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Träfflista för sökning "WFRF:(Nilsson Mats) ;pers:(Hellén Halme Kristina)"

Sökning: WFRF:(Nilsson Mats) > Hellén Halme Kristina

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1.
  • Hellén-Halme, Kristina, et al. (författare)
  • The Effects on Absorbed Dose Distribution in Intraoral X-ray Imaging When Using Tube Voltages of 60 and 70 kV for Bitewing Imaging.
  • 2013
  • Ingår i: eJournal of Oral and Maxillofacial Research. - : Stilus Optimus. - 2029-283X. ; 4:3, s. 2-2
  • Tidskriftsartikel (refereegranskat)abstract
    • Efforts are made in radiographic examinations to obtain the best image quality with the lowest possible absorbed dose to the patient. In dental radiography, the absorbed dose to patients is very low, but exposures are relatively frequent. It has been suggested that frequent low-dose exposures can pose a risk for development of future cancer. It has previously been reported that there was no significant difference in the diagnostic accuracy of approximal carious lesions in radiographs obtained using tube voltages of 60 and 70 kV. The aim of this study was, therefore, to evaluate the patient dose resulting from exposures at these tube voltages to obtain intraoral bitewing radiographs.
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2.
  • Cederhag, Josefine, et al. (författare)
  • Comparison of absorbed doses and organ doses measured with thermoluminescent dosimeters and Gafchromic film for cone beam computed tomography examination of the posterior mandibular region in a head phantom
  • 2023
  • Ingår i: Oral Surgery, Oral Medicine, Oral Pathology and Oral Radiology. - : Elsevier. - 2212-4403 .- 2212-4411. ; 136:6, s. 769-776
  • Tidskriftsartikel (refereegranskat)abstract
    • Objectives: We aimed to map the correlation between thermoluminescent dosimeters (TLDs) and Gafchromic film for measuring absorbed doses and to compare minimum, maximum, and mean absorbed doses over larger regions of interest and at various craniofacial organs and tissues during cone beam computed tomography (CBCT) exposure of the mandibular third molar region. Study Design: We positioned TLDs at 75 measurement points in a head phantom. Gafchromic film was cut to the same shape as the 5 levels of the phantom and was placed on top of the TLDs. Both dosimetry methods thus included the surface of each level simultaneously. CBCT scans were made using a 5 × 5 cm field of view and a rotation angle of 200°. Measurements included absorbed dose distributions, doses at all 75 points, and minimum, maximum, and mean doses within organs and tissues. Results: The correlation of point-dose measurements at all TLD sites with doses measured on film was strong (R2 = 0.9687), with greatest correlation at lower doses (<2 mGy). Large deviations between TLD and film measurements of minimum and maximum doses and absorbed doses to the organs occurred at all 5 levels. TLD positioning failed to cover several organ sites; for these, only absorbed dose measurements from the film were available. Conclusions: TLDs were unable to sample dose distributions and gradients accurately. The characteristics of Gafchromic LD-V1 film make it a favorable alternative in dental CBCT dosimetry.
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3.
  • Edén Strindberg, Jerker, et al. (författare)
  • Comparison of Swedish and Norwegian Use of Cone-Beam Computed Tomography : a Questionnaire Study
  • 2015
  • Ingår i: Journal of Oral & Maxillofacial Research. - : Kaunas University of Medicine. - 2029-283X .- 2029-283X. ; 6:4
  • Tidskriftsartikel (refereegranskat)abstract
    • Objectives: Cone-beam computed tomography in dentistry can be used in some countries by other dentists than specialists in radiology. The frequency of buying cone-beam computed tomography to examine patients is rapidly growing, thus knowledge of how to use it is very important. The aim was to compare the outcome of an investigation on the use of cone-beam computed tomography in Sweden with a previous Norwegian study, regarding specifically technical aspects. Material and Methods: The questionnaire contained 45 questions, including 35 comparable questions to Norwegian clinics one year previous. Results were based on inter-comparison of the outcome from each of the two questionnaire studies. Results: Responses rate was 71% in Sweden. There, most of cone-beam computed tomography (CBCT) examinations performed by dental nurses, while in Norway by specialists. More than two-thirds of the CBCT units had a scout image function, regularly used in both Sweden (79%) and Norway (75%). In Sweden 4% and in Norway 41% of the respondents did not wait for the report from the radiographic specialist before initiating treatment. Conclusions: The bilateral comparison showed an overall similarity between the two countries. The survey gave explicit and important knowledge of the need for education and training of the whole team, since radiation dose to the patient could vary a lot for the same kind of radiographic examination. It is essential to establish quality assurance protocols with defined responsibilities in the team in order to maintain high diagnostic accuracy for all examinations when using cone-beam computed tomography for patient examinations.
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4.
  • Gross, Heidi, et al. (författare)
  • Detectability of normal anatomy in digital panoramic radiographs
  • 2014
  • Ingår i: Swedish Dental Journal. - : Swedish Dental Federation. - 0347-9994. ; 38:4, s. 179-185
  • Tidskriftsartikel (refereegranskat)abstract
    • The aim of this study was to evaluate the image quality of digital panoramic radiographs and its correlation with the detectability of normal anatomical structures. The effects of image enhancement on the detectability were also studied. A total of 500 panoramic images (DICOM format) obtained with a storage phosphor-based digital system were evaluated. The image quality and the detectability of selected normal anatomical structures were evaluated in all images. Images with inadequate image quality were subjected to enhancement after which the detectability of the structures was re-evaluated. Only 9% of the images were classified as having adequate technical quality. The main sources of poor image quality were that the patient's tongue was not held against the palate and incorrect positioning of the patient. Not holding the tongue against the palate was found to have a negative impact on the detectability of maxillary structures. Of the images with horizontal positioning errors the patient's head was rotated to the left in 81% (70 images). The most effective form of enhancement was a combination of increased contrast and decreased brightness. Images in which the tongue was not held against the palate were partially improved, whereas images with positioning errors remained unaffected by this enhancement. In conclusion, most of the panoramic images showed some technical flaws. The marginal bone level and the maxillary area were the most difficult areas to reproduce. Retakes could be avoided in some cases by using image enhancement. However, this should not be regarded as an option to avoid poor image quality.
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5.
  • Hajem, Samara, et al. (författare)
  • CBCT of Swedish children and adolescents at an oral and maxillofacial radiology department : A survey of requests and indications.
  • 2020
  • Ingår i: Acta Odontologica Scandinavica. - : Taylor & Francis. - 0001-6357 .- 1502-3850. ; 78:1, s. 38-44
  • Tidskriftsartikel (refereegranskat)abstract
    • This retrospective study investigated requests and indications for cone-beam computed tomography (CBCT) in children and adolescents over a 3-year period at one oral and maxillofacial radiology department. Specific aims were to determine what technical settings were used, which caregivers write the referrals, and how often and for what reasons re-exposure was necessary. Patients
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6.
  • Hellén-Halme, Kristina, et al. (författare)
  • Comparison of the performance of intraoral X-ray sensors using objective image quality assessment
  • 2016
  • Ingår i: Oral surgery, oral medicine, oral pathology and oral radiology. - : Elsevier. - 2212-4403 .- 2212-4411. ; 121:5, s. e129-e137
  • Tidskriftsartikel (refereegranskat)abstract
    • Objectives. The main aim of this study was to evaluate the performance of 10 individual sensors of the same make, using objective measures of key image quality parameters. A further aim was to compare 8 brands of sensors. Study Design. Ten new sensors of 8 different models from 6 manufacturers (i.e., 80 sensors) were included in the study. All sensors were exposed in a standardized way using an X-ray tube voltage of 60 kVp and different exposure times. Sensor response, noise, low-contrast resolution, spatial resolution and uniformity were measured Results. Individual differences between sensors of the same brand were surprisingly large in some cases. There were clear differences in the characteristics of the different brands of sensors. The largest variations were found for individual sensor response for some of the brands studied. Also, noise level and low contrast resolution showed large variations between brands Conclusions. Sensors, even of the same brand, vary significantly in their quality. It is thus valuable to establish action levels for the acceptance of newly delivered sensors and to use objective image quality control for commissioning purposes and periodic checks to ensure high performance of individual digital sensors.
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7.
  • Hellén-Halme, Kristina, et al. (författare)
  • Digital radiography in general dental practice. A field study
  • 2007
  • Ingår i: Dento-Maxillo-Facial Radiology. - : British Institute of Radiology. - 0250-832X .- 1476-542X. ; 36:5, s. 249-255
  • Tidskriftsartikel (refereegranskat)abstract
    • Abstract Objectives: The aim of this study was to conduct a field study to survey the performance of digital radiography and how it was used by dentists in general dental practice. Methods: Nineteen general dental practitioners were visited at their clinics. Ambient light (illuminance) was measured in the rooms where the monitors were placed. Different technical display parameters were noted. Test images and two phantoms—one low-contrast phantom and one line-pair resolution phantom—were used to evaluate the digital system. How the dentists used the enhancement program was investigated by noting which functions were used. Results: Average illuminance in the operating room was 668 lux (range 190–1250 lux). On radiographs of the low-contrast phantom taken at the clinic, the ability to observe the holes decreased as illuminance increased. On average, the “light percentage” initially set on the monitor had to be decreased by 17% and contrast by 10% to optimise the display of the test images. The general dental practitioners used the enhancement programs most often to alter brightness and contrast to obtain the subjectively best image. Large differences between the clinics were noted. Conclusion: Knowledge of how to handle digital equipment in general dental practice should be improved. A calibrated monitor of good quality should be a given priority, as should proper ambient light conditions. There is a need to develop standardised quality controls for digital dental radiography. Key-words: display monitor, enhancement program, digital radiography, quality
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8.
  • Hellén-Halme, Kristina, et al. (författare)
  • Effect of ambient light and monitor brightness and contrast settings on the detection of approximal caries in digital radiographs : an in vitro study
  • 2008
  • Ingår i: Dento-Maxillo-Facial Radiology. - : British Institute of Radiology. - 0250-832X .- 1476-542X. ; 37:7, s. 380-384
  • Tidskriftsartikel (refereegranskat)abstract
    • Objectives: The aim of this study was to investigate how brightness and contrast settings of the display monitor and ambient light level (illuminance) in the viewing room affect the clinician's ability to diagnose carious lesions in digital radiographs. Methods: Standardized radiographs were taken of 100 extracted teeth. Seven observers evaluated the images for approximal carious lesions twice, once under 50 lux and once under 1000 lux room illumination. Monitor brightness and contrast were varied ±50% and ±6%, respectively, to mimic the normal limits of monitor adjustment by an inexperienced user and one optimal setting. This was done by adjusting radiograph brightness and contrast by ±25%. Thus, five radiographs of each tooth were evaluated. Receiver operating characteristic (ROC) analyses were performed. Histological examinations of the teeth served as the criterion standard. A paired t-test was used to evaluate whether differences in the areas under the ROC curves were significant and kappa was used to evaluate intraobserver agreement. Results: When a monitor with optimal brightness and contrast settings was used to detect approximal carious lesions, ambient light levels less than 50 lux were significantly better than levels above 1000 lux (dentin and enamel lesions, P < 0.01; dentin lesions, P < 0.02). Increasing the contrast setting of the monitor by 6% did not change these results; 50 lux was still significantly better than 1000 lux (enamel lesions, P < 0.01; dentin and enamel lesions, P < 0.02) for evaluating radiographs. Intraobserver agreement differed from fair to good. Conclusions: Reducing ambient light to less than 50 lux significantly increased the accuracy of diagnosing approximal carious lesions on a monitor with an optimal brightness setting and an optimal or slightly higher than optimal contrast setting.
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9.
  • Hellén-Halme, Kristina, et al. (författare)
  • Effect of ambient light and monitor brightness and contrast settings on the detection of approximal caries in digital radiographs.
  • 2007
  • Konferensbidrag (refereegranskat)abstract
    • Abstract Aims: The aim of this study was to investigate how brightness and contrast settings of the display monitor and ambient light level (illuminance) in the viewing room affect the clinician’s ability to diagnose carious lesions in digital radiographs. Methods: Standardised radiographs were taken of 100 extracted teeth. Seven observers evaluated the images for approximal carious lesions twice, once under 500-lux and once under 1000-lux room illumination. Radiograph brightness and contrast were varied ±50% and ±6%, respectively, to mimic normal limits of monitor adjustment by an inexperienced user and one optimal setting. Thus, five radiographs of each tooth were made. Receiver operating characteristic (ROC) analyses were performed. Histologic examinations of the teeth served as the criterion standard. A paired t-test was used to evaluate whether differences in the areas under the ROC curves were significant, and kappa was used to evaluate intra-observer agreement. Results: When a monitor with optimal brightness and contrast settings was used to detect approximal carious lesions, ambient light levels less than 50 lux were significantly better than levels above 1000 lux (dentine and enamel lesions, p<0.01; dentine lesions, p<0.02). Increasing the contrast setting of the monitor by 6% did not change these results; 50 lux was still significantly better than 1000 lux (enamel lesions, p<0.01; dentine and enamel lesions, p<0.02) for evaluating radiographs. Intra-observer agreement differed from fair to good. Conclusion: Reducing ambient light to less than 50 lux significantly increased the accuracy of diagnosing approximal carious lesions on a monitor with an optimal brightness setting and an optimal or slightly higher than optimal contrast setting.
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10.
  • Hellén-Halme, Kristina, et al. (författare)
  • Effect of monitors on approximal caries detection in digital radiographs—standard versus precalibrated DICOM part 14 displays : An in vitro study
  • 2009
  • Ingår i: Oral surgery, oral medicine, oral pathology, oral radiology, and endodontics. - 1079-2104 .- 1528-395X. ; 107:5, s. 716-720
  • Tidskriftsartikel (refereegranskat)abstract
    • Objectives. The aim of this study was to evaluate if different ways of adjusting brightness and contrast of monitors with different technical standards influence the diagnosis of carious lesions in digital radiographs. Study design. One hundred extracted teeth (premolars and molars) were radiographed. Seven observers evaluated images for approximal carious lesions on 3 monitors: a standard color monitor with brightness and contrast manually adjusted for viewing radiographs, a Digital Imaging and Communication in Medicine (DICOM) part 14 precalibrated color monitor, and a DICOM part 14 precalibrated monochromatic monitor. All evaluations were made in ambient light <50 lux. Receiver operating characteristic curves were plotted to evaluate results. The standard criterion was a histologic examination of sliced teeth. Kappa statistic evaluated intraobserver agreement. Results. No significant difference in accuracy of approximal carious lesion diagnosis was found between the monitors. Intraobserver agreement varied between fair and good. Conclusion. No differences that could affect clinicians’ abilities to detect carious lesions in digital radiographs existed between the standard monitor and the color and monochrome DICOM part 14 precalibrated monitors.
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