PubMed · 10149944
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S K Brahme, A C Brower, R Daffner, T L Pope. 1992. Selecting the appropriate imaging modality.. https://pubmed.ncbi.nlm.nih.gov/10149944/
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Preclinical evaluation of a new mobile C-arm image amplifier with an option for three-dimensional computed tomography (CT) imaging (prototype Iso-C3D) with respect to high-contrast resolution and possible clinical applications. Cadaveric specimens (n = 30) of different joints of the lower and upper extremities and specimens of the spinal column were examined with the Iso-C3D and evaluated for image quality. In addition, using a high-contrast phantom (Catphan, Phantom Laboratory, Salem, N.Y., USA) and a fracture model of the femoral bone, measurements of high-contrast resolution were performed in comparison to spiral CT. With the exception of the shoulder, all joint regions including the entire spinal column could be examined. Adequate image quality could be achieved in smaller joints such as the wrist, elbow, ankle, and knee, whereas a remarkably decreased image quality was found when imaging the hip as well as the lumbar and thoracic spine. Images of the phantom study and high-contrast fracture model showed a high-contrast resolution comparable to helical CT (9 Lp/cm in xy-axis). In smaller joints, the image quality of the mobile C-arm CT imaging system (Iso-C3D) is comparable to that of helical CT. Image quality in examinations of the hip and lumbar and thoracic spine seems to be sufficient for intraoperative control studies of osteosynthesis. Problems still occur in shoulder examinations.
A contracture of the elbow joint is a challenge for diagnostic radiology. Radiographs remain the method of choice for primary diagnosis, however, diagnostic confidence can be limited if periarticular ossifications or contracture do not permit evaluation of the whole joint. In these cases, CT or MRI can be used for specific diagnostic problems. Additional multiplanar or three-dimensional reformations can be used by the orthopedic surgeon for planning the surgical procedure. MRI has a great advantage in allowing visualization of muscles, capsula-ligamentous complex and articular cartilage. The main disadvantages are duration of examination time and artifacts. CT is superior in terms of spatial resolution and visualization of bony structures. MRI and CT examinations of the elbow will increase with the number of minimal invasive surgical procedures. Protocols must therefore be optimized with attention to positioning, sequence selection and image processing. This article reviews the current standards of high resolution imaging with CT and MRI, including arthrographic techniques. The pros and cons of both methods are discussed in the setting of a contracture of the elbow joint.
A method for measuring three-dimensional kinematics that incorporates the direct cross-registration of experimental kinematics with anatomic geometry from Computed Tomography (CT) data has been developed. Plexiglas registration blocks were attached to the bones of interest and the specimen was CT scanned. Computer models of the bone surface were developed from the CT image data. Determination of discrete kinematics was accomplished by digitizing three pre-selected contiguous surfaces of each registration block using a three-dimensional point digitization system. Cross-registration of bone surface models from the CT data was accomplished by identifying the registration block surfaces within the CT images. Kinematics measured during a biomechanical experiment were applied to the computer models of the bone surface. The overall accuracy of the method was shown to be at or below the accuracy of the digitization system used. For this experimental application, the accuracy was better than +/-0.1mm for position and 0.1 degrees for orientation for linkage digitization and better than +/-0.2mm and +/-0.2 degrees for CT digitization. Surface models of the radius and ulna were constructed from CT data, as an example application. Kinematics of the bones were measured for simulated forearm rotation. Screw-displacement axis analysis showed 0.1mm (proximal) translation of the radius (with respect to the ulna) from supination to neutral (85.2 degrees rotation) and 1.4mm (proximal) translation from neutral to pronation (65.3 degrees rotation). The motion of the radius with respect to the ulna was displayed using the surface models. This methodology is a useful tool for the measurement and application of rigid-body kinematics to computer models.