Multidimensional bioelectrical tissue analyzer

• US 7,499,745 B2
• Filed: 02/27/2001
• Issued: 03/03/2009
• Est. Priority Date: 02/28/2000
• Status: Active Grant

• Current Assignee: Delphinus Medical Technologies, Inc.
• Original Assignee: Barbara Ann Karmanos Cancer Institute
• Inventors: Duncan, Robert, Littrup, Peter
• Primary Examiner(s): Hindenburg; Max
• Assistant Examiner(s): Hoekstra; Jeffrey G
• Application Number:
  US09/794,612
• Publication Number:
  US 20010051774A1
• Time in Patent Office: 2,926 Days
• Field of Search: 600/547
• US Class Current: 600/547
• CPC Class Codes: A61B 5/053 Measuring electrical impedance or conductance of a portion of the body
• CPC Class Codes: A61B 5/4312 Breast evaluation or disorder diagnosis A61B5/0091 takes precedence
• CPC Class Codes: A61B 5/4869 Determining body composition
• CPC Class Codes: A61B 5/6806 Gloves
• CPC Class Codes: G01N 33/48728 Investigating individual cells, e.g. by patch clamp, voltage clamp investigating individual particles in general G01N15/10

Abstract

A method and apparatus that use complex impedance measurements of tissue in human or animal bodies for the detection and characterization of medical pathologies is disclosed. An analysis of the complex impedance measurements is performed by a trained evaluation system that uses a nonlinear continuum model to analyze the resistive, capacitive, and inductive measurements collected from a plurality of sensing electrodes. The analysis of the impedance measurements results in the construction of a multidimensional space that defines the tissue characteristics, which the trained evaluation system uses to detect and characterize pathologies. The method and apparatus are sufficiently general to be applied to various types of human and animal tissues for the analysis of various types of medical pathologies.

Claims

1. An apparatus for detection and characterization of one or more medical pathologies within an object under study comprising:

(a) a current source adapted to provide current with a predetermined current waveform, said current source being disposed so as to be capable of electrically stimulating such object;

(b) a plurality of electrodes being disposed relative to such object to receive current from such object, each of said plurality of electrodes being capable of measuring a voltage;

(c) means for controlling such current source and said plurality of electrodes to produce and receive current; and

(d) a device coupled with said plurality of electrodes and configured to perform the steps of;

(i) calculating a plurality of complex impedances, each of said plurality of complex impedances corresponding to a current drive path defined by said current source and one of said plurality of electrodes;

(ii) constructing a multidimensional representation of the electrical characteristics of a region within said object under study using said plurality of complex impedances by solving a continuum electrical model that incorporates nonlinearities; and

(iii) detecting and characterizing such one or more medical pathologies within said object under study from said multidimensional representation.

2. The apparatus according to claim 1 wherein said current source comprises a plurality of current sources.

3. The apparatus according to claim 1 wherein said plurality of electrodes includes at least one device that is used both as a current source and as a current sink.

4. The apparatus according to claim 1 wherein said plurality of electrodes comprises a re-configurable number of electrodes.

5. The apparatus according to claim 1 wherein said plurality of electrodes comprises three electrodes.

6. The apparatus according to claim 5 wherein said plurality of electrodes are disposed on a glove, a flexible membrane to attach to skin anywhere.

7. The apparatus according to claim 1 wherein said plurality of electrodes comprises more than 104 electrodes.

8. The apparatus according to claim 1 wherein said predetermined current waveform is harmonic.

9. The apparatus according to claim 1 wherein said predetermined current waveform has a profile selected from the group consisting of square, triangular, ramp, pulse, and sinc.

10. The apparatus according to claim 1 wherein said predetermined current waveform is periodic and comprises an oscillation frequency between 2 Hz and 2 MHz.

11. The apparatus according to claim 1 wherein said predetermined current waveform is periodic and has a magnitude between 10 nA and 1 mA.

12. The apparatus according to claim 1 further comprising means for reducing electrical noise.

13. The apparatus according to claim 12 wherein said means for reducing comprises a lock-in amplifier.

14. The apparatus according to claim 1 wherein said device further performs the step of calculating a plurality of complex impedance derivatives with respect to frequency, each of said plurality of complex impedance derivatives corresponding to a current drive path defined by said current source and one of said plurality of electrodes.

15. The apparatus according to claim 1 wherein said continuum electrical model comprises Zener-diode elements.

16. The apparatus according to claim 1 wherein said continuum electrical model comprises an inductive element.

17. The apparatus according to claim 1 wherein said continuum electrical model comprises:

(a) an inductive element;

(b) a capacitive element;

(c) a resistive element; and

(d) Zener-diode elements.

18. The apparatus according to claim 1 wherein said multidimensional representation is a ten-dimensional representation, or any reduced-dimensional representation.

19. The apparatus according to claim 18 wherein such object under study comprises human or animal tissue and said multi-dimensional representation comprises dimensions corresponding to differential cell-membrane capacitance, intracellular-fluid differential resistance, extracellular differential resistance, differential surface membrane inductance, range in variation of said differential cell-membrane capacitance, range in variation of said intracellular-fluid differential resistance, range in variation of said extracellular differential resistance, range in variation of said differential surface membrane inductance, amplitude of said current source, and frequency of said current waveform.

20. The apparatus according to claim 1 wherein said multidimensional representation is a six-dimensional representation.

21. The apparatus according to claim 20 wherein such object under study comprises human or animal tissue and said six-dimensional representation comprises dimensions corresponding to differential cell-membrane capacitance contracted with a range in variation of said differential cell-membrane capacitance, intracellular-fluid differential resistance contracted with a range in variation of said intracellular-fluid differential resistance, extracellular differential resistance contracted with a range in variation of said extracellular differential resistance, differential surface membrane inductance contracted with a range in variation of said differential surface membrane inductance, amplitude of said current source, and frequency of said current waveform.

22. The apparatus according to claim 1 wherein said device further performs the step of projecting said multidimensional representation into a plurality of low-dimensional spaces.

23. The apparatus according to claim 22 wherein said device further performs the steps of selecting one of said plurality of lower-dimensional spaces and displaying the selected lower-dimensional space.

24. The apparatus according to claim 1 wherein said device uses a trained evaluation system to perform said step of detecting and characterizing.

25. The apparatus according to claim 24 wherein said trained evaluation system comprises an expert system.

26. The apparatus according to claim 24 wherein said trained evaluation system comprises a neural net.

27. The apparatus according to claim 24 wherein said trained evaluation system uses stochastic optimization.

28. The apparatus according to claim 24 wherein said trained evaluation system uses a genetic algorithm.

29. The apparatus according to claim 1 wherein said object under study comprises a plurality of animal or human tissues.

30. The apparatus according to claim 29 wherein said plurality of animal or human tissues comprises a human breast.

31. The apparatus according to claim 29 wherein said plurality of animal or human tissues comprises a human prostate.

32. The apparatus according to claim 29 wherein said plurality of animal or human tissues comprises a human kidney.

33. The apparatus according to claim 29 wherein said plurality of animal or human tissues comprises a human lung.

34. The apparatus according to claim 29 wherein said plurality of animal or human tissues comprises a section of a human alimentary canal.

35. The apparatus according to claim 29 wherein said plurality of animal or human tissues comprises a human liver, heart or brain.

36. The apparatus according to claim 29 wherein said plurality of animal or human tissues comprises lymphatic tissue.

37. The apparatus according to claim 1 further comprising means for generating a compression wave within said object under study.

38. The apparatus according to claim 37 wherein said means for generating comprises an ultrasound source.

39. The apparatus according to claim 37 wherein said means for generating comprises a glove, whereby a practitioner generates said compression wave by palpation.

40. The apparatus according to claim 1 wherein at least one of said plurality of electrodes is disposed on a glove, a flexible membrane to attach to skin anywhere, or said ring of electrodes on elastic bands.

41. The apparatus according to claim 40 further comprising a position sensor disposed on said glove.

42. The apparatus according to claim 1 further comprising:

(a) a radiation source adapted to emit radiation within a predetermined frequency range or at a predetermined frequency onto a volume within such object under study, said radiation source being disposed so as to be capable of radiating such object; and

(b) a radiation detector disposed relative to such object to receive radiation scattered by said volume, said radiation detector being capable of providing data corresponding to the radiation received; and

wherein said device further performs the step of using said data in combination with said plurality of complex impedances to further characterize said one or more medical pathologies within said volume.

43. The apparatus according to claim 42 wherein said radiation source is a sound source and said radiation detector is a sound detector.

44. The apparatus according to claim 43 wherein said radiation source and said sound detector are fabricated in a single unit.

45. The apparatus according to claim 43 wherein said data are digitized.

46. The apparatus according to claim 45 wherein said data are digitized at a rate greater than or equal to 30 kHz.

47. The apparatus according to claim 43 wherein said sound source emits monochromatic radiation and said sound detector detects only scattered radiation that is at a constant predetermined phase relationship with said monochromatic radiation.

48. The apparatus according to claim 43 wherein said ultrasound source emits monochromatic radiation and said sound detector detects only scattered radiation that is detuned from said monochromatic radiation.

49. The apparatus according to claim 43 wherein said sound source emits chirped radiation.

50. The apparatus according to claim 43 wherein said one or more medical pathologies comprises a cardiac pathology.

51. The apparatus according to claim 50 wherein said cardiac pathology is a valvular dysfunction.

52. The apparatus according to claim 50 further comprising a standard electrocardiograph.

53. The apparatus according to claim 43 wherein said one or more medical pathologies comprises a vascular pathology.

54. The apparatus according to claim 53 further comprising means for imposing a concentrated magnetic field within said object under study.

55. The apparatus according to claim 54 further comprising means for scanning said concentrated magnetic field across said object under study.

56. The apparatus according to claim 43 wherein said one or more medical pathologies comprises a pulmonary pathology.

57. The apparatus according to claim 56 wherein said pulmonary pathology is selected from the group consisting of a bronchus spasm, pneumothorax, hyperinflation, eduma, consolidation, and a neoplasm.

58. The apparatus according to claim 43 wherein said one or more medical pathologies comprises a neurological pathology.

59. The apparatus according to claim 58 further comprising a standard electroencephalograph.

60. The apparatus according to claim 43 wherein said one or more medical pathologies comprises a neuromuscular pathology.

61. The apparatus according to claim 60 further comprising a standard electromyograph.

62. The apparatus according to claim 43 wherein said one or more medical pathologies comprises a bone fracture.

63. The apparatus according to claim 1 further comprising a container for holding said object under study wherein said current source and said plurality of electrodes are disposed within walls of said container.

64. The apparatus according to claim 63 wherein said object under study is a cell culture.

65. The apparatus according to claim 63 wherein said object under study is a surgical tissue specimen.

66. The apparatus according to claim 63 wherein said object under study is a laboratory animal.

67. The apparatus according to claim 63 wherein said object under study is a tissue equivalent model.

68. The apparatus according to claim 63 wherein said container comprises a plurality of wells in a plate.

69. The apparatus according to claim 63 wherein said container is a test tube.

70. The apparatus according to claim 63 wherein said container is a Petri dish.

71. The apparatus according to claim 63 wherein said container comprises a hemispherically shaped bottom.

72. The apparatus according to claim 63 further comprising an electrically conductive fluid within said container.

73. The apparatus according to claim 72 wherein said electrically conductive fluid has a specific gravity greater than said object under study.

74. The apparatus according to claim 72 wherein said electrically conductive fluid has a specific gravity greater than or equal to 1.2.

75. The apparatus according to claim 1 further comprising a contact instrument wherein said current source and said plurality of electrodes are disposed on one surface of said contact instrument.

76. The apparatus according to claim 1 further comprising a needle wherein said current source and said plurality of electrodes are disposed in said needle.

77. The apparatus according to claim 76 further comprising a container for holding said object under study.

78. The apparatus according to claim 77 wherein said object under study is selected from the group consisting of a cell culture, a surgical tissue specimen, a laboratory animal, and a tissue equivalent model or simulator and said container is selected from the group consisting of a culture well, a test tube, a Petri dish, and a jar with a hemispherical bottom.

79. An apparatus for detection and characterization of one or more medical pathologies within an object under study comprising:

(a) a current source adapted to provide current with a predetermined current waveform, said current source being disposed so as to be capable of electrically stimulating such object;

(b) a plurality of electrodes being disposed relative to such object to receive current from such object, each of said plurality of electrodes being capable of measuring a voltage;

(c) means for controlling such current source and said plurality of electrodes to produce and receive current; and

(d) a device coupled to said plurality of electrodes and configured to analyze data received from said plurality of electrodes to detect and characterize such one or more medical pathologies, wherein said device calculates a plurality of complex impedances, each of said plurality of complex impedances corresponding to a current drive path defined by said current source and one of said plurality of electrodes, and constructs a multidimensional representation of the electrical characteristics of a region within said object under study using the plurality of complex impedances by solving a continuum electrical model that incorporates nonlinearities.

80. The apparatus according to claim 79 wherein said predetermined current waveform is sinusoidal.

81. The apparatus according to claim 79 wherein said predetermined current waveform has a profile selected from the group consisting of square, triangular, ramp, pulse, and sinc.

82. The apparatus according to claim 79 wherein said predetermined current waveform is periodic and comprises an oscillation frequency between 2 Hz and 2 MHz.

83. The apparatus according to claim 79 wherein said predetermined current waveform is periodic and has a magnitude between 10 nA and 1 mA.

84. An apparatus for detection and characterization of one or more medical pathologies within an object under study comprising:

(a) a current source adapted to provide current that electrically stimulates such object;

(b) a plurality of electrodes being disposed relative to such object to receive current from such object, each of said plurality of electrodes being capable of measuring a voltage;

(c) means for controlling such current source and said plurality of electrodes to produce and receive current; and

(d) a device coupled to said plurality of electrodes and configured to perform the steps of;

(i) calculating a plurality of complex impedances, each of said plurality of complex impedances corresponding to a current drive path defined by said current source and one of said plurality of electrodes; and

(ii) analyzing said plurality of complex impedances to detect and characterize such one or more medical pathologies by solving a continuum electrical model that incorporates nonlinearities.

85. The apparatus according to claim 84 wherein said device is further configured to perform the step of constructing a multidimensional representation of the electrical characteristics of said object under study using said plurality of complex impedances.

86. The apparatus according to claim 85 wherein said device is further configured to perform the step of projecting said multidimensional representation into a plurality of three-dimensional spaces.

87. An apparatus for detection and characterization of one or more medical pathologies within an object under study comprising:

(a) a current source adapted to provide current that electrically stimulates such object;

(b) a plurality of electrodes being disposed relative to such object to receive current from such object, each of said plurality of electrodes being capable of measuring a voltage;

(c) means for controlling such current source and said plurality of electrodes to produce and receive current; and

(d) a device coupled to said plurality of electrodes and configured to analyze data received from said plurality of electrodes to detect and characterize such one or more medical pathologies by solving a continuum electrical model that incorporates nonlinearities to construct a multidimensional representation of the electrical characteristics of said object under study.

88. The apparatus according to claim 87 wherein said continuum electrical model comprises Zener-diode elements.

89. The apparatus according to claim 87 wherein said continuum electrical model comprises an inductive element.

90. The apparatus according to claim 87 wherein said continuum electrical model comprises:

(a) an inductive element;

(b) a capacitive element;

(c) a resistive element; and

(d) Zener-diode elements.

91. A method for detection and characterization of one or more medical pathologies within an object under study comprising the steps of:

(a) stimulating such object electrically with a current source adapted to provide current with a predetermined current waveform;

(b) measuring a plurality of voltages with a plurality of electrodes disposed relative to such object for receiving current from such object;

(c) calculating a plurality of complex impedances from said plurality of voltages, each of said plurality of complex impedances corresponding to a current drive path defined by said current source and one of said plurality of electrodes;

(d) constructing a multidimensional representation of the electrical characteristics of a region within such object using said plurality of complex impedances by solving a continuum electrical model that incorporates nonlinearities; and

(e) detecting and characterizing such one or more medical pathologies within such object from said multidimensional representation.

92. The method according to claim 91 wherein said current source comprises a plurality of current sources.

93. The method according to claim 91 wherein said plurality of electrodes includes at least one device that is used both as a current source and as a current sink.

94. The method according to claim 91 wherein said plurality of electrodes comprises three electrodes.

95. The method according to claim 91 wherein said plurality of electrodes comprises ten electrodes.

96. The method according to claim 95 wherein said plurality of electrodes are disposed on a pair of gloves, a flexible membrane to attach to skin anywhere, or a ring of electrodes on elastic bands.

97. The method according to claim 91 wherein said plurality of electrodes comprises more than 104 electrodes.

98. The method according to claim 91 wherein said predetermined current waveform is sinusoidal.

99. The method according to claim 91 wherein said predetermined current waveform has a profile selected from the group consisting of square, triangular, ramp, pulse, and sinc.

100. The method according to claim 91 wherein said predetermined current waveform is periodic and comprises an oscillation frequency between 2 Hz and 2 MHz.

101. The method according to claim 91 wherein said predetermined current waveform is periodic and has a magnitude between 10 nA and 1 mA.

102. The method according to claim 91 further comprising the step of reducing electrical noise.

103. The method according to claim 102 wherein said step of reducing electrical noise is accomplished with a lock-in amplifier.

104. The method according to claim 91 further comprising the step of calculating a plurality of complex impedance derivatives with respect to frequency, each of said plurality of complex impedance derivatives corresponding to a current drive path defined by said current source and one of said plurality of electrodes.

105. The method according to claim 91 wherein said continuum electrical model comprises Zener-diode elements.

106. The method according to claim 91 wherein said continuum electrical model comprises an inductive element.

107. The method according to claim 91 wherein said continuum electrical model comprises:

(a) an inductive element;

(b) a capacitive element;

(c) a resistive element; and

(d) Zener-diode elements.

108. The method according to claim 91 wherein said multidimensional representation is a ten-dimensional representation.

109. The method according to claim 108 wherein said ten-dimensional representation comprises dimensions corresponding to differential cell-membrane capacitance, intracellular-fluid differential resistance, extracellular differential resistance, differential surface membrane inductance, range in variation of said differential cell-membrane capacitance, range in variation of said intracellular-fluid differential resistance, range in variation of said extracellular differential resistance, range in variation of said differential surface membrane inductance, amplitude of said current source, and frequency of said current waveform.

110. The method according to claim 91 wherein said multidimensional representation is a six-dimensional representation.

111. The method according to claim 110 wherein said six-dimensional representation comprises dimensions corresponding to differential cell-membrane capacitance contracted with a range in variation of said differential cell-membrane capacitance, intracellular-fluid differential resistance contracted with a range in variation of said intracellular-fluid differential resistance, extracellular differential resistance contracted with a range in variation of said extracellular differential resistance, differential surface membrane inductance contracted with a range in variation of said differential surface membrane inductance, amplitude of said current source, and frequency of said current waveform.

112. The method according to claim 91 further comprising the step of projecting said multidimensional representation into a plurality of three-dimensional spaces.

113. The method according to claim 112 further comprising the steps of selecting one of said plurality of three-dimensional spaces and displaying the selected three-dimensional space.

114. The method according to claim 91 wherein said step of detecting and characterizing is performed by a trained evaluation system.

115. The method according to claim 114 wherein said trained evaluation system comprises an expert system.

116. The method according to claim 114 wherein said trained evaluation system comprises a neural net.

117. The method according to claim 114 wherein said trained evaluation system uses stochastic optimization.

118. The method according to claim 114 wherein said trained evaluation system uses a genetic algorithm.

119. The method according to claim 91 wherein said object under study comprises a plurality of animal or human tissues.

120. The method according to claim 119 wherein said plurality of animal or human tissues comprises a human breast.

121. The method according to claim 119 wherein said plurality of animal or human tissues comprises a human prostate.

122. The method according to claim 119 wherein said plurality of animal or human tissues comprises a human kidney.

123. The method according to claim 121 wherein said current source is positioned over the lower anterior abdomen of a patient and said plurality of electrodes are disposed on a probe inserted within the rectal cavity of said patient.

124. The method according to claim 119 wherein said plurality of animal or human tissues comprises a human lung.

125. The method according to claim 119 wherein said plurality of animal or human tissues comprises a section of a human alimentary canal.

126. The method according to claim 119 wherein said plurality of animal or human tissues comprises a human liver.

127. The method according to claim 119 wherein said plurality of animal or human tissues comprises lymphatic tissue.

128. The method according to claim 91 wherein said object under study is a surgical specimen.

129. The method according to claim 91 wherein said object under study is a laboratory animal.

130. The method according to claim 91 wherein said object under study is a tissue equivalent model simulator.

131. The method according to claim 91 further comprising the step of generating a compression wave within said object under study.

132. The method according to claim 131 wherein said step of generating is accomplished with an ultrasound source.

133. The method according to claim 131 wherein said step of generating is accomplished by palpation.

134. The method according to claim 91 wherein at least one of said plurality of electrodes is disposed on a glove.

135. The method according to claim 134 further comprising the step of determining the position of said at least one of said plurality of electrodes with respect to said object under study.

136. The method according to claim 135 wherein said step of determining is accomplished with a plurality of position sensors disposed on said glove.

137. The method according to claim 91 further comprising the steps of:

(a) irradiating, using a radiation source disposed so as to be capable of irradiating such object, upon a volume within the object under study with radiation within a predetermined frequency range or at a predetermined frequency;

(b) receiving, using a plurality of radiation detectors being disposed relative to such object, radiation scattered by said volume within the object and providing data corresponding to the radiation received; and

(c) using said data in combination with said plurality of complex impedances to further characterize said one or more medical pathologies within said volume under study.

138. The method according to claim 137 wherein said radiation source is an ultrasound source and said plurality of radiation detectors is a plurality of ultrasound detectors.

139. The method according to claim 138 wherein said ultrasound source and said plurality of ultrasound detectors includes at least one device that is used both as an ultrasound source and as an ultrasound detector.

140. The method according to claim 138 further comprising the step of digitizing said data.

141. The method according to claim 140 wherein said data are digitized at a rate greater than or equal to 30 kHz.

142. The method according to claim 138 wherein said ultrasound source emits monochromatic radiation and said plurality of ultrasound detectors detect only scattered radiation that is at a constant predetermined phase relationship with said monochromatic radiation.

143. The method according to claim 138 wherein said ultrasound source emits monochromatic radiation and said ultrasound detector detects only scattered radiation that is detuned from said monochromatic radiation.

144. The method according to claim 138 wherein said ultrasound source emits chirped radiation.

145. The method according to claim 138 wherein said one or more medical pathologies comprises a cardiac pathology.

146. The method according to claim 145 wherein said cardiac pathology is a valvular dysfunction.

147. The method according to claim 138 wherein said one or more medical pathologies comprises a vascular pathology.

148. The method according to claim 147 further comprising the step of imposing a concentrated magnetic field within said object under study.

149. The method according to claim 148 further comprising the step of scanning said concentrated magnetic field across said object under study.

150. The method according to claim 138 wherein said one or more medical pathologies comprises a pulmonary pathology.

151. The method according to claim 150 wherein said pulmonary pathology is selected from the group consisting of a bronchus spasm, Stein Ron Chi, consolidation, and a neoplasm.

152. The method according to claim 138 wherein said one or more medical pathologies comprises a neurological pathology.

153. The method according to claim 138 wherein said one or more medical pathologies comprises a neuromuscular pathology.

154. The method according to claim 138 wherein said one or more medical pathologies comprises a bone fracture.

155. The method according to claim 91 further comprising the step of analyzing such object with at least one supplementary technique.

156. The method according to claim 155 wherein said step of analyzing is performed prior to said step of measuring to identify a suspicious volume within such object and wherein said region is limited to such suspicious volume.

157. The method according to claim 155 wherein said step of analyzing is performed subsequent to said step of detecting and characterizing.

158. The method according to claim 155 wherein said at least one supplementary technique is a technique selected from the group consisting of x-ray imaging, mammography, computed tomography, magnetic resonance imaging, ultrasound, nuclear medicine, single-photon emission computed tomography, and positron-emission tomography.

159. A method for detection and characterization of one or more medical pathologies within an object under study comprising:

(a) stimulating such object electrically with a current source adapted to provide current with a predetermined current waveform;

(b) measuring a plurality of voltages with a plurality of electrodes disposed relative to such object for receiving current from such object; and

(c) analyzing data received from said plurality of electrodes to detect and characterize such one or more medical pathologies, wherein said analyzing constructs a multidimensional representation of the electrical characteristics of a region within such object by solving a continuum electrical model that incorporates nonlinearities.

160. The method according to claim 159 wherein said predetermined current waveform is sinusoidal.

161. The method according to claim 159 wherein said predetermined current waveform has a profile selected from the group consisting of square, triangular, ramp, pulse, and sinc.

162. The method according to claim 159 wherein said predetermined current waveform is periodic and comprises an oscillation frequency between 2 Hz and 2 MHz.

163. The method according to claim 159 wherein said predetermined current waveform is periodic and has a magnitude between 10 nA and 1 mA.

164. A method for detection and characterization of one or more medical pathologies within an object under study comprising the steps of:

(a) stimulating such object electrically with a current source;

(b) measuring a plurality of voltages with a plurality of electrodes disposed relative to such object for receiving current from such object;

(c) calculating a plurality of complex impedances, each of said plurality of complex impedances corresponding to a current drive path defined by said current source and one of said plurality of electrodes; and

(d) analyzing said plurality of complex impedances to detect and characterize such one or more medical pathologies, wherein said analyzing constructs a multidimensional representation of the electrical characteristics of a region within such object by solving a continuum electrical model that incorporates nonlinearities.

165. The method according to claim 164 further comprising the step of constructing a multidimensional representation of the electrical characteristics of said object under study using said plurality of complex impedances.

166. The method according to claim 165 further comprising the step of projecting said multidimensional representation into a plurality of three-dimensional spaces.

167. A method for detection and characterization of one or more medical pathologies within an object under study comprising:

(a) stimulating such object electrically with a current source;

(b) measuring a plurality of voltages with a plurality of electrodes disposed relative to such object for receiving current from such object; and

(c) analyzing data received from said plurality of electrodes to detect and characterize such one or more medical pathologies by solving a continuum electrical model that incorporates nonlinearities to construct a multidimensional representation of the electrical characteristics of said object under study.

168. The method according to claim 167 wherein said continuum electrical model comprises Zener-diode elements.

169. The method according to claim 167 wherein said continuum electrical model comprises:

(a) an inductive element;

(b) a capacitive element;

(c) a resistive element; and

(d) Zener-diode elements.