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- Olivecrona, Henrik, et al.
(författare)
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A new computed tomography-based radiographic method to detect early loosening of total wrist implants
- 2007
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Ingår i: Acta Radiologica. - London, UK : Informa Healthcare. - 0284-1851 .- 1600-0455. ; 48:9, s. 997-1003
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 3. |
- Olivecrona, Lotta, et al.
(författare)
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Assessing wear of the acetabular cup using computed tomography : an ex vivo study
- 2005
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Ingår i: Acta Radiologica. - London, UK : Informa Healthcare. - 0284-1851 .- 1600-0455. ; 46:8, s. 852-857
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 8. |
- Maguire Jr., Gerald Q., et al.
(författare)
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A Generic Raster Display for Medical Images : A Description
- 1986
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Ingår i: Nineteenth Annual Hawaii International Conference on System Sciences 1986. Volume 3. - : IEEE and ACM. ; , s. 279-288
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Konferensbidrag (refereegranskat)abstract
- Two major difficulties associated with medical image processing are the diverse image formats that must be dealt with because of the differences in image sources and the number of incompatible display systems available for viewing images both before and after processing. We describe a very small set of primitives which need to be defined to utilize any raster display. When these primitives have been implemented for a particular device, then a standard set of image display programs can be compiled and images and the results of image processing can be displayed. The main purpose of this paper is to describe what a raster display looks like from the point of view of the programmer and to define the specific hardware and software data about the raster display which must be known in order to implement the small set of primitives.
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