolute difference of 2.6% in open field and 4.4% with presence of scatter element up to 6.5 cm OTF. Absolute differences showed that both TPS MIRS and Eclipse underestimated doses up to 55.7% and 39.4% respectively in presence of scatter elements up to 6.5 cm from field edge. II) In anthropomorphic phantom, in terms of absolute differences, OSL measured dose followed IC up to 3%. TPS MIRS underestimated doses up to 34.5%. III) intracavitary in vivo dosimetry measurements for OSL and TPS MIRS showed absolute difference dose underestimation up to 42%. Conclusions: Different experiments showed a reliable response of OSL nanoDot versus IC. Both TPS MIRS and Eclipse (AAA) show limitations to determine and to model OTF dose with differences up to 55.7%. Multiple tests has shown OSLD nanoDot with a correct and adequate low dose calibration curve is a viable detector to measure OTF dose since there is no need for correction factors for spectral changes as suggested by Bordy et al. It is important to continue researching dosimetry in anatomical regions at OTF low doses due to probable long-term biological effects. [ABSTRACT FROM AUTHOR]

Radiotherapy represents a significant part of the treatment for glioblastoma multiforme and consists of 30 fractions of 2 Gy for 6 to 7 weeks. However, in preclinical studies, many different irradiation schedules are used. The aim of this work was to evaluate brain radiotoxicity from a fractionated irradiation in rat brain to establish a preclinical model that allows the evaluation of the radiobiological response in a model of glioblastoma in rats irradiated with a 6 MV LINAC. Three groups of Wistar rats were irradiated once a week for 3 weeks achieving a total dose of 10, 15 and 20 Gy, respectively. Brain radiotoxicity was evaluated by weight loss, histological techniques and the 18-FDG uptakes determined by microPET/CT images between pre and post-irradiation groups. The results suggest that no significant differences in the radiotoxicity response between different fractionated doses were observed indicating a favourable result that will be used in the irradiation plan of the tumor model. [ABSTRACT FROM AUTHOR]

The absorbed dose D is the fundamental physical quantity that best correlates the physical, chemical and biological effects induced by ionizing radiation. However, its definition given by ICRU 85a lacks rigor in the following aspects, [1]: a) does not use the modern definition of random variable of the axiomatic theory of Kolmogorov [2, 3], b) neither does it correctly define the concept of stochastic variable [4, 5], c) does not explain the electronic equilibrium condition EE to eliminate the temporal dependence of the imparted energy ε(r, t), considered as a stochastic variable, [5]. [ABSTRACT FROM AUTHOR]

Introduction. Due to the air density correction in the operation of secondary standards with no equivalent air walls, there is a fail of the kPT correction factor in order of 1% to 2.5% in the realization of air kerma rate at the atmospheric conditions of the Mexican highlands (3000 meters above sea level). For this reason, the SSDL-ININ-MEXICO has elected to design and build the Free Air Chamber (FAC), for medium energy X-ray dosimetry. Methods. The air kerma primary standard for X-ray photons is based on parallel-plate FAC for ionometric measurements, which must be operated and designed to fulfill the Charged Particle Equilibrium (CPE) conditions; where the main correction factors is the attenuation factor (katt); therefore, the attenuation length (lat) must be enough to comply with the CPE, where this lat is obtained by Monte Carlo (MC) simulation. Results and discussion. The distribution of the average imparted energy of 300 keV monoenergetic photons as a function of the distance from the reference plane is simulated by the PENELOPE 2008 code, where the plateau corresponds to the CPE region. Therefore, according to the MC simulation, the value of attenuation length lat must be calculated for the point: 44.0 ± 0.5 cm, where the width of the collector electrode is elected 20 cm, within the CPE region of 34 to 54 cm. Conclusions. In this first stage of the design of a FAC, the MC simulation determines that the range to achieve the CPE condition is from 34 to 54 cm, with a collector electrode length of 20 cm and considering an atmospheric pressure P ≈ 710 hPa for a height of 3000 m above sea level. [ABSTRACT FROM AUTHOR]

Breast cancer is one of the leading causes of death in México and among the world. This is mainly due to late diagnosis and the price of cancer treatment. Ultrasound (US) is one of the most used tools for image-based assessment of this disease, since it can help discriminate solid vs. cystic masses, as well as between benign or malignant masses. However, ultrasound imaging depends largely on the radiologists experience. A detection not depending on such experience should produce better diagnosis; therefore, it is necessary to develop automatic detection systems for US images. These systems are based on the image segmentation, which is an image processing technique used to analyze and group pixels by their features. US image segmentation represents important challenges due to the complicated appearance of healthy and tumoral tissue in the ultrasound image that includes speckle pattern, low contrast, blurred boundaries, etc. In this work, we provide a review of tests and comparisons of various segmentation methods that had helped to detect lesions in US images, we present some visual examples to compare this methods and we evaluate their performance in order to develop computer-aided diagnostic systems that help radiologists to do better diagnoses. [ABSTRACT FROM AUTHOR]

PET image quality (IQ) is altered by biological and physical parameters, like the scanner sensitivity, tomographic uniformity, contrast, spatial resolution and reconstruction algorithms. In this work we analyze the differences, advantages and disadvantages between NEMA NU-2 and AAPM TG 126 methods for PET IQ. Measurements were performed on a Siemens mCT Biograph PET-CT System and two phantoms were used: IEC/NEMA Body Phantom (for NEMA measurements) and PET ACR Phantom (for AAPM measurements). 18-Fluorine (18F) was used as the radioactive source (radiopharmaceutical) and all data were reconstructed with UHD: PSF + OSEM + TOF algorithm, iteration number and FWHM were varied. Our results indicates a dependence of contrast with reconstruction parameters. When contrast on a PET image increase, background noise and partial volume effect also increase. Three indicators were measured and graphed, drawing ROIs with an only one performance with NEMA, however, only contrast was measured with AAPM TG 126 protocol and data were compared with the reported limits of this protocol. It indicates that evaluation of IQ on NEMA NU-2 is better than AAPM TG 126, because of the different indicators reported, however AAPM TG 126 analysis is easier to evaluate if system does not have the NEMA quality control acquisition. [ABSTRACT FROM AUTHOR]

A temperature recording and storage system was designed and built, consisting of an array of five thermistor-type sensors, coupled to a synthetic model of biological tissue (MRI phantom) for Ultra-Low Field Magnetic Resonance Imaging System (ULF-MRI), using the Atmega328P microcontroller, like data logging and also used to determine the change in temperature associated with the absorption of energy within the phantom due to the interaction between the radio frequency (RF) field with a sample in different regions within it in MRI studies. The changes in temperature during the MRI study was registered for the entered MRI sequence. All the experiments were carried out in a ULF-MRI system Terranova that uses the Earth's magnetic field to obtain the resonance signal from the magnetization of the protons present in a sample of interest, and thus be able to perform primary imaging and spectroscopy studies [1]. [ABSTRACT FROM AUTHOR]

Introduction: Non-small cell lung cancer (NSCLC) is the most common type of lung cancer, accounting for 85% of all lung cancers. It is characterized by a poor prognosis and a low survival rate (1). Several studies have performed quantitative analysis of different features after a treatment of stereotactic body radiotherapy (SBRT) in lung cancer, using computed tomography studies (2), more specifically, with the cone beam computed tomography (CBCT) technique which is used to assess patient positioning before every treatment session. These studies have suggested that from these features it is possible to study the evolution of the patient's treatment outcome. In this retrospective work we propose several CBCT features evaluated in actual patient lung tumor tissue. Methods: Segmentation of the region of interest was performed to analyze the different features that can be extracted using the free software 3D Slicer 4.10.2. Once the features to be used have been defined, the images obtained by CBCT related to lung tumors of actual patients who underwent lung SBRT were analyzed at the beginning, middle and end of the treatment. Intensity features were of particular interest in this work. Results and discussion: In thorax CBCT images, the tumor volume intensity features that showed a pattern of change, were chosen to assess the tumor tissue response to treatment. The technique was applied to a nine series of images corresponding to actual clinical cases of lung cancer treated with SBRT, through the CBCT images acquired prior to every SBRT session. Energy, mean absolute deviation and total energy are examples of the intensity features that reflect in some degree the influence of the treatment. Conclusions: In this work we propose several CBCT imaging features that reflect in some degree the influence of lung SBRT treatment in tumor tissue. [ABSTRACT FROM AUTHOR]

The conjugate-view counting method used to be the most popular approach to obtain the quantitative information of radiopharmaceuticals. However, the advances in the medical technology and the image processing methods have led to the appearance of new quantification techniques, among which stands out the three-dimensional (3D) quantification of activity in internal tissues of interest. Despite the advantages of this method, its application in nuclear medicine services is usually limited by the workload. In order to exploit the advantages that each quantification method offers, alternative quantitative techniques known as hybrid methods have been developed. This study assessed the quantification of 99mTc-Octreotide through the conjugate-view method (2D) and the hybrid approach (2D/3D) in two patients. The hybrid quantification method improved the dose assessment avoiding the dose overestimation and underestimation in organs and lesions of interest observed in the 2D method. [ABSTRACT FROM AUTHOR]

Introduction: The extraction of features from different medical images can provide information on the changes induced in tumor tissue when patients undergo radiotherapy treatments [1]. One of the imaging modalities in daily use to ensure accurate positioning in lung cancer patients undergoing stereotactic body radiation therapy (SBRT) is cone beam computed tomography (CBCT). In this study we propose a method to extract potentially useful quantitative features from CBCT images in a phantom chest. We also analyze the degree of repeatability and reproducibility that can be achieved in each of the features. Materials and method: After the implementation of a CBCT quality control protocol [2] to the On-Board Imaging System (OBI) of a Novalis Tx (Varian Medical Systems) medical linear accelerator at the American British Cowdray Medical Center in the City of Mexico, CBCT images of a phantom of the thorax were acquired with different inserts made of thermoplastic material. Using open access software, 2D and 3D shape features, features based on a statistic of first order and texture features (features based on a statistic of second order) were extracted. Results and discussion: From the analyzed CBCT images, a total of 107 features were extracted. The methodology was selected according to semi-automatic segmentation procedures to reduce user-dependent results, starting with threshold Hounsfield unit values in a window range for lung tissue. The degree of reproducibility and repeatability of the extracted features and the possible viability of CBCT images for possible radiomics studies in patients with lung cancer and undergoing radiosurgery are analyzed. Conclusions: This work describes a methodology for the extraction of reproducible and repeatable features in CBCT images that can potentially be used to asses lung radiotherapy treatment effect in tumor tissue when the methodology is extrapolated to real images of patients. However, the prognostic value of the reported characteristics should be investigated in further studies. [ABSTRACT FROM AUTHOR]

In this work, we present the development of phantoms made out by anatomical models printed with a 3D printer and adequate them to fit an Ultra-Low Field Magnetic Resonance Imaging System, in order to obtain 2D images. It was used a machine learning algorithm to segment anatomical images from CT and MRI databases from three different organs, and therefore a 3D printer was used to build structures that can fit system's bore and acquire images using basic acquisition sequences to obtain 2D images. The images obtained with the Ultra-Low Field MRI system, show the borders of the phantoms manufactured. This can help us to ensure that the contours from our phantoms can be appreciated with the imaging system, which can lead us to improve system's hardware and imaging processing techniques for academic and research purposes. [ABSTRACT FROM AUTHOR]

Ultrasound is one of the most widely used medical imaging modalities. In Mexico there are official norms that regulate the use of diagnostic ultrasound; however, these guidelines do not specify the type of tests that must be performed to evaluate the optimal and constant performance of ultrasound equipment. Based on protocols from international organizations, a quality control manual was developed to evaluate the following characteristics: mechanical integrity, image uniformity, maximum penetration depth, distance measurement precision, spatial resolution, and dead zone. Subsequently, 4 GE Voluson Ultrasound Systems equipment were evaluated with 12 transducers of different geometries, from a third-level hospital in Mexico City. In total, 11 failures were found during the mechanical inspection, 1 in the uniformity test, 4 in the distance accuracy evaluation, 3 in the spatial resolution test, and 6 in the dead zone test. The results of this work demonstrated that quantitative methods provide information that is related to physical characteristics, which can contribute to reduce subjectivity in the performance of quality control tests of diagnostic ultrasound equipment. Also demonstrates the importance of the routine application of a quality control protocol. [ABSTRACT FROM AUTHOR]

The purpose of the study we report is to extract radiometric information, distributed in three regions of interest (ROI's), from the legs of patients clinically diagnosed with Diabetes Mellitus Type II (DM2) and a control group. We analyze the asymmetry of the thermal radiation emitted from the legs through two approaches: 1) comparing the higher and lower temperatures of the thermal probability distribution of each leg and 2) computing an asymmetry index based on the Spearman's correlation coefficient; that for both groups and two views: anterior (AV) and posterior (PV). The results indicate the existence of radiometric differences between the studied groups. From the former analysis, we get that the sensitivity and specificity over the 1st, 2nd and 3rd ROI at AV are 78% and 86%, respectively. For the posterior view are 89% and 83%, respectively. Instead, by using the Spearman's correlation coefficient, we built up an index related to the thermal asymmetry, whose (sensitivity, specificity) pair for the 1st, 2nd and 3rd ROI, (83%, 67%), (81%, 94%), and (72%, 78%), respectively. [ABSTRACT FROM AUTHOR]

In this work we introduce a standard framework to represent abnormal conditions related to metabolic syndrome (MetS). This framework is based on percentiles represented by reference ellipses constructed from a reference population, and it allows us to observe drifts respect references caused by MetS. [ABSTRACT FROM AUTHOR]

Tumor volume and volumetric reduction have been used as a metric to predict treatment response for patients under chemo-radiation treatments of advanced head and neck cancers. However, cut off values for volumetric changes vary widely among published studies. Imaging biomarkers that stratify patients at risk for treatment failure would be useful to identify patients who are not candidates for dose-deescalation radiotherapy. Radiomics aims to quantitatively capture complex tumor phenotypes from medical images to associate them with clinical outcomes. In this study, we evaluated retrospectively a single shape-type feature, namely, the lymph node gross tumor volume (GTVn) sphericity. The patient data comes from contrast-enhanced CT scans of an ongoing phase II institutional clinical research protocol. The CT scans are acquired at two time intervals (pre-treatment and at week 4 during chemo-radiation treatment) to evaluate radiation dose deescalation based on nodal reduction (ΔGTVn > 40%). Twenty-four patients have been currently enrolled in the study, thirteen of which presented multi-nodal involvement. The sphericity is calculated for two sets of GTVn contoured on CT scans: 1) largest node (based on volume size), and 2) all nodes involved. In the multi-nodal case the sphericity is obtained by averaging the sphericity of individual nodes. The mean pre-treatment sphericity across all patients was 0.746 0.074 for the largest node and 0.656 0.061 for all the nodes (p = 0.002 < 0.05). For both sphericity analyses, the deescalated patients showed higher sphericity range of variations, between the two time intervals compared to the non-deescalated patients (p < 0.05). These results suggest the prognostic value of lymph node tumor sphericity in clinical models, giving special attention to the lymph node GTVn definition as this significantly influences the sphericity values. [ABSTRACT FROM AUTHOR]

Mean Glandular Dose (MGD) is obtained from air kerma measurements, compressed breast characteristics, and beam quality, usually using an ionization chamber (IC). We have developed a system called M3D to evaluate MGD using thermoluminescent dosimetry. The system consists of two PMMA phantoms, one to obtain the radiological techniques for different breast thicknesses and the other to measure air kerma and half-value-layer. In this work, we have redesigned the first phantom to have a variable thickness, and we have evaluated two alternative methods for the use of thermoluminescent dosimeters to measure the required kerma and half-value-layer: use of TLD-100 and Al foils, or a combination of TLD-100/ TLD-300. In the second method, the TLD-300 glow curve shape was analyzed as a vector and was used to determine beam quality. Results showed that the kerma measured by both methods were equivalent to the use of an IC. Typical MGD uncertainties were about 14% and 35% for the two methods, respectively, and these figures rule out the use of the TLD-100/TLD-300 combination for this application. We have concluded that the newly designed M3D system is an option to determine MGD for different breast thicknesses. [ABSTRACT FROM AUTHOR]

In this paper, a modified radio frequency (RF) coil version is presented to be suitable to work at 900 MHz. The proposed coil is based on the Petal Surface Coil and Petal Resonator Surface Coil, whose resonant frequencies were 22 MHz and 64 MHz, respectively. These encouraging results at low field motivated the development of a modified petal resonator surface coil for ultra-high field magnetic resonance imaging applications. Electromagnetic field and return loss simulations guided the development of our coil design. Our prototype consisted of six small circular loops whose diameter was 0.5 cm, connected in series and the total coil diameter was 3 cm. Electromagnetic simulations showed the characteristic patterns of the prototype and provided the theoretical grounds to reliably develop this type of RF coils at 900 MHz. Bench tests measurements showed an important agreement with numerical values. It still remains to actually acquire phantom images to test the viability and compatibility with standard procedures for ultra-high field magnetic resonance imaging applications. This coil design may serve to develop coil arrays with improved performance for high frequencies. [ABSTRACT FROM AUTHOR]

In this work we investigate the effects due to photon attenuation and scattering in a Positron Emission Mammography (PEM) study using the GATE (Geant4 Application for Tomographic Emission) Monte Carlo (MC) code. Breast phantoms with different shapes and volumes placed within a scanner geometry similar to IFUNAM's PEM prototype under development were considered. The results show that attenuation and scatter effects for 511 keV photons depend strongly on the breast phantom volume (and thus, breast thickness). For breast volumes between 200 and 950 ml, scatter contributions vary from 24% to 58%, while the attenuation of primary photons are significant, within 36% and 73%. Our results indicate, overall, that the larger the breast volume, the larger these effects. This implies that for a clinical study to provide precise and quantitative information, complex corrections pre- or post- image reconstruction must necessarily be implemented. [ABSTRACT FROM AUTHOR]

The parallax error introduced by incorrectly assigning the lines-of-response defined by the annihilation photon pairs, limits the attainable spatial resolution in positron emission imaging. Knowledge of the exact position of interaction (x, y, z) inside the scintillation crystal, including the depth of interaction z of the 511 keV photons, reduces this error. In this work, the depth of interaction (DOI) was determined in two different scintillator materials: EJ-232 plastic and LYSO scintillation crystals. These were coupled to an 8×8 silicon photomultiplier (SiPM) array. An analysis of the light distributions produced inside the crystals enabled the determination of the DOI position, allowing the correction for parallax errors. This method is expected to be used in a Positron Emission Mammography (PEM) prototype under development. [ABSTRACT FROM AUTHOR]

Scintillator crystals are widely used as ionizing radiation detectors in nuclear medicine imaging equipment. In many detectors, arrays of small scintillator elements (pixels), optically isolated from each other by a reflective material, are used to provide information on the interaction position of photons in the crystal. The attainable spatial resolution is related to the pixel size. The technique of subsurface laser engraving has been proposed as a low-cost alternative to scintillation crystals arrays to pixelate monolithic crystals. In this work, the first results of the implementation of the laser engraving technique to pixelate cerium doped lutetium yttrium oxyorthosilicate (LYSO:Ce) scintillation crystals in the new Laser Engraving Laboratory at the UNAM Institute of Physics are presented. We characterized the shape and size of the induced microfractures with a Nd:YAG pulsed laser in LYSO crystal, and with this information, we optimized the engraving parameters to produce semi-transparent barriers that optically isolate one pixel from another, thus producing a 6×6 pixelated crystal array with pixel pitch of 1.67 mm. [ABSTRACT FROM AUTHOR]

Introduction: Limited financial resources available for science research and training in Latin America preclude most young scientists from having international experiences. This limitation has an impact on their development as scientists because it restricts the opportunities to interact with cutting-edge researchers and receive mentoring from such professionals. The lack of international forums in which to present their work may limit the expansion of their soft skills in areas such as oral communication, especially regarding giving scientific presentations in the English language. The popularity of online technologies, even in developing countries, allows for new methods in which students can have international experiences without extensive costs. Methods: The International Academic Virtual Exchange network (IAVE) was created as a way to provide students in the developing world access and collaborations with international partners. The student members of this network include graduate students in Medical Physics as well as Physics undergraduates. The network currently has members from 10 different countries in the Americas and Europe. Activities such as weekly journal clubs, scientific conferences, workshops and a peer-reviewed annual congress are organized online using free software that allow for real-time audience interaction via chat or video. Most activities are conducted in English, with occasional activities in Spanish, to allow participation of students at all levels of English command. The annual IAVE Congress accepts abstracts in two modalities, original research and literature review. This allows students with limited access to research opportunities, the chance to hone their literature research, and presentation skills using their available resources. Both modalities undergo the same peer-review process and students present through videoconference to an international audience. Results and discussion: Since 2017, IAVE has hosted over 60 webinars, including weekly sessions, covering subjects from clinical applications of radiation to professional development topics, such as scientific communication. These webinars include presentations of both graduate and undergraduate students in Latin America and the United States. Webinars with professional speakers are organized at each site institution and broadcast to the IAVE network, giving its members the chance to interact with those experts. Two IAVE Congresses have been organized thus far, with participation of 11 students in 2018 and another 11 in 2019, for a total of 18 different students from Latin America (graduate and undergraduate level) and 4 students from the United States (graduate level). The Congresses had online audiences in the Americas and Europe. Mentoring activities and research opportunities are organized at each site institution and across-sites. Conclusions: It is possible to establish a beneficial, fruitful, international relationship between initially unaffiliated institutions with limited resources, through the efforts and commitment of participating members. IAVE has been able to plan and execute several types of activities that increase the opportunities of interaction between members regardless of geographical limitations, providing students the opportunity to participate in international scientific activities, even without physical access to research or travel funding. [ABSTRACT FROM AUTHOR]

The UNAM master's degree program in Medical Physics (MFM) was created more than 20 years ago as part of the UNAM Graduate Program in Physics. In 2019, MFM updated its academic structure, and among the changes, redefined the fields that make up its curriculum according to the current interests of the academic staff and students. The new classification areas are Physics and dosimetry of radiotherapy, Physics and dosimetry of medical diagnostic imaging using X-rays and radionuclides, Physics of the use of non-ionizing radiation in medicine, Physics of the applications of biological physics in medicine, and Scientific instrumentation for medical use. This article analyzes-historically up to now-the projects that constitute the academic offer of these five research areas, the characteristics of the academic tutors, the interest of students to do theses in the area, the types of academic and professional positions occupied by the graduates, and discusses the prospects for the development of medical physics education in Mexico. [ABSTRACT FROM AUTHOR]

Introduction: At the beginning of the 90´s the low number of medical physicists in Mexico was a concern. In 1994, the Instituto Nacional de Investigaciones Nucleares (ININ), sponsored by the International Atomic Energy Agency (IAEA), promoted the creation of a teaching and training program in Medical Physics. In 1996, the Universidad Autónoma del Estado de México (UAEMex) and the ININ started the first formal Graduate Program in Science (Master's and Doctorate degree) specialized in Medical Physics in Mexico. Since 2009 the academic coordination of the program is under UAEMex supervision, but still ININ is its principal collaborator. The objective of this work is to present the professional and academic follow up of 100+ graduates of the UAEMex-ININ program after 24 years of experience. Methods: From the current student files, alumni records and the alumni tracking program, a retrospective analysis was carried out based on: a. Professional and social matters (geographical origin of the students, academic background, ratio of graduated students currently working as medical physicists and related areas, etc.); b. Academic impact (scientific publications and citations produced by the M.Sc. and D.Sc. programs, number of thesis by the study areas of the Medical Physics field, etc.). Results and discussion: The overall terminal efficiency of the program is 69.2%. Although the largest number of students comes from the State of Mexico and Mexico City, students have also been received from 12 other states of Mexico. The incoming students mostly have a Bachelor or Engineering degree majoring in physics. About 81.4% of the graduated work in areas related to medical physics, where 50% of that proportion are clinical medical physicists who are in 17 different states of the country. The areas of Nuclear Medicine and Radiation Therapy are the preferred ones for thesis, and the publications indicate the scientific impact of the program. Conclusions: The indicators presented in this work demonstrate that, in the last 24 years, the UAEMex-ININ M.Sc. and D.Sc. Medical Physics Graduate Program has achieved its goals, in forming clinical medical physicists and researchers. We are currently working to strengthen collaboration with the clinical sector, to impact in the national normativity, to support the establishment of clinical residency, to promote international collaboration and to lead our graduated to obtain recognized certifications in the medical physics areas. [ABSTRACT FROM AUTHOR]

Two-dimensional radiotherapy (2D-RT) is a treatment modality that uses parallel and opposes fields. This work aims to share with new generations of medical physicists the existence of 2D-RT treatments in Mexico today, particularly in the Hospital Central Dr. Ignacio Morones Prieto located in San Luis Potosí. We reviewed the national database of High Technology Medical Equipment, it is of CENETEC-Salud, to get a general overview of teletherapy machines in Mexico, updated in 2016. [ABSTRACT FROM AUTHOR]

The analysis with the Hurst exponent (H) shows the degree of persistence or anti-persistence of the time series, which has allowed quantifying the correlation between the time series data. In this paper, the estimation of the Hurst exponent was based on two methods: the discrete second-order derivative (DSOD) and its Wavelet-based adaptation (WDSOD). The main purpose is to apply the H exponent estimation for the study of complexity in the physiological signals of heartbeat, in order to find information that allows us to evaluate sleep-wake phases in 54 healthy subjects and 44 patients with congestive heart failure (CHF), as well as qualitatively determine cardiac stress and physical condition in stress tests of 30 young subjects, 11 middle-aged adults, both groups with a sedentary lifestyle, and 10 normally active subjects, all without any apparent cardiovascular disease. This method could be considered acceptable to show changes in the dynamics of the cardiovascular system since the results indicate persistence in the RR series of healthy subjects in the sleep and wake phases, in sedentary healthy subjects at rest and in healthy active subjects, otherwise is observed in subjects with CHF in both phases and in sedentary young and adult subjects during physical activity, which showed antipersistence. Therefore, this parameter could be very useful to verify the health state and at least qualitatively determine the stress to which the heart is submitted and the tolerance to exercise during physical activity. [ABSTRACT FROM AUTHOR]

A Faraday cage is an electromagnetic enclosure that is characterized by keeping inside the electric field constant if a nonzero electric charge is applied. On other hand, if the electric charge is zero, the electric field will also be zero. A Faraday cage design is presented for biomedical measurements to operate at 206 MHz with and without electromagnetic absorbents. The design was based on an electromagnetic field mapping to identify the potential sources of electromagnetic interference, their wavelength, effectiveness shielding and therefore, the physical dimensions of the enclosure. Subsequently, a computer simulation using finite element method was executed for the designed enclosure. Once both simulations were performed it was found that without absorbents, the current density was lower than in the simulation with absorbents. On the other hand, the radiation pattern with absorbents was lower in than the simulation without absorbents. [ABSTRACT FROM AUTHOR]

Pathologies in which homeostatic regulatory mechanisms are affected tend to impact multiple systems which are connected through an extensive network. Statistical analysis of time series has been explored as a tool to retrieve information about the underlying regulatory dynamics of these networks, to detect subtle changes that could lead to the development of diseases such as diabetes. This approach has been propelled by the introduction of devices capable of recording physiological variables continuously and non invasively. In this study, experimental time series of regulated and regulating physiological variables and an experimental mechatronic control system (a 2-wheeled self-balancing robot) and a corresponding computer model were analyzed. Results showed that in all examined systems variance of the regulating variable adapts in order to keep the regulated variables as constant as possible. Box-and-whisker charts also conveyed information about other important aspects of the regulation, in the physiological case hysteresis and thus non-linearity and memory became apparent, these properties were absent in the other two systems, which showed a linear behavior. Thus, adaptability of the variance of regulated variables seems to be a characteristic that is not only particular to complex regulatory systems and which would be inherent to all feedback control mechanisms. This study suggests that applications from control theory could be useful to better elucidate the connection between time series and the underlying control mechanisms. [ABSTRACT FROM AUTHOR]

Thermotherapy is a type of treatment increasingly indicated for diseases such as osteoarthritis, hypertonia, muscle contractures, rheumatoid arthritis, skeletal muscle injuries, edema; among others. This increase in the use of thermotherapy treatments has increased the number of thermal agents being used for therapeutic purposes, but in most cases these do not produce the desired effects of thermotherapy. One of these effects is the increase in local oxygenation of the area to which the thermal agent was applied; Therefore, in this experiment, a thermal conduction agent for thermotherapy treatment was applied to an upper extremity so the oxygenation could be measured in a non-invasive way; This treatment was applied to one group of users, while no treatment was applied to another in order to compare the blood oxygen levels of the groups and see if the thermotherapy treatment is really working. The chosen way to measure blood oxygen saturation was with a pulse oximeter and it was expected that increase in the users to whom the treatment was applied, while in the control group there shouldńt be changes in their oximetry levels. Finally, this was verified and therefore it is possible to propose the measurement of oxygen saturation levels in blood to quantify the effectiveness of a thermal agent for thermotherapy. [ABSTRACT FROM AUTHOR]

Introduction: In vivo dosimetry (IVD) is the tool that has been shown to be suitable for verification and improvement on the accuracy of dose delivery and to prevent accidents during radiotherapy treatment. OSLD nanoDot complies with the characteristics to perform intracavitary IVD: being small-sized, they show little or no dependence on variables such as temperature, dose rate, field size, among others. The goal of this work is to define confidence and action levels for intracavitary IVD in intensity modulated radiotherapy (IMRT) at high dose gradient regions (HDGR). Method: OSLD nanoDot were prepared following the TG-191 AAPM international guideline. Commissioning test: OSLD response at HDGR in the penumbra region of an open field with a dedicated acrylic phantom was evaluated and compared with an ionization chamber. Geometrical uncertainties were evaluated as i) dosimeter location at planar digital images, ii) internal anatomical movements, iii) construction and placement of compensator filters and iv) mechanical indicators of the linear accelerator such as gantry, telemeter, laser, among others. Dosimetric impact was evaluated by relative difference considering calculated dose at distant points ±5 mm on anteroposterior direction at HDGR at rectum as organ at risk (OAR) in prostate cancer treatments. In vivo dosimetry test: a small ergonomic silicone device contained two dosimeters and they were placed on 23 patients. Patients gave their consent to participate in this statistical study. Geometrical coordinates of the dosimeters location were acquired by anteroposterior and lateral planar digital images. Coordinates were imported to the treatment planning system Modular Integrated Radiotherapy System (MIRS) v.5.1 (Nuclemed S.A., Argentina) and dose was determined at these points. Results: OSLD response followed with good agreement ionization chamber response over the entire penumbra region and the maximum distance to agreement (DTA) is 1.2 mm. Total geometrical uncertainty was ±5 mm. On the basis of intracavitary IVD, confidence (CL) and action levels (AL) were defined for HDGR. CL was ±19.2% and AL was ±37.1%. Conclusion: Geometrical uncertainty analysis associated to IMRT and intracavitary IVD has excellent correspondence to action level defined. With the correct characterization of the OSLD nanoDot, this detector becomes a good option for its implementation in intracavitary IVD at HDGR. [ABSTRACT FROM AUTHOR]

In this work we developed and validated a Monte Carlo simulation framework of the imaging systems of the Varian TrueBeam STx Linac, and studied the scatter contribution in MV and kV cone-beam CT images. The simulations were validated by comparing measured PDD (Percentage Depth Dose) curves, off-axis profiles and transmission curves with those calculated with the DOSXYZnrc code and a dosimetric model of the detector response using the theoretical energy spectra. The transmission curves were obtained by imaging Al and Cu step-wedge phantoms with the MV system. A parallelized code was used to estimate cone-beam CT projections separating the scatter and primary contributions, optimizing the code using variance reduction techniques (VRTs). The models developed in this work show very good agreement with experimental measurements and with previous results reported in the literature. The use of VRTs allowed quick estimation of the scatter contributions with a speed up factor of 20. This MC framework was used to develop an iterative scatter correction method based on fast simulations of low-resolution voxel models and sparse angular sampling. The iterative scatter correction method showed very good results in both kV and MV cone-beam CT images, improving image quality by reducing the cupping artifact and improving the estimation of the CT numbers. [ABSTRACT FROM AUTHOR]

A three-dimensional electronic detector array consisting of an active matrix readout configuration has been designed. The array comprises 31,560 submillimeter size photodiodes isotropically distributed within a 20 cm diameter semi-spherical volume of water equivalent material. The number of photodiodes in an active matrix varies from 27 to 972, and 80 active matrices with 4200 channels are connected to a data acquisition unit for readout. A low resolution 20 cm diameter semi-spherical electronic detector array was constructed to test the active matrix readout configuration response. The array consists of 135 BPW34S photodiodes distributed in a 12 cm diameter layer and one ionization chamber at the center of the semi-spherical volume. Furthermore, a quality assurance plan for a 6-field 6-MV intracranial treatment was generated to check the array's response. The array was dose calibrated using 20 x 20 cm2 parallel-opposed 6 MV photon beams from a Varian 2100 C/D linear accelerator and the integrated voltage from each photodiode was matched to the calculated dose from a treatment planning software for that photodiode location. Data analysis resulted in a percent dose difference between the measured and calculated dose of ≤5%. [ABSTRACT FROM AUTHOR]

Noise amplification is an important concern in contrast-enhanced (CE) x-ray imaging, in which subtraction techniques are commonly used. In recent years, CE micro-computed tomography (micro-CT) has been used to assess tumor vascularization in animal models of cancer, increasing the necessity to implement noise reduction methods that also allow preserving the detail in the resulting images. This work aimed at designing a bilateral filter (BF) for noise reduction in CE micro-CT for single-energy (SE) and dual-energy (DE) imaging protocols. A classic BF performs smoothing on voxels with similar intensities, while it reduces the contribution of voxels with different intensities, for example, around the edges. In this work, the optimal BF parameters and their performance were evaluated with image quality metrics for the SE and DE protocols: noise (quantified as the standard deviation of the CT number of water), spatial resolution (evaluated with the modulation transfer function), and contrast-to-noise ratio (CNR, evaluated with an iodinated phantom). After the optimal BF parameters were chosen for each imaging protocol, the performance of the designed BF was further evaluated with in vivo SE and DE images of an animal model of breast cancer. Results showed that the designed BF reduced the noise and maintained the spatial resolution in the filtered images compared to the non-filtered images; moreover, the CNR quantified in the images of the iodinated phantom increased both pre- and post- subtraction. The filtered SE and DE images of the animal model of breast cancer showed an adequate level of smoothing, a better definition of tumor boundaries, and the preservation of vascular structures, compared to the non-filtered images. In conclusion, the BF implemented in this work improved the image quality of filtered CE micro-CT images for phantom and in vivo studies, which validates its use in the study of tumor vascularization in animal models of cancer. [ABSTRACT FROM AUTHOR]

This study applied three methods to compensate for intervening tissue attenuation in the estimation of the backscatter coefficient of a tissue-mimicking phantom with spatial variations of attenuation. The first method, considered as the gold standard, made use of attenuation estimates measured using an independent substitution technique. The second method estimated first the local attenuation using a Constrained-Spectral Log Difference (CLD) technique, and then used these values to quantify the total intervening tissue attenuation. The third method consisted on a regularized, dynamic programming technique that simultaneously computes the backscatter coefficient and the total attenuation. Two variants of the latter method were investigated, one with search ranges centered around the expected attenuation and backscatter values of the phantoms, and a second one with search reaches expanded to include attenuation and backscatter values expected in different breast tissues. Our results indicate that, although the CLD method provided more precise estimates of the local attenuation, the DP method with search ranges centered around the expected phantom values provided more accurate attenuation compensation and backscatter coefficient estimation. When increasing the search ranges, the accuracy and precision of DP was importantly reduced. [ABSTRACT FROM AUTHOR]

Young men have high cardio-respiratory variability reflecting the balance between robustness and adaptability to environmental and internal changes that characterize health. However, there are few biomarkers of this variability, thus it is important to determine the ranges for healthy men. Moreover, the health condition of women has considerable correlations with their menstrual cycle. Nevertheless, there is no complete characterization of how this cycle affects the overall physiological state, in particular the cardio-vascular and respiratory variability. To quantify these changes, cardio-respiratory time-series of young subjects are recorded daily during one month to determine the respiratory and heart-rate variability. As an initial proof of concept, four males (control group) and four females performed three maneuvers (clinostatism, rhythmic breathing at 0.1 Hz, and orthostatism) on a 5-minute interval. We also collected data on the circadian rhythm through physical activity and skin temperature. Females' menstrual cycle phase is determined from a clinical interrogation, physiological indicators of the cycle (cervical mucus fluidity and temperature elevation) and hormone determination by blood and urinary samples. Physiological time series of heart rate and breathing dynamics are less variable in women than in men, maybe due to the protective function of hormones, but to have conclusive remarks requires a study on a larger population. [ABSTRACT FROM AUTHOR]

Traditionally, sleep staging is done by medical experts, but computer aid will improve sleeping evaluation. We propose a mathematically-motivated algorithm based on Dense Convolutional Networks that encodes polysomnography (PSG) recordings into a very high-dimensional vector space to perform sleep-stage scoring. We emphasize the flexibility of our model as it provides a framework to analyze single or multi-channel signals without relying on any statistical information about the dataset. To prove the feasibility of our model we show results attaining comparable or better accuracy than current state-of-the-art models at a fraction of the time and very limited training data. [ABSTRACT FROM AUTHOR]

Bone is one of the most affected tissue during radiation therapy treatments. In postmenopausal women, the risk of a hip and femoral head fracture due to osteoporosis induced by ionizing radiation increases from 65% to 216% after receiving radiation treatment for cervical, anal, or rectal cancer. To date, there is no preventive or curative treatment for this damage; this situation promotes to explore preclinical models of radio-osteoporosis. In this work, the pelvic region of adult (male and female) Wistar rats were irradiated with a 6 MV photon beam. Four schemes of two fractions (2 fx) and one scheme of four fractions (4 fx), all with different fractional doses, were evaluated. microCT images were acquired two and four months after irradiations to evaluate changes in the hydroxyapatite concentration [HA] in the hip and femoral head. After imaging, animals were sacrificed, and the femurs were removed to perform histology and scanning electron microscopy studies to evaluate changes in trabecular bone microarchitecture. Low [HA] in the femoral head was observed in male rats (30-weeks-old) after two months post-irradiations. In the hip, a reduction of [HA] was observed after four months. No significant changes were detected in the bone microarchitecture. In female rats, no significant differences (experimental vs. control) in [HA] were observed. This result was associated with the age of rats (12-week-old) at the time of irradiations; it is known that the repair of radiation damage in bone tissue is more efficient in younger rats than in older rats. Visual inspection in the shape of the microarchitecture shows structural differences in the irradiated group; however, quantitative differences in the parameters of the evaluation were not detected. The fractionation schemes of irradiation implemented in this work result in bone damage that could promote radio-osteoporosis. Work is in progress with different image analysis techniques to quantify the damage in the microarchitecture. [ABSTRACT FROM AUTHOR]

3D printing is a method of semi-automated custom fabrication. The advantages of this technology for medical physics is apparent; objects can be constructed for specific clinical needs and constructed with moderate expertise. The cost of 3D printing is cheaper compared to other custom fabrication methods or purchasing from established vendors. Phantoms can be constructed for specific quality control tasks and radiation dosimetry measurements, including patient specific measurements. Beyond phantoms, 3D printing can be used for procedure devices in the form of radiation bolus, immobilization devices, surgical planning models, and rudimentary radiation detectors. Real clinical uses of 3D printing will be presented as well. [ABSTRACT FROM AUTHOR]

Radiomics aims for ways to personalize patient's treatments based on the extraction of texture features from routine clinical images. However, the implementation of Radiomics-based models in routine patient care poses a significant number of challenges, since there are multi-step processes in the implementation of the model. These include image selection (e.g CT, MRI, PET, or a combination of these), region of interest (ROI) segmentation, texture-feature extraction, model development, and model-validation. Each of these processes needs careful evaluation to ensure reproducibility and accuracy of the final Radiomics-based model before it can be introduced into the clinical practice. Image selection, ROI segmentation, and texture feature extraction are the most critical component in Radiomics modeling, because they define the reliability of the model. In this short review, after presenting a brief description of a Radiomics-based model representative workflow, we will concentrate in particular on the status of various technical aspects of imaging modality, segmentation selection, and texture feature extraction, including their shortcomings and possible solutions with emphasis in radiation therapy. [ABSTRACT FROM AUTHOR]

Upright radiotherapy is not new. It has been practiced for specialized treatments such as boron neutron capture therapy, light ion therapy, and even photon therapy before isocentric C-arm gantries became standardized more than 60 years ago. Today, radiotherapy treatment planning relies on CT and/or MRI systems which were typically designed only for recumbent positioning, however, lately CT and MRI scanners that can scan patients in the upright position have been developed. In recent years there is growing evidence that there are some medical benefits for treating some sites with the patient in the upright position. The existing literature describing the medical appropriateness is reviewed. Original work examining the impact to prostate radiotherapy in the upright direction is reported as is the effectiveness of repurposing conventional patient immobilization for upright radiotherapy. The financial benefits for treating with a fixed horizontal beam direction for external beam particle and photon therapy is also examined. So, is upright radiotherapy medically and financially better? The hypothesis is reasonable but it will require regulatory approval and early adopters to confirm the medical and cost effectiveness of the approach. [ABSTRACT FROM AUTHOR]