Feasibility and accuracy of relative electron density determined by virtual monochromatic CT value subtraction at two different energies using the gemstone spectral imaging

Radiation Oncology

Masahiko Koizumi²  Kazuhiko Ogawa⁴  Noriyuki Tomiyama¹  Yasuo Yoshioka⁴  Fumiaki Isohashi⁴  Ryota Ogihara³  Chikako Tanaka³  Sachiko Yamada³  Masashi Yagi⁴  Takashi Ueguchi³  Toshiyuki Ogata³ 

[1] Department of Radiology, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka, Japan;Division of Medical Physics, Oncology Center, Osaka University Hospital, 2-15 Yamadaoka, Suita, Osaka, Japan;Department of Radiology, Osaka University Hospital, 2-15 Yamadaoka, Suita, Osaka, Japan;Department of Radiation Oncology, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka, Japan

关键词: Computed tomography;    Dual energy;    Relative electron density;    Monochromatic images;    Gemstone spectral imaging;   

Others  :  1154220
DOI  :  10.1186/1748-717X-8-83

 received in 2012-08-06, accepted in 2013-04-04,  发布年份 2013

【 摘 要 】

Background

Recent work by Saito (2012) has demonstrated a simple conversion from energy-subtracted computed tomography (CT) values (ΔHU) obtained using dual-energy CT to relative electron density (RED) via a single linear relationship. The purpose of this study was to investigate the feasibility of this method to obtain RED from virtual monochromatic CT images obtained by the gemstone spectral imaging (GSI) mode with fast-kVp switching.

Methods

A tissue characterization phantom with 13 inserts made of different materials was scanned using the GSI mode on a Discovery CT750 HD. Four sets of virtual monochromatic CT images (60, 77, 100 and 140 keV) were obtained from a single GSI acquisition. When we define Δ HU in terms of the weighting factor for the subtraction α, Δ HU ≡ (1 + α)H - αL (H and L represent the CT values for high and low energy respectively), the relationship between Δ HU and RED is approximated as a linear function, a × Δ HU/1000 + b (a, b = unity). We evaluated the agreement between the determined and nominal RED. We also have investigated reproducibility over short and long time periods.

Results

For the 13 insert materials, the RED determined by monochromatic CT images agreed with the nominal values within 1.1% and the coefficient of determination for this calculation formula was greater than 0.999. The observed reproducibility (1 standard deviation) of calculation error was within 0.5% for all materials.

Conclusions

These findings indicate that virtual monochromatic CT scans at two different energies using GSI mode can provide an accurate method for estimating RED.

【 授权许可】

   
2013 Ogata et al.; licensee BioMed Central Ltd.

【 图 表 】

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