Ultrasound transceiver and control of a thermal damage process

Abstract

An ultrasonic transceiver apparatus for intracorporeal use, comprises an undamped ultrasonic transceiver for placing in a confined intracorporeal space, the transceiver vibrating at an instantaneous frequency and being excited to cause vibration at said instantaneous frequency to produce an ultrasonic ablation beam for ablating surrounding tissues and being further excited to cause vibration by primary echo signals returning from surrounding tissues—from separate excitations during quiet periods between the ablation—to monitor ablation progress. A signal processor isolates the primary echo signals from ringing, secondary echoes and extraneous noise also received from the transceiver and uses presence or absence of the characteristic frequency, or of a body characteristic frequency such as pulse or breathing, as an isolation criterion.

1 . An ultrasonic transceiver apparatus for intracorporeal use, the apparatus comprising:
 an undamped ultrasonic transceiver for placing in a confined intracorporeal space, the transceiver having an instantaneous excitation frequency and for receiving excitation at said excitation frequency to produce an ultrasonic ablation beam for ablating surrounding tissues and being further for receiving excitation by primary echo signals returning from surrounding tissues;   a signal processor connected to said transceiver configured to isolate said primary echo signals from ringing, secondary echoes and extraneous noise also received from said transceiver, said signal processor using presence or absence of said instantaneous excitation frequency as an isolation criterion.   
     
     
         2 . The ultrasonic transceiver apparatus of  claim 1 , wherein said signal processor is configured with an instantaneous frequency estimator to obtain an envelope of received signal minus excitation signal from said undamped ultrasonic transceiver and to use a global phase and local slopes thereof as an estimate of said instantaneous frequency, and further comprising an isolator unit for isolating signal segments whose instantaneous frequency approaches said characteristic frequency as segments containing primary echoes. 
     
     
         3 . The ultrasonic transceiver apparatus of  claim 2  further comprising a window unit for windowing said received signal using a windowing length chosen to provide windows with an expectation of a single primary echo. 
     
     
         4 . The ultrasonic receiving apparatus of  claim 3 , wherein said signal processor is further configured to find a point of appearance of a primary echo in a received signal by successively dividing said curve and fitting to a linear functions and calculating a point at which a corresponding error function is minimized. 
     
     
         5 . The ultrasonic receiving apparatus of  claim 4 , further configured with a location unit to determine a distance to a first feature wall from said point of appearance. 
     
     
         6 . The ultrasonic receiving apparatus of  claim 5 , wherein said location unit is configured to use a second point of appearance of a further primary echo to determine a distance to a second feature wall, the signal processor further comprising a monitoring unit for monitoring a distance between said first feature wall and said second feature wall as an indicator of ablation progress. 
     
     
         7 . The ultrasonic apparatus of  claim 1 , wherein said signal processor comprising a convolution unit for convolving an excitation signal with the received signal to carry out said isolation of the primary echo. 
     
     
         8 . The ultrasonic apparatus of  claim 1 , wherein said signal processor comprises a Fourier component analyzer for isolating segments having a principle Fourier component which corresponds to a body-characteristic frequency. 
     
     
         9 . The ultrasonic apparatus of  claim 1 , wherein said signal processor comprises a coherent summation unit for carrying out data summation such as to preserve amplitude and shift signals to a same phase. 
     
     
         10 . The ultrasonic apparatus of  claim 9 , wherein said coherent summation unit is configured to perform coherent summation, said coherent summation comprising building an auxiliary matrix of phase weights, making a Hilbert transform and multiplying to bring the entire signal to the same phase, therewith to create an in-phase sum. 
     
     
         11 . The ultrasonic apparatus of  claim 1 , further comprising a reference subtracting unit configured to subtract a reference from the transceiver signal by averaging several signal samples. 
     
     
         12 . An ultrasonic transceiver method for intracorporeal use, the method comprising:
 placing an undamped ultrasonic transceiver in a confined intracorporeal space, the transceiver having a characteristic frequency   
       exciting said transceiver at an instantaneous excitation frequency to produce an ultrasonic ablation beam for ablating surrounding tissues using ablation pulses;
 at intervals between said ablation pulses providing monitoring excitation to elicit primary echo signals returning from surrounding tissues; 
 isolating said primary echo signals from ringing, secondary echoes and extraneous noise also received from said transceiver using presence or absence of said instantaneous excitation frequency as an isolation criterion. 
 
     
     
         13 . The ultrasonic transceiver method of  claim 12 , wherein said isolation comprises:
 obtaining an envelope of received signal minus excitation signal from said undamped ultrasonic transceiver and using a global phase and local slopes as an estimate of said instantaneous frequency,   isolating those signal segments whose frequency approaches said instantaneous excitation frequency.   
     
     
         14 . The ultrasonic transceiver method of  claim 13  further comprising windowing said received signal using a windowing length chosen to provide windows with an expectation of a single primary echo. 
     
     
         15 . The ultrasonic receiving method of  claim 14 , further configured to find a point of appearance of a primary echo in a received signal by
 successively dividing said curve,   fitting to a linear functions and   calculating a point at which a corresponding error function is minimized.   
     
     
         16 . The ultrasonic receiving method of  claim 15 , comprising determining a distance to a first feature wall from said point of appearance. 
     
     
         17 . The ultrasonic method of  claim 16 , comprising using a second point of appearance of a further primary echo to determine a distance to a second feature wall, and monitoring a distance between said first feature wall and said second feature wall as an indicator of ablation progress. 
     
     
         18 . The ultrasonic method of  claim 12 , comprising convolving an excitation signal with the received signal to carry out said isolation of the primary echo. 
     
     
         19 . The ultrasonic method of  claim 12 , comprising isolating segments having a principle Fourier component which corresponds to a body characteristic frequency. 
     
     
         20 . The ultrasonic method of  claim 12 , comprising carrying out coherent data summation such as to preserve amplitude and shift signals to a single phase. 
     
     
         21 . The ultrasonic method of  claim 20 , wherein said coherent summation comprises:
 making an auxiliary weights matrix evaluation;   carrying out a Hilbert transformation;   multiplication to bring all signals to the same phase; and   performing an in-phase summation.   
     
     
         22 . An ultrasonic transceiver apparatus for intracorporeal use, the apparatus comprising:
 an undamped ultrasonic transceiver for placing in a confined intracorporeal space, the transceiver having a characteristic frequency and for receiving excitation at said characteristic frequency to produce an ultrasonic ablation beam for ablating surrounding tissues and being further for receiving excitation by primary echo signals returning from surrounding tissues;   a signal processor connected to said transceiver configured to isolate said primary echo signals from ringing, secondary echoes and extraneous noise also received from said transceiver, said signal processor using correlation with a body-characteristic frequency as an isolation criterion.   
     
     
         23 . The apparatus of  claim 22 , wherein said body characteristic frequency is one member of the group consisting of pulse and breathing rate. 
     
     
         24 . The apparatus of  claim 22 , wherein said signal processor is configured to obtain a power spectrum of a signal extracted from said transceiver and to identify said primary echoes from peaks in said power spectrum at said body-characteristic frequency. 
     
     
         25 . The apparatus of  claim 22 , further comprising a coherent summation unit. 
     
     
         26 . The apparatus of  claim 22 , further comprising a convolution unit. 
     
     
         27 . A method of providing controlled thermal damage to a tissue, comprising:
 identifying locations of boundary walls of said tissue;   applying energy to said tissue;   during said applying, monitoring changes in locations of said boundary walls as indicators of an effect of said applying said energy on said tissue; and   controlling said thermal energy according to said effect.   
     
     
         28 . The method of  claim 27 , wherein said monitoring and said applying are carried out from within a blood vessel. 
     
     
         29 . The method of  claim 27 , wherein said monitoring and said applying are carried out using ultrasonics. 
     
     
         30 . The method of  claim 27 , wherein said effect on said tissue is thermal shrinkage. 
     
     
         31 . The apparatus of  claim 29 , wherein said applying comprises applying a non-focused ultrasonic ablation beam. 
     
     
         32 . The apparatus of  claim 1 , wherein said ultrasonic ablation beam is not focused. 
     
     
         33 . The method of  claim 12 , wherein said ultrasonic ablation beam is not focused.