An investigation and comparison
of effective factors on variations
of Honsfield numbers in CT scanners
Subject Areas :
biophsics
Ameneh Abdollahi Qomi
1
(Master's student, Nuclear Radiomedical Engineering, Qom Branch, Islamic Azad University, Qom, Iran.)
Parviz Zobdeh
2
(Associate Professor, Department of Physics and Radiation Medicine, Qom Branch, Islamic Azad University, Qom, Iran)
Saeed Karim Khani Zandi
3
(Assistant Professor, Radiation Therapy Department, University of Medical Sciences, Qom, Iran)
Received: 2020-06-30
Accepted : 2021-09-10
Published : 2021-12-22
Keywords:
Hounsfield numbers,
CT simulation system,
Computer tomography,
CT quality control,
Electron density,
CT numbers,
Abstract :
Objectives:This study was conducted to evaluate effective factors in variation of amount of Handsfield numbers in different CT scanners, considering the importance of CT number equivalence in diagnostic programs and cancer treatment by radiotherapy. Providing the better functional solutions for CT calibration, improving the quality of diagnostic and therapeutic programs, the emphasis on accepted tolerance and controlling the errors resulted from dose calculated by treatment planning systems were studied.Methods:The process performed on raw data obtained during the calibration procedure on ten CT scanners in different radiotherapy centers in IRAN. This quality control tests performed by a selected approved Iranian company.Results: This research focused on CT Number correctness and accuracy tests section in calibration procedure. The factors influencing the variation of Honsfield numbers in CT scans were evaluated by analyzing the obtained data. Data are compared with other factors that cause to alter Handsfeld CT number and reported in previous researches.Creating an error and changing the numbers of CTs causes change in the CT density curve and ultimately effects on treatment plan and the received patient dose. Therefore, it should minimize the error rate by evaluating the effective factors of the TPS. The main factors affecting on Honsfield numbers are: photon energy, the characteristics of materials in phantoms used for calibration of the systems, physical phantom shape and diameter, patient/phantom position and image reconstruction algorithm.Conclusion: It is strongly recommended that a well-documented assessment program is required to ensure Honsfield numbers changes in the confined range of treatments.
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Bushberg JT & Boone JM. The essential physics of medical imaging. Lippincott Williams & Wilkins; 2011.
Parker R, Hobday PA & Cassell K. The direct use of CT numbers in radiotherapy dosage calculations for inhomogeneous media. Physics in Medicine & Biology. 1979; 24(4): 802.
Grantham KK, Li H, Zhao T & Klein EE. The impact of CT scan energy on range calculation in proton therapy planning. Journal of applied clinical medical physics. 2015; 16(6): 100-9.
Bazalova M, Carrier J-F, Beaulieu L & Verhaegen F. Dual-energy CT-based material extraction for tissue segmentation in Monte Carlo dose calculations. Physics in Medicine & Biology. 2008; 53(9): 2439.
Williamson JF, Li S, Devic S, Whiting BR & Lerma FA. On two‐parameter models of photon cross sections: Application to dual‐energy CT imaging. Medical physics. 2006; 33(11): 4115-29.
Torikoshi M, Tsunoo T, Sasaki M, Endo M, Noda Y, Ohno Y & et al. Electron density measurement with dual-energy x-ray CT using synchrotron radiation. Physics in Medicine & Biology. 2003; 48(5): 673.
Wu V, Podgorsak MB, Tran TA, Malhotra HK & Wang IZ. Dosimetric impact of image artifact from a wide‐bore CT scanner in radiotherapy treatment planning. Medical physics. 2011; 38(7): 4451-63.
Mutic S, Palta JR, Butker EK, Das IJ, Huq MS, Loo LND & et al. Quality assurance for computed‐tomography simulators and the computed‐tomography‐simulation process: report of the AAPM Radiation Therapy Committee Task Group No. 66. Medical physics. 2003; 30(10): 2762-92.
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Van Dyk J, Battista J, Cunningham J, Rider W & Sontag M. On the impact of CT scanning on radiotherapy planning. Computerized tomography. 1980; 4(1): 55-65.
Khan FM & Gibbons JP. Khan's the physics of radiation therapy. Lippincott Williams & Wilkins; 2014.
Asgharizadeh F, Ghannadi Maragheh M, Salimi B & Sedgh Gouya E. Dose rate calculation caused by natural radioactivity in granite samples used as building materials in Iran. ijrsm. 2014; 2(2): 27-30.
Landry G, Reniers B, Granton PV, van Rooijen B, Beaulieu L, Wildberger JE & et al. Extracting atomic numbers and electron densities from a dual source dual energy CT scanner: experiments and a simulation model. Radiotherapy and Oncology. 2011; 100(3): 375-9.
Jaffray DA, Siewerdsen JH, Wong JW & Martinez AA. Flat-panel cone-beam computed tomography for image-guided radiation therapy. International Journal of Radiation Oncology *Biology* Physics. 2002; 53(5): 1337-49.
Yoo S, Yin F-F. Dosimetric feasibility of cone-beam CT-based treatment planning compared to CT-based treatment planning. International Journal of Radiation Oncology *Biology* Physics. 2006; 66(5): 1553-61.
Mahmoudi R, Jabbari N & Khalkhali HR. Energy dependence of measured CT numbers on substituted materials used for CT number calibration of radiotherapy treatment planning systems. PloS one. 2016; 11(7): e0158828.
Rizescu C, Beşliu C & Jipa A. Determination of local density and effective atomic number by the dual-energy computerized tomography method with the <sup> 192 <sup> Ir radioisotope. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. 2001; 465(2): 584-99.
Skrzyński W, Zielińska-Dąbrowska S, Wachowicz M, Ślusarczyk-Kacprzyk W, Kukołowicz PF & Bulski W. Computed tomography as a source of electron density information for radiation treatment planning. Strahlentherapie und Onkologie. 2010; 186(6): 327-33.
Nobah A, Moftah B, Tomic N & Devic S. Influence of electron density spatial distribution and X‐ray beam quality during CT simulation on dose calculation accuracy. Journal of applied clinical medical physics. 2011; 12(3): 80-9.
Lamba R, McGahan JP, Corwin MT, Li C-S, Tran T, Seibert JA & et al. CT Hounsfield numbers of soft tissues on unenhanced abdominal CT scans: variability between two different manufacturers’ MDCT scanners. American Journal of Roentgenology. 2014; 203(5): 1013-20.
Cropp RJ, Seslija P, Tso D & Thakur Y. Scanner and kVp dependence of measured CT numbers in the ACR CT phantom. Journal of applied clinical medical physics. 2013; 14(6): 338-49.
Constantinou C, Harrington JC & DeWerd LA. An electron density calibration phantom for CT‐based treatment planning computers. Medical physics. 1992; 19(2): 325-7.
Heismann B, Leppert J & Stierstorfer K. Density and atomic number measurements with spectral x-ray attenuation method. Journal of applied physics. 2003; 94(3): 2073-9.
Joseph PM & Spital RD. The effects of scatter in x‐ray computed tomography. Medical physics. 1982; 9(4): 464-72.
Davis AT, Palmer AL, Pani S & Nisbet A. Assessment of the variation in CT scanner performance (image quality and Hounsfield units) with scan parameters, for image optimisation in radiotherapy treatment planning. Physica Medica. 2018; 45: 59-64.
Bushberg JT & Boone JM. The essential physics of medical imaging. Lippincott Williams & Wilkins; 2011.
Parker R, Hobday PA & Cassell K. The direct use of CT numbers in radiotherapy dosage calculations for inhomogeneous media. Physics in Medicine & Biology. 1979; 24(4): 802.
Grantham KK, Li H, Zhao T & Klein EE. The impact of CT scan energy on range calculation in proton therapy planning. Journal of applied clinical medical physics. 2015; 16(6): 100-9.
Bazalova M, Carrier J-F, Beaulieu L & Verhaegen F. Dual-energy CT-based material extraction for tissue segmentation in Monte Carlo dose calculations. Physics in Medicine & Biology. 2008; 53(9): 2439.
Williamson JF, Li S, Devic S, Whiting BR & Lerma FA. On two‐parameter models of photon cross sections: Application to dual‐energy CT imaging. Medical physics. 2006; 33(11): 4115-29.
Torikoshi M, Tsunoo T, Sasaki M, Endo M, Noda Y, Ohno Y & et al. Electron density measurement with dual-energy x-ray CT using synchrotron radiation. Physics in Medicine & Biology. 2003; 48(5): 673.
Wu V, Podgorsak MB, Tran TA, Malhotra HK & Wang IZ. Dosimetric impact of image artifact from a wide‐bore CT scanner in radiotherapy treatment planning. Medical physics. 2011; 38(7): 4451-63.
Mutic S, Palta JR, Butker EK, Das IJ, Huq MS, Loo LND & et al. Quality assurance for computed‐tomography simulators and the computed‐tomography‐simulation process: report of the AAPM Radiation Therapy Committee Task Group No. 66. Medical physics. 2003; 30(10): 2762-92.
