Dual photon absorptiometry using a gadolinium-153 source applied to measure equine bone mineral content.

The research paper presents the application of a method known as dual photon absorptiometry (DPA) with a gadolinium-153 source, utilized to measure the bone mineral density (BMD) in the third metacarpal bone of horses.

Overview of the Method

• The authors leveraged dual photon absorptiometry (DPA), a non-invasive technique frequently used to measure bone mineral density in humans. In this case, however, they applied it for the same purpose but in horses. Especially, they focused on the third metacarpal bone.
• The DPA technique implemented gadolinium-153 as the photon source. Gadolinium-153 releases two different energy gamma photons, which are used in the DPA for calculating bone mineral density.
• The radiation detector used a NaI(Tl) scintillator attached to a 14-stage photomultiplier. A photomultiplier is a highly sensitive detector of light in the ultraviolet, visible, and near-infrared spectra, thus used here to detect the photons released by the gadolinium-153 source.

Application of the Method

• To ensure flexible and precise use, a modular mechanical system was developed to adjust the position of the setup with relation to the animal.
• A moveable carrier allows the metacarpal to be scanned at variable speeds, ranging from 1 to 12 mm per second, ensuring accurate coverage of a total distance of 250 mm.

Testing and Evaluation of the Method

• Initial testing was accomplished using a phantom model of the third metacarpal bone made up of perspex and aluminium.
• Later, this method was also tested in vitro on a real transverse slice of a horse’s third metacarpal bone.
• Test results elucidated that the prototype had a fairly good accuracy and precision rate, i.e., approximately 10% and 6% respectively for a 6-second acquisition time.

Application on Live Animals

• Preliminary studies were conducted on three foals from birth to one year of age, indicating that the prototype was suitable for in vivo and in situ analysis of bone mineral density.
• The method made it feasible to monitor the monthly changes in BMD levels of the horses’ third metacarpal bone.
• Moreover, these studies suggested an exponential growth pattern of the BMD in the horses’ bones during the first year of life.

Significance of the Findings

• The use of DPA with a gadolinium-153 source created a new and efficient precedent for diving deeper into veterinary orthopedic studies, specifically in horses.
• This development has significant potential in regular monitoring of bone mineral density in horses, aiding in the detection and management of orthopedic diseases.