The Effects Of High Dose and Low Dose Protocols In Thorax’s CT Scan Image Quality

Ni Larasati Kartika Sari, Deni Tiko Bahagia, Puji Hartoyo, Dewi Muliyati



The aim of this research was to evaluate the effects of two different dose protocols’ usage on image quality. This research was performed on three different CT Scanners using high dose and low dose protocols of thorax scan. Different exposure parameters were used, depending on each scanner’s setting. GE QA CT Scan phantom was used for image quality assessment.  Image quality measured were CT number accuracy, uniformity and linearity, noise uniformity, spatial resolution and Contrast To Noise Ratio (CNR). CT Scan’s dose index, CTDIvol (Volumetric Computed Tomography Dose Index), was also measured to evaluate how these two protocols work in reducing radiation dose. The result showed that the usage of low dose protocols reduce the CTDIvol value at 85-91% compared to the high dose protocols, meanwhile most of the image quality parameters obtained from both protocols were still considered good. The CT number accuracy, uniformity, linearity and noise uniformity for all CT Scans were all still inside BAPETEN’s (Indonesia National Regulator Agency) threshold. There were 20-23% difference on the spatial resolution value measured from both protocols. The most significant difference came from CNR. The CNR obtained from high dose protocols were 65-93% higher than the one from low dose protocols.   

Keywords: contrast to noise ratio, CTDIvol, CT number, spatial resolution


Penelitian ini mengevaluasi pengaruh penggunanaan protokol dosis tinggi dan protokol dosis rendah terhadap kualitias citra dan dosis khususnya pada pemeriksaan CT Scan thorax. Penelitian ini dilakukan pada 3 sampel CT Scan yang berbeda. Faktor eksposi yang digunakan berbeda untuk tiap scanner, bergantung pada setting yang terdapat pada scanner. Fantom yagdigunakan untuk menilai kualitas citra adalah fantom GE QA CT Scan. Adapun kualitas citra yang diukur adalah keseragaman, akurasi, dan linearitas CT number, keseragaman noise, resolusi spasial, serta Contrast to Noise Ratio (CNR). Sementara dosis radiasi yang diamati adalah CTDIvol (Volumetrik Computed Tomography Dose Index) yang tampil pada konsol. Hasil penelitian ini menunjukkan bahwa penggunaan protokol dosis rendah mampu mengurangi nilai CTDIvol sebesar 85-91% dibanding dengan protokol dosis tinggi, sementara sebagian besar parameter kualitas citra yang diukur masih dinilai baik. Nilai akurasi, keseragaman, dan linearitas CT number  serta keseragaman noise pada protokol dosis tinggi dan dosis rendah, keseluruhannya masih dalam batas ambang BAPETEN. Terdapat perbedaan sebesar 20-23% pada nilai resolusi spasial yang terukur dari  kedua protokol. Nilai CNR pada protokol dosis tinggi lebih baik dari pada protokol dosis rendah, dengan perbedaan yang cukup signifikan, yaitu 65-93%.

Kata kunci: contrast to noise ratio, CTDIvol, CT number, resolusi spasial


contrast to noise ratio,; CTDIvol; CT number; resolusi spasial

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1. Hausleiter J, Meyer T, Hermann F, Hadamitzky M, Krebs M, Gerber T C, McCollough C, Martinoff S, Kastrati A and Schömig A 2009 Estimated radiation dose associated with cardiac CT angiography. J. Am. Med. Assoc, 301 500–7.

2. D. Tack, M. K. Kalra, and P. A. Gevenois. 2012. Radiation Dose from Multidetector CT, Second Edition. Springer-Verlag Berlin Heidelberg, Jerman

3. Smith-Bindman R, Lipson J, Marcus R, et al. 2009. Radiation dose associated with common computed tomography examinations and the associated lifetime attributable risk of cancer. Arch Intern Med, 169: 2078-2086.

4. European Commission, Radiation Protection No 180 Medical Radiation Exposure of the European Population, Publications Office of the European Union, 2015.

5. Dougeni, E., Faulkner, K. and Panayiotakis, G. 2012. A review of patient dose and optimisation methods in adult and paediatric CT scanning. Eur. J. Radiol, 81(4), e665–e683.

6. M. K. Kalra, M. M. Maher, T. L. Toth, R. S. Kamath, E. F. Halpern, and S. Saini. 2004. Comparison of Z-axis automatic tube current modulation technique with fixed tube current CT scanning of abdomen and pelvis. Radiology, vol. 232, no. 2, pp. 347–353.

7. A. R. Kambadakone, P. Prakash, P. F. Hahn, and D. V. Sahani. 2010. Low-dose CT examinations in Crohn’s disease: impact on image quality, diagnostic performance, and radiation dose.American Journal of Roentgenology, vol. 195, no. 1, pp. 78–88.

8. P. D. McLaughlin, K. P. Murphy, S. A. Hayes et al. 2014. Non-contrast CT at comparable dose to an abdominal radiograph in patients with acute renal colic; impact of iterative reconstruction on image quality and diagnostic performance. Insights into Imaging, vol. 5, no. 2, pp. 217–230.

9. K. P. Murphy, L. Crush, M. Twomey et al. 2015. Model-based iterative reconstruction in CT enterography. American Journal of Roentgenology, vol. 205, no. 6, pp. 1173–1181.

10. Ni Larasati Kartika Sari, Merry Suzana, Muzilman Muslim, Dewi Muliyati. 2020. Analysis of the effect of care dose 4D software use on image quality and radiation dose on the CT scan abdomen. Spektra: Jurnal Fisika dan Aplikasinya, volume 5, Issue 1.

11. Syamsidar, Bualkar Abdullah, Syamsir Dewang dan Mulyadin, 2017. Analisis Akurasi dan Keseragaman CT Number dari Citra CT Scan menggunakan Phantom Gammex. Jurnal Pendidikan Fisika Universitas Hasanudin, 2(1) 2356-301X.

12. Mohammad Davoudi, Daryoush Khoramian, Razzagh Abedi-Firouzjah, and Gholamreza Ataei. 2019. Strategy of computed tomography image optimisation in cervical vertebrae and neck soft tissue in emergency patients. Radiation protection dosimetry, 187 (1), 98-102.

13. Kalra MK, Maher MM, Toth TL, et al. 2004. Strategies for CT radiation dose optimization. Radiology, 230:619–28.

14. Richard G. Kavanagh, John O’Grady, Brian W. Carey, Patrick D. McLaughlin, Siobhan B. O’Neill, Michael M. Maher, and Owen J. O’Connor. 2018. Low-Dose Computed Tomography for the Optimization of Radiation Dose Exposure in Patients with Crohn’s Disease. Gastroenterology Research and Practice, Volume 2018, Article ID 1768716, 10 pages.

15. BAPETEN. 2018. Peraturan kepala BAPETEN no. 2 tahun 2018 tentang Uji Keseuaian Pesawat Sinar-X Radiologi Diagnostik dan Konvensional.

16. Bushberg, J.T. 2011. The Essential Physics Of Medical Imaging, Third Edition. Philadelphia, USA.

17. ICRU. 2012. ICRU report 87: Radiation Dose and Image-Quality Assessment in Computed Tomography. Journal of the ICRU Volume 12 No 1, Oxford University Press.

18. Mohamed Bahaaeldin Afifi, A. Abdelrazek, Nashaat Ahmed Deiab, A. I. Abd ElHafez & A. H. El-Farrash. 2020. The effects of CT x-ray tube voltage and current variations on the relative electron density (RED) and CT number conversion curves. Journal of Radiation Research and Applied Sciences, 13:1, 1-11, DOI: 10.1080/16878507.2019.1693176.

19. Brent van der Heyden, Michel Öllers, André Ritter, Frank Verhaegen, Wouter van Elmpt. 2017. Clinical evaluation of a novel CT image reconstruction algorithm for direct dose calculations. Physics and Imaging in Radiation Oncology 2, 11–16

20. E. Seeram, 2016. Computed Tomography Physical Principles, Clinical Applications, and Quality Control, Fourth edition. Saunders.

21. Dennis Mackin, Rachel Ger, Cristina Dodge, Xenia Fave, Pai-Chun Chi1, Lifei Zhang, Jinzhong Yang, Steve Bache, Charles Dodge, A. Kyle Jones & Laurence Court. 2018. Effect of tube current on computed tomography radiomic features. Scientific Reports, 8:2354.

22. Haney A Alsleem and Hussain M Almohiy. 2020. The Feasibility of Contrast-to-Noise Ratio on Measurements to Evaluate CT Image Quality in Terms of Low-Contrast Detailed Detectability. Med. Sci., 8, 26.


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