| 1. |
- Moy, Linda, et al.
(författare)
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Improving specificity of breast MRI using prone PET and fused MRI and PET 3D volume datasets
- 2007
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Ingår i: Journal of Nuclear Medicine. - Reston, Virginia, USA : Society of Nuclear Medicine. - 0161-5505 .- 1535-5667. ; 48:4, s. 528-537
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Tidskriftsartikel (refereegranskat)abstract
- MRI is a sensitive method for detecting invasive breast cancer, but it lacks specificity. To examine the effect of combining PET with MRI on breast lesion characterization, a prototype positioning device was fabricated to allow PET scans to be acquired in the same position as MRI scans-that is, prone. Methods: To test the hypothesis that fusion of 18F-FDG PET and MRI scans improves detection of breast cancer, 23 patients with suspected recurrent or new breast cancer underwent a routine whole-body PET scan, a prone PET scan of the chest, and a routine breast MRJ scan. The attenuation-corrected prone PET and MRI clatasets were registered twice by different operators. The fusion results were judged for quality by visual inspection and statistical analysis. A joint reading of the MRI and PET scans side by side and integrated images was performed by a nuclear medicine physician and a radiologist. Sensitivity and specificity of MRI and combined MRI and PET scans were calculated on the basis of pathology reports or at least 1 y of clinical and radiologic follow-up. Results: All fusions were verified to be well matched using specific anatomic criteria. A total of 45 lesions was assessed. Lesion size range was 0.6 to 10.0 cm. Of the 44 breasts examined, 29 were suspicious for cancer, of which 15 were found to be positive on surgical excision. In lesion-by-lesion analysis, sensitivity and specificity of MRI alone were 92% and 52%, respectively; after MRI and PETfusion, they were 63% and 95%, respectively. The positive predictive value and the negative predictive value for MRI alone were 69% and 85%, respectively; after MRI and PET fusion, they were 94% and 69%, respectively. Conclusion: Acquisition of prone PET scans using the new positioning device permitted acquisition of prone scans suitable for fusion with breast MRI scans. Fused PET and MRI scans increased the specificity of MRI but decreased the sensitivity in this small group of patients. Additional data are needed to confirm the statistical significance of these preliminary findings.
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| 2. |
- Moy, Linda, et al.
(författare)
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Prone mammoPET acquisition improves the ability to fuse MRI and PET breast scans
- 2007
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Ingår i: Clinical Nuclear Medicine. - Philadephia, Pennsylvania, USA : Lippincott Williams & Wilkins. - 0363-9762 .- 1536-0229. ; 32:3, s. 194-198
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: This study compared prone acquisition of PET scans with traditional supine acquisition to improve fusion of PET scans with MRI scans and improve evaluation of enhancing breast lesions detected on MRI. Materials and Methods: MRI breast scans are acquired in the prone position using a breast coil to allow the breasts to hang pendant. An apparatus was fabricated to allow prone acquisition of PET scans. Fused scans from 2 patients acquired both prone and supine were contrasted with those from 3 patients acquired supine only. All 5 MRI scans were acquired on standard scanners. The PET scans were acquired with a PET/CT unit using a low-dose CT scan for attenuation correction. The PET and MRI volumes were matched twice (using a semiautomated registration method) by different operators. The additional value of fusion was judged using reports from the original (nonfused) MRI and PET, joint rereading of the volumes side by side, and examination of fused images. Results: Of 12 enhancing lesions on breast MRI, 7 demonstrated uptake on PET/CT. In the 3 supine-only cases, the fused images were not interpretable because of the marked distortion of the breasts. In the 2 prone cases, the fused images increased our confidence in characterizing a lesion as benign or malignant. Interpretations were confirmed by clinical follow up in 2 or histologic results in 3 patients. Conclusions: PET MRI fusion is feasible and may assist in localizing lesions detected on either study. A more extensive study is under-way to confirm the value of this fusion technique.
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| 3. |
- Olivecrona, Lotta, et al.
(författare)
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Standard orientation of the pelvis : Validation on a model and ten patients
- 2005
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Ingår i: Acta Radiologica. - London, UK : Informa Healthcare. - 0284-1851 .- 1600-0455. ; 46:1, s. 74-82
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 4. |
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| 5. |
- Alcala, Yvonne, et al.
(författare)
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Qualifying CT for wrist arthroplasty : Extending techniques for total hip arthroplasty to total wrist arthroplasty
- 2005
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Ingår i: Medical Imaging 2005. - : SPIE - The International Sooceity for Optical Engineeering. - 0819457213 ; , s. 1155-1164
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Konferensbidrag (refereegranskat)abstract
- The purpose of this study was to extend previous work to detect migration of total wrist arthroplasty non-invasively, and with greater accuracy. Two human cadaverous arms, each with a cemented total wrist implant, were used in this study. In one of the arms, I mm tantalum balls were implanted, six in the carpal bones and five in the radius. Five CT scans of each arm were acquired, changing the position of the arm each time to mimic different positions patients might take on repeated examinations. Registration of CT volume data sets was performed using an extensively validated, 3D semi-automatic volume fusion tool in which co-homologous point pairs (landmarks) are chosen on each volume to be registered. Three sets of ten cases each were obtained by placing landmarks on 1) bone only (using only arm one), 2) tantalum implants only, and 3) bone and tantalum implants (both using only arm two). The accuracy of the match was assessed visually in 2D and 3D, and numerically by calculating the distance difference between the actual position of the transformed landmarks and their ideal position (i.e., the reference landmark positions). All cases were matched visually within one width of cortical bone and numerically within one half CT voxel (0.32 mm, p = 0.05). This method matched only the bone/arm and not the prosthetic component per se, thus making it possible to detect prosthetic movement and wear. This method was clinically used for one patient with pain. Loosening of the carpal prosthetic component was accurately detected and this was confirmed at surgery.
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| 6. |
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| 7. |
- Anderlind, Eva, et al.
(författare)
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Will haptic feedback speed up medical imaging? An application to radiation treatment planning
- 2008
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Ingår i: Acta Oncologica. - OSLO, Norge : Taylor & Francis. - 0284-186X .- 1651-226X. ; 47:1, s. 32-37
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Tidskriftsartikel (refereegranskat)abstract
- Haptic technology enables us to incorporate the sense of touch into computer applications, providing an additional input/output channel. The purpose of this study was to examine if haptic feedback can help physicians and other practitioners to interact with medical imaging and treatment planning systems. A haptic application for outlining target areas (a key task in radiation therapy treatment planning) was implemented and then evaluated via a controlled experiment with ten subjects. Even though the sample size was small, and the application only a prototype, results showed that haptic feedback can significantly increase (p0.05) the speed of outlining target volumes and organs at risk. No significant differences were found regarding precision or perceived usability. This promising result warrants further development of a full haptic application for this task. Improvements to the usability of the application as well as to the forces generated have been implemented and an experiment with more subjects is planned.
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| 8. |
- Ericson, Anne, et al.
(författare)
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Fusion of radio stereometric analysis data into computed tomography space : Application to the elbow joint
- 2007
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Ingår i: Journal of Biomechanics. - Oxford, UK : Elsevier Science Ltd. - 0021-9290 .- 1873-2380. ; 40:2, s. 296-304
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Tidskriftsartikel (refereegranskat)abstract
- Improvement of joint prostheses is dependent upon information concerning the biomechanical properties of the joint. Radiostereometric analysis (RSA) and electromagnetic techniques have been applied in previous cadaver and in vivo studies on the elbow joint to provide valuable information concerning joint motion axes. However, such information is limited to mathematically calculated positions of the axes according to an orthogonal coordinate system and is difficult to relate to individual skeletal anatomy. The aim of this study was to evaluate the in vivo application of a new fusion method to provide three-dimensional (31)) visualization of flexion axes according to bony landmarks. In vivo RSA data of the elbow joint's flexion axes was combined with data obtained by 3D computed tomography (CT). Results were obtained from five healthy subjects after one was excluded due to an instable RSA marker. The median error between imported and transformed RSA marker coordinates and those obtained in the CT volume was 0.22mm. Median maximal rotation error after transformation of the rigid RSA body to the CT volume was 0.003 degrees. Points of interception with a plane calculated in the RSA orthogonal coordinate system were imported into the CT volume, facilitating the 3D visualization of the flexion axes. This study demonstrates a successful fusion of RSA and CT data, without significant loss of RSA accuracy. The method could be used for relating individual motion axes to a 3D representation of relevant joint anatomy, thus providing important information for clinical applications such as the development of joint prostheses.
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| 9. |
- Jedenmalm, Anneli, et al.
(författare)
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A new approach for assessment of wear in metal-backed acetabular cups using computed tomography : a phantom study with retrievals
- 2008
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Ingår i: Acta Orthopaedica. - : Medical Journals Sweden AB. - 1745-3674 .- 1745-3682. ; 79:2, s. 218-224
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Tidskriftsartikel (refereegranskat)abstract
- Background and purpose Polyethylene wear is an important cause of aseptic loosening in hip arthroplasty. Detection of significant wear usually happens late on, since available diagnostic techniques are either not sensitive enough or too complicated and expensive for routine use. This study evaluates a new approach for measurement of linear wear of metal-backed acetabular cups using CT as the intended clinically feasible method. Material and methods 8 retrieved uncemented metal-backed acetabular cups were scanned twice ex vivo using CT. The linear penetration depth of the femoral head into the cup was measured in the CT volumes using dedicated software. Landmark points were placed on the CT images of cup and head, and also on a reference plane in order to calculate the wear vector magnitude and angle to one of the axes. A coordinate-measuring machine was used to test the accuracy of the proposed CT method. For this purpose, the head diameters were also measured by both methods. Results Accuracy of the CT method for linear wear measurements was 0.6 nm and wear vector angle was 27 degrees. No systematic difference was found between CT scans. Interpretation This study on explanted acetabular cups shows that CT is capable of reliable measurement of linear wear in acetabular cups at a clinically relevant level of accuracy. It was also possible to use the method for assessment of direction of wear.
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