Comparison of Image Qualities of 80 kVp and 120 kVp CT Venography Using Model-Based Iterative Reconstruction at Same Radiation Dose

Hyun Jung Baek; Ki Seok Choo; Kyung Jin Nam; Jae-Yeon Hwang; Ji Won Lee; Jin You Kim; Hyuk Jae Jung

doi:10.3348/jksr.2018.78.4.235

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Baek, Choo, Nam, Hwang, Lee, Kim, and Jung: Comparison of Image Qualities of 80 kVp and 120 kVp CT Venography Using Model-Based Iterative Reconstruction at Same Radiation Dose

Original Article

J Korean Soc Radiol 2018;78(4):235-241.

Published online: 20 January 2018

DOI: https://doi.org/10.3348/jksr.2018.78.4.235

Comparison of Image Qualities of 80 kVp and 120 kVp CT Venography Using Model-Based Iterative Reconstruction at Same Radiation Dose

Hyun Jung Baek, MD¹, Ki Seok Choo, MD^1,^∗, Kyung Jin Nam, MD¹, Jae-Yeon Hwang, MD¹, Ji Won Lee, MD², Jin You Kim, MD², Hyuk Jae Jung, MD³

¹Department of Radiology, Research Institute for Convergence of Biomedical Science and Technology, Pusan National University Yangsan Hospital, Busan, Korea

²Department of Radiology, Pusan National University Hospital, Busan, Korea

³Department of Vascular Surgery, Pusan National University Yangsan Hospital, Pusan National University School of Medicine, Yangsan, Korea

^∗Corresponding author: Ki Seok Choo, MD Department of Radiology, Research Institute for Convergence of Biomedical Science and Technology, Pusan National University Yangsan Hospital, Pusan National University School of Medicine, 20 Geumo-ro, Mulgeum-eup, Yangsan 50612, Korea. Tel. 82-55-360-1840 Fax. 82-55-360-1848 E-mail: kschoo0618@naver.com

Received 8 June 2017 Revised 25 July 2017 Accepted 18 August 2017

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Purpose

To compare image qualities of 80 kVp CT venography (CTV) and 120 kVp

Materials and Methods

Sixty-nine patients that underwent CTV using 80 kVp (36 patients, group 1) or 120 kVp (33 patients, group 2) with MBIR at the same radiation dose were enrolled, and objective and subjective image qualities were assessed independently by two radiologists.

Results

Mean vascular enhancement and contrast-to-noise ratio were significantly higher in group 1 than in group 2 for inferior vena cavas, femoral veins, and popliteal veins (p < 0.001), and there was significantly lower objective image noise in group 1 (p < 0.001). Subjective analysis revealed image quality was significantly higher in group 1 and image noise was significantly higher in group 2 (p < 0.001). Mean dose-length products was not significantly lower in group 1 (356.1 ± 153.7 mGy cm) than in group 2 (370.1 ± 77.1 mGy cm) (p = 0.635).

Conclusion

CTV at 80 kVp with MBIR is a better protocol than CTV at 120 kVp with MBIR at the same radiation dose.

Keywords: Index terms Radiation Dosage Multidetector Computed Tomograph Lower Extremity Veins

References

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Fig. 1.

Comparison of vascular enhancement (mean) and image noise (SD). (A) 60-year-old female patient that underwent CTV at 80 kVp, and (B) 79-year-old female patient that underwent CTV at 120 kVp. The 80 kVp images showing better objective vascular enhancement, and lower image noise levels. The contrast-to-noise ratio in (A) was higher than in (B). (A) IVC-7.6, FV-6.7, PopV-7.7, (B) IVC-3.3, FV-3.9, PopV-3.3. CTV = CT venography, FV = femoral vein, IVC = inferior vena cava, PopV = popliteal vein, SD = standard deviation

Table 1.

Scales Used for the Subjective Scoring of Image Quality Characteristics

Scale and Score	Description
Image quality
1	Unacceptable, no diagnosis possible
2	Poor, inadequate for diagnosis of the presence or absence of a clot
3	Fair, enhancement sufficient for diagnosis
4	Good, optimal enhancement allowing confident diagnosis of the presence or absence of a clot
5	Excellent, optimal enhancement superior to a score of 4 allowing for confident diagnosis of the presence or absence of a clot
Image noise
1	Optimal, none perceivable
2	Moderate, but sufficient for diagnosis
3	Unacceptable, no diagnosis possible

Table 2.

Cohen Kappa Coefficients of Interobserver Agreements

Characteristics	Level	Kappa
Objective analysis Vascular enhancement
	IVC	0.98
	FV	0.96
	PopV	0.97
Image noise	IVC	0.75
	FV	0.71
	PopV	0.51
^CNR	IVC	0.69
	FV	0.66
	PopV	0.70
Subjective analysis
Image quality		0.64
Image noise		0.65

CNR = contrast-to-noise ratio, FV = femoral vein, IVC = inferior vena cava, PopV = popliteal vein

Table 3.

Patient Characteristics and Radiation Doses

Characteristics	Group 1 (n = 36)	Group 2 (n = 33)	p-Value
Age (mean ± SD, years)	58 ± 13.1	57.5 ± 16.9	0.715
Sex (F:M)	24:12	19:14	0.890
BMI (mean ± SD, kg/m²)	26.7 ± 3.6	25 ± 4.1	0.111
DLP (mean ± SD, mGy cm)	356.1 ± 153.7	370.1 ± 77.1	0.635

BMI = body mass index, DLP = dose-length product, SD = standard deviation

Table 4.

Objective Analysis Results

Characteristics	Level	Group 1	Group 2	p-Value
Vascular enhancement (HU)	IVC	157.2 ± 19.3	111.7 ± 18.8	< 0.001
	FV	154.6 ± 21.2	110.8 ± 15.3	< 0.001
	PopV	154.2 ± 30.4	115.5 ± 15.3	< 0.001
Image noise (HU)	IVC	11.2 ± 1.4	13.5 ± 4.11	< 0.001
	FV	10.1 ± 2.1	12.5 ± 2.6	< 0.001
	PopV	10.4 ± 2.5	12 ± 3.6	< 0.001
CNR	IVC	7 ± 2.8	5.2 ± 1.7	< 0.001
	FV	6.8 ± 2.8	5.2 ± 1.7	< 0.001
	PopV	6.8 ± 3.3	5.7 ± 1.9	< 0.001

Results are presented as means ± standard deviations. CNR = contrast-to-noise ratio, FV = femoral vein, HU = Hounsfield unit, IVC = inferior vena cava, PopV = popliteal vein

Table 5.

Subjective Analysis Results

Characteristics	Readers	Group 1	Group 2	p-Value
Image quality	R1	4.33 ± 0.60	4.11 ± 0.71	< 0.001
Image quality	R2	4.42 ± 0.83	4.28 ± 0.81	< 0.001
Image noise	R1	1.21 ± 0.42	1.31 ± 0.47	< 0.001
Image noise	R2	1.18 ± 0.39	1.22 ± 0.48	< 0.001

Results are presented as means ± standard deviations. R1 = reader 1, R2 = reader 2

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