Arts and Sciences computed radiography CRpresampled MTF Measurement of presampled MTFs with computed radiography (CR) by contrast method using smoothed square-wave. 1 16813 1, 2 1 1 1 2 Key words: contrast method, square wave response function (SWRF), presampled MTF, Sampling bin, square -wave chart Abstract The presampled modulation transfer function (MTF) was determined with a computed radiography (CR) system, using the contrast and edge methods. In the contrast method, the smoothing of profiles presented in a square-wave chart was performed at different effective sampling points, based on the sample theorem. High and low spatial frequencies in each profile were easily measured, and stable presampled MTF performances were achieved for standard (ST) and high quality (HQ) images. In the edge method, the line spread function (LSF) was extrapolated in an exponential manner until its intensity ratio was 1:1,000, and stable presampled MTF performances were achieved for standard (ST) and high quality (HQ) images. To improve the accuracy of measurements, presampled MTF was determined five times to calculate the mean, and there were no significant differences among the measurements. These results suggest that the contrast method is a simple, excellent method in which samples for the determination of presampled MTF can be easily prepared and the measurement principle can be clearly understood. computed radiography system CR presampled MTF modulation transfer function MTF profile sampling sampling distance smoothing top bottom ST HQpresampled MTF line spread function LSF1000 1 ST HQ presampled MTF 5presampled MTF presampled MTF digital radiography DRcomputed radiography CR flat panel detector Yasuo Mochizuki 1) 1, 2) (16813), Ryo Kasahara Daisuke Ueda 1), Masumi Takeda 1) 1) Department of Radiological Technology, Faculty of Health Sciences, Nihon Institute of Medical Science. 2) Now at Kashiwazaki General Hospital and Medical Center. FPD presampled modulation transfer function MTFInternational Electrotechnical Commission IEC Buhr 1 Samel 2 top bottom presampled MTF 3 screen-film system S/FMTF presampled MTF 4 square wave response function SWRFMTF 35 411
S/F MTF 5 Regius 170 2003 presampled MTF MTF X 3 presampled MTF CR Regius 170 ST 175 m HQ 87.5 m presampled MTF 1. presampled MTF 1-1 S/F CR sampling of rectangle filter sampling bin bin bin bin 2 0.01 0.02 0.03mm S/F Fig. 1 Composite chart image generated from chart images corresponding to various alignments of the square-wave chart. (a): Profile of original data. (b): A bin smoothing processing to profile of data Fig. 1 0.003mm 0.030mm bin 0.5cycle/mm1.0 cycle/mm S/F 6 1-2 Type 1 2 4 60kV 100 ma 25msec 200cm DICOM Image J PC CSV tan 36 412 2013. vol.60 no.726
computed radiography CRpresampled MTF Arts and Sciences bin 1022 SWRF 3 SWRF SWRF70cycles/mm 6 4 presampled MTFMTF Regius 170 ST HQ5 2. 2-1 presampled MTF Fig. 2 ST HQ bin 0.01 0.02 0.03 mm5presampled MTF 1-3 presampled MTF 2.0 200cm 60kV 7 mas 80% DICOM Image J PC CSV 2.0 /tan1 28 bin0.020mm 1 line spread function LSF 8 LSF presampled MTF 8 presampled MTF Regius 170 ST HQ 5 MTF discrete Fourier transform: DFT X R20 Fig. 2 Presampled MTFs in the horizontal and vertical direction on Standard image (ST) and High quality image (HQ) obtained by contrast method. (a) bin with 0.01mm (b) bin with 0.02mm (c) bin with 0.03mm 37 413
2-2 presampled MTF LSF 0.004 0.0025 S/F 1000 1 LSF presampled MTF Fig. 3 bin 0.02mm ST HQ presampled MTF 5 Fig. 3 Presampled MTFs in the horizontal and vertical direction on ST and HQ obtained by edge method. ST HQ MTF HQ MTFST MTF Table 12.0 cycles/mm MTF bin MTF Table 1 Average Presampled MTF values at 2 cycles/mm obtained by five different time measurements and their standard deviations for ST and HQ obtained by contrast method and edge method. 3. Regius 170 presamled MTF bin Fig. 1 PC bin PC 5 presamled MTF MTFST HQ MTF ST SWRF MTF ST 2.86cycles/mm HQ 5.71cycles/mm ST bin 0.01 0.02 0.03mm MTF presamled MTFST ST HQ MTF MTF MTF Fig. 2 4 CR A/D 9 MTF bin MTF MTF bin0.01mm 0.02mm 0.03 mmbin bin SWRF bin 38 414 2013. vol.60 no.726
computed radiography CRpresampled MTF Arts and Sciences XX 9 3Regius 170 presamled MTF 2.0 cycles/mm MTFbin 0.356 0.31 2 0.32bin 10 20% 7 ST HQ 0.0175mm bin 0.020mm bin MTF MTF t- ST HQ MTF 5% t-p 2.79 5 MTF 2.0cycles/mm 0.032 Table 2 Regius 170 Table 2 Difference between MTF values at 2 cycles/mm obtained by contrast method and edge method. 2.0cycles/mm presampled MTF MTF 7 bin 2.0cycles/mm MTF 0.26% Table 1 2 3% 11 S/F MTF PC 12 4. CRRegius 170 bin 0.01 0.02 0.03mm presampled MTFMTF 5 MTF ST HQ2.0cycles/mm 0.26% presampled MTF 1 Buhr, E, et al: Accuacy of a simple method for deriving the presampled modulation transfer function of a digital radiographic system from an edge image. Med. Phys, 30,2323-2331, (2003). 2 Samel. E, et al: A methed for measuring the presampled MTF of digital radiographic system using an edge test device. Med, Phys, 25, 102-113, (1998). 3, MTF., 58(9) 1261-1267, (2002). 4, MTF., 61(9), 13551-1357, (2005). 5, 16(3), 129-137, 1996. 6 MTF INNERVISON. 3-5, 52 56, (1988). 7, presampled MTF., 64(4), 417-425, (2008). 8 Excel MTF. 2, INNERVISON. 19-1, 37-43, (2004). 9,., 57(1), 68-77, (2001). 10, CR 2., Vol 14, 210-212, 2005. 11 Junji Morishita, et al: Comparison of two methds for accurate measurement of modulation transferfunctions of screen-film systems. Med, Phys, 22(2), 193-200, (1995) 12, X TV., 51(11), 1635-1640, (1995). 39 415