Exploring the impedance-matching effect in terahertz reflection imaging of skin tissue.

Terahertz (THz) electromagnetic waves, known for their unique response to water, offer promising opportunities for next-generation biomedical diagnostics and novel cancer therapy technologies. This study investigated the impedance-matching effect, which enhances the efficiency of THz wave delivery into tissues and compensates for the signal distortion induced by the refractive index mismatch between the target and the sample substrate. Three candidate biocompatible materials, water, glycerol, and petroleum jelly were applied to a skin phantom and compared using THz two-dimensional imaging and time-of-flight imaging methods. Finally, we successfully demonstrated impedance-matching effect on mouse skin tissues.

Cranioplasty effect on the cerebral hemodynamics and cardiac function.

BACKGROUND: Cranioplasty is usually performed for aesthetic, protective and patient comfort reasons. The objective of this study is to examine the effects of cranioplasty on the cerebral hemodynamics and cardiovascular system. METHODS: Twenty-seven patients who had undergone cranioplasty after extensive skull bone removal to prevent uncontrollable intracranial hypertension were included in this study. Arterial blood flow velocities in the middle cerebral artery (MCA) and internal carotid artery (ICA) were assessed by transcranial doppler (TCD). The cardiac functions were evaluated using the echocardiogram. And cerebral blood flow were measured by perfusion CT. FINDINGS: The blood flow velocity at the MCA ipsilateral to the cranioplasty was decreased from 50.5 +/- 15.4 cm/s preoperative to 38.1 +/- 13.9 cm/s following cranioplasty (p < 0.001) and from 33.1 +/- 8.3 cm/s to 26.4 +/- 6.6 cm/s at the ICA (p < 0.001). The stroke volume was increased from 64.7 +/- 18.3 ml/beat, to 73.3 +/- 20.4 ml/beat (p < 0.001), while the cardiac output and mean arterial blood pressure were unchanged. The cerebral blood flow was increased from 39.1 +/- 7.2 ml/100g/min to 44.7 +/- 8.9 ml/100g/min on the cranioplasty side (P = 0.05). CONCLUSIONS: Cranioplasty can get rid of the atmospheric pressure on the brain and increase the cerebral blood flow as well as improve the cardiovascular functions. A skull defect should be corrected, because cranioplasty has not only aesthetic or protective effects but also improves the cardiovascular functions.