Apparatus for hematocrit determination and method for its use

• US 20040054283A1
• Filed: 08/28/2002
• Published: 03/18/2004
• Est. Priority Date: 08/28/2002
• Status: Active Grant

• Current Assignee: Separation Technology, Inc.
• Original Assignee: Separation Technology, Inc.
• Inventors: Lipford, Keith, Murphy, Brian, Corey, Scott, Reed, Samuel, Sakers, John
• Granted Patent: US 7,838,296 B2
• Time in Patent Office: Days
• US Class Current: 600/438
• CPC Class Codes: G01H 5/00 Measuring propagation velocity of ultrasonic, sonic or infrasonic waves , e.g. of pressure waves
• CPC Class Codes: G01N 2291/02466 Biological material, e.g. blood
• CPC Class Codes: G01N 2291/02881 Temperature
• CPC Class Codes: G01N 29/024 by measuring propagation velocity or propagation time of acoustic waves
• CPC Class Codes: G01N 29/032 by measuring attenuation of acoustic waves
• CPC Class Codes: G01N 33/491 by separating the blood components G01N15/05 takes precedence
• CPC Class Codes: Y10T 436/101666 Particle count or volume standard or control [e.g., platelet count standards, etc.]

Abstract

The present invention provides an apparatus and method for measuring the properties of blood using ultrasound. The present invention is particularly suitable for measuring HCT, HGB, MCV, RBC, MCHC, MCH or TPC of blood.

Claims

1. An apparatus for measuring one or more of HCT, HGB, MCV, RBC, MCHC, or MCH of blood, comprising:

a means for holding a blood sample;

a means for sending one or more ultrasonic signals into said blood sample;

a means for receiving one or more ultrasonic signals from said blood sample; and

a means for determining at least one property selected from the group consisting of HCT, HGB, MCV, RBC, MCHC, MCH, and combinations thereof, of the blood.

2. The apparatus of claim 1, wherein the blood sample comprises 1 mL or less of blood.

3. The apparatus of claim 1, wherein the received ultrasonic signal comprises at least one selected from the group consisting of signals received from two or more acoustic paths, signals received from more than one reflective interface, and a combination thereof.

4. The apparatus of claim 3, wherein said signals are used in combination to eliminate one or more delays or transit times through one or more other materials from the calculation of transit time through blood.

5. The apparatus of claim 1, wherein the means for determining comprises measuring a combination of least two characteristics selected from the group consisting of speed of sound, attenuation, backscatter, continuous wave excitation, frequency response, refraction angle, phase, amplitude, and acoustic impedance to eliminate at least one unknown variable.

6. The apparatus of claim 5, wherein the unknown variable is selected from the group consisting of a distance the ultrasound travels in blood, a temperature of the blood, and a combination thereof.

7. The apparatus of claim 1, wherein the means for receiving comprises a means for receiving one or more ultrasonic signal reflections.

8. The apparatus of claim 1, comprising at least one stepped reflector which returns multiple ultrasonic signal reflections.

9. The apparatus of claim 1, comprising at least one movable reflector.

10. The apparatus of claim 1, wherein the apparatus or chamber comprises a material with a speed of sound matched to the speed of sound in blood.

11. The apparatus of claim 10, wherein the material has a speed of sound ranging from 1000 m/s to 2500 m/s.

12. The apparatus of claim 1, wherein the blood is diluted to achieve a monotonic correlation between backscatter and at least one of the properties.

13. The apparatus of claim 1, wherein the blood sample is comprised within the body of a subject.

14. A method for measuring one or more of HCT, HGB, MCV, RBC, MCHC, or MCH of blood, comprising:

sending one or more ultrasonic signals into blood;

measuring at least one ultrasonic signal received from the blood; and

determining at least one property selected from the group consisting of HCT, HGB, MCV, RBC, MCHC MCH, and combinations thereof of the blood.

15. The method of claim 14, wherein the blood is comprised within a blood sample of 1 mL or less.

16. The method of claim 14, wherein the received ultrasonic signal comprises at least one selected from the group consisting of signals received from two or more acoustic paths, signals received from more than one reflective interface, and a combination thereof.

17. The method of claim 16, wherein said signals are used in combination to eliminate one or more delays or transit times through one or more other materials from the calculation of transit time through blood.

18. The method of claim 14, wherein the measuring comprises measuring a combination of least two characteristics selected from the group consisting of speed of sound, attenuation, backscatter, continuous wave excitation, frequency response, refraction angle, phase, amplitude, and acoustic impedance to eliminate at least one unknown variable.

19. The method of claim 18, wherein the unknown variable is selected from the group consisting of a distance the ultrasound travels in blood, a temperature of the blood, and a combination thereof.

20. The method of claim 14, wherein one or more ultrasonic signal reflections are measured.

21. The method of claim 14, wherein the received ultrasonic signal arises from at least one stepped reflector which returns multiple ultrasonic signal reflections.

22. The method of claim 14, wherein the received ultrasonic signal arises from at least one movable reflector.

23. The method of claim 14, wherein the blood is diluted to achieve a monotonic correlation between backscatter and at least one of the properties.

24. The method of claim 14, wherein the blood sample is comprised within the body of a subject.

25. An apparatus for measuring one or more of HCT, HGB, MCV, RBC, MCHC, MCH, TPC of blood, comprising:

a means for holding a blood sample;

a means for sending one or more ultrasonic signals into said blood sample;

a means for receiving one or more ultrasonic signals from said blood sample; and

a means for measuring at least one characteristic selected from the group consisting of attenuation, backscatter, frequency response, continuous wave response, phase, amplitude, acoustic impedance, refraction angle, and combinations thereof, of at least one of the received ultrasonic signals.

26. The apparatus of claim 25, wherein the blood sample comprises 1 mL or less of blood.

27. The apparatus of claim 25, wherein the received ultrasonic signal comprises at least one selected from the group consisting of signals received from two or more acoustic paths, signals received from more than one reflective interface, and a combination thereof.

28. The apparatus of claim 27, wherein said signals are used in combination to eliminate one or more delays or transit times through one or more other materials from the calculation of transit time through blood.

29. The apparatus of claim 25, wherein the means for measuring comprises a means for measuring a combination of least two of the characteristics to eliminate at least one unknown variable.

30. The apparatus of claim 29, wherein the unknown variable is selected from the group consisting of a distance the ultrasound travels in blood, a temperature of the blood, and a combination thereof.

31. The apparatus of claim 25, wherein the means for receiving comprises a means for receiving one or more ultrasonic signal reflections.

32. The apparatus of claim 25, comprising at least one stepped reflector which returns multiple ultrasonic signal reflections.

33. The apparatus of claim 25, comprising at least one movable reflector.

34. The apparatus of claim 25, wherein the apparatus or chamber comprises a material with a speed of sound matched to the speed of sound in blood.

35. The apparatus of claim 34, wherein the material has a speed of sound ranging from 1000 m/s to 2500 m/s.

36. The apparatus of claim 25, wherein the blood is diluted to achieve a monotonic correlation between backscatter and at least one blood property selected from the group consisting of HCT, HGB, MCV, RBC, MCHC, MCH, TPC, and combinations thereof.

37. The apparatus of claim 25, wherein the blood sample is comprised within the body of a subject.

39. The method of claim 34, wherein the blood is comprised within a blood sample of 1 mL or less.

40. The method of claim 34, wherein the received ultrasonic signal comprises at least one selected from the group consisting of signals received from two or more acoustic paths, signals received from more than one reflective interface, and a combination thereof.

41. The method of claim 40, wherein said signals are used in combination to eliminate one or more delays or transit times through one or more other materials from the calculation of transit time through blood.

42. The method of claim 34, wherein the measuring comprises measuring a combination of least two of the characteristics to eliminate at least one unknown variable.

43. The method of claim 42, wherein the unknown variable is selected from the group consisting of a distance the ultrasound travels in blood, a temperature of the blood, and a combination thereof.

44. The method of claim 34, wherein one or more ultrasonic signal reflections are measured.

45. The method of claim 34, wherein the received ultrasonic signal arises from at least one stepped reflector which returns multiple ultrasonic signal reflections.

46. The method of claim 34, wherein the received ultrasonic signal arises from at least one movable reflector.

47. The method of claim 34, wherein the blood is diluted to achieve a monotonic correlation between backscatter and at least one of the properties.

48. The method of claim 34, wherein the blood sample is comprised within the body of a subject.

38. A method for measuring one or more of HCT, HGB, MCV, RBC, MCHC, MCH, or TPC of blood, comprising:

sending one or more ultrasonic signals into the blood;

receiving at least one ultrasonic signal from the blood;

measuring at least one characteristic selected from the group consisting of attenuation, backscatter, frequency response, continuous wave response, phase, amplitude, acoustic impedance, refraction angle, and combinations thereof, of at least one of the received ultrasonic signals; and

determining at least one property selected from the group consisting of HCT, HGB, MCV, RBC, MCHC, MCH, TPC, and combinations thereof, of the blood.

49. An apparatus for measuring one or more of HCT, HGB, MCV, RBC, MCHC, MCH, TPC of blood, comprising:

a means for holding a blood sample;

a means for sending one or more ultrasonic signals into said blood sample; and

a means for receiving one or more ultrasonic signals from said blood sample;

wherein said blood sample comprises 1 mL or less of blood.

50. The apparatus of claim 49, wherein the blood sample comprises 250 micro Liters or less of blood.

51. The apparatus of claim 49, wherein the received ultrasonic signal comprises at least one selected from the group consisting of signals received from two or more acoustic paths, signals received from more than one reflective interface, and a combination thereof.

52. The apparatus of claim 51, wherein said signals are used in combination to eliminate one or more delays or transit times through one or more other materials from the calculation of transit time through blood.

53. The apparatus of claim 49, further comprising at least one means for determining at least one property selected from the group consisting of HCT, HGB, MCV, RBC, MCHC, MCH, TPC, and combinations thereof, of blood.

54. The apparatus of claim 53, wherein the means for determining comprises a means for measuring a combination of least two characteristics selected from the group consisting of speed of sound, attenuation, backscatter, continuous wave excitation, frequency response, refraction angle, phase, amplitude, and acoustic impedance to eliminate at least one unknown variable.

55. The apparatus of claim 54, wherein the unknown variable is selected from the group consisting of a distance the ultrasound travels in blood, a temperature of the blood, and a combination thereof.

56. The apparatus of claim 49, wherein the means for receiving comprises a means for receiving one or more ultrasonic signal reflections.

57. The apparatus of claim 49, comprising at least one stepped reflector which returns multiple ultrasonic signal reflections.

58. The apparatus of claim 49, comprising at least one movable reflector.

59. The apparatus of claim 49, wherein the apparatus or means for holding a blood sample comprises a material with a speed of sound matched to the speed of sound in blood.

60. The apparatus of claim 59, wherein the material has a speed of sound ranging from 1000 m/s to 2500 m/s.

61. The apparatus of claim 59, wherein the blood is diluted to achieve a monotonic correlation between backscatter and at least one of the properties.

62. The apparatus of claim 59, wherein the blood sample is comprised within the body of a subject.

63. A method for measuring one or more of HCT, HGB, MCV, RBC, MCHC, MCH, or TPC of blood, comprising:

sending one or more ultrasonic signals into blood;

measuring at least one ultrasonic signal received from the blood;

compensating for a blood temperature other than by direct contact with the blood; and

determining at least one property selected from the group consisting of HCT, HGB, MCV, RBC, MCHC, MCH, TPC, and combinations thereof, of the blood.

64. The method of claim 63, wherein the blood is comprised within a blood sample of 1 mL or less.

65. The method of claim 63, wherein the received ultrasonic signal comprises at least one selected from the group consisting of signals received from two or more acoustic paths, signals received from more than one reflective interface, and a combination thereof.

66. The method of claim 63, wherein said signals are used in combination to eliminate one or more delays or transit times through one or more other materials from the calculation of transit time through blood.

67. The method of claim 63, wherein the measuring comprises measuring a combination of least two characteristics selected from the group consisting of speed of sound, attenuation, backscatter, continuous wave excitation, frequency response, refraction angle, phase, amplitude, and acoustic impedance to eliminate at least one unknown variable.

68. The method of claim 67, wherein the unknown variable is selected from the group consisting of a distance the ultrasound travels in blood, a temperature of the blood, and a combination thereof.

69. The method of claim 63, wherein one or more ultrasonic signal reflections are measured.

70. The method of claim 63, wherein the received ultrasonic signal arises from at least one stepped reflector which returns multiple ultrasonic signal reflections.

71. The method of claim 63, wherein the received ultrasonic signal arises from at least one movable reflector.

72. The method of claim 63, wherein the blood is diluted to achieve a monotonic correlation between backscatter and at least one of the properties.

73. The method of claim 63, wherein the blood sample is comprised within the body of a subject.

74. The method of claim 63, wherein said compensating comprises one or more selected from the group consisting of assuming the blood is in thermal equilibrium with its surroundings, measuring the temperature of the blood container, utilizing a chamber that allows the blood to approach thermal equilibrium rapidly, calculating temperature from ultrasonic measurements, using multiple thermal or ultrasonic measurements over time, and combinations thereof.

75. A method for measuring one or more of HCT, HGB, MCV, RBC, MCHC, MCH, or TPC of blood, comprising:

sending one or more ultrasonic signals into blood;

measuring more than one received ultrasonic signals; and

determining at least one property selected from the group consisting of HCT, HGB, MCV, RBC, MCHC, MCH, TPC, and combinations thereof, of the blood.

76. The method of claim 75, wherein the blood is comprised within a blood sample of 1 mL or less.

77. The method of claim 75, wherein the received ultrasonic signals comprise at least one selected from the group consisting of signals received from two or more acoustic paths, signals received from more than one reflective interface, and a combination thereof.

78. The method of claim 75, wherein said signals are used in combination to eliminate one or more delays or transit times through one or more other materials from the calculation of transit time through blood.

79. The method of claim 75, wherein the measuring comprises measuring a combination of least two characteristics selected from the group consisting of speed of sound, attenuation, backscatter, continuous wave excitation, frequency response, refraction angle, phase, amplitude, and acoustic impedance to eliminate at least one unknown variable.

80. The method of claim 79, wherein the unknown variable is selected from the group consisting of a distance the ultrasound travels in blood, a temperature of the blood, and a combination thereof.

81. The method of claim 75, wherein the received ultrasonic signals arise from at least one stepped reflector which returns multiple ultrasonic signal reflections.

82. The method of claim 75, wherein the received ultrasonic signals arise from at least one movable reflector.

83. The method of claim 75, wherein the blood is diluted to achieve a monotonic correlation between backscatter and at least one of the properties.

84. The method of claim 75, wherein the blood sample is comprised within the body of a subject.

85. The method of claim 75, wherein the received ultrasonic signals comprise at least one selected from the group consisting of signals received from two or more acoustic paths, signals received from more than one reflective interface, and a combination thereof.

86. An apparatus for measuring one or more of HCT, HGB, MCV, RBC, MCHC, MCH, TPC of whole blood, comprising:

a means for holding a whole blood sample;

a means for sending one or more ultrasonic signals into said blood sample; and

a means for receiving one or more ultrasonic signals from said blood sample.

87. The apparatus of claim 86, wherein the blood sample comprises 1 mL or less of blood.

88. The apparatus of claim 86, wherein the received ultrasonic signal comprises at least one selected from the group consisting of signals received from two or more acoustic paths, signals received from more than one reflective interface, and a combination thereof.

89. The apparatus of claim 88, wherein said signals are used in combination to eliminate one or more delays or transit times through one or more other materials from the calculation of transit time through blood.

90. The apparatus of claim 86, further comprising a means for determining at least one characteristic selected from the group consisting of speed of sound, attenuation, backscatter, continuous wave excitation, frequency response, refraction angle, phase, amplitude, acoustic impedance, and a combination thereof.

91. The apparatus of claim 90, wherein the means for determining comprises a means for determining a combination of at least two of the characteristics to eliminate at least one unknown variable selected from the group consisting of a distance the ultrasound travels in blood, a temperature of the blood, and a combination thereof.

92. The apparatus of claim 90, wherein the means for receiving comprises a means for receiving one or more ultrasonic signal reflections.

93. The apparatus of claim 90, comprising at least one stepped reflector which returns multiple ultrasonic signal reflections.

94. The apparatus of claim 90, comprising at least one movable reflector.

95. The apparatus of claim 90, wherein the apparatus or means for holding the whole blood sample comprises a material with a speed of sound matched to the speed of sound in blood.

96. The apparatus of claim 95, wherein the material has a speed of sound ranging from 1000 m/s to 2500 m/s.

97. The apparatus of claim 90, wherein the blood is diluted to achieve a monotonic correlation between backscatter and at least one of the properties.

98. The apparatus of claim 90, wherein the blood sample is comprised within the body of a subject.

99. A method for measuring one or more of HCT, HGB, MCV, RBC, MCHC, MCH, or TPC of whole blood, comprising:

sending one or more ultrasonic signals into whole blood;

measuring at least one ultrasonic signal received from the blood; and

determining one or more property selected from the group consisting of HCT, HGB, MCV, RBC, MCHC, MCH, TPC, and combinations thereof, of the whole blood.

100. The method of claim 99, wherein the blood is comprised within a blood sample of 1 mL or less.

101. The method of claim 99, wherein the received ultrasonic signal comprises at least one selected from the group consisting of signals received from two or more acoustic paths, signals received from more than one reflective interface, and a combination thereof.

102. The method of claim 101, wherein said signals are used in combination to eliminate one or more delays or transit times through one or more other materials from the calculation of transit time through blood.

103. The method of claim 99, wherein the measuring comprises measuring a combination of least two characteristics selected from the group consisting of speed of sound, attenuation, backscatter, continuous wave excitation, frequency response, refraction angle, phase, amplitude, and acoustic impedance to eliminate at least one unknown variable.

104. The method of claim 103, wherein the unknown variable is selected from the group consisting of a distance the ultrasound travels in blood, a temperature of the blood, and a combination thereof.

105. The method of claim 99, wherein one or more ultrasonic signal reflections are measured.

106. The method of claim 99, wherein the received ultrasonic signal arises from at least one stepped reflector which returns multiple ultrasonic signal reflections.

107. The method of claim 99, wherein the received ultrasonic signal arises from at least one movable reflector.

108. The method of claim 99, wherein the blood is diluted to achieve a monotonic correlation between backscatter and at least one of the properties.

109. The method of claim 99, wherein the blood sample is comprised within the body of a subject.

110. An apparatus for measuring one or more of HCT, HGB, MCV, RBC, MCHC, MCH, TPC of blood of a subject in-vivo, non-invasively, or through the skin of the subject, comprising:

a means for sending one or more ultrasonic signals into blood; and

a means for receiving one or more ultrasonic signals from said blood.

111. The apparatus of claim 110, wherein the received ultrasonic signal comprises at least one selected from the group consisting of signals received from two or more acoustic paths, signals received from more than one reflective interface, and a combination thereof.

112. The apparatus of claim 111, wherein said signals are used in combination to eliminate one or more delays or transit times through one or more other materials from the calculation of transit time through blood.

113. The apparatus of claim 110, further comprising means for determining one or more characteristics selected from the group consisting of speed of sound, attenuation, backscatter, continuous wave excitation, frequency response, refraction angle, phase, amplitude, acoustic impedance, and a combination thereof.

114. The apparatus of claim 113, wherein the means for determining comprising a means for determining two or more of the characteristics to eliminate at least one unknown variable.

115. The apparatus of claim 114, wherein the unknown variable is selected from the group consisting of a distance the ultrasound travels in blood, a temperature of the blood, and a combination thereof.

116. The apparatus of claim 110, wherein the means for receiving comprises a means for receiving one or more ultrasonic signal reflections.

117. The apparatus of claim 110, comprising at least one stepped reflector which returns multiple ultrasonic signal reflections.

118. The apparatus of claim 110, comprising at least one movable reflector.

119. The apparatus of claim 110, comprises a material with a speed of sound matched to the speed of sound in blood.

120. The apparatus of claim 119, wherein the material has a speed of sound ranging from 1000 m/s to 2500 m/s.

121. A method for measuring one or more of HCT, HGB, MCV, RBC, MCHC, MCH, or TPC of blood of a subject in-vivo, non-invasively, or through the skin, comprising:

sending one or more ultrasonic signals into blood of said subject in-vivo, non-invasively, or through the skin of said subject;

measuring at least one ultrasonic signal received from the blood; and

determining at least one property selected from the group consisting of HCT, HGB, MCV, RBC, MCHC, MCH, TPC, and combinations thereof, of the blood.

122. The method of claim 121, wherein the received ultrasonic signal comprises at least one selected from the group consisting of signals received from two or more acoustic paths, signals received from more than one reflective interface, and a combination thereof.

123. The method of claim 121, wherein said signals are used in combination to eliminate one or more delays or transit times through one or more other materials from the calculation of transit time through blood.

124. The method of claim 121, wherein the measuring comprises measuring one or more characteristic selected from the group consisting of speed of sound, attenuation, backscatter, continuous wave excitation, frequency response, refraction angle, phase, amplitude, acoustic impedance, and combinations thereof.

125. The method of claim 124, wherein the measuring comprises measuring a combination of at least two of the characteristics to eliminate at least one unknown variable.

126. The method of claim 125, wherein the unknown variable is selected from the group consisting of a distance the ultrasound travels in blood, a temperature of the blood, and a combination thereof.

127. The method of claim 121, wherein one or more ultrasonic signal reflections are measured.

128. The method of claim 121, wherein the received ultrasonic signal arises from at least one stepped reflector which returns multiple ultrasonic signal reflections.

129. The method of claim 121, wherein the received ultrasonic signal arises from at least one movable reflector.

130. A method for measuring one or more of HCT, HGB, MCV, RBC, MCHC, MCH, or TPC of blood, comprising:

sending one or more ultrasonic signals into blood;

measuring at least one ultrasonic signal received from the blood; and

determining at least one property selected from the group consisting of of HCT, HGB, MCV, RBC, MCHC, MCH, TPC, and a combination thereof, of the blood;

wherein the peak frequency of at least one of said ultrasonic signals is 6 MHz or higher.

131. The method of claim 130, wherein the blood is comprised within a blood sample of 1 mL or less.

132. The method of claim 130, wherein the received ultrasonic signal comprises at least one selected from the group consisting of signals received from two or more acoustic paths, signals received from more than one reflective interface, and a combination thereof.

133. The method of claim 132, wherein said signals are used in combination to eliminate one or more delays or transit times through one or more other materials from the calculation of transit time through blood.

134. The method of claim 132, wherein the measuring comprises measuring at least one characteristic selected from the group consisting of speed of sound, attenuation, backscatter, continuous wave excitation, frequency response, refraction angle, phase, amplitude, acoustic impedance, and combinations thereof.

135. The method of claim 134, wherein the measuring comprises measuring a combination of at least two characteristics to eliminate at least one unknown variable.

136. The method of claim 135, wherein the unknown variable is selected from the group consisting of a distance the ultrasound travels in blood, a temperature of the blood, and a combination thereof.

137. The method of claim 132, wherein one or more ultrasonic signal reflections are measured.

138. The method of claim 132, wherein the received ultrasonic signal arises from at least one stepped reflector which returns multiple ultrasonic signal reflections.

139. The method of claim 132, wherein the received ultrasonic signal arises from at least one movable reflector.

140. The method of claim 132, wherein the blood is diluted to achieve a monotonic correlation between backscatter and at least one of the properties.

141. The method of claim 132, wherein the blood sample is comprised within the body of a subject.

142. An apparatus for measuring one or more of HCT, HGB, MCV, RBC, MCHC, MCH, TPC of blood, comprising:

a means for holding a blood sample;

a means for sending one or more ultrasonic signals into said blood sample; and

a means for receiving one or more ultrasonic signals from said blood sample wherein the blood sample does not flow through the apparatus during the measurement.

143. The apparatus of claim 142, wherein the blood sample comprises 1 mL or less of blood.

144. The apparatus of claim 142, wherein the received ultrasonic signal comprises at least one selected from the group consisting of signals received from two or more acoustic paths, signals received from more than one reflective interface, and a combination thereof.

145. The apparatus of claim 144, wherein said signals are used in combination to eliminate one or more delays or transit times through one or more other materials from the calculation of transit time through blood.

146. The apparatus of claim 142, further comprising a means for determining at least one characteristic selected from the group consisting of speed of sound, attenuation, backscatter, continuous wave excitation, frequency response, refraction angle, phase, amplitude, acoustic impedance, and a combination thereof.

147. The apparatus of claim 146, wherein the means for determining comprises a means for determining a combination of at least two of the characteristics to eliminate at least one unknown variable.

148. The apparatus of claim 147, wherein the unknown variable is selected from the group consisting of a distance the ultrasound travels in blood, a temperature of the blood, and a combination thereof.

149. The apparatus of claim 142, wherein the means for receiving comprises a means for receiving one or more ultrasonic signal reflections.

150. The apparatus of claim 142, comprising at least one stepped reflector which returns multiple ultrasonic signal reflections.

151. The apparatus of claim 142, comprising at least one movable reflector.

152. The apparatus of claim 142, wherein the apparatus or means for holding the blood sample comprises a material with a speed of sound matched to the speed of sound in blood.

153. The apparatus of claim 152, wherein the material has a speed of sound ranging from 1000 m/s to 2500 m/s.

154. The apparatus of claim 142, wherein the blood is diluted to achieve a monotonic correlation between backscatter and at least one property selected from the group consisting of HCT, HGB, MCV, RBC, MCHC, MCH, TPC, and combinations thereof.

155. A method for measuring one or more of HCT, HGB, MCV, RBC, MCHC, MCH, or TPC of blood, comprising:

sending one or more ultrasonic signals into blood;

measuring at least one ultrasonic signal received from the blood;

measuring a combination more than one characteristic selected from the group consisting of attenuation, backscatter, frequency response, continuous wave response, phase, amplitude, acoustic impedance, speed of sound, and refraction angle of said measured ultrasonic signals; and

using said combination to determine at least one property selected from the group consisting of HCT, HGB, MCV, RBC, MCHC, MCH, TPC, and combinations thereof, of the blood.

156. The method of claim 155, wherein the blood is comprised within a blood sample of 1 mL or less.

157. The method of claim 155, wherein the received ultrasonic signal comprises at least one selected from the group consisting of signals received from two or more acoustic paths, signals received from more than one reflective interface, and a combination thereof.

158. The method of claim 157, wherein said signals are used in combination to eliminate one or more delays or transit times through one or more other materials from the calculation of transit time through blood.

159. The method of claim 155, further comprising measuring a combination of least two characteristics selected from the group consisting of speed of sound, attenuation, backscatter, continuous wave excitation, frequency response, refraction angle, phase, amplitude, and acoustic impedance to eliminate at least one unknown variable.

160. The method of claim 159, wherein the unknown variable is selected from the group consisting of a distance the ultrasound travels in blood, a temperature of the blood, and a combination thereof.

161. The method of claim 155, wherein one or more ultrasonic signal reflections are measured.

162. The method of claim 155, wherein the received ultrasonic signal arises from at least one stepped reflector which returns multiple ultrasonic signal reflections.

163. The method of claim 155, wherein the received ultrasonic signal arises from at least one movable reflector.

164. The method of claim 155, wherein the blood is diluted to achieve a monotonic correlation between backscatter and at least one of the properties.

165. The method of claim 155, wherein the blood sample is comprised within the body of a subject.

166. An apparatus for measuring one or more of HCT, HGB, MCV, RBC, MCHC, or MCH of blood, comprising:

a means for holding a blood sample;

a means for sending one or more ultrasonic signals into blood;

a means for receiving at least one ultrasonic signal from the blood; and

a means for determining at least one property selected from the group consisting of HCT, HGB, MCV, RBC, MCHC, MCH, and combinations thereof, of the blood;

wherein the ultrasound travels in a vertical direction through the blood with respect to the horizon.

167. The apparatus of claim 166, wherein the blood sample comprises 1 mL or less of blood.

168. The apparatus of claim 166, wherein the received ultrasonic signal comprises at least one selected from the group consisting of signals received from two or more acoustic paths, signals received from more than one reflective interface, and a combination thereof.

169. The apparatus of claim 168, wherein said signals are used in combination to eliminate one or more delays or transit times through one or more other materials from the calculation of transit time through blood.

170. The apparatus of claim 166, wherein the means for determining comprises a means for measuring at least one characteristic selected from the group consisting of speed of sound, attenuation, backscatter, continuous wave excitation, frequency response, refraction angle, phase, amplitude, acoustic impedance, and combinations thereof.

171. The apparatus of claim 170, wherein the means for determining comprises a means for determining a combination of at least two of the characteristics to eliminate at least one unknown variable.

172. The apparatus of claim 171, wherein the unknown variable is selected from the group consisting of a distance the ultrasound travels in blood, a temperature of the blood, and a combination thereof.

173. The apparatus of claim 166, wherein the means for receiving comprises a means for receiving one or more ultrasonic signal reflections.

174. The apparatus of claim 166, comprising at least one stepped reflector which returns multiple ultrasonic signal reflections.

175. The apparatus of claim 166, comprising at least one movable reflector.

176. The apparatus of claim 166, wherein the apparatus or means for holding the blood sample comprises a material with a speed of sound matched to the speed of sound in blood.

177. The apparatus of claim 176, wherein the material has a speed of sound ranging from 1000 m/s to 2500 m/s.

178. The apparatus of claim 166, wherein the blood is diluted to achieve a monotonic correlation between backscatter and at least one of the properties.

179. The apparatus of claim 166, wherein the blood sample is comprised within the body of a subject.

180. A method for measuring one or more of HCT, HGB, MCV, RBC, MCHC, or MCH of blood, comprising:

sending one or more ultrasonic signals into blood;

measuring at least one ultrasonic signal received from the blood; and

determining at least one property selected from the group consisting of HCT, HGB, MCV, RBC, MCHC MCH, and combinations thereof, of the blood;

wherein the ultrasound travels in a vertical direction through the blood with respect to the horizon.

181. The method of claim 180, wherein the blood is comprised within a blood sample of 1 mL or less.

182. The method of claim 180, wherein the received ultrasonic signal comprises at least one selected from the group consisting of signals received from two or more acoustic paths, signals received from more than one reflective interface, and a combination thereof.

183. The method of claim 180, wherein said signals are used in combination to eliminate one or more delays or transit times through one or more other materials from the calculation of transit time through blood.

184. The method of claim 180, wherein the measuring comprises measuring at least one characteristic selected from the group consisting of speed of sound, attenuation, backscatter, continuous wave excitation, frequency response, refraction angle, phase, amplitude, acoustic impedance, and a combination thereof.

185. The method of claim 184, wherein the measuring comprises measuring a combination of at least two of the characteristics to eliminate at least one unknown variable.

186. The method of claim 185, wherein the unknown variable is selected from the group consisting of a distance the ultrasound travels in blood, a temperature of the blood, and a combination thereof.

187. The method of claim 180, wherein one or more ultrasonic signal reflections are measured.

188. The method of claim 180, wherein the received ultrasonic signal arises from at least one stepped reflector which returns multiple ultrasonic signal reflections.

189. The method of claim 180, wherein the received ultrasonic signal arises from at least one movable reflector.

190. The method of claim 180, wherein the blood is diluted to achieve a monotonic correlation between backscatter and at least one of the properties.

191. The method of claim 180, wherein the blood sample is comprised within the body of a subject.

192. An apparatus for measuring HCT, HGB, MCV, RBC, MCHC or MCH of blood, comprising:

a sample chamber configured to contain blood; and

one or more transducers configured to send one or more ultrasonic signals into said blood; and

one or more transducers configured to receive said ultrasonic signals from said blood.

193. The apparatus of claim 192, further comprising a means for determining at least one property selected from the group consisting of HCT, HGB, MCV, RBC, MCHC, MCH, and a combination thereof, of blood.

194. The apparatus of claim 192, wherein the blood sample comprises 1 mL or less of blood.

195. The apparatus of claim 192, wherein the received ultrasonic signal comprises at least one selected from the group consisting of signals received from two or more acoustic paths, signals received from more than one reflective interface, and a combination thereof.

196. The apparatus of claim 195, wherein said signals are used in combination to eliminate one or more delays or transit times through one or more other materials from the calculation of transit time through blood.

197. The apparatus of claim 192, further comprising a means for determining at least one characteristic selected from the group consisting of speed of sound, attenuation, backscatter, continuous wave excitation, frequency response, refraction angle, phase, amplitude, acoustic impedance, and a combination thereof.

198. The apparatus of claim 197, wherein the means for determining comprises a means for determining a combination of at least two of the characteristics to eliminate at least one unknown variable.

199. The apparatus of claim 198, wherein the unknown variable is selected from the group consisting of a distance the ultrasound travels in blood, a temperature of the blood, and a combination thereof.

200. The apparatus of claim 192, the transducers configured to receive are configured to receive one or more ultrasonic signal reflections.

201. The apparatus of claim 192, comprising at least one stepped reflector which returns multiple ultrasonic signal reflections.

202. The apparatus of claim 192, comprising at least one movable reflector.

203. The apparatus of claim 192, wherein the apparatus or chamber comprises a material with a speed of sound matched to the speed of sound in blood.

204. The apparatus of claim 203, wherein the material has a speed of sound ranging from 1000 m/s to 2500 m/s.

205. The apparatus of claim 192, wherein the blood is diluted to achieve a monotonic correlation between backscatter and at least one of the properties.

206. The apparatus of claim 192, wherein the blood sample is comprised within the body of a subject.

207. An apparatus for measuring HCT, HGB, MCV, RBC, MCHC, MCH or TPC of whole blood, comprising:

a sample chamber configured to contain whole blood; and

one or more transducers configured to send one or more ultrasonic signals into said blood; and

one or more transducers configured to receive said ultrasonic signals from said blood.

208. The apparatus of claim 207, further comprising a means for determining at least one property selected from the group consisting of HCT, HGB, MCV, RBC, MCHC, MCH, and a combination thereof, of blood.

209. The apparatus of claim 207, wherein the blood sample comprises 1 mL or less of blood.

210. The apparatus of claim 207, wherein the received ultrasonic signal comprises at least one selected from the group consisting of signals received from two or more acoustic paths, signals received from more than one reflective interface, and a combination thereof.

211. The apparatus of claim 210, wherein said signals are used in combination to eliminate one or more delays or transit times through one or more other materials from the calculation of transit time through blood.

212. The apparatus of claim 207, further comprising a means for determining at least one characteristic selected from the group consisting of speed of sound, attenuation, backscatter, continuous wave excitation, frequency response, refraction angle, phase, amplitude, acoustic impedance, and a combination thereof.

213. The apparatus of claim 212, wherein the means for determining comprises a means for determining a combination of at least two of the characteristics to eliminate at least one unknown variable.

214. The apparatus of claim 213, wherein the unknown variable is selected from the group consisting of a distance the ultrasound travels in blood, a temperature of the blood, and a combination thereof.

215. The apparatus of claim 207, the transducers configured to receive are configured to receive one or more ultrasonic signal reflections.

216. The apparatus of claim 207, comprising at least one stepped reflector which returns multiple ultrasonic signal reflections.

217. The apparatus of claim 207, comprising at least one movable reflector.

218. The apparatus of claim 207, wherein the apparatus or chamber comprises a material with a speed of sound matched to the speed of sound in blood.

219. The apparatus of claim 218, wherein the material has a speed of sound ranging from 1000 m/s to 2500 m/s.

220. The apparatus of claim 207, wherein the blood is diluted to achieve a monotonic correlation between backscatter and at least one of the properties.

221. The apparatus of claim 207, wherein the blood sample is comprised within the body of a subject.