oru.sePublications
Change search
Refine search result
1 - 28 of 28
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Alshamari, Muhammed
    et al.
    Örebro University, School of Medical Sciences. Örebro University Hospital. Department of Radiology, Örebro University Hospital, Örebro, Sweden.
    Geijer, Mats
    Örebro University, School of Medical Sciences. Örebro University Hospital. Department of Radiology, Örebro University Hospital, Örebro, Sweden; Department of Medical Imaging and Physiology, Skåne University Hospital, Lund University, Lund, Sweden.
    Norrman, Eva
    Örebro University, School of Medical Sciences. Örebro University Hospital. Department of Medical Physics, Örebro University Hospital, Örebro, Sweden.
    Lidén, Mats
    Örebro University, School of Medical Sciences. Örebro University Hospital. Department of Radiology, Örebro University Hospital, Örebro, Sweden.
    Krauss, Wolfgang
    Örebro University, School of Medical Sciences. Örebro University Hospital. Department of Radiology, Örebro University Hospital, Örebro, Sweden.
    Jendeberg, Johan
    Örebro University, School of Medical Sciences. Örebro University Hospital. Department of Radiology, Örebro University Hospital, Örebro, Sweden.
    Magnuson, Anders
    Örebro University Hospital.
    Geijer, Håkan
    Örebro University, School of Medical Sciences. Örebro University Hospital. Department of Radiology, Örebro University Hospital, Örebro, Sweden.
    Impact of iterative reconstruction on image quality of low-dose CT of the lumbar spine2017In: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 58, no 6, p. 702-709Article in journal (Refereed)
    Abstract [en]

    Background: Iterative reconstruction (IR) is a recent reconstruction algorithm for computed tomography (CT) that can be used instead of the standard algorithm, filtered back projection (FBP), to reduce radiation dose and/or improve image quality.

    Purpose: To evaluate and compare the image quality of low-dose CT of the lumbar spine reconstructed with IR to conventional FBP, without further reduction of radiation dose.

    Material and Methods: Low-dose CT on 55 patients was performed on a Siemens scanner using 120 kV tube voltage, 30 reference mAs, and automatic dose modulation. From raw CT data, lumbar spine CT images were reconstructed with a medium filter (B41f) using FBP and four levels of IR (levels 2-5). Five reviewers scored all images on seven image quality criteria according to the European guidelines on quality criteria for CT, using a five-grade scale. A side-by-side comparison was also performed.

    Results: There was significant improvement in image quality for IR (levels 2-4) compared to FBP. According to visual grading regression, odds ratios of all criteria with 95% confidence intervals for IR2, IR3, IR4, and IR5 were: 1.59 (1.39-1.83), 1.74 (1.51-1.99), 1.68 (1.46-1.93), and 1.08 (0.94-1.23), respectively. In the side-by-side comparison of all reconstructions, images with IR (levels 2-4) received the highest scores. The mean overall CTDIvol was 1.70 mGy (SD 0.46; range, 1.01-3.83 mGy). Image noise decreased in a linear fashion with increased strength of IR.

    Conclusion: Iterative reconstruction at levels 2, 3, and 4 improves image quality of low-dose CT of the lumbar spine compared to FPB.

  • 2.
    Alshamari, Muhammed
    et al.
    Örebro University, School of Medical Sciences. Department of Radiology.
    Geijer, Mats
    Department of Radiology, School of Medical Sciences, Örebro University, Örebro, Sweden; Department of Medical Imaging and Physiology, Skåne University Hospital, Lund; Lund University, Lund, Sweden.
    Norrman, Eva
    Department of Medical Physics, School of Medical Sciences, Örebro University, Örebro, Sweden.
    Lidén, Mats
    Örebro University, School of Health Sciences.
    Krauss, Wolfgang
    Örebro University, School of Health Sciences.
    Jendeberg, Johan
    Örebro University, School of Health Sciences.
    Magnuson, Anders
    Clinical Epidemiology and Biostatistics, School of Medical Sciences, Örebro University, Örebro, Sweden.
    Geijer, Håkan
    Örebro University, School of Health Sciences.
    Impact of iterative reconstruction on image quality of low-dose CT of the lumbar spineManuscript (preprint) (Other academic)
  • 3.
    Alshamari, Muhammed
    et al.
    Örebro University, School of Health and Medical Sciences, Örebro University, Sweden. Department of Radiology, Faculty of Health and Medical Sciences, Örebro University, Örebro, Sweden.
    Geijer, Mats
    Department of Medical Imaging and Physiology, Skåne University Hospital, Lund University, Lund, Sweden.
    Norrman, Eva
    Örebro University, School of Health and Medical Sciences, Örebro University, Sweden. Department of Medical Physics,, Faculty of Health and Medical Sciences, Örebro University, Örebro, Sweden.
    Lidén, Mats
    Örebro University, School of Health and Medical Sciences, Örebro University, Sweden. Department of Radiology, Faculty of Health and Medical Sciences, Örebro University, Örebro, Sweden.
    Krauss, Wolfgang
    Örebro University, School of Health and Medical Sciences, Örebro University, Sweden. Department of Radiology, Faculty of Health and Medical Sciences, Örebro University, Örebro, Sweden.
    Wilamowski, Franciszek
    Department of Radiology, Örebro University Hospital, Örebro, Sweden.
    Geijer, Håkan
    Örebro University, School of Health and Medical Sciences, Örebro University, Sweden. Department of Radiology, Faculty of Health and Medical Sciences, Örebro University, Örebro, Sweden.
    Low dose CT of the lumbar spine compared with radiography: a study on image quality with implications for clinical practice2016In: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 57, no 5, p. 602-611Article in journal (Refereed)
    Abstract [en]

    Background: Lumbar spine radiography is often performed instead of CT for radiation dose concerns.

    Purpose: To compare image quality and diagnostic information from low dose lumbar spine CT at an effective dose of about 1 mSv with lumbar spine radiography.

    Material and Methods: Fifty-one patients were examined by both methods. Five reviewers scored all examinations on eight image quality criteria using a five-graded scale and also assessed three common pathologic changes.

    Results: Low dose CT scored better than radiography on the following: sharp reproduction of disc profile and vertebral end-plates (odds ratio [OR], 1.8; 95% confidence interval [CI], 1.3-2.5), intervertebral foramina and pedicles (OR, 4.3; 95% CI, 3.1-5.9), intervertebral joints (OR, 139; 95% CI, 59-326), spinous and transverse processes (OR, 7.0; 95% CI, 4.3-11.2), sacro-iliac joints (OR, 4.2; 95% CI, 3.2-5.7), reproduction of the adjacent soft tissues (OR, 2.9; 95% CI, 2.1-4.0), and absence of any obscuring superimposed gastrointestinal gas and contents (OR, 188; 95% CI, 66-539). Radiography scored better on sharp reproduction of cortical and trabecular bone (OR, 0.3; 95% CI, 0.2-0.4). The reviewers visualized disk degeneration, spondylosis/diffuse idiopathic skeletal hyperostosis (DISH) and intervertebral joint osteoarthritis more clearly and were more certain with low dose CT. Mean time to review low dose CT was 204 s (95% CI, 194-214 s.), radiography 152 s (95% CI, 146-158 s.). The effective dose for low dose CT was 1.0-1.1 mSv, for radiography 0.7 mSv.

    Conclusion: Low dose lumbar spine CT at about 1 mSv has superior image quality to lumbar spine radiography with more anatomical and diagnostic information.

  • 4. Al-Ubeidy, H.
    et al.
    Alshamari, Muhammed
    Örebro University, School of Medical Sciences. Örebro University Hospital.
    Widell, J.
    Eriksson, T.
    Lidén, Mats
    Örebro University, School of Medical Sciences.
    High-pitch, low-kVp computed tomography for ruling out pulmonary embolism with 17-mL contrast media2019Conference paper (Refereed)
  • 5.
    Andersson, Karin M.
    et al.
    Department of Medical Physics, Faculty of Medicine and Health, Örebro University, Örebro, Sweden; Department of Medical Physics, Örebro University Hospital, Örebro, Sweden.
    Norrman, Eva
    Department of Medical Physics, Faculty of Medicine and Health, Örebro University, Örebro, Sweden.
    Geijer, Håkan
    Örebro University, School of Medical Sciences. Department of Radiology, Örebro University Hospital, Örebro, Sweden.
    Krauss, Wolfgang
    Örebro University, School of Medical Sciences. Department of Radiology, Örebro University Hospital, Örebro, Sweden.
    Cao, Yang
    Clinical Epidemiology and Biostatistics, School of Medical Sciences, Örebro University, Örebro, Sweden; Unit of Biostatistics, Institute of Environmental Medicine, Karolinska Institute, Stockholm, Sweden.
    Jendeberg, Johan
    Örebro University, School of Medical Sciences. Department of Radiology, Örebro University Hospital, Örebro, Sweden.
    Geijer, Mats
    Department of Radiology, Faculty of Medicine and Health, Örebro University, Örebro, Sweden; Department of Clinical Sciences, Lund University, Lund, Sweden.
    Lidén, Mats
    Örebro University, School of Medical Sciences. Department of Radiology, Örebro University Hospital, Örebro, Sweden.
    Thunberg, Per
    Örebro University, School of Medical Sciences. Department of Medical Physics, Örebro University Hospital, Örebro, Sweden .
    Visual grading evaluation of commercially available metal artefact reduction techniques in hip prosthesis computed tomography2016In: British Journal of Radiology, ISSN 0007-1285, E-ISSN 1748-880X, Vol. 89, no 1063, article id 20150993Article in journal (Refereed)
    Abstract [en]

    Objectives: To evaluate metal artefact reduction (MAR) techniques from four computed tomography (CT) vendors in hip prosthesis imaging.

    Methods: Bilateral hip prosthesis phantom images, obtained by using MAR algorithms for single energy CT data or dual energy CT (DECT) data and by monoenergetic reconstructions of DECT data, were visually graded by five radiologists using ten image quality criteria. Comparisons between the MAR images and a reference image were performed for each scanner separately. Ordinal probit regression analysis was used.

    Results: The MAR algorithms in general improved the image quality based on the majority of the criteria (up to between 8/10 and 10/10) with a statistically improvement in overall image quality (P<0.001). However, degradation of image quality, such as new artefacts, was seen in some cases. A few monoenergetic reconstruction series improved the image quality (P<0.004) for one of the DECT scanners, but it was only improved for some of the criteria (up to 5/10). Monoenergetic reconstructions resulted in worse image quality for the majority of the criteria (up to 7/10) for the other DECT scanner.

    Conclusions: The MAR algorithms improved the image quality of the hip prosthesis CT images. However, since additional artefacts and degradation of image quality were seen in some cases, all algorithms should be carefully evaluated for every clinical situation. Monoenergetic reconstructions were in general concluded to be insufficient for reducing metal artifacts. Advances in knowledge: Qualitative evaluation of the usefulness of several MAR techniques from different vendors in CT imaging of hip prosthesis.

  • 6.
    Hellstrandh Jorstig, Stina
    et al.
    Örebro University, School of Medical Sciences.
    Waldenborg, Micael
    Örebro University, School of Health Sciences. Department of Clinical Physiology, Örebro University Hospital, Örebro, Sweden.
    Lidén, Mats
    Örebro University, School of Medical Sciences. Department of Radiology, Örebro University Hospital, Örebro, Sweden.
    Wodecki, Maciej
    Department of Clinical Physiology, Faculty of Medicine and Health, Örebro University, Örebro, Sweden.
    Thunberg, Per
    Örebro University, School of Medical Sciences. Department of Medical Physics, Örebro University Hospital, Örebro, Sweden.
    Determination of Right Ventricular Volume by Combining Echocardiographic Distance Measurements2016In: Echocardiography, ISSN 0742-2822, E-ISSN 1540-8175, Vol. 33, no 6, p. 844-853Article in journal (Refereed)
    Abstract [en]

    Background: The position of the right ventricle (RV), often partly behind the sternum, implies difficulties to image the RV free wall using transthoracic echocardiography (TTE) and consequently limits the possibilities of stroke volume calculations. The aim of this study was to evaluate whether the volume of the right ventricle (RV) can be determined by combining TTE distance measurements that do not need the RV free wall to be fully visualized.

    Methods: The RV volume was approximated by an ellipsoid composed of three distances. Distance measurements, modeled RV stroke volumes (RVSV), and RV ejection fraction (RVEF) were compared to reference values obtained from cardiac magnetic resonance (CMR) imaging for 12 healthy volunteers.

    Results: Inter-modality comparisons showed that distance measurements were significantly underestimated in TTE compared to CMR. The modeled RV volumes using TTE distance measurements were underestimated compared to reference CMR volumes. There was, however, for TTE an agreement between modeled RVSV and left ventricular stroke volumes determined by biplane Simpson's rule. Similar agreement was shown between modeled RVSV based on CMR distance measurements and the CMR reference. Regarding RVEF, further studies including patients with a wider range of RVEF are needed to evaluate the method.

    Conclusion: In conclusion, the ellipsoid model of the RV provides good estimates of RVSVs, but volumes based on distance measurements from different modalities cannot be used interchangeably.

  • 7.
    Jendeberg, Johan
    et al.
    Örebro University, School of Medical Sciences.
    Cierzniak, B.
    Alshamari, Muhammed
    Örebro University, School of Medical Sciences. Örebro University Hospital.
    Geijer, Håkan
    Örebro University, School of Medical Sciences.
    Lidén, Mats
    Örebro University, School of Medical Sciences.
    Prognosis of spontaneous ureteral stone passage: as revealed by CT2016Conference paper (Refereed)
  • 8.
    Jendeberg, Johan
    et al.
    Örebro University, School of Medical Sciences. Department of Radiology, Faculty of Health and Medical Sciences, Örebro University, Örebro, Sweden.
    Geijer, Håkan
    Örebro University, School of Medical Sciences. Department of Radiology, Faculty of Health and Medical Sciences, Örebro University, Örebro, Sweden.
    Alshamari, Muhammed
    Örebro University, School of Medical Sciences. Örebro University Hospital. Department of Radiology, Örebro University Hospital, Örebro, Sweden.
    Cierzniak, Bartosz
    Department of Surgery, Faculty of Medicine and Health, Örebro University, Örebro, Sweden.
    Lidén, Mats
    Örebro University, School of Medical Sciences. Department of Radiology, Faculty of Health and Medical Sciences, Örebro University, Örebro, Sweden.
    Size matters: The width and location of a ureteral stone accurately predict the chance of spontaneous passage2017In: European Radiology, ISSN 0938-7994, E-ISSN 1432-1084, Vol. 27, no 11, p. 4775-4785Article in journal (Refereed)
    Abstract [en]

    OBJECTIVES: To determine how to most accurately predict the chance of spontaneous passage of a ureteral stone using information in the diagnostic non-enhanced computed tomography (NECT) and to create predictive models with smaller stone size intervals than previously possible.

    METHODS: Retrospectively 392 consecutive patients with ureteric stone on NECT were included. Three radiologists independently measured the stone size. Stone location, side, hydronephrosis, CRP, medical expulsion therapy (MET) and all follow-up radiology until stone expulsion or 26 weeks were recorded. Logistic regressions were performed with spontaneous stone passage in 4 weeks and 20 weeks as the dependent variable.

    RESULTS: The spontaneous passage rate in 20 weeks was 312 out of 392 stones, 98% in 0-2 mm, 98% in 3 mm, 81% in 4 mm, 65% in 5 mm, 33% in 6 mm and 9% in ≥6.5 mm wide stones. The stone size and location predicted spontaneous ureteric stone passage. The side and the grade of hydronephrosis only predicted stone passage in specific subgroups.

    CONCLUSION: Spontaneous passage of a ureteral stone can be predicted with high accuracy with the information available in the NECT. We present a prediction method based on stone size and location.

    KEY POINTS: • Non-enhanced computed tomography can predict the outcome of ureteral stones. • Stone size and location are the most important predictors of spontaneous passage. • Prediction models based on stone width or length and stone location are introduced. • The observed passage rates for stone size in mm-intervals are reported. • Clinicians can make better decisions about treatment.

  • 9.
    Jendeberg, Johan
    et al.
    Örebro University, School of Medical Sciences. Department of Radiology, Faculty of Health and Medical Sciences, Örebro University, Örebro, Sweden.
    Geijer, Håkan
    Örebro University, School of Medical Sciences. Department of Radiology, Faculty of Health and Medical Sciences, Örebro University, Örebro, Sweden.
    Alshamari, Muhammed
    Örebro University, School of Medical Sciences. Örebro University Hospital. Department of Radiology, Örebro University Hospital, Örebro, Sweden.
    Lidén, Mats
    Örebro University, School of Medical Sciences. Department of Radiology, Faculty of Health and Medical Sciences, Örebro University, Örebro, Sweden.
    Prediction of spontaneous ureteral stone passage: Automated 3D-measurements perform equal to radiologists, and linear measurements equal to volumetric2018In: European Radiology, ISSN 0938-7994, E-ISSN 1432-1084, Vol. 28, no 6, p. 2474-2483Article in journal (Refereed)
    Abstract [en]

    OBJECTIVES: To compare the ability of different size estimates to predict spontaneous passage of ureteral stones using a 3D-segmentation and to investigate the impact of manual measurement variability on the prediction of stone passage.

    METHODS: We retrospectively included 391 consecutive patients with ureteral stones on non-contrast-enhanced CT (NECT). Three-dimensional segmentation size estimates were compared to the mean of three radiologists' measurements. Receiver-operating characteristic (ROC) analysis was performed for the prediction of spontaneous passage for each estimate. The difference in predicted passage probability between the manual estimates in upper and lower stones was compared.

    RESULTS: The area under the ROC curve (AUC) for the measurements ranged from 0.88 to 0.90. Between the automated 3D algorithm and the manual measurements the 95% limits of agreement were 0.2 ± 1.4 mm for the width. The manual bone window measurements resulted in a > 20 percentage point (ppt) difference between the readers in the predicted passage probability in 44% of the upper and 6% of the lower ureteral stones.

    CONCLUSIONS: All automated 3D algorithm size estimates independently predicted the spontaneous stone passage with similar high accuracy as the mean of three readers' manual linear measurements. Manual size estimation of upper stones showed large inter-reader variations for spontaneous passage prediction.

    KEY POINTS:• An automated 3D technique predicts spontaneous stone passage with high accuracy.• Linear, areal and volumetric measurements performed similarly in predicting stone passage.• Reader variability has a large impact on the predicted prognosis for stone passage.

  • 10.
    Jorstig, Stina
    et al.
    Örebro University, School of Medical Sciences. Örebro University Hospital.
    Emilsson, Kent
    Department of Clinical Physiology, Faculty of Medicine and Health, Örebro University, Örebro, Sweden.
    Waldenborg, Micael
    Örebro University, School of Health Sciences. Örebro University Hospital. Department of Clinical Physiology, Örebro University Hospital, Örebro, Sweden.
    Lidén, Mats
    Örebro University, School of Medical Sciences. Örebro University Hospital. Department of Radiology, Örebro University Hospital, Örebro, Sweden.
    Wodecki, M.
    Department of Clinical Physiology, Faculty of Health and Medical Sciences, Örebro University, Örebro, Sweden.
    Thunberg, Per
    Örebro University, School of Medical Sciences. Örebro University Hospital. Department of Medical Physics, Örebro University Hospital, Örebro, Sweden.
    Distance and area measurement of the right atrium and ventricle by echocardiography and cardiac magnetic resonance imaging: do we measure the same thing?2016Conference paper (Other academic)
    Abstract [en]

    Purpose: It has previously been shown that stroke volumes measured by transthoracic echocardiography (TTE) are underestimated, compared to cardiac magnetic resonance (CMR) imaging. The purpose of this study was to evaluate differences in distance and area measurements of the right atrium (RA) and the right ventricle (RV) by TTE and CMR.

    Methods: TTE examinations and CMR examinations were subsequently performed in 12 healthy volunteers. Three distances (RAL - right atrial length, RVIT3 - right ventricular inflow tract, RVLAX - right ventricular long axis) and one area (RVA - right ventricular area) were measured in TTE and CMR. Stroke volumes were also calculated using conventional methods available on each modality. Both intramodality and intermodality comparisons were performed based on measurements from three observers. One of the observers performed measurements in both TTE and CMR.

    Results: Intermodality comparisons showed that all distance and area measurements were significantly smaller using TTE (Table 1). Two of the measurements, RVIT3 and RVA, differed at about 50%. Calculated stroke volumes showed, consistent with previous results, that the TTE stroke volumes are substantially underestimated compared to CMR volumes. Intramodality variations of distance and area measurements were considerably smaller (Table 1).

    Conclusions: Our results show that RV distances and areas measured by TTE are smaller compared to CMR, probably due to differences in defining the endocardial borders. These differences subsequently result in smaller stroke volumes when using TTE. Caution should be taken when comparing distances, areas and volumes measured by TTE and CMR.

  • 11.
    Jorstig, Stina Hellstrand
    et al.
    Örebro University, School of Health and Medical Sciences, Örebro University, Sweden. Örebro University Hospital.
    Emilsson, Kent
    Örebro University, School of Health and Medical Sciences, Örebro University, Sweden. Department of Clinical Physiology, Örebro University Hospital, Örebro, Sweden.
    Lidén, Mats
    Örebro University, School of Health and Medical Sciences, Örebro University, Sweden. Örebro University Hospital. Department of Radiology, Örebro University Hospital, Örebro, Sweden.
    Thunberg, Per
    Örebro University Hospital. Department of Medical Physics, Örebro University Hospital, Örebro, Sweden.
    A study to determine the contribution to right ventricle stroke volume from pulmonary and tricuspid valve displacement volumes2015In: Clinical Physiology and Functional Imaging, ISSN 1475-0961, E-ISSN 1475-097X, Vol. 35, no 4, p. 283-290Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: Describing the systolic function of the right ventricle (RV) is a difficult task due to the complex shape and orientation of the RV. The purpose of this study was to investigate the extent to which the volumes encompassed by the pulmonary and tricuspid valve displacements contribute to the total right ventricle stroke volume (RVSV).

    METHODS: Twelve healthy volunteers were examined using cardiac magnetic resonance (CMR). Two series of time-resolved axially rotated MR images were acquired that encompassed the tricuspid valve and the pulmonary valve, respectively. The volume related to each valve movement, the tricuspid plane displacement (TPD) and the pulmonary plane displacement (PPD), was determined by delineation in diastole and systole. These volumes, RVSVTPD and RVSVPPD , were compared to the stroke volume to determine the contributions to the total stroke volume from the TPD and the PPD. The remaining volume of the total RVSV was referred to as RVSVOther . An initial in vitro study was carried out to validate the accuracy of volume measurements using axially rotated images.

    RESULTS: In vitro measurements indicated that the method for volumetric measurements using axially rotated images was a very accurate one, with a mean difference of 0·04 ± 0·10 ml. The in vivo measurements of RVSVTPD , RVSVPPD and RVSVOther were 45 ± 10%, 13 ± 2% and 42 ± 11%, respectively.

    CONCLUSIONS: Right ventricle stroke volume is determined by different individual volume changes as follows: RVSVTPD together with RVSVOther contributes to almost the entire RVSV in nearly equal proportions, while RVSVPPD contributes only a small amount and is approximately 30% of either RVSVTPD or RVSVOther.

  • 12.
    Jorstig, Stina
    et al.
    Örebro University, School of Medical Sciences.
    Waldenborg, Micael
    School of Medical Sciences, Faculty of Medicine and Health, Örebro University, Örebro, Sweden.
    Lidén, Mats
    Örebro University, School of Medical Sciences.
    Thunberg, Per
    Örebro University, School of Medical Sciences.
    Right ventricular ejection fraction measurements using twodimensional echocardiographyManuscript (preprint) (Other academic)
  • 13.
    Jorstig, Stina
    et al.
    Örebro University, School of Medical Sciences. Örebro University Hospital. Faculty of Medicine and Health, Örebro University Biomedical Engineering, Örebro University Hospital, Örebro, Sweden.
    Waldenborg, Micael
    Örebro University Hospital. Örebro University, School of Medical Sciences. Faculty of Medicine and Health and Department of Clinical Physiology, Faculty of Medicine and Health, Örebro University, Örebro, Sweden.
    Lidén, Mats
    Örebro University, School of Medical Sciences. Örebro University Hospital. Faculty of Medicine and Health and Department of Radiology, Faculty of Medicine and Health, Örebro University, Örebro, Sweden.
    Thunberg, Per
    Örebro University, School of Medical Sciences. Örebro University Hospital. Faculty of Medicine and Health and Department of Medical Physics, Department of Medical Physics, Faculty of Medicine and Health, Örebro University, Örebro, Sweden.
    Right ventricular ejection fraction measurements using two-dimensional transthoracic echocardiography by applying an ellipsoid model2017In: Cardiovascular Ultrasound, ISSN 1476-7120, E-ISSN 1476-7120, Vol. 15, article id 4Article in journal (Refereed)
    Abstract [en]

    Background: There is today no established approach to estimate right ventricular ejection fraction (RVEF) using 2D transthoracic echocardiography (TTE). The aim of this study was to evaluate a new method for RVEF calculations using 2D TTE and compare the results with cardiac magnetic resonance (CMR) imaging and tricuspid annular plane systolic excursion (TAPSE).

    Methods: A total of 37 subjects, 25 retrospectively included patients and twelve healthy volunteers, were included to give a wide range of RVEF. The right ventricle (RV) was modeled as a part of an ellipsoid enabling calculation of the RV volume by combining three distance measurements. RVEF calculated according to the model, RVEFTTE, were compared with reference CMR-derived RVEF, RVEFCMR. Further, TAPSE was measured in the TTE images and the correlations were calculated between RVEFTTE, TAPSE and RVEFCMR.

    Results: The mean values were RVEFCMR = 43 +/- 12% (range 20-66%) and RVEFTTE = 50 +/- 9% (range 34-65%). There was a high correlation (r = 0.80, p < 0.001) between RVEFTTE and RVEFCMR. Bland-Altman analysis showed a mean difference between RVEFCMR and RVEFTTE of 6 percentage points (ppt) with limits of agreement from -11 to 23 ppt. The mean value for TAPSE was 19 +/- 5 mm and the correlation between TAPSE and RVEFCMR was moderate (r = 0.54, p < 0.001). The correlation between RVEFTTE and RVEFCMR was significantly higher (p < 0.05) than the correlation between TAPSE and RVEFCMR.

    Conclusions: The ellipsoid model shows promise for RVEF calculations using 2D TTE for a wide range of RVEF, providing RVEF estimates that were significantly better correlated to RVEF obtained from CMR compared to TAPSE.

  • 14.
    Lidén, Mats
    Örebro University Hospital. Örebro University, School of Medical Sciences. Department of Radiology, Örebro University Hospital, Örebro, Sweden.
    A new method for predicting uric acid composition in urinary stones using routine single-energy CT2018In: Urolithiasis, ISSN 2194-7228, Vol. 46, no 4, p. 325-332Article in journal (Refereed)
    Abstract [en]

    Urinary stones composed of uric acid can be treated medically. Prediction of uric acid stone type is, therefore, desirable when a urinary stone is diagnosed with unenhanced CT. The purpose of the present study was to describe single-energy thin slice quantitative CT parameters of urinary stones correlated to chemical stone type and to develop a method to distinguish pure uric acid stones (UA) from other stones (non-UA/Mix). Unenhanced thin slice single-energy CT images of 126 urinary stones (117 patients) with known chemical stone type were retrospectively included in the study. Among the included stones, 22 were UA and 104 were non-UA/Mix. The included CT images and Laplacian filtered images of the stones were quantitatively analyzed using operator-independent methods. A post hoc classification method for pure UA stones was created using a combination of cutoff values for the peak attenuation and peak point Laplacian. The stone types differed in most quantitative image characteristics including mean attenuation (p < 0.001), peak attenuation (p < 0.001), and peak point Laplacian (p < 0.001). The sensitivity for the post hoc-developed peak attenuation-peak point Laplacian method for classifying pure UA stones was 95% [21/22, 95% CI (77-100%)] and the specificity was 99% [103/104, 95% CI (95-100%)]. In conclusion, quantitative image analysis of thin slice routine single-energy CT images is promising for predicting pure UA content in urinary stones, with results comparable to double energy methods.

  • 15.
    Lidén, Mats
    Örebro University, School of Health and Medical Sciences, Örebro University, Sweden.
    The stack mode review of volumetric datasets: applications for urinary stone disease2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    During the last decades the acquisition and visualization of radiological images have rapidly evolved. The increasing amounts of volumetric image data particularly from modern CT systems necessitate a constant evolution of the radiological visualization techniques.

    The dominating display mode for volumetric images has been the stack mode display since its introduction in computerized image review. In the increasing amounts of image data, the stack mode display needs to be analyzed so that the information content in the high resolution datasets can be transformed into clinically relevant information for the management of the individual patient. In the present thesis some aspects of the stack mode display were analyzed using for the most part the size estimation of urinary stones in unenhanced CT as a model.

    The estimated size has an important correlation to the prognosis for spontaneous passage of an obstructing ureteral stone. In the present thesis the reader variations in the size estimation of urinary stones were quantified, using different visualization parameters and after an attempt to reduce the variations with a training session for the readers. The influence on the estimated stone size of CT image post processing parameters was quantified. A segmentation algorithm was developed and demonstrated to reduce the reader variability through reader independent computer aid. One limitation of the stack mode display concerns three-dimensional shapes, which was modeled by a comparison between the estimated length and width of urinary stones in two- and three-dimensional segmentation. The increasing number of image slices in the acquisitions introduces a need for efficient navigation of the image volumes. In the present thesis the navigation of CT datasets using different user interface devices was evaluated.

    The rapid evolution of the MRI and CT systems necessitates a constant refinement and evaluation of the cornerstone for radiological volumetric reviewing – the stack mode display of volumetric datasets.

    List of papers
    1. Alternative user interface devices for improved navigation of CT datasets
    Open this publication in new window or tab >>Alternative user interface devices for improved navigation of CT datasets
    2011 (English)In: Journal of digital imaging, ISSN 0897-1889, E-ISSN 1618-727X, Vol. 24, no 1, p. 126-134Article in journal (Refereed) Published
    Abstract [en]

    The workflow in radiology departments has changed dramatically with the transition to digital PACS, especially with the shift from tile mode to stack mode display of volumetric images. With the increasing number of images in routinely captured datasets, the standard user interface devices (UIDs) become inadequate. One basic approach to improve the navigation of the stack mode datasets is to take advantage of alternative UIDs developed for other domains, such as the computer game industry. We evaluated three UIDs both in clinical practice and in a task-based experiment. After using the devices in the daily image interpretation work, the readers reported that both of the tested alternative UIDs were better in terms of ergonomics compared to the standard mouse and that both alternatives were more efficient when reviewing large CT datasets. In the task-based experiment, one of the tested devices was faster than the standard mouse, while the other alternative was not significantly faster. One of the tested alternative devices showed a larger number of traversed images during the task. The results indicate that alternative user interface devices can improve the navigation of stack mode datasets and that radiologists should consider the potential benefits of alternatives to the standard mouse.

    Place, publisher, year, edition, pages
    Springer, 2011
    Keywords
    navigation, user interface, PACS, computed tomography
    National Category
    Medical and Health Sciences Radiology, Nuclear Medicine and Medical Imaging
    Research subject
    Medicine
    Identifiers
    urn:nbn:se:oru:diva-12074 (URN)10.1007/s10278-009-9252-2 (DOI)000286469600014 ()19949832 (PubMedID)2-s2.0-79751523933 (Scopus ID)
    Available from: 2010-10-05 Created: 2010-10-05 Last updated: 2019-03-26Bibliographically approved
    2. Making renal stones change size: impact of CT image post processing and reader variability
    Open this publication in new window or tab >>Making renal stones change size: impact of CT image post processing and reader variability
    2011 (English)In: European Radiology, ISSN 0938-7994, E-ISSN 1432-1084, Vol. 21, no 10, p. 2218-2225Article in journal (Refereed) Published
    Abstract [en]

    Objectives The objectives of this study were to quantify the impact of image post-processing parameters on the apparent renal stone size, and to quantify the intra- and inter-reader variability in renal stone size estimation. Methods Fifty CT datasets including a renal or ureteral stone were included retrospectively during a prospective inclusion period. Each of the CT datasets was post-processed in different ways regarding slice thickness, slice increment and window setting. In the first part of the study a single reader repeated size estimations for the renal stones using different post-processing parameters. In the intra-reader variability experiment one reader reported size estimations for the same images with a one-week interval. The inter-reader variability data were obtained from 11 readers reporting size estimations for the same renal stones. Results The apparent stone size differed according to image post-processing parameters with the largest mean differences seen with regard to the window settings experiment (1.5 mm, p < 0.001) and slice thickness (0.8 mm, p < 0.001). Changes in parameters introduced a bias and a pseudo-random variability. The inter-reader variability was considerably larger than the intra-reader variability. Conclusion Our results indicate a need for the standardisation of making measurements on CT images.

    National Category
    Medical and Health Sciences
    Research subject
    Medicine
    Identifiers
    urn:nbn:se:oru:diva-18641 (URN)10.1007/s00330-011-2171-x (DOI)000294471100027 ()
    Available from: 2011-09-30 Created: 2011-09-29 Last updated: 2019-03-26Bibliographically approved
    3. Urinary stone size estimation: Can we reduce the reader variations?
    Open this publication in new window or tab >>Urinary stone size estimation: Can we reduce the reader variations?
    (English)Manuscript (preprint) (Other academic)
    National Category
    Radiology, Nuclear Medicine and Medical Imaging
    Research subject
    Radiology
    Identifiers
    urn:nbn:se:oru:diva-30363 (URN)
    Available from: 2013-08-29 Created: 2013-08-29 Last updated: 2019-03-26Bibliographically approved
    4. Urinary stone size estimation: a new segmentation algorithm-based CT method
    Open this publication in new window or tab >>Urinary stone size estimation: a new segmentation algorithm-based CT method
    Show others...
    2012 (English)In: European Radiology, ISSN 0938-7994, E-ISSN 1432-1084, Vol. 22, no 4, p. 731-737Article in journal (Refereed) Published
    Abstract [en]

    The size estimation in CT images of an obstructing ureteral calculus is important for the clinical management of a patient presenting with renal colic. The objective of the present study was to develop a reader independent urinary calculus segmentation algorithm using well-known digital image processing steps and to validate the method against size estimations by several readers. Fifty clinical CT examinations demonstrating urinary calculi were included. Each calculus was measured independently by 11 readers. The mean value of their size estimations was used as validation data for each calculus. The segmentation algorithm consisted of interpolated zoom, binary thresholding and morphological operations. Ten examinations were used for algorithm optimisation and 40 for validation. Based on the optimisation results three segmentation method candidates were identified. Between the primary segmentation algorithm using cubic spline interpolation and the mean estimation by 11 readers, the bias was 0.0 mm, the standard deviation of the difference 0.26 mm and the Bland-Altman limits of agreement 0.0 +/- 0.5 mm. The validation showed good agreement between the suggested algorithm and the mean estimation by a large number of readers. The limit of agreement was narrower than the inter-reader limit of agreement previously reported for the same data. The size of kidney stones is usually estimated manually by the radiologist. An algorithm for computer-aided size estimation is introduced. The variability between readers can be reduced. A reduced variability can give better information for treatment decisions.

    Place, publisher, year, edition, pages
    New York, USA: Springer, 2012
    Keywords
    X-ray computed tomography, ureteral calculi, kidney stone, computer-assisted image processing, computer-assisted image interpretation
    National Category
    Medical and Health Sciences Radiology, Nuclear Medicine and Medical Imaging
    Research subject
    Medicine
    Identifiers
    urn:nbn:se:oru:diva-22493 (URN)10.1007/s00330-011-2309-x (DOI)000301496900002 ()22160167 (PubMedID)2-s2.0-84861461077 (Scopus ID)
    Note

    Funding Agency:

    Knowledge Foundation, Stockholm, Sweden 

    Available from: 2012-04-10 Created: 2012-04-10 Last updated: 2019-03-26Bibliographically approved
    5. Two- and three-dimensional CT measurements of urinary calculi length and width: a comparative study
    Open this publication in new window or tab >>Two- and three-dimensional CT measurements of urinary calculi length and width: a comparative study
    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    The standard imaging procedure for a patient presenting with renal colic is unenhanced CT. The CT measured size has a close correlation to the estimated prognosis for spontaneous passage of a ureteral calculus. Size estimations of urinary calculi in CT images are still based on 2d-reformats. In the present study we developed and validated a calculus oriented 3dmethod for measurements of length and width of urinary calculi and compared those with corresponding 2d measurements in axial and coronal reformats.

    Methods: Fifty unenhanced CT examinations demonstrating urinary calculi were included. A 3d-symmetric segmentation algorithm was validated against reader size estimations. The calculus-oriented size from the segmentation was then compared to the size in axial and coronal reformats.

    Results: The validation showed 0.1±0.7 mm agreement against reference measure. There was a 0.4 mm median bias for 3d-estimated calculus length compared to 2d (p<0.001), but no significant bias for 3d-width compared to 2d.

    Conclusion: The size of the urinary calculus becomes underestimated if its orientation is not aligned to the axial or coronal image plane. Future studies aiming to correlate calculus size with patient outcome should use a calculus oriented size estimation.

    Keywords
    3D segmentation; tomography, X-ray computed; image perception; imaging, three- dimensional; image segmentation; image visualization; ureteral calculi; urinary stones; urolithiasis
    National Category
    Radiology, Nuclear Medicine and Medical Imaging
    Research subject
    Radiology
    Identifiers
    urn:nbn:se:oru:diva-30364 (URN)
    Available from: 2013-08-29 Created: 2013-08-29 Last updated: 2019-03-26Bibliographically approved
  • 16.
    Lidén, Mats
    et al.
    Örebro University, School of Health and Medical Sciences, Örebro University, Sweden. Department of Radiology, Örebro University Hospital, Örebro, Sweden.
    Andersson, Torbjörn
    Örebro University, School of Health and Medical Sciences, Örebro University, Sweden.
    Broxvall, Mathias
    Örebro University, School of Science and Technology.
    Thunberg, Per
    Örebro University, School of Health and Medical Sciences, Örebro University, Sweden. Department of Medical Physics, Örebro University Hospital, Örebro, Sweden.
    Geijer, Håkan
    Örebro University, School of Health and Medical Sciences, Örebro University, Sweden.
    Urinary stone size estimation: a new segmentation algorithm-based CT method2012In: European Radiology, ISSN 0938-7994, E-ISSN 1432-1084, Vol. 22, no 4, p. 731-737Article in journal (Refereed)
    Abstract [en]

    The size estimation in CT images of an obstructing ureteral calculus is important for the clinical management of a patient presenting with renal colic. The objective of the present study was to develop a reader independent urinary calculus segmentation algorithm using well-known digital image processing steps and to validate the method against size estimations by several readers. Fifty clinical CT examinations demonstrating urinary calculi were included. Each calculus was measured independently by 11 readers. The mean value of their size estimations was used as validation data for each calculus. The segmentation algorithm consisted of interpolated zoom, binary thresholding and morphological operations. Ten examinations were used for algorithm optimisation and 40 for validation. Based on the optimisation results three segmentation method candidates were identified. Between the primary segmentation algorithm using cubic spline interpolation and the mean estimation by 11 readers, the bias was 0.0 mm, the standard deviation of the difference 0.26 mm and the Bland-Altman limits of agreement 0.0 +/- 0.5 mm. The validation showed good agreement between the suggested algorithm and the mean estimation by a large number of readers. The limit of agreement was narrower than the inter-reader limit of agreement previously reported for the same data. The size of kidney stones is usually estimated manually by the radiologist. An algorithm for computer-aided size estimation is introduced. The variability between readers can be reduced. A reduced variability can give better information for treatment decisions.

  • 17.
    Lidén, Mats
    et al.
    Örebro University, School of Health and Medical Sciences.
    Andersson, Torbjörn
    Örebro University, School of Health and Medical Sciences.
    Geijer, Håkan
    Örebro University, School of Health and Medical Sciences.
    Alternative user interface devices for improved navigation of CT datasets2011In: Journal of digital imaging, ISSN 0897-1889, E-ISSN 1618-727X, Vol. 24, no 1, p. 126-134Article in journal (Refereed)
    Abstract [en]

    The workflow in radiology departments has changed dramatically with the transition to digital PACS, especially with the shift from tile mode to stack mode display of volumetric images. With the increasing number of images in routinely captured datasets, the standard user interface devices (UIDs) become inadequate. One basic approach to improve the navigation of the stack mode datasets is to take advantage of alternative UIDs developed for other domains, such as the computer game industry. We evaluated three UIDs both in clinical practice and in a task-based experiment. After using the devices in the daily image interpretation work, the readers reported that both of the tested alternative UIDs were better in terms of ergonomics compared to the standard mouse and that both alternatives were more efficient when reviewing large CT datasets. In the task-based experiment, one of the tested devices was faster than the standard mouse, while the other alternative was not significantly faster. One of the tested alternative devices showed a larger number of traversed images during the task. The results indicate that alternative user interface devices can improve the navigation of stack mode datasets and that radiologists should consider the potential benefits of alternatives to the standard mouse.

  • 18.
    Lidén, Mats
    et al.
    Örebro University, School of Health and Medical Sciences.
    Andersson, Torbjörn
    Örebro University, School of Medicine, Örebro University, Sweden.
    Geijer, Håkan
    Örebro University, School of Health and Medical Sciences.
    Making renal stones change size: impact of CT image post processing and reader variability2011In: European Radiology, ISSN 0938-7994, E-ISSN 1432-1084, Vol. 21, no 10, p. 2218-2225Article in journal (Refereed)
    Abstract [en]

    Objectives The objectives of this study were to quantify the impact of image post-processing parameters on the apparent renal stone size, and to quantify the intra- and inter-reader variability in renal stone size estimation. Methods Fifty CT datasets including a renal or ureteral stone were included retrospectively during a prospective inclusion period. Each of the CT datasets was post-processed in different ways regarding slice thickness, slice increment and window setting. In the first part of the study a single reader repeated size estimations for the renal stones using different post-processing parameters. In the intra-reader variability experiment one reader reported size estimations for the same images with a one-week interval. The inter-reader variability data were obtained from 11 readers reporting size estimations for the same renal stones. Results The apparent stone size differed according to image post-processing parameters with the largest mean differences seen with regard to the window settings experiment (1.5 mm, p < 0.001) and slice thickness (0.8 mm, p < 0.001). Changes in parameters introduced a bias and a pseudo-random variability. The inter-reader variability was considerably larger than the intra-reader variability. Conclusion Our results indicate a need for the standardisation of making measurements on CT images.

  • 19.
    Lidén, Mats
    et al.
    Örebro University, School of Health and Medical Sciences, Örebro University, Sweden.
    Andersson, Torbjörn
    Örebro University, School of Medicine, Örebro University, Sweden.
    Geijer, Håkan
    Örebro University, School of Health and Medical Sciences, Örebro University, Sweden.
    Urinary stone size estimation: Can we reduce the reader variations?Manuscript (preprint) (Other academic)
  • 20.
    Lidén, Mats
    et al.
    Örebro University, School of Medical Sciences.
    Jendeberg, Johan
    Örebro University, School of Medical Sciences.
    Längkvist, Martin
    Örebro University, School of Science and Technology.
    Loutfi, Amy
    Örebro University, School of Science and Technology.
    Thunberg, Per
    Örebro University, School of Medical Sciences.
    Discrimination between distal ureteral stones and pelvic phleboliths in CT using a deep neural network: more than local features needed2018Conference paper (Refereed)
    Abstract [en]

    Purpose: To develop a deep learning method for assisting radiologists in the discrimination between distal ureteral stones and pelvic phleboliths in thin slice CT images, and to evaluate whether this differentiation is possible using only local features.

    Methods and materials: A limited field-of-view image data bank was retrospectively created, consisting of 5x5x5 cm selections from 1 mm thick unenhanced CT images centered around 218 pelvis phleboliths and 267 distal ureteral stones in 336 patients. 50 stones and 50 phleboliths formed a validation cohort and the remainder a training cohort. Ground truth was established by a radiologist using the complete CT examination during inclusion.The limited field-of-view CT stacks were independently reviewed and classified as containing a distal ureteral stone or a phlebolith by seven radiologists. Each cropped stack consisted of 50 slices (5x5 cm field-of-view) and was displayed in a standard PACS reading environment. A convolutional neural network using three perpendicular images (2.5D-CNN) from the limited field-of-view CT stacks was trained for classification.

    Results: The 2.5D-CNN obtained 89% accuracy (95% confidence interval 81%-94%) for the classification in the unseen validation cohort while the accuracy of radiologists reviewing the same cohort was 86% (range 76%-91%). There was no statistically significant difference between 2.5D-CNN and radiologists.

    Conclusion: The 2.5D-CNN achieved radiologist level classification accuracy between distal ureteral stones and pelvic phleboliths when only using the local features. The mean accuracy of 86% for radiologists using limited field-of-view indicates that distant anatomical information that helps identifying the ureter’s course is needed.

  • 21.
    Lidén, Mats
    et al.
    Örebro University, School of Health and Medical Sciences, Örebro University, Sweden.
    Thunberg, Per
    Örebro University, School of Health and Medical Sciences, Örebro University, Sweden. Kliniskt forskningscentrum (KFC), Univeritetssjukhuset, Örebro, Sverige.
    Broxvall, Mathias
    Örebro University, School of Science and Technology.
    Geijer, Håkan
    Örebro University, School of Health and Medical Sciences, Örebro University, Sweden.
    Two- and three-dimensional CT measurements of urinary calculi length and width: a comparative studyManuscript (preprint) (Other academic)
    Abstract [en]

    The standard imaging procedure for a patient presenting with renal colic is unenhanced CT. The CT measured size has a close correlation to the estimated prognosis for spontaneous passage of a ureteral calculus. Size estimations of urinary calculi in CT images are still based on 2d-reformats. In the present study we developed and validated a calculus oriented 3dmethod for measurements of length and width of urinary calculi and compared those with corresponding 2d measurements in axial and coronal reformats.

    Methods: Fifty unenhanced CT examinations demonstrating urinary calculi were included. A 3d-symmetric segmentation algorithm was validated against reader size estimations. The calculus-oriented size from the segmentation was then compared to the size in axial and coronal reformats.

    Results: The validation showed 0.1±0.7 mm agreement against reference measure. There was a 0.4 mm median bias for 3d-estimated calculus length compared to 2d (p<0.001), but no significant bias for 3d-width compared to 2d.

    Conclusion: The size of the urinary calculus becomes underestimated if its orientation is not aligned to the axial or coronal image plane. Future studies aiming to correlate calculus size with patient outcome should use a calculus oriented size estimation.

  • 22.
    Lidén, Mats
    et al.
    Örebro University, School of Health and Medical Sciences, Örebro University, Sweden. Örebro University Hospital. Department of Radiology, Örebro University Hospital, Örebro, Sweden; Center for Medical Image Science and Visualization (CMIV), Linköping University, Linköping, Sweden.
    Thunberg, Per
    Örebro University Hospital. Örebro University, School of Health and Medical Sciences, Örebro University, Sweden. School of Health and Medical Sciences, Örebro University, Örebro, Sweden; Department of Medical Physics, Örebro University Hospital, Örebro, Sweden.
    Broxvall, Mathias
    Modeling and Simulation Research Center, Örebro University, Örebro, Sweden.
    Geijer, Håkan
    Örebro University, School of Health and Medical Sciences, Örebro University, Sweden. Örebro University Hospital. Department of Radiology, Örebro University Hospital, Örebro, Sweden.
    Two- and three-dimensional CT measurements of urinary calculi length and width: a comparative study2015In: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 56, no 4, p. 487-492Article in journal (Refereed)
    Abstract [en]

    Background: The standard imaging procedure for a patient presenting with renal colic is unenhanced computed tomography (CT). The CT measured size has a close correlation to the estimated prognosis for spontaneous passage of a ureteral calculus. Size estimations of urinary calculi in CT images are still based on two-dimensional (2D) reformats.

    Purpose: To develop and validate a calculus oriented three-dimensional (3D) method for measuring the length and width of urinary calculi and to compare the calculus oriented measurements of the length and width with corresponding 2D measurements obtained in axial and coronal reformats.

    Material and Methods: Fifty unenhanced CT examinations demonstrating urinary calculi were included. A 3D symmetric segmentation algorithm was validated against reader size estimations. The calculus oriented size from the segmentation was then compared to the estimated size in axial and coronal 2D reformats.

    Results: The validation showed 0.1 +/- 0.7mm agreement against reference measure. There was a 0.4mm median bias for 3D estimated calculus length compared to 2D (P < 0.001), but no significant bias for 3D width compared to 2D.

    Conclusion: The length of a calculus in axial and coronal reformats becomes underestimated compared to 3D if its orientation is not aligned to the image planes. Future studies aiming to correlate calculus size with patient outcome should use a calculus oriented size estimation.

  • 23.
    Lidén, Mats
    et al.
    Örebro University, School of Medical Sciences.
    Wodecki, Maciej
    Department of Clinical Physiology, Faculty of Medicine and Health, Örebro University, Örebro, Sweden.
    Thunberg, Per
    Örebro University, School of Medical Sciences. Department of Medical Physics.
    Rask, Peter
    Örebro University Hospital. Örebro University, School of Medical Sciences.
    Impact of Heart Rate on Flow Measurements in Aortic Regurgitation2017In: Journal of Heart Valve Disease, ISSN 0966-8519, E-ISSN 2053-2644, Vol. 26, no 5, p. 502-508, article id 4562Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: Flow measurements using cardiac magnetic resonance imaging (CMRI) enable quantification of the stroke volume, regurgitant volume (RV) and regurgitant fraction (RF) in patients with aortic regurgitation (AR). These variables are used to assess the severity of the valve disease and for the timing of surgery. The aim of the study was to investigate the impact of an increased heart rate on measurement of the RV and RF in patients with AR.

    METHODS: Among 13 patients with known moderate or severe AR, regurgitant flow measurements, using phase-contrast cine magnetic resonance imaging, were obtained in the ascending aorta. Flow measurements were obtained at rest and at increased heart rates after intravenous administration of atropine.

    RESULTS: The mean heart rate was 61 beats per min at rest and 91 beats per min after atropine administration. The RV and RF were 52 ml and 35% at rest, respectively, and 34 ml (p <0.001) and 30% (p = 0.065) at increased heart rate, respectively.

    CONCLUSIONS: An increased heart rate leads to a decreased RV. The RF is more stable and may therefore be preferable for severity grading in AR.

  • 24.
    Lundin, Margareta
    et al.
    Department of Radiology, Örebro University Hospital, Örebro University, Örebro, Sweden.
    Liden, Mats
    Örebro University, School of Health and Medical Sciences, Örebro University, Sweden. Department of Radiology, Örebro University Hospital, Örebro University, Örebro, Sweden.
    Magnuson, Anders
    Clinical Epidemiology and Biostatistic Unit, Örebro University Hospital, Örebro, Sweden.
    Mohammed, Ahmed Abdulilah
    Department of Radiology, Linköping University Hospital, Linköping, Sweden.
    Geijer, Håkan
    Örebro University, School of Health and Medical Sciences, Örebro University, Sweden. Department of Radiology, Örebro University Hospital, Örebro University, Örebro, Sweden.
    Andersson, Torbjörn
    Örebro University, School of Health and Medical Sciences, Örebro University, Sweden. Department of Radiology, Örebro University Hospital, Örebro University, Örebro, Sweden.
    Persson, Anders
    Center for Medical Image Science and Visualization (CMIV), Linköping University, Linköping, Sweden.
    Virtual non-contrast dual-energy CT compared to single-energy CT of the urinary tract: a prospective study2012In: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 53, no 6, p. 689-694Article in journal (Refereed)
    Abstract [en]

    Background: Dual-energy computed tomography (DECT) has been shown to be useful for subtracting bone or calcium in CT angiography and gives an opportunity to produce. a virtual non-contrast-enhanced (VNC) image from a series where contrast agents have been given intravenously. High noise levels and low resolution have previously limited the diagnostic value of the VNC images created with the first generation of DECT. With the recent introduction of a second generation of DECT, there is a possibility of obtaining VNC images with better image quality at hopefully lower radiation dose compared to the previous generation.

    Purpose: To compare the image quality of the single-energy series to a VNC series obtained with a two generations of DECT scanners. CT of the urinary tract was used as a model.

    Material and Methods: Thirty patients referred for evaluation of hematuria were examined with an older system (Somatom Definition) and another 30 patients with a new generation (Somatom Definition Flash). One single-energy series was obtained before and one dual-energy series after administration of intravenous contrast media. We created a VNC series from the contrast-enhanced images. Images were assessed concerning image quality with a visual grading scale evaluation of the VNC series with the single-energy series as gold standard.

    Results: The image quality of the VNC images was rated inferior to the single-energy variant for both scanners, OR 11.5-67.3 for the Definition and OR 2.1-2.8 for the Definition Flash. Visual noise and overall quality were regarded as better with Flash than Definition.

    Conclusion: Image quality of VNC images obtained with the new generation of DECT is still slightly inferior compared to native images. However, the difference is smaller with the new compared to the older system.

  • 25.
    Längkvist, Martin
    et al.
    Örebro University, School of Science and Technology.
    Jendeberg, Johan
    Örebro University, School of Medical Sciences. Department of Radiology, Faculty of Health and Medical Sciences, Örebro University, Örebro, Sweden.
    Thunberg, Per
    Örebro University, School of Medical Sciences. Department of Medical Physics, Faculty of Health and Medical Sciences, Örebro University, Örebro, Sweden.
    Loutfi, Amy
    Örebro University, School of Science and Technology.
    Lidén, Mats
    Örebro University, School of Medical Sciences. Department of Radiology, Faculty of Health and Medical Sciences, Örebro University, Örebro, Sweden.
    Computer aided detection of ureteral stones in thin slice computed tomography volumes using Convolutional Neural Networks2018In: Computers in Biology and Medicine, ISSN 0010-4825, E-ISSN 1879-0534, Vol. 97, p. 153-160Article in journal (Refereed)
    Abstract [en]

    Computed tomography (CT) is the method of choice for diagnosing ureteral stones - kidney stones that obstruct the ureter. The purpose of this study is to develop a computer aided detection (CAD) algorithm for identifying a ureteral stone in thin slice CT volumes. The challenge in CAD for urinary stones lies in the similarity in shape and intensity of stones with non-stone structures and how to efficiently deal with large high-resolution CT volumes. We address these challenges by using a Convolutional Neural Network (CNN) that works directly on the high resolution CT volumes. The method is evaluated on a large data base of 465 clinically acquired high-resolution CT volumes of the urinary tract with labeling of ureteral stones performed by a radiologist. The best model using 2.5D input data and anatomical information achieved a sensitivity of 100% and an average of 2.68 false-positives per patient on a test set of 88 scans.

  • 26.
    Samano, Ninos
    et al.
    Örebro University, School of Health and Medical Sciences, Örebro University, Sweden. Department of Cardiothoracic and Vascular Surgery, Örebro University Hospital, Örebro, Sweden.
    Geijer, Håkan
    Örebro University, School of Health and Medical Sciences, Örebro University, Sweden.
    Lidén, Mats
    Örebro University, School of Health and Medical Sciences, Örebro University, Sweden.
    Fremes, Stephen
    Division of Cardiac Surgery, Schulich Heart Centre, Sunnybrook Health Sciences Centre, Toronto ON, Canada.
    Bodin, Lennart
    Intervention and Implementation Research, Institute of Environmental Medicine, Karolinska Institute, Stockholm, Sweden.
    Souza, Domingos S. R.
    Department of Cardiothoracic and Vascular Surgery, Faculty of Medicine and Health, Örebro University, Örebro, Sweden.
    The no-touch saphenous vein for coronary artery bypass grafting maintains a patency, after 16 years, comparable to the left internal thoracic artery: a randomized trial2015In: Journal of Thoracic and Cardiovascular Surgery, ISSN 0022-5223, E-ISSN 1097-685X, Vol. 150, no 4, p. 880-888Article in journal (Refereed)
    Abstract [en]

    Objectives: This study investigates whether the no-touch (NT) vein graft, at a mean time of 16 years, maintains a significantly higher patency rate than conventional (C) vein grafts and still has patency comparable to that of the left internal thoracic artery (LITA).

    Methods: A total of 156 patients accepted for coronary artery bypass grafting were randomly allocated to 1 of 3 groups. In the C group, the saphenous vein (SV) was stripped and distended. In the intermediate group, the SV was stripped but not distended. In the NT group, the SV was neither stripped nor distended, but rather harvested with a fat pedicle. This study is an angiographic follow-up of the C and NT groups, at a mean time of 16 years postoperatively.

    Results: Fifty-four patients were included (C group = 27; NT group = 27). In all, 72 and 75 vein grafts were completed in groups C and NT, respectively. Crude SV graft patency was 64% in the C group versus 83% in the NT group (P = .03), which was similar to the patency of the LITA (88%). The harvesting technique had a major impact on the patency with a hazard ratio for occlusion of 1.83 for the C group (P = .04).

    Conclusions: Harvesting the SV with the NT technique conferred, at a mean time of 16 years, a significantly higher patency than the conventional technique that was still comparable to that of the LITA.

  • 27.
    Waldenborg, Micael
    et al.
    Örebro University, School of Health and Medical Sciences, Örebro University, Sweden.
    Lidén, Mats
    Örebro University, School of Health and Medical Sciences, Örebro University, Sweden.
    Kähäri, Anders
    Department of Radiology, School of Health and Medical Sciences, Örebro University, Örebro, Sweden .
    Emilsson, Kent
    Örebro University, School of Health and Medical Sciences, Örebro University, Sweden.
    Effect on left ventricular mass and geometry in patients with takotsubo cardiomyopathy2015In: Scandinavian Cardiovascular Journal, ISSN 1401-7431, E-ISSN 1651-2006, Vol. 49, no 1, p. 27-38Article in journal (Refereed)
    Abstract [en]

    Objectives: Takotsubo cardiomyopathy (TTC) is a condition of transient left ventricular (LV) dysfunction. The effects on LV mass (LVM) and geometry have not been studied enough in TTC. Retrospectively, we analyzed our TTC cohort both by transthoracic echocardiography (TTE) and magnetic resonance imaging (MRI), for comparative purposes.

    Design: Thirteen women undergoing TTE and MRI, at onset and three months later, were included. LVM was estimated by MRI, and two TTE-methods. Segmental wall thickness (SWT) was measured, whilst radial strain was assessed by TTE. Data analysis included Wilcoxon's test (between phases), Mann Whitney U- and McNemar's tests (between and within groups). Bland-Altman analyzes were used for intertechnique coherence, whilst interactions regarding TTE were tested using Spearman's coefficient.

    Results: LVM decreased during recovery (p<0.05), by MRI and one of the TTE-methods; truncated ellipsoid formula (TEF), which also showed relatively better coherence compared to MRI. SWT decreased in two of three sites, by both modalities, but with ambiguous coherence therebetween. The TEF-data interacted partially with a demonstrated increase in radial strain.

    Conclusions: TTC associates with acute increase in LVM, which appears to be an apical effect, tending to follow the changes in concentric wall motion. MRI and TTE show adequate coherence; primarily for the TEF-method regarding LVM.

  • 28.
    Waldenborg, Micael
    et al.
    Örebro University, School of Health and Medical Sciences, Örebro University, Sweden. Department of Clinical Physiology, Örebro University Hospital, Örebro, Sweden.
    Lidén, Mats
    Department of Radiology, Örebro University Hospital, Örebro, Sweden.
    Kähäri, Anders
    Department of Radiology, Örebro University Hospital, Örebro, Sweden.
    Emilsson, Kent
    Department of Clinical Physiology, Örebro University Hospital, Örebro, Sweden.
    Effect on left ventricular mass and geometry in patients with takotsubo cardiomyopathyManuscript (preprint) (Other academic)
    Abstract [en]

    Aims: Takotsubo cardiomyopathy (TTC) is a condition of reversible left ventricular (LV) dysfunction. The effects, from acute to recovery phase, on LV mass (LVM) and the LV geometry are not thoroughly enough studied at TTC, which were the main aims of the present study. Retrospectively, we analyzed our cohort of TTC-patients, both with transthoracic echocardiography (TTE) and magnetic resonance imaging (MRI), to further investigate these changes, including intertechnique comparison.

    Methods: We studied 13 female TTC-patients, undergoing TTE and MRI acutely, and three months later at follow-up. LVM was measured with MRI- and five different TTE-methods. Segmental wall thickness (SWT) was assessed, and used for LV hypertrophy (LVH) geometry categorization. Radial strain was measured at TTE. Data analysis included Wilcoxon signed-test (between phases), Mann Whitney U- and McNemar’s tests (between and within groups). Spearman’s coefficient was used for intertechnique coherence (with BlandAltman plots) and for correlations of simultaneous TTE changes.

    Results: LVM decreased significantly between phases (p<0.05), by MRI and with two TTE-methods. Two of three SWT-sites became significantly thinner, with adequate correlation (rs≥0.69) between techniques, while LVH categories remained unchanged. Relatively better consistency, compared with MRI, was shown for one of the TTE-methods used to estimate LVM (truncated ellipsoid (TE)). Radial strain improved significantly, with partial correlation towards the TE-method.

    Conclusions: TTC associates with acute increase in LVM, which seems to be a local effect, tending to occur in parallel with changes in concentric wall motion. MRI and TTE shows adequate consistency, primarily for the TE-method regarding LVM.

1 - 28 of 28
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf