Bone mineral density in Iranian adolescents and young adults with beta-thalassemia major.

The authors investigated the prevalence of low bone mass in patients from Tehran, Iran, with beta-thalassemia major (n = 203), aged 10-20 years, and the potential risk factors for osteoporosis in this patient population. Prevalence of osteoporosis was 50.7% in lumbar spine, 10.8% in femur, and 7.9% in both regions with no significant difference between the two genders. The following factors were associated with low BMD: height for age and weight for age below 3rd percentile, delayed puberty or hypogonadism, age when Desferal (for iron chelation) was started, duration of Desferal therapy, and serum zinc. Low serum copper and 25(OH)D were not associated with low BMD.

The new SQUID biosusceptometer at Oakland: first year of experience.

Liver iron measurements using biosusceptometers have been validated on two low-TC SQUID (Superconducting Quantum Interference Device) systems (New York and Hamburg) built in the 1980's. Recently, two new instruments have been installed in Torino, Italy (2001), and Oakland, California (2003). The design of the Oakland system is similar to those in Hamburg and Torino. Improvements were made to adjust for significant environmental noise, moreover, an active electronic noise cancellation, a computer controlled water coupling reference system using a pressure feedback and a faster data acquisition system using software lockin amplifiers have been implemented. All 3 systems (Hamburg, Torino, Oakland) are using the same standardized operational protocol. Presented herein are the data collected from 276 patients measured with the SQUID biosusceptometer at Oakland since installation. The results from 149 patients with beta-thalassemia (beta-Thal, age: 2-66 y), 76 patients with sickle-cell disease (SCD, age: 5-55 y), 35 patients with various rare diseases (RD, age: 2-80 y), and 16 patients with hereditary hemochromatosis (HHC, age: 6-74 y) are reported. The liver iron concentration in the different groups are 222 - 7570 (beta-Thal), 518 - 7918 (SCD), 511 - 6234 (RD), 258 - 2041 (HHC) microg/g-liver (in vivo wet weight). The long-term reproducibility (12 months) in a patient on constant treatment regimen demonstrated a mean liver iron of 1141 +/- 133 microg/g-liver. The new SQUID Ferritometer located on the US West coast will give more patients access to this non-invasive liver iron assessment.

Interaction of artificial metallic objects with biosusceptometric measurements.

In human subjects, metallic objects cause distortions of the magnetic fields used by magnetic resonance imaging (0.5 - 3.0 T) or by SQUID biomagnetic liver susceptometry (0.1 - 30 mT) and may lead to artifacts in the measurement of the relaxation rate or the magnetic susceptibility. In biosusceptometry, the measured signal will depend not only on the magnetic susceptibility of the object, but also on its distance to the sensor assembly, and in case of ferromagnetic objects, on the direction of its remanent field. The magnetic susceptibility of a vascular access port-a-cath and of surgical clips have been measured by a SQUID biosusceptometer. Additionally, the impact from port-a-caths and dental braces on liver iron concentration (LIC) measurements was measured in vivo with respect to their radial distance from the gradiometer center axis. For the port-a-cath, a mean magnetic volume susceptibility of (83.5 +/- 0.3).10(-6) SI-units was found, which may be compared with the magnetic susceptibility of titanium at room temperature of (180 +/- 2).10(-6) SI demonstrating the absence of ferromagnetic contamination. At a radial distance of 5 cm from the gradiometer center axis, the voltage amplitude is similar to the signal generated by a normal liver. Modern surgical clips have nearly no impact on LIC measurements. However, dental braces although further away from the center axis, often superimpose the signal even from an iron overloaded liver. Depending on the Ni-content, these objects reveal ferromagnetic properties and contribute in first order with a one parameter reciprocal distance function to the measured liver iron signal.