The objective of this study was to introduce a new iterative method to reconstruct multi leaf collimator (MLC) positions based on low resolution ionization detector array measurements and to evaluate its error detection performance. The iterative reconstruction method consists of a fluence model, a detector model and an optimizer. Expected detector response was calculated using a radiotherapy treatment plan in combination with the fluence model and detector model. MLC leaf positions were reconstructed by minimizing differences between expected and measured detector response. The iterative reconstruction method was evaluated for an Elekta SLi with 10.0 mm MLC leafs in combination with the COMPASS system and the MatriXX Evolution (IBA Dosimetry) detector with a spacing of 7.62 mm. The detector was positioned in such a way that each leaf pair of the MLC was aligned with one row of ionization chambers. Known leaf displacements were introduced in various field geometries ranging from −10.0 mm to 10.0 mm. Error detection performance was tested for MLC leaf position dependency relative to the detector position, gantry angle dependency, monitor unit dependency, and for ten clinical intensity modulated radiotherapy (IMRT) treatment beams. For one clinical head and neck IMRT treatment beam, influence of the iterative reconstruction method on existing 3D dose reconstruction artifacts was evaluated. The described iterative reconstruction method was capable of individual MLC leaf position reconstruction with millimeter accuracy, independent of the relative detector position within the range of clinically applied MU's for IMRT. Dose reconstruction artifacts in a clinical IMRT treatment beam were considerably reduced as compared to the current dose verification procedure. The iterative reconstruction method allows high accuracy 3D dose verification by including actual MLC leaf positions reconstructed from low resolution 2D measurements.
LINK
Introduction: The purpose of this review is to gather and analyse current research publications to evaluate Sinogram-Affirmed Iterative Reconstruction (SAFIRE). The aim of this review is to investigate whether this algorithm is capable of reducing the dose delivered during CT imaging while maintainingimage quality. Recent research shows that children have a greater risk per unit dose due to increased radiosensitivity and longer life expectancies, which means it is particularly important to reduce the radiation dose received by children.Discussion: Recent publications suggest that SAFIRE is capable of reducing image noise in CT images, thereby enabling the potential to reduce dose. Some publications suggest a decrease in dose, by up to 64% compared to filtered back projection, can be accomplished without a change in image quality.However, literature suggests that using a higher SAFIRE strength may alter the image texture, creating an overly ‘smoothed’ image that lacks contrast. Some literature reports SAFIRE gives decreased low contrast detectability as well as spatial resolution. Publications tend to agree that SAFIRE strength threeis optimal for an acceptable level of visual image quality, but more research is required. The importance of creating a balance between dose reduction and image quality is stressed. In this literature review most of the publications were completed using adults or phantoms, and a distinct lack of literature forpaediatric patients is noted.Conclusion: It is necessary to find an optimal way to balance dose reduction and image quality. More research relating to SAFIRE and paediatric patients is required to fully investigate dose reduction potential in this population, for a range of different SAFIRE strengths.
DOCUMENT
Background: Computed tomography (CT) is one of the most used modalities for diagnostics in paediatric populations, which is a concern as it also delivers a high patient dose. Research has focused on developing computer algorithms that provide better image quality at lower dose. The iterative reconstruction algorithm Sinogram-Affirmed Iterative Reconstruction (SAFIRE) was introduced as a new technique that reduces noise to increase image quality.Purpose: The aim of this study is to compare SAFIRE with the current gold standard, Filtered Back Projection (FBP), and assess whether SAFIRE alone permits a reduction in dose while maintaining image quality in paediatric head CT.Methods: Images were collected using a paediatric head phantom using a SIEMENS SOMATOMPERSPECTIVE 128 modulated acquisition. 54 images were reconstructed using FBP and 5 different strengths of SAFIRE. Objective measures of image quality were determined by measuring SNR and CNR. Visual measures of image quality were determined by 17 observers with different radiographic experiences. Images were randomized and displayed using 2AFC; observers scored the images answering 5 questions using a Likert scale.Results: At different dose levels, SAFIRE significantly increased SNR (up to 54%) in the acquired images compared to FBP at 80kVp (5.2-8.4), 110kVp (8.2-12.3), 130kVp (8.8-13.1). Visual image quality was higher with increasing SAFIRE strength. The highest image quality was scored with SAFIRE level 3and higher.Conclusion: The SAFIRE algorithm is suitable for image noise reduction in paediatric head CT. Our data demonstrates that SAFIRE enhances SNR while reducing noise with a possible reduction of dose of 68%.
DOCUMENT
Objective: Summarize all relevant findings in published literature regarding the potential dose reduction related to image quality using Sinogram-Affirmed Iterative Reconstruction (SAFIRE) compared to Filtered Back Projection (FBP).Background: Computed Tomography (CT) is one of the most used radiographic modalities in clinical practice providing high spatial and contrast resolution. However it also delivers a relatively high radiation dose to the patient. Reconstructing raw-data using Iterative Reconstruction (IR) algorithmshas the potential to iteratively reduce image noise while maintaining or improving image quality of low dose standard FBP reconstructions. Nevertheless, long reconstruction times made IR unpractical for clinical use until recently.Siemens Medical developed a new IR algorithm called SAFIRE, which uses up to 5 different strength levels, and poses an alternative to the conventional IR with a significant reconstruction time reduction.Methods: MEDLINE, ScienceDirect and CINAHL databases were used for gathering literature. Eleven articles were included in this review (from 2012 to July 2014).Discussion: This narrative review summarizes the results of eleven articles (using studies on both patients and phantoms) and describes SAFIRE strengths for noise reduction in low dose acquisitions while providing acceptable image quality.Conclusion: Even though the results differ slightly, the literature gathered for this review suggests that the dose in current CT protocols can be reduced at least 50% while maintaining or improving image quality. There is however a lack of literature concerning paediatric population (with increased radiationsensitivity). Further studies should also assess the impact of SAFIRE on diagnostic accuracy.
DOCUMENT
Wat vinden docenten in het beroepsonderwijs in onderwijspedagogische zin de moeite van het onderwijzen waard? Deze vraag staat centraal in de publicatie Onderwijspedagogische visies van mbo-docenten.
MULTIFILE
Deze bundel is een resultaat van de werkgroep ‘Presentie & Onderwijs’. Zij verschijnt ter gelegenheid van het eerste landelijke presentiecongres, op 26 september 2006 in Amersfoort. De werkgroep “Presentie & Onderwijs” is een van de werkgroepen die geïnitieerd is tijdens de eerste bijeenkomst van het presentieforum in het voorjaar van 2004. Zij nam de taak op zich een verkenning te doen naar inbeddingmogelijkheden van de presentiebenadering van Baart (2001) in het onderwijs. Hierbij werd specifiek gekeken naar het HBO-onderwijs, maar er werd ook aandacht besteed aan opleiding in het algemeen, zoals universitair en postinitieel onderwijs, bij- en nascholing en supervisietrajecten. De bundel bestaat uit de volgende bijdragen: • Presentie en Onderwijs: where the twain will meet? (M. Banning e.a.) • Over professionaliteit en presentie. Pleidooi voor normatieve professionaliteit bij HBO-opleidingen (J.P. Wilken) • Presentie en Social Work; Een verkenning van mogelijkheden voor beroepsinnovatie en invoeging in het onderwijs (B. Schriever) • Didactiek van Exposure; Het aanleren van een specifieke manier van kijken (M. Nuy & B. Venneman)
DOCUMENT
Dit onderzoek is een exploratief onderzoek naar welke aspecten van belang zijn bij het interpreteren en begrijpen van hedendaagse informatiebronnen door mensen met beperkte basisvaardigheden.
DOCUMENT
Hoe kunnen vaktherapeuten samen met het kinderwerk en de bijbehorende nieuwe (regionale) zorgnetwerken, nieuwe interventies ontwikkelen en vormgeven met en voor kwetsbare jongeren in hun eigen leefomgeving, zodat enerzijds ontwikkeling van delinquent gedrag bij kwetsbare jongeren voorkomen wordt en anderzijds ketenzorg ontstaat en terugval van jongeren in delinquent gedrag (her)opname in justitiële jeugdinrichtingen en de gesloten jeugdzorg voorkomen wordt. In dit participerend actiegericht onderzoek was er sprake van een intensieve samenwerking tussen professionals en betrokkenen in de praktijk. Hiertoe werd een Community of Practice (CoP) opgericht bestaande uit Jongerenwerkers, Beeldend therapeut, deelnemende kinderen uit een aandachtswijk in Maastricht. De interventies zijn door deze samenwerking ontwikkeld en voortdurend geëvalueerd, waarbij gebruik werd gemaakt van zogenaamde van kwalitatieve en kwantitatieve methoden en instrumenten bij alle betrokken partijen.
DOCUMENT
Een jongerennetwerk is een plek waar jongeren sociale contacten kunnen opdoen en onderlinge steun krijgen. Ook zorgt commissie- en bestuurswerk voor een groei van hun persoonlijke, professionele vaardigheden. Tijdens de eindconferentie deelde lectoraat Diversiteitsvraagstukken inzichten over hoe de deelname van jongeren aan een netwerk of community bij kan dragen aan het realiseren van hun toekomst. Ze leerden hoe deelname aan een jongerennetwerk bijdraagt aan een positief zelfbeeld, een positieve identiteit en het versterken van ambities. Hierdoor krijgen zij de kracht om vol zelfvertrouwen een plek te vinden binnen de onderwijs- of arbeidsomgeving.
MULTIFILE
