Technical Note: Improved CT number stability across patient size using dual-energy CT virtual monoenergetic imaging

Gregory Michalak, Joshua Grimes, Joel Fletcher, Ahmed Halaweish, Lifeng Yu, Shuai Leng, Cynthia McCollough

Research output: Contribution to journalArticlepeer-review

20 Scopus citations


Purpose: The purpose of this study was to evaluate, over a wide range of phantom sizes, CT number stability achieved using two techniques for generating dual-energy computed tomography (DECT) virtual monoenergetic images. Methods:Water phantoms ranging in lateral diameter from 15 to 50 cm and containing a CT number test object were scanned on a DSCT scanner using both single-energy (SE) and dual-energy (DE) techniques. The SE tube potentials were 70, 80, 90, 100, 110, 120, 130, 140, and 150 kV; the DE tube potential pairs were 80/140, 70/150Sn, 80/150Sn, 90/150Sn, and 100/150Sn kV (Sn denotes that the 150 kV beam was filtered with a 0.6 mm tin filter). Virtual monoenergetic images at energies ranging from 40 to 140 keV were produced from the DECT data using two algorithms, monoenergetic (mono) and monoenergetic plus (mono+). Particularly in large phantoms, water CT number errors and/or artifacts were observed; thus, datasets with water CT numbers outside ± 10 HU or with noticeable artifacts were excluded from the study. CT numbers were measured to determine CT number stability across all phantom sizes. Results: Data exclusions were generally limited to cases when a SE or DE technique with a tube potential of less than 90 kV was used to scan a phantom larger than 30 cm. The 90/150Sn DE technique provided the most accurate water background over the large range of phantom sizes evaluated. Mono and mono+ provided equally improved CT number stability as a function of phantom size compared to SE; the average deviation in CT number was only 1.4% using 40 keV and 1.8% using 70 keV, while SE had an average deviation of 11.8%. Conclusions: The authors report demonstrates, across all phantom sizes, the improvement in CT number stability achieved with mono and mono+ relative to SE.

Original languageEnglish (US)
Pages (from-to)513-517
Number of pages5
JournalMedical physics
Issue number1
StatePublished - Jan 1 2016


  • dual-energy CT
  • monoenergetic
  • stability

ASJC Scopus subject areas

  • Biophysics
  • Radiology Nuclear Medicine and imaging


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