Korean J Radiol.  2013 Apr;14(2):183-193. 10.3348/kjr.2013.14.2.183.

CT Venography for Deep Vein Thrombosis Using a Low Tube Voltage (100 kVp) Setting Could Increase Venous Enhancement and Reduce the Amount of Administered Iodine

• Cho ES
• Chung JJ
• Kim S
• Kim JH
• Yu JS
• Yoon CS

• KMID: 1482776
• DOI: http://doi.org/10.3348/kjr.2013.14.2.183

Abstract

OBJECTIVE
To investigate the validity of the 100 kVp setting in CT venography (CTV) in the diagnosis of deep vein thrombosis (DVT), and to evaluate the feasibility of reducing the amount of administered iodine in this setting.
MATERIALS AND METHODS
After receiving the contrast medium (CM) of 2.0 mL/kg, 88 patients underwent CTV of the pelvis and lower extremities by using one of four protocols: Group A, 120 kVp setting and 370 mgI/mL CM; group B, 120 kVp and 300 mgI/mL; group C, 100 kVp and 370 mgI/mL; group D, 100 kVp and 300 mgI/mL. The groups were evaluated for venous attenuation, vein-to-muscle contrast-to-noise ratio (CNRVEIN), DVT-to-vein contrast-to-noise ratio (CNRDVT), and subjective degree of venous enhancement and image quality.
RESULTS
Venous attenuation and CNRVEIN were significantly higher in group C (144.3 Hounsfield unit [HU] and 11.9), but there was no significant difference between group A (118.0 HU and 8.2) and D (122.4 HU and 7.9). The attenuation value of DVT was not significantly different among the four groups, and group C had a higher absolute CNRDVT than the other groups. The overall diagnostic image quality and venous enhancement were significantly higher in group C, but there was no difference between groups A and D.
CONCLUSION
The 100 kVp setting in CTV substantially help improve venous enhancement and CNRVEIN. Furthermore, it enables to reduce the amount of administered iodine while maintaining venous attenuation, as compared with the 120 kVp setting.

Keyword

CT venography; Deep vein thrombosis; Low tube voltage; Contrast medium; Contrast enhancement

MeSH Terms

Contrast Media/administration & dosage
Feasibility Studies
Female
Humans
Iohexol/administration & dosage/analogs & derivatives
Linear Models
Lower Extremity/blood supply/*radiography
Male
Middle Aged
Phantoms, Imaging
Phlebography/*methods
Statistics, Nonparametric
Tomography, X-Ray Computed/*methods
Venous Thrombosis/*radiography
Contrast Media
Iohexol

Figure

• 

  Fig. 1 Cylindrical water phantom and CT images of phantom. A. 300 mm-diameter cylindrical water phantom simulated abdomen of patients with intermediate body weight. 25 mm-diameter tube filled with diluted contrast medium (CM) was inserted into center of phantom. B. Transverse 1 mm CT scans of phantom obtained at 120 kVp with 1.4% 370 mgI/mL CM, 120 kVp with 1.4% 300 mgI/mL CM, 100 kVp with 1.4% 370 mgI/mL CM, and 100 kVp with 1.4% 300 mgI/mL CM. 1.4% concentration of CM in tube resulted in mean CT attenuation values most similar to those obtained for CT venography in clinical studies (113.0 Hounsfield unit (HU) in 120 kVp with 370 mgI/mL CM, 94.2 HU in 120 kVp with 300 mgI/mL CM, 145.0 HU in 100 kVp with 370 mgI/mL CM, and 116.0 HU in 100 kVp with 300 mgI/mL CM).

• 

  Fig. 2 Graphs showing results of phantom study. A. Relationship between CT attenuation value and contrast medium (CM) concentration was: for 100 kVp with high concentration CM (HC-CM), y = 97.7x + 10.3 (r = 0.999); for 100 kVp with moderate concentration CM (MC-CM), y = 82.2x + 6.4 (r = 0.998); for 120 kVp with HC-CM, y = 75.7x + 7.8 (r = 0.999); and for 120 kVp with MC-CM, y = 63.7x + 5.7 (r = 0.999). B. Relationship between contrast-to-noise ratio (CNR) and CM concentration was: for 100 kVp with HC-CM, y = 3.0x + 0.5 (r = 0.996); for 100 kVp with MC-CM, y = 2.5x + 0.3 (r = 0.998); for 120 kVp with HC-CM, y = 2.5x + 0.4 (r = 0.997); and for 120 kVp with MC-CM, y = 2.1x + 0.3 (r = 0.999).

• 

  Fig. 3 Graphs showing results of clinical study. Box-and-whisker plot showing median (middle line of each box), quartiles (top and bottom lines of each box), and upper and lower adjacent (upper and lower whiskers for each box) of mean attenuation value of veins (A), vein-to-muscle contrast-to-noise ratio (CNRVEIN) (B), mean attenuation value of deep vein thrombosis (DVT) (C), and DVT-to-vein contrast-to-noise ratio (CNRDVT) (D). Dotted lines = no significant difference between two groups. Solid lines = significant difference between two groups. A, B. Mean venous attenuation value and CNRVEIN in group C (100 kVp and 370 mgI/mL setting) were significantly higher than those of other groups. There was no difference in venous attenuation value and CNRVEIN between group A (120 kVp and 370 mgI/mL setting) and group D (100 kVp and 300 mgI/mL setting). C, D. Mean DVT attenuation value and CNRDVT was not significantly different among four groups. CNRDVT in group C was lower than that of other groups but this was not significant.

• 

  Fig. 4 Comparison of attenuations of veins and deep vein thrombosis (DVT) on axial CTV images obtained in (A) 120 kVp and 370 mgI/mL setting, (B) 120 kVp and 300 mgI/mL setting, (C) 100 kVp and 370 mgI/mL setting, and (D) 100 kVp and 300 mgI/mL contrast medium setting from representative patient of each group. Attenuation values and vein-to-muscle contrast-to-noise ratio of non-thrombosed vein (arrow head) in these patients were 124.3 HU and 8.2 in (A), 98.1 HU and 6.5 in (B), 144.1 HU and 12.3 in (C), and 129.4 HU and 8.9 in (D). Attenuation values of DVT (arrow) and DVT-to-vein contrast-to-noise ratio were 32.8 HU and -14.8 in (A), 50.2 HU and -8.3 in (B), 43.4 HU and -16.8 in (C), and 28.4 HU and -14.9 in (D). Subjective scores for venous enhancement, image noise, and overall diagnostic image quality were 2.0, 3.0, and 3.0 in (A), 2.0, 3.0, and 2.0 in (B), 3.0, 3.0, and 3.0 in (C), and 2.0, 3.0, and 3.0 in (D). CVT = computed tomoraphy venography, HU = Hounsfield unit

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