| 1. |
- Andersson, Martin, et al.
(författare)
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IDAC-CAD2VOX : A software for radiation protection calculations for the ICRP reference phantoms which are in an environment described by detailed cad drawings
- 2017
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Ingår i: Medical Physics in the Baltic States : Proceedings of the 13th International Conference on Medical Physics. ; , s. 10-13
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Konferensbidrag (refereegranskat)abstract
- A computer program called IDAC-CAD2VOX has been constructed to create geometry input files from CAD drawings for the Monte Carlo simulation program MCNP. The ICRP reference phantoms are incorporated into the CAD drawings to estimate organ doses and the effective dose. The program is applied to a CAD drawing of a house and a 2D drawing of a radiation protection bunker. The created MCNP geometry was visualised by an external program Visual Editor. Dose calculations were performed for a CAD -drawing of a house, where a point source of 1 GBq 99mTc was placed in the attic. The effective dose to the adult male ICRP reference phantom was estimated to be 7.0 µSv when placed in the living room on the second floor. In summary, a method has been developed to enable effective dose estimations to adults directly from CAD files and to present the results in a pedagogic and easily understandable way.
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| 2. |
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| 3. |
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| 4. |
- Hemdal, Bengt, et al.
(författare)
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Average glandular dose in routine mammography screening using a Sectra MicroDose Mammography unit.
- 2005
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Ingår i: Radiation Protection Dosimetry. - : Oxford University Press (OUP). - 1742-3406 .- 0144-8420. ; 114:1-3, s. 436-443
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Tidskriftsartikel (refereegranskat)abstract
- The Sectra MicroDose Mammography system is based on direct photon counting (with a solid-state detector), and a substantially lower dose to the breast than when using conventional systems can be expected. In this work absorbed dose measurements have been performed for the first unit used in routine mammography screening (at the Hospital of Helsingborg, Sweden). Two European protocols on dosimetry in mammography have been followed. Measurement of half value layer (HVL) cannot be performed as prescribed, but this study has demonstrated that non-invasive measurements of HVL can be performed accurately with a sensitive and well collimated solid-state detector with simultaneous correction for the energy dependence. The average glandular dose for a 50 mm standard breast with 50% glandularity, simulated by 45 mm polymethylmethacrylate, was found to be 0.21 and 0.28 mGy in March and December 2004, respectively. These values are much lower than for any other mammography system on the market today. It has to be stressed that the measurements were made using the current clinical settings and that no systematic optimisation of the relationship between absorbed dose and diagnostic image quality has been performed within the present study. In order to further increase the accuracy of absorbed dose measurements for this unit, the existing dose protocols should be revised to account also for the tungsten/aluminium anode/filter combination, the multi-slit pre-collimator device and the occurrence of a dose profile in the scanning direction
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| 6. |
- Herrnsdorf, Lars, et al.
(författare)
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A method to characterize the radiation output from a cone beam O-arm using a device for dose and dose profile scanning measurement
- 2013
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Ingår i: Medical Imaging 2013: Physics of Medical Imaging. - : SPIE. - 0277-786X .- 1996-756X. - 9780819494429 ; 8668, s. 86682-86682
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Konferensbidrag (refereegranskat)abstract
- The O-arm system is a mobile intraoperative imaging system that is comprised of fluoroscopy and cone beam CT. The configuration of the O-arm system with absence of patient table and a broad beam width (165 mm in isocenter) brings new practical and physical requirements on how to perform dose measurements. The purpose of this study was to describe a method that overcomes this and makes it possible to characterize the radiation output from the O-arm system. A holder with a clamp and a flexible ball joint that can orientate the radiation detector support and the Mover that can be adjusted to hold the dose detector in a horizontal position was used. Evaluation of the dose response for three different dose detectors of different active length (0.3, 23.1 and 100 mm) was made for three different beam qualities. Furthermore the dose profile free in air to control the possible heel effect and width of the x-ray field during rotation was measured and the dose rate waveform was analyzed. The FWHM of the dose profile was 162 mm The dose response of the three detectors is reported. The average dose response was lower for the detector with longer active length due to the influence of the dose profile shape. From dynamic measurement total exposure time, pulse width, and the number of pulses were verified. In conclusion, an external horizontal hanging holder with mover option helps to assist to make dose measurement easier and enables characterize the radiation output from the O-arm system.
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| 7. |
- Herrnsdorf, Lars, et al.
(författare)
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Construction and evaluation of a real-time personal dosemeter based on a Si sensor for eye-dose measurement
- 2019
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Ingår i: Applied Radiation and Isotopes. - : Elsevier BV. - 0969-8043. ; 147, s. 171-176
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Tidskriftsartikel (refereegranskat)abstract
- The objective was to design a thin, flex card based personal dosemeter with low angular and energy dependence. It is based on silicon diodes that can measure the personal dose equivalent. Anisotropic conducting adhesive was used to connect the Si sensor to the flex card. Its intended use is for interventional radiology and after nuclear or radiological accidents, as it provides immediate detailed information about the dose rate to the wearer during shorter periods and integrates the dose rate during hours. It can be freely placed all over the body. By placing the dosemeter close to the eyes, it may be possible to estimate the personal dose equivalent as well as the dose at the lens of the eye.
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| 8. |
- Herrnsdorf, Lars
(författare)
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Development and characterization of sensitive, energy-independent solid-state photon dosemeters with high spatial and temporal resolution. Applications in clinical radiology and radiation protection.
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- AbstractModern medicine and health care rely on a variety of diagnostic and therapeutic equipment and methods that involve ionizing radiation. To guarantee quality and the safety of patients and staff, advanced radiation detectors and dosemeters are needed that have low energy and operate with directional independence for X-ray and γ-ray photons. Similar instruments are also of great importance for measurements used in radiation protection and safety outside of hospitals and the health care sector and for nuclear and radiological emergencies. In this thesis, new sensors, detectors, and dosemeters based on silicon were designed, manufactured, characterized, and tested. The aim was to develop dosemeters with signals that are as independent as possible of the energy and direction of the incoming X-ray and γ-ray photons. Starting with a 350 µm silicon wafer, a sensor was constructed with electrical contacts on one side only. A flex card was adapted with anisotropic conductive adhesive (ACA) and mounted to the sensor. Since all components have low X-ray attenuation, the disturbance of the radiation field by the detector is minimal from all directions. Another important component is the metal filter encapsulating the silicon detector. Made of stainless steel, this encompassing filter compensates for the energy and directional variation of sensitivity of the silicon detector. The filter was designed using a series of Monte Carlo calculations. The hole pattern was selected so that the signal (proportional to the absorbed dose) was independent of the X-ray source position (in 4π). Due to the small structures, additive manufacturing (AM) in the form of metal 3D printing was needed to fabricate the filter. The functionality of the 4π dosemeter was verified by simulation to meet the quality criterion that the energy dependence is less than 5% for the IEC beam qualities RQR and RQT in the range 65–145 kV. The best way to microfabricate the sensor, sensor holder, flex card, and energy filter was evaluated and a method to control its mounting accuracy is proposed. The application of silicon detectors in radiology (CT, CBCT, and planar radiography) was tested, and a specific dosemeter construction also was tested for eye lens dosimetry and for emergency situations. To broaden the use of silicon detectors in future medical imaging and dosimetry applications, an overview of silicon photomultipliers (SiPM) for this area is included and a learning and training program targeted to graduate students is described.
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| 9. |
- Herrnsdorf, Lars
(författare)
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Review of Methods to Control Patient Doses and Image Quality in Various CT Techniques
- 2012
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Ingår i: Medical Physics in the Baltic States. - 1822-5721. ; , s. 97-98
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Konferensbidrag (refereegranskat)abstract
- Medical X-ray imaging is the largest source of radiation exposure to the population from artificial sources. Computed tomography (CT) contributes with 50-80 % of that radiation. About 660 000 CT examinations (2005) are done in Sweden every year. A CT examination gives a mean effective dose of 5 mSv, which is about 10 times higher than for a corresponding conventional X-ray investigation. This presentation describes earlier, current and future dosimetric and image quality analysis methods, necessary to correspond to the rapidly developing CT-techniques.
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