A Protocol for Improved Measurement of Arterial Flow Rate in Preclinical Ultrasound

Abstract

Purpose:

To describe a protocol for the measurement of blood flow rate in small animals and to compare flow rate measurements against measurements made using a transit time flowmeter.

Materials and Methods:

Measurements were made in rat and mice using a Visualsonics Vevo 770 scanner. The flow rate in carotid and femoral arteries was calculated from the time-average maximum velocity and vessel diameter. A correction factor was applied to correct for the overestimation of velocity arising from geometric spectral broadening. Invasive flow rate measurements were made using a Transonics system.

Results:

Measurements were achieved in rat carotid and femoral arteries and in mouse carotid arteries. Image quality in the mouse femoral artery was too poor to obtain diameter measurements. The applied correction factor in practice was 0.71–0.77. The diameter varied by 6–18% during the cardiac cycle. There was no overall difference in the flow rate measured using ultrasound and using transit-time flowmeters. The flow rates were comparable with those previously reported in the literature. There was wide variation in flow rates in the same artery in individual animals. Transit-time measurements were associated with changes of a factor of 10 during the typical 40 min measurement period, associated with probe movement, vessel spasm, vessel kinking and other effects.

Conclusion:

A protocol for the measurement of flow rate in arteries in small animals has been described and successfully used in rat carotid and femoral arteries and in mouse carotid arteries. The availability of a noninvasive procedure for flow rate measurement avoids the problems with changes in flow associated with an invasive procedure.

Key words

ultrasound Doppler - technical aspects - flow rate - blood velocity - preclinical

• References

• 1 D’Almeida MS, Cailmail S, Lebrec D. Validation of transit-time ultrasound flow probes to directly measure portal blood flow in conscious rats. Am J Physiol – Heart Circ Physiol 1996; 271: H2701-H2709
• 2 Beldi G, Bosshard A, Hess OM et al. Transit time flow measurement: experimental validation and comparison of three different systems. Ann Thorac Surg 2000; 70: 212-217
• 3 Kagadis GC, Loudos G, Katsanos K et al. In vivo small animal imaging: Current status and future prospects. Med Phys 2010; 37: 6421-6442
• 4 Foster FS, Zhang MY, Zhou YQ et al. A new ultrasound instrument for in vivo microimaging of mice. Ultrasound Med Biol 2002; 28: 1165-1172
• 5 Foster FS, Mehi J, Lukacs M et al. A new 15–50 MHz array-based micro-ultrasound scanner for preclinical imaging. Ultrasound Med Biol 2009; 35: 1700-1708
• 6 Hoskins PR. Measurement of blood velocity, volumetric flow and wall shear rate. Ultrasound 2011; 19: 120-129
• 7 Evans DH, McDicken WN. Doppler ultrasound: physics, instrumentation and signal processing. Chichester: Wiley; 2000
• 8 Evans DH. On the measurement of the mean velocity of blood flow over the cardiac cycle using Doppler ultrasound. Ultrasound Med Biol 1985; 11: 735-741
• 9 Li SF, Hoskins PR, Anderson T et al. Measurement of mean velocity during pulsatile flow using time averaged maximum frequency of Doppler ultrasound waveforms. Ultrasound Med Biol 1993; 19: 105-113
• 10 Daigle RJ, Stavros AT, Lee RM. Overestimation of velocity and frequency values by multi-element linear array Dopplers. J Vasc Technol 1990; 14: 206-213
• 11 Hoskins PR, Li SL, McDicken WN. Velocity estimation using duplex scanners. Ultrasound Med Biol 1991; 17: 195-199
• 12 Thrush AJ, Evans DH. Intrinsic spectral broadening: a potential cause of misdiagnosis of carotid artery disease. J Vasc Invest 1995; 1: 187-192
• 13 Hoskins PR. Accuracy of maximum velocity estimates made using Doppler ultrasound systems. Br J Radiol 1996; 69: 172-177
• 14 Newhouse VL, Furgason ES, Johnson GF et al. The dependence of ultrasound Doppler bandwidth on beam geometry. IEEE Trans Sonics Ultrasonics 1980; 27: 50-59
• 15 Yang X, Anderson T, Moran CM et al. Assessment of spectral Doppler in preclinical ultrasound using a small-size rotating phantom. Ultrasound Med Biol 2013; 39: 1491-1499
• 16 Kenwright DA, Anderson T, Moran CM et al. Assessment of spectral Doppler for an array-based preclinical ultrasound scanner using a rotating phantom. Ultrasound Med Biol 2015;
• 17 Drost CJ. Vessel diameter-independent volume flow measurements using ultrasound. Proc San Diego Bioml Symp 1978; 17: 299-302
• 18 Kubo-Inoue M, Egashira K, Usui M et al. Long-term inhibition of nitric oxide synthesis increases arterial thrombogenecity in rat carotid artery. Am J Physiol Heart Circ Physiol 2002; 282: H1478-H1484
• 19 Basu P, Sen U, Tyagi N et al. Blood flow interplays with elastin: collagen and MMP: TIMP ratios to maintain healthy vascular structure and function. Vasc Health Risk Manag 2010; 15: 215-228
• 20 Mondy JS, Lindner V, Miyashiro JK et al. Platelet-derived growth factor ligand and receptor expression in response to altered blood flow in vivo. Circ Res 1997; 81: 320-327
• 21 Hoffman A, Grossman E, Ohman KP et al. Endothelin induces an initial increase in cardiac output associated with selective vasodilation in rats. Life Sci 1989; 45: 249-255
• 22 Rickard RF, Wilson J, Hudson DA. Characterization of a rodent model for the study of arterial microanastomoses with size discrepancy (small-to-large). Lab Anim 2009; 43: 350-356
• 23 Lundberg G, Luo F, Blegen H et al. A rat model for severe limb ischemia at rest. Eur Surg Res 2003; 35: 430-438
• 24 Ota R, Kurihara C, Tsou TL et al. Roles of matrix metalloproteinases in flow-induced outward vascular remodeling. J Cereb Blood Flow Metab 2009; 29: 1547-1458
• 25 Wilson KM, Lynch CM, Faraci FM et al. Effect of mechanical ventilation on carotid artery thrombosis induced by photochemical injury in mice. J Thromb Haemost 2003; 1: 2669-2674
• 26 Dörffler-Melly J, de Kruif M, Schwarte LA et al. Functional thrombomodulin deficiency causes enhanced thrombus growth in a murine model of carotid artery thrombosis. Basic Res Cardiol 2003; 98: 347-352
• 27 Bryant SR, Bjercke RJ, Erichsen DA et al. Vascular remodeling in response to altered blood flow is mediated by fibroblast growth factor-2. Circ Res 1999; 84: 323-328
• 28 Rudic RD, Bucci M, Fulton D et al. Temporal events underlying arterial remodeling after chronic flow reduction in mice: correlation of structural changes with a deficit in basal nitric oxide synthesis. Circ Res 2000; 86: 1160-1166