A Study of Water Phantom Homogeneity from DICOM CT-Images Based on ImageJ
DOI:
https://doi.org/10.21608/jntas.2020.38220.1028Keywords:
Water phantom, CT Number, (HU) distribution, homogeneity, ImageJAbstract
The real data for water phantom have complex variations in the distribution of CT (Computed Tomography) number values for each slice. Thus, the accuracy of dose calculation on a homogeneous medium becomes very important to be reviewed. This study aims to review the distribution of CT numbers (in Hounsfield Units, HU) in a water phantom homogeneity determination. The water phantom was of the IBA dose 1 type, with dimensions of 40 cm x 35 cm x 35 cm. The image dimensions were 500 x 500 mm2 with a 1 mm pixel thickness, and 512 x 512 matrix size at image reconstruction. The overall division of water phantom slices was taken from the z-direction or parallel to the patient table into 441 slices. Water phantom homogeneity determination consisted of scanning procedures and image processing. Based on the analysis of the CT number distribution of all slices, the accepted slices were composed of 350 water and 18 acrylic slices. Furthermore, 42 anomaly slices were identified from the calculation of mean and standard deviation. The ROI (Region of Interest) was also considered, reducing water CT number to 53.06 HU. Based on this study, a method for homogeneity determination from the distribution of CT numbers in water phantom IBA Dose 1 was developed.
References
Brahme, A. (1984): Dosimetric precision requirements in radiation therapy. Acta Radiologica Oncology, 23: 379.
Bushong, S. C. (2000): Computed Tomography: Essentials of Medical Imaging Series. New York: McGraw-Hill Companies.
Dobbs, H. J.; Parker, R. P.; Hodson, N. J.; Hobday, P. and Husband, J. E. (1983): The use of CT in radiotherapy treatment planning. Radiotherapy and Oncology, 1(2): 133.
Dutreix, A. (1984): When and how can we improve precision in radiotherapy? Radiotherapy and Oncology, 2: 275.
Goldman, L. W. (2007): Principles of CT: Radiation dose and image quality. Journal of Nuclear Medicine Technology, 35: 213.
Huizenga, H. and Storchi, P. R. M. (1985): The use of computed tomography number dose calculations for radiation therapy. Acta Radiologica Oncology, 24(6): 509.
Kristine, G.; Caroline, S. and Anne, C. T. M. (2014): How to measure CT image quality: Variations in CT numbers, uniformity and low contrast resolution for a CT quality assurance phantom. European Journal of Medical Physics, 30(4): 521.
Nowik, P.; Bujila, R.; Poludniowski, G. and Fransson, A. (2015): Quality control of CT systems by automated monitoring of key performance indicators: A two-year study. Journal of Applied Clinical Medical Physics, 16(4): 254.
Nuttawan, J. (2004): CT Protocol. Bangkok: Radiology Department of Takshin Hospital.
Papp, J. (2006): Quality Management in the Imaging Sciences (3rd ed.). Missouri: Mosby Elsevier, Inc.
Payne, T. (2001): Fundamental Principles of CT Performance Evaluation. AAPM Summer School, Minneapolis: Abbott Northwestern Hospital.
Rong, Y.; Smilowitz, J.; Tewatia, D. and Tomé, W. A. (2009): Dose calculation on kV cone beam CT images: An investigation of the HU-density conversion stability and dose accuracy using site-specific calibration. Medical Dosimetry: Official Journal of the American Association of Medical Dosimetrists, 35(3): 195.
Sage, D. and Unser, M. (2001): Proceedings of the 2001 IEEE International Conference on Image Processing. Thessaloniki, 3: 298.
Seeram, E. (2001): Computed Tomography: Physical Principles, Clinical Applications, and Quality Control (2nd ed.). Canada: W. B. Saunders Company.
Siewerdsen, J. H.; Uneri, A.; Hernandez, A. M.; Burkett, G. W. and Boone, J. M. (2019): Cone-beam CT dose and imaging performance evaluation with a modular, multipurpose phantom. Medical Physics, 47(2): 467.
Smith, H. J.; Bakke, S. J.; Smevik, B.; Hald, J. K.; Moen, G.; Rudenhed, B. and Abildgaard, A. (1992): Comparison of 12-bit and 8-bit gray scale resolution in MR imaging of the CNS. Acta Radiologica, 33(6): 505.
Veinot, K. G.; Eckerman, K. F. and Hertel, N. E. (2016): Organ and effective dose coefficients for cranial and caudal irradiation geometries: Photons. Radiation Protection Dosimetry, 168(2): 167.
White, D. R. and Constantinou, C. (1982): Anthropomorphic phantom materials. Medical Radiation Physics, 1: 133.
Wong, J. W. and Henkelman, R. M. (1983): A new approach to CT pixel-based photon dose calculations in heterogeneous media. Medical Physics, 10: 199.
Downloads
Published
Issue
Section
License
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.
