Korean J Radiol.  2013 Dec;14(6):886-893. 10.3348/kjr.2013.14.6.886.

Radiation Dose Reduction via Sinogram Affirmed Iterative Reconstruction and Automatic Tube Voltage Modulation (CARE kV) in Abdominal CT

• Shin HJ
• Chung YE
• Lee YH
• Choi JY
• Park MS
• Kim MJ
• Kim KW

• KMID: 1711454
• DOI: http://doi.org/10.3348/kjr.2013.14.6.886

Abstract

OBJECTIVE
To evaluate the feasibility of sinogram-affirmed iterative reconstruction (SAFIRE) and automated kV modulation (CARE kV) in reducing radiation dose without increasing image noise for abdominal CT examination.
MATERIALS AND METHODS
This retrospective study included 77 patients who received CT imaging with an application of CARE kV with or without SAFIRE and who had comparable previous CT images obtained without CARE kV or SAFIRE, using the standard dose (i.e., reference mAs of 240) on an identical CT scanner and reconstructed with filtered back projection (FBP) within 1 year. Patients were divided into two groups: group A (33 patients, CT scanned with CARE kV); and group B (44 patients, scanned after reducing the reference mAs from 240 to 170 and applying both CARE kV and SAFIRE). CT number, image noise for four organs and radiation dose were compared among the two groups.
RESULTS
Image noise increased after CARE kV application (p < 0.001) and significantly decreased as SAFIRE strength increased (p < 0.001). Image noise with reduced-mAs scan (170 mAs) in group B became similar to that of standard-dose FBP images after applying CARE kV and SAFIRE strengths of 3 or 4 when measured in the aorta, liver or muscle (p > or = 0.108). Effective doses decreased by 19.4% and 41.3% for groups A and B, respectively (all, p < 0.001) after application of CARE kV with or without SAFIRE.
CONCLUSION
Combining CARE kV, reduction of mAs from 240 to 170 mAs and noise reduction by applying SAFIRE strength 3 or 4 reduced the radiation dose by 41.3% without increasing image noise compared with the standard-dose FBP images.

Keyword

Computed tomography; Radiation dose reduction; Iterative reconstruction; Tube voltage modulation

MeSH Terms

Adult
Aged
Aged, 80 and over
*Algorithms
Equipment Design
Female
Humans
Male
Middle Aged
Multidetector Computed Tomography/adverse effects/*instrumentation
Radiation Dosage
Radiation Injuries/etiology/*prevention & control
Radiographic Image Interpretation, Computer-Assisted/*methods
Radiography, Abdominal/adverse effects/*methods
Retrospective Studies

Figure

• 

  Fig. 1 Mean CT number of four different tissues in 44 patients with different SAFIRE strengths and previous CT scans (group B). Hounsfield units for different SAFIRE strengths (0 to 5) show no significant difference for aorta (p = 0.999), liver (p = 0.995), muscle (p = 0.984) and fat (p = 0.929). Compared to prior CTs, CT numbers were significantly increased due to application of CARE kV (i.e., 100 kVp instead of 120 kVp) for aorta (23.8%, p < 0.001), liver (18.6%, p < 0.001) and muscle (10.0%, p < 0.001) and were increased for fat (10.9%, p < 0.001). SAFIRE = sinogram-affirmed iterative reconstruction

• 

  Fig. 2 Forty-three-year-old male with small hepatic cysts. A. Image scanned with 120 kVp and reference mAs of 240 and reconstructed with FBP, resulting in effective dose 8.69 mSv. B, C and D. CT scan obtained 2 months later with CARE kV (i.e., 100 kVp) and 30% reduced reference mAs of 170, resulting in effective dose of 4.74 mSv (45.5% dose reduction) and reconstructed without application of SAFIRE (i.e., use of FBP); (B) and with SAFIRE strengths of 3 (C) and 5 (D). Image noise was 7 HU (A), 12 HU (B), 8.7 (C) and 4.8 (D), respectively. FBP = filtered back projection, SAFIRE = sinogram-affirmed iterative reconstruction, HU = Hounsfield Unit

Reference

1. Winklehner A, Goetti R, Baumueller S, Karlo C, Schmidt B, Raupach R, et al. Automated attenuation-based tube potential selection for thoracoabdominal computed tomography angiography: improved dose effectiveness. Invest Radiol. 2011; 46:767–773.

2. Hart D, Wall BF. Radiation exposure of the UK population from medical and dental X-ray Examinations. NRPB-W4. Chilton: NRPB;2002.

3. Hur S, Lee JM, Kim SJ, Park JH, Han JK, Choi BI. 80-kVp CT using Iterative Reconstruction in Image Space algorithm for the detection of hypervascular hepatocellular carcinoma: phantom and initial clinical experience. Korean J Radiol. 2012; 13:152–164.

4. Kambadakone AR, Chaudhary NA, Desai GS, Nguyen DD, Kulkarni NM, Sahani DV. Low-dose MDCT and CT enterography of patients with Crohn disease: feasibility of adaptive statistical iterative reconstruction. AJR Am J Roentgenol. 2011; 196:W743–W752.

5. Brenner DJ, Hall EJ. Computed tomography--an increasing source of radiation exposure. N Engl J Med. 2007; 357:2277–2284.

6. Qi W, Li J, Du X. Method for automatic tube current selection for obtaining a consistent image quality and dose optimization in a cardiac multidetector CT. Korean J Radiol. 2009; 10:568–574.

7. Hwang HJ, Seo JB, Lee JS, Song JW, Kim SS, Lee HJ, et al. Radiation dose reduction of chest CT with iterative reconstruction in image space - Part II: assessment of radiologists' preferences using dual source CT. Korean J Radiol. 2012; 13:720–727.

8. Hwang HJ, Seo JB, Lee JS, Song JW, Kim SS, Lee HJ, et al. Radiation dose reduction of chest CT with iterative reconstruction in image space - Part I: studies on image quality using dual source CT. Korean J Radiol. 2012; 13:711–719.

9. Goo HW. CT radiation dose optimization and estimation: an update for radiologists. Korean J Radiol. 2012; 13:1–11.

10. Moritz JD, Hoffmann B, Sehr D, Keil K, Eggerking J, Groth G, et al. Evaluation of ultra-low dose CT in the diagnosis of pediatric-like fractures using an experimental animal study. Korean J Radiol. 2012; 13:165–173.

11. McCollough CH, Primak AN, Braun N, Kofler J, Yu L, Christner J. Strategies for reducing radiation dose in CT. Radiol Clin North Am. 2009; 47:27–40.

12. Winklehner A, Karlo C, Puippe G, Schmidt B, Flohr T, Goetti R, et al. Raw data-based iterative reconstruction in body CTA: evaluation of radiation dose saving potential. Eur Radiol. 2011; 21:2521–2526.

13. Halliburton SS. Recent technologic advances in multi-detector row cardiac CT. Cardiol Clin. 2009; 27:655–664.

14. Ghetti C, Ortenzia O, Serreli G. CT iterative reconstruction in image space: a phantom study. Phys Med. 2012; 28:161–165.

15. Schindera ST, Diedrichsen L, Müller HC, Rusch O, Marin D, Schmidt B, et al. Iterative reconstruction algorithm for abdominal multidetector CT at different tube voltages: assessment of diagnostic accuracy, image quality, and radiation dose in a phantom study. Radiology. 2011; 260:454–462.

16. Barrett HH, Swindell W. Radiological imaging: the theory of image formation, detection, and processing. New York: Academic Press;1981.

17. The 2007 Recommendations of the International Commission on Radiological Protection. ICRP publication 103. Ann ICRP. 2007; 37:1–332.

18. Office for Official Publications of the European Communities. European guidelines on quality criteria for computed tomography. Luxembourg: Office for Official Publications of the European Communities;1999.

19. Yu L, Bruesewitz MR, Thomas KB, Fletcher JG, Kofler JM, McCollough CH. Optimal tube potential for radiation dose reduction in pediatric CT: principles, clinical implementations, and pitfalls. Radiographics. 2011; 31:835–848.

20. Leipsic J, LaBounty TM, Mancini GB, Heilbron B, Taylor C, Johnson MA, et al. A prospective randomized controlled trial to assess the diagnostic performance of reduced tube voltage for coronary CT angiography. AJR Am J Roentgenol. 2011; 196:801–806.

21. Schindera ST, Nelson RC, Mukundan S Jr, Paulson EK, Jaffe TA, Miller CM, et al. Hypervascular liver tumors: low tube voltage, high tube current multi-detector row CT for enhanced detection--phantom study. Radiology. 2008; 246:125–132.

22. Fleischmann D, Boas FE. Computed tomography--old ideas and new technology. Eur Radiol. 2011; 21:510–517.

23. Mueck FG, Körner M, Scherr MK, Geyer LL, Deak Z, Linsenmaier U, et al. Upgrade to iterative image reconstruction (IR) in abdominal MDCT imaging: a clinical study for detailed parameter optimization beyond vendor recommendations using the adaptive statistical iterative reconstruction environment (ASIR). Rofo. 2012; 184:229–238.

24. Moscariello A, Takx RA, Schoepf UJ, Renker M, Zwerner PL, O'Brien TX, et al. Coronary CT angiography: image quality, diagnostic accuracy, and potential for radiation dose reduction using a novel iterative image reconstruction technique-comparison with traditional filtered back projection. Eur Radiol. 2011; 21:2130–2138.