Biomedical subjects
Publications and source records attributed to H K Genant.
Laboratory tests that are commonly used in the evaluation of rheumatic diseases are described. The techniques for performing these tests; their use in screening, diagnosis, and follow-up; and the pitfalls in interpreting their results are discussed to provide the radiologist with an understanding of the current technology relating to rheumatic disorders.
A method is described for using quantitative computed tomography (CT) to detect subtle skeletal metastases not readily identified or precisely located by conventional methods. Four patients with intramedullary metastases are presented along with data from 13 control subjects. The results indicate that CT may demonstrate intramedullary changes that occur in skeletal metastases and that cannot be detected by other techniques. A difference in medullary CT number greater than 20 HU between limbs is abnormal. This asymmetry, however, is not specific for metastatic disease, and clinical judgment must be exercised in interpreting this finding.
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Computed tomography (CT) provides precise anatomic localization coupled with quantitative x-ray attenuation information that can be used to determine bone mineral content. A precise and sensitive method for vertebral mineral measurement by CT is described and illustrated with results from an ongoing study of mineral loss in oophorectomized women. Spinal mineral loss measured by quantitative CT is compared with peripheral loss determined by photon absorptiometry and radiogrammetry. Vertebral cancellous bone loss was significant for the group as a whole at 12 months, while mean peripheral measurements showed no change. In two subjects in whom mineral change was significant at both sites, spinal loss was approximately five times greater than peripheral loss.
A precise method of measuring vertebral mineral content by computed tomography has been developed. Calibration phantoms scanned with patients are used to provide corrections for machine drifts. Advanced software manipulation of the display images is used to reposition precisely to the midportion of each vertebral body. A long-term precision of 2.8% for mineral content has been obtained in excised vertebrae in a phantom simulating the human torso.
Vertebral mineral loss (measured by computed tomography) was compared to peripheral mineral loss (measured by photon absorptiometry) in immobilized monkeys. Significantly greater loss was found in axial cancallous bone than in peripheral cortical bone. The accuracy of vertebral CT measurements in one animal was determined using direct chemical analysis of excised vertebrae. Results indicate that mineral changes may be detected earlier in the vertebrae by CT than in peripheral bone using photon absorptiometric techniques.
Unilateral osteoarthritis of the functional hand was observed in a 67-year-old monoplegic woman. The contralateral hand with flaccid paralysis was spared. In this and similar cases in the literature, there is apparently some need for neural innervation to an extremity for osteoarthritis to develop.
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Pain after total knee arthroplasty is a common clinical problem in orthopedics, and prosthetic loosening, often requiring surgical revision, is usually the etiology. Since standard clinical and radiographic diagnostic measures have not proven totally satisfactory, a study of the utility of bone scintigraphy to assess stability of the knee prosthesis was done. Thirty-five patients with 39 prostheses were studied. Seventeen patients with 21 total knee arthroplasties served as controls and were asymptomatic, were stable at surgery, or improved with conservative management. Eighteen knees in 18 symptomatic patients composed the experimental group. Of these, 11 knees were loose at surgery and seven have had surgery recommended. Scintigrams of the knees were obtained using 99mTc-MDP, and ranked 0-3 corresponding to increasingly abnormal localization by three observers. Highly significant differences were observed between the abnormal and control groups (p less than 0.001). Reciprocal changes in sensitivity and specificity with increasingly stringent criteria were shown. While it is apparent that the bone scan cannot be used as the sole diagnostic method for evaluation of prosthetic stability, it does seem to be useful adjunct along with clinical criteria and radiographic studies.
To demonstrate the potential impact of computed tomography on orthopaedics, a brief review was done of four generations of scanners and of one new development (assay of bone mineral in the spine) that is presently being researched. To assess the utility of the method in treating orthopaedic problems, the cases of 140 patients, including patients with congenital anomalies, tumors, infections, and traumatic lesions, were analyzed. In the majority of the patients the technique provided useful information, often unobtainable with any other technique.
The role of computed tomography (CT) in the evaluation of fatty tumors of the somatic soft tissues was investigated. Six surgically proven cases of fatty tumors were studied preoperatively by CT and standard radiographic means--conventional radiographs, xeroradiography, and angiography. Our case material included a simple lipoma, two infiltrative lipomas, an angiolipoma, and two liposarcomas. The radiologic-pathologic correlation was evaluated with respect to the various imaging modalities. The unique tissue characteristics of fatty tumors makes them particularly adaptable to CT scanning. In addition to its ability to define accurately tissue densities, the facility of CT in depicting depth, size, and extent of the lesion in the axial plane was found to be most useful in the preoperative evaluation of our case material.
The ability of five low-dose mammographic screen--film systems to portray normal and abnormal breast structures was evaluated in parallel with a study of physical image properties. Single-blind evaluations of the visibility of normal breast architecture, mass lesions, and calcifications were made on the mammograms of 100 patients radiographed with each of the systems. There was increased noise and slightly poorer resolution for the faster recording systems, but there was no difference in final diagnostic impressions among the five systems. These results suggest that the faster systems will result in substantial dose reduction without sacrificing diagnostic accuracy.
A retrospective study was performed to determine the accuracy of 99mTc-methylene diphosphonate bone imaging in the evaluation of total hip arthrosplasty for lossening and/or infection. Using focally increased activity at the tip of the femoral component or in the region of the acetabular component as a criterion, the examination was 77% specific and 100% sensitive for loosening and/or infection. A possible explanation for the increased uptake at the tip of the femoral component and the role of this examination in the management of a painful total hip prosthesis are discussed.
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Avascular necrosis (AN) of bone developed in 11 of 100 children who received renal transplants from 1964 to 1977. Bones involved were femoral heads, 14; femoral condyles, 12; tall, two; and carpal naviculars, two. Seven children with symptomatic AN of the femoral heads were treated with limited weight bearing; three subsequently required arthroplasty, and degenerative joint disease developed in one. The AN at other joints healed clinically but not roentgenographically. Although the prevalence of AN decreased after 1967 coincident with a decrease in prednisone dose, children with AN received the same cumulative prednisone dose as children in a control group. Serum phosphorus levels were different in the AN and control groups, but other indexes of hyperparathyroidism were similar. The relative contributions of prednisone therapy and hyperparathyroidism to the development of AN could not be delineated.
The ration of late to early uptake of several radionuclides was examined as a method for distinguishing states of abnormal bone metabolism. Nutritional osteoporosis (secondary hyperparathyroidism) and osteomalacia were produced in young rats and compared to a control group. The ratio of early (3-6 hrs.) to late (4-6 days) uptake of barium-131, nitrate, indium-111 EDTMP, and lead-203 were studied, as was that of strontium-85 chloride, a calcium analogue. Ratios of late to early uptake were found to distinguish osteomalacia from osteoporosis in the models when strontium-85 or barium-131 were used. Barium-131 may be a clinically useful alternative to strontium-85 in the evaluation of metabolic bone disease due to its shorter half-life and lower radiation dose.
The association between histo-compatibility antigens and disease is reviewed, in particular that between HLA-B27 and spondylitic disorders, i.e., ankylosing spondylitis, Reiter's arthritis, psoriatic arthritis, and ankylosing hyperostosis. We determined whether the presence of HLA-B27 predicted specific radiographic findings and, conversely, whether specific radiographic changes predicted antigenic status. The prevalences of the HLA-B27 antigen in our patients were: ankylosing spondylitis, 100%; Reiter's arthritis, 93%; psoriatic arthritis, 55%; and ankylosing hyperostosis, 12%. The only specific radiographic finding associated with B27 positivity was severe spondylitis in psoriasis.