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ASTM E 1672 Document Information:
Title
Standard Guide for Computed Tomography (CT) System Selection
ASTM International
Publication Date:
Dec 1, 2006
Scope:
This guide covers guidelines for translating application
requirements into computed tomography (CT) system
requirements/specifications and establishes a common terminology to
guide both purchaser and supplier in the CT system selection
process. This guide is applicable to the purchaser of both CT
systems and scan services. Computed tomography systems are complex
instruments, consisting of many components that must correctly
interact in order to yield images that repeatedly reproduce
satisfactory examination results. Computed tomography system
purchasers are generally concerned with application requirements.
Computed tomography system suppliers are generally concerned with
the system component selection to meet the purchaser's performance
requirements. This guide is not intended to be limiting or
restrictive, but rather to address the relationships between
application requirements and performance specifications that must
be understood and considered for proper CT system selection.
Computed tomography (CT) may be used for new applications or in
place of film radiography, provided that the capability to disclose
physical features or indications that form the acceptance/rejection
criteria is fully documented and available for review.
Computed tomography (CT) systems use a set of transmission
measurements made along a set of paths projected through the object
from many different directions. Each of the transmission
measurements within these views is digitized and stored in a
computer, where they are subsequently conditioned (for example,
normalized and corrected) and reconstructed by one of a variety of
techniques. An in-depth treatment of CT principles is given in
Guide E 1441.
Computed tomography (CT), as with conventional radiography and
radioscopic examinations, is broadly applicable to any material or
object through which a beam of penetrating radiation may be passed
and detected, including metals, plastics, ceramics,
metallic/nonmetallic composite material and assemblies. The
principal advantage of CT is that it provides densitometric (that
is, radiological density and geometry) images of thin cross
sections through an object. Because of the absence of structural
superposition, images are much easier to interpret than
conventional radiological images. The new purchaser can quickly
learn to read CT data because images correspond more closely to the
way the human mind visualizes 3-D structures than conventional
projection radiology. Further, because CT images are digital, the
images may be enhanced, analyzed, compressed, archived, input as
data into performance calculations, compared with digital data from
other nondestructive evaluation modalities, or transmitted to other
locations for remote viewing. While many of the details are generic
in nature, this guide implicitly assumes the use of penetrating
radiation, specifically X rays and gamma rays.
This standard does not purport to address all of the safety
concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and
health practices and determine the applicability of regulatory
limitations prior to use.
Keywords:
- artifacts
- computed tomography (CT)
- contrast discrimination
- detectability
- dynamic range imaging
- nondestructive evaluation
- spatial resolution
- scan services
- throughput
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