Ct Applications PDF

CT Applications  The clarity and accuracy of images produced by CT scanners have enabled CT to become one of the most widespread modalities for diagnostic imaging. 1/Cardiac Imaging  There are two general types of cardiac applications: 1/coronary artery calcification and 2/cor...

CT Applications  The clarity and accuracy of images produced by CT scanners have enabled CT to become one of the most widespread modalities for diagnostic imaging. 1/Cardiac Imaging  There are two general types of cardiac applications: 1/coronary artery calcification and 2/coronary artery imaging. Volume-rendered image of a cardiac CT scan.  Coronary artery calcification examination. Arrows in the figure indicate locations of calcium. Reformatted image of a CT cardiac scan to illustrate the third dimension of the calcification. Illustration of stenosis as a result of plaque. (a) An x-ray angiographic example and (b) an example from CT CAI. Calculation of ejection fraction from CAI. (a) End-systole phase and (b) enddiastole phase. 2/CT Fluoroscopy Artist’s rendered version of CT fluoroscopy operating suite Examples of a biopsy operation. (a) Biopsy needle just entering the patient. (b) Biopsy needle en route to target. (c) Biopsy needle farther en route to target. (d) Biopsy needle reaching the target Depth-weighted volume-rendered view of a biopsy procedure.  3/CT Perfusion Perfusion images of a head scan. Upper left: CT image of a head scan with contrast injection. Upper right: contrast uptake curves in the vessels. Lower left: blood flow image. Lower right: mean- transit-time image.  Perfusion images of a body scan. Upper left: original CT scan. Upper right: contrast uptake curves in the vessels. Lower left: blood volume, blood flow, mean transit time, and permeability surface images. Lower right: blood volume image. Blood flow map of a brain perfusion study with (a) x ray on continuously and (b) x ray on every three seconds. 4/Screening and Quantitative CT  Slowly but surely, CT is moving into the area of screening. Screening implies that the patient under examination is asymptomatic. For CT to be successful in screening, two key enabling technologies must be developed and perfected.  The first is low-dose scans. Since human exposure to x-rays is generally considered harmful, the risks of patient radiation exposure have to be significantly lower than the risks of undetected pathologies that can be treated at early stages to impact the outcome.  In other words, the benefit of CT screening examinations has to outweigh the risks of the additional radiation exposure.  Lung cancer screening Identification of a lung nodule in a CT image (a) Segmentation of a lung nodule and (b) 3D volume-rendered view. 5/Virtual Reality  Bronchoscopy Real Time Fly through Reverse Perspective Axial Image reference High Resolution 18  Virtual Bronchoscopy  Is a branch of computer science that immerses users in computer- generated environment and allows them to interact with 3D scenes. The creation of inner views of tubular structures is called virtual endoscope. Bronchus with carcinoid tumor 3.5p 19  Examples of a CT colonography study. A patient is scanned in both supine (left) and prone (right) positions. (The prone image is shown upside down so that patient orientation is identical to the supine image.) CT colonography CT colonography images: (a) cross-sectional image, (b) reformatted image, (c), “fly through” image, and (d) volume-rendered image. CT Colonoscopy 3.5p 22 CT Colonoscopy 3.5p 23 VIRTUAL ENDOSCOPY 3.5p 24 Flattened and straightened CT colonography image.  CT image quality is typically evaluated using a number of criteria  Spatial resolution describes the ability of a system to define small objects distinctly.  Low-contrast resolution refers to the ability of a system to differentiate, on the image, objects with similar densities.  Temporal resolution refers to the speed that the data can be acquired. This speed is particularly important to reduce or eliminate artifacts that result from object motion, such as those commonly seen when imaging the heart. Disadvantages  Radiation – although CT scans account for only 4% of X-ray examinations, they contribute to more than 20% of the radiation dose to the population by ‘medical X-rays’. For typical doses of common radiological examinations.  Artefacts – an artefact is a feature or appearance that is seen on an image,which does not actually exist.