CT成像原理介绍(英文版)

X 线计算机断层摄影术

CT 成像原理介绍 成像原理介绍

X 线计算机断层摄影术

Computed TomographyCT Basics Principle of Spiral CT Scan Parameter & Image Quality Optimizing Injection Protocols Clinical Applications

X 线计算机断层摄影术

X-Ray DiscoveryX-ray was discovered by a German scientist Roentgen 100 years ago. This made people for the first time

be able toview the anatomy structure of human body without operation But it's superimposed And we couldn't view soft tissue

X 线计算机断层摄影术

History of Computed Tomography1963 - Alan Cormack developed a mathematical method of reconstructing images from x-ray projectionsMy name is Godfrey Hounsfield I work for the Central Research Labs. of EMI, Ltd in England I developed the the first clinically useful CT scanner in 1971

Early 1970s

X 线计算机断层摄影术

CT Broke the BarrierFor the first time we could view: - Tomographic or “Slice” anatomy - Density differenceBut it's time consuming And resolution needs to be improved

X 线计算机断层摄影术

Concept of X-ray Attenuation XAn X-ray beam passing through Xthe body is attenuated (loses its energy) by : Absorption Scattering Incident X-rayBODY TISSUE SCATTERED XXRAYS

Transmitted ray

Absorption by the tissue is proportional to the density

More dense tissue

Less dense tissue

MORE ATTENUATION

LESS ATTENUATION

X 线计算机断层摄影术

How does CT Work?X-ray generation Data acquisition Recon. & postpro.

X 线计算机断层摄影术

How does CT Work?

X-ray goes through collimator therefore penetrate only an axial layer of the object, called

"slice"

X 线计算机断层摄影术

How does CT Work?Patient is placed in the center of the measurement field X-ray is passed through the patient’s slice from many direction along a 360° path ° The transmitted beams are captured by the detectors which digitizes these signals These digitized signals called raw data are sent to a computer which create the CT image

X 线计算机断层摄影术

How is CT Image generated?The object slice is divided into small volume elements called voxels. Each voxel is assigned a value which is dependent on the average amount of attenuation

X 线计算机断层摄影术

How is CT Image generated?The attenuation values are transferred to the computer where they are coded & used to create a slice image

X 线计算机断层摄影术

CT Generations & Design“Generation” is used to label CT tube-detector tubedesigns

3rd Generation Design Rotating tube & detector

4th Generation Design Fixed ring detector

X 线计算机断层摄影术

SlipSlip-ring TechnologyPower is transmitted through parallel sets of conductive rings instead of electrical cables

Continuous Gantry Rotation Prerequisite for Spiral CT

Non Slip-ring Scanner Slip-

SlipSlip-ring Scanner

X 线计算机断层摄影术

Computed TomographyCT Basics Principle of Spiral CT Scan Parameter & Image Quality Optimizing Injection Protocols Clinical Applications

X 线计算机断层摄影术

What is Spiral Scan? -- just 4“C”

Continuously rotating tube/detectorsystem

Continuously generating X-ray XContinuously table feed Continuously data acquisition

X 线计算机断层摄影术

Continuous data acquisition

A

Volume Data

B

Reconstruction of arbitrary slices (either contiguous or overlapping) within the scanned volume Distance between the slices is called Increment