A study of brain-computer interface paradigm based on mental arithmetic / 生物医学工程学杂志

In the traditional P300 brain-computer interface (BCI) system, the electroencephalogram (EEG) signals can only provide limited information with a low signal-to-noise ratio. A BCI paradigm under visual stimulus was proposed in our study aiming to effectively activate the related brain areas and response signal while dealing with specific cognitive task (mental arithmetic task), so as to enhance the EEG signals. The result was compared with the traditional P300 counting task paradigm. Then the collected EEG data were preprocessed including extracting signal features with coherent averaging method, and analyzing the influences of different experimental paradigms on main components of event related potential (ERP). In the improved paradigm experiments the average increasing rate of P300 amplitude was 6. 83MV (73. 94%). The brain activity from 400ms was more active and lasted longer. Besides, unlike traditional counting task, mental arithmetic task appeared to have apparent activation at 650ms. The results showed that the improved paradigm could activate the related brain areas better and enhance the characteristics of signal. This provides a new system paradigm for BCI.

The Effect of the Position Change of the Upper Limbs to the Setup Accuracy in the Practice of Immobilizing the Thoracic Cancer Patients by Using Vacuum Bags and Body Frames / 中国医学物理学杂志

Objective: To explore the position change of the setup reference markers on the sternum due to the change of hands grip position. Methods: Six hands grip positions were simulated for 8 patients and the set-up reference points marked on the sternum skin were compared while the hands grasped different positions of the hands. Results: The setup markers on the sternum were deviated by all five hands grip positions. The maximum deviated distance was 14mm. Conclusion: The change of the hands grip position can affect the position of setup reference markers on the sternum of the patients and thus the isocenter of plan may be aligned to the wrong area.

Comparison Between Two Marking Methods in CT/MRI Image Registration / 医疗卫生装备

Objective To compare the results of CT/MRI registration by using two different marker materials. Methods CT and MR transversal images (using electric wire and thin tube filled with lohexol injection as matching points respectively) were obtained from nine cases with brain tumor. Another CT and MR transversal images were also obtained by using the cod-liver oil capsule filled with gadopentetate dimeglumine injection as matching points with the same scanning position. The images were transferred to the TPS for image registration and the effect was evaluated. Results The CT/MRI CRE range for using different kinds of marker material was 0.16-0.28cm,while was 0.06-0.16cm for using the same marker material. Conclusion Comparing with the method using different kinds of material,the method using the same spherical material can get better results in CT/MRI registration.