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  • 1.
    Gårdestig, Magnus
    et al.
    Linköping University, Department of Medicine and Care, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Helmrot, Ebba
    Linköping University, Department of Medicine and Care, Medical Radiology. Linköping University, Faculty of Health Sciences. Jönköping County Hospital.
    Sandborg, Michael
    Linköping University, Department of Medicine and Care, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Nilsson Althén, Jonas
    Linköping University, Department of Medicine and Care, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Bahar Gogani, Jalil
    Linköping University, Department of Medicine and Care, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Alm Carlsson, Gudrun
    Linköping University, Department of Medicine and Care, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Pettersson, Håkan BL
    Linköping University, Department of Medicine and Care, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Estimations of effective dose in X-ray examinations derived from information stored in PACS2005In: Radiological Protection in Transition: Proceedings of the XIV Regular Meeting of the Nordic Society for Radiation Protection, NSFS, Stockholm: Statens Strålskyddsinstitut , 2005, p. 175-178Conference paper (Other academic)
    Abstract [en]

    Information about each X-ray examination, in a modern digitized X-ray department is generated and stored in a PACS. Appropriate conversion factors, e.g. E/DAP, can be applied to separate projections and summed to the total effective dose for each examination. The objectives of the work were (i) to investigate the accuracy and precision in the calculated effective dose (ii) to identify data for registration of (1) patient dose, (2) exposure data, and (3) patient information (iii) to make it possible to derive dose statistics on patient level for documentation of diagnostic standard doses, optimizations, constancy checks, and future epidemiological studies. The effective doses were calculated using Monte Carlo based computer programs or by using tabulations. Conversion factors were calculated for different levels of information and the individual effective dose was compared to the most precise estimation. The results suggest that the accuracy in the estimations of effective dose increases by added information about the patient (gender, size) and how the examination was performed.

  • 2.
    Helmrot, Ebba
    et al.
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Pettersson, Håkan
    Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics. Linköping University, Department of Medicine and Care, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Sandborg, Michael
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Center for Medical Image Science and Visualization (CMIV). Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics. Linköping University, Faculty of Health Sciences.
    Nilsson Althen, Jonas
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Estimation of the dose to the unborn child at diagnostic X-ray examinations based on data registrerad in RIS/PACS2007In: European Radiology, ISSN 0938-7994, E-ISSN 1432-1084, Vol. 17, no 1, p. 205-209Article in journal (Refereed)
    Abstract [en]

    The aim of this work was to determine mean absorbed doses to the unborn child in common conventional X-ray and computed tomography (CT) examinations and to find an approach for estimating foetal dose based on data registered in the Radiological Information System/Picture Archive and Communication System (RIS/PACS). The kerma-area product (KAP) and CT dose index (CTDIvol) in common examinations were registered using a human-shaped female dosimetry phantom. Foetal doses, Df, were measured using thermoluminescent dosimeters placed inside the phantom and compared with calculated values. Measured foetal doses were given in relation to the KAP and the CTDIvol values, respectively. Conversion factor Df/KAP varies between 0.01 and 3.8 mGy/Gycm2, depending on primary beam position, foetus age and beam quality (tube voltage and filtration). Conversion factors Df/CTDIvol are in the range 0.02 – 1.2 mGy/mGy, in which the foetus is outside or within the primary beam. We conclude that dose conversion factors based on KAP or CTDIvol values automatically generated by the RIS/PACS system can be used for rapid estimations of foetal dose for common examination techniques.

  • 3.
    Helmrot, Ebba
    et al.
    Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Thilander Klang, Anne
    Department of Medical Physics and Biomedical Engineering, Sahlgrenska University Hospital, SE-413 45.
    METHODS FOR MONITORING PATIENT DOSEIN DENTAL RADIOLOGY2010In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 139, no 1-3, p. 303-305Article in journal (Refereed)
    Abstract [en]

    Different types of X-ray equipment are used in dental radiology, such as intra-oral, panoramic, cephalometric, cone-beam computed tomography (CBCT) and multi-slice computed tomography (MSCT) units. Digital receptors have replaced film and screen-film systems and other technical developments have been made.

    The radiation doses arising from different types of examination are sparsely documented and often expressed in different radiation quantities. In order to allow the comparison of radiation doses using conventional techniques, i.e. intra-oral, panoramic and cephalometric units, with those obtained using, CBCT or MSCT techniques, the same units of dose must be used. Dose determination should be straightforward and reproducible, and data should be stored for each image and clinical examination.

    It is suggested here that air kerma-area product (PKA) values be used to monitor the radiation doses used in all types of dental examinations including CBCT and MSCT. However, for the CBCT and MSCT techniques, the estimation of dose must be more thoroughly investigated. The values recorded can be used to determine diagnostic standard doses and to set diagnostic reference levels for each type of clinical examination and equipment used. It should also be possible to use these values for the estimation and documentation of organ or effective doses. 

  • 4.
    Lofthag-Hansen, S
    et al.
    Public Dental Health, Göteborg.
    Thilander-Klang, A
    Department of Medical Physics and Biomedical Engineering, Sahlgrenska University Hospital, Göteborg, Sweden.
    Ekestubbe, A
    Department of Oral and Maxillofacial Radiology The Sahlgrenska Academy at Göteborg University, Sweden.
    Helmrot, Ebba
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Gröndahl, K
    Department of Oral and Maxillofacial Radiology, The Sahlgrenska Academy at Göteborg University, Sweden.
    Calculating effective dose on a cone beam computed tomographydevice: 3D Accuitomo and 3D Accuitomo FPD2008In: Dento-Maxillo-Facial Radiology, ISSN 0250-832X, E-ISSN 1476-542X, Vol. 37, no 2, p. 72-79Article in journal (Refereed)
    Abstract [en]

    Objectives: This study evaluates two methods for calculating effective dose, CT dose index (CTDI) and dose–area product (DAP) for a cone beam CT (CBCT) device: 3D Accuitomo at field size 30x40 mm and 3D Accuitomo FPD at field sizes 40x40 mm and 60x60 mm. Furthermore, the effective dose of three commonly used examinations in dental radiology was determined.

    Methods: CTDI100 measurements were performed in a CT head dose phantom with a pencil ionization chamber connected to an electrometer. The rotation centre was placed in the centre of the phantom and also, to simulate a patient examination, in the upper left cuspid region. The DAP value was determined with a plane-parallel transmission ionization chamber connected to an electrometer. A conversion factor of 0.08 mSv per Gy cm2 was used to determine the effective dose from DAP values. Based on data from 90 patient examinations, DAP and effective dose were determined.

    Results: CTDI100 measurements showed an asymmetric dose distribution in the phantom when simulating a patient examination. Hence a correct value of CTDIw could not be calculated. The DAP value increased with higher tube current and tube voltage values. The DAP value was also proportional to the field size. The effective dose was found to be 11–77 microSv for the specific examinations.

    Conclusions: DAP measurement was found to be the best method for determining effective dose for the Accuitomo. Determination of specific conversion factors in dental radiology must, however, be further developed

  • 5.
    Malusek, Alexandr
    et al.
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Helmrot, Ebba
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Alm Carlsson, Gudrun
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Patient-specific kerma-area product as an exposure estimator in computed tomography: the concept and typical values2011In: IAEA, International Symposium on Standards, Applications and Quality Assurance in Medical Radiation Dosimetry (IDOS). 9-12 november 2010, Vienna, Austria. Book of extended synopses. IAEA-CN-182 / [ed] IAEA, International Atomic Energy Agency, Vienna: IAEA , 2011, p. 83-92Conference paper (Refereed)
    Abstract [en]

    Monitoring of exposure levels in computed tomography is important from the radiation safety point of view. In this article, the concept suggested by Huda X[1]X of using the patient-specific kerma-area product as an exposure estimator is extended by providing both a rigorous definition of this quantity and a method for its evaluation. The method was demonstrated on an axial scan of the standard CT dosimetry head phantom taken with a Siemens Somatom Open CT scanner. The resulting patient-specific kerma-area product was 0.25 Gy cm2 for the x-ray tube voltage of 120 kV, tube current of 100 mA, scanning time of 1 s, and beam width at the iso-center of 1.2 cm.  To implement this method, the CT scanner must be equipped with a KAP meter, and the calculation procedure must be added to the scanner's software. Alternatively, the patient-specific kerma-area product can be calculated by the CT scanner without using a KAP meter. In this case, however, the extra safety feature provided by the direct monitoring of the x-ray beam by the KAP meter is lost.

  • 6.
    Malusek, Alexandr
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences.
    Helmrot, Ebba
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Sandborg, Michael
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Grindborg, J-E
    Swedish Radiat Protect Author, Sweden.
    Alm Carlsson, Gudrun
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    In-situ calibration of clinical built-in KAP meters with traceability to a primary standard using a reference KAP meter2014In: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560, Vol. 59, no 23, p. 7195-7210Article in journal (Refereed)
    Abstract [en]

    The air kerma-area product (KAP) is used for settings of diagnostic reference levels. The International Atomic Energy Agency (IAEA) recommends that doses in diagnostic radiology (including the KAP values) be estimated with an accuracy of at least +/- 7% (k = 2). Industry standards defined by the International Electrotechnical Commission (IEC) specify that the uncertainty of KAP meter measurements should be less than +/- 25% (k = 2). Medical physicists willing to comply with the IAEAs recommendation need to apply correction factors to KAP values reported by x-ray units. The aim of this work is to present and evaluate a calibration method for built-in KAP meters on clinical x-ray units. The method is based on (i) a tandem calibration method, which uses a reference KAP meter calibrated to measure the incident radiation, (ii) measurements using an energy-independent ionization chamber to correct for the energy dependence of the reference KAP meter, and (iii) Monte Carlo simulations of the beam quality correction factors that correct for differences between beam qualities at a standard laboratory and the clinic. The method was applied to the KAP meter in a Siemens Aristos FX plus unit. It was found that values reported by the built-in KAP meter differed from the more accurate values measured by the reference KAP meter by more than 25% for high tube voltages (more than 140 kV) and heavily filtered beams (0.3 mm Cu). Associated uncertainties were too high to claim that the IECs limit of 25% was exceeded. Nevertheless the differences were high enough to justify the need for a more accurate calibration of built-in KAP meters.

  • 7.
    Thilander Klang, Anne
    et al.
    Department of Medical Physics and Biomedical Engineering, Sahlgrenska University Hospital, SE-413 45.
    Helmrot, Ebba
    Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics. Linköping University, Department of Medicine and Health Sciences, Radiology . Linköping University, Faculty of Health Sciences.
    METHODS OF DETERMINING THE EFFECTIVE DOSE INDENTAL RADIOLOGY2010In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 139, no 1-3, p. 306-309Article in journal (Refereed)
    Abstract [en]

    A wide variety of X-ray equipment is used today in dental radiology, including intra-oral, orthopantomographic, cephalometric, cone-beam computed tomography (CBCT) and computed tomography (CT). This raises the question of how the radiation risks resulting from different kinds of examinations should be compared. The risk to the patient is usually expressed in terms of the effective dose. However, it is difficult to determine its reliability, and it is difficult to make comparisons, especially when different modalities are used. The classification of the new CBCT units is also problematic as they are sometimes classified as CT units. This will lead to problems in choosing the best dosimetric method, especially when the examination geometry more resembles an ordinary orthopantomographic examination, as the axis of rotation is not at the centre of the patient, and small radiation field sizes are used. The purpose of this study was to present different methods for the estimation of the effective dose from the equipment currently used in dental radiology, and to discuss their limitations. The methods are compared based on common used measurable and computable dose quantities, and their reliability in the estimation of effective dose.

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