CT Fundamentals

The first CT scanners were only capable of reconstructing images in the transverse plane were called ______ ______ ______.

Computerized transaxial tomography or Computed Axial tomography

____ ____ was used in 3rd generation, which can have 800 or more detectors, use a much wider fan beam that encompasses the patient.

Cone Beam

CT tube voltages range from _____ to _____ kilovolts.

90, 140

Two methods of data acquistion are: ______ or ______ acquisition.

(Sequential or slice by slice), (spiral or helical, volume)

The first CT scanner used to image a living human was installed at Atkinson-Morley's in 1971 and the first clinical images were aquired in _____.

1972

In _____ Robert Ledley develovped the first CT scanner capable of imaging the entire body.

1974

_____ ______ is the way in which the x-ray beam passes through the patient and is acquired by the CT detectors.

Beam Geometry

______ plane divides the body into anterior and posterior portion.

Coronal Plane

______ is responsible for amplifying the digitizing the signals from the detectors before they are sent to the computer for processing. _____ has 3 functions: -measures the radiation that is transmitted from the patient -encodes the measurements into binary codes -transmits the binary data to the array processor computer.

DAS-Data acquistion system

Workstations must comply with the ______ standard and be able to connect with PACS, radiology information system and hospital information system.

DICOM standard

_____ _____ refers to the systmatic collection of information from the patient to produce the CT image.

Data Acquisition

____ ____ was introduced in 2nd generation scanners. -x-rays diverged slightly from x-ray source, forming a narrow fan-like shape of about 10 degree -had approx. 30 detectors

Fan Beam

The ______ generation scanners: -allows dynamic imaging of certain structures, especially the heart -Final name given to these scanners is "Electron beam computed tomography" -Often referred to as high speed CT scanners

Fifth Generation

The ______ generation Scanners: -were designed specifically for imaging the head -Used a bag of water called a "head cap" to reduce the dynamic range of the radiation. -Used pencial beam scanning -Took approx 5 minutes for each scan to process. 30 minutes in exam duration.

First Generation

The ______ generation scanners: -Use stationary array of detectors that do not rotate -x-ray tube completes an entire 360 rotation, sending data to hundereds of detectors surrounding the patient. -Once the section of anatomy is scanned, the tube moves in the opposite direction to acquire data from the next section.

Fourth Generation

The pivotal point, where no motion occurs is called the _______.

Fulcrum

The _____ is a mounted framework that surrounds the patient in the vertical plane.

Gantry

The _____ ______ is the opening in which the patient is positioned during the scanning procedure.

Gantry Aperture

_______ components include: -x-ray generator -x-ray tube -detectors -digital acquisition system (DAS) -slip rings -high tension generator -collimators

Gantry Components

_____ _____ _____ varies between systems, but plus or minus 12 to 30 degrees is standard.

Gantry Tilting Range

The first scan and all scans performed with the first generation scanners was of a patient's ____.

Head

Areas of ____ ____ appear white in a CT.

High density

-the x-ray tube and detector system rotate around the patient -x-rays are transmitted through the patient, recorded by the detectors and converted to electrical signals -The signals then transformed into digital data and transferred to a computer. -The computer completes the image reconstruction process, producing digital images that can be displayed, shared, printed and digitally stored.

How CT scanners work

In 1917 _____ _____ a mathematician in the Austro-Hungarian Empire, developed an algorithm that reconstructed a two-or three demensional object based on multiple measures from several different locations. His algorith the ____ _____ was developed for use in integral geometery.

Johann Radon, Radon Transform

Modern detectors are scintillation devices that use a crystal to produce ______ when struck by x-ray photons.

Light

Areas of ___ ___ appear black in a CT.

Low density

Two types of filtration are used in CT _____ and _____.

Mathmatical, Beam-shaping filter

_______ ______ has faster scan times, increased anatomical coverage and thinner slice capabilities for higher resolution images. -use wide beam geometry -detector array covering more than 20mm in the longitudinal, or z-axis direction. -spreads out in 3-D in a shape similar to a narrow pyramid.

Multidetector CT

____ ____-refers to a highly collimated, thin "pencil-shaped" x-ray beam. -used by Hounsfield in the 1st generation scanners -x-ray tube is located on one side of the pt, and one or two detectors located on the opposite side of the pt, moved across the pt in a straight line collecting several transmission measurements, called projections. -the tube rotated one degree and repeated the data collection process until 180 degree of transmission data was acquired.

Pencil Beam

There are three major types of beam geometry: _____, _____ and _____.

Pencil beam, fan beam and cone beam

The spacing of the bands of data is referred to as ______.

Pitch

_____ collimation are located directly below the tube collimators ensures that the beam width is constant as it travels toward the pt.

Postpatient

______ collimation are located just beyond the x-ray tube and determine the scan volume for each tube rotation for a particular scanning procedure.

Prepatient

Two types of collimators are used in MDCT scanning: _____ and _____

Prepatient, postpatient

During ______, each voxel, or individual image element, is assigned a specific number to represent its brightness. _______ helps the computer to display the image data appropriately, depending on what tissue type the individual viewing the image is examining.

Quantization

After the signal from the detectors has undergone analog-to-digital conversion, it is read as _____ data into the computer, where it is reconstructed into a cross-sectional image.

Raw (or unprocessed data)

_______ plane divides the body into a right side and left side.

Sagittal Plane

The image data can be displayed in a _____, ______ or ______ plane depending on the user preferrence.

Sagittal, transverse or coronal plane

______ ______ components include: -high quality flat panel display monitor, keyboard and mouse and central processing unit.

Scanning Console

The _____ generation scanners: -used much larger x-ray beam and larger number of detectors -Used "Fan beam" x-ray beam -completed a scan with far less indexing motion than first generation.

Second Generation

The ______ generation scanners: -Spiral-helical scanners -can aquire data from between 16 and 320 sections per rotation -reduced scan time -multiple rows of detectors -referred to as a multisectional, multidetector or multiple detector array scanner

Seventh Generation

______ ______ _____ _____brought together the pieces to create the first workable CT unit.

Sir Godfrey Newbold Hounsfield

The ______ generation scanners: (also known as helical) -the ability of the x-ray tube and detectors to continuously rotate around the pt while the patient and table move through the gantry -aquire data continuously during the scan, so an entire volume of tissue can be imaged during one breath hold. -Often referred to as spiral or helical scanners -Slip rings help maintain a constant connection between x-ray tube and its electrical source

Sixth Generation

The ______ is usually made of carbon fiber composites because those materials have low absorption and excellent vibration dampening capabilities.

Table

The ______ generation scanners: -Fan beam is much larger -have a curved array of detectors that gather image data. -Operates continously, without stopping to translate. -both x-ray tube and row of detectors rotate so that an entire 360 degree arc of image data can be collected.

Third Generation

The process of using motion to blur certain portions of the patients anatomy in order to demonstrate a particular area of interest is called the ______ principle

Tomographic

______ plane divides the body into a superior and inferior portion.

Transverse Plane

A CT scanner images a _______ section of anatomy as it scans a patient's body. The images are presented like a loaf of bread....

Transverse section

_____ _____ are usually defined by the maximum load at which the table can be moved accurately, not the weight limit at which the table will break.

Weight limits

A pitch of 1 results in _______ bands.

adjacent bands

A pitch of less than 1 implies the bands ______.

bands overlap

A pitch of greater than 1 results in _____.

gaps between the bands