Reconstructing 3D x-ray CT images of polymer gel dosimeters using the zero-scan method

In this study x-ray CT has been used to produce a 3D image of an irradiated PAGAT gel sample, with noise-reduction achieved using the ‘zero-scan’ method. The gel was repeatedly CT scanned and a linear fit to the varying Hounsfield unit of each pixel in the 3D volume was evaluated across the repeated scans, allowing a zero-scan extrapolation of the image to be obtained. To minimise heating of the CT scanner’s x-ray tube, this study used a large slice thickness (1 cm), to provide image slices across the irradiated region of the gel, and a relatively small number of CT scans (63), to extrapolate the zero-scan image. The resulting set of transverse images shows reduced noise compared to images from the initial CT scan of the gel, without being degraded by the additional radiation dose delivered to the gel during the repeated scanning. The full, 3D image of the gel has a low spatial resolution in the longitudinal direction, due to the selected scan parameters. Nonetheless, important features of the dose distribution are apparent in the 3D x-ray CT scan of the gel. The results of this study demonstrate that the zero-scan extrapolation method can be applied to the reconstruction of multiple x-ray CT slices, to provide useful 2D and 3D images of irradiated dosimetry gels

Patient-Specific Pre-Treatment VMAT Plan Verification Using Gamma Passing Rates

Continuous gantry motion, continuous beam modulation, and variable dose rate are used in volumetric modulated arc therapy (VMAT) to obtain highly conformal radiation therapy dose distributions. Several errors during daily radiation therapy treatment can be sources of uncertainties in dose delivery. These errors include monitor unit calculation errors and other human mistakes. Due to the uncertainties in the excessively modulated VMAT plan, the intended dose distribution is not delivered perfectly, leading to a mismatch between the measured and planned dose distributions. This necessitates an extensive and effective quality assurance (QA) program for both machine and patient. In this study, VMAT QA plan verification of 62 head and neck (HN) and 19 prostate cases was done using Octavius 4D setup with its associating VeriSoft gamma analysis software. The plans showed a maximum 3D gamma passing rate with 4 mm/3 % gamma acceptance criteria, i.e., 99.7 % for the HN cancer cases and 99.5 % for the prostate cancer cases. Local gamma analysis was also performed for both regions. Furthermore, 2D and volumetric gamma analyses were also carried out. Gamma analysis with respect to different axis was also carried out. It was known that the transversal axis showed    the highest gamma passing rate in both HN and prostate cases, i.e., 99.17 % and 98.3 %, respectively. The transverse axis came to be a better fit for the planned dose distribution

Uso de la infraestructura docente MIPSfpga v2.0 en la asignatura Arquitectura de Sistemas Integrados

Este paper se basa en un artículo anterior titulado ”Practical experiences based on MIPSfpga”, publicado en el Workshop on Computer Architecture Education (celebrado en la conferencia ISCA-2017). Incluye algunas modificaciones: (1) Hemos ampliado la Sección II-D (que en este paper corresponde a la Sección 2.4) y la Sección III-A (que corresponde a la Sección 3); (2) Hemos eliminado las Secciones III-B y III-C; (3).En este artículo se describe el uso de la infraestructura docente MIPSfpga v2.0 en las prácticas de la asignatura Arquitectura de Sistemas Integrados, una asignatura obligatoria en el Grado en Ingeniería Electrónica de Comunicaciones que se imparte en la Universidad Complutense de Madrid.In this paper we describe the use of the MIPSfpga v2.0 teaching infrastructure for the labs included in the course Integrated Systems Architecture, a compulsory subject in the fourth year of the Electronic Engineering of Communications degree offered at University Complutense of Madrid.Universidad de Granada: Departamento de Arquitectura y Tecnología de Computadores; Vicerrectorado para la Garantía de la Calidad.Los autores agradecen la contribución de Imagination University Program, University of Nevada, Las Vegas, Imperial College London (UK), Grupo ArTeCS de la Universidad Complutense de Madrid y contratos TIN2015-65277-R, TIN2015- 65316-P y Artículo-83 (no 411-2016), Munir Hasan (IMG UK), Prashant Deokar (IMG India), Mahesh Firke (IMG India) Parimal Patel (Xilinx), Kent Brinkley (IMG USA), Rick Leatherman (IMG USA), Chuck Swartley (IMG USA), Sean Raby (IMG UK), Michio Abe (IMG Japan), Bingli Wang (IMG China), Sachin Sundar (IMG USA), Alex Wong (Digilent Inc.), Matthew Fortune (IMG UK), Jeffrey Deans (IMG UK), Laurence Keung (IMG UK), Roy Kravitz (Portland State University), Dennis Pinto (UCM), Tejaswini Angel (Portland State University), Christian White, Gibson Fahnestock, Jason Wong, Cathal McCabe (Xilinx), Larissa Swanland (Digilent)

FORESAIL-1 cubesat mission to measure radiation belt losses and demonstrate de-orbiting

Abstract Today, the near-Earth space is facing a paradigm change as the number of new spacecraft is literally sky-rocketing. Increasing numbers of small satellites threaten the sustainable use of space, as without removal, space debris will eventually make certain critical orbits unusable. A central factor affecting small spacecraft health and leading to debris is the radiation environment, which is unpredictable due to an incomplete understanding of the near-Earth radiation environment itself and its variability driven by the solar wind and outer magnetosphere. This paper presents the FORESAIL-1 nanosatellite mission, having two scientific and one technological objectives. The first scientific objective is to measure the energy and flux of energetic particle loss to the atmosphere with a representative energy and pitch angle resolution over a wide range of magnetic local times. To pave the way to novel model - in situ data comparisons, we also show preliminary results on precipitating electron fluxes obtained with the new global hybrid-Vlasov simulation Vlasiator. The second scientific objective of the FORESAIL-1 mission is to measure energetic neutral atoms (ENAs) of solar origin. The solar ENA flux has the potential to contribute importantly to the knowledge of solar eruption energy budget estimations. The technological objective is to demonstrate a satellite de-orbiting technology, and for the first time, make an orbit manoeuvre with a propellantless nanosatellite. FORESAIL-1 will demonstrate the potential for nanosatellites to make important scientific contributions as well as promote the sustainable utilisation of space by using a cost-efficient de-orbiting technology.Peer reviewe

Assessment of the effects of CT dose in averaged x-ray CT images of a dose-sensitive polymer gel

The signal-to-noise ratio achievable in x-ray computed tomography (CT) images of polymer gels can be increased by averaging over multiple scans of each sample. However, repeated scanning delivers a small additional dose to the gel which may compromise the accuracy of the dose measurement. In this study, a NIPAM-based polymer gel was irradiated and then CT scanned 25 times, with the resulting data used to derive an averaged image and a "zero-scan" image of the gel. Comparison between these two results and the first scan of the gel showed that the averaged and zero-scan images provided better contrast, higher contrast-to- noise and higher signal-to-noise than the initial scan. The pixel values (Hounsfield units, HU) in the averaged image were not noticeably elevated, compared to the zero-scan result and the gradients used in the linear extrapolation of the zero-scan images were small and symmetrically distributed around zero. These results indicate that the averaged image was not artificially lightened by the small, additional dose delivered during CT scanning. This work demonstrates the broader usefulness of the zero-scan method as a means to verify the dosimetric accuracy of gel images derived from averaged x-ray CT data

Analysing emergent users' text messages data and exploring its benefits

While users in the developed world can choose to adopt the technology that suits their needs, the emergent users cannot afford this luxury, and hence, they adapt themselves to the technology that is readily available. When technology is designed, such as the mobile-phone technology, it is an implicit assumption that it would be adopted by the emergent users in due course. However, such user groups have different needs, and they follow different usage patterns as compared to users from the developed world. In this paper, we target an emergent user base, i.e., users from a university in Pakistan, and analyze their texting behavior on mobile phones. We see interesting results, such as the long-term linguistic adaptation of users in the absence of reasonable Urdu keyboards, the overt preference for communicating in Roman Urdu, and the social forces related to textual interaction. We also present two case studies on how a single dataset can effectively help understand emergent users, improve usability of some tasks, and also help users perform previously difficult tasks with ease.Anas Bilal, Aimal Rextin, Ahmad Kakakhel, Mehwish Nasi

Improving the quality of reconstructed X-ray CT images of polymer gel dosimeters: zero-scan coupled with adaptive mean filtering

This study evaluated the feasibility of combining the ‘zero-scan’ (ZS) X-ray computed tomography (CT) based polymer gel dosimeter (PGD) readout with adaptive mean (AM) filtering for improving the signal to noise ratio (SNR), and to compare these results with available average scan (AS) X-ray CT readout techniques. NIPAM PGD were manufactured, irradiated with 6 MV photons, CT imaged and processed in Matlab. AM filter for two iterations, with 3 × 3 and 5 × 5 pixels (kernel size), was used in two scenarios (a) the CT images were subjected to AM filtering (pre-processing) and these were further employed to generate AS and ZS gel images, and (b) the AS and ZS images were first reconstructed from the CT images and then AM filtering was carried out (post-processing). SNR was computed in an ROI of 30 × 30 for different pre and post processing cases. Results showed that the ZS technique combined with AM filtering resulted in improved SNR. Using the previously-recommended 25 images for reconstruction the ZS pre-processed protocol can give an increase of 44% and 80% in SNR for 3 × 3 and 5 × 5 kernel sizes respectively. However, post processing using both techniques and filter sizes introduced blur and a reduction in the spatial resolution. Based on this work, it is possible to recommend that the ZS method may be combined with pre-processed AM filtering using appropriate kernel size, to produce a large increase in the SNR of the reconstructed PGD images

Feasibility study of using Stereotactic Field Diode for field output factors measurement and evaluating three new detectors for small field relative dosimetry of 6 and 10 MV photon beams

This study assesses the feasibility of using stereotactic field diode (SFD) as an alternate to gaf chromic films for field output factor (FF) measurement and further evaluating three new detectors for small field dosimetry. Varian 21EX linear accelerator was used to generate 6 and 10 MV beams of nominal square fields ranging from 0.5 × 0.5 cm2 to 10 × 10 cm2. One passive (EBT3 films) and five active detectors including IBA RAZOR diode(RD), SFD, RAZOR nanochamber (RNC), pinpoint chamber (PTW31023), and semiflex chamber (PTW31010) were employed. FFs were measured using films and SFD while beam profiles and percentage depth dose (PDD) distribution were acquired with active detectors. Polarity (kpol) and recombination (ks) effects of ion chambers were determined and corrected for output ratio measurement. Correction factors (CF) of RD, RNC, and PTW31023 in axial and radial orientation were also measured. Stereotactic field diode measured FFs have shown good agreement with films (with difference of <1%). RD and RNC measured beam profiles were within 3% deviation from the SFD values. Variation in kpol with field size for RNC and PTW31023 was up to 4% and 0.4% (for fields ≥ 1 × 1 cm2), respectively, while variation in ks of PTW31023 was <0.2 %. The maximum values of CF have been calculated to be 5.2%, 2.0%, 13.6%, and 25.5% for RD, RNC, PTW31023‐axial, and PTW31023‐radial respectively. This study concludes that SFD with appropriate CFs as given in TRS 483 may be used for measuring FFs as an alternate to EBT3 films. Whereas RD and RNC may be used for beam profile and PDD measurement in small fields. Considering the limit of usability of 2%, RNC may be used without CF for FF measurement in the smallfields investigated in this study

Improved image quality for x-ray CT imaging of gel dosimeters

Purpose: This study provides a simple method for improving precision of x-ray computed tomography (CT) scans of irradiated polymer gel dosimetry. The noise affecting CT scans of irradiated gels has been an impediment to the use of clinical CT scanners for gel dosimetry studies. Method: In this study, it is shown that multiple scans of a single PAGAT gel dosimeter can be used to extrapolate a ‘zero-scan’ image which displays a similar level of precision to an image obtained by averaging multiple CT images, without the compromised dose measurement resulting from the exposure of the gel to radiation from the CT scanner. Results: When extrapolating the zero-scan image, it is shown that exponential and simple linear fits to the relationship between Hounsfield unit and scan number, for each pixel in the image, provides an accurate indication of gel density. Conclusions: It is expected that this work will be utilised in the analysis of three-dimensional gel volumes irradiated using complex radiotherapy treatments

ELEPHANTIASIS OF THE EXTERNAL GENITALIA: A SEQUEL TO CUTANEOUS TUBERCULOSIS

Tuberculosis continues to be an important public health problem and cutaneous tuberculosis constitutes a minor proportion of extra pulmonary manifestations of tuberculosis. Elephantiasis of the external genitalia, as a sequel to cutaneous tuberculosis, in a 40-year-old diabetic lady is being reported for its rarity. The patient also had lesions of healed scrofuloderma of 27 years’ duration, in both axillae, with residual pedunculated nodules