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Aim of Study: The goal of this research was to investigate if application of optimized imaging parameters, recommended in literature, would be effective in producing the image quality required for treatment planning of spinal radiation fields with metallic implants. Materials and Methods: CT images from an anthropomorphic torso phantom with and without spinal implants were acquired using different imaging protocols: raising kVp and mAs, reducing the pitch and applying an extended CT scale (ECTS) technique. Profiles of CT number (CT#) were produced using DICOM data of each image. The effect of artifact on dose calculation accuracy was investigated using the image data in the absence of implant as a reference and the recommended electron density tolerance levels (Δρe). Results: Raising the kVp was the only method that produced improvement to some degree in CT# in artifact regions. Application of ECTS improved CT# values only for metal. Conclusions: Although raising the kVp was effective in reducing metallic artifact, the significance of this effect on Δρe values in corrected images depends on the required tolerance for treatment planning dose calculation accuracy. ECTS method was only successful in correcting the CT number range in the metal. Although, application of ECTS method did not have any effect on artifact regions, its use is necessary in order to improve delineation of metal and accuracy of attenuation calculations in metal, provided that the treatment planning system can use an extended CT# calibration curve. Also, for Monte Carlo calculations using patient's images, ECTS-post-processed-CT images improve dose calculation accuracy for impure metals
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Objective@#To explore the mechanism and influencing factors of mirror-image artifact of color blood flow (MACBF) due to longitudinal strong echo big interface (LSEBI).@*Methods@#Fifty suspicious patients with MACBF beside the main pulmonary artery and/or the left pulmonary artery undergoing echocardiography examination from November 2018 to April 2019 in Shengjing Hospital of China Medical University were chosen as the subjects. Image characteristics of the MACBF were observed, and mechanism and influence factors of the MACBF were explored with Doppler imaging principle.@*Results@#Of all the subjects with MACBF, 36 subjects occurred only on the left side of the main pulmonary artery, 14 subjects occurred on both the left side of the main pulmonary artery and the left pulmonary artery. The LSEBI was found between the real color blood flow (RCBF) and the MACBF, there was a mirror relationship between the RCBF and the MACBF. The LSEBI on the left of the main pulmonary artery and the left pulmonary artery were the interface of the left lung and pleural. The signal strength of MACBF enhanced as the distance between the blood flow and the LSEBI got closer or the gain of the color blood flow got bigger.@*Conclusions@#MACBF may caused by LSEBI beside vessel. The formation of MACBF and its signal strength are influenced by the distance between blood flow and LSEBI and the gain of the color blood flow.
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Objective To explore the mechanism and influencing factors of mirror-image artifact of color blood flow (MACBF) due to longitudinal strong echo big interface (LSEBI).Methods Fifty suspicious patients with MACBF beside the main pulmonary artery and/or the left pulmonary artery undergoing echocardiography examination from November 2018 to April 2019 in Shengjing Hospital of China Medical University were chosen as the subj ects.Image characteristics of the MACBF were observed, and mechanism and influence factors of the MACBF were explored with Doppler imaging principle.Results Of all the subjects with MACBF,36 subjects occurred only on the left side of the main pulmonary artery,14 subj ects occurred on both the left side of the main pulmonary artery and the left pulmonary artery.The LSEBI was found between the real color blood flow (RCBF) and the MACBF,there was a mirror relationship between the RCBF and the MACBF.The LSEBI on the left of the main pulmonary artery and the left pulmonary artery were the interface of the left lung and pleural.The signal strength of MACBF enhanced as the distance between the blood flow and the LSEBI got closer or the gain of the color blood flow got bigger.Conclusions MACBF may caused by LSEBI beside vessel.The formation of MACBF and its signal strength are influenced by the distance between blood flow and LSEBI and the gain of the color blood flow.
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The hardware and software faults in the image guidance system may cause ring-shaped artifacts,which is more commonly induced by the aging of the hardware.During troubleshooting,the first step should be checking whether there are obvious faults in the basic hardware.Subsequently,OBI background image is collected to confirm the bad point status.If the bad point is not shielded,it can be compensated by updating the image processing bad point.The invoked Pixel Correction Maps are adopted compensate for the bad point and calibrate the image.If it is still unable to repair,replacing the detection board can be considered.Cone-beam CT (CBCT) image guidance system is an important approach to verify the position orientation and positioning accuracy in modem radiotherapy,which effectively guarantees for the safety and accuracy of radiotherapy.We should fully understand its law of aging,maintain the equipment on a regular basis and verify the image quality to ensure the normal operation of the equipment.
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A comprehensive overview of CR equipment in the system to use various types of image artifacts and accurate analysis of the reasons for the formation of artifacts; described in detail to avoid and eliminate the artifact method, and measures to solve the work encountered in the actual artifacts of the problem.