New nonradioactive microspheres and more sensitive X-ray fluorescence to measure regional blood flow

Abstract

We developed new nonradioactive microspheres and used more sensitive X-ray fluorescence spectrometers than used previously to measure regional blood flow in the heart and other organs. We demonstrated the chemical stability of eight kinds of heavy element-loaded microspheres and validated their use for regional blood flow measurement by comparing duplicate flows measured with radioactive and/or nonradioactive microspheres in both acute and chronic dog experiments. The wavelength-dispersive spectrometer (Philips PW 1480) has a higher sensitivity than the previously described X-ray fluorescent system and reduced the number of microspheres required for accurate measurement. The fine energy resolution of this system makes it possible to increase the numbers of different kinds of microspheres to be quantitated, but at present only eight kinds are available. We also used a synchrotron radiation-excited energy dispersive spectrometer. The monochromatic synchrotron radiation allowed us to obtain much higher signal-to-background ratios of X-ray fluorescence spectra than with the wavelength-dispersive system (50 dB more for Zr-loaded microspheres) and will enable analysis of fluorescent activity in smaller regions (< 20 mg) than the radioactive method does.

Development of the Fluorescent Microsphere Technique for Quantifying Regional Blood Flow in Small Mammals

“…A number of non-radioactive alternatives have been proposed, including coloured microspheres (Hale et al 1988;Kowallik et al 1991;Hakkinen et al 1995;Degens et al 1996) and X-ray fluorescent microspheres (Morita et al 1990;Mori et al 1992), although they have been shown to have some disadvantages. For example, coloured microspheres may underestimate RBF, since they have limited resolution due to significant spectral overlap among different colours, while data variance is high as a result of the low signal intensity (Hale et al 1988;Kowallik et al 1991;Prinzen & Glenny, 1994;Degens et al 1996).…”

Edaravone Preserves Coronary Microvascular Endothelial Function After Ischemia/Reperfusion on the Beating Canine Heart In Vivo

“…To confirm infarct size reduction by edaravone in relation to the effect of collateral flow, regional MBF was assessed by non-radioactive microspheres (Sekisui Plastic Co., Ltd., Tokyo), as previously described (17). Briefly, 1 ml of the microsphere suspension (2 to 4 × 10 6 spheres) was injected into the left atrium 85 min after the onset of coronary occlusion.…”

β-Adrenoceptor Blocker Carvedilol Provides Cardioprotection via an Adenosine-Dependent Mechanism in Ischemic Canine Hearts

“…17 Nonradioactive microspheres (Sekisui Plastic Co) made of inert plastic were labeled with bromine. Microspheres were administered at 80 minutes after the start of coronary occlusion.…”