디지털 래디오그라피 디텍터의 성능 -Modulation Transfer Function- 6 Nov 2014 Seungman Yun Radiation Imaging Laboratory, School of Mechanical Engineering, Pusan National University, South Korea

Radiation Imaging Laboratory, Pusan National University Seungman Yun 6 Nov 2014, 의공학개론 MTF, NPS, DQE 자료 다운로드 Lecture  Introduction to Medical Engineering 2

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 efficiency

Radiation Imaging Laboratory, Pusan National University Seungman Yun 6 Nov 2014, 의공학개론 MTF, NPS, DQE Imaging Performance Metrics Why important?? 4 Taken from Dr. Ian Cunningham’s slides High DQELow DQE

Radiation Imaging Laboratory, Pusan National University Seungman Yun 6 Nov 2014, 의공학개론 MTF, NPS, DQE Performance evaluation procedure 5 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/I 0 spectral density MTF 1 DQE

Radiation Imaging Laboratory, Pusan National University Seungman Yun 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 distinguish 6 Pixel pitch mm detector N y = (2×0.096) -1 mm = mm -1

Radiation Imaging Laboratory, Pusan National University Seungman Yun 6 Nov 2014, 의공학개론 MTF, NPS, DQE Spatial Frequency for DR 7

Radiation Imaging Laboratory, Pusan National University Seungman Yun 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) 8 Note:

Radiation Imaging Laboratory, Pusan National University Seungman Yun 6 Nov 2014, 의공학개론 MTF, NPS, DQE Imaging System Transfer Function 9

Radiation Imaging Laboratory, Pusan National University Seungman Yun 6 Nov 2014, 의공학개론 MTF, NPS, DQE Modulation Transfer Function 10

Radiation Imaging Laboratory, Pusan National University Seungman Yun 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 11 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) 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 University Seungman Yun 6 Nov 2014, 의공학개론 MTF, NPS, DQE Commercial Products MTF 12

Radiation Imaging Laboratory, Pusan National University Seungman Yun 6 Nov 2014, 의공학개론 MTF, NPS, DQE 과제 제출 Homework 2 (DIP): 11월 13일 (목) 강의시간 Homework 3 (MTF): 11월 20일 (목) 강의시간 13