Comparison of noise power spectrum methodologies in measurements by using megavoltage X-ray energies

Jung Whan Min, Jin Hyun Son, Hoi Woun Jeong, Jung Min Kim, Youl Hun Seoung, Soon Yong Son, Ho Kyung Kim, Sang Young Kim, Do Wan Lee, Jae Yong Jung, Tae Suk Suh, Bo Young Choe

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3 Citations (Scopus)


The noise power spectrum (NPS) is one of the most general methods for measuring the noise amplitude and the quality of an image acquired from a uniform radiation field. The purpose of this study was to compare different NPS methodologies by using megavoltage X-ray energies. The NPS evaluation methods in diagnostic radiation were applied to therapy using the International Electrotechnical Commission standard (IEC 62220-1). In order to measure the region of interest (ROI) of the NPS, we used the following five factors: the overlapping impact, the non-overlapping impact, the penumbra, the flatness and different ROI sizes. We used NPS from four different types of detectors, the CR-IP (computed radiography image plate: photo-stimulable phosphor screen), the CR-IP-lead (hexalon lead screen), the CR-IP-back [lanex TM fast back screen: {terbium-doped gadolinium oxysulfide granular phosphor screen (Gd 2O 2S:Tb,133 mg/cm 2)} + 1-mm-thick copper plate and the CR-IP-front (lanex TM fast front screen). A Kodak 2000 RT photo-stimulable phosphor-based computed radiographic (CR) system showed that the normalized noise power spectrum (NNPS) curve gradually decreased, in compliance with increasing spatial resolution. In addition, each detector showed a different reactivity of the NPS to megavoltage. The results of multivariate analysis of variance (MANOVA) test (methods × detectors) revealed significant main effects of the methods [F(1, 4) = 53.543, P = 0.001 and of the detectors [F(1, 4) = 17.556, P = 0.001]. The present study revealed that various factors could be employed to produce megavoltage imaging (MVI) of the NPS and as a baseline standard for NPS control in MVI.

Original languageEnglish
Pages (from-to)129-136
Number of pages8
JournalJournal of the Korean Physical Society
Issue number1
Publication statusPublished - 2012 Jan


  • Megavoltage X-ray imaging (MVI)
  • Modulation transfer function (MTF)
  • Noise power spectrum (NPS)

ASJC Scopus subject areas

  • Physics and Astronomy(all)


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