Volume 16 (2010): Issue 2 (January 2010)

In order to optimize the accuracy of imaging in Gamma Knife radiosurgery using the image fusion options available in the Leksell gamma plan. Phantom images from 1.5 Tesla MRI Scan (Magnetom vision - Siemens) and Computed Tomography images from Philips Brilliance 16 CT scanner were used for image fusion in Gammaplan treatment planning system. The images were fused using co-registration technique using multiview and imagemerge modules. Stereotactic coordinates were then calculated for known targets. Vector distances from the centre of the Leksell coordinate system to five known targets were measured in CT, MR and CT-MR fused images and compared with geometrical measurements. The mean values of maximum absolute errors were 0.34 mm, 0.41 mm.0.38 mm (along x-axis), 0.43 mm, 1.53 mm, 0.62 mm (along y-axis) and 0.75 mm 2.02 mm, 0.93 mm (along z-axis) for CT, MR and CT-MR fused image data respectively. The mean error in calculating the vector distances from the center of the Leksell coordinate system (100, 100, 100) to the known target volumes are 0.22 mm, 0.8 mm and 0.43 mm for CT, MR and CT-MR fused images, respectively. Image fusion functions available in gamma plan are useful for combining the features of CT and MR imaging modalities. These methods are highly useful in clinical situations where the error associated with Magnetic Resonance Imaging is beyond acceptable levels.

The effects of long term mental arithmetic task on psychology are investigated by subjective self-reporting measures and action performance test. Based on electroencephalogram (EEG) and heart rate variability (HRV), the impacts of prolonged cognitive activity on central nervous system and autonomic nervous system are observed and analyzed. Wavelet packet parameters of EEG and power spectral indices of HRV are combined to estimate the change of mental fatigue. Then wavelet packet parameters of EEG which change significantly are extracted as the features of brain activity in different mental fatigue state, support vector machine (SVM) algorithm is applied to differentiate two mental fatigue states. The experimental results show that long term mental arithmetic task induces the mental fatigue. The wavelet packet parameters of EEG and power spectral indices of HRV are strongly correlated with mental fatigue. The predominant activity of autonomic nervous system of subjects turns to the sympathetic activity from parasympathetic activity after the task. Moreover, the slow waves of EEG increase, the fast waves of EEG and the degree of disorder of brain decrease compared with the pre-task. The SVM algorithm can effectively differentiate two mental fatigue states, which achieves the maximum classification accuracy (91%). The SVM algorithm could be a promising tool for the evaluation of mental fatigue.

Fatigue, especially mental fatigue, is a common phenomenon in modern life, is a persistent occupational hazard for professional. Mental fatigue is usually accompanied with a sense of weariness, reduced alertness, and reduced mental performance, which would lead the accidents in life, decrease productivity in workplace and harm the health. Therefore, the evaluation of mental fatigue is important for the occupational risk protection, productivity, and occupational health.

Ten patients with cancer of uterine cervix who underwent interstitial brachytherapy using MUPIT templates were CT scanned (CT1) using which bladder, rectum and CTV were delineated. The treatment plan PCT1 was generated and optimized geometrically on the volume. CT scan (CT2) was repeated before the second fraction of the treatment CTV and critical organs were delineated. The plan (PCT2) was created by reproducing the Plan PCT1 in the CT2 images and compared with PCT1. Bladder, Rectum and CTV percentage volume variation ranges from +28.6% to -34.3%, 38.4% to -14.9% and 8.5% to -15.2% respectively. Maximum dose variation in bladder was +17.1%, in rectum was up to +410% and in CTV was -13.0%. The dose to these structures varies independently with no strong correlation with the volume variation. Hence it is suggested that repeat CT and re-planning is mandatory before second fraction execution.

Quality control (QC) in radiology is meant to ensure that accurate diagnoses are obtained with radiation doses kept as low as reasonably achievable. It is also a fundamental requirement by the Regulatory Authorities in issuing operational license to operators of radiology facilities. In Nigeria, QC issues in Radiation Medicine have recently been introduced and are being enforced by the Nigerian Nuclear Regulatory Authority (NNRA). The level of QC practice in the radiology facilities in Cross River State, Nigeria was evaluated to obtain baseline information that could be relied on in the future to determine the level of improvement. It was observed that radiology practitioners appreciate QC and its importance in their practice, the present low level of its implementation notwithstanding.

This paper presents a model of the human circulatory system with the possible addition of a parallel assist device, which was developed for the purpose of artificial heart monitoring. Information about an identification experiment of an extracorporeal ventricle assist device POLVAD is included. The modelling methods applied and the corresponding functional blocks in a PExSim package are presented. The results of the simulation for physiological conditions, left ventricle failure and pathological conditions with parallel assistance are included.