Archive for the ‘Main’ Category

MR also has been used to measure structural parameters in animal models of osteoporosis. Jiang et al. treated an ovariec- tomized sheep model of osteoporosis with salmon calcitonin, an osteoclast inhibitor, to determine if structural parameters in the neck of the femur could be maintained. It was found that BV/TV and Tb.N decreased and Tb.Sp […]

Several studies have explored how MR images compare with other imaging modalities in determining structural parameters (Table I). Hipp et al. and Hopper et al. used small-bore MRI with resolutions of 92x92x92 |im3 and 23x23x39 |im3 respec­tively. All other studies were performed on 1.5 or 3T scanners with in-plane resolution of 100-150 mm and a […]

Bone mineral density and trabecular structure together deter­mine the mechanical strength of trabecular bone. The main ob­jective of imaging trabecular bone structure is to determine morphological parameters of the trabecular architecture. These morphologic parameters may help to determine the efficacy of therapeutic treatments for osteoporosis and predict individuals at risk for bone fracture. Standard histomorphometric […]

After obtaining an MR image, pre-processing of the image is usually required in order to improve the signal-to-noise ratio and image quality and make it possible to differentiate marrow from bone trabeculae. Pre-processing may include coil correc­tion, noise reduction, motion correction, and thresholding. Coil correction is required to correct spatial variations in the sensi­tivity of […]

MRI basics Nuclei with an odd number of protons and neutrons (such as hydrogen) have a magnetic moment causing the nucleus to act like a small magnet in the presence of an external magnetic field. The magnetic field of the nucleus aligns in the direction of the external magnetic field. Magnetic resonance imaging uses radio […]

Introduction Osteoporosis is a metabolic disorder that results in a decrease in bone mineral density and an alteration in the trabecular ar­chitectural structure. Osteoporotic bone has decreased me­chanical strength making it prone to fracture, especially atrau­matic vertebral fractures and fall-related hip and radius frac­tures. Osteoporosis is clinically diagnosed using measurement of bone mineral density. Bone […]

Other maneuvers during both CV and HFV can be potentially helpful in patients with BPF. Selective intubation and CV of the unaffected lung in patients with a unilateral BPF may be useful but will predispose to the collapse of the nonintubated lung. The use of differential lung ventilation with CV may be of benefit in […]