Steam pop detection

Abstract

Medical apparatus includes an elongate probe for insertion into a body of a patient. The probe includes an ablation element and an acoustic transducer disposed at a distal end of the probe. An array of acoustic sensors is placed over the body. While the distal end of the probe is positioned in a target location in the body, a control unit drives the acoustic transducer in a training phase to emit an acoustic signal, receives electrical signals from the acoustic sensors in response to the acoustical signal, and processes the electrical signals so as to derive a phase profile focused at the target location. In an operational phase, the control unit drives the ablation element to ablate tissue in the body at the target location, and receives and filters the electrical signals from the acoustic sensors using the phase profile so as to detect acoustical activity at the target location.

1 . A medical apparatus, comprising:
 an elongate probe configured for insertion into a body of a patient, the probe comprising an ablation element and an acoustic transducer disposed at a distal end of the probe;   an array of acoustic sensors configured to be placed over the body of the patient; and   a control unit, which is configured, while the distal end of the probe is positioned in a target location in the body, to drive the acoustic transducer in a training phase to emit an acoustic signal, to receive electrical signals from the acoustic sensors in response to the acoustical signal, and to process the electrical signals so as to derive a phase profile focused at the target location, and which is further configured, in an operational phase, to drive the ablation element to ablate tissue in the body at the target location, to receive and filter the electrical signals from the acoustic sensors using the phase profile to compute phase-adjusted signals, and to sum the phase-adjusted signals.   
     
     
         2 . The medical apparatus of  claim 1 , in which the acoustic sensors are mounted on a vest, which is configured to be placed over a thorax of the patient. 
     
     
         3 . The medical apparatus of  claim 1 , in which the acoustic sensors comprise microphones. 
     
     
         4 . The medical apparatus of  claim 1 , in which the acoustic transducer comprises a piezoelectric crystal, and in which the control unit is configured to drive the piezoelectric crystal with electrical pulses. 
     
     
         5 . The medical apparatus of  claim 1 , in which the ablation element comprises an electrode, and in which the control unit is configured to drive the electrode with radio frequency (RF) electrical energy. 
     
     
         6 . The medical apparatus of  claim 1 , in which the control unit is configured to process the filtered electrical signals so as to detect steam pops occurring at the target location. 
     
     
         7 . The medical apparatus of  claim 1 , in which the probe comprises a catheter, which is configured for insertion into a chamber of a heart of the patient, so as to ablate myocardial tissue at the target location. 
     
     
         8 . The medical apparatus of  claim 1 , in which the phase profile comprises a set of phase delays. 
     
     
         9 . The medical apparatus of  claim 8 , in which the set of phase delays comprises a respective phase delay for each respective acoustic sensor. 
     
     
         10 . The medical apparatus of  claim 1 , in which the phase profile comprises a spectral phase profile. 
     
     
         11 . A method for monitoring treatment, comprising:
 inserting an elongate probe into a body of a patient, the probe comprising an ablation element and an acoustic transducer disposed at a distal end of the probe;   placing an array of acoustic sensors over the body of the patient;   in a training phase, positioning the distal end of the probe at various target locations in the body, and while the probe is disposed at each of the various target locations:
 driving the acoustic transducer to emit an acoustic signal; 
 receiving electrical signals from the acoustic sensors in response to the acoustical signal; and 
 processing the electrical signals so as to derive a phase profile focused at each of the various target locations; and 
   in an operational phase, while the distal end of the probe is positioned at one of the various target locations:
 driving the ablation element to ablate tissue in the body at the one of the various target locations; and 
 receiving and filtering the electrical signals from the acoustic sensors using the phase profile to compute phase-adjusted signals, and to sum the phase-adjusted signals. 
   
     
     
         12 . The method of  claim 11 , in which the acoustic sensors are mounted on a vest. 
     
     
         13 . The method of  claim 12 , further comprising placing the vest over a thorax of the patient. 
     
     
         14 . The method of  claim 12 , in which the acoustic sensors comprise microphones. 
     
     
         15 . The method of  claim 11 , further comprising:
 processing the filtered electrical signals;   detecting steam pops occurring at the one of the various target locations; and   interrupting the step of driving the ablation element.   
     
     
         16 . The method of  claim 15 , in which the probe comprises a catheter, which is configured for insertion into a chamber of a heart of the patient, so as to ablate myocardial tissue.