1. Determining the normal aorta size in infants and children
S Bruce Greenberg, Shilpa V Hegde, Shelly Lensing
University of Arkansas for Medical Sciences
Little Rock , AR.

2. Normal aorta size in Children
Echocardiography: limited to planar measurements of thoracic aorta
CT and MRA:
Limited standards for thoracic aorta
Technique
Patient age
No standards for abdominal aorta .

3. Purpose: Determine the normal range of effective diameters for the aorta at multiple locations and common iliac arteries in children of all sizes

4. Patients and methods: Inclusion criteria Exclusion Criteria
All torso computed tomography examinations performed with IV contrast from 7/9/2012 to 12/27/2012
Exclusion Criteria
Cardiovascular disease
Unknown patient height
Total CT examinations 137
Thorax 89
Abdomen 111

5. CT indications: Total 137 Indications for CT Oncology 57 Pain 22
Trauma
Infection
Miscellaneous

6. Patient age and size Age
Mean : 9.9 years (Standard Deviation 5.7 years)
Range : 2 weeks to 20 years
Body Surface Area
Mean: 1.24 m 2 (Standard Deviation 0.57 m 2)
Range: 0.19 m 2 to 2.5 m 2

7. Measurement locations
Double oblique MPR using 1 mm reconstructions
Effective diameter measured by 2 readers

8. Measurement method: double oblique
Effective diameter of abdominal Aorta just above the celiac axis = 16 mm

9. Statistical Methods
Intraclass correlation for inter-rater reliability of 2 readers
Multiple linear regression models relating
Body surface area
Effective diameter
Outliers with standardized residuals < 3 or >3 were deleted

10. Intraclass Correlation: excellent
Thorax
Abdomen
Aortic Annulus
Aortic Sinus
Sino Tubular Junction
Ascending Aorta
Arch
Isthmus
Prox. Descend. Aorta
Aorta at the diaphragm
Superior to celiac axis
Renal artery level
Superior to bifurcation
Right common iliac artery 0.95
Left common iliac artery

11. Results: AORTA ROOT Formula root MSE R2
Loge (Aorta Annulus) = *BSA *BSA *BSA3
0.088
0.902
Loge (Sinus of Valsalva) = *BSA *BSA *BSA3
0.097
0.892
Loge (Sino Tubular Junction) = *BSA – 1.106*BSA *BSA3
0.109
0.894

12. Results: thoracic aorta
Formula
root MSE R2
loge(Mid Ascending Aorta)= *BSA – 1.014*BSA *BSA3
0.118
0.872
loge(Arch)= *BSA – 0.984*BSA *BSA3
0.107
0.906
loge(Isthmus)= *BSA – 1.136*BSA *BSA3
0.103
0.913
loge(Proximal Descending Aorta)= *BSA – 0.930*BSA *BSA3
0.113
0.881
loge(Aorta at Diaphragm)= *BSA – 0.667*BSA *BSA3
0.104
0.886

13. Results: Abdominal aorta and iliac arteries
Formula
root MSE R2
loge (Superior to Celiac Axis) = *BSA *BSA *BSA3
0.104
0.856
loge (Level Renal Arteries) = *BSA – 0.725*BSA *BSA3
0.123
0.848
loge (Aorta above Bifurcation) = *BSA – 0.957*BSA *BSA3
0.114
0.883
loge(Right Common Iliac)= *BSA – 1.489*BSA *BSA3
0.149
0.829
loge(Left Common Iliac)= *BSA – 1.506*BSA *BSA3
0.115
0.875

14. Z-score (Standard deviation) calculation

15. Z score calculation: 14 week old child with William’s Syndrome with a body surface area of 0.3m2. Effective diameter of the aorta at the level of isthmus was 4.7mm.

16. Z-score (STANDARD DEVIATION) calculation
Observed value : natural log of observed measurement loge 4.7 = 1.54
Predicted value : loge(Isthmus) = *BSA – 1.136*BSA *BSA3
= *0.3 – 1.136*(0.3) *(0.3)3 = 1.988
Z score = [calculation 1 – calculation 2] ÷ √ MSE = [ ] ÷ = - 4.2

17. Z-scores in Williams patient
Enter BSA (units)
Enter observed diameter (mm)
Calculated predicted diameter (mm)
Z-Scores
Aorta Annulus
#NUM!
Sinus of Valsalva
Sino Tubular Junction
Mid Ascending Aorta
Arch
Isthmus
Proximal Descending Aorta
Aorta at Diaphragm
Superior to Celiac Axis
Level Renal Arteries
Aorta above Bifurcation
Right Common Iliac
Left Common Iliac
Enter BSA (units)
Enter observed diameter (mm)
Calculated predicted diameter (mm)
Z-Scores
0.3
Aorta Annulus 9
11.2
-2.76
Sinus of Valsalva 10
13.2
-2.82
Sino Tubular Junction
4.5
9.6
-7.14
Mid Ascending Aorta
5.2
-5.29
Arch
5.3
7.9
-3.68
Isthmus
4.7
7.0
-4.02
Proximal Descending Aorta
4.8
7.4
-4.01
Aorta at Diaphragm
-4.07
Superior to Celiac Axis
4.3
6.6
-4.19
Level Renal Arteries
3.4
5.1
-3.41
Aorta above Bifurcation
3.2
-2.93
Right Common Iliac
2.5
2.8
-0.68
Left Common Iliac
2.9
-1.22

18. Diffuse aorta hypoplasia
Enter BSA (units)
Enter observed diameter (mm)
Calculated predicted diameter (mm)
Z-Scores
0.3
Aorta Annulus 9
11.2
-2.76
Sinus of Valsalva 10
13.2
-2.82
Sino Tubular Junction
4.5
9.6
-7.14
Mid Ascending Aorta
5.2
-5.29
Arch
5.3
7.9
-3.68
Isthmus
4.7
7.0
-4.02
Proximal Descending Aorta
4.8
7.4
-4.01
Aorta at Diaphragm
-4.07
Superior to Celiac Axis
4.3
6.6
-4.19
Level Renal Arteries
3.4
5.1
-3.41
Aorta above Bifurcation
3.2
-2.93
Right Common Iliac
2.5
2.8
-0.68
Left Common Iliac
2.9
-1.22

19. OR USE THE GRAPH : *

20. Objective evaluation of hypoplasia or aneurysm
Conclusion
Normal values for the effective diameter of the aorta can now be determined in children of all sizes using the derived formulas
Objective evaluation of hypoplasia or aneurysm