Sage Journals: Discover world-class research

Abstract

Background

As there is increased concern over the radiation exposure particularly in adolescents and young adults, computed tomography (CT) dose reduction is needed in the diagnosis of acute appendicitis.

Purpose

To evaluate the optimal strength of sinogram affirmed iterative reconstruction (SAFIRE) to obtain the best image quality on a 30-mAs applied low-dose CT (LDCT_30mAs) and to compare the diagnostic performances of the LDCT_30mAs with different SAFIRE strengths with that of the 100-mAs applied LDCT (LDCT_100mAs) for the diagnosis of acute appendicitis.

Material and Methods

A total of 102 consecutive patients (47 men, 55 women; mean age, 41.2 years; range, 15–82 years) with right lower quadrant pain underwent abdominal-pelvic CT, consisting of arterial phase LDCT_100mAs and portal venous phase LDCT_30mAs under a fixed 120 kV. LDCT_30mAs images were reconstructed separately with five strength levels (S1–S5). Two blinded radiologists recorded scores for the subjective image quality of the LDCT_30mAs dataset (S0–S5) and confidence scores for the diagnosis of acute appendicitis on each dataset and LDCT_100mAs. CT image noise was measured for each set.

Results

The study population consisted of 58 patients with confirmed appendicitis and 44 without appendicitis. There was no significant difference in diagnostic performance between LDCT_100mAs and LDCT_30mAs with any strength for both readers (AUC for reader 1, LDCT_30mAs with S0–S5 = 0.97, LDCT_100mAs = 0.93, P = 0.0936; for reader 2, LDCT_30mAs with S0–S5 = 0.96, LDCT_100mAs = 0.97, P = 0.128). The measured noise decreased as the strength increased from S0 to S5 (mean, 20.8 > 17.7 > 15.6 > 13.5 > 11.5 > 9.5, P < 0.0001). However, overall subjective image quality on S3 was better than the other strengths for both readers (S0 < S1 < S2 < S3 > S4 > S5, P < 0.0001).

Conclusion

Although measured noise declined as SAFIRE strength increased, S3 seems optimal for the best subjective image quality on LDCT_30mAs. The diagnostic performance of LDCT_30mAs with any strength is comparable to that of LDCT_100mAs for the diagnosis of acute appendicitis.

Keywords

Iterative reconstruction computed tomography image reconstruction radiation dosage appendicitis

Get full access to this article

View all access options for this article.

References

Buckius

McGrath

Monk

. Changing epidemiology of acute appendicitis in the United States: study period 1993-2008. J Surg Res 2012; 175: 185–190.

Poletti

Platon

De Perrot

. Acute appendicitis: prospective evaluation of a diagnostic algorithm integrating ultrasound and low-dose CT to reduce the need of standard CT. Eur Radiol 2011; 21: 2558–2566.

Brenner

Hall

. Computed tomography: an increasing source of radiation exposure. N Engl J Med 2007; 357: 2277–2284.

Brenner

. Slowing the increase in the population dose resulting from CT scans. Radiat Res 2010; 174: 809–815.

Berrington de González

Mahesh

Kim

. Projected cancer risks from computed tomographic scans performed in the United States in 2007. Arch Intern Med 2009; 169: 2071–2077.

Fefferman

Bomsztyk

Yim

. Appendicitis in children: low-dose CT with a phantom-based simulation technique—initial observations. Radiology 2005; 237: 641–646.

Seo

Lee

Kim

. Diagnosis of acute appendicitis with sliding slab ray-sum interpretation of low-dose unenhanced CT and standard-dose i.v. contrast-enhanced CT scans. Am J Roentgenol 2009; 193: 96–105.

Keyzer

Tack

de Maertelaer

. Acute appendicitis: comparison of low-dose and standard-dose unenhanced multi-detector row CT. Radiology 2004; 232: 164–172.

Keyzer

Cullus

Tack

. MDCT for suspected acute appendicitis in adults: impact of oral and IV contrast media at standard-dose and simulated low-dose techniques. Am J Roentgenol 2009; 193: 1272–1281.

10.

Kim

Lee

Kim

. Acute appendicitis in young adults: low- versus standard-radiation-dose contrast-enhanced abdominal CT for diagnosis. Radiology 2011; 260: 437–445.

11.

Paulson

Coursey

. CT protocols for acute appendicitis: time for change. Am J Roentgenol 2009; 193: 1268–1271.

12.

Baker

Dong

Primak

. Contrast-to-noise ratio and low-contrast object resolution on full- and low-dose MDCT: SAFIRE versus filtered back projection in a low-contrast object phantom and in the liver. Am J Roentgenol 2012; 199: 8–18.

13.

Moscariello

Takx

Schoepf

. 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.

14.

Han

Grant

Garberich

. Assessment of an iterative reconstruction algorithm (SAFIRE) on image quality in pediatric cardiac CT datasets. J Cardiovasc Comput Tomogr 2012; 6: 200–204.

15.

Kalra

Woisetschläger

Dahlström

. Radiation dose reduction with Sinogram Affirmed Iterative Reconstruction technique for abdominal computed tomography. J Comput Assist Tomogr 2012; 36: 339–346.

16.

Kulkarni

Uppot

Eisner

. Radiation dose reduction at multidetector CT with adaptive statistical iterative reconstruction for evaluation of urolithiasis: how low can we go? Radiology 2012; 265: 158–166.

17.

Pickhardt

Lubner

Kim

. Abdominal CT with model-based iterative reconstruction (MBIR): initial results of a prospective trail comparing ultralow-dose with standard-dose imaging. Am J Roentgenol 2012; 199: 1–9.

18.

Booya

Fletcher

Huprich

. Active Crohn disease: CT findings and interobserver agreement for enteric phase CT enterography. Radiology 2006; 241: 787–795.

19.

International Commission on Radiological Protection. 2007 recommendations of the International Commission on Radiological Protection. ICRP Publication 103. Ann ICRP 2007; 37: 1–34.

20.

American Association of Physicists in Medicine (AAPM). Size-specific dose estimates(SSDE) in pediatric and adult body CT examinations. AAPM report no. 204. College Park, MD: AAPM, 2011:1–26.

21.

Bankier

Kressel

. Through the Looking Glass revisited: the need for more meaning and less drama in the reporting of dose and dose reduction in CT. Radiology 2012; 265: 4–8.

22.

EUR 16262. European guidelines on quality criteria for computed tomography. Available at http://www.drs.dk/guidelines/ct/quality/htmlindex.htm (accessed 4 June 2014).

23.

Birnbaum

Wilson

. Appendicitis at the millennium. Radiology 2000; 215: 337–348.

24.

Desai GS, Kambadakone AR, Sahani DV. Performance of low dose abdomen CT images reconstructed with Sinogram Affirmed Iterative Reconstruction (SAFIRE) and Filtered Back Projection (FBP) (abstr SSA06-07). In: 2012 Radiological Society of North America (RSNA) Annual Meeting Program. Chicago, USA, http://rsna2012.rsna.org/search.

25.

Ebersberger

Tricarico

Schoepf

. CT evaluation of coronary artery stents with iterative image reconstruction: improvements in image quality and potential for radiation dose reduction. Eur Radiol 2013; 23: 125–132.

26.

Smith-Bindman

Lipson

Marcus

. Radiation dose associated with common computed tomography examinations and the associated lifetime attributable risk of cancer. Arch Intern Med 2009; 169: 2078–2086.

27.

Kim SH, Baek SH, Yoon JH, et al. Quarter regular dose non-enhanced CT for urinary stone: added value of adaptive statistical iterative reconstruction. Acta Radiol 2013 Nov 20 [Epub ahead of print].

Low-dose CT for patients with clinically suspected acute appendicitis: optimal strength of sinogram affirmed iterative reconstruction for image quality and diagnostic performance