Taylor G A, Hudak M L
Department of Radiology, Johns Hopkins Medical Institutions, Baltimore, Maryland 21205.
Invest Radiol. 1994 Feb;29(2):188-94. doi: 10.1097/00004424-199402000-00013.
The relationship between changes in small vessel diameter as determined by arteriography and those estimated by color Doppler ultrasound were tested. These techniques were used to examine the effects of acute isovolemic anemia on cerebral blood flow and small vessel diameter in the newborn lamb.
Validation of Doppler measurements was obtained in two lambs. Color Doppler diameter estimates of the anterior tibial artery (1-2 mm) were compared with simultaneous arteriographic measurements during vasodilatation and vasoconstriction effected by intra-arterial infusions of papaverine and norepinephrine, respectively. Acute anemia was produced in five newborn lambs by serial isovolemic exchange transfusions with adult sheep plasma. Doppler estimates of intracranial vessel diameter and mean blood flow velocity were correlated with simultaneous cerebral blood flow (CBF) determinations corrected for cerebral oxygen consumption (CBF/CMRO2).
In the anterior tibial artery, color Doppler measurements of vessel diameter correlated well with arteriographic measurements (r2 = .77, P = .001), but overestimated the absolute vessel diameter by 10% to 27%. Hemodilution resulted in significant increases in CBF/CMRO2 (r2 = .61, P = .001), and estimated diameter of small cerebral arteries (r2 = .93, P = .001). Percent change in mean blood flow velocity correlated well with changes in CBF/CMRO2, but underestimated true changes in blood flow by approximately 40% (r2 = .93, P = .0001). Conversely, changes in Doppler volume flow overestimated true change in flow by approximately 50% (r2 = .84, P = .0001).
Under certain physiological conditions, small cerebral arteries may make an important contribution to the overall regulation of CBF. Doppler estimates of relative flow and vessel diameter correlate well with true changes in CBF and small vessel diameter.
检测了通过动脉造影确定的小血管直径变化与通过彩色多普勒超声估计的小血管直径变化之间的关系。这些技术被用于研究急性等容性贫血对新生羔羊脑血流量和小血管直径的影响。
在两只羔羊中对多普勒测量进行了验证。将胫前动脉（1 - 2毫米）的彩色多普勒直径估计值与分别通过动脉内输注罂粟碱和去甲肾上腺素引起血管舒张和收缩时的同步动脉造影测量值进行比较。通过与成年绵羊血浆进行系列等容性交换输血，在五只新生羔羊中造成急性贫血。颅内血管直径和平均血流速度的多普勒估计值与同时进行的经脑氧耗量校正的脑血流量（CBF）测定值（CBF/CMRO2）相关。
在胫前动脉中，血管直径的彩色多普勒测量值与动脉造影测量值相关性良好（r2 = 0.77，P = 0.001），但绝对血管直径高估了10%至27%。血液稀释导致CBF/CMRO2显著增加（r2 = 0.61，P = 0.001），以及小脑动脉估计直径增加（r2 = 0.93，P = 0.001）。平均血流速度的百分比变化与CBF/CMRO2的变化相关性良好，但血流真实变化低估了约40%（r2 = 0.93，P = 0.0001）。相反，多普勒容积流量变化高估了血流真实变化约50%（r2 = 0.84，P = 0.0001）。
在某些生理条件下，小脑动脉可能对脑血流量的整体调节起重要作用。多普勒对相对血流和血管直径的估计与脑血流量和小血管直径的真实变化相关性良好。
