Card Set Information
Intro to CT
The process of creating a cross-sectional tomographic plane of any part of the body:
What measures the radiation exiting the patient and feeds back the primary data to the host computer?
A detector assembly
In the early 70's, CT scanning was only used clinically for imaging the:
The first CT scanners were capable of producing only ____ images.
The differentiation of densities is referred to as:
The improved contrast resolution with CT when compared to conventional is due to a reduction in the amount of:
When and by whom was CT first demonstrated?
1970, Godfery Hounsfield
The early CT scanners were categorized by:
The first generation scanners worked by the process of:
First generation scanners produced a ____ beam.
First generation scan time was :
The first generation scanner had a linear tube movement known as ____ followed by a rotation of ___.
translation, 1 degree
Why was early CT limited almost exclusively to neurologic examinations?
Slow scanning and reconstruction time
Second generation scanners emitted a ____ beam measured by ____ detectors.
fan shaped, 30
Second generation scanners were _____/______ movement, but the rotation was ____ degrees between each translation.
Scan time of second generation scanners was ____ for a single slice.
Third generation scanners introduced a _____/_____ movement with ____ detectors.
Third generation scanners reduced scan time to ____ per slice.
Fourth generation scanners introduced _____ movement. The tube moves ____ while the detectors are ____.
rotate-only, around the patient, in fixed positions
In contemporary CT scanners, both ___ and ___ generation designs are incorporated.
3rd and 4th
A relative comparison of x-ray attenuation of a voxel of tissue to an equal volume of water:
CT Number, or Housefield unit
Tissues that are denser than water are given ____ CT numbers whereas tissues with less density than water are given ____ CT numbers.
The scale of CT numbers ranges from _____ for air and _____ for dense bone.
Three main components of the CT scanner:
Computer, Table, and Gantry
The computer system used in CT has 4 basic functions:
control of data acquisition, image reconstruction, storage of image data, and image display
CT studies are removed form the limited memory of the host computer and stored independently, a process called:
The gantry is a circular device that houses the:
x-ray tube, data acquisition system (DAS), and the detector array
The gantry can be tilted forward or backward up to ____
The opening within the center of the gantry is termed the ____ and measures about ____.
aperture, 28 inches wide
CT tables are made of ____ or ____ and have weight limits of ____-_____.
low-density carbon composite or wood; 300-600 lbs
The special device used for head CT examinations is called:
The postprocessing technique which allows image reconstruction in a variety of planes without additional radiation to the patient is:
Multiplanar Reconstruction (MPR)
Original CT's were used to diagnose:
Most commonly requested CT procedures:
head, chest and abdomen
Contrast media for CT is of ____ concentration.
Four main factors contributing to image quality:
spatial resolution, contrast resolution, noise and artifacts
The amount of blurring in an image:
The latest technology of detector arrays has ___ rows of elements.
Muli-slice helical CT systems are referred to as ____ CT systems because covering entire body sections is easily accomplished in a single breath-hold.
The bones of the skull are categorized into ___ facial bones and ____ cranial bones.
The brain is surrounded by three layers of protective membranes called the:
From internal to external, the meninges are:
pia matter, arachnoid matter, and dura matter
The two hemispheres of the brain are connected by the:
A unique arterial anastomosis exits in the brain to protect it from sudden loss of blood supply; it is called:
the Circle of Willis
Venous drainage in the brain is accomplished by two systems:
cerebral veins and dural venous sinuses
Degree of arc angulation described by the movement of the x-ray tube and cassette during a tomographic motion
tomographic fulcrum remains at a fixed height
plane of tissue that is in focus on a tomogram
point of axis of rotation for a tomographic motion
Basic tomographic movement that occurs when x-ray tube and cassette movement occurs with the longitudinal axis of the tomographic table
linear tomographic motion
Tomographic principle in which the fulcrum, or axis of rotation, is raised or lowered to alter the level of the focal plane; the tabletop height remains constant.
Storage of CT images on long-term storage device such as cassette tape, magnetic tape, or optical disk.
Same as transverse:
Preset amount of contrast injected rapidly per IV administration to visualize high-flow vascular structures
Area of anatomy displayed by the CRT
Field of View
Determines field of view; also referred to as zoom or focal plane
Cancer of plasma cells in bone marrow:
Acquired language disorder in which there is impairment of any language modality; including producing or comprehending spoken or written language.
Muscle weakness on one side of the body:
Why is a dry head done before administering contrast?
To check for conditions that may be hidden by contras; prior surgeries/calcifications etc.
Body section radiography:
Basic positions for tomographic examinations:
AP and Lateral
In tomographic examinations, structures are oriented either:
parallel or perpendicular to the tomographic plane