Progress in Medical Physics (한국의학물리학회지:의학물리)

Korean Society of Medical Physics (한국의학물리학회)
권호 표지

Evaluation of Image Quality by Using a Tungsten Edge Block in a Megavoltage (MV) X-ray Imaging

텅스텐 엣지 블록을 이용하여 Megavoltage (MV) 영상의 질 평가

  • Min, Jung-Whan (Department of Biomedical Engineering, Research Institute of Biomedical Engineering, College of Medicine, The Catholic University) ;
  • Son, Jin-Hyun (Department of Radiological Science, The Shingu University College) ;
  • Kim, Ki-Won (Department of Radiological Science, The Shingu University College) ;
  • Lee, Jung-Woo (Department of Radiation Oncology, The Konkuk University Hospital) ;
  • Son, Soon-Yong (Department of Radiology Team, The Asan Medical Center) ;
  • Back, Geum-Mun (Department of Radiation Oncology Team, The Asan Medical Center) ;
  • Kim, Jung-Min (Department of College of Health Science, Radiologic Science, The Korea University) ;
  • Kim, Yeon-Rae (Department of Radiological Technology, Choonhae Health College) ;
  • Jung, Jae-Yong (Department of Biomedical Engineering, Research Institute of Biomedical Engineering, College of Medicine, The Catholic University) ;
  • Kim, Sang-Young (Department of Biomedical Engineering, Research Institute of Biomedical Engineering, College of Medicine, The Catholic University) ;
  • Lee, Do-Wan (Department of Biomedical Engineering, Research Institute of Biomedical Engineering, College of Medicine, The Catholic University) ;
  • Choe, Bo-Young (Department of Biomedical Engineering, Research Institute of Biomedical Engineering, College of Medicine, The Catholic University)
  • 민정환 (가톨릭대학교 성의교정 의과학연구원 의공학교실) ;
  • 손진현 (신구대학교 방사선과) ;
  • 김기원 (신구대학교 방사선과) ;
  • 이정우 (건국대학교병원 방사선종양학과) ;
  • 손순룡 (서울아산병원 영상의학과) ;
  • 백금문 (서울아산병원 방사선종양학과) ;
  • 김정민 (고려대학교 방사선과) ;
  • 김연래 (춘해보건대학 방사선과) ;
  • 정재용 (가톨릭대학교 성의교정 의과학연구원 의공학교실) ;
  • 김상영 (가톨릭대학교 성의교정 의과학연구원 의공학교실) ;
  • 이도완 (가톨릭대학교 성의교정 의과학연구원 의공학교실) ;
  • 최보영 (가톨릭대학교 성의교정 의과학연구원 의공학교실)
  • Received : 2012.05.26
  • Accepted : 2012.09.11
  • Published : 2012.09.30
Download PDF
⟨ Previous Next ⟩

Abstract

Digital Radiography (DR) has rapidly developed in megavoltage X-ray imaging (MVI). Thus, a very simple and general quality assurance (QA) method is required. The purpose of this study was to evaluate the modulation transfer function (MTF), the noise power spectrum (NPS) and the detective quantum efficiency (DQE) for MVI using general QA method and computed radiography (CR) device. We used tungsten edge block with $19{\times}10{\times}1cm^3$ thickness and 6MV energy. For detector, CR-IP (image plate), CR-IP-lead, the CR-IP-back (lanex TM fast back screen), CR-IP-front (lanex TM fast front screen) were used and pre-sampling MTF was calculated. The MTF of CR-IP-front showed the highest value with 1.10 lp/mm although the CR-IP showed the only 0.70 lp/mm. The best NPS was observed in CR-IP front screen. According to the increase in spatial frequency, our results showed that DQE was approximately 1.0 cycles/mm. The present study demonstrates that the QA method with our home-made edge block can be used to evaluate MTF, NPS and DQE for MVI.

최근 백만 볼트 영상(megavoltage imaging, MVI)에서 급격히 발전해 온 디지털 방사선영상(digital radiography, DR)은 치료용 방사선영상 기술이 발전함에 따라 매우 정확하면서 간단하게 측정할 수 있는 일반적인 정도관리(quality assurance, QA) 방법을 요구하게 되었다. 본 연구의 목적은 일반적인 QA 방법과 computed radiography (CR) 장비를 사용하여 MVI의 변조전달함수(modulation transfer function, MTF), 잡음전력스펙트럼(noise power spectrum, NPS), 양자검출효율(detective quantum efficiency, DQE)를 평가하고자 하였다. 텅스텐으로 구성된 $19{\times}10{\times}1cm^3$ 두께의 엣지(edge) 블록을 사용하였으며, 6 MV energy를 사용하였다. 또한 검출기는 CR-IP (image plate), CR-IP-lead, the CR-IP-back (lanex TM fast back screen), CR-IP-front (lanex TM fast front screen)를 사용하였으며, pre-sampling MTF를 계산하였다. CR-IP의 MTF는 0.70 lp/mm를 나타내었고, CR-IP front의 MTF는 1.10 lp/mm로서 가장 높은 값의 고해상도 공간분해능을 보였다. 가장 우수한 검출기의 NPS는 CR-IP front screen에서 확인되었다. 공간주파수가 증가함에 따라 1.0 cycles/mm의 가까운 DQE를 획득하였다. 본 연구결과로서 자체 제작한 엣지 블록 방법은 MVI의 MTF, NPS, DQE를 평가하는 일반적인 QA 방법으로 사용될 수 있음을 확인하여 주었다.

Keywords

References

  1. Antonuk LE: Electronic portal imaging devices: a review and historical perspective of contemporary technologies and research. Phys Med Biol 47:31-65 (2002) https://doi.org/10.1088/0031-9155/47/2/401
  2. Gayou O, Miften M: Commissioning and clinical implementation of a mega-voltage conebeam CT system for treatment localization. Med Phys 34:3183-3192 (2007) https://doi.org/10.1118/1.2752374
  3. Pouliot J, Bani-Hashemi A, Chen J, et al: Low-dose megavoltage cone-beam CT for radiation therapy. Int J Radiat Oncol Biol Phys 61:552-560 (2005) https://doi.org/10.1016/j.ijrobp.2004.10.011
  4. Langen KM, Meeks SL, Poole DO, et al: The use of megavoltage CT (MVCT) images for dose recomputations. Phys Med Biol 50:4259-4276 (2005) https://doi.org/10.1088/0031-9155/50/18/002
  5. Meeks SL, Harmon JF, Langen KM, et al: A Performance characterization of megavoltage computed tomography imaging on a helical tomotherapy unit. Med Phys 32:2673-2681 (2005) https://doi.org/10.1118/1.1990289
  6. Pang G, Rowlands JA: Development of high quantum efficiency, flat panel, thick detectors for megavoltage x-ray imaging: a novel direct conversion design and its feasibility. Med Phys 31:3004-3016 (2004) https://doi.org/10.1118/1.1803771
  7. Sawant A, Antonuk LE, El-Mohri Y, et al: Segmented phosphors: MEMS-based high quantum efficiency detectors for megavoltage x-ray imaging. Med Phys 32:553-565 (2005) https://doi.org/10.1118/1.1854774
  8. Sawant A, Antonuk LE, El-Mohri Y, et al: Segmented crystalline scintillators: An initial investigation of high quantum efficiency detectors for megavoltage x-ray imaging. Med Phys 32:3067-3083 (2005) https://doi.org/10.1118/1.2008407
  9. Rathee S, Tu D, Monajemi TT, et al: A bench-top megavoltage fan-beam CT using CdWO4-photodiode detectors. I. System description and detector characterization. Med Phys 33:1078-1089 (2006) https://doi.org/10.1118/1.2181290
  10. Samant SS, Gopal A: Analysis of the kinestatic charge detection system as a high detective quantum efficiency electronic portal imaging device. Med Phys 33:3557-3667 (2006) https://doi.org/10.1118/1.2241991
  11. Samant SS, Gopal A: Study of a prototype high quantum efficiency thick scintillation crystal video-electronic portal imaging device. Med Phys 33:2783-2791 (2006) https://doi.org/10.1118/1.2216877
  12. Judy PF: The line spread function and modulation transfer function of a computed tomographic scanner. Med Phys 3:233-236 (1976) https://doi.org/10.1118/1.594283
  13. Cunningham IA, Fenster A: A method for modulation transfer function determination from edge profiles with correction for finiteelement differentiation. Med Phys 14:533-537 (1987) https://doi.org/10.1118/1.596064
  14. Samei E, Flynn MJ, Reimann DA: A method for measuring the presampled MTF of digital radiographic systems using an edge test device. Med Phys 25:102-113 (1998) https://doi.org/10.1118/1.598165
  15. Buhr EG, Gunther-Kohfahl S, Neitzel U: Accuracy of a simple method for deriving the presampled MTF of a digital radiographic system from an edge image. Med Phys 30: 2323-2331 (2003) https://doi.org/10.1118/1.1598673
  16. Metz CE, Doi K: Transfer function analysis of radiographic imaging systems. Phys Med Biol 24:1079-1106 (1979) https://doi.org/10.1088/0031-9155/24/6/001
  17. Fujita H, Tsai DY, Itoh T, et al: A simple method for determining the modulation transferfunction in digital radiography IEEE Trans. Med Imaging 11:34-39 (1992) https://doi.org/10.1109/42.126908
  18. Dobbins JT, Ergun DL, Rutz L, et al: DQE_f_ of four generations of computed radiography acquisition devices. Med Phys 22:1581-1593 (1995) https://doi.org/10.1118/1.597627
  19. Droege RT, Morin RL: A practical method to measure the MTF of CT scanners. Med Phys 9:758-760 (1982) https://doi.org/10.1118/1.595124
  20. Droege RT, Rzeszotarski MS: An MTF method immune to aliasing. Med Phys 12:721-725 (1985) https://doi.org/10.1118/1.595654
  21. Munro P, Rawlinson JA, Fenster A: Therapy imaging (A signal-to-noise analysis of a fluoroscopic imaging system for radiotherapy localization). Med Phys 17:763-772 (1990) https://doi.org/10.1118/1.596474
  22. El-Mohri Y, Jee KW, Antonuk LE, et al: Determination of the detective quantum efficiency of a prototype, megavoltage indirect detection, active matrix flat-panel imager. Med Phys 28: 2538-2550 (2001) https://doi.org/10.1118/1.1413516
  23. Antonuk LE, El-Mohri Y, Siewerdsen JH, et al: Empirical investigation of the signal performance of a high-resolution, indirect detection, active matrix flat-panel imager (AMFPI) for fluoroscopic and radiographic operation. Med Phys 24:51-70 (1997) https://doi.org/10.1118/1.597918
  24. Antonuk LE, El-Mohri Y, Huang W, et al: Initial performance evaluation of an indirect-detection, active matrix flat-panel imager AMFPI_ prototype for megavoltage imaging. Int J Radiat Oncol Biol Phys 42:437-454 (1998) https://doi.org/10.1016/S0360-3016(98)00210-7
  25. Park HS, Cho HM, Jung J, et al: Comparison of the image Noise Power Spectra for Computed Radiography. Korean Phys Soc 54:236-243 (2009) https://doi.org/10.3938/jkps.54.236
  26. Cho HS, Ghoi SG, Lee BS, et al: Image quality evaluation of highly-intergrated digital X-ray imaging sensor for dental intraoral- imaging applications. Korean Phys Soc 51:30-34 (2007) https://doi.org/10.3938/jkps.51.30
  27. Rampado O, Isoardi P, Ropolo R: Quantitative assessment of computed radiography quality control parameters. Phys Med Biol 51:1577-1593 (2006) https://doi.org/10.1088/0031-9155/51/6/015
  28. Ciantar D, Fitzgerald M, Cotterill AD, et al: Correlation between quantitative and subjective assessment of image quality in paediatric radiology. Radiat Prot Dosim 90:185-188 (2000) https://doi.org/10.1093/oxfordjournals.rpd.a033115
  29. Rogers DWO: Fluence to dose equivalent conversion factors calculated with EGS3 for electrons from 100 keV to 20 GeV and photons from 20 keV to 20 GeV. Health Physics 46: 891-914 (1984) https://doi.org/10.1097/00004032-198404000-00015
  30. Mohan R, Chui CS, Lidofsky L: Energy and angular distributions of photons from linear accelerators. Med Phys 12: 592-597 (1985) https://doi.org/10.1118/1.595680
  31. Giger ML, Doi K: Investigation of basic imaging properties in digital radiography. 1. Modulation transfer function. Med Phys 11: 287-295 (1984) https://doi.org/10.1118/1.595629
  32. Giger ML, Doi K, Metz CE: Investigation of basic imaging properties in digital radiography. 2. Noise Wiener Spectrum. Med Phys 11:797-805 (1984) https://doi.org/10.1118/1.595583
  33. Dobbins III JT, Samei E, Ranger NT, et al: Intercomparison of methods for image quality characterization. II. Noise power spectrum. Med Phys 33:1466-1475 (2006) https://doi.org/10.1118/1.2188819
  34. Nath R, Biggs PJ, Bova FJ, et al: AAPM code of practice for radiotherapy accelerators AAPM code of practice for radiotherapy accelerators. Med Phys 21:1093-1121 (1994) https://doi.org/10.1118/1.597398
  35. Min JW, Suh TS, Choe BY, et al: Comparison of noise power spectrum methodologies in measurements by using megavoltage X-ray energies. Korean Phys Soc 60:129-136 (2012) https://doi.org/10.3938/jkps.60.129
  36. Gopal A, Samant SS: Use of a line-pair resolution phantom for comprehensive quality assurance of electronic portal imaging devices based on fundamental imaging metrics. Med Phys 36: 2006-2015 (2009) https://doi.org/10.1118/1.3099559