GB2064117A - Ultrasonic inspection apparatus - Google Patents

Abstract

This invention relates to ultrasonic inspection apparatus, e.g. for detecting blood flow. An ultrasonic probe (10) is arranged to transmit (18) a signal at a characteristic radio frequency and to receive (19) reflected signals close to that frequency. The signal processing unit 11 converts the received signals into an audio frequency signal, e.g. representing the doppler shift. The signal processing unit 11 has a broad band input and therefore can process received signals having a wide range of characteristic frequencies. If it is desired to use the apparatus at a different frequency a different probe 10 is plugged into input 45 of unit 11, the different probe having the required characteristic frequency. <IMAGE>

Description

SPECIFICATION Ultrasonic inspection apparatus This invention relates to ultrasonic inspection apparatus and in particular, but not exclusively, to apparatus for detecting blood flow.

According to the present invention there is provided ultrasonic inspection apparatus comprising a circuit for converting a radio frequency signal to an audio signal, a set of interchangeable ultrasonic probes each having a characteristic frequency and including a head engageable on the surface of a workpiece and carrying an ultrasonic transmitter for transmitting signals into a part of the workpiece and an ultrasonic receiver for receiving signals reflected from the part of the workpiece, means for generating a radio frequency signal at the characteristic frequency of the probe, means for feeding the radio frequency signal to the transmitter, means for feeding the received signals to an output on the probe and means for connecting the output of one probe at a time to the converting circuit to produce audio frequency signals corresponding to the received signals.

The converting circuit may include a D.C. power source in which case the connecting means may connect the power source to the output of the probe to power at least one of the frequency generating means, feeding means, transmitter and receiver. In this latter case means are provided in the probe and the converting circuit for decoupling the received signals from their respective power supplies.

The characteristic frequency of each probe may lie in the range 1 MHz~1 5MHz.

The characteristic frequency of a given probe in the set of probes may be one of 2MHz, 4MHz, 8MHz and 10MHz.

The connecting means may comprise a single coaxial cable.

The audio frequency signals may represent the doppler shift of the received signals with respect to the transmitted frequency.

A specific embodiment of the invention will now be described with reference to the accompanying drawings in which: Figure 1 is a part sectional view of an ultrasonic inspection apparatus; Figure 2 is a diagrammatic circuit of the circuitry contained within the probe of the apparatus of Figure 1; and Figure 3 is a diagrammatic view of a circuit for converting the signals generated by the probe of the apparatus of Figure 1.

Ultrasonic inspection apparatus using a probe having a head for applying to a workpiece and then for transmitting signals into the workpiece and receiving reflected signals from the workpiece are well known. Such probes either carry all their circuitry in the body of the probe or all the circuitry other than the ultrasonic transmitter and receiver in an associated box, the probe and box being connected by a flexible cable. Each probe has a characteristic frequency. In many applications, particularly medical applications a user wishes to use different transmitted frequencies, depending on what part of the workpiece he wishes to study.

This is because the penetration of the signals depend on the transmitted frequency. Typically a doctor might wish to use probes having characteristic transmitted frequency of 2MHz, 4MHz, 8MHz and 10MHz. With existing apparatus he has to purchase a complete set of apparatus for each frequency he wants to use, because each apparatus has a single characteristic frequency of operation.

Figure 1 shows a probe 10 which is connected to a signal probe processing unit 11 by a coaxial cable 12. The signal processing unit 11 is in turn connected to a loud speaker 13, by a line 14.

The probe 10 comprises a cylindrical body 15 in one end of which is mounted a polystyrene head 16, which is transparent to ultrasound. The head 16 may be made of perspex, acrylic resin or other suitable material. The head 16 is of generally triangular cross section with its apex directed axially into body 1 5. The head is formed with an axially, inwardly facing diametric groove 17.

An ultrasonic transmitter 18 is mounted on the angled face of head 16 to one side of groove 17 and an ultrasonic receiver 19 is mounted on the angled face of head 1 6 on the other side of groove 17. The transmitter 18 and receiver 19 are connected, by respective leads 20, 21 to its circuit 22.

The circuit 22 is connected by coaxial cable 12 to signal processing unit 11.

Figure 2 shows circuit 22 diagrammatically together with its connections to transmitter 18.

receiver 19 and coaxial cable 12. Circuit 22 is essentially divided into two halves. The upper half generally indicated at 23 relates to generation and transmission of a signal, whilst lower half 24 relates to the receiving and feeding of the reflected signal.

The upper half 23 of circuit 22 comprises a radio frequency oscillator 25 set to generate a radio frequency signal at the predetermined characteristic frequency of the probe 10. This signal is fed into amplifier 26 by line 27. The amplified signal is then fed to tune circuit 28 via line 29 and from there to transmitter 18 by line 20. The tuned circuit 28 serves to match amplifier 26 with transmitter 18, which transmits the radio frequency signal.

As will be described below some of this signal is reflected and received by receiver 19. The receiver 19 feeds the received signal to tuned circuit 30 along line 21. The tuned circuit 30 feeds the received signals to amplifier 31 via line 32.

Tuned circuit 30 is tuned to the characteristic frequency of the probe and serves both to match the receiver 19 with amplifier 31 and to filter out extraneous signals. Amplifier 31 feeds the received signals to tuned circuit 33, via line 34 from whence they are fed to coaxial cable 12.

Figure 3 shows a part of the circuitry contained in signal processing unit 11 in diagrammatic form.

The circuit of Figure 3 is essentially designed to convert the radio frequency received signals into audio signals. The received signals are fed from probe output 35 along coaxial cable 12 to tuned circuit 36. The tuned circuit 36 feeds the signals to a detector 37, which converts the radio frequency signals to audio frequency signals in a known manner and the audio frequency signals are then fed to amplifier filter 38, which in turn feeds the audio signals to loud speaker 14 via line 13. It will be appreciated that the audio frequency signals represent the doppler shift of the received signals with respect to the transmitted frequency.

Signal processing unit 11 is provided with a D.C. power source (not shown) such as a battery, which feeds power lines 39 and 40 and as these lines are connected directly into coaxial cable 12 output 35 has a D.C. voltage drop across it. This voltage drop is applied to power lines 41 and 42 of circuit 22. The received signals are decoupled from power lines 41 and 42 by tuned circuit 33 and a capacitor 43 whilst power lines 39 and 40 are decoupled by tuned circuit 36 and capacitor 44. This system allows the power source for the probe circuitry to be placed in signal processing unit 11, without the need for more than a single cable connection between unit 11 and probe 10.

In use the head 16 is applied, for example, to a patient's arm over the vessels which are to be inspected. A gel or other coupling medium would be applied to the face of head 16 to ensure a good ultrasonic interface between the head and the body. The apparatus is then switched on and signals are transmitted by the transmitter 18 into the body. These signals are reflected by a part of the body and because of the angles at which the transmitter and receiver are set a portion of the reflected signals are reflected back into receiver 19. The signals are then processed as described above and appear as an audio output on line 14.

The signals can then be broadcasted through loud speaker 13 or they can be fed into an earphone arrangement (not shown). Alternatively they can be displayed, after further processing, on an oscilloscope or by a chart recorder.

The signals may represent blood flow, shown by the Doppler shift in the transmitted signal, or internal movement such as the movement of the mitral valve. The many uses of ultrasonic probes are well known and are not described here.

If the user then wants to inspect a part of the body at a different depth from the surface he can unplug the probe he has been using from input 45 of signal processing unit 11 and plug-in a probe with the desired characteristic frequency. It will thus be seen that the arrangement of the apparatus in which circuit 22 is placed in the body of the probe and in which the circuit shown in Figure 3 is placed in signal processing unit 11 allows a set of probes, covering a wide range of characteristic frequencies, to be used with a single processing unit. The cost of supplying a single processing unit with a set of probes is considerably less than having to supply a separate complete apparatus for each frequency.

Claims (7)

1. Ultrasonic inspection apparatus comprising a circuit for converting a radio frequency signal to an audio signal, a set of interchangeable ultrasonic probes each having a characteristic frequency and including a head engageable on the surface of a workpiece and carrying an ultrasonic transmitter for transmitting signals into a part of the workpiece and an ultrasonic receiver for receiving signals reflected from the part of the workpiece, means for generating a radio frequency signal at the characteristic frequency of the probe, means for feeding the radio frequency signal to the transmitter, means for feeding the received signals to an output on the probe and means for connecting the output of one probe at a time to the converting circuit to produce audio frequency signals corresponding to the received signals.

2. Apparatus as claimed in Claim 1 wherein the converting circuit includes a D.C. power source, wherein the connecting means connects the power source to the output of the probe to power at least one of the frequency generating means, feeding means, transmitter and receiver, and wherein means are provided in the probe and the converting circuit for decoupling the received signals from their respective power suppiies.

3. Apparatus as claimed in Claims 1 or 2 wherein the characteristic frequency of each probe lies in the range 1 MHz to 15MHz.

4. Apparatus as claimed in Claim 3 wherein the characteristic frequency of a given probe in the set of probes is one of 2MHz, 4MHz, 6MHz, 8MHz and 10MHz.

5. Apparatus as claimed in any one of the preceding claims wherein the means for connecting comprises a single coaxial cable.

6. Apparatus as claimed in any one of the preceding claims wherein the audio frequency signals represent the doppler shift of the received signals with respect to the transmitted frequency.

7. Ultrasonic inspection apparatus substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.