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  • 1. Fröberg, Asa
    et al.
    Mårtensson, Mattias
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik.
    Larsson, Matilda
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik.
    Janerot-Sjöberg, Birgitta
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik.
    D'Hooge, Jan
    Arndt, Anton
    High variability in strain estimation errors when using a commercial ultrasound speckle tracking algorithm on tendon tissue2016Inngår i: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 57, nr 10, s. 1223-1229Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Background: Ultrasound speckle tracking offers a non-invasive way of studying strain in the free Achilles tendon where no anatomical landmarks are available for tracking. This provides new possibilities for studying injury mechanisms during sport activity and the effects of shoes, orthotic devices, and rehabilitation protocols on tendon biomechanics. Purpose: To investigate the feasibility of using a commercial ultrasound speckle tracking algorithm for assessing strain in tendon tissue. Material and Methods: A polyvinyl alcohol (PVA) phantom, three porcine tendons, and a human Achilles tendon were mounted in a materials testing machine and loaded to 4% peak strain. Ultrasound long-axis cine-loops of the samples were recorded. Speckle tracking analysis of axial strain was performed using a commercial speckle tracking software. Estimated strain was then compared to reference strain known from the materials testing machine. Two frame rates and two region of interest (ROI) sizes were evaluated. Results: Best agreement between estimated strain and reference strain was found in the PVA phantom (absolute error in peak strain: 0.21 +/- 0.08%). The absolute error in peak strain varied between 0.72 +/- 0.65% and 10.64 +/- 3.40% in the different tendon samples. Strain determined with a frame rate of 39.4Hz had lower errors than 78.6Hz as was the case with a 22mm compared to an 11mm ROI. Conclusion: Errors in peak strain estimation showed high variability between tendon samples and were large in relation to strain levels previously described in the Achilles tendon.

  • 2.
    Olivecrona, Henrik
    et al.
    Karolinska Institute, Department of Molecular Medicine and Surgery.
    Noz, Marilyn E.
    New York University, Department of Radiology.
    Maguire Jr., Gerald Q.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Zeleznik, Michael P.
    Saya Systems Inc., Salt Lake City, UT, USA.
    Sollerman, Christer M.
    Handkirurgiska verksamhetsområdet, Sahlgrenska Universitetssjukhuset/Sahlgrenska, Göteborg.
    Olivecrona, Lotta
    Karolinska Institutet, Department of Clinical Science, Intervention and Technology, Division of Radiology.
    A new computed tomography-based radiographic method to detect early loosening of total wrist implants2007Inngår i: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 48, nr 9, s. 997-1003Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Background: Diagnosis of loosening of total wrist implants is usually late using routine radiographs. Switching modality to computed tomography (CT) should aid in early diagnosis. Purpose: To propose and evaluate the accuracy of a new CT method for assessing loosening of the carpal component in total wrist arthroplasty. Material and Methods: A protocol encompassing volume registration of paired CT scans of patients with unexplained pain in a prosthetically replaced wrist (used in clinical routine) is presented. Scans are acquired as a dynamic examination under torsional load. Using volume registration, the carpal component of the prosthesis is brought into spatial alignment. After registration, prosthetic loosening is diagnosed by a shift in position of the bones relative to the prosthesis. This study is a preclinical validation of this method using a human cadaverous arm with a cemented total wrist implant and tantalum markers. Seven CT scans of the arm were acquired. The scans were combined into 21 pairs of CT volumes. The carpal component was registered in each scan pair, and the residual mismatch of the surrounding tantalum markers and bone was analyzed both visually and numerically. Results: The detection limit for prosthetic movement was less than 1 mm. Conclusion: The results of this study demonstrate that CT volume registration holds promise to improve detection of movement of the carpal component at an earlier stage than is obtainable with plain radiography.

  • 3.
    Olivecrona, Henrik
    et al.
    Karolinska Institute, Department of Molecular Medicine and Surgery.
    Olivecrona, Lotta
    Karolinska Institutet, Department of Clinical Science, Intervention and Technology, Division of Radiology.
    Weidenhielm, Lars
    Karolinska Institute, Department of Molecular Medicine and Surgery.
    Noz, Marilyn E.
    New York University, Department of Radiology.
    Maguire Jr., Gerald Q.
    KTH, Tidigare Institutioner, Mikroelektronik och informationsteknik, IMIT.
    Zeleznik, Michael P.
    RAHD Oncology Products, St. Lous, MO, USA.
    Svensson, Lars E.
    KTH, Skolan för teknikvetenskap (SCI), Matematik (Inst.).
    Jonson, T.
    Stability of acetabular axis after total hip arthroplasty, repeatability using CT and a semiautomated program for volume fusion2003Inngår i: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 44, nr 6, s. 653-661Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Purpose: To validate a CT method for detecting changes in acetabular cup orientation after THA. Material and Methods: 26 CT examinations were obtained from a pelvic model with an uncemented acetabular cup. The model position was altered between acquisitions, but the cup axis angle vis-a-vis the pelvis was maintained. Data sets were combined into 37 pairs, each containing a unique positioning error. The pelvi in different examinations were fused, creating transformed volumes. Landmarks corresponding to the cup before and after fusion were placed interactively by two independent examiners. The orientation of the acetabular axis was calculated for each volume and compared across volumes. Results: Before fusion the mean angle error between the acetabular axes was 4.17degrees (SD +/- 1.95degrees). After fusion the mean angle error was 0.36degrees (SD +/- 0.17). The 95% repeatability limits were below 0.7degrees. There was no significant interobserver difference. Analysis of the cup landmarking pattern by condition numbers and individual landmark errors showed stability. Conclusion: Non-invasive fusion of CT volumes and a stable landmarking pattern for the acetabular cup outperforms routine plain radiography in detecting changes in the orientation of the acetabular axis over time. The method delivers both visual and numerical output and could be used in clinical practice.

  • 4.
    Olivecrona, Henrik
    et al.
    Soder Sjukhuset, Dept Hand Surgery.
    Weidenhielm, Lars
    Karolinska Hosp, Dept Orthoped.
    Olivecrona, Lotta
    Karolinska Hosp, Dept Radiologyy.
    Noz, Marilyn E.
    New York University, Department of Radiology.
    Maguire Jr., Gerald Q.
    KTH, Tidigare Institutioner, Mikroelektronik och informationsteknik, IMIT.
    Zeleznik, Michael P.
    RAHD Oncology Products, St. Louis, MO, USA.
    Svensson, Lars E.
    KTH, Skolan för teknikvetenskap (SCI), Matematik (Inst.).
    Jonson, T.
    Spatial component position in total hip arthroplasty - Accuracy and repeatability with a new CT method2003Inngår i: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 44, nr 1, s. 84-91Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Purpose: 3D detection of centerpoints of prosthetic cup and head after total hip arthroplasty (THA) using CT. Material and Methods: Two CT examinations, 10 min apart, were obtained from each of 10 patients after THA. Two independent examiners placed landmarks in images of the prosthetic cup and head. All landmarking was repeated after 1 week. Centerpoints were calculated and compared. Results: Within volumes, all measurements of centerpoints of cup and head fell, with a 95% confidence, within one CT-voxel of any other measurement of the same object. Across two volumes, the mean error of distance between center of cup and prosthetic head was 1.4 mm (SD 0.73). Intra- and interobserver 95% accuracy limit was below 2 mm within and below 3 mm across volumes. No difference between intra- and interobserver measurements occurred. A formula for converting finite sets of point landmarks in the radiolucent tread of the cup to a centerpoint was stable. The percent difference of the landmark distances from a calculated spherical surface was within one CT-voxel. This data was normally distributed and not dependent on observer or trial. Conclusion: The true 3D position of the centers of cup and prosthetic head can be detected using CT. Spatial relationship between the components can be analyzed visually and numerically.

  • 5.
    Olivecrona, Lotta
    et al.
    Karolinska Institutet, Department of Clinical Science, Intervention and Technology, Division of Radiology.
    Aspelin, Peter
    Karolinska Institutet, Department of Clinical Science, Intervention and Technology, Division of Radiology.
    Weidenhielm, Lars
    Karolinska Institute, Department of Molecular Medicine and Surgery.
    Stark, Andreas
    Karolinska Institute, Department of Molecular Medicine and Surgery.
    Noz, Marilyn E.
    New York University, Department of Radiology.
    Maguire Jr., Gerald Q.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Zeleznik, Michael P.
    RAHD Oncol Prod, St Louis, MO USA .
    Svensson, Lars E.
    KTH, Skolan för teknikvetenskap (SCI), Matematik (Inst.).
    Olivecrona, Henrik
    Soder Sjukhuset, Dept Hand Surgery.
    Standard orientation of the pelvis: Validation on a model and ten patients2005Inngår i: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 46, nr 1, s. 74-82Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Purpose: To validate an image post-processing method for re-orienting the pelvis in CT volumes to a standardized orientation in a model and in 10 patients. Material and Methods: Twenty-four CT volumes of a pelvic model and 10 pairs of postoperative total hip arthroplasty (THA) patient CT scans were rotated to a defined pelvic standard orientation and the rotation was recorded. For precision, a test-retest procedure was used. For accuracy, three exactly represented coordinate points were used. For clinical application, the standard orientation was used for calculating the direction of acetabular cup migration from a previous model study. Results: Precision of pelvic standard orientation, calculated as maximal directional error, was better than 1degrees in the model study and better than 1.5degrees in the patient study. Accuracy, expressed as angle between ideal and measured coordinate axes, was 0.1degrees for x, y, z axes. No measurable systematic errors were found. When applied to acetabular cup migration in the model, standardization of pelvic orientation had no significant effect on the measurements. Conclusion: Reorienting the pelvis during image post-processing was shown to be accurate. It enables measurements relative to the pelvis and minimizes the dependency of patient positioning.

  • 6.
    Olivecrona, Lotta
    et al.
    Karolinska Hospital, Department of Radiology.
    Crafoord, Joakim
    Karolinska Hospital, Department of Radiology.
    Olivecrona, Henrik
    Karolinska Hosp, Dept Orthopaed.
    Noz, Marilyn E.
    New York University, Department of Radiology.
    Maguire Jr., Gerald Q.
    KTH, Tidigare Institutioner, Mikroelektronik och informationsteknik, IMIT.
    Zeleznik, Michael P.
    RAHD Oncology Products, St. Louism MO, USA.
    Svensson, Lars E.
    KTH, Skolan för teknikvetenskap (SCI), Matematik (Inst.).
    Weidenhielm, Lars
    Karolinska Hosp, Dept Orthopaed.
    Acetabular component migration in total hip arthroplasty using CT and a semiautomated program for volume merging2002Inngår i: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 43, nr 5, s. 517-527Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Purpose: To develop a non-invasive method for detection of acetabular cup migration after total hip arthroplasty (THA) with a higher degree of accuracy than routine plain radiography. Material and Methods: Two CT examinations, 10 min apart, were obtained from each of 10 patients that had undergone THA. Using an in-house developed semiautomated program for volume merging, the pelves in the two examinations were fused and the acetabular cup was visually and numerically evaluated to test the method's accuracy in detecting migration. Results: In the visual evaluation of the best match a 1-mm translation of the cup was detectable. The numerical evaluation, comparing landmarks placed in the images of the acetabular cup and the head of the femur component in the two examinations, showed the mean difference in orientation of acetabular axes to be 2.5degrees, the mean distance between centre of cup face to be 2.5 mm and the mean distance between centre of the head of the prosthetic femoral component to be 1 mm. Conclusion: This method has a significantly higher accuracy than routine plain radiography in detecting acetabular cup migration and could be used in clinical practice. It gives both a visual and a numerical correlate to migration.

  • 7.
    Olivecrona, Lotta
    et al.
    Karolinska Institutet, Department of Clinical Science, Intervention and Technology, Division of Radiology.
    Jedenmalm, Anneli
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Aspelin, Peter
    Karolinska Institutet, Department of Clinical Science, Intervention and Technology, Division of Radiology.
    Weidenhielm, Lars
    Karolinska Institutet, Dept. Orthoped..
    Noz, Marilyn E.
    New York University, Department of Radiology.
    Maguire Jr., Gerald Q.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Zeleznik, Michael P.
    RAHD Oncology Products, St. Louis. Mo.
    Olivecrona, Henrik
    Department of Hand Surgery, Södersjukhuset, Stockholm.
    Assessing wear of the acetabular cup using computed tomography: an ex vivo study2005Inngår i: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 46, nr 8, s. 852-857Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Purpose: To validate a clinically useful method for measuring acetabular cup wear using computed tomography (CT). Material and Methods: Eight uncemented acetabular cups were scanned twice ex vivo using CT. The linear penetration depth of the femoral component head into the cup and the thickness of the remaining polyethylene liner were measured in the CT volumes using dedicated software. Two independent examiners twice assessed each volume. The CT measurements were compared to direct measurements using a coordinate measuring device and micrometer measurements. Results: Accuracy of wear measurements expressed as penetration depth was +/- 0.6 and +/- 1.0 mm for the two examiners, respectively, with no significant differences between examiners, trials, and CT scans. Accuracy of measurements of remaining polyethylene was +/- 1.3 and +/- 1.0 mm, respectively, for the two examiners. Systematic differences between examiners were found, but no significant differences between trials and CT scans. These differences were due to different interpretations of metal artifacts in the volumes. Conclusion: The proposed CT method for evaluating wear as head penetration depth allows for reliable wear detection at a clinically relevant level. Measurements of remaining polyethylene on CT volumes are not as reliable as wear measurements owing to metal artifacts.

  • 8.
    Olivecrona, Lotta
    et al.
    Karolinska Hosp, Dept Radiology.
    Olivecrona, Henrik
    Soder Sjukhuset, Dept Hand Surg, Stockholm, Sweden .
    Weidenhielm, Lars
    Karolinska Institute, Department of Molecular Medicine and Surgery.
    Noz, Marilyn E.
    New York University, Department of Radiology.
    Maguire Jr., Gerald Q.
    KTH, Tidigare Institutioner, Mikroelektronik och informationsteknik, IMIT.
    Zeleznik, Michael P.
    RAHD Oncology Products, St. Louis, MO, USA.
    Model studies on acetabular component migration in total hip arthroplasty using CT and a semiautomated program for volume merging2003Inngår i: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 44, nr 4, s. 419-429Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Purpose: Validation of a non-invasive CT method for detection of acetabular cup migration after total hip arthroplasty in a phantom study. Material and Methods: 26 CT examinations were obtained of a pelvic model while altering the position of the acetabular cup. Using a previously described program for volume merging, the pelvi in different examinations were fused and the 3D alterations of the position of the acetabular cup were evaluated visually and numerically and correlated to direct measurements on the model. Results: Visually, two independent examiners differentiated between 0, 1 and 2 to 3 mm migration with 100% specificity and sensitivity. Numerically, the mean error over all cases between model and CT measurements was 0.04 mm (SD +/- 0.33). The mean absolute error between model and CT data was 0.26 mm (SD +/- 0.19). Intra- and interobserver 95% accuracy and repeatability limits were below 0.5/0.7 mm, respectively. No significant interobserver difference occurred. The data were normally distributed and not dependent on observer. Conclusion: The accuracy of this non-invasive method out-performs routine plain radiography. The method gives both visual and numerical correlates to migration and can be used in clinical practice.

  • 9.
    Svedmark, Per
    et al.
    Karolinska Institutet at Karolinska University Hospital Solna and Stockholm Spine Center, Löwenströmska Hospital.
    Lundh, Fredrik
    Nemeth, Gunnar
    Capio S:t Göran Sjukhuset.
    Noz, Marilyn E.
    New York University, Department of Radiology.
    Maguire, Gerald Q., Jr.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Zeleznik, Michael P.
    University of Utah.
    Olivecrona, Henrik
    Karolinska Institutet at Karolinska University Hospital Solna.
    Motion analysis of total cervical disc replacements using computed tomography: Preliminary experience with nine patients and a model2011Inngår i: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 52, nr 10, s. 1128-1137Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Background: Cervical total disc replacement (CTDR) is an alternative to anterior fusion. Therefore, it is desirable to have an accurate in vivo measurement of prosthetic kinematics and assessment of implant stability relative to the adjacent vertebrae. Purpose: To devise an in vivo CT-based method to analyze the kinematics of cervical total disc replacements (CTDR), specifically of two prosthetic components between two CT scans obtained under different conditions. Material and Methods: Nine patients with CTDR were scanned in flexion and extension of the cervical spine using a clinical CT scanner with a routine low-dose protocol. The flexion and extension CT volume data were spatially registered, and the prosthetic kinematics of two prosthetic components, an upper and a lower, was calculated and expressed in Euler angles and orthogonal linear translations relative to the upper component. For accuracy analysis, a cervical spine model incorporating the same disc replacement as used in the patients was also scanned and processed in the same manner. Results: Analysis of both the model and patients showed good repeatability, i.e. within 2 standard deviations of the mean using the 95% limits of agreement with no overlapping confidence intervals. The accuracy analysis showed that the median error was close to zero. Conclusion: The mobility of the cervical spine after total disc replacement can be effectively measured in vivo using CT. This method requires an appropriate patient positioning and scan parameters to achieve suitable image quality.

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