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Glossary of Terminology*

A Mode (-mode): A method of display in which time is represented along the horizontal axis and echo amplitude is displayed along the vertical axis. AB Mode (Amplitude brightness-mode): A method of data presenta• tion on the oscilloscope screen in which one coordinate represents time (depth) and the amplitude of the echo signal is displayed as both a deflection along the other coordinate and as a brightening of the display spot. Absolute Maximum (from AIUM/NEMA Standard): This means the largest possible value of a specified quantity either for an individual instrument or for all instruments of a given generic type. This value shall include effects of inaccuracies and imprecision of the measure• ment process(es) used to determine it. Absolute Minimum (from AIUM/NEMA Standard): This means the smallest possible value of a specified quantity either for an individual instrument or for all instruments of a given generic type. This value shall include effects of inaccuracies and imprecision of the measure• ment process(es) used to determine it. Absorbed Dose: The thermal imparted to matter by of acoustic per unit mass (or per unit volume) of irradiated material at the site of interest. Absorption: The process by which acoustic radiation imparts energy locally to the medium through which it propagates, by conversion of acoustic energy to heat. Absorption contributes to . Acoustic, Acoustical: The qualifying adjectives "acoustic" and "acous• tical" mean containing, producing, arising from, actuated by, related to, or associated with . Acoustic (note 1) is used when the term being qualified designates something that has the properties, dimen• sions, or physical characteristics associated with sound ; acous• tical (note 2) is used when the term being qualified does not desig-

*Selected terms taken from AlUM Recommended Nomenclature [Reflections 6 0),3219801 with permission. Definitions modified from this reference are markedt. 305 306 GLOSSARY

nate explicitly something that has such properties, dimensions, or physical characteristics. Note 1: The following examples qualify as having the properties or physical characteristics associated with sound waves and hence would take acoustic: impedance, output (), energy , medium, signal, transducer. Note 2: The following examples do not have the requisite physical characteristics and therefore take acoustical: method, engineer, symbol, problem, measurement. Note 3: As illustrated in the preceding notes, usually the generic term is modified by acoustical, whereas the specific technical impli• cation calls for acoustic. *: Amplitude reduction of the acoustic signal as a function of time or of propagation distance. Attenuation includes the effects of absorption, , , , and . Acoustic Energy: Mechanical energy transported by an . The units are those of acoustic power times time, the (J) (Watt• second) in standard international units. Acoustic Field: A distribution (in space and time) of acoustic energy. Acoustic Holography: See Holography. : A vector quantity formed by taking the ratio of the instantaneous acoustic at a surface to the instantaneous volume at the surface in an acoustic field. (See also specific acoustic impedance, characteristic acoustic impedance). Acoustic Impedance Match (Colloquial): The condition of equality of Characteristic Acoustic Impedances of contiguous media, avoiding reflection of acoustic energy at the interface (see Impedance Ratio).

*In this (and other similar definitions in this section), the adjective "acoustic" may be deleted when the acoustic context of the term is understood; or it may be replaced by the equivalent term "sonic" or, when appropriate, the more specific adjective "ultrasonic." These terms, which refer to the amplitude, can also be defined in terms of . The choice would be based upon the measurement technique. For example, a hydrophone probe will yield data in terms of sound pressure amplitude, and a thermocouple probe will give data in terms of intensity. The magnitude of this attenuation (or ) depends upon many characteristics of the measurement system, such as the size and orientation of the transducer or transmitting and receiving transducer element, the orientation of the tissues, and electrical signal processing. The acoustic attenuation of or other material in an ultrasound beam is the ratio of the signal received by the transducer relative to the signal that is received when the tissue or other material in the propagation pathway is replaced by a specified lossless medium (water, at a given temperature). GLOSSARY 307

Acoustic Impedance Mismatch: A condition of unequal Characteris• tic Acoustic Impedances of contiguous media, causing reflection of acoustic energy at the interface (see Impedance Ratio). Acoustic Intensity: See Intensity. Acoustic Lens: A refractive element employed to redirect acoustic waves or rays in order to increase or decrease acoustic energy den• sity in a prescribed volume or to modify phase at a receiving transducer. Acoustic Power: Acoustic energy transported per unit time (usually a temporal average is quoted; e.g. I J/s) (See Average Acoustic Power). Acoustic Pressure: The instantaneous value of the total pressure mi• nus the ambient pressure. : Acoustics is the science of sound, including its production, transmission, and effects. Acoustic Shadow: A manifestation of reduced acoustic signal ampli• tude in or returning from regions lying beyond an attenuating ob• ject. It is important to distinguish between acoustic shadows and re• gions of low reflectivity. Acoustic Streamingt: An acoustically generated time-independent transport of fluid within the body of the sonicated fluid or tissue. Acoustic Wave: A mechanical disturbance that progagates through a continuous medium. Acoustic : See Waveform. Acoustic Wavefront: The surface of equal phase in a propagating wave. Acoustic : The acoustic wavelength is the distance between any two adjacent points at which the phase, at the same instant, dif• fers by 21T; it corresponds to the distance traveled by the wave during one cycle; A = clf, where A is the wavelength, c is the , and f is the . For water or tissue at I MHz, the wavelength is approximately 1.5 mm. Amplitude: The magnitude of the envelope of a first-order electrical or acoustic waveform (e.g., voltage or acoustic pressure in linear acoustics. ) Amplitude Modulation Factor: The value of the expression 100 X (IAI - IBI) I IAI, expressed as a percentage, where IAI and IBI are the absolute maximum and minimum of the envelope of a modulated acoustical or electrical carrier (first-order quantity), respectively. Amplitude Modulated Waveform: A waveform in which the carrier wave is modified in amplitude by a signal wave as a means of trans• mitting information. For measurement purposes the AIUM-NEMA 308 GLOSSARY

standard defines it as a waveform in which the amplitude modula• tion factor is greater than 5%. Angle of Incidence: The angle between the axis of an ultrasound beam encountering an interface and the vector normal (perpendicular) to the interface. Attenuation: See Acoustic Attenuation. Attenuation Coefficient: The relative change in the acoustic wave am• plitude (acoustic attenuation) per unit path length in a medium. Commonly employed units are dB/cm, and Np/cm where Np = Neper. Attenuator: A device that reduces the signal by a specified amount, e.g., 10 dB steps. Average Acoustic Power: The power output from an acoustic trans• ducer averaged over a period of time that is either long com pared to, or exactly to, the period of pulses or variations in power. Average Intensity: See Intensity. Axial Resolution: The minimum separation of reflectors, required along the direction of sound travel, such that each can be separately distinguished on the display (same as Depth Resolution, Longitudi• nal Resolution, and Range Resolution). Azimuthal Resolution: The minimum angular separation between ad• jacent reflectors at the same range such that each can be separately distinguished in the display. This resolution is limited by the beamwidth of the transducer at that range of the targets (see Lateral Resolution). B-Mode (Brightness-Mode): A method of display on an oscilloscope screen in which the intensity of the echo is represented by modula• tion of the brightness of the spot and in which the position of the echo, displayed in the x-y plane, is determined from the position of the transducer and the transit time of the acoustic pulse. B-Scan: A misnomer for a B-mode scan or image; scanning with B-mode display. Backscattered Energy: The portion of the incident acoustic energy re• flected from a small (compared to the wavelength) target to• ward the reflector source; to be distinguished from specular reflec• tion, where the reflector dimension may be large compared to the wavelength. Bandwidth: The transmitted bandwidth is the difference in the fre• quencies, Fr and F2, at which the magnitude in the acoustic pressure is 71% (-3 dB) of its maximum value. The pulse-echo bandwidth is the difference in , Fr and F2, at which the magnitude of the pulse-echo response from a planar reflector at a specified range is 50% (-6 dB) of its maximum value. (AlUM Standard for Testing Single Element Pulse-Echo Ultrasonic GLOSSARY 309

Transducers. American Institute of Ultrasound in , 6161 No. May Ave., Suite 278, Oklahoma City, OK 73112.) Beam: The directed acoustic field produced by a transducer. Beam Axis: A straight line joining the points of maximum sound pres• sure amplitude, at increasing distances from the source in the far field, and extending back to the transducer assembly surface. In pulse-echo situations, the above points of maximum spatial pressure amplitude are replaced by the points of maximum pulse-echo re• sponse from a specified reflector. Beam Cross-Sectional Area: The area of that portion of a surface, i.n a plane perpendicular to the beam axis consisting of all the points at which the intensity is greater than X% of the maximum transducer signal in that plane. For beams from therapy equipment X is usually 5%. For beams from diagnostic equipment X is usually larger than 5%, i.e., 10, 25, or 50%. Transmitted Beam Cross-Sectional Area is the area on the surface of a plane perpendicular to the beam axis consisting of all points where the acoustic pressure is greater than 50% of the maximum acoustic pressure in that plane. Beam Cross-Sectional Profile: The sound pressure amplitude distri• bution along a line perpendicular to the beam axis. Beam Divergence: The full angle of beam spread in a particular plane through the beam axis. The orientation of the plane must be specified. Beam Pattern: The directional response pattern of a transducer used for sound emission and/or reception is a description, often pres• ented graphically, of the response of the transducer as a function of the direction of the transmitted or incident sound waves in a specified plane and at a specified frequency. A complete description of the beam pattern of a transducer would require three• dimensional presentation. The beam pattern is often shown as the response relative to the maximum response. [USA Standard S1.1-1971 (R-1960) "Acoustical Terminology" published by Ameri• can National Standards Institute, 1430 Broadway, New York, NY 10018.] Beam Uniformity Ratiot: The ratio of the Spatial Peak-Temporal Average Intensity (SPTA) at the point in the ultrasound field where the temporal average is a maximum to the Spatial Average• Temporal-Average Intensity (SATA) where both quantities are measured in a plane perpendicular to the beam axis (See Spatial Average). Beam Width (Transmission): The transverse distance between points on a specified beam cross-sectional profile where the acoustic pres• sure is a specified fraction of the maximum acoustic pressure on the profile. This may also be expressed as the angle formed between 310 GLOSSARY

lines from the location of these two points to the point of intersection of the beam axis and the surface of the transducer assembly. C-Mode (Constant Range-Mode): A method of display of cross• sectional echo data in which the plane imaged is at a constant range from the transducer and is perpendicular to the interrogating beam. Cathode Ray Tube (CRT): An beam tube designed for two• dimensional display of as a function of their coordinates in space, time, or both. It consists of an electron source (gun), a means for deflecting the electron beam in the x and y directions, and a phosphorous screen upon which the position of the electron beam is visible. The brightness of the display can be modulated by varying the current to the electron source, or the voltage on the grid of the CRT. (Acoustically Induced): A phenomenon produced by sound in liquid or liquid-like media involving bubbles or cavities containing gas or vapor.

Center Frequency: The frequency determined by (F 1-F2 )/2), where F 1 and F 2 are the frequencies used in defining bandwidth. Gener• ally, the frequency at which the amplitude spectrum is a maximum. Centroid of a Surface: The point whose coordinates are the mean value of the coordinates of the surface. Characteristic Acoustic Impedancet: The specific acoustic imped• ance for plane waves in a lossless medium equal to the product (pc) of the undisturbed density and the velocity of sound of the medium. Compressional Wave: A wave motion which is characterized by changes of density in the medium. See as an example. Contact Coupling: Acoustical coupling of a transducer by direct con• tact with the skin, using liquid or gel to exclude air from the space between the transducer and skin. Continuous Wave (cw) Ultrasoundt: A wave of (almost) constant am• plitude which persists for a large number of cycles. Defined in the Canadian and US Ultrasound Therapy Product Standard as a waveform in which the amplitude modulation factor is less than or equal to 5%. Coupling Methods: The method by which ultrasound is transmitted from a transducer to the subject and vice versa. These methods in• clude 1) Contact Coupling, 2) Immersion Coupling and 3) Liquid Coupling. Crystal: A colloquial term for the piezoelectric element of the trans• ducer. Most piezoelectric elements are made of poly-crystaline materials. D Mode: A display method in which only moving targets are displayed through their Doppler frequency shifts. If a scan is made it is referred to as scanned D mode . GLOSSARY 311

Damping: Any mechanism which removes mechanical or electrical en• ergy from the transducer. This can include internal absorption in the transducer as well as electrical or mechanical loading of a trans• ducer to produce a more rapid decrease in the trailing edge of the transmitted acoustic pulse and the echoes received. Damping is used to improve axial resolution. Dead Time: The time interval between the start of the complex and the arrival of the first identifiable echo. The dead time is determined primarily by a characteristic of the receiving and may be controlled by minimizing the amplitude of the transmit• ter pulse reaching the amplifier and adjusting the recovery time of the amplifier. : A unit used for expressing the ratio of two like quantities, such as electrical signal amplitudes or sound . The decibel unit is only a relative measurement of the intensity of signals or sound en• ergy levels and does not specify any definite voltage, power or inten• sity, unless one of several conventional reference levels is used and stated. The equations for expressing the decibel are as follows: n(dB) = 20 loglO (Pl/P2); n(db) = 10 loglO (W 11W2); n(dB) = 20 loglO (V1N 2); n(dB) = 10 loglO(I I/12); where n is the number of , PI and P2 designate two ultrasonic pressure levels, WI and W 2 designate two power levels, VIand V 2 designate two voltage lev• els, and 11 and 12 designate two intensity levels. Delivered Acoustic Energy: The product of acoustic power and expo• sure time at the prescribed site. Delivered Acoustic Pulse Energy: See Energy per pulse. Depth: The distance along the sound path from the point of entry into the patient or other object being examined to the point of interest. Distance along the time axis of the display is assumed to correspond proportionally to depth in the tissue. Depth of Focus: The distance along the beam axis, for a focusing transducer assembly, from the point where the beam cross• sectional area first becomes equal to two times the focal area to the point beyond the focal surface where the beam cross-sectional area again becomes equal to two times the focal area. Specify whether the depth of focus is measured in one way or round trip (pulse-echo) conditions. (See also Focal Zone.) Diffraction: A redistribution in space of the intensity of waves that re• sults from the presence of inhomogeneities causing variations of the amplitude and/or phase of the waves. Thus the ultrasonic field that appears in and near the geometric shadow of an obstacle typically has a complex spatial distribution which is explained by diffraction. Directivity Pattern: A beam pattern expressed in polar coordinates. : The dependence of propagation speed upon frequency. Dispersion is responsible, to a small extent, for the changes in the shape of a pulse waveform as it propagates. 312 GLOSSARY

Display Format: The manner in which information is presented to the diagnostician, e.g., A-mode, B-mode, C-mode, etc. Displayed Beam Width: The length of the displayed image of a point target, measured normal to the direction of the axis of propagation. See also Beam Cross-Sectional Area and Pulse-Echo Response Profile. : A shift in observed frequency (and wavelength), caused by relative motions among sources, receivers, and the propa• gation medium, when there is a component of relative motion paral• lel to the beam axis. Doppler Frequency Shift: The difference between the frequencies of waves, transmitted and received, being proportional to the speed of relative motion between the transducer(s) and the target [reflector( s)]. Doppler Ultrasound: Application of the Doppler effect in ultrasound to detect movement of a reflecting boundary relative to the source from a change in frequency of the reflected wave. Doppler Velocity Signal: A signal whose instantaeous voltage, cor• rected for the angle between the beams, is proportional to the instan• taneous Doppler frequency shift, derived by a frequency-to-voltage conversion of the Doppler signal. Dosimetry: The quantitative determination of spatial and temporal field distributions in media of interest (usually tissues). Duty Factor: The product of the pulse duration and the pulse repeti• tion rate. Dynamic Imaging: Imaging of an object in motion, a technique which is frequently referred to as imaging at a real time rate. Echo: Acoustic signal received from scattering elements or a specular reflector. Echo Ranging: A technique for measuring distances in materials of known acoustic velocity by measuring the transit time for the sound to propagate from the transducer to the target and return. Echo ran• ging techniques, in particular pulse-echo ultrasound, form the basis for most of the ultrasonic visualization systems. Echo (Signal) Shaping: Image modification in which the echo wave• form is changed using techniques such as limiting and differentiation. Echo Strength: See Magnitude of Echoes. Energizing Pulse (Transmitter Pulse): An electrical pulse used to ex• cite (or "shock") an ultrasonic transducer. Frequently, the pulse is a "spike" whose rise time is short compared to the natural period for the fundamental resonant of the transducer. Energy per Pulse: The ratio of the average acoustic power to the pulse repetition rate measured in . GLOSSARY 313

Entrance Beam Dimensions: The dimensions of the beam cross• sectional area where the beam enters the pattern. For contact trans• ducers these dimensions can be taken as the dimensions of the radiating element if so stated. Envelope: A continuous curve connecting the peaks of the successive cycles of a waveform. Exposure Time: The total amount of time the transducer assembly is delivering ultrasonic energy to the subject. In a pulse waveform, this includes time between pulses. Far Field (Fraunhofer Zone): That region of the field in which the acoustic energy now along the beam axis proceeds essentially as though coming from a located in the vicinity of the transducer assembly. (Note: For an unfocused transducer assembly, the far field commonly is ascribed to ranges greater than Sf7rA, where S is the radiating cross-sectional area and A is the acoustic wavelength in the medium.) Focal Area: The area of the focal surface. Focal Length: The axial distance from the centroid of the radiating surface of a focusing transducer assembly to the focal surface. Focal Surface: The surface containing the smallest of all beam cross• sectional areas of a focusing transducer assembly. Focal Zone: The volume lying within the depth of focus and the perim• eters of the beam cross-sectional areas. Focusing Transducer Assemblyt: A transducer assembly for which the ratio of the smallest beam cross-sectional area to radiating cross-sectional area is less than 0.5. Fractional Bandwidth: The bandwidth divided by the center frequency. Fraunhofer Zone (Far Field): See Far Field. Frequency: Number of cycles of a periodic process per unit of time, usually expressed in (Hz), or multiples such as Megahertz (l MHz = 106 Hz). Fresnel Zone (Near Field): See Near Field. Gain: The ratio of the output to input of an amplifying system, gener• ally expressed in decibels (dB). Geometrical Focal Length: The distance along the beam axis from the center of the face of the transducer or lens to the geometrical focal point. Geometrical Focal Point: The point of intersection of the greatest number of rays from the active transmitting element(s) of the trans• ducer. Each ray is perpendicular to a small element of given surface area and may be refracted by lenses and/or renected by mirrors. Gray Scale: A term describing the property of a display in which inten• sity information is recorded as variations in the brightness. The 314 GLOSSARY

number of intensity levels differing in luminence by v'2 or the num• ber of distinguishable gray-scale levels with a specified test pattern is a measure of the output of the display. The dynamic range of the signal input to the display amplifier(s) is related to the output gray scale luminence by the gray scale transfer function. Log• arithmic and other nonlinear are used to provide dynamic range compression and modify the grayscale transfer function. Half-Power Distance: The distance an ultrasound beam must travel in a medium to reduce its power to one-half of its original value (See Half Value Layer.) Half-Value Layer: A layer of a specified substance whose thickness is the half power distance. Hard Copy: A permanent visual record on materials such as paper or film, as opposed to an image on an oscilloscope screen or magnetic tape. : A whole number multiple of the of a periodic quantity. For example, the second harmonic of a 1 MHz wave is at 2 MHz. (Subharmonics also are possible; e.g., at V2, 1/3 , etc. of the fundamental frequency.) Hertz: The standard unit of frequency equal to one cycle per second. Holography: A two-stage process of imaging. The object to be visual• ized is uniformly irradiated with ultrasound (or light) and the re• flected or transmitted waves are sampled over a large area. The re• sulting image or hologram is generated by recording the sum of the reflected or transmitted waves and a reference wave or signal. This resulting image is an interference pattern where the contours are lines of constant phase. Although holograms contain three• dimensional data, they are usually reconstructed in acoustics so that only two dimensions are displayed. Immersion Coupling: A method of coupling an ultrasonic transducer to an object by placing both in a bath of the coupling medium. Impedance: See Acoustic Impedance. Impedance Ratio: The ratio Z2/Zj, where ZI and Z2 are the specific acoustic impedances of two contiguous media, respectively. Instantaneous Acoustic Power: The acoustic power at an instant in time. Intensity: A quantity related to acoustic power transmitted in a specified direction per unit area normal to this direction at the point considered. The particular intensity intended should be specified as defined below. Instantaneous Intensityt: The instantaneous acoustic power trans• mitted in a specified direction per unit area normal to this direction at the point considered. For measurement purposes, this point is re• stricted to where it is reasonable to assume that the acoustic pressure GLOSSARY 315

and are in phase, viz, in the far-field or the area of the focus. Under such conditions, the intensity can be expressed as: I = p 2/2pc, where P is the instantaneous acoustic pressure, p is the density of the medium, and c is the velocity of sound in the medium. Pulse Average Intensity: The time-average of instantaneous inten• sity at a point in space, when averaged over the pulse duration. (May be calculated approximately as the ratio of the temporal av• erage intensity to the duty factor.) Spatial-Average Intensity: The same as spatial average-temporal average intensity. Generally, this parameter is used when speci• fying the intensity for continuous wave (cw) ultrasound. Spatial Average-Pulse Average Intensity (SAPA): The pulse aver• age intensity averaged over the beam cross-sectional area. (May be calculated as the ratio of acoustic power to the product of duty factor and beam cross-sectional area.) Spatial Average-Temporal Average Intensity (SATA): The tempo• ral average intensity averaged over the beam cross-sectional area. (May be calculated as the ratio of acoustic power to the beam cross-sectional area.) Spatial Peak-Pulse Average Intensity (SPPA): The value of the pulse average intensity at the point in the acoustic field where the pulse average intensity is a maximum, or is a local maximum within a specified region. Spatial Peak-Pulse Average Intensity (SPPA)t: The value of the pulse average intensity at the point in the acoustic field where the pulse average intensity is a maximum, or is a local maximum within a specified region. Spatial Peak-Temporal Peak Intensity (SPTP): The value of tem• poral peak intensity at the point in the acoustic field where it is a maximum, or is a local maximum within a specified region. Temporal Average Intensity: The time-average of instantaneous intensity at a point in space; equal to the mean value of the instaneous intensity at the point considered. For non-auto• scanning systems, the average is taken over one or more pulse rep• etition periods. For auto-scanning systems, the instantaneous in• tensity is averaged over one or more scan repetition periods for a specified operating mode. Temporal Peak Intensity: The peak value of the instantaneous in• tensity at the point considered. Interface: The surface forming the boundary between two media hav• ing different properties. Interference: The phenomenon in which two or more waves of the same or harmonically related frequency(ies) add together or cancel each other, according to their amplitudes and phases. 316 GLOSSARY

Isotropic: Having nondirectional properties (i.e., physical properties that are independent of direction). For example, the speed of sound is not a function of the direction of propagation through an isotropic material. In contrast, the velocity of sound in muscle differs when propagating parallel to the fibers than when propagating at right an• gles to the fiber orientation; thus, muscle is anisotropic. Lateral Resolution: The minimum separation of reflectors in a direc• tion normal to the beam axis at which the individual reflectors can be distinguished in the display (see Azimuthal Resolution). Limiting (Clipping): A technique that does not permit the voltage level to exceed a specified value. Linear Scan: The motion of a transducer at constant speed along a straight line at right angles to the beam. Liquid Coupling: A technique using a liquid, such as water, to couple the transducer to the object (see Coupling Method). The method is used with focused transducers so that the focus can be moved with respect to the tissue. Longitudinal Wave: Wave motion for which the in the medium is normal to the wavefront. M-Mode (Motion-Mode): A method of display in which tissue depth is displayed along one axis and time is displayed along the second axis. The second axis displays time at a rate of physiological interest. M-mode is used frequently to display echocardiographic data when the changes in range of echoes corresponding to wall and valve motion are displayed as a function of time. The intensity of the ech• oes may be displayed by modulation of the brightness of the CRT im• age, or the shading of the hard copy. Megahertz: One million cycles per second (106 Hz); see Hertz. Monochromatic: Having a single frequency; from analogy with light. Near Field (Fresnel Zone): A region of an acoustic field lying between the transducer and an axial point at approximately 0.7 times the range to the last axial pressure maximum. For a plane disc trans• ducer this pressure maximum occurs approximately at a range of ShrA, where S is the radiating area of the transducer and A is the wavelength. In the near field it is necessary to consider both ampli• tude and phase in describing the field parameter distributions. Neper: A logarithmic unit expressing the amplitude ratio of two like quantities equal to the natural logarithm (In = loge) of the ampli• tude ratio of the two quantities: In AI/A2 = amplitude ratio in Nepers [1 Neper (Np) = 8.686 decibels (dB)] On-Time: The sum of pulse duration during the total time that the transducer is acoustically coupled to the subject or other object of in• terest. Contrasted with "off-time," which is the sum of intervals be• tween pulses when the transducer is not electrically driven. Total time = on-time + off-time. GLOSSARY 317

Peak Instantaneous Intensity: See Intensity. Peak Intensity: See Intensity. Peak Spatial-Average Temporal Intensity: See Intensity and Spatial Peak-Temporal Average Intensity (SPTA). Peak Spatial-Peak Temporal Intensity: See Intensity and Spatial Peak-Temporal Peak Intensity (SPTP). Peak Temporal-Average Spatial Intensity: See Intensity and Spatial Average-Temporal Peak Intensity (SA TP). Phantom: A passive device that simulates some parameters of the hu• man body and allows meaningful measurements of ultrasound sys• tem parameters or visualization of simulated anatomical features. Piezoelectric Effect: The property, exhibited by all electrically asym• metrical crystals, of generating electrical potentials when mechani• cally stressed. Conversely, these crystals generate mechanical strains when electrically stressed. This effect is the basis of electromechani• cal transduction of energy in transducers. Power (See also Acoustic Power and Ultrasonic Power): The quantity of energy flow per unit time, expressed in Watts. One Watt is equiva• lent to a rate of flow of energy of 1 joule per second. Pressure: See Acoustic Pressure. Pulse Average Intensity (From AIUM/NEMA Standard): The time• average of intensity at a point in space, when averaged over the pulse duration (this quantity may be calculated as the ratio of the temporal average intensity to the duty factor). Pulse-Average Ultrasonic Power: See Ultrasonic Power. Pulse Durationt: The time interval beginning when the absolute value of the acoustic pressure exceeds X% of the maximum absolute value of the acoustic pressure and ending at the last time the abso• lute value of acoustic pressure returns to this value. This term is preferable to pulse length. For therapy devices X = 10%; for diag• nostic devices X may be larger, for example, 32% (-10 dB). Pulse-Echo Technique: See Echo Ranging. Pulse Length: See Pulse Duration. Pulse Repetition Frequency (PRF): See Pulse Repetition Rate. Pulse Repetition Period: The time interval between the same point on the waveform of two successive pulses. Pulse Repetition Ratet: The repetition rate of the pulses of a pulse• echo system, or the repetition frequency of the amplitude modu• lated waveform, expressed in Hz; the inverse of the pulse repeti• tion period. Pulse Waveform: A waveform in which B (defined in the amplitude modulation factor) is equal to zero for a time greater than the pulse duration. 318 GLOSSARY

Radial Mode: A mode of of an acoustic wave propagating radially in a disk transducer. It does not contribute to the desired acoustic output of the transducer, and therfore is regarded as a para• sitic oscillation. Radiating Cross-Sectional Area: The beam cross-sectional area at the surface of the transducer assembly. Radiation Force: The constant unidirectional force exerted on an in• terface by an incident acoustic wave. The force results from the transfer to the second medium of carried by the wave to the interface. The term is a misnomer for this force. Real-Time: A characteristic of a system whose output keeps pace with changes in input. Real-Time Display: A display for which the image is continuously re• newed, keeping pace with changes in the object, and in which stor• age or processing time does not delay appreciably the image presentation. Real-Time Ultrasonic Visualization System: A system presenting real-time ultrasonic images. Real-time displays present the acoustic data at the time it is received without a discernible delay for proc• essing, and at a frame rate that is sufficient to enable the operator to appreciate relative motion between the tissue and the transducer. The high data rate characteristic of real-time displays results in the continuously updated image analogous to television, so that moving structures, such as the heart and heart valves, can be visualized. The high frame rate is also useful when using the scanning system in the search mode. Reflected Acoustic Pulse: See Echo. Reflection: Reversal of the direction of propagation of a component of a wave that is propagating in one medium and encounters an ex• tended interface with another medium of different acoustic proper• ties. The amplitude of the reflected wave is related to the ratio of the characteristic acoustic impedances across the interface. The angle of the reflection from a plane interface that is large compared to the acoustic wavelength is equal to the angle (between the and normal to the interface) of the incident wave, in accordance with Snell's Law. Reflection Coefficient (Amplitude): The ratio of the reflected to the incident wave pressure amplitudes at normal incidence R = (Z2-Zr)/(Z2 + Zr), where Zr and Z2 are the characteristic acoustic impedances of the first and second media, respectively. Reflection Mode Imaging: A technique that makes use of the reflected acoustic energy to produce the image data. Also called echo ranging. GLOSSARY 319

Refraction: The phenomenon of changing the direction of propaga• tion as an obliquely incident acoustic wave propagates from a me• dium of one acoustic velocity to a second medium of differing acous• tic velocity. Registration Accuracy: A of the display related to the accuracy of representation of the position of acoustic targets. It generally re• fers to display errors produced by refraction, position sensing, and computation devices for the B-mode scanning arm, or inadequacy of the CRT spot in representing the location of echo-producing interfaces. Relaxation: A class of processes in which acoustic energy is absorbed in a medium. Resolution: A measure of the ability of a system to display distinguisha• ble images of two closely spaced structures as discrete targets. (Also see Azimuthal Resolution, Axial Resolution, and Lateral Resolution.) Reverbation: The phemonenon of multiple reflections within a closed system. This phenomenon causes echoes to be misplaced in the display, thereby presenting false information. Multiple reflections may be identified in an image by moving the transducer relative to the object. The multiple reflections will move faster than the primary echoes because the primary echoes move a distance on the display which is equivalent to twice the incremental distance, while the first multiple reflection moves a distance equivalent to four times the increment. Rise Time: The time taken for a pulse or echo amplitude to increase from 10% to 90% of its peak value. Sagittal Plane: Anyone of a set of anterior-posterior planes parallel to the long axis of the body. Scale Factor: Generally, a transfer function between the input and out• put of a system. In ultrasound diagnosis, it commonly refers to the ratio of the displayed size of an object to the real size of the object. Scan: The moving of an acoustic beam to produce an image for which the transducer and the display movements are synchronized in space and time. Scan Repetition Frequency: See Scan Repetition Rate. Scan Repetition Rate: The repetition rate of a complete frame, sector, or scan. The term applies to automatic scanning systems only. Scanner: A device to move and focus an acoustic beam relative to a tar• get. This is accomplished by using the beam steering and focusing ca• pability of systems or by mechanically moving a transducer. Scattering: The diffuse reflection, refraction, or diffraction of ultrasound in many directions from irregular surfaces or inhomoge- 320 GLOSSARY

neities within a medium. The discontinuities are dimensionally com• parable to or smaller than an acoustic wavelength; e.g., small spheres in the path of a give rise to complex reflection, refraction, and diffraction behavior called scattering. In an ultra• sonic visualization system, by far the largest number of reflective ob• jects in a specimen are scatterers. Visualization of scattering sources provides a much more complete picture than visualization of specu• lar reflections. For this reason, images based on scattered acoustic energy are easier to interpret, but systems with higher sensitivity and greater dynamic range (gray scale) are required to display the weak scattered signals. Sector Scan: A system of scanning in which the transducer or trans• mitted beam is rotated through an angle, the center of rotation being near or behind the surface of the transducer. Sensitivity: The minimum signal that can be satisfactorily detected, generally limited by the input level of the system. Shear Wave: Wave motion with particle movements perpendicular to the propagation direction. Shear waves propagate in , but are highly attenuated in liquid systems. Shear waves are generated when a longitudinal wave impinges obliquely on - inter• faces and partially account for the heating of the periosteum and bone at this location. Short Axis Scan: A scan parallel to the short axis of the heart obtained from cross-sectional with a transducer scanning a plane at right angles to the long axis of the heart (base to apex). Side Lobe: A diffractive characteristic of an acoustic beam in which secondary, off-axis maxima occur in the near or far acoustic field, or in the focal zone. The presence of side lobes tends to cause target ambiguity and limit the resolution. Signal (Electrical): The information content of the electrical variation in voltage or current in a circuit. Signal-to-noise ratio is a statement of sensitivity. Single Sweep Scan: A scan mode in which only a single pass of the transducer over the tissue to be examined is used. This scan mode may be used where relative motion of tissues could be expected and where this motion would obscure the desired detail. : Applied to , the term "sonar" is the generic term for echo ranging. From the acronym SOund NAvigation Ranging. Sonography: Any imaging method using sound and yielding a graph• ical representation of the subject. This is a more inclusive term than echography inasmuch as transmission sonography is also included. Sound Pressure Amplitude: The deviation from the ambient value of the pressure in a medium resulting from the presence of an acoustic wave. It usually refers to the peak instantaneous wave pressure, but GLOSSARY 321

also may be the general instantaneous, or root-mean-square (rms) pressure. The pressure amplitude of an acoustic wave may be meas• ured with a linear device such as a hydrophone. In a plane progres• sive (cw) wave, intensity (I) and maximum pressure amplitude (P) are related by I = (P2/2pc) 112, where p and c are the mean density and speed of sound of the medium, respectively. Spatial Average: See Intensity. Spatial Average-Pulse Average Intensity (SAPA): See Intensity. Spatial Average-Temporal Average Intensity (SAT A): See Intensity. Spatial Peak-Temporal Average Intensity (SPT A): See Intensity. Spatial Peak-Temporal Peak Intensity (SPTP): See Intensity. Specific Acoustic Impedance: The ratio of instantaneous acoustic pressure to instantaneous particle velocity. For plane progressive wave in a lossless medium, the specific acoustic impedance is nu• merically equal to the characteristic acoustic impedance. Speed of Soundt: The speed of sound, c, in a fluid medium is deter• mined by the properties of the propagation medium; c = (Ka/p)1I2, where p is the mean density of the medium and Ka is the adiabatic . The speed of sound is the product of the frequency (f) and the wavelength (A): c = fA. Also, c = Zip, where Z is the characteristic acoustic impedance (a scaler quantity). Spiral C-Mode Section Scanner: Apparatus to perform scanning in a spiral motion so that from a selected site on the body surface, scans are made corresponding to sections parallel to the surface at varying depths. Superposition Principle: If a linear physical system is acted upon by a number of independent influences, the resultant influence is the sum of the independent influences. Any linear wave phenomenon can be analyzed by simple addition of scalar contributions from some distribution of simple sources, properly selected in phase and ampli• tude to represent the physical situation. The vector quantities can then be determined from the basic equations by taking gradients. This principle is applied in phased array transducers to generate the appropriate wave amplitude and phase relationships throughout the field. TM-Mode (Time-Motion): See M-Mode. Temporal Average Intensity: See Intensity. Temporal-Average Ultrasonic Power: See Average Acoustic Power. Temporal-Maximum Ultrasonic Power: U sed in US Ultrasound Therapy Product Standard name for pulse-average ultrasonic power (see Ultrasonic Power). Temporal Peak Intensity: See Intensity. Test Object: A passive device that provides echoes and permits evalua• tion of one or more parameters of an ultrasound system, but does 322 GLOSSARY

not necessarily duplicate the acoustical properties of the . See also Phantom. Through-Transmission Imaging: The process of imaging by trans• mitting the sound field through the specimen and receiving the transmitted energy on a far surface or a receiving transducer or ar• ray. See also Holography. Transceiver: A transducer used both for transmission and reception of acoustic energy. This is the customary configuration for ultra• sound visualization equipment. (In contrast, typical cw Doppler de• vices are examples of instruments that use separate and receivers.) Transceiver Voltage Response: The ratio of the amplitude of the en• ergizing pulse with the transceiver attached, to the amplitude of the echo from a perfect-planar reflector. Transducer: A device capable of converting energy from one form to another. Specifically in ultrasonics, the device used to convert electri• cal energy to mechanical energy and, reciprocally, to convert me• chanical energy to electrical energy. If, in the application, the device performs both functions, the term may be left unqualified. If the de• vice is used only to transmit or to receive, the device should be referred to as the "transmitting" or "receiving" transducer. Transducer Assembly: That portion of a fully assembled ultrasonic di• agnostic product designed to emit and/or receive ultrasonic radia• tion and including one or more ultrasonic transducers and any asso• ciated housing. Transducer Dynamic Response: See Dynamic Response. Transition Zone: That portion of the acoustic field between Fresnel zone (near field) and the Fraunhofer zone (far-field) that encom• passes the last maximum occurring along the beam axis. The transi• tion zone has no distinct boundaries, but is sometimes referred to in the literature. Transmitted Acoustic Pulse: The acoustic pulse transmitted into the coupling medium as a result of the applied energizing pulse. Transmitter Pulse: See Energizing Pulse. : See Shear Wave. Ultrasonic Intensity (also Intensity): Ultrasonic power per unit area. Ultrasonic Shadow: See Acoustic Shadow. Ultrasonic Power: See also Acoustic Power and Power. In the Cana• dian and US Ultrasound Therapy Product Standards, Ultrasonic Power is defined as "the total power emitted in the form of ultrasonic radiation by the applicator averaged over each cycle of the ultrasonic radiation carrier wave". Pulse-average (or temporal-maximum), ultrasonic power is equal to one-half the instantaneous power, and is also numerically equal to the temporal average ultrasonic power of a GLOSSARY 323

cw waveform having the same instantaneous power. Temporal aver• age ultrasonic power is the time average of the instantaneous power at a point in space. Ultrasonogram: Any image obtained from ultrasonic examination methods. The term may be qualified by adjectives appropriate to the field of application. The term includes both echograms and transsonograms. Ultrasound: Acoustic radiation at frequencies above the range of hu• man (conventionally, above 20 kHz). Unipolar Pulse or Waveform: A waveform that has either positive or negative excursions from the baseline, but not both. A unipolar waveform can be produced by rectification of radiofrequency signals. Velocity of Sound: See Speed of Sound. The term "velocity" implies both direction and speed; the term "speed of sound" should be used where direction is of no concern. Signal: The rectified and often filtered echo signals in an ultra• sonic visualization system generally are referred to as "video signals" by analogy with television nomenclature. Watt per Square Centimeter (W/cm2): The unit of intensity (104 W/m2). Wave: See Acoustic Wave. Waveform: The representation of an acoustical or electrical parame• ter as a function of time in a rectangular coordinate system. Wavelength: See Acoustic Wavelength. Subject Index

A power, 78-80, 183-185, 292, 293,299 Abdomen, 159-167 instantaneous power, 183 Absorbing target, 85, 86 temporal average ultrasonic Absorption, 20-23 power, 79, 183, 184 coefficient, 37, 118, 196 temporal maximum Acoustic ultrasonic power, boundary layers, 55-57 183-185 holography, 222,223 temporal peak ultrasonic im pedance, 5 power, 79 intensity, 78, 241, 286, 287, 299 radiation, (see Ultrasound, effective intensity, 186 characteristics of, spatial average temporal ultrasonic radiation) average (SAT A), 78-80, shadows, 225 105-110,288-290 velocity, 227, 253-258 spatial average temporal peak Acupuncture, 294 intensity (SA TP), 105 Air filters, 238 spatial peak intensity of pulse Airborne ultrasound, 121 (SPI), 288, 289 AlUM, 298, 299 spatial peak pulse average bioeffects statement, 286 (SPPA), 79, 80 A-mode operation (see Amplitude• spatial peak temporal average mode operation) (SPT A), 78-80, 288-290 Amplitude-mode operation, 144, spatial peak temporal peak 216-218 (SPTP) 79, 80, 288-290 A-mode test, 261-264 therapeutic intensities, 195, gain switch, 223, 224 196 Amplitude-modulated (wave) (see microstreaming, 49, 55-64, 70 Pulse)

325 326 SUBJECT INDEX

Analog scan converter, 244, 245 Cavitation, 36, 70, 71, 118, 119, , 167, 168 200,201 Arteries, 176, 177 collapse cavitation (see Aspiration, 294 Transient cavitation) nuclei,71 B stable, 70, 119, 202 transient, 70-90, 119, 202 Bandwidth, 240, 241 Central nervous system, 122, 123 Beams, 10, 11 Chest, 151-160 angle, 225 Chiropractors, 300 (see also area, 186 ) axis, 187 Consumer devices, 281 diameter, 14 Continuous wave, 183,222 divergence, 188 Contrast enhancement, 223 non-uniformity ratio (BNR), Coupling medium, 203, 227, 228 193 pattern, 12,240,241 D spreading, 10-18 width,217 Dental scalers, 295 ultrasound, 10, 11 Diagnostic ultrasound, 77 Biological effects (see Ultrasound biological effect levels, 109, 110 biological effects) clinical applications, 141-180 Biological effects curve (see abdomen, 160-171 Threshold curve) , 159, 160 Biliary tract, 166-168 chest, 151-160 Biomacromolecules, 128-133 extremities, arteries and Biparietal measurement, 226 veins, 178 Bladder, 176 head, 144-149 Blood flow stasis, 124, 125,201 neck, 149, 151 B-Mode (see Brightness mode pelvis, 171-178 operation) clinical significance, 142-144 Bragg diffraction theory, 27 coupling medium, 227 , 144-146 distance measurement, 225 Breast, 159, 160 gain, 217 Brightness mode modulation, imaging, 145,218,220,230, 218-250 245-248,258-270 B-mode registration test, output levels, 110 264-270 quality assurance, 215-280 B-scanner (see B-scan equipment) receiver, 243, 244 B-scan equipment, 146,215-280 resolution, 217 scanning technique, 224-227 standards, 288-291 c surveys, 288-290 Calorimetry, 94-96 ultrasound image, 216 Cardiac mode (see Time-motion Diathermy (see Therapeutic mode) ultrasound) Carotid artery, 151 Digital caliper, 226 SUBJECT INDEX 327

Digital scan converter, 245 H Dispersion, 23-25 Doppler "Half-value" thickness, 196 Doppler devices, 107, 108, 220, Hardcopy, 230-238 288,289 Head, 144-149 pulsed Doppler, 150 Heart, 151-158 Doppler effect, 27, 222 High-audible frequency noise, Dynamic range, 243 119, 120 Holography (see Acoustic holography) E Hospital electrical noise, 236, 237 Echo-cardiography (see Heart) Principle, 11 Echoes, 217 Hydrophones (see Ultrasound Education, 296, 297, 300 measurement techniques) Effective intensity (see Acoustic Intensity) I Extremities, 176, 177 Industrial ultrasonic equipment, Eyes, 146-149 119, 120 Insects, 121 F International activities on standards, 297, 298 Fallopian tubes, 175, 176 Intensity (see Acoustic intensity) Far field (see Ultrasound, Intra-organ structure, 225 characteristics of), Fetal, 171-175 fetal growth, 173, 174 K Focal lesion, 46 Kidneys, 162-164 Focused ultrasound (see Ultrasound, characteristics L of) Fraunhoffer region (see , 161, 162 Ultrasound) Logic lock up, 224 Frequency, 3, 217 Lymph nodes, 170 Fresnel region (see Ultrasound, characteristics of, near field) M

G Matching, 20 Measurement techniques (see Gain (see Diagnostic ultrasound, Ultrasound measurement gain) techniques) Gall bladder, 165-167 Menieres disease, 293 Globe, 146-148 Miniature hydrophones (see Gray bar, 230 Ultrasound measurement Gray-scale (see Diagnostic techniques) ultrasound, imaging) M-mode (see Motion-mode Guidelines for safety, 282, 296, operation; time-motion 297 mode) 328 SUBJECT INDEX

Mode conversion, 20 Propagation Motion-mode operation, 152-159 properties of mammalian Multi-image 233-236, 238 tissues, 196, 197 velocity, 3, 118 Prostrate, 176 N Pulse, 38, 183,216 National standards, 298-300 duration, 38, 217 Far field (see Ultrasound) repetition rate, 105 Neck, 149-151 Pulse-echo, 216-280, 288 Neoplastic tissue, 125, 126 transducer array, 8-10

Q o Quality assurance Operators of ultrasound devices, diagnostic ultrasound, 215-280 297-300 A-mode test, 261-264 Optical measurement techniques analog scan converter test, (see Ultrasound 258-260 measurement techniques) B-mode registration test, , 149 264-270 , 175, 176 equipment operation, 222-237 p gray-scale test, 260, 261 hardcopy care, 230-236 , 164, 165 logic lock up, 225 Parathyroid, 149-151 potential hazards, 227-229 Patency evaluation, 178 routine preventive Pelvis, 171-178 maintenance, 237-239 Pericardial effusion, 152-154 system performance testing, Period, 3 239,250 Periosteal, 196-200 transducer axial resolution Peritoneal space, 170, 171 test, 268-270 Phaco-emulsification, 294 warm-up procedure, 229, 230 Phantom, 250 therapeutic ultrasound, Phonophoresis, 202 191-195 Physiotherapy, 300 (see also R Therapeutic ultrasound) Piezoelectric Radiation force, 49-54, 69 materials, 8, 118 pressure, 49, 50 crystal, 193,216,281 torque, 49, 54,55,69, 70 element, 9, 10 Real-time (see Diagnostic transducer, 117, 182 ultrasound, imaging) Pleural space, 158 Receiver, 243 Polaroid images, 232, 233, 237, Reciprocity calibration, 101, 102 238 Reflection, 18-20 Power (see Acoustic power) reflecting target, 83-85 Preventive maintenance, 237-239 reflection coefficient, 19 SUBJECT INDEX 329

Reflectors (see Echoes) exposure time, 193, 194 Refraction, 18-20 power output levels, 105, 193, Regulation (definition), 282 194,292,293 Relaxation, 22 standards, 184-193, 291-293 Resolution, 217, 224, 240-242 Thermal mechanisms, 37-49 Threshold, 122, 123 S mammalian brain, 122, 123 cat liver, 123, 124 Safe-use guidelines, 296, 297 Threshold curve, 43, 110, Scanning arm stability, 238, 239 285-287 Scanning techniques 224-227 , 149 Scattering, 20-27 Time-motion mode, 218, 219 Scrotum, 177, 178 Tissue regeneration, 202 Sensitivity, 243 Transducers, 7-18, 240-243, 299 Service logs, 274 axial resolution test, 268-270 Sokoloff camera, 222 bandwidth, 240, 241 , 165, 166 case, 242 Standard,283, 287-296, 298-300 certification, 242, 243 dentistry, 295, 296 circular, 11 diagnostic ultrasound, 288-291, doppler, 222 298-300 focusing, 87, 88 emission, 287-296 medical, 8-10 exposure, 287 ocular, 11, 12, 191 international, 297, 298 pulsed, 15-18 national, 298-300 quartz, 102, 103 philosophy, 282-284 sterilization, 229 surgical devices, 293, 294 therapy devices, 291-293, u 298-300 Stress mechanisms, 49-70 Ultrasound-biological effects, Surgical applications, 293, 294 117-139,284-287,292,293 Synergism, 125, 126 biomacromolecules, 128-133 cells, 126, 127 tissues, 121, 126 T blood stasis, 124,292 Test object, 250 central nervous system, 122, AlUM 100 mm, 251-258 123 liquid, 253-258 liver, 123, 124 Testes, 124 microorganisms, 126, 127 Therapeutic ultrasound, 77, neoplastic tissues and 181-214 synergism, 125, 126 applications, 206 organs, 121-126 contraindications, 207, 208 testes, 124 devices, 182-191 tissue regeneration, 202 dose, 2 whole-body radiation, 120, 121 effective radiating area (ERA), insects, 121 188 vertebrates, 120, 121 330 SUBJECT INDEX

Ultrasound, characteristics of, laboratory calorimetry system, 1-34 94-96 absorption in biological portable thermal system, 96, 97 materials, 195-203 Ultrasonic waves (see Waves, far field, 12, 13, 187, 190 acoustic) focused ultrasound, 44-46, 241, Ultrasound, biophysical 242 mechanisms, 35-75 near field, 13-15, 187, 190 cavitation, 36, 70, 71 transmission in biological thermal mechanisms, 37-49 materials, 195-203 stress mechanisms, 36, 49-70 ultrasonic radiation, 11-18,35 Ultrasound diagnostic devices (see ultrasound beams (see Beams) Diagnostic ultrasound) ultrasound field, 186 Ultrasound therapy (see unfocused ultrasound, 44 Therapeutic ultrasound) wave phenomena, 186 Ultrasound wave (see Waves, Ultrasound devices, 281-301 acoustic) calibration, 296-300 , 171-175 performance tests, 296 Ultrasound power (see Acoustic power) v Ultrasound, standards, regulations, and guidelines, Veins, 176, 177 281-304 Vertebrates, 120, 121 Ultrasonic drill, 294, 295 Ultrasonic measurement techniques, 77-116 w miniature hydrophones, 103-105, 188 Warmup procedure, 229, 230 optical techniques, 98-101 Wavelength, 3 intensity measurements, 98, Waves, acoustic, 2-7, 216 99 Lamb waves, 5, 6 interferometry, 100, 101 longitudinal wave, 3 schlieren visualization, 99, Love waves, 5 100 modes of , 5, radiation force 6,31-33 balance radiometer, 90, 91 periodic wave motion, 2, 3 float radiometer, 89, 90 Raleigh waves, 5 intensity techniques, 92, 93 standing waves, 6, 7 modulated system, 91, 92 surface waves, 5 portable instruments 92 transverse waves, 5 total power, 81-92 , 28-31 reci procity calibration, 101, 102 wave parameters, 4, 5 thermal methods, 93-98 Whole-body radiation, 120, 121