Application of reconstruction technique in the CT scan of nasal traumas / 重庆医学

Objective To evaluate the value of the SAFIRE reconstruction technique for the nasal traumatic lesions .Methods Six‐ty‐seven patients with nasal traumas were scanned by the orbital scan and were reconstructed with FBP and SAFIRE (strength grade 1 to 5) respectively .Then a comparative analysis for six kinds of reconstructed images were conducted on the average CT value ,noise ,signal to noise ratio (SNR) ,contrast to noise ratio (CNR) ,subjective scoring and lesion detection .Results Compared with reconstruction by FBP , SAFIRE (strength grade 1 to 5)reconstruction ,for the noise ,decreased to 20 .4% ,31 .4% ,39 .7% ,46 .5% and 57 .2% respectively ;For the SNR ,increased to 33 .3% ,54 .7% ,75 .4% ,87 .4% and 101 .4% respectively ;For the CNR ,it also increased to 23 .0% ,36 .4% ,57 .7% , 87 .4% and 106 .5% respectively ;The difference was statistically significant (P< 0 .05) .For the images of SAFIRE‐1 and SAFIRE‐5 ,the image subjective scoring was lower than that by FBP ;for the images of SAFIRE‐2 and SAFIRE‐4 ,the image subjective scoring was higher than that by FBP ;and SAFIRE‐3 had the highest score .But for the rate of lesion detection ,all the images were the same .Conclusion CT scan combined SAFIRE reconstruction technique can decrease effectively the noise and increase the image quality in the traumatic nasal scan , as well as has a potential effect to decrease the scan dose .

Optimizing Imaging Conditions in Digital Tomosynthesis for Image-Guided Radiation Therapy / 의학물리

Cone-beam digital tomosynthesis (CBDT) has greatly been paid attention in the image-guided radiation therapy because of its attractive advantages such as low patient dose and less motion artifact. Image quality of tomograms is, however, dependent on the imaging conditions such as the scan angle (beta(scan)) and the number of projection views. In this paper, we describe the principle of CBDT based on filtered-backprojection technique and investigate the optimization of imaging conditions. As a system performance, we have defined the figure-of-merit with a combination of signal difference-to-noise ratio, artifact spread function and floating-point operations which determine the computational load of image reconstruction procedures. From the measurements of disc phantom, which mimics an impulse signal and thus their analyses, it is concluded that the image quality of tomograms obtained from CBDT is improved as the scan angle is wider than 60 degrees with a larger step scan angle (Delta beta). As a rule of thumb, the system performance is dependent on . If the exact weighting factors could be assigned to each image-quality metric, we would find the better quantitative imaging conditions.

Design and realization of filtered backprojection algorithms of CT image reconstruction based on FHT and MSBP / 医疗卫生装备

Filtered backprojection algorithms are widely used in the commercial CT systems.The projection data and the object functions all belong to the real number area in applications of CT image reconstruction.The reconstruction algorithm based on Fourier transform involves lots of complex number operations.It's an inherent characteristic in computation.Because of the real number transform characteristic of Hartley transform comparing with Fourier transform,the signals and images in the real number area can be processed using Hartley transform instead of Fourier transform.Based on the geometrical relationships between image pixels and projection rays at different viewing angles,a Multi-orientation simultaneous computation of backprojection for tomographic image reconstruction(MSBP) approach is proposed.In this paper,the filtered backprojection algorithms of CT image reconstruction are realized by using FHT and MSBP.The algorithms may lead to the reduction of the memory space and can reduce the amount of calculation while retaining the precision.