Elsevier

Academic Radiology

Volume 18, Issue 8, August 2011, Pages 991-999
Academic Radiology

Original investigation
A Low Tube Voltage Technique Reduces the Radiation Dose at Retrospective ECG-gated Cardiac Computed Tomography for Anatomical and Functional Analyses

https://doi.org/10.1016/j.acra.2011.03.007Get rights and content

Rationale and Objectives

To investigate the effect of low-tube-voltage technique on a cardiac computed tomography (CT) for coronary arterial and cardiac functional analyses and radiation dose in slim patients.

Materials and Methods

We enrolled 80 patients (52women, 28 men; mean age, 68.7 ± 8.9 years) undergoing retrospective electrocardiogram-gated 64-slice cardiac CT. Forty were subjected to the low (80-kV) and 40 to the standard (120-kV) tube-voltage protocol. Quantitative parameters of the coronary arteries (ie, CT attenuation, image noise, and the contrast-to-noise ratio [CNR]) were calculated, as were the effective radiation dose and the figure of merit (FOM). Each coronary artery segment was visually evaluated using a 5-point scale. Cardiac function calculated by using low-tube-voltage cardiac CT was compared with that on echocardiographs.

Results

CT attenuation and image noise were significantly higher at 80- than 120-kV (P < .01). CNR of the left and right coronary artery was 18.4 ± 3.8 and 18.5 ± 3.3, respectively, at 80 kV; these values were 19.7 ± 2.7 and 19.8 ± 2.8 at 120 kV; the difference was not significant. The estimated effective radiation dose was significantly lower at 80 than 120 kV (6.3 ± 0.6 vs. 13.9 ± 1.1 mSv, P < .01) and FOM was significantly higher at 80 than 120 kV (P < .01). At visual assessment, 99% of the coronary segments were diagnostic quality; the two protocols did not differ significantly. We observed a strong correlation and good agreement between low-tube-voltage cardiac CT and echocardiography for cardiac functional analyses.

Conclusion

Low-tube-voltage cardiac CT significantly reduced the radiation dose by approximately 55% in slim patients while maintaining anatomical image quality and accuracy of cardiac functional analysis.

Section snippets

Materials and methods

This study was approved by our institutional review board; informed consent was obtained from all patients who underwent cardiac CT.

Results

The patient characteristics are summarized in Table 1. There was no significant difference in the age (P = .71), gender distribution (P = .64), body weight (P = .45), BMI (P = .39), and heart rate (P = .08) between the two protocol groups.

Discussion

Retrospective ECG-gated cardiac CT has emerged as a useful noninvasive diagnostic imaging modality not only for the assessment of coronary arteries but also of cardiac motion in three dimensions 2, 17. However, the risk of cancer associated with ionizing radiation in patients undergoing repeat CT studies has raised serious concerns (18) and a low-tube-voltage technique may minimize this disadvantage.

Reducing the tube voltage offers the advantages of higher vascular enhancement at a reduced

References (32)

  • Y. Nakayama et al.

    Abdominal CT with low tube voltage: preliminary observations about radiation dose, contrast enhancement, image quality, and noise

    Radiology

    (2005)
  • F. Cademartiri et al.

    Intravenous contrast material administration at 16-detector row helical CT coronary angiography: test bolus versus bolus-tracking technique

    Radiology

    (2004)
  • W.G. Austen et al.

    A reporting system on patients evaluated for coronary artery disease. Report of the ad hoc Committee for Grading of Coronary Artery Disease, Council on Cardiovascular Surgery, American Heart Association

    Circulation

    (1975)
  • E. Samei et al.

    A framework for optimising the radiographic technique in digital X-ray imaging

    Radiat Prot Dosim

    (2005)
  • J.M. Bland et al.

    Statistical methods for assessing agreement between two methods of clinical measurement

    Lancet

    (1986)
  • Cited by (0)

    View full text