The effect of 99mTc on dual-energy X-ray absorptiometry measurement of body composition and bone mineral density.

Whether the γ-emission by radioisotopes influences the outcome of dual-energy X-ray absorptiometry (DXA) measurements is not fully elucidated. The aim of this study was to evaluate the effect of antecedent administration of 99mTc on DXA measurements regarding body composition and bone mineral density (BMD) using a K-edge filter scanner. The phantom measurements were performed by placing a urinary bladder phantom containing 40 mL of radioisotope solution on the pelvic region of a whole-body phantom. Twenty-seven patients attending our department for a routine examination involving the administration of a tracer marked with 99mTc were included. The patients underwent a whole-body DXA scan before and within 2 h after tracer injection using a GE/Lunar Prodigy scanner. Control scans were performed on 40 volunteers, who had not received any radioactive tracer. In both phantom and patient measurements, we found a significant dose-related decrease in fat mass and BMD and a corresponding increase in fat-free mass (p < 0.001). Based on the linear regression analysis, we suggest upper dose limits for the measurement of BMD at 0.77 µSv/h and body composition at 0.21 µSv/h (dose rate measured at a distance of 1m from the patient). Caution should be taken when interpreting the results of DXA scans performed in close temporal proximity to procedures involving the administration of 99mTc.

Nephrogenic systemic fibrosis: suspected causative role of gadodiamide used for contrast-enhanced magnetic resonance imaging.

Nephrogenic systemic fibrosis is a new, rare disease of unknown cause that affects patients with renal failure. Single cases led to the suspicion of a causative role of gadodiamide that is used for magnetic resonance imaging. This study therefore reviewed all of the authors' confirmed cases of nephrogenic systemic fibrosis (n = 13) with respect to clinical characteristics, gadodiamide exposure, and subsequent clinical course. It was found that all had been exposed to gadodiamide before the development of nephrogenic systemic fibrosis. The delay from exposure to first sign of the disease was 2 to 75 d (median 25 d). Odds ratio for acquiring the disease when gadodiamide exposed was 32.5 (95% confidence interval 1.9 to 549.2; P < 0.0001). Seven (54%) patients became severely disabled, and one died 21 mo after exposure. No other exposure/event than gadodiamide that was common to more than a minority of the patients could be identified. These findings indicate that gadodiamide plays a causative role in nephrogenic systemic fibrosis.