title: Controllable pulse parameter transcranial magnetic stimulator with enhanced circuit topology and pulse shaping.
abstract: OBJECTIVE
  This work aims at flexible and practical pulse parameter control in transcranial magnetic stimulation (TMS), which is currently very limited in commercial devices.
  
  
  METHODS
  We present a third generation controllable pulse parameter device (cTMS3) that uses a novel circuit topology with two energy-storage capacitors. It incorporates several implementation and functionality advantages over conventional TMS devices and other devices with advanced pulse shape control. cTMS3 generates lower internal voltage differences and is implemented with transistors with a lower voltage rating than prior cTMS devices.
  
  
  RESULTS
  cTMS3 provides more flexible pulse shaping since the circuit topology allows four coil-voltage levels during a pulse, including approximately zero voltage. The near-zero coil voltage enables snubbing of the ringing at the end of the pulse without the need for a separate active snubber circuit. cTMS3 can generate powerful rapid pulse sequences (< 10 ms inter pulse interval) by increasing the width of each subsequent pulse and utilizing the large capacitor energy storage, allowing the implementation of paradigms such as paired-pulse and quadripulse TMS with a single pulse generation circuit. cTMS3 can also generate theta (50 Hz) burst stimulation with predominantly unidirectional electric field pulses. The cTMS3 device functionality and output strength are illustrated with electrical output measurements as well as a study of the effect of pulse width and polarity on the active motor threshold in ten healthy volunteers.
  
  
  CONCLUSIONS
  The cTMS3 features could extend the utility of TMS as a research, diagnostic, and therapeutic tool.
authors.affiliation: Department of Psychiatry and Behavioral Sciences, Duke University, Durham, NC, USA. Department of Biomedical Engineering, Duke University, Durham, NC, USA. Department of Electrical and Computer Engineering, Duke University, Durham, NC, USA.
authors.forename: Angel V
authors.initials: AV
authors.lastname: Peterchev
authors.forename: Kevin
authors.initials: K
authors.lastname: DʼOstilio
authors.forename: John C
authors.initials: JC
authors.lastname: Rothwell
authors.forename: David L
authors.initials: DL
authors.lastname: Murphy
mesh_terms: D000328:Adult; D004867:Equipment Design; D019544:Equipment Failure Analysis; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D012815:Signal Processing, Computer-Assisted / Q000295:instrumentation*; D013813:Therapy, Computer-Assisted / Q000295:instrumentation*; D050781:Transcranial Magnetic Stimulation / Q000295:instrumentation*