Biomedical subjects

D D Robertson

Publications and source records attributed to D D Robertson.

41 records · Page 3Linked to original sources

PubMedDate not supplied

Depiction of pelvic fractures using 3D volumetric holography: comparison of plain X-ray and CT.

OBJECTIVE: The goal of this study was to demonstrate the feasibility and test the diagnostic performance of a new technology, 3D volumetric holography, for imaging pelvic fractures. The management of pelvic fractures may be complex, and advanced imaging studies such as CT are frequently indicated. Multiplanar CT reformations and 3D renderings provide clinically useful and complementary display of the directly acquired CT data. With the recent availability of volumetric multiple exposure holograms, produced from serial image data, it is now possible to produce true 3D images of the pelvis. In the hologram, one may view the CT data in 3D or as individual planar slices constituting the whole 3D pelvis. The diagnostic performance of the volumetric multiple exposure holograms was tested against routine radiography, CT, and 3D volumetric CT reconstructions. MATERIALS AND METHODS: Routine radiography and CT were performed in 15 patients with suspected pelvic fractures. Volumetric multiple exposure holograms and 3D volumetric CT reconstructions were created from the CT data. Axial and multiplanar reformation CT images were used as the standard for fracture, diastasis, and intraarticular fragment detection. RESULTS: Radiograms detected 39 of 50 of the fractures and diastases and no intraarticular fragments. The 3D CT reconstructions and the holograms viewed as 3D objects alone missed two small fractures of the anterior column and one hip with intraarticular bone fragments. When the volumetric multiple exposure holograms were viewed as a 3D object and as individual planar slices constituting the whole, their results were the same as the standard. CONCLUSION: Volumetric multiple exposure holograms were as sensitive and specific as axial CT and multiplanar reformations in detecting fracture pathology. By containing and making available, from one image, both planar and 3D information, volumetric multiple exposure holograms detected subtle anatomical features that were hidden by overlapping structures in the radiographs and the 3D CT images.

Fractures, Bone↗

PubMedDate not supplied

Total hip prosthesis metal-artifact suppression using iterative deblurring reconstruction.

PURPOSE: CT of total joint prostheses is limited by metal artifact produced mainly by missing projection data. Iterative deblurring reconstruction is less sensitive to missing projection data than filtered backprojection. A software CT simulator was used to compare total hip prosthesis images reconstructed using standard filtered backprojection, filtered backprojection after linear interpolation of missing data, and iterative deblurring. METHOD: Unilateral and bilateral total hip replacements with metal-backed or all-polyethylene acetabular prostheses were simulated using bone, metal, and polyethylene annuli and circles of metal and water (soft tissue). Material attenuation properties were taken from the literature. The simulation assumed that no X-rays penetrated the metal. Simulated projection data were reconstructed using filtered backprojection, filtered backprojection after linear interpolation of missing data, and iterative deblurring. Visual observations and objective region-of-interest analyses were made. RESULTS: Even with no X-rays penetrating the metal, iterative deblurring produced almost no visible artifact within the bone or soft tissues. Bone edge detection and sizing were more easily and accurately done from the iterative deblurring images. All reconstruction techniques underestimated bone and water CT attenuation values. Metal artifact was worse for the bilateral or metal-backed prostheses. CONCLUSION: Iterative deblurring generated nearly metal-artifact-free images in this simulation. Filtered backprojection, even after linear interpolation, produced typical clinical metal-artifact images.

Artifacts↗

PubMedDate not supplied

Preoperative description of severe acetabular defects caused by failed total hip replacement.

PURPOSE: The reconstruction of severe acetabular defects, caused by failed hip prostheses, is difficult and complex. Current radiographic descriptions of the defects are inadequate. We sought to more accurately describe remaining bone and improve surgical planning using 3D physical models based on CT data. METHOD: Nineteen patients (20 hips) with failed total hip replacements and severe acetabular defects were selected. Plain radiography and CT were performed. Solid 3D physical models of each pelvis were constructed using the CT data. Bone loss in structurally important regions was measured from radiographs, models, and intraoperative observation. Comparisons were made of the radiograph-based and model-based bone loss measurements, surgical plans, and interobserver variability. RESULTS: There was no statistical difference between the model-based measurements and the intraoperative measurements. Radiographs statistically underestimated bone loss by at least 20% (p < 0.01). Interobserver bone loss grading was poor for the radiograph-based measurements (kappa = 0.06) but was substantial for the model-based measurements (kappa = 0.73). In only half the cases was prosthesis type correctly selected based on radiographs. Model-based planning selected the correct prosthesis type in all cases. CONCLUSION: The physical models were substantially more accurate than radiographs for measuring acetabular defects and for surgical planning.

Acetabulum↗

PubMedDate not supplied

Quantitative bone measurements using x-ray computed tomography with second-order correction.

Two-component cortical bone and water, and trabecular bone and water models were used to study the beam hardening errors associated with computed tomography (CT) bone densitometry and sizing methods. Specimens used included a femur, humerus, radius, ulna, and vertebral bodies. A second-order correction algorithm was employed to improve the accuracy of these quantitative CT methods. Physical measurements of the bones were obtained to verify the CT results. Large discrepancies were found between the uncorrected and second-order corrected CT assessments of cortical bone density, trabecular bone density, water density within the medullary canal, total bone area, medullary canal area, and cortical area. The interosseous lucent streak was also quantitatively studied. Results showed that second-order correction significantly improved the accuracy of CT bone densitometry and sizing methods.

Absorptiometry, Photon↗

PubMedDate not supplied

Assessment of the diabetic foot using spiral computed tomography imaging and plantar pressure measurements: a technical report.

Persons with diabetes mellitus (DM) and peripheral neuropathy are at high risk for skin breakdown due to unnoticed excessive pressures to the plantar foot during walking. We developed methods that combined spiral x-ray computed tomography (SXCT) imaging and plantar pressure analysis to quantify internal foot structure and external pressure during plantar loading. Methods were tested using a subject with DM who had a plantar ulcer, and a healthy control. SXCT measurements were within 2 mm of truth and SXCT plantar recordings were within 6.5% of walking trials. Hammer toe deformity (second toe), severe atrophy of the intrinsic muscles and less contact area during plantar loading, and a peak plantar pressure three times greater at the site of the ulcer were measured in the diabetic foot as compared with the healthy control. This preliminary investigation suggests that these methods are accurate for structural and pressure measurements of diabetic and healthy feet.

Adult↗