Prog Med Phys.  2012 Sep;23(3):154-161.

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

Affiliations
  • 1Department of Biomedical Engineering, Research Institute of Biomedical Engineering, College of Medicine, The Catholic University, Seoul, Korea. bychoe@catholic.ac.kr
  • 2Department of Radiological Science, The Shingu University College, Seongnam, Korea.
  • 3Department of Radiation Oncology, The Konkuk University Hospital, Seoul, Korea.
  • 4Department of Radiology Team, The Asan Medical Center, Seoul, Korea.
  • 5Department of Radiation Oncology Team, The Asan Medical Center, Seoul, Korea.
  • 6Department of College of Health Science, Radiologic Science, The Korea University, Seoul, Korea.
  • 7Department of Radiological Technology, Choonhae Health College, Ulsan, Korea.

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 19x10x1 cm3 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.

Keyword

Modulation transfer function (MTF); Noise power spectrum (NPS); Detective quantum efficiency (DQE); Megavoltage x-ray imaging (MVI)

MeSH Terms

Noise
Radiographic Image Enhancement
Tungsten
Tungsten
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