Kafka U C M, Beukes P, Slabbert J P, Carstens A
Department of Companion Animal Clinical Studies, University of Pretoria, South Africa.
NRF iThemba LABS, University of the Witwatersrand, South Africa.
J S Afr Vet Assoc. 2024 Dec;95(2):63-70. doi: 10.36303/JSAVA.546. Epub 2024 Aug 29.
The main aim of this pilot study was to determine how the energy spectrum of scatter radiation emitted from horses after injection of the radiopharmaceutical Technetium-methyl diphosphonate (Tc-MDP), changed behind lead shielding of varying thicknesses (0.25 mm, 0.35 mm, and 0.5 mm Pb thickness), and if beam hardening occurred. The effect lead shielding has on the emitted gamma radiation energy spectrum has not been documented. In particular, the presence of beam hardening effects behind lead shielding was investigated, to determine whether or not it could discourage the use of lead shields during bone scintigraphy in horses. Horses were injected intravenously with Tc-MDP, and energy spectra emitted from horses without lead shielding were recorded initially to determine the emitted scatter spectrum. Thereafter, different combinations of lead shields of the various thicknesses listed above, draped over the horse and on simulated personnel, were recorded. The energy spectra were obtained at different anatomical locations of five horses on five consecutive days with a pulse height (multichannel) analyser two and a half hours post-injection. Energy spectra recorded from horses without lead shielding showed polychromatic energy spectra that encompassed a large portion of predominantly lower scatter energies (averaging around the 88-94 keV peaks). Higher Tc- MDP peaks averaging at 139-143 keV (useful for gamma camera acquisition) were consistently seen in all recordings but made up a very small part of the emitted spectra. With the application of lead shielding, peaks of 83-86 keV, which coincided with K-edges of lead, occurred. No significant beam hardening effects behind lead shields of varying thicknesses were observed. Thus, the wearing of lead shields during bone scintigraphy of horses is encouraged.
这项初步研究的主要目的是确定注射放射性药物锝-亚甲基二膦酸盐（Tc-MDP）后，马所发出的散射辐射能谱在不同厚度（0.25毫米、0.35毫米和0.5毫米铅厚度）的铅屏蔽后如何变化，以及是否发生束硬化。铅屏蔽对发出的伽马辐射能谱的影响尚未有文献记载。特别是，研究了铅屏蔽后束硬化效应的存在情况，以确定其是否会阻碍在马的骨闪烁显像中使用铅屏蔽。给马静脉注射Tc-MDP，最初记录无铅屏蔽的马发出的能谱，以确定发出的散射谱。此后，记录上述不同厚度的铅屏蔽以不同组合覆盖在马身上以及模拟人员身上时的情况。在注射后两个半小时，使用脉冲高度（多道）分析仪在连续五天对五匹马的不同解剖位置获取能谱。无铅屏蔽的马记录的能谱显示为多色能谱，其中大部分主要是较低的散射能量（平均在88 - 94 keV峰附近）。在所有记录中均始终能看到平均在139 - 143 keV的较高Tc-MDP峰（对伽马相机采集有用），但在发出的能谱中占比非常小。随着铅屏蔽的应用，出现了与铅的K边缘重合的83 - 86 keV峰。未观察到不同厚度铅屏蔽后有明显的束硬化效应。因此，鼓励在马的骨闪烁显像过程中佩戴铅屏蔽。
