The biological principle of genetic code and genetic computation in natural selection is discussed and a new frame of genetic computation is proposed.

Objective To develop a fast shimming method for permanent magnet MRI system. Methods Peak location method (PLM) was improved by calculating the eddy current effect, and the time deviation was replaced by their phase to increase the precision. Results Experiment showed that the new method took less than 45 s, which was 3 times faster than conventional method while providing the same homogeneity. The result of PLM satisfied the requirement of homogeneity. Conclusion This new method can significantly improve the homogeneity in a short time and satisfy further fast pulse sequence development on 0.5T permanent magnet MRI system, which can be generalized for any permanent magnet first order shimming.

0.05).Conclusion It is feasible to implement the DWS pulse sequence in conventional MR system to investigate the diffusion property of water molecule,furthermore the results are not dependent on diffusion weighting.

Objective: Bladder cancer is the ninth cause of cancer deaths and has high recurrence rate after resection of the tumors. Cystoscopy is the current most accurate method for investigating the bladder abnormalities. However, it is expensive, uncomfortable and invasive. It is possible to induce bleeding, urinary-tract infection and even puncture of bladder. Advances in medical imaging and computer technologies make virtual cystoscopy a potential alternative. Methods: Computed tomography (CT) and magnetic resonance imaging (MR/) are the preferred imaging modalities for virtual cystoseopy to get clear structural images or (and) functional images of the bladder. The boundary of bladder is segmented manually or automatically, and then the bladder is reconstructed and displayed by surface rendering. Useful features are extracted from the images and expressed o nthe reconstructed bladder to provide more valuable diagnosis information for doctors. Results: Comparing with conventional cystuscopy, virtual cystuscopy is noninvasive, more convenient, flexible and can provide more useful diagnosis information as well. Conclusions: Virtual cystoscopy is a promising method of detection and reexamination of bladder cancer. So far, more researches are needed for the virtual cystoscopy before clinical application. It clinical and commercial value are under investigation.

Objective Studies on IMRT technique demonstrates that the improved dose homogeneities throughout the breast as well as reduction in dose to the heart and the ipsi-and control-lateral lungs. Methods Based on the physical principle of rolling tangential technique, a treatment plan for a patient has been planned by using Pinnacle aperture-based inversion software. The rolling tangential IM-beam was pre-determined at each pre-selected gantry angle with normally angle separation of 5?, 10? or 15?. Each beam's width was so chosen that the inner-and outer-edge of the beam should be tangential to the inner chest wall and target outer surface respectively. For the starting and ending tangential beam, a pair of opposing beam was designed. The beam's orientation was suggested to be reversed to its opposite angle when the tangential beam's gantry angle reached 90? or 270?. Each beam's shape and size were adjusted on its BEV map. For each tangential beam, 7 sub-segment beams were chosen for each tangential beam. Then, planning system was allowed to do optimization according to the clinical dose prescriptions. Results The calculated dose distributions in target(CTV), left & right lungs, and heart showed that the volume received the prescribed dose 50?Gy V_ 50 was 0.95; The volume in target enclosed with 95%, 105%, 110%, 115% isodose lines V_ 95% , V_ 105% , V_ 110% , V_ 115% was 0.98, 0.84, 0.53, 0.18, respectively. The volume of V_ 10 ,V_ 20 , V_ 30 , V_ 40 V_ 50 , in the lungs and heart were significantly decreased when compared to the current IMRT techniques published in the literature(Table 1).Conclusions The rolling tangential IM-segment irradiation technique for the breast developed by the author is able to offer not only a better dose distribution and better dose conformity throughout the target, but also reduce significantly the dose to the lungs and heart, with the patient's set up and localization process being very simple. The treatment planning for individual patient is optimal in any treatment planning system with Aperture-Optimization inverse software. This technique is certainly to offer more benefit to the patient if some measures are taken to limit or to follow the movement of the chest wall during irradiation.

Diffusion time and diffusion gradient magnetic strength are two important parameters of the pulsed gradient spin echo (PGSE) that is the most commonly used method in diffusion-weighted magnetic resonance imaging. However, the effects of the diffusion time on the apparent diffusion coefficient (ADC) in previous studies are controversial, and the effects of the diffusion gradient magnetic strength have received little attention. In this study, a new experimental protocol was designed to evaluate the effects of the two parameters on ADC. It was found that ADC decreased significantly with the increase of diffusion time or increase of diffusion gradient magnetic strength, which cannot be explained by the previous theories. Through theoretical analysis, we found the flaw of PGSE method, which is on explanation for the controversial results of diffusion time in former literatures.
Diffusion ; Diffusion Magnetic Resonance Imaging ; methods ; Electromagnetic Fields ; Image Processing, Computer-Assisted ; methods ; Water ; chemistry