Radiotherapy treatment planning with contrast-enhanced computed tomography: feasibility of dual-energy virtual unenhanced imaging for improved dose calculations

Radiation Oncology

Kazuhiko Ogawa¹  Kenya Murase²  Takeshi Shimazu⁵  Masahiko Koizumi²  Ryota Ogihara³  Hirokazu Mizuno³  Toshiyuki Ogata⁴  Takashi Ueguchi⁶  Sachiko Yamada² 

[1] Department of Radiation Oncology, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan;Department of Medical Physics and Engineering, Osaka University Graduate School of Medicine, 1-7 Yamadaoka, Suita, Osaka 565-0871, Japan;Department of Radiology, Osaka University Hospital, 2-15 Yamadaoka, Suita, Osaka 565-0871, Japan;Kobe Minimally Invasive Cancer Center, 8-5-1 Minatojima-nakamachi, Chuo-ku, Hyogo 650–0046, Kobe, Japan;Department of Traumatology and Acute Critical Medicine, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan;Graduate School of Frontier Biosciences, Osaka University, 1-4 Yamadaoka, Suita, Osaka 565-0871, Japan

关键词: Tin filter;    Dual-source CT;    CT number;    Tissue attenuation;    Iodine contrast agent;    Dose calculation;    Virtual unenhanced CT;    Dual-energy CT;    Radiotherapy treatment planning;   

Others  :  1131980
DOI  :  10.1186/1748-717X-9-168

 received in 2014-03-25, accepted in 2014-07-22,  发布年份 2014

【 摘 要 】

Background

In radiotherapy treatment planning, intravenous administration of an iodine-based contrast agent during computed tomography (CT) improves the accuracy of delineating target volumes. However, increased tissue attenuation resulting from the high atomic number of iodine may result in erroneous dose calculations because the contrast agent is absent during the actual procedure. The purpose of this proof-of-concept study was to present a novel framework to improve the accuracy of dose calculations using dual-energy virtual unenhanced CT in the presence of an iodine-based contrast agent.

Methods

Simple phantom experiments were designed to assess the feasibility of the proposed concept. By utilizing a “second-generation” dual-source CT scanner equipped with a tin filter for improved spectral separation, four CT datasets were obtained using both a water phantom and an iodine phantom: “true unenhanced” images with attenuation values of 2 ± 11 Hounsfield Units (HU), “enhanced” images with attenuation values of 274 ± 23 HU, and two series of “virtual unenhanced” images synthesized from dual-energy scans of the iodine phantom, each with a different combination of tube voltages. Two series of virtual unenhanced images demonstrated attenuation values of 12 ± 29 HU (with 80 kVp/140 kVp) and 34 ± 10 HU (with 100 kVp/140 kVp) after removing the iodine component from the contrast-enhanced images. Dose distributions of the single photon beams calculated from the enhanced images and two series of virtual unenhanced images were compared to those from true unenhanced images as a reference.

Results

The dose distributions obtained from both series of virtual unenhanced images were almost equivalent to that from the true unenhanced images, whereas the dose distribution obtained from the enhanced images indicated increased beam attenuation caused by the high attenuation characteristics of iodine. Compared to the reference dose distribution from the true unenhanced images, the dose distribution pass rates from both series of virtual unenhanced images were greater than 90%, while those from the enhanced images were less than approximately 50–60%.

Conclusions

Dual-energy virtual unenhanced CT improves the accuracy of dose distributions in radiotherapy treatment planning by removing the iodine component from contrast-enhanced images.

【 授权许可】

   
2014 Yamada et al.; licensee BioMed Central Ltd.

【 图 表 】

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