Computed Tomography Equipment Techniques PDF

Middle Technical University (MTU) College of Health and Medical Techniques -Baghdad Radiological Techniques Department Computed Tomography EquipmentsTechniques Second stage/ 2nd coarse Title: Advanced technical CT applications CT Angiography Cardiac CT imaging CT flouroscopy Name of the instructor:...

Middle Technical University (MTU) College of Health and Medical Techniques -Baghdad Radiological Techniques Department Computed Tomography EquipmentsTechniques Second stage/ 2nd coarse Title: Advanced technical CT applications CT Angiography Cardiac CT imaging CT flouroscopy Name of the instructor: Lec. Dr. Lamyaa Fadhil Abdul Hussein Target population: Students of second class 106 CT Angiography CT angiography is defined as CT imaging of blood vessels opacified by contrast media. During contrast injection, the entire area of interest is scanned with spiral/helical CT and images are recorded when vessels are fully opacified to show arterial or venous phases of enhancement. CT angiography uses 3D imaging principles to display images of the vasculature through intravenous injection of contrast media compared with those of intraarterial angiograms. Four essential elements are patient preparation; selection of acquisition parameters (total spiral/helical scan time, slice thickness, table speed) to optimize the imaging process; contrast media injection; and postprocessing techniques and visualization tools such as algorithms to display 3D images, multiplanar reconstruction, maximum intensity projection. Cardiac CT Imaging To image the beating heart with the goal of reducing motion artifacts and a loss of both spatial and contrast resolution, fast CT scanners such as the EBCT scanner were introduced to overcome these problems and produce good diagnostic images of the prospective imaging, after it is recorded at the same time with the scanning with stop and go scanners. Subsequently, retrospective imaging has been developed where the ECG is correlated with image reconstruction in spiral/helical CT scanning. The recent technical developments in MSCT scanners and the introduction of the DSCT scanner open up a whole new avenue for successful imaging of the heart with excellent image quality based on meeting several technical requirements. These include lowcontrast resolution to visualize small differences in tissue contrast, high-contrast 107 resolution (spatial resolution) to visualize small structures in the anatomy scanned, to image fast-moving objects to reduce motion artifacts. These have all been made possible by fast data acquisition and dedicated reconstruction algorithms, such as the for merging synchronized transmission data from successive heart cycles. So, cardiac CT is routinely performed to gain knowledge about cardiac or coronary anatomy, to detect or diagnose coronary artery disease (CAD), to evaluate patency of coronary artery bypass grafts or implanted coronary stents. Artifacts Several artifacts can potentially occur and include: motion artifact o cardiac motion o respiratory motion o gross patient motion partial volume averaging beam hardening metal or streak artifact slab or banding artifacts poor contrast enhancement artifacts from overlapping structures CT Fluoroscopy CT fluoroscopy, or continuous imaging, depends on spiral/helical data acquisition methods, high-speed processing, and a fast image-processing algorithm for image reconstruction. 108 In conventional CT, the time lag between data acquisition and image reconstruction makes realtime display of images impossible. CT fluoroscopy allows for the reconstruction and display of images in real time with variable frame rates. CT fluoroscopy is based on three advances in CT technology: (1) fast, continuous scanning made possible by spiral/helical scanning principles. (2) fast image reconstruction made possible by spe- cial hardware performing quick calculations and a new image reconstruction algorithm. (3) continuous image display by use of cine mode at frame rates of two to eight images per second. Other support tools were developed to facilitate interventional procedures in CT fluoroscopy. One such tool, the Fluoro Assisted Computed Tomography System, uses a unique flat-panel amorphous silicon digital detector coupled with an x-ray tube by a C-arm, which is a part of the CT gantry. References 1. Stewart Carlyle Bushong, Elsevier, Inc. , 7th edition, 2017. 2. Chris Guy & Dominic ffytche, Imperial College Press, 2005. , 3. Perry Sprawls, , 2nd Edition 1996. 4. J. Hsieh, "Computed Tomography: Principles, Design, Artifacts, and Recent Advances", 2nd ed. Wiley Inter-science, Bellingham, Washington, USA, (2009) 5. Lee W. Goldman Technology September 2007, 35 (3) 115-128. , Journal of Nuclear Medicine 109