1381 総説 ディジタル画像の画質と被ばくを考慮した適正線量の研究 岸本健治 1) 有賀英司 2) 石垣陸太 3) 今井方丈 4) 川本清澄 5) 6) 小林謙一澤田道人 7) 能登公也 8) 中前光弘 9) 10) 東出了 論文受付 2011 年 8 月 9 日 論文受理 2011 年 10 月 7 日 Code Nos. 253 522 621 1) 大阪市立大学医学部附属病院中央放射線部 2) 名古屋第 2 赤十字病院 3) 京都医療科学大学 4) 滋賀医科大学医学部附属病院 5) 大阪大学医学部附属病院 6) 藤田保健衛生大学病院 7) 有限会社ムツダ商会 8) 金沢大学附属病院 9) 奈良県立医科大学附属病院 10) 名古屋市立大学病院 はじめに F/S 1983 CR 1998 FPD 2001 2007 88.9 1, 2 Study of Appropriate Dosing in Consideration of Image Quality and Patient Dose on the Digital Radiography Kenji Kishimoto, 1) Eiji Ariga, 2) Rikuta Ishigaki, 3) Masatake Imai, 4) Kiyosumi Kawamoto, 5) Kenichi Kobayashi, 6) Michito Sawada, 7) Kimiya Noto, 8) Mitsuhiro Nakamae, 9) and Ryo Higashide 10) 1) Department of Radiology, Osaka City University Hospital 2) Depertment of Radiological Technology, Nagoya Daini Red Cross Hospital 3) Kyoto College of Medical Science, Faculty of Medical Science 4) Department of Radiology, Shiga University of Medical Science Hospital 5) Department of Radiology, Osaka University Hospital 6) Department of Radiology, Fujita Health University Hospital 7) MUTSUDA SHOUKAI CORPORATION, LTD. 8) Department of Radiology, Kanazawa University Hospital 9) Central Division of Radiology, Nara Medical University Hospital 10) Central Department of Radiology, Nagoya City University Hospital Received August 9, 2011; Revision accepted October 7, 2011; Code Nos. 253, 522, 621 Summary Recently about 90% of radiographs have been taken by the digital radiographic system in Japan, but the exposure dose of the patients are about ten-times different among the systems. We understood it by a surveytaken in 2007. We studied the visual evaluation with varying exposure doses using the image phantom of the lumber AP, lumber lateral and hip AP. Additionally we measured quantum efficiency (DQE) of the digital systems. We also studied the exposure index (EI) of IEC standard to see whether it is able to be the sensitivity index among the digital systems. DQE in 1.0 cycle/mm of CR, FPD (GOS), FPD (CsI, a-se) became 0.2 0.25, 0.3, 0.5, respectively. Our results display that the dose reduction is relative to DQE. The visual evaluation results also show that dose reduction is possible among the systems. From these results, we are able to reduce the exposure dose of the patients at the clinical site. We also suggest that we manage the exposure dose using the E.I of the IEC standard. Key words: digital radiography, patient dose, image quality, detective quantum efficiency (DQE) 545-8586 1-5-7
1382 Fig. 1 Results of a survey on the image receptor system. 10 22 1 19 2 exposure index 3 4 5 5 4 3 3 1 2007 17 第 1 章一般撮影における患者が受ける線量の現状 - 平成 19 年度全国調査から- はじめに 19 X X 1, 2 22 Fig. 2 Transition of the image receptor system. 1-1 2007 19 1-1-1 3,000 782 26.1 1-1-2 computed radiography CR 69.4 flat panel detector FPD 2.2 CR FPD 17.3 film-screen F/S 11.1 Fig. 1 3 F/S 2001 1997 2007 10 Fig. 2 1-1-3 50 X 100 X entrance surface dose; ESD ESD 3/4 75 Table 1 75 10 10 10 2001 2007 coefficient of variation; CV 2007 CV 10 Fig. 3 5 4 7 1973 5 100 Fig. 4 F/S 1993 1993 FCR9000 2 67 11
1383 Table 1 Results of a survey on ESD Examination n Mean SD 75%dose Max Min Skull AP/PA 712 2.39 1.66 2.87 22.86 0.05 Skull LAT 703 1.82 1.21 2.21 13.36 0.19 Cervical spine AP 711 0.90 0.83 1.03 12.76 0.07 Thoracic spine AP 692 3.37 2.97 3.93 46.77 0.16 Thoracic spine LAT 687 5.73 5.07 6.91 65.70 0.24 Lumbar spine AP 707 4.06 2.31 5.17 16.23 0.25 Lumbar spine LAT 703 11.34 7.98 14.16 77.65 0.50 Pelvis AP 702 3.12 2.61 3.65 30.01 0.29 Femur 697 1.99 1.51 2.39 17.72 0.09 Forearm 706 0.18 0.27 0.19 5.22 0.01 Ankle joint 709 0.21 0.19 0.25 2.74 0.02 Chest low voltage 258 0.42 0.63 0.44 7.26 0.01 Chest medium voltage 251 0.49 0.38 0.62 3.11 0.01 Chest high voltage 721 0.26 0.26 0.30 2.99 0.02 Abdomen 703 2.52 2.60 3.00 34.13 0.01 Guthmann 328 5.65 5.55 6.77 50.55 0.23 Martius 308 6.02 5.07 7.60 35.32 0.24 Infant hip joint 475 0.19 0.21 0.21 2.09 0.01 Infant chest 490 0.18 0.26 0.19 3.91 0.01 Pediatric chest 527 0.25 0.42 0.24 4.70 0.01 Breast 434 1.61 0.63 1.91 5.12 0.0005 unit: mgy Fig. 3 Comparison of the CV value on A.D 2007 and A.D. 2001. Fig. 4 Transition of the ESD and sale time of the image receptor system.
1384 Fig. 5 Comparison of the ESD in FPD, CR and F/S. Fig. 6 Cumulative curve in the lumbar spine AP, the lumbar spine LAT and the pelvis AP examination. (a) X-ray tube voltage in the lumbar spine AP examination (b) X-ray tube voltage in the lumbar spine LAT examination (c) X-ray tube voltage in the pelvis AP examination (d) Value of mas in the lumbar spine AP examination (e) Value of mas in the lumbar spine LAT examination (f) Value of mas in the pelvis AP examination 3 Fig. 5 F/S CR FPD mas Fig. 6 CR F/S mas FPD 20 20 Fig. 7 FPD CR FPD cesium iodide 67 11
1385 Fig. 7 The image receptor system of low dose and high dose at the lumbar spine LAT examination in 20 facilities. CsI gadolinium-oxide sulfide GOS CsI Fig. 8 1-2 1 2003 8 50 2 CR PMT 3 dose index 4 F/S CR FPD CsI GOS FPD 5 ICRP Publ.93 9 guest editorial 6 Fig. 8 Comparison of the ESD of the lumbar spine LAT examination in indirect FPD systems. Dose (%) Table 2 modality worklist management MWM 1-3 2007 75 Table 2 4 1-4 Results of ESD below 75% dose ESD (mgy) Lumbar spine Lumbar spine Pelvis AP LAT AP 75 5.17 14.16 3.65 50 3.65 9.71 2.57 25 2.39 6.56 1.78 10 1.74 4.44 1.24 5 1.27 3.19 0.99 3 1.05 2.64 0.83 1 0.7 1.47 0.54
1386 Fig. 9 Geometry for calibration of IEC 62494. 第 2 章ディジタル装置の感度指標としての exposure index はじめに X 1 exposure index 2-1 Exposure index IEC X exposure index; EI 10 IEC EI Fig. 9 EI EI=c 0 g(v) 1 c 0 100 μgy 1 g(v) V: value of interest K EI EI=c 0 K cal 2 K cal K cal=g(v cal) 3 EI 100 2-2 EI g(v) 11 Fig. 10 3 CR Fig. 11 3 Philips FPD S K EI Fig. 10 11 100 μgy 1 Fig. 10 CR A B 9 C 50 S S 67 11
1387 Fig. 10 Relationship between S number and K. Fig. 11 Relationship between value of interest. Fig. 11 FPD 3 μgy ±15 CR FPD CR FPD 2-3 EI EI IEC 62494 EI target exposure index EI T deviation index DI EI T DI EI T EI 9 DI = log 10 10 EI 4 EI T 2 DI 0.0 3.0 EI T 1 EI T 2 EI T EI T 2 EI T 2-4 EI T EI DI EI DI 90 kv X 12 EI
1388 Table 3 Specification of digital radiography systems evaluated in the study System Manufacturer Technology Pixel size (mm) FUJIFILM DR BENEO Fujifilm medical Direct FPD 0.150 Difinium 8000 GE Healthcare Indirect FPD CsI 0.200 Digital Diagnost Philips Indirect FPD CsI 0.143 FUJIFILM DR CALNEO U Fujifilm medical Indirect FPD GOS 0.150 REGIUS MODEL 170 [RP-3S] Konica Minolta CR 0.175 FCR PROFECT CS [ST-VI] Fujifilm medical CR 0.100 FCR 5000 [ST-V N] Fujifilm medical CR 0.100 2-5 IEC62494 EI EI T 第 3 章物理評価による検出器の検出量子効率評価 3-1 X CR FPD X X X CR CR CR FPD 1, 13 2 detective quantum efficiency DQE 14 16 DQE 3-2 4 7 Table 3 FPD FUJIFILM DR BENEO BENEO 1 FPD 3 CsI Difinium 8000 Difinium Digital Diagnost DiDi 2 Gd 2O 2S GOS FUJIFILM DR CALNEO U CALNEO 1 CR REGIUS MODEL 170 REGIUS FCR PROFECT CS PROFECT FCR 5000 3 DiDi 6 DiDi DiDi 4 presampled modulation transfer function presampled MTF Wiener spectrum WS DQE X IEC 61267 17 RQA5 presampled MTF WS IEC 62220-1 18 19 18, 20 presampled MTF 2 CR WS 2 DQE X q presampled MTF WS q IEC 62220-1 2 MTF (f) DQE(f) = 5 q WS(f) 67 11
1389 Fig. 12 Determination of presampled MTF in respective systems. Fig. 13 Determination of WS in respective systems. Fig. 14 Relation between air Kerma and WS values at 1.0 cycles/mm. Fig. 15 Determination of DQE in respective systems. 3-3 Fig. 12 15 presampled MTF WS DQE 2 DiDi 6 3-3-1 Presampled MTF Fig. 12 presampled MTF DiDi FPD BENEO MTF FPD CsI GOS CR
1390 CR 3 FPD CsI GOS MTF FPD Difinium CALNEO MTF 3-3-2 WS X 2.19 μgy 0.25 mr WS Fig. 13 2.19 μgy WS X 2.19 μgy WS WS 2.19 μgy WS DiDi FPD FPD GOS CR FPD CsI Difinium WS FPD CR WS FPD BENEO MTF WS FPD GOS CALNEO FPD CsI Difinium WS CR PROFECT WS 3 WS Fig. 14 1.0 cycle/mm WS 1.0 cycle/mm WS FPD CsI Difinium DiDi FPD GOS FPD CR3 WS 3-3-3 DQE Fig. 15 2.19 μgy 0.25 mr DQE DiDi DQE 1.3 cycles/mm FPD CsI Difinium 1.3 cycles/mm FPD BENEO FPD GOS CALNEO CR 3 DQE Difinium BENEO DQE CR REGIUS DQE PROFECT FCR 5000 Table 4 1.0 cycle/mm DQE FPD BENEO FPD CsI Difinium 0.5 FPD GOS CALNEO 0.31 CR 3 0.20 0.26 Table 4 DQE value at 1.0 cycles/mm System DQE value at 1.0 cycle/mm BENEO 0.501 Difinium 0.525 CALNEO 0.306 REGIUS 0.257 PROFECT 0.207 FCR5000 0.201 DiDi 0.667 3-4 DiDi FPD BENEO FPD CsI Difinium DQE BENEO Difinium FPD GOS CALNEO CR 3 1.0 cycle/mm DQE FPD BENEO FPD CsI Difinium 0.5 FPD GOS CALNEO 0.31 CR 3 0.20 0.26 FPD FPD CsI DQE FPD FPD GOS FPD FPD CsI 60 DQE CR FPD FPD CsI DQE 2 FPD GOS DQE 1.2 1.5 CR 2 DQE FPD FPD CsI CR 1/2 DQE 21 DQE 3-5 67 11
1391 Table 5 The relationship between exposure and skin dose with lumber spine (A-P view), lumber spine (Lateral view) and hip joint (A-P view) The current time product of lumber spine (A-P view), x-ray tube voltage is at 75 kv Grid ratio Grid density CR (FCR5000) 40.0 25.0 20.0 16.0 12.5 8.0 6.3 4.5 3.2 10 1 36 FPD CsI (DiDi) 40.0 25.0 20.0 16.0 12.5 8.0 6.3 5.0 2.5 12 1 36 Exposure dose 5.42 2.15 1.72 1.38 1.08 0.77 0.54 0.45 0.39 0.28 0.22 FPD The current time product of lumber spine (lateral view), x-ray tube voltage is at 85 kv Grid ratio Grid density CR (FCR5000) 63.0 40.0 32.0 20.0 16.0 12.5 8.0 10 1 36 FPD CsI (DiDi) 40.0 25.0 20.0 16.0 12.5 8.0 6.3 5.0 2.5 12 1 36 Exposure dose 12 7.62 6.1 4.76 3.81 3.05 2.38 1.52 1.17 0.98 0.48 The current time product of hip joint (A-P view), x-ray tube voltage is at 75 kv Grid ratio Grid density CR (FCR5000) 36.0 20.0 16.0 12.5 10.0 7.1 5.0 3.6 10 1 36 FPD CsI (DiDi) 32.0 20.0 16.0 12.5 10.0 6.3 5.0 3.2 12 1 36 Exposure dose 3.12 3.1 1.73 1.39 0.99 0.87 0.62 0.54 0.43 0.36 0.33 unit: mgy DQE 第 4 章 視覚評価による適正線量 はじめに 90 1 10 4-1 CR 1 FPD 1 CR FCR5000 Imaging Plate; ST type FPD CsI Gd 2O 2S Tb GOS FPD CsI Philips Digital Diagnost CR CR FCR5000 Fig. 16 The filing form of observation scores and examples. FPD FPD CsI DiDi Table 5 1 X SDEC 22 2 1 3 6 12 1 100 Fig. 16 50
1392 Fig. 17 Observer s score and average score. (a) CR (FCR5000) on lumber spine (A-P view) (b) FPD CsI (DiDi) on lumber spine (A-P view) (c) CR (FCR5000) on lumber spine (lateral view) (d) FPD CsI (DiDi) on lumber spine (lateral view) (e) CR (FCR5000) on hip joint (A-P view) (f) FPD CsI (DiDi) on hip joint (A-P view) Fig. 16 10 cm 75 4-2 Fig. 17a CR FCR5000 mgy 0.77 mgy Fig. 17b FPD CsI DiDi 67 11
1393 Fig. 18 Comparison of the average scores between CR (FCR5000) and FPD CsI (DiDi) on lumber spine (A-P view), lumber spine (lateral view) and hip joint (A-P view). (a) Lumber spine (A-P view) (b) Lumber spine (lateral view) (c) Hip joint (A-P view) 1.08 mgy 0.54 mgy Fig. 17c d Fig. 17e f Fig. 18a CR FCR5000 FPD CsI DiDi 50 Tukey-Kramer CR FCR5000 0.77 mgy 0.28 mgy 5.42 mgy FPD CsI DiDi 0.54 mgy 0.22 mgy 5.42 mgy Fig. 18b CR FCR5000 FPD CsI DiDi 50 Tukey-Kramer Fig. 18c CR FCR5000 FPD CsI DiDi 50 Tukey-Kramer CR FCR5000 FPD CsI DiDi 50 4-3 50 Table 6 X 1 Table 2
1394 Table 6 Relation between image quality of diagnostic confidence level and minimum required values of exposure dose in this study CR (FCR5000) FPD CsI (DiDi) Lumber spine 0.77 0.54 A-P view (0.39 2.15) (0.45 2.15) Lumber spine 6.10 3.81 Lateral view (>3.81) (>2.38) Hip joint 0.43 0.33 A-P view (<1.39) ( ) unit: mgy 4-3-1 50 4-3-2 23 100 60 35 5 60 100 35 60 35 100 4-3-3 CR CR FCR5000 FPD FPD CsI DiDi FPD CsI DiDi 3 DQE Table 4 X DQE 4-3-4 X exposure index 4-4 CR FCR5000 FPD CsI DiDi 第 5 章まとめと今後の課題 5-1 1 2007 10 2001 2007 90 2001 24 2007 67 11
1395 75 1 Table 1 2000 FPD CsI CR DQE 25 CR FPD GOS CR DQE CR 26 2 IEC 2006 EI EI 3 DQE DQE DQE 1 CR FPD CsI FPD GOS CsI GOS CsI DQE DQE 1.0 cycle/mm CR FPD GOS FPD CsI FPD a-se 0.2 0.25 0.3 0.5 FPD CsI FPD a-se 1 CR FPD GOS FPD CsI FPD a-se 2.5 2 1.75 1 4 4 Table 5 1 Table 2 3 CR FCR5000 FPD CsI DiDi 2 CR FCR5000 FPD CsI DiDi CR FCR5000 flexible noise control FNC 27 DR FPD CsI DiDi Low-pass filter Wiener filter detail contrast enhancement DCE noise compensation NC 28 3 4 Table 6 1 Table 2 75 1/5 Table 2 1/3 CR FPD CsI DiDi DQE 3 Table 4 3 CR FPD CsI DiDi DQE EI 5-2 謝辞 2007 19 X
1396 38 参考文献 1 X 2009; 65(5): 681-685. 2 X 2 2009; 65(11): 1582-1590. 3 2003 X 2005; 75(2): 55-62. 4 1976; 32(1): 34-39. 5 X 1973 M 1980; 12(6): 324-327. 6 X 1973 1979 M 1990; 22(6): 359-363. 7 X 23 1999; 46(4): 382-393. 8 CR 2005; 61(11): 1510-1520. 9 ICRP Publication 93. Managing patient dose in digital radiology, 2004. 10 IEC62494-1. Medical electrical equipment Exposure index of digital X-ray imaging systems, Part 1: Definition and requirements for general radiography, Ed. 1, 2008. 11 Exposure Index 2011; 67(11):1433-1437. 12 Ariga E, Ito S, Deji S, et al. Development of dosimetry using detectors of diagnostic digital radiography systems. Med Phys 2007; 34(1): 166-174. 13 17 X 2009; 65(3): 323-331. 14 Dainty JC, Shaw R. Image science. Academic Press, London, 1974. 15 DQE NEQ 2010; 66(8): 958-966. 16 Detective Quantum Efficiency DQE 2010; 66(1): 88-93. 17 IEC 61267. Medical diagnostic X-ray equipment-radiation conditions for use in the determination of characteristics, Ed. 2.0, 2005. 18 IEC 62220-1. Medical electrical equipment Characteristics of digital X-ray imaging devices, Part1: Determination of the detective quantum efficiency, Ed. 1.0, 2003. 19 presampled MTF 2008; 64(4): 417-425. 20 IEC 62220-1-2. Medical electrical equipment Characteristics of digital X-ray imaging devices, Part 1-2: Determination of the detective quantum efficiency, Detectors used in mammography, Ed. 1.0, 2007. 21 DQE 2009; 32(2): 27-32. 22 X SDEC 2009; 65(10): 1400-1406. 23 1996; 52(9): 1136. 24 2002. 25 2002; 58(4): 455-461. 26 2001; 57(5): 587-592. 27 FCR II 2007: 1-6. 28 Digital Diagnost Innervision 2007; 22(2): 29-34. 67 11
1397 図表の説明 Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. 7 Fig. 8 Fig. 9 Fig. 10 Fig. 11 Fig. 12 Fig. 13 Fig. 14 Fig. 15 Fig. 16 Fig. 17 Fig. 18 2001 2007 CV mas a b c d mas e mas f mas 20 20 FPD IEC62494 S K air kerma K air kerma presampled MTF WS Air kerma 1.0 cycles/mm WS DQE a CR FCR5000 b FPD CsI DiDi c CR FCR5000 d FPD CsI DiDi e CR FCR5000 f FPD CsI DiDi CR FCR5000 FPD CsI DiDi a b c Table 1 Table 2 75 Table 3 X Table 4 1.0 cycle/mm DQE Table 5 mas Table 6