디지털 래디오그라피 디텍터의 성능 -modulation transfer function- 6 nov 2014 seungman...
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Radiation Imaging Laboratory, Pusan National University Seungman Yun 6 Nov 2014, 의공학개론 MTF, NPS, DQE Performance of X-ray Imaging Detectors 3 DQE MTF SNR NPS Resolution Contrast Noise Degrading “contrast” Degrading “detail” Adding “noise” Ideal image X-ray imaging system transfers by… MTF: modulation-transfer function NPS: noise-power spectrum SNR: signal-to-noise ratio DQE: detective quantum efficiencyTRANSCRIPT
디지털 래디오그라피 디텍터의 성능-Modulation Transfer Function-
6 Nov 2014
Seungman YunRadiation Imaging Laboratory,
School of Mechanical Engineering,Pusan National University, South Korea
Radiation Imaging Laboratory, Pusan National UniversitySeungman Yun {[email protected]}
6 Nov 2014, 의공학개론 MTF, NPS, DQE
자료 다운로드http://bml.pusan.ac.krLecture Introduction to Medical Engineering
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Radiation Imaging Laboratory, Pusan National UniversitySeungman Yun {[email protected]}
6 Nov 2014, 의공학개론 MTF, NPS, DQE
Performance of X-ray Imaging Detectors
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DQE
MTF
SNR
NPS
Resolution
Contrast
Noise
Degrading “con-trast”
Degrading “de-tail”
Adding “noise”
Ideal image
X-ray imaging sys-tem
transfers by…
MTF: modulation-transfer functionNPS: noise-power spectrum
SNR: signal-to-noise ratioDQE: detective quantum effi-ciency
Radiation Imaging Laboratory, Pusan National UniversitySeungman Yun {[email protected]}
6 Nov 2014, 의공학개론 MTF, NPS, DQE
Imaging Performance Metrics• Why important??
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Taken from Dr. Ian Cunningham’s slides
High DQE Low DQE
Radiation Imaging Laboratory, Pusan National UniversitySeungman Yun {[email protected]}
6 Nov 2014, 의공학개론 MTF, NPS, DQE
Performance evaluation procedure
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)(NNPS)(MTF)(DQE
0
2
fqff
2D FFT
1D FFT
• Slit images• Gain-offset corrections
• Synthesizing LSF`s
• HVL measurements• Spectral simulation• Tuning kVp• Estimating fluence
• Scaling for non-uniformity• Averaging• Extracting 1D profiles
• White images• Gain-offset corrections• Detrending• Conversion into relative noise• Windowing
f
f
f
mmAl
I/I0
spec
tral d
ensit
y
MTF
1
DQE
Radiation Imaging Laboratory, Pusan National UniversitySeungman Yun {[email protected]}
6 Nov 2014, 의공학개론 MTF, NPS, DQE
Spatial Frequency & Nyquist Frequency• Spatial frequency? (line-pair/mm 1 cycle/mm)
– space domain: mm spatial frequency domain: mm-1
– inverse number of dimension: • low spatial frequency means large and blunt object• high spatial frequency means small and sharp object
• Nyquist frequency = maximum spatial frequency that the detector can dis-tinguish
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Pixel pitch 0.096 mm detectorNy = (2×0.096)-1 mm = 5.208 mm-1
Radiation Imaging Laboratory, Pusan National UniversitySeungman Yun {[email protected]}
6 Nov 2014, 의공학개론 MTF, NPS, DQE
Spatial Frequency for DR
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Radiation Imaging Laboratory, Pusan National UniversitySeungman Yun {[email protected]}
6 Nov 2014, 의공학개론 MTF, NPS, DQE
Fourier Transform• Any periodic function can be expressed as the sum of a series of
sines and cosines (of varying amplitudes)
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dkexfkF ikx2)()( )sin()cos( xixexi Note:
Radiation Imaging Laboratory, Pusan National UniversitySeungman Yun {[email protected]}
6 Nov 2014, 의공학개론 MTF, NPS, DQE
Imaging System Transfer Function
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Radiation Imaging Laboratory, Pusan National UniversitySeungman Yun {[email protected]}
6 Nov 2014, 의공학개론 MTF, NPS, DQE
Modulation Transfer Function
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Radiation Imaging Laboratory, Pusan National UniversitySeungman Yun {[email protected]}
6 Nov 2014, 의공학개론 MTF, NPS, DQE
• Spatial frequency domain analysis for impulsive excitation– How can we provide an impulse input to the imaging system? (edge and slit
device)
Modulation Transfer Function
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Slanted slit method
Slanted edge method
Extracting edge profile
Fine-sampling
Differentiation
1D Fourier transform
Edge spread function (step impulse response)
Line spread function (line impulse response)
)0(MTF]LSF[)(MTF FFTf
Extracting slit profile
Fine-sampling
Edge method
Slit method
???
Fine-sampling?? – synthesizing all the response profiles
Noise removing (Hann filter)
Radiation Imaging Laboratory, Pusan National UniversitySeungman Yun {[email protected]}
6 Nov 2014, 의공학개론 MTF, NPS, DQE
Commercial Products MTF
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Radiation Imaging Laboratory, Pusan National UniversitySeungman Yun {[email protected]}
6 Nov 2014, 의공학개론 MTF, NPS, DQE
과제 제출• Homework 2 (DIP): 11 월 13 일 ( 목 ) 강의시간
• Homework 3 (MTF): 11 월 20 일 ( 목 ) 강의시간
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