Korean J Radiol.  2015 Jun;16(3):531-540. 10.3348/kjr.2015.16.3.531.

Combined Use of Automatic Tube Voltage Selection and Current Modulation with Iterative Reconstruction for CT Evaluation of Small Hypervascular Hepatocellular Carcinomas: Effect on Lesion Conspicuity and Image Quality

• Lv P
• Liu J
• Zhang R
• Jia Y
• Gao J

• KMID: 2155522
• DOI: http://doi.org/10.3348/kjr.2015.16.3.531

Abstract

OBJECTIVE
To assess the lesion conspicuity and image quality in CT evaluation of small (< or = 3 cm) hepatocellular carcinomas (HCCs) using automatic tube voltage selection (ATVS) and automatic tube current modulation (ATCM) with or without iterative reconstruction.
MATERIALS AND METHODS
One hundred and five patients with 123 HCC lesions were included. Fifty-seven patients were scanned using both ATVS and ATCM and images were reconstructed using either filtered back-projection (FBP) (group A1) or sinogram-affirmed iterative reconstruction (SAFIRE) (group A2). Forty-eight patients were imaged using only ATCM, with a fixed tube potential of 120 kVp and FBP reconstruction (group B). Quantitative parameters (image noise in Hounsfield unit and contrast-to-noise ratio of the aorta, the liver, and the hepatic tumors) and qualitative visual parameters (image noise, overall image quality, and lesion conspicuity as graded on a 5-point scale) were compared among the groups.
RESULTS
Group A2 scanned with the automatically chosen 80 kVp and 100 kVp tube voltages ranked the best in lesion conspicuity and subjective and objective image quality (p values ranging from < 0.001 to 0.004) among the three groups, except for overall image quality between group A2 and group B (p = 0.022). Group A1 showed higher image noise (p = 0.005) but similar lesion conspicuity and overall image quality as compared with group B. The radiation dose in group A was 19% lower than that in group B (p = 0.022).
CONCLUSION
CT scanning with combined use of ATVS and ATCM and image reconstruction with SAFIRE algorithm provides higher lesion conspicuity and better image quality for evaluating small hepatic HCCs with radiation dose reduction.

Keyword

Automatic tube voltage selection; Automatic tube current modulation; Sinogram-affirmed iterative reconstruction; Small hepatocellular carcinoma

MeSH Terms

Adult
Aged
Aged, 80 and over
Algorithms
Carcinoma, Hepatocellular/*radiography
Contrast Media
Female
Fluoroscopy
Humans
Image Enhancement/*methods
Liver Neoplasms/*radiography
Male
Middle Aged
Prospective Studies
Radiation Dosage
Radiographic Image Interpretation, Computer-Assisted/*methods
Tomography, X-Ray Computed/*methods
Young Adult
Contrast Media

Figure

• 

  Fig. 1 Distribution of selected tube voltages in group A according to BMI. BMI = body mass indices

• 

  Fig. 2 Results of quantitative analysis for all lesions with respect to CNRlesion and image noise among three groups. Among three groups, CNRlesion was highest and image noise was lowest in group A2 (p values ranging from < 0.001 to 0.004). Compared with group B, CNRlesion in group A1 was not significantly different (p > 0.05) while image noise in group A1 was significantly higher (p = 0.002). CNR = contrast-to-noise ratio, HU = Hounsfield unit

• 

  Fig. 3 Transverse contrast-enhanced CT images were obtained from 60-year-old man with hepatocellular carcinoma and cirrhosis (BMI, 23.2 kg/m2) (A, B) with combined use of ATVS and ATCM at tube voltage of 100 kVp and from 61-year-old man with hepatocellular carcinoma and cirrhosis using ATCM alone (BMI, 20.6 kg/m2) (C) during LAP. CNR of lesion and mean image noise in group A1 (A), group A2 (B), and group B (C) were as follows: CNR of lesion: 3.60, 4.85, and 4.01; image noise: 10.9, 7.7, and 8.0 HU. ATCM = automatic tube current modulation, ATVS = automatic tube voltage selection, BMI = body mass indices, CNR = contrast-to-noise ratio, HU = Hounsfield unit, LAP = late arterial phase

• 

  Fig. 4 Transverse contrast-enhanced CT images were obtained from 50-year-old woman with hepatocellular carcinoma and cirrhosis (BMI, 21.8 kg/m2) (A, B) with combined use of ATVS and ATCM at tube voltage of 80 kVp and from 56-year-old woman with hepatocellular carcinoma and cirrhosis using ATCM alone (BMI, 23.4 kg/m2) (C) during LAP. CNR of lesion and mean image noise in group A1 (A), group A2 (B), and group B (C) were as follows: CNR of lesion: 1.73, 2.61, and 2.15; image noise: 16.9, 11.9, and 9.9 HU. ATCM = automatic tube current modulation, ATVS = automatic tube voltage selection, BMI = body mass indices, CNR = contrast-to-noise ratio, HU = Hounsfield unit, LAP = late arterial phase

• 

  Fig. 5 Results of qualitative analysis for all lesions in terms of image noise, overall image quality, and lesion conspicuity among three groups. Group A2 showed less image noise, and higher overall image quality and lesion conspicuity than group A1 and group B (p values ranging from < 0.001 to 0.001) except for overall image quality between group A2 and group B (p = 0.022). Group B showed less image noise than group A1 (p < 0.001). There was no significant difference in overall image quality and lesion conspicuity between group A1 and group B (p > 0.05).

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