Measurement of regional myocardial blood flow with multiple colored microspheres.

Abstract

BACKGROUND The use of radioactive microspheres (RM) for the measurement of regional myocardial blood flow (RMBF) is limited and inaccessible to many investigators due to radiation safety concerns and radioactive waste disposal problems. Therefore, a new method for the measurement of RMBF using colored microspheres (CM) was developed. METHODS AND RESULTS Polystyrene spheres (diameter, 15 +/- 0.1 [SD] micron; density, 1.09 g/ml) were dyed with one of five colors. With the injection of CM into the left atrium or into a coronary perfusion line, RMBF and its distribution can be determined. CM are extracted from the myocardium and blood by digestion with potassium hydroxide and subsequent microfiltration. The dyes are then recovered from the CM within a defined volume of a solvent, and their concentrations are determined by spectrophotometry. The separation of composite absorbance spectra by spectrophotometry with the CM technique was as good as the separation of energy spectra by a gamma-counter using the RM technique. Leaching of dye from the CM was less than 0.1% during a 2-month period in vitro. Significant leaching of dye from the microspheres also did not occur during 8 hours in the blood and myocardium of four anesthetized dogs in vivo. For further validation of this method, pairs of CM and RM (15.5 +/- 0.1 [SD] microns) were simultaneously injected under five different RMBF conditions (range, 0-10 ml/[min.g]) into the left anterior descending coronary artery of four anesthetized pigs, with coronary inflow as a flow reference, or into the left atrium of four anesthetized dogs using aortic blood withdrawal as a reference. The relation between RMBF determined by CM and RM was CM = 0.01 + 1.00.RM (r = 0.98, n = 1,080 data points) in the pigs, and CM = -0.19 + 0.92.RM (r = 0.97, n = 1,813 data points) in the dogs. CONCLUSIONS Measurement of RMBF with CM yields values very similar to those of RM. Their use is less expensive and avoids all the disadvantages related to radioactivity, thus offering an alternative method for as many as five RMBF measurements in a single experiment.

An isolated perfused pig heart model for the development, validation and translation of novel cardiovascular magnetic resonance techniques

“…Graded ischaemia [19], ischaemic preconditioning [20] and the coronary microcirculation [21] have all been studied in different porcine models. In vivo imaging in pig models has previously been used to study coronary blood-flow using coloured microspheres [22], microvascular function using computer tomography (CT) [23], and to validate novel perfusion tracers for positron emission tomography (PET) [24]. Other applications include validation of MR-guided real time coronary catheterization or percutaneous transluminal balloon angioplasty in aortic coarctation [25,26].…”

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).…”

“…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). The X-ray fluorescent microspheres technique uses a measurement system that is expensive and not in common use (Prinzen & Glenny, 1994).…”

“…unit û1 for all muscles (Table 5). discussion Microsphere loss during tissue processing is one of the biggest problems associated with the use of non-radioactive (fluorescent and coloured) microspheres, with both filtration and sedimentation procedures (Hale et al 1988;Kowallik et al 1991;Prinzen & Glenny, 1994;Hakkinen et al 1995;van Oosterhout et al 1995). Although recovery tests were performed in these previous studies, it is not clear whether this varied with stage of processing.…”

Repeat Microsphere Delivery for Serial Measurement of Regional Blood Perfusion in the Chronically Instrumented, Conscious Canine

“…When appropriately sized microspheres are used, RBF is proportional to the number of spheres trapped in the region of tissue of interest [21,22]. Acute, tissue specific studies in small animal models suggest that 15 μm-diameter microspheres do not significantly alter RBF or vascular tone [21,23].…”