Article
Monte Carlo techniques in medical radiation physics.
Department of Radiation Physics, Karolinska Institute, Stockholm, Sweden.
Physics in Medicine and Biology (Impact Factor: 2.7). 08/1991; 36(7):861920. DOI: 10.1088/00319155/36/7/001 Source: PubMed

Thesis: A Monte Carlo study of the accuracy of CTnumbers for range calculations in carbon ion therapy
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ABSTRACT: Kohlenstoffionen deponieren den größten Teil ihrer Energie in einer schmalen Region nahe der maximalen Reichweite (Bragg Peak). Die Reichweite der Ionen in Gewebe ist abhängig von der Elektronendichte des Gewebes. Diese Elektronendichte kann gegenwärtig nur mit Hilfe eines RöntgenComputertomographen (CT) mit ausreichend räumlicher Auflösung gemessen werden. Daher ist es notwendig, möglichst exakte CTDaten zu erhalten. Diese CTDaten sind allerdings abhängig von den Parametern die während der Datenerfassung verwendet werden. In dieser Arbeit wird der Einfluss dieser Messparameter auf die CTDaten mit Hilfe von MonteCarlo Simulationen einzelner CTProjektionen und der Rekonstruktion dieser Projektionen systematisch studiert. Abweichungen der CTDaten aufgrund des Phantomdurchmessers sowie der Zusammensetzung des Substitutmaterials, dem verwendeten Phantommaterial und der gewählten Spannung der CTRöntgenröhre werden untersucht. Desweiteren wird die Übertragung von Unsicherheiten in den CTDaten in eine herapeutisch relevantere Reichweiten und Dosisunsicherheit bei der Anwendung von Kohlenstoffstrahlen diskutiert. Carbon ions deposit most of their energy in a narrow region near the end of their range (Bragg peak). The range of ions in tissue depends on the electron density of the tissue, which can only be measured with reasonable spatial resolution using Xray computed tomography (CT).Therefore, it is important to have accurate CTdata. However, the value of CTnumbers depends on the parameters used during the acquisition of CTnumbers. In this work, the effect of measuring conditions on CTnumbers is systematically studied by performing Monte Carlo simulations of a CT scanner and reconstructing the simulated projections. Deviations of CTnumbers due to the material of the substitutes, the material of the phantom which is used for CT measurements, the diameter of the phantom and the voltage settings of the Xray tube are investigated. The translation of the deviations in CTnumbers into range and dose uncertainties of Carbon ions is also discussed.07/2014  [Show abstract] [Hide abstract]
ABSTRACT: Knowledge of organ and effective doses achieved during paediatric xray examinations is an important prerequisite for assessment of radiation burden to the patient. Conversion coefficients for reconstruction of organ and effective doses from entrance doses for segmental spine radiographs of 0, 1, 5, 10, 15 and 30yearold patients are provided regarding the Guidelines of Good Radiographic Technique of the European Commission. Using the personal computer program PCXMC developed by the Finnish Centre for Radiation and Nuclear Safety (Säteilyturvakeskus STUK), conversion coefficients for conventional segmental spine radiographs were calculated performing Monte Carlo simulations in mathematical hermaphrodite phantom models describing patients of different ages. The clinical variation of beam collimation was taken into consideration by defining optimal and suboptimal radiation field settings. Conversion coefficients for the reconstruction of organ doses in about 40 organs and tissues from measured entrance doses during cervical, thoracic and lumbar spine radiographs of 0, 1, 5, 10, 15 and 30yearold patients were calculated for the standard sagittal and lateral beam projections and the standard focus detector distance of 115 cm. The conversion coefficients presented may be used for organ dose assessments from entrance doses measured during spine radiographs of patients of all age groups and all field settings within the optimal and suboptimal standard field settings.Pediatric Radiology 02/2014; · 1.57 Impact Factor 
Article: Patient Radiation Exposure in a Modern, LargeVolume, Pediatric Cardiac Catheterization Laboratory.
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ABSTRACT: Radiation exposure from pediatric cardiac catheterization may be substantial, although published estimates vary. We sought to report patient radiation dose across a range of diagnostic and interventional cases in a modern, highvolume pediatric catheterization laboratory. We retrospectively reviewed diagnostic and interventional cases performed in our pediatric catheterization laboratory from 1 April 2009 to 30 September 2011 for which radiation usage data were available as reported by the Artis Zee(®) (Siemens Medical Solutions) system. Electrophysiology cases were excluded. Radiation dose was quantified as air kerma dose (mGy) and dosearea product (DAP; μGy m(2)). The DAP was converted to an effective dose millisievert (mSv) using the Monte Carlo method. Radiation usage data were available from 2,265 diagnostic and interventional cases with an overall median air kerma dose of 135 mGy [interquartile range (IQR) 59433], median DAP of 760 μGy m(2) (IQR 2812,810), of which 75 % (IQR 5990 %) was derived from fluoroscopy, and median effective dose of 6.2 mSv (IQR 2.714.1). Air kerma dose from a single camera >2,000 mGy occurred in 1.8 % of cases. Significant differences in all measures of radiation exposure existed based on procedural and interventional types (p = 0.0001), with interventional cases associated with the highest effective dose after adjusting for patient weight category (p < 0.001). Patient weight, age, fluoroscopy time, and proportional use of digital acquisition were independent predictors of exposure (p ≤ 0.001; R (2) = 0.590.64). In a modern, largevolume pediatric catheterization laboratory, the median effective dose is 6.2 mSv with a wide range of exposure based on patient and procedurespecific factors. Radiation monitoring is an important component of a pediatric laboratory and further dose reduction strategies are warranted.Pediatric Cardiology 01/2014; · 1.20 Impact Factor
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