2 International Scanner Contest...

ASSESSMENT OF TECHNICAL PARAMETERS A. Alekseychuk1, N. Zerbe2, Y. Yagi3 1Computer Vision and Remote Sensing, TU Berlin, Berlin, Germany 2Institute of Pathology, Charité – Universitätsmedizin Berlin, Berlin, Germany 3Massachusetts General Hospital, Boston, United States

technology meets pathology 2nd International Scanner Contest

technology meets pathology

2nd International Scanner Contest

 „Non-medical” parameters evaluated

 Precision: technical image quality   Colour fidelity & resolution   Geometrical distortions and effective pixel size

 Green IT: environmental/ergonomic properties   Noise emission   Power consumption

Overview

Giovedì, 14 giugno 2012 2



  Motivation:   Large range of illuminators

-  Incandescent (halogen) bulbs: 15-150 W

-  High intensity gas discharge lamps (xenon, mercury, tin-halide): 75-200 W

-  LED: 3-5 W typical   Mechanics and electronics

-  slide advance & autoloader -  CCD camera (10-15W non-cooled)

  Measuring: -  in-socket device -  ±1%, ±1W typical

Power consumption


5 W

250 W



  40x scan (“Quality”) of about 1 cm² specimen

  Scanner only (without computer and monitor)

Power consumption measurements


  Results:   Power range: 19 W – 360 W   Energy per scan: 6 Wh – 83 Wh   Highest Wattage – not highest consumption



“Acoustic Camera” (gfai tech GmbH, www.acoustic-

camera.com)

  phased array of 48 microphones

  fine spectral and time resolution (down to 10 µs)

  distribution of sound emission → “sound image”

  simple video camera for overlay

Noise emission measurements




  Measured during “Quality” scan

  Absolute measurements dif ficult (background noise)

Noise emission measurements




  Aims of investigation:   determination of true effective pixel

size   image distortions   no stitching assessment

  Main test specimen:   overall size: 1” x 3” (25mm x 75mm)   image area: 20mm x 50mm   clear aperture: 8.5 µm²   opaque lines: 1.5 µm²   pitch: 10 µm

Geometrical precision




Geometrical precision

 Other test specimens



  Human: trichromatic vision

  Cones spectral sensitivity   nor RGB neither XYZ, etc.   complex mechanism

  Digital sensing accuracy   spectral properties of sensor   encoding and calibration

  Sufficient illuminator   CRI / CIE metamerism index

  Danger: slight shades of colour not distinguishable

Colour and its measurement




  Tungsten lamps (halogen): smooth spectrum, 3200K typical

  Arc lamps (xenon): flat continuous spectrum, 6500K (daylight)

  Fluorescent lamps (LID): only a few spectral l ines (usually) → problems

  LED:   fundamentally monochromatic

(single mode)   with luminophor → wider

Spectra of light sources




  Aims of assessment : -  colour fidelity of devices – absolute accuracy of colour

reproduction -  colour resolution – detectability of subtle differences

  IT8.7/1 colour target -  264 colour & 24 grey value fields -  known absorption spectra -  known colourimetric coordinates

  Testing method 1.  perform low-resolution scan 2.  average inside middle 50% of each field

Colour accuracy test method




3.  Chromatic adaptation (property of human vision) → colour temperature correction after Von Kries

4.  Colour dif ference calculation to CIEDE2000 definition (resolves CIE94 dE perceptual uniformity issue)



Planckian locus and constant CCT lines

contours of just- noticeable- differences (JND)




  Fidelity test: average dE over 144 fields

dEavg=n dE(c*mes, cref) /144

→ the lower the better

  Colour resolution ability: minimum over step differences on step wedges

dEstep= min dE(cmes(i), cmes(i+1)),

i ∈ [B,J]

→ the higher the better colour step wedges

mix-colours matrix for fidelity test



  1st time technical domain   5 of 6 manufactures participated   Performed a few simple yet useful tests   First time metrological assessment of colour fidelity of

histological scanners → technical limits of visibility of structures

  Outlook:   more quantitative methods   more metrology in this domain (60dBA vs. 65dBA → 60 ±6dBA vs.

….)   IT8 → histological dies, matrix of application-specific colours   advanced geometry (e.g. evaluation of quality of stitching)

Conclusions




Thank you for your attention!





2 International Scanner Contest...

Documents

Transcript of 2 International Scanner Contest...