ALARA Concept for MDCT Optimization: What is Reasonable, What is Achievable?

  • Denis Tack
Part of the Medical Radiology book series (MEDRAD)


Almost all MDCT scanners are installed with default parameters providing a perfect image quality called “standard”, and deliver the corresponding “standard dose”. Optimization is a process by which a substantial proportion of the standard dose is eliminated without loss in diagnostic performance and/or confidence. The final “optimized dose” reached by this process is not clearly defined in the literature because it varies among manufacturers, scanner generation, and CT users. The ALARA principle implies setting the optimized dose at the lowest reasonable level. In this chapter, we describe possible methods for optimization and propose achievable and reasonable limits for CT scanning of the head, the chest, the abdomen, and the spine.


Iterative Reconstruction Filter Back Projection Automatic Exposure Control Tube Potential Pitch Factor 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


  1. American College of Radiology (ACR) (2008) ACR Appropriateness Criteria®. Clinical Condition: Low Back Pain. Access at
  2. Abdeen N, Chakraborty S, Nguyen T, dos Santos MP, Donaldson M, Heddon G, Schwarz BA (2010) Comparison of image quality and lens dose in helical and sequentially acquired head CT. Clin Radiol 65:868–873PubMedCrossRefGoogle Scholar
  3. Allen BC, Baker ME, Einstein DM, Remer EM, Herts BR, Achkar JP, Davros WJ, Novak E, Obuchowski NA (2010) Effect of altering automatic exposure control settings and quality reference mAs on radiation dose, image quality, and diagnostic efficacy in MDCT enterography of active inflammatory Crohn’s disease. AJR 195:89–100PubMedCrossRefGoogle Scholar
  4. Bankier AA, Schaefer-Prokop C, De Maertelaer V, Tack D, Jaksch P, Klepetko W, Gevenois PA (2007) Air trapping: comparison of standard-dose and simulated low-dose thin-section CT techniques. Radiology 242:898–906PubMedCrossRefGoogle Scholar
  5. Bankier AA, Van Muylem A, Knoop C, Estenne M, Gevenois PA (2001) Bronchiolitis obliterans syndrome in heart-lung transplant recipients: diagnosis with expiratory CT. Radiology 218:533–539PubMedGoogle Scholar
  6. Brenner DJ, Hall EJ (2007) Computed tomography–an increasing source of radiation exposure. N Engl J Med 357:2277–2284PubMedCrossRefGoogle Scholar
  7. Bohy P, de Maertelaer V, Roquigny A, Keyzer C, Tack D, Gevenois PA (2007) Multidetector CT in patients suspected of having lumbar disk herniation: comparison of standard-dose and simulated low-dose techniques. Radiology 244:524–531PubMedCrossRefGoogle Scholar
  8. Deak PD, Smal Y, Kalender WA (2010) Multisection CT protocols: sex- and age-specific conversion factors used to determine effective dose from dose-length product. Radiology 257:158–166PubMedCrossRefGoogle Scholar
  9. Demaerel P, Buelens C, Wilms G, Baert AL (1998) Cranial CT revisited: do we really need contrast enhancement? Eur Radiol 8:1447–1451PubMedCrossRefGoogle Scholar
  10. EMAN European Medical ALARA Network (2011) WG1 :optimization of Patient CT Exposures—synthesis Document 31-03-2011—Page 53–71. Access on line at
  11. Golding SJ (2010) Radiation exposure in CT: what is the professionally responsible approach? Radiology 255:683–685PubMedCrossRefGoogle Scholar
  12. Guimarães LS, Fletcher JG, Harmsen WS, Yu L, Siddiki H, Melton Z, Huprich JE, Hough D, Hartman R, McCollough CH (2010) Appropriate patient selection at abdominal dual-energy CT using 80 kV: relationship between patient size, image noise, and image quality. Radiology 257:732–742PubMedCrossRefGoogle Scholar
  13. Hricak H, Brenner DJ, Adelstein SJ, Frush DP, Hall EJ, Howell RW, McCollough CH, Mettler FA, Pearce MS, Suleiman OH, Thrall JH, Wagner LK (2011) Managing radiation use in medical imaging: a multifaceted challenge. Radiology 258:889–905PubMedCrossRefGoogle Scholar
  14. Huda W, Magill D, He W (2011) CT effective dose per dose length product using ICRP 103 weighting factors. Med Phys 38:1261–1265PubMedCrossRefGoogle Scholar
  15. Jaffe TA (2009) Reply. AJR 192:W141–W141CrossRefGoogle Scholar
  16. Kambadakone AR, Prakash P, Hahn PF, Sahani DV (2010) Low-dose CT examinations in Crohn’s disease: impact on image quality, diagnostic performance, and radiation dose. AJR 195:78–88PubMedCrossRefGoogle Scholar
  17. Keyzer C, Tack D, De Maertelaer V, Bohy P, Gevenois PA, Van Gansbeke D (2004) Acute appendicitis: comparison of low-dose and standard-dose unenhanced multi-detector row CT. Radiology 232:164–172PubMedCrossRefGoogle Scholar
  18. Keyzer C, Cullus P, Tack D, De MV, Bohy P, Gevenois PA (2009) MDCT for suspected acute appendicitis in adults: impact of oral and IV contrast media at standard-dose and simulated low-dose techniques. AJR 193:1272–1281PubMedCrossRefGoogle Scholar
  19. Leng S, Yu L, McCollough CH (2010) Radiation dose reduction at CT enterography: how low can we go while preserving diagnostic accuracy? AJR 195:76–77PubMedCrossRefGoogle Scholar
  20. Meeson S, Alvey CM, Golding SJ (2010) The in vivo relationship between cross-sectional area and CT dose index in abdominal multidetector CT with automatic exposure control. J Radiol Prot 30:139–147PubMedCrossRefGoogle Scholar
  21. National Lung Screening Trial Research Team (2010) The national lung screening trial: overview and study design. Radiology 258:243–253Google Scholar
  22. Raissaki M, Perisinakis K, Damilakis J, Gourtsoyiannis N (2010) Eye-lens bismuth shielding in paediatric head CT: artefact evaluation and reduction. Pediatr Radiol 40:1748–1754PubMedCrossRefGoogle Scholar
  23. Remy-Jardin M, Remy J, Wattinne L, Giraud F (1992) Central pulmonary thromboembolism: diagnosis with spiral volumetric CT with the single-breath-hold technique–comparison with pulmonary angiography. Radiology 185:381–387PubMedGoogle Scholar
  24. Remy–Jardin M, Remy J, Deschildre F, Artaud D, Beregi JP, Hossein-Foucher C, Marchandise X, Duhamel A (1996) Diagnosis of pulmonary embolism with spiral CT: comparison with pulmonary angiography and scintigraphy. Radiology 200:699–706PubMedGoogle Scholar
  25. Smith-Bindman R (2010) Is computed tomography safe? N Engl J Med 363:1–4PubMedCrossRefGoogle Scholar
  26. O’Connor OJ, Vandeleur M, McGarrigle AM, Moore N, McWilliams SR, McSweeney SE, O’Neill M, Ni Chroinin M, Maher MM (2010) Development of low-dose protocols for thin-section CT assessment of cystic fibrosis in pediatric patients. Radiology 257:820–829PubMedCrossRefGoogle Scholar
  27. Schindera ST, Graca P, Patak MA, Abderhalden S, von Allmen G, Vock P, Szucs-Farkas Z (2009) Thoracoabdominal-aortoiliac multidetector-row CT angiography at 80 and 100 kVp: assessment of image quality and radiation dose. Invest Radiol 44:650–655PubMedCrossRefGoogle Scholar
  28. Schueller-Weidekamm C, Schaefer-Prokop CM, Weber M, Herold CJ, Prokop M (2006) CT angiography of pulmonary arteries to detect pulmonary embolism: improvement of vascular enhancement with low kilovoltage settings. Radiology 241:899–907PubMedCrossRefGoogle Scholar
  29. Sigal-Cinqualbre AB, Hennequin R, Abada HT et al (2004) Low-kilovoltage multi-detector row chest CT in adults: feasibility and effect on image quality and iodine dose. Radiology 231:169–174PubMedCrossRefGoogle Scholar
  30. Singh S, Kalra MK, Hsieh J, Licato PE, Do S, Pien HH, Blake MA (2010) Abdominal CT: comparison of adaptive statistical iterative and filtered back projection reconstruction techniques. Radiology 257:373–383PubMedCrossRefGoogle Scholar
  31. Singh S, Kalra MK, Gilman MD, Hsieh J, Pien HH, Digumarthy SR, Shepard JA (2011) Adaptive statistical iterative reconstruction technique for radiation dose reduction in chest CT: a pilot study. Radiology 259:565–573PubMedCrossRefGoogle Scholar
  32. Szucs-Farkas Z, Strautz T, Patak MA, Kurmann L, Vock P, Schindera ST (2009a) Is body weight the most appropriate criterion to select patients eligible for low-dose pulmonary CT angiography? Analysis of objective and subjective image quality at 80 kVp in 100 patients. Eur Radiol 19:1914–1922PubMedCrossRefGoogle Scholar
  33. Szucs-Farkas Z, Schaller C, Bensler S, Patak MA, Vock P, Schindera ST (2009b) Detection of pulmonary emboli with CT angiography at reduced radiation exposure and contrast material volume: comparison of 80 kVp and 120 kVp protocols in a matched cohort. Invest Radiol 44:793–799PubMedCrossRefGoogle Scholar
  34. Tang Y, Sampson B, Pack S, Shah K, Yon Um S, Wang D, Wang T, Prinz M (2011) Ethnic differences in out-of-hospital fatal pulmonary embolism. Circulation 123:2219–2225PubMedCrossRefGoogle Scholar
  35. Tack D, Gevenois PA (2009) Body MDCT at 140 kV. AJR 192:W139–W140PubMedCrossRefGoogle Scholar
  36. Tack D, Jahnen A, Kohler S, Harpes N, Back C (2011) Clinical audit on optimization of radiation dose from mdct: effect on diagnostic reference levels for brain, sinus, cervical spine, chest, abdomen-pelvis, and lumbar spine examinations and on nationwide collective effective dose. ECR 2011, C-0066. Accessd on 13 June 2011,
  37. Tsapaki V, Aldrich JE, Sharma R, Staniszewska MA, Krisanachinda A, Rehani M, Hufton A, Triantopoulou C, Maniatis PN, Papailiou J, Prokop M (2006) Dose reduction in CT while maintaining diagnostic confidence: diagnostic reference levels at routine head, chest, and abdominal CT–IAEA-coordinated research project. Radiology 240:828–834PubMedCrossRefGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2011

Authors and Affiliations

  1. 1.Department of RadiologyRHMS Clinique Louis CatyBaudourBelgium

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