(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2007/0239019 A1
`(43) Pub. Date:
`Oct. 11, 2007
`Richard et al.
`
`US 2007023 90 l 9A1
`
`(54) PORTABLE ULTRASONIC IMAGING PROBE
`THAN CONNECTS DIRECTLY TO A HOST
`COMPUTER
`
`(76) Inventors: William D. Richard, BallWin, MO
`(US); Roman Solek, Pleasanton, CA
`(US); David M. Zar, Maryland
`Heights, MO (US)
`
`Correspondence Address:
`FLIESLER MEYER LLP
`650 CALIFORNIA STREET
`14TH FLOOR
`SAN FRANCISCO, CA 94108 (US)
`
`(21) App1.No.:
`
`11/353,185
`
`(22) Filed:
`
`Feb. 13, 2006
`
`Publication Classi?cation
`
`(51) Int. Cl.
`(2006.01)
`A61B 8/00
`(52) US. Cl. .......................................... .. 600/459; 600/443
`
`(57)
`
`ABSTRACT
`
`A portable ultrasonic imaging probe is adapted to connect to
`a host computer via a passive interface cable, e. g., a standard
`USB 2.0 peripheral interface cable or a standard IEEE 1394
`“FireWire” peripheral interface cable. In accordance With an
`embodiment, the portable ultrasound imaging probe
`includes a probe head, a logarithmic compressor, an enve
`lope detector, and analog-to-digital converter and interface
`circuitry, all of Which receive poWer from the host computer
`via the passive interface cable. To simplify the portable
`ultrasonic imaging probe, none of electronic beamforming,
`time gain compensation, gray-scale mapping and scan con
`version are performed Within the probe. This abstract is not
`intended to describe all of the various embodiments of the
`present invention, or to limit the scope of the invention.
`
`112
`
`/—
`
`HOST
`+ r122?
`
`COM.
`CHIPSET
`
`/—1o4
`[106 /
`1
`
`PROBE
`
`TARGET
`
`5108
`
`0 r124
`
`CPU
`
`MEMORY
`\-126
`DISPLAY
`\12a
`INPUT
`DEVICE
`\—13o
`
`LGE-1019 / Page 1 of 12
`LGE v. Fundamental
`
`

`

`Patent Application Publication Oct. 11, 2007 Sheet 1 0f 4
`
`US 2007/0239019 A1
`
`oowl\
`
`.5015.
`
`Nov
`\ 31
`
`mmOmE
`
`42. .9"
`
`we]
`WTNNI +
`
`$1 0
`3&0
`
`ow;
`
`3)
`
`o2)
`
`LGE-1019 / Page 2 of 12
`
`

`

`Patent Application Publication Oct. 11, 2007 Sheet 2 0f 4
`
`US 2007/0239019 Al
`
`CO
`C)
`‘
`
`112
`
`FIG. 1B
`
`102
`
`106
`
`104
`
`LGE-1019 / Page 3 of 12
`
`

`

`Or3dOud
`
`
`
`éOld
`
`obe
`
`AC’WLISId
`
`©3uYVANIT
`
`gez-/
`
`Patent Application Publication Oct. 11,2007 Sheet 3 of 4
`
`US 2007/0239019 Al
`
`802
`
`0ze
`
`Yasind
`
`Sf|SOVLIOAp97/eS2/0SZ—WaAqOONa|YOLOWS1EVINVA
`YAGOONSOLASGAHOLIMS
`AGSDOWNYGSHOLIMSHO.UMS/M
`
`
`
`
`
`
`
`
`Ove
`
`
`
`OlSOVAYALNI
`
`yOSSd00"d
`
`HUM
`
`YOLOANNOD
`
`LGE-1019 / Page 4 of 12
`
`LGE-1019 / Page 4 of 12
`
`

`

`Patent Application Publication Oct. 11,2007 Sheet 4 of 4
`
`US 2007/0239019 Al
`
`
`
`
`
`82SOVLIOAYOLOWATEVINVA
`
`Ore93yNONE
`
`1Add
`
`
`
`901A1EVDADVAYSLNIWOUSAS
`
`
`
`SEZTYNSISTONLNODWMd
`
`dWNd
`
`aTOYXLNOD
`
`MS
`
`dvO
`
`AOVLIOA
`
`Y3TENCG
`
`
`
`901JIGWDJOVAYMSLNIWOAS
`
`ADYVHD €‘Sid
`
`Pv-Sls
`
`0¢¢SdAH
`
`LGE-1019 / Page 5 of 12
`
`LGE-1019 / Page 5 of 12
`
`
`
`

`

`US 2007/0239019 A1
`
`Oct. 11, 2007
`
`PORTABLE ULTRASONIC IMAGING PROBE
`THAN CONNECTS DIRECTLY TO A HOST
`COMPUTER
`
`FIELD OF THE INVENTION
`[0001] The present invention relates to portable ultrasonic
`imaging probes, and more speci?cally, to such probes that
`can be directly connected to a host computer, such as an
`olf-the-shelf laptop computer, or the like.
`
`BACKGROUND
`[0002] Typically, ultrasound imaging systems include a
`hand-held probe that is connected by a cable to a relatively
`large and expensive piece of hardWare that is dedicated to
`performing ultrasound signal processing and displaying
`ultrasound images. Such systems, because of their high cost,
`are typically only available in hospitals or in the offices of
`specialists, such as radiologists.
`
`[0003] Recently, there has been an interest in developing
`more portable ultrasound imaging systems that can be used
`With personal computers. One such system, described in
`US. Pat. No. 6,440,071, includes an electronic apparatus
`that is connected betWeen a personal computer and an
`ultrasound probe. The electronic apparatus sends and
`receives signals to and from an ultrasound probe, performs
`ultrasound signal processing, and then sends ultrasound
`video to a personal computer that displays the ultrasound
`video. A disadvantage of the system of the ’071 patent is that
`there is a need for a custom electronic apparatus located
`betWeen the probe and the personal computer. A further
`disadvantage of the system of the ’071 patent is that analog
`signals travel a relatively long distance betWeen the probe
`and the electronic apparatus, Which Will result in a poor
`signal-to-noise ratio. Another disadvantage of the system of
`the ’071 patent is that the cable that carries analog signals
`betWeen the probe and the electronic apparatus is a custom
`cable.
`
`[0004] Another ultrasound imaging system that that can be
`used With personal computers is described in US. Pat. No.
`6,969,352. This system includes an integrated front end
`probe that interfaces With a host computer, such as a
`personal computer. The integrated front end probe performs
`electronic beamforming and other signal processing, such as
`time gain compensation (TGC), using hardWare that is
`dedicated to such ?nctions, and sends ultrasound video to
`the host computer that displays the ultrasound video. A
`disadvantage of the system of the ’352 patent is that the
`components necessary to perform electronic beamforming
`as Well as the components necessary to perform TGC Within
`the integrated front end probe are relatively expensive.
`Another disadvantage is of the system of the ’352 patent is
`that a custom cable, Which includes a DC-DC converter, is
`used to connect the probe to the host computer.
`
`[0005] Accordingly, there is still a need for an inexpensive
`portable ultrasound probe that can be used With an off-the
`shelf host computer, such as a personal computer. Prefer
`ably, such a portable ultrasound probe is inexpensive enough
`to provide ultrasound imaging capabilities to general prac
`titioners and health clinics having limited ?nancial
`resources.
`
`SUMMARY
`[0006] Embodiments of the present invention relate to a
`portable ultrasonic imaging probe that is adapted to connect
`
`to a host computer via a passive interface cable, such us, but
`not limited to, a standard USB 2.0 peripheral interface cable
`or a standard IEEE 1394 “FireWire” peripheral interface
`cable.
`
`[0007] In accordance With an embodiment, the portable
`ultrasound imaging probe includes a probe head, a logarith
`mic compressor, an envelope detector, and analog-to-digital
`converter and interface circuitry. The probe head includes a
`maneuverable single-element transducer to send ultrasonic
`pulses and detect ultrasonic echoes. The logarithmic com
`pressor performs logarithmical compression of analog echo
`signals representative of the detected ultrasonic echoes. The
`envelope detector performs envelope detection of the loga
`rithmically compressed analog echo signals. The analog-to
`digital converter converts the logarithmically compressed
`and envelope detected analog echo signals to digital signals
`representative of the logarithmically compressed and enve
`lope detected echo signals. The interface circuitry transfers
`the digital signals representative of the logarithmically com
`pressed and envelope detected echo signals across the pas
`sive interface cable to a host computer, so that the host
`computer can perform time gain compensation, gray-scale
`mapping and scan conversion of the data, and display
`ultrasound images on a display associated With the host
`computer.
`[0008] In accordance With an embodiment, the logarithmic
`compressor and the envelope detector are collectively
`embodied in a logarithmic ampli?er. In other Words, the
`logarithmic ampli?er receives the analog echo signals rep
`resentative of the detected ultrasonic echoes, performs both
`logarithmic compression and envelope detection of the
`analog echo signals, and outputs the logarithmically com
`pressed and envelope detected analog echo signals.
`[0009] In accordance With embodiments of the present
`invention, in order to provide for a relatively simple and
`inexpensive portable ultrasound imaging probe, the portable
`ultrasound imaging probe does not perform any of time gain
`compensation, gray-scale mapping and scan conversion.
`Rather, these functions are performed Within the host com
`puter that receives the digital data from the portable probe.
`Also, because the probe head includes a maneuverable
`single-element transducer, there is no need for the portable
`ultrasound imaging probe, or the host computer for that
`matter, to perform any electronic beamforming.
`
`[0010] In accordance With embodiments of the present
`invention, the probe head assembly, the logarithmic com
`pressor, the envelope detector, the analog-to-digital con
`verter and the interface circuitry all receive poWer from the
`host computer via the same passive interface cable across
`Which the probe transfers the digital signals to the host
`computer. This can be accomplished by including voltage
`regulator circuitry, Within the portable ultrasonic imaging
`probe, to receive a poWer signal from the host computer via
`the passive interface cable, and to produce voltages used to
`poWer the aforementioned components.
`[0011] Additionally, the probe head assembly includes a
`pulser to provides high voltage pulses to the transducer to
`cause the transducer to send ultrasonic pulses. In accordance
`With an embodiment of the present invention, poWer for the
`pulser is received from a high voltage poWer supply Within
`the portable ultrasonic imaging probe, Where the high volt
`age poWer supply steps-up a voltage of the poWer signal,
`
`LGE-1019 / Page 6 of 12
`
`

`

`US 2007/0239019 A1
`
`Oct. 11, 2007
`
`received from the host computer via the passive interface
`cable, to thereby produce the higher voltage that powers the
`pulser.
`[0012] The portable ultrasound imaging probe may also
`include a pre-ampli?er and a ?lter, Wherein the analog echo
`signals are preampli?ed and ?ltered by the pre-ampli?er and
`the ?lter before being provided to the logarithmic compres
`sor.
`
`[0013] This description is not intended to be a complete
`description of, or limit the scope of, the invention. Alterna
`tive and additional features, aspects, and objects of the
`invention can be obtained from a revieW of the speci?cation,
`the ?gures, and the claims.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`[0014] FIG. 1A is a high level diagram that is useful for
`describing embodiments of the present invention.
`
`[0015] FIG. 1B illustrates a speci?c implementation of the
`invention originally described With reference to FIG. 1A.
`
`[0016] FIG. 2 is a block diagram that shoWs additional
`details of an ultrasonic imaging probe according to an
`embodiment of the present invention.
`
`[0017] FIG. 3 illustrates additional details of the buck
`regulator (BUCK REG) shoWn in FIG. 2, according to a
`speci?c embodiment of the present invention.
`[0018] FIG. 4 illustrates additional details of the high
`voltage poWer supply (HVPS) shoWn in FIG. 2, according to
`a speci?c embodiment of the present invention.
`
`DETAILED DESCRIPTION
`
`[0019] FIG. 1A shoWs an ultrasonic imaging probe 102,
`according to an embodiment of the present invention, that is
`connected by a passive interface cable 106 to a host com
`puter 112. The host computer 112 can be a desktop personal
`computer (PC), a laptop PC, a pocket PC, a tablet PC, a cell
`phone capable or running softWare programs (e.g., a Palm
`TreoTM), a personal digital assistant (e. g., a Palm PilotTM), or
`the like. The passive interface cable 106, Which includes
`connectors and passive Wires, can be a Universal Serial Bus
`(USB) cable (e.g., a USB 2.0 cable), a FireWire (also knoWn
`as IEEE 1394) cable, or the like. Preferably the probe 102 is
`not connected to any other device or poWer supply. Thus, as
`Will be described beloW, in a preferred embodiment the
`probe 102 receives all its necessary poWer from the host
`computer 112 via the passive interface cable 106.
`
`[0020] As Will be described in more detail beloW, in
`accordance With embodiments of the present invention, the
`probe 102 enables the host computer 112, via softWare
`running on the host computer 112, to form real-time ultra
`sonic images of a target 100 (e.g., human tissue or other
`materials) Without the need for any additional internal or
`external electronics, poWer supply, or support devices. More
`speci?cally, the probe 102 produces raW digitiZed data that
`is logarithmically compressed, envelope detected ultrasound
`echo data from a single transducer in the probe 102, and
`transmits such raW data to the host computer 112. When the
`host computer 112 receives raW data via the passive inter
`face cable 106 from the probe 102, the host computer 112
`performs time gain compensation (TGC), gray-scale map
`ping, and scan conversion of the raW data using softWare that
`
`runs on the host computer 112, and displays the resultant
`video images. No electronic beamforming or other equiva
`lent image processing is implemented by the probe 102,
`thereby reducing the complexity and cost of the probe 102.
`Additionally, because a single maneuverable transducer is
`used to obtain the raW ultrasound data, there is no need for
`any electronic beamforming or other equivalent image pro
`cessing to be performed on the data once it is transferred to
`the host computer 112, thereby simplifying the softWare that
`the host computer 112 runs, and thus reducing the required
`processing capabilities of the host computer 112. The term
`“raW data”, as used herein, refers to ultrasound imaging data
`that has not yet been time gain compensated, gray-scale
`mapped and scan converted. As described beloW, such raW
`data is included in the digital signals that are transferred
`from the probe 102 to the host computer 112.
`
`[0021] As shoWn in FIG. 1A, the host computer 112 Will
`likely include a communications port 108, a communica
`tions chip-set 122, a central processing unit (CPU) 124,
`memory 126, a display 128, and an input device 130, such
`as a keyboard, mouse, touch screen, track ball, or the like.
`Additionally, the host computer 112 runs softWare that
`enables the host to control speci?c aspects of the probe 102.
`Such softWare also enables the host computer 112 to perform
`time gain compensation (also knoWn as time gain correc
`tion), gray-scale mapping, and scan conversion of the raW
`data received from the probe 112 over the passive interface
`cable 106. The host computer 112 can then display the
`resulting ultrasound video on the display 128, as Well as
`store such video in its memory 126, or another data storage
`device (not shoWn). The article “A NeW Time-Gain Correc
`tion Method for Standard B-Mode Ultrasound Imaging”, by
`William D. Richard, IEEE T ransaclions of Medical Imaging,
`Vol. 8, No. 3, pp. 283-285, September 1989, Which is
`incorporated herein by reference, describes an exemplary
`time gain correction technique that can be performed by the
`host computer 112. The article “Real-Time Ultrasonic Scan
`Conversation via Linear Interpolation of Oversampled Vec
`tors,”UlZras0nic Imaging, Vol. 16, pp. 109-123,April 1994,
`Which is incorporated herein by reference, describes an
`exemplary scan conversion technique that can be performed
`by the host computer 112.
`
`[0022] The passive interface cable 106 includes at least
`one data line over Which data is carried, and at least one
`poWer line to provide poWer to a peripheral device, Which in
`this case is the ultrasonic imaging probe 102. For example,
`Where the passive interface cable 106 is a USB 2.0 cable,
`one Wire of the cable provides about 5V at about 1/2 Amp. In
`alternative embodiments, the passive interface cable 106 is
`a FireWire cable, Which also includes a poWer Wire. Other
`types of passive interface cable can be used if desired.
`HoWever, as mentioned above, it is preferred that the passive
`interface cable 106 is a standard olf-the-shelf cable that can
`interface With an olf-the-shelf interface IC. The term passive
`as used herein refers to a cable that does not regenerate
`signals or process them in any Way.
`
`[0023] FIG. 1B illustrates an example Where the host
`computer 112 is a laptop. FIG. 1B also shoWs an exemplary
`ergonomic design of a housing 103 for the ultrasonic imag
`ing probe 102 of the present invention. Other ergonomic
`designs are of course possible, and Within the scope of the
`present invention. Also, as explained above, other types of
`host computer 112 can also be used.
`
`LGE-1019 / Page 7 of 12
`
`

`

`US 2007/0239019 A1
`
`Oct. 11, 2007
`
`[0024] Additional details of the ultrasonic imaging probe
`102, according to speci?c embodiments of the present
`invention, are shoWn in FIG. 2. As shoWn in FIG. 2, in
`accordance With an embodiment of the present invention,
`the probe 102 includes a peripheral connector 104 and an
`interface IC 204 that enables the probe 102 to interface With
`the host computer 112 via the interface cable 106. The
`connector 104 and the interface IC 204 are preferably
`olf-the-shelf devices, but can be custom devices. In one
`embodiment, the connector 104 is a FireWire connector, and
`the interface IC 204 is a FireWire interface IC. In another
`embodiment, the connector 104 is a Universal Serial Bus
`(USB) connector, and the interface IC 204 is a USB interface
`IC. An exemplary olf-the-shelf IC that can be used to
`implement a USB interface is the CY7C8014A EZ-USB
`FXZLPTM USB Microcontroller available from Cypress
`Semiconductor Corp. of San Jose, Calif., Which integrates a
`USB 2.0 interface, 4 KB of static random access memory
`(SRAM) for buffering high-speed USB data, and an 8051
`microprocessor With 16 KB of code/data SRAM all inte
`grated into a single chip. This chip can run embedded 8051
`code that is stored in a serial programmable read only
`memory (SPROM) 246 that is accessible via an internal bus
`244 (e.g., an Inter-Integrated Circuit (I2C) bus) or that has
`been doWnloaded from the host computer 112 via a process
`called ReNumeration, Which is discussed in Cypress Semi
`conductor Corporation’s “EZ-USB FXZLPTM USB Micro
`controller Datasheet,” Cypress Document Number 38-8032
`Rev I, Jun. 1, 2005, Which is incorporated herein by refer
`ence.
`
`[0025] In accordance With an embodiment of the present
`invention, the portable ultrasound imaging probe 102
`includes a single transducer 270 that is pivoted by a shaft
`254 that is connected to a motor 250. An encoder 252, Which
`can be mechanical, optical, or some other type, is used to
`provide feedback indicative of the position of the motor
`shaft 254 (and thus the position of the transducer 270) to the
`microcontroller of the interface IC 204 and to a program
`mable logic device or programmable gate array, Which in the
`embodiment shoWn is a complex programmable logic device
`(CPLD) 206. As shoWn in FIG. 2, the transducer 270, the
`motor 250, the encoder 252 and the shaft 254 are compo
`nents of the probe head assembly 280. In one embodiment,
`the position of the transducer is represented by an one byte
`of data, such that there can be 256 different positions of the
`transducer 270 (i.e., position 0 through position 255).
`
`[0026] The ultrasonic imaging probe 102 includes an
`ultrasonic pulser 208 that sends precisely timed drive pulses
`to the transducer 270, through the transmit/receive (T/R)
`sWitch 210, to initiate transmission of ultrasonic pulses. The
`pulser 208 is con?gured to provide pulses that are suf?cient
`to drive the transducer 210 to ultrasound oscillation. The
`host computer 112, through the passive interface cable 106,
`the interface IC 204 and the CPLD 206, can control the
`amplitude, frequency and duration of the pulses output by
`the pulser 208 via the pulse control line 207. The pulser 208
`is poWered by a high voltage poWer supply (HVPS) 220,
`Which generates the necessary high voltage potential
`required by the pulser 208 from a loWer voltage (e.g., 5V)
`received via the passive interface cable 106. Additional
`details of the HVPS 220, according to an embodiment of the
`present invention, are discussed beloW With reference to
`FIG. 4.
`
`[0027] The pulser 208 is preferably a bi-polar pulser that
`produces both positive and negative high voltage pulses that
`can be as large as +/—100V. In such an embodiment, the
`HVPS 220 provides up to +/—100V supply rails to the pulser
`208. A digital-to-analog converter (DAC) 228 that is con
`nected to the internal bus 244 is used to set the peak voltage
`produced by the HVPS 220. In a speci?c embodiment, the
`commands used to control the bus 228 are generated by the
`microprocessor (e.g., an 8051 microprocessor) of the inter
`face IC 204. An exemplary IC that can be used to implement
`the bus 228 is the AD5301 Buffered Voltage Output 8-Bit
`DAC available from Analog Devices of NorWood, Mass.
`Additional details of the HVPS 220, according to an
`embodiment of the present invention, are described beloW
`With reference to FIG. 4.
`
`[0028] The T/R sWitch 210 is used to connect the sWitch
`270 to either the pulser 208 or a pre-ampli?er 212. When a
`high voltage pulse is produced by the pulser 208, the T/R
`sWitch 210 automatically blocks the high voltage from
`damaging the pre-ampli?er 212 While delivering the pulse to
`the sWitch 270 via a pulse path 272, Which can be, e.g., a
`short 50 ohm coaxial line. When the pulser 208 is not
`producing a pulse, the T/R sWitch 210 automatically
`sWitches to disconnect the sWitch 270 from the pulser 208,
`and to connect the sWitch 270 (via the pulse path 272) to the
`pre-ampli?er 212.
`
`[0029] The transducer 270, e.g., a pieZoelectric element,
`transmits ultrasonic pulses into the target region being
`examined and receives re?ected ultrasonic pulses (i.e.,
`“echo pulses”) returning from the region. As described
`above, the T/R sWitch 220 enables the probe 102 to alternate
`betWeen transmitting and receiving. When transmitting, the
`transducer 270, is excited to high-frequency oscillation by
`the pulses emitted by the pulser 208, thereby generating
`ultrasound pulses that can be directed at a target region/
`object to be imaged. These ultrasound pulses (also referred
`to as ultrasonic pulses) produced by the sWitch 270 are
`echoed back toWards the sWitch 270 from some point Within
`the target region/object, e.g., at boundary layers betWeen
`tWo media With differing acoustic impedances. Then, When
`receiving, the “echo pulse” is received by the sWitch 270 and
`converted into a corresponding loW-level electrical input
`signal (i.e., the “echo signal”) that is provided to the
`pre-ampli?er 212 for enhancing the signal.
`
`[0030] The pre-ampli?ed echo signal output by the pre
`ampli?er 212 is provided to a ?lter, such as a loW pass ?lter
`(LPF) 214 or a bandpass ?lter, Which ?lters out the frequen
`cies that are not of interest. The pre-ampli?er 212, in
`accordance With an embodiment, is a very loW noise ampli
`?er that provides about 20 dB of gain. The LPF 214, in
`accordance With an embodiment, is a passive, four-pole,
`band limited loW pass ?lter.
`
`[0031] The ?ltered pre-ampli?ed echo signal output by the
`?lter 214, Which is a radio frequency (RF) signal, is provided
`to a logarithmic ampli?er 216. The logarithmic ampli?er
`216 performs log-compression and envelope detection of the
`?ltered pre-ampli?ed echo signal, thereby compressing the
`dynamic range of the echo signal. An exemplary ?nction of
`the logarithmic ampli?er 216 can be
`
`LGE-1019 / Page 8 of 12
`
`

`

`US 2007/0239019 A1
`
`Oct. 11, 2007
`
`Where VOUT is the voltage output by the logarithmic ampli
`?er 216, Vy is the slope voltage, VIN is the voltage input to
`the logarithmic ampli?er 216 (i.e., the output of the pre
`ampli?er 212) and VX is the intercept voltage. In accordance
`With an embodiment of the present invention, the logarith
`mic ampli?er 216 has about 100 dB of dynamic range. An
`exemplary logarithmic ampli?er 216 having such a dynamic
`range is the AD83 10 98 dB Logarithmic Ampli?er, available
`from Analog Devices of NorWood, Mass.
`[0032] By compressing the dynamic range using the loga
`rithmic ampli?er 216, it is unnecessary to perform time gain
`correction (TGC) inside the probe 102 of the present inven
`tion. Rather, as mentioned above, and discussed in more
`detail beloW, the host computer 112 uses softWare to perform
`TGC. Additionally, because the logarithmic ampli?er 216
`performs envelope detection, the need to digitiZe radio
`frequency (RF) data is eliminated. This approach to ultra
`sound imaging also eliminates the need for electronic beam
`forming, Which is required by an ultrasound imaging system
`that employs a transducer array.
`[0033] The output of the logarithmic ampli?er 216, Which
`is a log-compressed and envelope-detected echo signal, is
`provided to an analog-to-digital converter (A/D) 218. The
`A/ D 218 samples the log-compressed and envelope detected
`echo signal (e.g., at 30 or 48 MHZ), to thereby digitiZe the
`signal. The A/D 216 is preferably an 8-bit analog-to-digital
`converter, because the cost of such a device is relatively
`inexpensive as compared to analog-to-digital converters
`With higher resolution. An exemplary A/D 216 is the
`ADC08L060 8-bit analog-to-digital converter available
`from National Semiconductor Corp. of Santa Clara, Calif.
`Nevertheless, analog-to-digital converters With other reso
`lution are also Within the scope of the present invention.
`
`[0034] For ease of implementation, space savings and cost
`considerations, it is preferred that the logarithmic ampli?er
`216 performs both logarithmic compression and envelope
`detection. HoWever, in another embodiment of the present
`invention, a logarithmic compressor and an envelope detec
`tor, Which are separate components, can be used to perform
`these ?nctions.
`
`[0035] The interface IC 204 outputs a clock signal 205 that
`has a frequency (e.g., 30 or 48 MHZ) selected by the host
`computer 112 via softWare. The clock signal 205 is provided
`to the CPLD 206 and the A/D 218. Where the interface IC
`204 is a CY7C8014A EZ-USB FXZLPTM USB Microcon
`troller, the clock signal is produced at the IFCLK output pin
`of the interface IC 204.
`
`[0036] The interface IC 204 also outputs controls signals
`that are used to set the pulse frequency, doWn-sampling rate,
`and other parameters inside the CPLD 206. The CPLD 206
`uses the clock signal 205 (e.g., 30 or 48 MHZ) to produce the
`pulse control signals 207 that are provided to the pulser 208.
`The CPLD 206 implements the logic functions and counters
`that are used to provide outputs of the A/D 218 to the
`interface IC 204. The CPLD 206 also provides the pulse
`control signal 207 to the pulser 208. An exemplary IC that
`
`can be used to implement the CPLD 206 is the XCR3064XL
`CPLD available from Xilinx of San Jose, Calif. A Field
`Programmable Gate Array (FPGA) or custom IC can be used
`in place of the CPLD, if desired.
`
`[0037] As mentioned above, the pulser 208 is preferably a
`bi-polar pulser. The high and loW times of the bipolar pulses
`produced by the pulser 208 can be, e.g., 1, 2, 3, or 4 clock
`periods in length, resulting in single-cycle bipolar pulses
`that are 2, 4, 6, or 8 clock periods in total length. These pulse
`periods correspond to bipolar pulse “frequencies” of 15, 7.5,
`5.0, or 3.75 MHZ (When a 30 MHZ clock is used) or 24, 12,
`8.0, or 6.0 MHZ (When a 48 MHZ clock is used). While the
`above mentioned clock frequencies and pulse frequencies
`have been provided for example, other clock and pulse
`frequencies are also Within the scope of the present inven
`tion.
`
`[0038] In accordance With speci?c embodiments of the
`present invention, to support different imaging depths,
`doWn-sampling is done by the CPLD 206. For example,
`doWn-sampling by 1, 2, 3, and 4 can be supported for each
`sample rate, resulting in effective sample rates of 30, 15, 10,
`and 7.5 MHZ (When the 30 MHZ clock is used) and 48, 24,
`16, and 12 MHZ (When the 48 MHZ clock is used). After
`doWn-sampling, the CPLD 206 Writes the doWnsampled
`digitiZed data (e.g., 2048 bytes) into buffers inside the
`interface IC 204, or separate buffers (not shoWn). For
`512x512 pixel images, 2048 samples per return echo cor
`responds to a 4x over-sampling rate as described in the
`Richard et al. article entitled “Real-Time Ultrasonic Scan
`Conversion via Linear Interpolation of Oversampled Vec
`tors,”UlZras0und Imaging, Vol. 16, pp. 109-123, April 1994,
`Which is incorporated herein by reference. Assuming the
`speed of sound in tissue is 1540 m/s, then 2048 samples
`taken at 7.5 MHZ corresponds to a maximum imaging depth
`of 21 cm, While 2048 samples taken at 48 MHZ corresponds
`to a minimum imaging depth of 3.3 cm. While embodiments
`of the present invention are not limited to the use of only
`these eight sample frequencies, this approach simpli?es the
`implementation.
`
`[0039] In accordance With an embodiment, the encoder
`252 outputs an index signal 260 and a pulse signal 262.
`When imaging, a softWare routine running on the micropro
`cessor of the interface IC 204 (or a separate microprocessor
`Within the probe 102) implements a servo control loop by
`monitoring the index and pulse signals 260 and 262 from the
`encoder 252. The microprocessor of the interface IC 204
`generates a pulse Width modulated (PWM) control signal
`238 that is used to drive a buck regulator 240 to produce the
`correct motor voltage signal 264 for the rotational speed
`desired. For example, if the motor 250 is running too sloWly,
`the PWM signal 238 is used to increase the motor voltage
`produced by the buck regulator 240, and, conversely, if the
`motor 250 is running too fast, the PWM signal 238 is used
`to decrease the motor voltage. The softWare routine running
`on the microprocessor of the interface IC 204 can also
`determine the position of the sWitch 270 from such infor
`mation.
`
`[0040] In accordance With an embodiment, the index sig
`nal 260 produced by the encoder 252 is asserted once per
`rotation of the motor 250, and the pulse signal 262 is
`asserted multiple times per rotation (e.g., 512 times per
`rotation, or 256 times per left/right or right/left transducer
`
`LGE-1019 / Page 9 of 12
`
`

`

`US 2007/0239019 A1
`
`Oct. 11, 2007
`
`sweep). The CPLD 206 monitors the pulse signal 262 and
`performs a data acquisition cycle each time a neW position
`(i.e., angle) of the sWitch 270 is detected. For each pulse
`signal 262, the CPLD 206 signals the pulser 206 to produce
`a pulse at one of several different available pulse frequencies
`and then transfers data (e.g., 2048 bytes of data) from the
`A/D 218 to the high-speed data transfer buffers inside (or
`outside) the interface IC 204. This data acquisition process
`happens Without intervention from the microprocessor of the
`interface IC 204 or the host 212. Once in the buffers, the data
`samples can be read over the passive interface cable 106 by
`the host computer 112. As mentioned above, in one embodi
`ment, the sWitch 270 can have 256 different positions (i.e.,
`angles), Which can be represented by a single byte. Of
`course, more positions can be represented if more than 8 bits
`are used to represent the position. When the interface IC 204
`sends the logarithmically compressed and envelope detected
`digital data to the host computer 112, such position data is
`sent thereWith. Collectively, the logarithmically compressed
`and envelope detected digital data and the position data can
`be referred to as vector data, because the data includes both
`magnitude data and direction data.
`
`[0041] In accordance With a preferred embodiment, the
`poWer for the motor 250 and all of the circuitry inside the
`probe 102 is received from the host computer 112 through
`the passive interface cable 106. For example, Where the
`passive interface cable 106 is a USB 2.0 compliant cable, a
`peripheral device connected to the cable 106 is alloWed to
`draW 1/2 Amp at a nominal 5V. Versions of this invention
`have been used to image at 10 frames/ second (5 revolutions
`per second on the motor 250) that draW as little as 1A Amp
`from a standard USB interface cable, Which is equivalent to
`1.25 W.
`
`[0042] In accordance With an embodiment, a linear regu
`lator IC 230 With integrated poWer sWitches and loW qui
`escent current requirements designed for USB applications
`is used to produce a 3.3V digital supply 232, a 3.3V analog
`voltage supply 234, as Well as a sWitched 5V supply 236 to
`sWitch the poWer to the encoder 256 on and off. The 3.3V
`digital supply 232 poWers the interface IC 204, the CPLD
`206, the SPROM 246, and the bus 228. The 3.3V analog
`supply poWers the preamp 212, the logarithmic ampli?er
`214, and the A/D 218. In a suspend mode (e.g., a USB
`suspend mode), a “shut doWn” sign