DAS/computer system & image reconstruction

analog-to-digital converter (ADC) is a component of the?

DAS

Path of data from dectors to output devices (the order it travels)

Detectors DAS computer system & array processor Output devices

e in the equation is? actual number?

Euler's constant (2.718)

Special cone beam reconstruction algorithms

Examples Feldkamp- Davis-Kress (FDK) and advanced single-slice rebinning (ASSR) algorithms.

Iterative reconstruction was historically used for image reconstruction in some of the earliest CT systems, dating back to

Hounsfield's original work. (1st gen)

Lambert-Beer equation

I=Ioe^ux

= log

Intensity of x-ray at the source (lo) /Intensity of x-ray at the detector (1)

an additional feature of CT com- puter systems that further improves the speed and efficiency with which it can perform multiple simultaneous functions,

Pipelining

Form of data when it comes to computer system and form when it leaves

Raw data ———> image data

common choice for mass storage of CT computer system data.

The hard disk drive

model-based iterative reconstruction considers what?

This advanced technique beam both considers shape of the CT x-ray prepatient and postpatient, and uses complex statistical analyses in both a forward and backward series of reconstructions to arrive at an improved image with reduced noise.

During MDCT, the DAS is responsible for controlling the signal emitted from the

activated detectors exposed to the collimated x-ray beam.

z-filtering during image reconstruction.

allows for thin sections to be reconstructed at any point along the acquired z-axis volume.

From the thousands of ray sum measurements acquired, the computer system generates an ___________ _________

an attenuation map,

convolution is applied to do what

applied to reduce image unsharpness.

The primary data processing component of the CT system is the

array processor.

reduction in intensity of the x-ray quantum as it travels along from tube to detector.

attenuation,

The mathematical process primarily responsible for image reconstruction is called

back-projection.

Adaptive iterative reconstruction

begins with data analysis using standard FBP algorithms. This is fol- lowed by comparisons between the measured pixel values and those of an ideal data set. Through a repeated comparison process, new pixel values are calculated, resulting in a final image that approaches an ideal, noise-free version (iteration).

The smallest unit of information used in the binary language of computers is the :

bit

Interpolation of data from a shorter distance away along the z-axis reduces

blurring and improves image quality.

CT computer system :The central processing unit (CPU) does what?

capable of performing multiple tasks simultaneously,

Image reconstruction for MDCT helical acquisition is complicated further by the addition of cone beam geometry. The rays measured from a more divergent beam arrive at the detector at an oblique angle, which must be

compen- sated for during the reconstruction process.

An algorithm or also know as

con- volution kernel

analog-to-digital converter (ADC) is the responsible for

converting the electronic signal into digital form.

The DAS of a MDCT system has a maximum number of _________ ________ used to transmit data from the detectors to the computer system for image reconstruction.

data channels

The Lambert-Beer equation is valid only for homo- geneous pencil-beam radiation sources, such as

first-generation CT system developed by Hounsfield.

Once the reconstruction is completed, the process raw data (ray sum or transmission measurements) is displayed as what kind of data?

image data,

The ability of an object to attenuate the X-ray beam assigned a value termed

linear attenuation coefficient (u).

The operating system (OS)

main software of the CT computer.

Interpolation

mathematical process whereby data from tube rotations just above and just below a given slice position are used for image reconstruction.

The DAS consists of electronic components responsible for

measuring the transmitted x-radiation absorbed by the detectors. Also converts and transmits

of iterative reconstruction second-generation type technique known as

model-based iterative reconstruc- tion

x is

object thickness.

The number of data channels controls the number

of slices the system can acquire with each gantry rotation.

The central processing unit (CPU) is capable of performing multiple tasks simultaneously, a function called

parallel processing.

The VPR determines the

quantity of samples,

The Lambert-Beer equation illustrates the relationship between

radiation intensity and object density

measurement of transmitted radiation made by an individual detector is called

ray sum.

The portion of the x-ray beam transmitted through the patient and incident upon a single detector is

ray,

An algorithm or convolution kernel acts as a mathematical filter, modifying the ray sum data and? due to the effect of what

removing the unwanted blurring effect of the back-projection.

The array processor is responsible for receiving

scan data from the host computer, performing all of the major processing of the CT image, and returning the reconstructed image to the storage memory of the host computer.

The resultant images of this initial, or prospective, reconstruction are evaluated by a radiologist, further manipulated in 3-D or MPR, archived to long-term storage, and so on. ybod Multiple data reconstructions can be performed retrospectively, The projection (raw) data must be available within the system to perform

such retrospective reconstructions.

iterative techniques are commonly employed to reduce what two factors?

techniques reduce image noise and allow for significant reductions in technical factors, thus reducing patient dose.

back-projection of ray sum data onto a matrix combined with mathematical filtration is the basis what was historically the most common employed basic method of image reconstruction for the modern MDCT

the filtered back projection (FBP).

Attenuation values are calculated by mathematically comparing (basically a formula)

the radiation incident the patient upon (Io) to the radiation transmitted through and measured by the detector (I).

back-projection.

the ray sum data acquired from each projection (data sample) is projected back onto a matrix.

operating system (OS) controls

the utilization of the hardware resources, such as the available memory, CPU time, and disk space.

Interpolation allows for the reconstruction of a? WHAT TYPE OF INTENSE WOULD IT BE USED IN

thin, motion-free image from a volumetric data set acquired from a moving patient.

360-degree linear interpola- tion (360LI)

uses two sets of projection data acquired 360 degrees apart to form an image at a precise z-axis location.

The term used to describe each data sample made by the DAS.

view

The sampling rate may be called what

views per rotation (VPR),

The extent of attenuation depends on multiple factors,

x-ray energy and the atomic structure and density of the exposed tissue.

A standard CT image reconstructed on a 512² matrix has a digital size of approximately

0.5 MB

Interpolation technique used More commonly used for current MDCT

180-degree linear interpolation technique (180LI).

A matrix is a

2-D grid of numbers arranged in rows and columns.

helical data acquisition, the patient bed is continuously feeding through the gantry as the tube and detector array rotate. Therefore no single slice of patient anatomy is ever exposed to a full

360 degrees of evaluation.

iterative reconstruction techniques cur- rently employed on CT systems from most major industry vendors. (which one)

Adaptive