title: Transtemporal ultrasound application potentially elevates brain temperature: results of an anthropomorphic skull model.
abstract: OBJECTIVE
  Transtemporal sonothrombolysis is a tool for a more effective treatment in acute stroke patients. However, some reports revealed side effects, which might be potentially connected to temperature elevation. To gain better insight into cerebral temperature changes during transtemporal sonication, diagnostic and therapeutic ultrasound (US) applications were evaluated using an anthropomorphic skull model.
  
  
  METHODS
  The impact of diagnostic (PW-Doppler, 1.8-MHz, 0.11 W/cm², TIC 1.2) and therapeutic (1-MHz and 3-MHz, 0.07 - 0.71 W/cm², continuous and pulsed mode) US application on temperature changes was evaluated at the level of muscle/temporal bone (TB), TB/brain, brain and at the middle cerebral artery (MCA) using 4 miniature thermocouples along the US beam. Sonication lasted 120 minutes.
  
  
  RESULTS
  Diagnostic ultrasound revealed a maximum temperature increase of 1.45°/0.60°/0.39°/0.41°C (muscle/TB, TB/brain, brain, MCA) after 120 minutes. Therapeutic-1-MHz ultrasound raised temperature by 4.33°/2.02°/1.05 °C/0.81°C (pulsed 1:20) and by 10.38°/4.95°/2.43°/2.08°C (pulsed 1:5) over 120 minutes. Therapeutic-3-MHz US raised temperature by 4.89°/2.56°/1.24/1.25°C (pulsed 1:20) and by 14.77°/6.59°/3.56°/2.86°C (pulsed 1:5) over 120 minutes, respectively. Continuous application of therapeutic US (1-MHz and 3-MHz) led to a temperature increase of 13.86°/3.63°/1.66°/1.48°C and 17.09°/4.28°/1.38/0.99°C within 3 minutes.
  
  
  CONCLUSIONS
  Diagnostic PW-Doppler showed only a moderate temperature increase and can be considered as safe. Therapeutic sonication is very powerful in delivering energy so that even pulsed application modes resulted in significant and potentially harmful temperature increases.
authors.affiliation: Department of Internal Medicine II, Division of Cardiology, Medical University Vienna, Austria.
authors.forename: S
authors.initials: S
authors.lastname: Pfaffenberger
authors.forename: E
authors.initials: E
authors.lastname: Vyskocil
authors.forename: C
authors.initials: C
authors.lastname: Kollmann
authors.forename: E
authors.initials: E
authors.lastname: Unger
authors.forename: C
authors.initials: C
authors.lastname: Kaun
authors.forename: S
authors.initials: S
authors.lastname: Kastl
authors.forename: C
authors.initials: C
authors.lastname: Woeber
authors.forename: G
authors.initials: G
authors.lastname: Nawratil
authors.forename: K
authors.initials: K
authors.lastname: Huber
authors.forename: G
authors.initials: G
authors.lastname: Maurer
authors.forename: M
authors.initials: M
authors.lastname: Gottsauner-Wolf
authors.forename: J
authors.initials: J
authors.lastname: Wojta
mesh_terms: D001833:Body Temperature Regulation / Q000502:physiology*; D001921:Brain / Q000503:physiopathology*; D002544:Cerebral Infarction / Q000000981:diagnostic imaging* / Q000628:therapy*; D006361:Heating / Q000009:adverse effects*; D006801:Humans; D066298:In Vitro Techniques; D020767:Intracranial Thrombosis / Q000000981:diagnostic imaging* / Q000628:therapy*; D061185:Mechanical Thrombolysis / Q000009:adverse effects* / Q000295:instrumentation / Q000379:methods*; D019047:Phantoms, Imaging; D014159:Transducers; D014464:Ultrasonic Therapy / Q000009:adverse effects* / Q000295:instrumentation / Q000379:methods*; D017585:Ultrasonography, Doppler, Transcranial / Q000009:adverse effects* / Q000295:instrumentation / Q000379:methods*