ISO 17636-2:2022 溶接部の非破壊検査 — 放射線検査 — Part 2: デジタル検出器を使用した X 線およびガンマ線技術 | ページ 5

3.1

computed radiography

cr

complete system comprising a storage phosphor imaging plate (IP) (3.2) and a corresponding read-out unit (scanner or reader), which converts the information from the IP into a digital image

3.2

storage phosphor imaging plate

IP

photostimulable luminescent material capable of storing a latent radiographic image of a material being tested and which, upon stimulation by a source of red light of appropriate wavelength, generates luminescence proportional to radiation absorbed

Note 1 to entry: When performing computed radiography (3.1) , an IP is used in lieu of a film. When establishing techniques related to source size (3.20) or focal geometries, the IP is referred to as a detector, i.e. source-to-detector distance (3.21) .

3.3

digital detector array

DDA

electronic device converting ionizing or penetrating radiation into a discrete array of analogue signals which are subsequently digitized and transferred to a computer for display as a digital image corresponding to the radiologic energy pattern imparted upon the input region of the device

3.4

structure noise

<imaging plate> local sensitivity variations due to inhomogeneities in the sensitive layer (structure, graininess) and surface of an imaging plate

Note 1 to entry: After scanning of the exposed imaging plate, the inhomogeneities appear as overlaid fixed pattern noise in the digital image.

Note 2 to entry: This noise limits the maximum achievable image quality of digital CR images and can be compared with the graininess in film images.

3.5

structure noise

<digital detector array> local sensitivity variations due to different properties of detector elements (pixels)

Note 1 to entry: After read-out of the exposed uncorrected digital detector array (DDA) (3.3) image, the inhomogeneities of the DDA appear as overlaid fixed pattern noise in the digital image. Therefore, all DDAs require, after read-out, a software-based image correction (software and guidelines are provided by the manufacturer). A suitable correction procedure reduces the structure noise.

Note 2 to entry: The image correction is also called “calibration” in other documents.

3.6

grey value

gv

numeric value of a pixel in a digital image

Note 1 to entry: This is typically interchangeable with the terms “pixel value”, “detector response”, “analogue-to-digital unit” and “detector signal”.

Note 2 to entry: For further information, see Annex E.

3.7

linearized grey value

numeric value of a pixel which is directly proportional to the detector exposure dose, having a value of zero if the detector was not exposed

Note 1 to entry: This is typically interchangeable with the terms “linearized pixel value” and “linearized detector signal”.

3.8

basic spatial resolution of a digital detector

sr_b^detector

half of the measured detector unsharpness in a digital image, which corresponds to the effective pixel size and indicates the smallest geometrical detail which can be resolved with a digital detector at magnification equal to one

Note 1 to entry: For this measurement, the duplex wire IQI is placed directly on the digital detector array (3.3) or imaging plate.

Note 2 to entry: The measurement of unsharpness is described in ISO 19232-5. See also ASTM E1000 and ASTM E2736.

3.9

basic spatial resolution of a digital image

sr_b^image

half of the measured image unsharpness in a digital image, which corresponds to the effective pixel size and indicates the smallest geometrical detail which can be resolved in a digital image

Note 1 to entry: For this measurement, the duplex wire IQI is placed directly on the object (source side).

Note 2 to entry: The measurement of unsharpness is described in ISO 19232-5. See also ASTM E1000 and ASTM E2736.

3.10

signal-to-noise ratio

SNR

ratio of mean value of the linearized grey values (3.7) to the standard deviation of the linearized grey values (noise) in a given region of interest (3.25) in a digital image

3.11

normalized signal-to-noise ratio

SNR_N

Note 1 to entry: If the duplex wire IQI is positioned directly on the detector without a test object, sr_b^image is equal to the measured sr_b^detector, which can be used instead of sr_b^image.

3.12

contrast-to-noise ratio

CNR

ratio of the difference of the mean signal levels between two image areas to the averaged standard deviation of the signal levels

Note 1 to entry: Signal levels are measured in grey values (3.6) or linearized grey values (3.7) .

Note 2 to entry: The contrast-to-noise ratio describes a component of image quality and depends approximately on the product of radiographic attenuation coefficient and SNR. In addition to adequate CNR, it is also necessary for a digital radiograph to possess adequate unsharpness or basic spatial resolution to resolve desired features of interest.

3.13

normalized contrast-to-noise ratio

CNR_N

3.14

aliasing

artefacts that appear in an image when the spatial frequency of the input is higher than the output is capable of reproducing

Note 1 to entry: Aliasing often appears as jagged or stepped sections in a line or as moiré patterns.

3.15

cluster kernel pixel

CKP

bad pixel (3.29) which does not have five or more good neighbourhood pixels

Note 1 to entry: See ASTM E2597 for details of bad pixels and CKP.

3.16

nominal thickness

t

thickness of the parent material only where manufacturing tolerances do not have to be considered

3.17

penetration thickness change

Δt

change of penetrated thickness (3.18) relative to the nominal thickness (3.16) due to beam angle

3.18

penetrated thickness

w

thickness of material in the direction of the radiation beam, calculated on the basis of the nominal thicknesses (3.16) of all penetrated walls

3.19

object-to-detector distance

b

largest (maximum) distance between the radiation side of the radiographed part of the test object and the sensitive layer of the detector, measured along the central axis of the radiation beam

Note 1 to entry: The abbreviated term ODD is used in other documents.

3.20

source size

d

size of the radiation source or focal spot size

Note 1 to entry: See EN 12543 or EN 12679.

3.21

source-to-detector distance

SDD

distance between the source of radiation and the detector, measured in the direction of the beam

Note 1 to entry:SDD = f + b

3.22

source-to-object distance

f

distance between the source of radiation and the source side of the test object, measured along the central axis of the radiation beam

Note 1 to entry: The abbreviated term SOD is used in other documents.

3.23

external diameter

D_e

nominal value of the external diameter of the pipe

3.24

geometric magnification

v

ratio of source-to-detector distance (3.21) to source-to-object distance (3.22)

3.25

region of interest

RoI

defined group of pixels from which measurements or statistics, or both, can be derived

3.26

weld area to evaluate

WAE

area to be evaluated on the radiograph, which contains the weld and the heat-affected zone (3.30) on both sides

3.27

area of interest

AoI

minimum area which should be evaluated on the radiograph and which contains the weld, the heat-affected zone (3.30) on both sides and all lead letters, markers and image quality indicators (IQIs)

3.28

raw image

image acquired with digital detector arrays (3.3) or computed radiography (3.1) systems after image correction, if a correction has been performed

3.29

bad pixel

underperforming detector element (pixel) of a digital detector array (3.3)

Note 1 to entry: Bad pixels are described in ASTM E2597.

3.30

heat affected zone

HAZ

area beside the weld influenced by the heating and cooling process of the welding, which is considered as the two areas beside the weld, each with the same width as the weld cap but at least 10 mm width to be considered for evaluation