Effects of lead shielding on gamma radiation scatter energy spectrum during equine bone scintigraphy.

The research analyzes how lead shielding impacts the energy spectrum of scatter radiation that is emitted from horses after they have been injected with a radiopharmaceutical, Technectium-methyl diphosphonate (Tc-MDP), during bone scintigraphy. The study found no significant beam hardening effects, leading to the recommendation that lead shields should be used during bone scintigraphy in horses.

Study Objectives and Approach

• The main goal of this research was to explore how the energy spectrum of scatter radiation changes behind lead shielding of different thicknesses (0.25 mm, 0.35 mm, and 0.5 mm) after horses are injected with Tc-MDP.
• The researchers also aimed to document whether beam hardening occurred with the use of lead shielding, and if its presence would advise against using lead shields during bone scintigraphy in horses.

Methodology

• The study used a number of horses, each of which was injected intravenously with the Tc-MDP radiopharmaceutical.
• Energy spectra from the horses were initially recorded without lead shielding to establish the standard scatter spectrum. Following this, the horses and simulated personnel were clothed with lead shields of varying thicknesses and the spectra recorded.
• The energy spectra were collected at different anatomical locations on five horses over five consecutive days, two and a half hours post-injection, using a pulse height (multichannel) analyzer.

Results and Recommendations

• Unshielded horses consistently displayed polychromatic energy spectra that consisted of mainly lower scatter energies, averaging from 88-94 keV.
• The horses also showed minimal but consistent peaks averaging 139-143 keV, useful for gamma camera acquisition, in their emitted spectra.
• With the application of lead shielding, additional peaks from 83-86 keV matching with K-edge energies of lead were observed.
• The main finding of the study was that no significant beam hardening effects were observed behind lead shields of different thicknesses. This therefore encourages the use of lead shields during bone scintigraphy in horses as it does not adversely affect the imaging quality or safety of the procedure.