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    Outline

    - New standards on Computed Radiography and radiography with DigitalDetector Arrays have been developed and partly published.

    - Some key requirements are discussed for the major standard organizations:

    ASME, ASTM, EN ISO.

    - The proof of minimum image quality by image quality indicators in radiographyis the basis for technical safet and contractual a reements in industr and willnot be changed.

    - The essential parameters for optimization and prediction of step hole visibility.

    - Three essential parameters for image quality in Digital Radiology (DR) are:

    - Signal to noise ratio (SNR)- pec c con ras eff- Basic spatial resolution (SRb).

    - Discussion of the requirements for detector qualification and selection.- Information on the implementation of the essential parameter concept in the new

    standard practice EN ISO/DIS 17636-2: NDT of welds RT Part 2: X- andgamma ray techniques with digital detectorsand in the ASTM E 2033 (draft: CR

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    practice) and E 2597 (DDA qualification) and E 2698 (DDA practice).

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    Overview of Standards on Digital Industrial Radiology

    EN 14096, ISO 14096 Film Digitization

    EN 14784 CR 2005 Part 1: Classification of S stems, Part 2: General

    Goes to ISO, revision required principles, becomes ISO 16371

    ISO 10893-7 (2010) Steel tubes NDT of welds with DDA and (CR)New ISO/DIS 17636-2 NDT of welds: CR and DDA to substitute EN 1435

    New ISO draft: corrosion and

    wall thickness measurement

    Practice with film, CR and DDA for double wall and

    tan ential techni ue

    ASME (BPVC, S.V, XI) CR Radiography (CR) with Phosphor Imaging Plates

    ASTM CR (2005) Classification (E 2446-05), Long term stability (E2445-Revision required 05), Guide (E 2007-10), Practice (E 2033-06)

    ASTM DDA (2010) Characterization (E 2597-07), Guide (E 2736-10),Practice E 2698-10 Lon Term Stabilit E 2737-10

    ASTM DICONDE (2010)

    (data format)

    Standard Practice for Digital Imaging and Communication

    Non-destructive Evaluation (DICONDE)

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    - , - , - , - , -

    ASTM E 2422-05, E 2660-

    10, E 2669-10Digital reference image catalogues,

    light alloy, titanium and steel castings

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    Basic Requirements for Film Radiography

    in all National and International Standards

    All film based standards require: Minimum optical Density (e.g. D > 2.0)

    ax mum m sys em c ass e.g. Maximum unshar ness < 0.1 mm FFD/FOD

    Minimum IQI perception (e.g. > W14, < H3)What are the correct requirements for film replacement by

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    ASME BPVC Section V (NDE)

    Mandatory Appendices

    I In-Motion Radiography

    II Real-Time Radioscopic Examination

    III Digital Image Acquisition, Display, and Storage for Radiography and Radioscopy

    IV Interpretation, Evaluation, and Disposition of Radiographic and Radioscopic Examination

    Test Results Produced by the Digital Image Acquisition and Display ProcessV Glossary of Terms for Radiographic Examination

    VI Digital Image Acquisition, Display, Interpretation, and Storage of Radiographs forNuclear Applications

    VII Radiographic Examination of Metallic Castings

    VIII Radio ra h Usin Phos hor Ima in Plate

    IX Application of Digital Radiography

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    ASME Section V Article 2 Radiographic Examination 2007

    W 13

    W 12

    W 11

    W 10

    W 09

    W 08W 07

    W 06

    W 05

    W 04

    W 02

    W 01

    CEN wires

    ASME requires basically the

    April 2012,

    Ewert et al. Standards in Digital Radiologyminimum IQI-Visibility for digital radiography only!

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    Basic Requirements for IQI Visibility of

    y = 17,687x-0,483 Ste Holes ISO/DIS 17636-2 EN 1435y = 15,711x-0,48

    y = 11,112x-0,505

    n[%

    ]Plate Holes,ASMEBPVC SC V Ar. 2

    Plate Holes,ASTME 1742, E 2104,

    3,00R

    esoluti

    hicknes

    , . ,

    EN 1435-class A andISO 17636-class A are

    about equivalent

    y = 5,851x-0,402

    y = 4,2561x-0,406

    Wall

    ASTM E1742, E 2104,

    EN 1435-class B and

    -

    0,30

    1,00 10,00 100,00

    res 7 - , 5

    about equivalent below

    t=12 mm (1/2)

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    Influence of Image Noise on

    etail Visibilityetail Visibility

    Intensity

    Contrast

    Signal Intensity

    Contrast

    Signal

    Length

    Length

    Notch visible!

    Contrast/Noise is high

    Notch not visible!

    Contrast/Noise is low

    April 2012,

    Ewert et al. Standards in Digital RadiologySignal/Noise is high Signal/Noise is low

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    Effect of System Class in Film Radiography

    Lost of information / perception of flaws

    D

    Fine grained film,

    slow Imaging plates

    Coarse grained film,

    fast imaging plates

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    Film system C1 C5 C6

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    Noise Sources in Radiographic Images

    Typical noise sources in digital radiography:

    1. EXPOSURE CONDITIONS: Photon noise, depending on

    exposure dose (e.g. mAs or GBqmin). This is the main factor!SNR increases with higher exposure dose.

    2. Limitation for the maximum achievable SNR:

    1. DETECTOR: Structural noise of DDAs and Imaging Platesalso called fixed pattern noise (due to variations in pixel topixel response and inhomogeneities in the phosphor layer).

    2. OBJECT:

    1. Crystalline structure of material (e.g. nickel based steel,mottling)

    2. Surface roughness of test object

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    Noise in Dependence on Exposure Time

    CNR and SNR increase with increasing exposure time due to

    Normalized at constant contrast

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    improved photon statistics

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    Human Observer Model: Perception Threshold PT

    a o you seeNoise = 1000

    =

    or magnification technique

    CNR = 2.5

    .visible than small ones at

    same Contrast-to-NoiseA

    CNR = 1.25 Each row has indications

    =

    CNR = 0.625

    ep

    Each column has holes

    with same diameterFlat bottom holes of different de th and diameter2T = 0.5 mm / 0.02SRb image = 50 mCalculated CNRmin = 1

    b

    depthlateral

    constSR

    PT -

    Alateral area of just visible indication

    Cdepth mean contrast of just visible indication

    - noise of image (N)

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    SRb basic spatial resolution (effective pixel size)Rose approach, 1946

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    Image Quality in Digital Radiology- -

    The 3 essential parameters:

    gna o no se ra o Specific contrast (eff)

    ratio (CNR)

    Basic spatial resolution (SRb)

    noise ratio (SNRN)

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    Essential Parameters for Calculation of JustVisible IQI 1 T Hole Diameter

    The essential parameters are: eff, SNR and SRb?

    New Formula

    Depends on Hardware: effective pixel sizeMagnification

    Focal spot size, source size

    SRPTd

    image

    b

    SNR - Signal to noise ratio

    eff specific contrast,

    SNReff

    SRb effective pixel size in the image,basic spatial resolution of image

    a er a ,keV, Source typeScattered radiation

    Exposure timeTube current, Activity

    Detector efficiency

    -

    ource- o- e ec or s ance

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    ,

    viewing conditions and operator14

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    Comparison of Calculated and Measured Image Quality

    0,17Berechnete und gemessene Bildqualitt

    d = PT*/square_root((kV,w) SNR(GV))

    Calculated and Measured Image Quality

    Dependence on tube kV

    0,15

    s(m

    m)

    Calculated IQI visibility from measured CNR

    Diameter of Visible wires

    Diameter of visible wires (digital fil ter)

    W 14d

    ntinmm

    0,13

    barenDrahte

    Diameter of Visible hole normalised by 2.5

    Diameter of Visible hole normalised by 2.5 (digital filter)W 15

    IQIeleme b .

    0,09

    0,11

    serdessicht

    W 16Calculated just visible wire

    ustvisibl

    0,07Durchmes

    W 17

    Just visible wire diameter and

    of the just visible1T-hole,

    ame er

    terofthej

    132 mAmin

    1 m SDD

    0,05

    60 80 100 120 140 160 180 200 220 240kV

    ,

    (high pass filter)Diam

    19 mm FeUR 1, DynamIx HR

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    Qualification of Imaging Plate Systems by the Visibility ofIQIs and/or EPS calculation from eff, SNR and SRb10

    25)

    EPS Procedure is proposed for CR qualificationin the new ASTM E 2033 draft and the Draft on Practice for the Use of Computed Radiology for Aerospace Casting Inspections (USA: MAI group)6,

    E747,

    - The EPS (equivalent penetrameter sensitivity) measurement is based on E 746

    - A smooth inch (19 mm) steel plate with a set of plate holes is radiographed at 200kV in 1 m distanceASTME7

    - Other IQIs are on the plate

    to increase the information

    on image response.sitivity(se

    The exposure is performedwith different mAs settings

    metersen

    ,

    see next page

    Verification of equation:

    len

    tpenetr

    SNR

    SRPTd

    eff

    mage

    bvisible

    E 746S=equiva

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    eff for 200 kV and 19 mm Fe is about 0,05 mm-1

    16

    ew ormu aE

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    Example: EPS test with DRR HD CR scanner at20 m pixel size

    Do you see the holes?

    (19 mm) steel plate, 200 kV

    CNR 0.81 mm steel step formeasuremen o eff

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    Visibility of EPS holes (E 746)

    Do you see the holes?

    CNR 0.8

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    New Formula for Conversion of SNRN Measurements toEPS Values and Working Range for CR (ASTM Draft E 2033)

    PT is about 2100 for visibility of the 2 T hole of IQIs corr. to ASTM E 1025

    EPS by ASTM E 746 with 200 kV, t = 19 mm Fe plate and eff = 0.05 mm-1

    Plateau area defines theSRPT

    EPSimage

    b

    '

    PT EPSmax

    wor ng range etestp ate

    ASTM

    EPS = 15%Level I

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    EPS= equivalent penetrameter sensitivity (see ASTM E 746, E 747, E 1025)

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    Requirements for Digital Detector Arrays

    Exceeding Film Quality withHigh Contrast Sensitivity Technique

    HCS-RT

    DDA

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    Qualification of Digital Detector Arrays- -

    6.2.1 Definition and Test of Bad Pixels:

    A bad pixel can be corrected if it has at least 5 good neighbors. . .

    6.2.1.2 Over Responding Pixel

    6.2.1.3 Under Responding Pixel

    6.2.1.4 Noisy Pixel

    6.2.1.5 Non-Uniform Pixel

    6.2.1.6 Persistence/Lag Pixel

    6.2.1.7 Bad Neighborhood Pixel

    6.2.2 Types or Groups of Bad Pixels:

    . . .

    6.2.2.2 Cluster of Bad Pixels

    6.2.2.3 A cluster without an CKP is wellcorrectable.

    6.2.2.4 A cluster with CKP is labeled a

    relevant cluster.

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    . . .

    special irrelevant cluster.

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    Qualification of Digital Detector Arrays

    DDAs are qualified by different tests of ASTM E 2597.Five relevant parameters shall be provided: Basic spatial resolution (SRb)

    Specific Material Thickness Range

    Efficiency

    Image lag Contrast sensitivity

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    Measurement of Contrast to Noise Ratio in DDA Practice

    CNR shall be measured in theNoise

    y

    4T hole or proo o image quality.

    A minimum CNR of 2.5 is

    required by ASTM E 2698. This value needs to be revised!

    = .C = I = 473

    Noise = 71

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    SNR = 155

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    Verification of CNRmin for ASTM Standard Practice

    ASTM Draft, Practice for the Use of Digital Detector Arrays and ComputedRadiology for Aerospace Casting Inspections and E 2698 Standard

    for digital images with DDAs in the 2T IQI hole:

    But CNRmin for all digital images can be described more accurate by the

    .min

    equation:image

    SR10

    holeIQIdiameter

    min

    The ASTM E 2698 value (CNR = 2.5) is optimized for testing of thin objects with

    thickness < and typical DDAs in the range of 0.1 mm < SRb < 130 m.

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    BAM 5, 8mm steel

    FujiFilm IX25SNRN ~ 265

    DDA Technology

    quality than fi lm with a

    s ecial calibrationBest (slowest) NDT film

    procedure!

    Images high pass

    filtered for better

    PerkinElmer 1620

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    SNRN ~ 1500Magn. = 3.5

    DDA exposure 25

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    Requirements of ISO/DIS 17636-2

    NDT of welds RT Part 2: X- and gamma ray

    techni ues with di ital detectors

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    Computed Radiography (CR) with storage

    phosphor imaging plates

    CR DDA

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    S

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    New Standard Proposal

    -Radiographic testing of welds with digital detectors.

    I. Minimum score for wire type or step-hole type Image Quality

    Indicators (IQIs) in function of test technique (similar to ASME)

    II. Maximum image unsharpness requirements (SRb = Basic Spatial

    Resolution, determined using a duplex wire gauge)

    III. Choice of tube voltage or gamma source in function of objectcomposition, penetrated thickness and detector

    . - - N

    Determine SNR (Signal-to-Noise Ratio) and SRb

    Anti-scatter filter t e & thickness Source-to-Detector Distance requirements

    New testing geometries

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    V. New compensation principles

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    Minimum IQI score for wire type or step-hole

    IQI scores taken

    from EN1435

    Potential Issues

    Same re uirements for

    wire type and step hole

    IQIs as in EN 1435 and

    ISO 19232-3

    New exceptions for

    isotopes for doublewall inspections

    1 wire or step-holevalue less for Ir192

    5 mm < w 12 mm:-

    value less for Se75

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    New European standard proposal

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    New European standard proposal

    ISO 17636-2

    n mum N an an -sca er er

    Concept SNRN was taken

    from EN14784-1. Minimum values are

    tabulated in function of

    radiation ener and

    object thickness, similar totable 2 of EN14784-2.

    reduced to maximum

    values only except for

    g energy.

    April 2012,

    Ewert et al. Standards in Digital RadiologyHigher SNRN requirements than in EN14784-2

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    New European standard proposal ISO 17636-2Maximum detector or image unsharpness (SRb)

    0.030

    0.030

    .

    0.040

    0.063

    April 2012,

    Ewert et al. Standards in Digital RadiologySRb concept taken from EN14784-1IQI scores relaxed compared with EN14784-2

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    Measurement of Interpolated Basic Spatial Resolution

    Duplex wire IQIEN 462-5

    -

    ASTM E 2002

    Determination of the basicspatial resolution in each

    production radiograph is not

    required but recommended.

    N con ro s su c en y

    the image quality at a givenpixel size.

    I,90k

    V,

    lfocus

    udetectorshall be controlled

    by reference exposures with

    the duplex wire IQI. x

    Wire

    I

    D,

    sma

    l

    The interpolated basic

    spatial resolution is

    1

    Dup

    l

    1m

    S

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    totalb 2

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    Compensation Principle (II)

    Compensation of high detector unsharpness by increased SNR

    Unsharp digital systems may be applied for NDT if they enable

    to compensate the missing sharpness by increased SNR.

    at means, ac eves a g ta system not t e requ re

    visibility of the separated duplex wires, it can be used for

    NDT, if one or two single wires more than required (see

    tables B.1 B.12 of ISO/DIS 17636-2) can be seen clearly in

    the digital image for one or two missing duplex wire pairs.

    Com ensation of 3 wires vs. wire airs re uires a reement

    of contracting parties.

    Compensation principle (II):

    High detector unsharpness can be compensated by

    increased SNR 34

    April 2012,

    Ewert et al. Standards in Digital RadiologyCompensation Principle II

    Compensation for Higher Unsharpness by Increased SNR

    New European standard proposal

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    New European standard proposal

    ISO/DIS 17636-2

    Example : new compensation principle II

    Compensate missing spatial resolution by increased singlewire sensitivity:

    A lower spatial resolution i.e. a lower double wire score (D)

    . .

    higher single wire score (W). Max. two (or three) single/double wire scores may be exchanged.

    Required:Not OK: OK OK

    D12

    W14D13

    W13

    D11

    W15D10

    W16

    D9

    W17

    Duplex wire score

    Single wire score

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    C l i

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    Conclusions

    New standards were developer for digital industrial radiography for detector qualification, quality

    assurance and standard practices.

    Image quality depends on the essential parameters: (specific) contrast eff, achieved SNR and

    b.

    For practical application further parameters have been included for DDAs, as contrast sensitivity,

    efficiency, image lag and material thickness range.

    max

    value which is limited by the design of the imaging plate (fixed pattern noise) or DDA calibration.

    The operator increases the contrast sensitivity by the exposure time and tube current up to a

    certain EPS lateau, which defines the recommended re value workin ran e for CR ASTM E

    2033, new draft).

    DDAs achieve a significant better contrast sensitivity with correct detector calibration than film

    radiography. The prove of image quality requires CNR measurements (ASTM practice E 2798).

    New standard practices have been developed for CR and Radiography with DDAs. Basic

    requirements are defined by EPS, SNR, SRb and CNR depending on the technology.

    ISO/DIS 17636-2 defines additionally compensation principles for the standard practice and

    .

    3 compensation principles (3rd one for DDAs only) are described in the standard.

    ISO/DIS 17636-2 defines minimum requirements for detector SRb, depending on the material

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    .

    36

    www.filmfree.eu.comAcknowledgement

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    g

    European Projects:

    with 33 Partners, 11 countries2005 2009

    HEDRad

    2009 2011

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    End

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    uwe.ewer am. e

    38