Influence of dental metallic materials on MR imaging / 浙江大学学报·医学版

Magnetic resonance imaging (MRI) technique is one of the most commonly used imaging diagnostic techniques for pate diseases at present.Metal and alloy are commonly used in dental practice. The artifacts on MRI caused by metal and alloy may result in attenuation of signal intensity, image distortion and signal loss, which severely influences imaging quality. So these materials confine the application of MRI on pate. In this paper, the influence of dental metallic materials on MRI is discussed. It expounds the generation and principals of MR artifacts, the influence of artifacts of metal dental prosthetic restoration, the effects of choosing different MR sequences and imaging weight on MRI, as well as how to prevent and diminish artifacts, to provide reference for clinical practice.

Mechanism of acupuncture anesthesia for analgesia of the operative region of thyroid gland / 中国针灸

<p><b>OBJECTIVE</b>To probe into peripheral nervous mechanisms of analgesic effect of electroacupuncture (EA) at Hegu (LI 4) and Neiguan (PC 6) on cervical region.</p><p><b>METHODS</b>Twenty cases of thyroid disease who wished to receive acupuncture anesthesia, were stimulated with electroacupuncture at bilateral Hegu (LI 4), Neiguan (PC 6) in continued wave, intensity of 6-8 V, frequency of 10-20 Hz. After stimulation for 40 min, the operation was made. Before EA stimulation, 10 min, 20 min and 30 min after EA stimulation, changes of the physiologi cal functions including latent period, conduction velocity, wave peak amplitude of great auricular nerve were monitored and changes of pain sense were detected.</p><p><b>RESULTS</b>After EA given at Hegu (LI 4) and Neiguan (PC 6) for 10 min, 20 min and 30 min, the pain sense significantly decreased (P<0.01), the latent period of great auricular nerve was shortened, and the conduction velocity was fastened and the wave peak amplitude raised with significant changes as compared with those before EA stimulation (P<0.01).</p><p><b>CONCLUSION</b>EA at Hegu (LI 4) and Neiguan (PC 6) can produce a better analgesic effect on cervical region; EA at Hegu (LI 4) and Neiguan (PC 6) induces electro-physio logic changes of the nerve innervating the cervical region, showing increase of excitability; the nerves innervating Hegu (LI 4) and Neiguan (PC 6) and the nerves of cervical region possibly are homologous nerves.</p>