Korean J Radiol.  2009 Jun;10(3):235-243. 10.3348/kjr.2009.10.3.235.

The Image Quality and Radiation Dose of 100-kVp versus 120-kVp ECG-Gated 16-Slice CT Coronary Angiography

• Park EA
• Lee W
• Kang JH
• Yin YH
• Chung JW
• Park JH

• KMID: 1779450
• DOI: http://doi.org/10.3348/kjr.2009.10.3.235

Abstract

OBJECTIVE
This study was conducted to assess the feasibility of performing 100-kVp electrocardiogram (ECG)-gated coronary CT angiography, as compared to 120-kVp ECG-gated coronary CT angiography. MATERIALS AND METHODS: We retrospectively evaluated one hundred eighty five gender- and body mass index-matched 16-slice coronary CT sets of data, which were obtained using either 100 kVp and 620 effective mAs or 120 kVp and 500 effective mAs. The density measurements (image noise, vessel density, signal-to-noise ratio [SNR] and contrast-to-noise ratio [CNR]) and the estimated radiation dose were calculated. As a preference test, two image readers were independently asked to choose one image from each pair of images. The results of both protocols were compared using the paired t-test or the Wilcoxon signed rank test. RESULTS: The 100-kVp images showed significantly more noise and a significantly higher vessel density than did the 120-kVp images. There were no significant differences in the SNR and CNR. The estimated reduction of the radiation dose for the 100-kVp protocol was 24%; 7.8 +/- 0.4 mSV for 100-kVp and 10.1 +/- 1.0 mSV for 120-kVp (p < 0.001). The readers preferred the 100-kVp images for reading (reader 1, p = 0.01; reader 2, p = 0.06), with their preferences being stronger when the subject's body mass index was less than 25. CONCLUSION: Reducing the tube kilovoltage from 120 to 100 kVp allows a significant reduction of the radiation dose without a significant change in the SNR and the CNR.

Keyword

Cardiac CT; Low kVp; Radiation dose

MeSH Terms

Adult
Aged
Aged, 80 and over
Contrast Media/administration & dosage
Coronary Angiography/*methods
Electrocardiography/*methods
Feasibility Studies
Female
Humans
Iohexol/administration & dosage/analogs & derivatives
Male
Middle Aged
Observer Variation
*Radiation Dosage
Radiographic Image Enhancement/methods
Retrospective Studies
Tomography, X-Ray Computed/*methods

Figure

• 

  Fig. 1 Scatterplots of subject BMI versus measurement parameters with two protocols. A. Scatterplot of subject BMI versus attenuation of sinus Valsalva (r2 = 0.067 for 100-kVp protocol and r2 = 0.148 for 120-kVp protocol). B. Scatterplot of subject BMI versus image noise (r2 = 0.377 for 100-kVp protocol and r2 = 0.38 for 120-kVp protocol). C. Scatterplot of subject BMI versus SNR (r2 = 0.377 for 100-kVp protocol and r2 =0.413 for 120-kVp protocol). D. Scatterplot of subject BMI versus CNR (r2 = 0.280 for 100-kVp protocol and r2 = 0.331 for 120-kVp protocol). Solid line (-) and dotted line (---) represent monoexponential fit for 100-kVp and 120-kVp protocol, respectively. BMI = body mass index, SNR = signal-to-noise ratio, CNR = contrast-to-noise ratio, ○ = 100-kVp protocol, △ = 120-kVp protocol

• 

  Fig. 2 Results of subjective image-quality assessment of 185 paired 1-mm thick transverse images for both reviewers. Numbers on columns represent percentage of preferred image numbers. A. Results for less image noise. B. Results for better image contrast. C. Results for preference of reading.

• 

  Fig. 3 Paired transverse postcontrast CT images of subjects with BMI 27.3 and window width and level of 1,200 HU and 300 HU, respectively. A. 1-mm thick transverse image obtained at 100 kVp and 620 mAs in 78-year-old man with noise level of 25.7 HU on pre-contrast image. B. 1-mm thick transverse obtained at 120 kVp and 500 mAs in 62-year-old man with noise level of 22.9 HU on pre-contrast image. Objectively measured image noise was 43.4 HU for 100-kVp image (A) and 31.2 HU for 120-kVp image (B). However, subjective noise level between both images was considered to be equal. Mean attenuation of sinus Valsalva was 583 HU and 319 HU, respectively. Readers chose 100-kVp image for higher image contrast and preference of reading. Image quality score was 4 for 100-kVp image and 3 for 120-kVp image. Estimated effective radiation doses were 7.74 and 9.62 mSv, respectively.

Reference

1. Ghersin E, Litmanovich D, Dragu R, Rispler S, Lessick J, Ofer A, et al. 16-MDCT coronary angiography versus invasive coronary angiography in acute chest pain syndrome: a blinded prospective study. AJR Am J Roentgenol. 2006. 186:177–184.

2. Haberl R, Tittus J, Böhme E, Czernik A, Richartz BM, Buck J, et al. Multislice spiral computed tomographic angiography of coronary arteries in patients with suspected coronary artery disease: an effective filter before catheter angiography? Am Heart J. 2005. 149:1112–1119.

3. Abada HT, Larchez C, Daoud B, Sigal-Cinqualbre A, Paul JF. MDCT of the coronary arteries: feasibility of low-dose CT with ECG-pulsed tube current modulation to reduce radiation dose. AJR Am J Roentgenol. 2006. 186:S387–S390.

4. Hausleiter J, Meyer T, Hadamitzky M, Huber E, Zankl M, Martinoff S, et al. Radiation dose estimates from cardiac multislice computed tomography in daily practice: impact of different scanning protocols on effective dose estimates. Circulation. 2006. 113:1305–1310.

5. d'Agostino AG, Remy-Jardin M, Khalil C, Delannoy-Deken V, Flohr T, Duhamel A, et al. Low-dose ECG-gated 64-slices helical CT angiography of the chest: evaluation of image quality in 105 patients. Eur Radiol. 2006. 16:2137–2146.

6. Hohl C, Mühlenbruch G, Wildberger JE, Leidecker C, Süss C, Schmidt T, et al. Estimation of radiation exposure in low-dose multislice computed tomography of the heart and comparison with a calculation program. Eur Radiol. 2006. 16:1841–1846.

7. Paul JF, Abada HT. Strategies for reduction of radiation dose in cardiac multislice CT. Eur Radiol. 2007. 17:2028–2037.

8. Jakobs TF, Becker CR, Ohnesorge B, Flohr T, Suess C, Schoepf UJ, et al. Multislice helical CT of the heart with retrospective ECG gating: reduction of radiation exposure by ECG-controlled tube current modulation. Eur Radiol. 2002. 12:1081–1086.

9. Hsieh J, Londt J, Vass M, Li J, Tang X, Okerlund D. Step-and-shoot data acquisition and reconstruction for cardiac x-ray computed tomography. Med Phys. 2006. 33:4236–4248.

10. McCollough CH, Primak AN, Saba O, Bruder H, Stierstorfer K, Raupach R, et al. Dose performance of a 64-channel dual-source CT scanner. Radiology. 2007. 243:775–784.

11. Earls JP, Berman EL, Urban BA, Curry CA, Lane JL, Jennings RS, et al. Prospectively gated transverse coronary CT angiography versus retrospectively gated helical technique: improved image quality and reduced radiation dose. Radiology. 2008. 246:742–753.

12. Johnson TR, Nikolaou K, Wintersperger BJ, Leber AW, von Ziegler F, Rist C, et al. Dual-source CT cardiac imaging: initial experience. Eur Radiol. 2006. 16:1409–1415.

13. Kalender WA, Wolf H, Suess C, Gies M, Greess H, Bautz WA. Dose reduction in CT by on-line tube current control: principles and validation on phantoms and cadavers. Eur Radiol. 1999. 9:323–328.

14. Schoenhagen P. Back to the future: coronary CT angiography using prospective ECG triggering. Eur Heart J. 2008. 29:153–154.

15. Stolzmann P, Leschka S, Scheffel H, Krauss T, Desbiolles L, Plass A, et al. Dual-source CT in step-and-shoot mode: noninvasive coronary angiography with low radiation dose. Radiology. 2008. 249:71–80.

16. Stolzmann P, Scheffel H, Schertler T, Frauenfelder T, Leschka S, Husmann L, et al. Radiation dose estimates in dual-source computed tomography coronary angiography. Eur Radiol. 2008. 18:592–599.

17. Heyer CM, Mohr PS, Lemburg SP, Peters SA, Nicolas V. Image quality and radiation exposure at pulmonary CT angiography with 100- or 120-kVp protocol: prospective randomized study. Radiology. 2007. 245:577–583.

18. Sigal-Cinqualbre AB, Hennequin R, Abada HT, Chen X, Paul JF. Low-kilovoltage multi-detector row chest CT in adults: feasibility and effect on image quality and iodine dose. Radiology. 2004. 231:169–174.

19. Wintersperger B, Jakobs T, Herzog P, Schaller S, Nikolaou K, Suess C, et al. Aorto-iliac multidetector-row CT angiography with low kV settings: improved vessel enhancement and simultaneous reduction of radiation dose. Eur Radiol. 2005. 15:334–341.

20. Schueller-Weidekamm C, Schaefer-Prokop CM, Weber M, Herold CJ, Prokop M. CT angiography of pulmonary arteries to detect pulmonary embolism: improvement of vascular enhancement with low kilovoltage settings. Radiology. 2006. 241:899–907.

21. Jung B, Mahnken AH, Stargardt A, Simon J, Flohr TG, Schaller S, et al. Individually weight-adapted examination protocol in retrospectively ECG-gated MSCT of the heart. Eur Radiol. 2003. 13:2560–2566.

22. Huda W, Scalzetti EM, Levin G. Technique factors and image quality as functions of patient weight at abdominal CT. Radiology. 2000. 217:430–435.

23. Kalra MK, Maher MM, Toth TL, Hamberg LM, Blake MA, Shepard JA, et al. Strategies for CT radiation dose optimization. Radiology. 2004. 230:619–628.

24. Nakayama Y, Awai K, Funama Y, Liu D, Nakaura T, Tamura Y, et al. Lower tube voltage reduces contrast material and radiation doses on 16-MDCT aortography. AJR Am J Roentgenol. 2006. 187:W490–W497.