PMID- 11381162
OWN - NLM
STAT- MEDLINE
DCOM- 20010705
LR  - 20161124
IS  - 0006-355X (Print)
IS  - 0006-355X (Linking)
VI  - 38
IP  - 1
DP  - 2001
TI  - The "black hole" phenomenon in ultrasonic backscattering measurement under 
      pulsatile flow with porcine whole blood in a rigid tube.
PG  - 15-26
AB  - The "black hole" phenomenon was further investigated with porcine whole blood 
      under pulsatile flow conditions in a straight rigid tube 120 cm long and of 0.95 
      cm diameter. A modified Aloka 280 commercial scanner with a 7.5 MHz linear array 
      was used to collect the radio frequency (RF) signal of backscattering echoes from 
      the blood inside the tube. The transducer was located downstream from the 
      entrance and parallel to the longitudinal direction of the tube. The experimental 
      results showed that higher hematocrits enhanced the black hole phenomenon, 
      leading to a more apparent and larger diameter black hole. The black hole was not 
      apparent at hematocrits below 23%. The highest hematocrit used in the experiment 
      was 60%. Beat rates of 20, 40 and 60 beats per minute (bpm) were used, and the 
      black hole became weaker in amplitude and smaller in diameter when the peak flow 
      velocity was increased at each beat rate. These results are consistent with the 
      suggestion in previous work that the black hole arises from insufficient 
      aggregation of red blood cells (RBCs) at the center of the tube because of the 
      low shear rate. At 20 and 40 bpm, the peak flow velocity ranges were 10 
      approximately 25 cm/s and 18 approximately 27 cm/s, respectively. The black hole 
      was very clear at the minimal peak flow velocity but almost disappeared at the 
      maximal velocities for each beat rate. At 60 bpm, experiments were only performed 
      at one peak flow velocity of 31 cm/s and the black hole was clear. The results 
      showed that the black hole was more pronounced at higher beat rates when the peak 
      velocity was the same. This phenomenon cannot be explained by previous 
      hypotheses. Acceleration seems to be the only flow parameter that varies at 
      different beat rates when peak velocities are the same. Therefore, the influence 
      of acceleration on the structural organization and orientation of RBC rouleaux 
      might be another factor involved in the formation of the black hole in addition 
      to the shear rate. As the entrance length was changed from 110 to 15 diameters 
      (D) in seven steps at the hematocrit of 60%, it was found that a position farther 
      downstream yielded a black hole with a greater contrast relative to the 
      surrounding region, while the backscattering power at the central hypoechoic zone 
      did not increase with increasing entrance length.
FAU - Cao, P J
AU  - Cao PJ
AD  - Department of Bioengineering, Pennsylvania, University Park, PA 16802, USA. 
      pjcao@psu.edu
FAU - Paeng, D G
AU  - Paeng DG
FAU - Shung, K K
AU  - Shung KK
LA  - eng
GR  - HL 28452/HL/NHLBI NIH HHS/United States
PT  - Journal Article
PT  - Research Support, U.S. Gov't, P.H.S.
PL  - Netherlands
TA  - Biorheology
JT  - Biorheology
JID - 0372526
SB  - IM
MH  - Animals
MH  - Blood/*diagnostic imaging
MH  - Blood Flow Velocity/physiology
MH  - Erythrocyte Aggregation/physiology
MH  - Hematocrit
MH  - Pulsatile Flow/*physiology
MH  - Swine
MH  - Ultrasonography
EDAT- 2001/05/31 10:00
MHDA- 2001/07/06 10:01
CRDT- 2001/05/31 10:00
PHST- 2001/05/31 10:00 [pubmed]
PHST- 2001/07/06 10:01 [medline]
PHST- 2001/05/31 10:00 [entrez]
PST - ppublish
SO  - Biorheology. 2001;38(1):15-26.