Limitations of Quantitative CT in Corticosteroid Induced Osteopenia

Abstract

Single energy spectrum quantitative CT (SES-QCT) was applied for the assessment of the trabecular bone mineral status in patients under long-term corticosteroid treatment. Seventeen renal graft recipients (RGR) and 12 patients receiving corticosteroid treatment for collagen disease were studied. A reduction of about 40% in the spinal trabecular bone density relative to matched controls was found, associated with the corticosteroid administration. Repeated measurements showed significant reduction in density 4 months after transplantation, and an increase in density after graft rejection. Radiologic or clinical evidence of osteopenia in the spine was not found. Other noninvasive techniques, applied in the upper extremities of the RGR, showed only minor bone reduction compared to controls. The findings of the present study suggest that adipose tissue deposition in the spinal trabeculae can introduce errors in the measurements. Therefore, SES-QCT should not be applied during corticosteroid therapy. Key words:Spine; quantitative CT; corticosteroids; osteopenia.Osteopenia is a side effect of corticosteroid administration (16). The term "osteopenia" is used because of the multiple and not completely understood effects of corticosteroids on bone metabolism (1, 9). The influence of corticosteroid administration on spinal bone minerals has not been adequately studied with noninvasive techniques. The usefulness of CT for the assessment of bone mineral status in the spine lies in its ability to provide quantitative data on the vertebral trabecular bone (2, 4, 10, 14, 19). In the present study patients under long-term corticosteroid treatment were examined applying single energy spectrum quantitative CT (SES-QCT). Material and MethodsTwenty-nine patients receiving corticosteroid treatment, divided into 2 groups, were studied. Group A consisted of 12 females (aged 29-65 years, mean 49 years) who received corticosteroids for various collagen diseases (6 for systemic lupus erythematosus, 3 for mixed connective tissue disease, 3 for polyarteritis nodosa). Group B (15 males and 4 females) consisted of patients (aged 21-58 years, mean 42 years) who had undergone renal transplantation up to 17 years earlier (mean time 5.5 years). Among renal graft recipients (RGR) 4 were measured a few days before and 4 months after transplantation. Five RGR with graft rejection and subsequent hemodialysis were measured after withdrawal of the corticosteroid treatment. The rest of the patients were studied by single SES-QCT measurements. Whereas patients in Group A received high doses of corticosteroids (initial dose 50-60 mg/day prednisolone followed by about 20 mg/ day for at least 1 year), patients in Group B received low doses (up to 10 mg/day prednisolone).A modified version of the Cann-Genant single kVp QCT technique (2) was applied for the measurement of the electron density in spinal trabecular bone (19). The trabecular bone equivalent density (TBED) was expressed as the density of a K,HPO, solution that exhibits an identical linea...

An update on the assessment of osteoporosis using radiologic techniques

“…QCT can be performed in single-energy or dual-energy spectrum modes. The accuracy of the single energy spectrum mode is limited by the variable amount of marrow fat, inducing thus a possible underestimation of BMD [36]. On the other hand, dual energy spectrum mode suffers from poor precision and higher radiation dose.…”