Visualization of brain perfusion by contrast-enhanced ultrasonography: preliminary study in rabbits

PURPOSE: We evaluated the usefulness of an agent for contrast-enhanced ultrasonography (galactose parmitine acid: Levovist) in visualizing brain perfusion in rabbits. MATERIALS AND METHODS: Six rabbits were involved in this study. A hole in the skull bone was made under anesthesia and used as an acoustic window. An ischemic model (3 of 6 rabbits) was made by surgically occluding the M1 portion of the middle cerebral artery. Power Doppler images (PDI) and B-mode Harmonic images (HI) before and after intravenous injections of the contrast medium (150 mg/body) were obtained using the HDI5000 (ATL) equipped with a linear-type 5-12 Mhz probe. RESULTS: Smaller arteries were clearly visualized by contrast-enhanced PDI. However, enhancement of brain parenchyma was not clear on PDI. Enhancement of brain parenchyma was observed clearly on contrast-enhanced HI. Enhancement was strong during the first pass and then diminished quickly. In ischemic models, hypoperfusion in the right cerebral hemisphere (the occluded side) were clearly observed on contrast-enhanced HI. CONCLUSION: Brain perfusion in rabbits can be observed on contrast-enhanced Harmonic ultrasonographic imaging. It is suggested to be useful for human clinical cases, including hypoxic ischemic brain injury in infants.     

An excitatory response preceding the silent period in masseter electromyographs

A masseteric excitatory reflex response preceding the silent period which appears following tapping movement of the jaw, was investigated in order to evaluate its origin. In the pre-anaesthetic state, the latency of response did not change with the intensity of tapping. However, its amplitude increased depending on the intensity of tapping. The response did not disappear even after the anaesthesia. After the anaesthesia the lighter the intensity of tapping was, the longer the latency of the response, coming up to that of the jaw-jerk reflex. The pre-anaesthetic response had an intricate wave form comparing with the post-anaesthetic one. From the above findings it was concluded that the response must be a complex one in nature originating in the muscle spindle of jaw closing muscles and in a certain receptor of the structures surrounding the tooth.