Kosin Med J.  2017 Jun;32(1):47-57. 10.7180/kmj.2017.32.1.47.

Performance of Half-dose Chest Computed Tomography in Lung Malignancy Using an Iterative Reconstruction Technique

• Kang H
• Park JG
• Park SK
• Kim BS
• Lee KN
• Oh KS

• KMID: 2384833
• DOI: http://doi.org/10.7180/kmj.2017.32.1.47

Abstract

OBJECTIVES
The purpose of this study was to evaluate the performance of half-dose chest CT using an iterative reconstruction technique in patients with lung malignancies.
METHODS
The Dual-source CT scans were obtained and half-dose datasets were reconstructed with 5 different strengths in 38 adults with lung malignancies. Two radiologists graded subjective image quality; noise, contrast and sharpness at the central/peripheral lung, mediastinum and chest wall of the reconstructed half-dose images, compared with those of standard-dose images, using a three-point scale. A lesion assessment; lesion conspicuity and diagnostic confidence, was also performed. The quantitative image noises; contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR) were measured and compared with those of standard-dose images.
RESULTS
The subjective image noise in the half-dose images was less than that of the standard-dose images. The contrast in strengths 2 to 5 was superior, the sharpness of the lung parenchyma in strengths 3 to 5 was inferior, and the CNR/SNR in all strengths were higher than those of standard-dose images (P < 0.05). The improvement of subjective image noise and contrast, the decrease in sharpness, were correlated with strength level (P < 0.05). The lesion conspicuity in half-dose images of strengths 4 and 5 was decreased. The diagnostic confidence of the half-dose images of all strengths was comparable to that of the standard-dose images (P < 0.05).
CONCLUSIONS
Half-dose chest CT images using an iterative reconstruction technique show decreased image noise, increased contrast, and diagnostic confidence comparable to standard-dose images. Images reconstructed with strength 2 and 3 appear to be the optimal choice in clinical practice.

Keyword

Chest CT; Low-dose CT; Noise reduction; Reconstruction technique; SAFIRE

MeSH Terms

Adult
Dataset
Humans
Lung*
Mediastinum
Noise
Signal-To-Noise Ratio
Thoracic Wall
Thorax*
Tomography, X-Ray Computed

Figure

• 

  Fig. 1 52-year-old woman with stomach cancer. The reconstructed half-dose CT images with 5 strengths (b, strength 1; c, strength 2; d, strength 3; e, strength 4; f, strength 5) show decreased image noise in the aorta and mediastinal fat compared to the standard-dose image (a). Image noise was inversely correlated with strength.

• 

  Fig. 2 53-year-old woman with rectal cancer. The reconstructed half-dose CT images with strength 3, 4 and 5 (d, e and f) show poor visualization of the small vascular structures in the peripheral 2 cm of the lung compared to the standard-dose image (a). Image sharpness was inversely correlated with strength (b, strength 1; c, strength 2; d, strength 3; e, strength 4; f, strength 5). However, the conspicuity of the small metastatic pulmonary nodules is comparable to the standard-dose image.

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