Assessment of Optimal Pitch Ratio in 4D Computed Tomography Images for Reducing Radiation Dose with Sustained Image Quality
Four-dimensional computed tomography (4D CT) images are used to manage the respiratory- induced moving tumour problem. A pitch ratio is the main factor for radiation dose and image quality of 4D CT. Therefore, the purpose of this study was to determine the optimal pitch ratio for 4D CT images in mov...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
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Prince of Songkla University
2016-08-01
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| Series: | Journal of Health Science and Medical Research (JHSMR) |
| Subjects: | |
| Online Access: | https://www.jhsmr.org/index.php/jhsmr/article/view/152 |
| Summary: | Four-dimensional computed tomography (4D CT) images are used to manage the respiratory- induced moving tumour problem. A pitch ratio is the main factor for radiation dose and image quality of 4D CT. Therefore, the purpose of this study was to determine the optimal pitch ratio for 4D CT images in moving target volume that related with respiratory rate. A CT scanner with a Real-time Position ManagementTM system was used. A respiratory phantom was used to simulate tumor motion up to 1 cm in the supero-inferior direction. Four different pitch ratios were compared, recommended by the manufacturer of the CT scanner, average pitch ratio between recommended by the manufacturer and used by hospital, routine use (old pitch ratio from the manufacturer of the CT scanner) and calculated equation, Maximum pitch ratio=Rotation time (s)xBreath rate (breaths/min)/60(seconds/min). Image data sets were acquired with three different respiratory rates 10, 15 and 20 BPM. The raw image data was reconstructed in 4 phases of respiratory binning at 0%, 25%, 50% and 75%. All images in each pitch ratio groups were calculated and analyzed in terms of percent difference of volume and elongation. Image quality was evaluated by 5 radiation oncologists. Additionally, CTDIVOL (Volume CT Dose Index) was measured at different pitch ratios. As a result, the percent difference of volume and elongation of pitch ratio as recommended by the manufacturer were not different (p-value>0.05) compared to the other groups. Image quality between average pitch ratio and the one recommended by the CT manufacturer were not significantly different (p-value>0.05). Also, CTDIVOL decreased with lower pitch ratio. In conclusion, the average pitch ratio was optimal for 4D CT images with the percent difference of volume, elongation and image quality results comparable with the recommended by the CT manufacturer, and decreased dose by 31.3%. |
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| ISSN: | 2586-9981 2630-0559 |