WO2019160406A1

WO2019160406A1 - Data collection system suitable for imaging of a distant object

Info

Publication number: WO2019160406A1
Application number: PCT/NL2019/050078
Authority: WO
Inventors: Douwe Manuel VAN WILLIGEN; Michiel Antonius Petrus Pertijs
Original assignee: Technische Universiteit Delft
Priority date: 2018-02-13
Filing date: 2019-02-07
Publication date: 2019-08-22
Also published as: NL2020426B1

Abstract

Data collection system, in particular suitable for imaging of a distant object (2), comprising a transmission line (7) with a proximal end (8) and a distal end (9), wherein at the distal end (9) at least one transducer (10) is provided for transmitting an excitation signal and receiving a response signal, and amplifier means (12) to amplify the response signal and to provide the amplified response signal at the distal end (9) to the transmission line (7), and wherein at the proximal end (8) of the transmission line (7) a data processor (13) is provided for processing the amplified response signal received at the proximal end (8) of the transmission line (7), and wherein at the proximal end (8) of the transmission line (7) a power supply (14) is provided and a power source (15) for a transducer excitation signal, wherein the transmission line (7) is embodied as a single two-wire line equipped to transmit both power from the power supply (14) and the transducer excitation signal from the proximal end (8) to the distal end (9), wherein multiple transducers (10) are provided at the distal end (9), and the proximal end (8) is provided with an addressing organ (17) for providing configuration data on the transmission line (7) to sequentially address and select one of the multiple transducers (10) to transmit the excitation signal and receive the response signal, and wherein the data processor (13) is equipped to process and derive information from the collection of response signals received back from the transducers (10).

Description

DATA COLLECTION SYSTEM SUITABLE FOR IMAGING OF A DISTANT OBJECT

The invention relates to a data collection system, in particular suitable for imaging of a distant object, compris ing a transmission line with a proximal end and a distal end, wherein at the distal end at least one transducer is provided for transmitting an excitation signal and receiving a response signal, and amplifier means to amplify the response signal and to provide the amplified response signal at the distal end to the transmission line, and wherein at the proximal end of the transmission line a data processor is provided for processing the amplified response signal received at the proximal end of the transmission line, and wherein at the proximal end of the transmission line a power supply is provided and a power source for a transducer excitation signal, wherein the trans mission line is embodied as a single two-wire line equipped to transmit both power from the power supply and the transducer excitation signal from the proximal end to the distal end.

Such a data collection system is known from WO00/61008, which discloses an ultrasound catheter wherein a rotatable transducer couples to the input of a preamplifier. Protection circuits at the input and output of the preamplifi er protect the preamplifier from the transducer excitation signal. The preamplifier couples to the distal end of a trans mission line. In an alternate embodiment, at least one switch responds to the presence of the transducer excitation signal by coupling the transducer excitation signal to the rotatable transducer and protecting the preamplifier from the transducer excitation signal. The said at least one switch responds to the absence of the transducer excitation signal by coupling a received signal produced by the rotatable transducer to the input of the preamplifier. The said at least one switch fur ther responds to the absence of the transducer excitation sig nal by coupling the output of the preamplifier to the distal end of the transmission line.

WO00/61008 uses a single line to transfer power for the amplifier at the distal end and the transducer excitation signal for the single transducer at the distal end, however this system is unsuited for high-quality 3D-real time imaging with the least possible amount of motion artefacts which would require an array of transducers at the distal end, and multi ple lines that would be required for sending signals to and receiving signals from the respective transducers.

The article "A Front-End ASIC with High-Voltage

Transmit Switching and Receive Digitization for Forward- Looking Intravascular Ultrasound"· by Mingliang Tan, Chao Chen, Zhao Chen, Jovana Janjic, Verya Daeichin, Zu-yao Chang, Emile Nootinout, Gijs van Soest, Martin D. Verweij, Nico de Jong, and Michiel A. P. Pertijs; presented at the Custom Integrated Cir cuits Conference CICC 2017: Austin, TX, USA -

ISBN 97 S-1--5090- 5131 - 5 / 17 / $31 , 00@2017 IEEE presents a front-end ASIC (: Application Specific IC) for forward-looking intravas- cular ultrasound (IVUS) imaging. The ASIC is intended to be mounted at the tip of a catheter and can interface a total of 80 piezo-electric transducer elements with an imaging systems using only 4 cables. It is capable of switching high-voltage transmit pulses to 16 transmit elements, and capturing the re- suiting echo signals using 64 multiplexed receive elements.

The ASIC digitizes the received signals locally.

W02004/021044 discloses a data collection system ac cording to the preamble of claim 1, wherein accordingly multi ple transducers are provided at the distal end, and wherein the proximal end is provided with an addressing organ for providing configuration data on the transmission line to se quentially address and select the transducers at the distal end to transmit the excitation signal and receive the response signal, and wherein the data processor at the proximal end is equipped to process and derive information from the collection of response signals received back from the transducers.

It is an object of the invention to provide that only a single cable can be used in the data collection system and that this data collection system enables high quality real time imaging substantially free of motion artefacts, wherein the data collection system has improved versatility and flexi bility .

The data collection system of the invention has the features of one or more of the appended claims. In a first aspect of the invention the data collec tion system is embodied with the feature that the addressing organ is equipped to send address-data over the t ansmission line for addressing each and every transducer separately in an arbitrary sequence. This makes possible that the sequence of scanning of an object with the data collection system of the invention can be selected to best suit the situation at hand.

Suitably the addressing organ addresses each and eve ry transducer separately by sending configuration data embod ied as a string of address bits tailored to the transducer to be selected.

In an embodiment of the invention four different sig nals are transmitted over the single transmission line, to note the power for the amplifier at the distal end, the con figuration data, the excitation signal for the transducers and the response signals received back from the transducers. Ac cordingly only a single transmission line can be used, which has the tremendous advantage that the data collection system is capable for use in very narrow areas which do not leave much room for multiple transmission lines. This particularly but not exclusively applies in medical applications such as intravascular monitoring.

In a beneficial application of the invention the data processor is equipped to construe an image from the collection of response signals received back from the transducers.

In a preferred embodiment the addressing organ is ar ranged to superimpose the configuration data on the signal from the power supply travelling on the transmission line from the proximal end to the distal end.

Suitably the distal end is provided with a demodula tor for retrieving the configuration data received at the dis tal end of the transmission line and to select the transducer to transmit the excitation signal to, and to select the trans ducer from which to receive back the response signal.

It is preferable that at the distal end protection circuitry is provided to secure the amplifier means against damage due to the transducer excitation signal.

Desirably further in the system of the invention the protection circuitry comprises switches with a transmit mode and a receive mode, wherein the switches when in the transmit mode enable the transducer excitation signal to reach the transducers and block the transducer excitation signal from reaching the amplifier means, and that the switches when in the receive mode enable the response signals from the trans ducers to reach the amplifier means. It is however also possi ble that the protection circuitry is embodied with a diode- bridge circuit .

It is further beneficial that the protection circuit ry at the distal end comprises a voltage limiter to protect the amplifier means. The voltage limiter provides further pro tection against high voltages from the excitation signal that drives the transducers, and which might without such protec tion circuitry damage the amplifier means.

To assist the switches in assuming a proper switching mode it is desirable that the protection circuitry at the dis tal end comprises a voltage level detector to establish wheth er the transmission line transmits a transducer excitation signal .

Suitably the voltage level detector drives the switches to transmit mode when it detects a voltage on the transmission line above a predetermined threshold value. Fur ther it is desirable that the voltage level detector drives the switches to receive mode when it detects a voltage on the transmission line being below a predetermined threshold value for a predetermined time.

In a further preferred embodiment the amplifier means at the distal end is a current amplifier, wherein at the prox imal end a current sensor is provided that drives the data processor for processing the amplified response signal re ceived at the proximal end of the transmission line. The ap plication of a current amplifier has the notable advantage that the system is less sensitive for the capacitive load that the transmission line provides. Accordingly the performance in providing high quality real time imaging is improved in com parison with the alternative of voltage amplification. Instead of using a current amplifier it is also possible to apply fre quency division multiplexing or to apply an analog-digital converter following the current amplifier. Although the invention is not restricted thereto, the data collection system of the invention is particularly suited for intravascular imaging, wherein the transducers are

equipped to send to and receive ultrasound from an intravascu lar object to be imaged.

The invention will hereinafter be further elucidated with reference to the drawing of an exemplary embodiment of a data collection system for imaging according to the invention that is not limiting as to the appended claims.

In the drawing:

-figure 1 shows a schematic drawing of part of a data collection system of the invention when embodied as an intra vascular ultrasound imaging system;

-figure 2 shows a further schematic drawing of sig nals transmitted over a transmission line of the data collec tion system of the invention;

-figure 3 shows a schematic diagram of building blocks forming part of the data collection system of the in vention;

-figure 4 shows a more detailed circuit diagram rep resenting the circuitry at a distal end of the transmission line; and

-figure 5 shows a more detailed circuit diagram rep resenting the circuitry at a proximal end of the transmission line .

Whenever in the figures the same reference numerals are applied, these numerals refer to the same parts.

Turning first to figure 1 a blood vessel 1 is shown which suffers from stenosis 2 which is to be detected with the data processing system of the invention. For this purpose the data processing system is embodied as an intravascular ultra sound imaging system, only distant parts of which are shown in figure 1 as a catheter 3 with its corresponding guide wire 4, and at the distal end of the catheter 3 some electronics 5 for sending and receiving ultrasound signals with an array of transducers 6. Normally the transducers are piezo-electric transducers, but this is not essential.

The electronics 5 are placed at the distal end of the catheter 3 and within the catheter a transmission line 7 is present to facilitate communication between a proximal end 8 of the data collection system, and the distal end 9 of the da ta collection system as together depicted in figure 3, with a transmission line 7 connecting both ends 8, 9.

Figure 3 shows for clarity a single transducer 10 at the distal end 8, although the shaded lines 11 represent that according to the invention multiple transducers are provided at the distal end 9. Each of the transducers 10 is provided for transmitting an excitation signal towards an object of in terest such as the stenosis 2 in figure 1, and receiving back a response signal which is monitored by the transducers 10. According to the invention the respective transducers 10 are activated sequentially one at a time to send excitation sig nals and receive back response signals. Further there are (usually singular) amplifier means 12 to amplify the response signals from the transducers 10. The amplifier means 12 pro vide the amplified response signals at the distal end to pass over the transmission line 7 back to the proximal end 8 of the data collection system.

At the proximal end 8 of the transmission line 7 a data processor 13 is provided for processing the amplified re sponse signal that is received back at the proximal end 8 of the transmission line 7. The data processor 13 is equipped to construe an image from the collection of response signals re ceived back from the multitude of transducers 10 at the distal end 9.

The respective signals that are required to communi cate back and forth and to operate and control the electronics on the distal end 9 of the system of the invention all pass over the single transmission line 7. In connection therewith figure 3 shows that at the proximal end 8 of the transmission line 7 a power supply 14 is provided as well as a power source 15 for a transducer excitation signal Vtx that is required for feeding the transducers 10. The proximal end 8 is further pro vided with an addressing organ 17 for providing configuration data to pass over the transmission line 7 and that is used to sequentially address and select one of the multiple transduc ers 10 at a time to transmit the excitation signal Vtx and to receive back the response signal from the selected transducer 10. Since the excitation signal Vtx is a relatively high volt age signal of approximately 30 V, at the distal end 9 protec tion circuitry 16 is provided to secure the amplifier means 12 against damage which might otherwise be caused by the high voltage transducer excitation signal Vtx.

Figure 3 further depicts that the addressing organ 17 is arranged to superimpose the configuration data on the sig nal from the power supply 14 so as to jointly travel on the transmission line 7 from the proximal end 8 to the distal end 9. This joint signal is depicted in figure 2 as Vcable, being in this example a DC voltage power supply signal of 3 V on which the signal which is indicated (configuration) data is superimposed .

At the distal end 9 a demodulator 18 is provided for retrieving the (configuration) data received at the distal end 9 of the transmission line 7, which data is used to select the transducer 10 from the multitude of transducers which is to transmit the excitation signal and from which to receive the response signal back from.

According to another aspect protection circuitry 16 is applied in the data collection system of the invention that comprises switches with a transmit mode TX and a receive mode RX. The switches 16 are provided both at the proximal end 8 and at the distal end 9, and when in the transmit mode TX the switches 16 enable the transducer excitation signal Vtx to reach the transducers 10 and block the transducer excitation signal Vtx from reaching the amplifier means 12. In the re ceive mode RX the switches 16 enable the response signals from the transducers 10 to reach the amplifier means 12. Likewise the switches 16 also protect a sensor 21 which is provided at the proximal end 8 and that drives the data processor 13 for processing the amplified response signal received back at the proximal end 8 via the transmission line 7, and which signal originates from the amplifier 12. In this connection it is re marked that the amplifier 12 at the distal end 9 is preferably a current amplifier and that the sensor 19 is preferably a current sensor.

Figure 3 further shows that the protection circuitry at the distal end 9 also preferably comprises a voltage limit- er 19 to protect the amplifier means 12 against the high volt age transducer excitation signal Vtx.

It shows further in figure 3 that the protection cir cuitry at the distal end 9 comprises a voltage level detector 20 to establish whether the transmission line 7 transmits a high voltage transducer excitation signal Vtx. If that happens - which is shown in figure 2 as the peak voltage at the

"transmit" instance - the voltage level detector 20 drives the switches 16 to transmit mode TX, that is when it detects a voltage on the transmission line 7 above a predetermined threshold value. On the other hand the voltage level detector 20 drives the switches 16 to receive mode RX when it detects that the voltage on the transmission line 7 is below a prede termined threshold value for a predetermined time. In that case the amplifier 12 is enabled to amplify the signal current requirements of the transducers 10 as symbolized in figure 2 with Icable and to transmit this amplified current back over the transmission line 7 to the proximal end 8. The current sensor 19 at the proximal end 8 receives these signals and supplies it to the processor 13 which processes the sequential signals from the multiple transducers 10 at the distal end 9 into a real-time complete image of the object of interest 2 (figure 1 ) .

In figure 4 and figure 5 respectively exemplary em bodiments are shown of the electrical circuitry that can be used at the distal end 9 of the data collection system of the invention, as well as the electrical circuitry that can be used at the proximal end 8 of the data collection system of the invention.

Fig. 4 shows a block diagram of the circuitry at the distal end 9. Programmable switches Stx and Srx allow each el ement to be connected to the cable for TX, or to a low noise amplifier LNA for receiving mode RX. During receiving mode RX, a DC voltage of 3V on the cable powers the electronics at the distal end 9. To configure the switches, pulse-width modulated (PWM) data (500mVpp) is superimposed on the power supply. This is recovered by AC coupling, amplifying and thresholding, and then used to program a configuration shift register. A low- dropout regulator (LDO) prevents the modulated supply from af- fecting the operation of the associated logic. After configu ration, a high-voltage transmission mode TX signal with a max imum peak amplitude of 30V can be supplied to the cable, which will drive the elements selected for transmission mode TX to generate an acoustic pulse. This arrangement allows the pulse waveform to be defined on the system side. Transistors Ml and M3 clamp the high-voltage transmission mode TX signal to pro tect the low-voltage circuitry. A bias circuit (not shown) generates bias currents and Vclamp, which is stored on a ca pacitor during transmission mode TX, when a stable supply voltage is absent.

When the level detector senses that Vcable is below 6V for more than 200ns, the electronics at the distal end 9 switches back to the receiving mode RX by turning off the transmission mode TX switches and enabling the low noise am plifier LNA . The acoustic echoes received by the PZT-element which is selected for receiving mode RX creates a small signal current that is amplified by the low noise amplifier LNA and returned to the proximal end 8 of the system by superimposing it on the supply current. The supply current is a constant offset, because the logic is quiet in this period, and can therefore easily be filtered out on the proximal system side. Compared to the alternative conventional solution of driving the cable with a signal voltage, which requires that the elec tronics at the distal end 9 drive the cable capacitance, this current mode signalling is more power efficient.

Fig. 5 shows a simplified diagram of the circuitry used on the proximal end 8 of the system to drive, configure and read out the electronics at the distal end 9 of the sys tem. During receiving mode RX, a trans-impedance amplifier is used to supply the electronics at the distal end 9 with a fixed supply voltage (Vsup) while converting the amplified signal current to a voltage VRX with a trans-impedance gain set by resistor R1. Resistor R2 is used to match the cable im pedance, while capacitor C5 rejects the DC component associat ed with the supply current of the distal end 9 of the system. To configure the electronics at the distal end 9 of the sys tem, PWM-encoded data Vdata is added to Vsup, causing the vir tual ground of the shown operational amplifier to follow this signal, thus transmitting it over the coaxial cable to the distal end 9 of the system. During transmission mode TX, the high-voltage signal VTX generated by the system is AC-coupled to the cable.

Although the invention has been discussed in the foregoing with reference to an exemplary embodiment of the ap paratus of the invention, the invention is not restricted to this particular embodiment which can be varied in many ways without departing from the invention. The discussed exemplary embodiment shall therefore not be used to construe the append ed claims strictly in accordance therewith. On the contrary the embodiment is merely intended to explain the wording of the appended claims without intent to limit the claims to this exemplary embodiment. The scope of protection of the invention shall therefore be construed in accordance with the appended claims only, wherein a possible ambiguity in the wording of the claims shall be resolved using this exemplary embodiment.

Claims

1. Data collection system, in particular suitable for imaging of a distant object (2), comprising a transmission line (7) with a proximal end (8) and a distal end (9), wherein at the distal end (9) at least one transducer (10) is provided for transmitting an excitation signal and receiving a response signal, and amplifier means (12) to amplify the response sig nal and to provide the amplified response signal at the distal end (9) to the transmission line (7), and wherein at the prox imal end (8) of the transmission line (7) a data processor (13) is provided for processing the amplified response signal received at the proximal end (8) of the transmission line (7), and wherein at the proximal end (8) of the transmission line (7) a power supply (14) is provided and a power source (15) for a transducer excitation signal, wherein the transmission line (7) is embodied as a single two-wire line equipped to transmit both power from the power supply (14) and the trans ducer excitation signal from the proximal end (8) to the dis tal end (9), wherein multiple transducers (10) are provided at the distal end (9), and the proximal end (8) is provided with an addressing organ (17) for providing configuration data on the transmission line (7) to address and select the transduc ers (10) to transmit the excitation signal and receive the re sponse signal, and wherein the data processor (13) is equipped to process and derive information from the collection of re sponse signals received back from the transducers (10), characterized in that the addressing organ (17) is equipped to send address-data over the transmission-line for addressing each and every transducer (10) separately in an arbitrary se quence .

2. Data collection system according to claim 1, characterized in that the addressing organ (17) addresses each and every transducer (10) separately by sending configuration data embodied as a string of address bits tailored to the transduc er (10) to be selected.

3. Data collection system according to claim 1 or 2, characterized in that the data processor (13) is equipped to construe an image from the collection of response signals re ceived back from the transducers (10) .

4. Data collection system according to any one of claims 1 - 3, characterized in that the addressing organ (17) is arranged to superimpose the configuration data on the sig nal from the power supply (14) travelling on the transmission line (7) from the proximal end (8) to the distal end (9) .

5. Data collection system according to any one of claims 1 - 4, characterized in that the distal end (9) is pro vided with a demodulator (18) for retrieving the configuration data received at the distal end (9) of the transmission line (7) and to select the transducer (10) to transmit the excita tion signal and from which to receive the response signal.

6. Data collection system according to any one of claims 1 - 5, characterized in that at the distal end (9) pro tection circuitry (16, 19, 20) is provided to secure the am plifier means (12) against damage due to the transducer exci tation signal.

7. Data collection system according to claim 6, characterized in that the protection circuitry (16, 19, 20) com prises switches (16) with a transmit mode and a receive mode, wherein the switches (16) when in the transmit mode enable the transducer excitation signal to reach the transducers (10) and block the transducer excitation signal from reaching the am plifier means (12), and in the receive mode to enable the re sponse signals from the transducers (10) to reach the amplifi er means ( 12 ) .

8. Data collection system according to claim 6 or 7, characterized in that the protection circuitry (16, 19, 20) at the distal end (9) comprises a voltage limiter (19) to protect the amplifier means (12) .

9. Data collection system according to any one of claims 6 - 8, characterized in that the protection circuitry (16, 19, 20) at the distal end (9) comprises a voltage level detector (20) to establish whether the transmission line (7) transmits a transducer excitation signal.

10. Data collection system according to claim 9, characterized in that the voltage level detector (20) drives switches (16) forming part of the protection circuitry (16, 19, 20) to transmit mode when it detects a voltage on the transmission line (7) above a predetermined threshold value.

11. Data collection system according to claim 9 or 10, characterized in that the voltage level detector (20) drives switches (16) forming part of the protection circuitry (16, 19, 20) to receive mode when it detects a voltage on the transmission line (7) is below a predetermined threshold value for a predetermined time.

12. Data collection system according to any one of claims 1 - 11, characterized in that the amplifier means (12) at the distal end (9) is a current amplifier and at the proxi mal end (8) a current sensor (19) is provided that drives the data processor (13) for processing the amplified response sig nal received at the proximal end (8) of the transmission line (7).

13. Data collection system according to any one of claims 1 - 12, characterized in that the system is an ultra sonic imaging system, particularly suited for intravascular imaging, wherein the transducers (10) are equipped to send and receive ultrasound.