Measurement of Pediatric Thoracic Aorta from contrast enhanced axial CT


A1= (0.720 x age) +11.55mm

A2= (0.629 x age) + 9.54mm

B1= (0.668 x age) + 13.0mm

B2= (0.572 x age) + 9.56mm

B3= (0.559 x age) + 8.44mm

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Level A= 1cm below aortic arch

Level B= 1cm cranial to aortic arch

Level C= 1cm cranial to domeof right hemidiaphragm

Above regression charts plot mean with 95% confidence limits.

Reference: Fitzgerald SW, Donaldson JS, Poznanski AK. Pediatric thoracic aorta: Normal measurements determined with CT. Radiology 1987; 165:667-669 (Used with permission from author: awaiting permission from publisher)

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Bronchietasis is defined by a bronchus-to-artery ratio of >1.2 on chest radiographs 1§.

§ Based on the external diameters of both the pulmonary arteries and bronchi on chest radiographs.

Normal bronchi are not usually seen in the most peripheral 5 to 10 mm of the lung on CT 2.


1. Woodring JH. Pulmonary artery-bronchus ratios in patients with normal lungs, pulmonary vascular plethora, and congestive heart failure. Radiology 1991; 179:115-22.

2. Siegel MJ. Pediatric Body CT. Lippincott Williams & Wilkins: Philadelphia. 1999. p. 101.

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Cardiothoracic Index

(made on upright frontal view of chest at 72 inches during quiet breathing)

(re-drawn from Caffey J. Pediatric X-ray Diagnosis. 7th Ed. 1978, p 543)

ID = internal diameter of chest at level of right hemidiaphragm

MRD = greatest perpendicular diameter from midline to right heart border

MLD = greatest perpendicular diameter from midline to left heart border

CT index = (MRD + MLD)/ID


1st year of life, larger CT index due to more transverse heart position in chest compared to older children and adults, and from data derived from films obtained in expiratory phase of respiration. Data in infants and young children obtained from supine films at 1.5m distance

1. Bakwin H, Bakwin R. Body build in infants: VI. Growth of the cardiac silhouette and the thoraco-abdominal cavity. Am J Dis Child. 49:861, 1935

2. Maresh MM, Washburn AH. Size of the heart in healthy children. Am J Dis Child 56:33, 1938

3. Lincoln EM, Spillman R. Studies of the hearts of normal children: II. Roentgen ray studies. Am J Dis Child 35:791, 1928.

Retropharyngeal & Retrotracheal Soft Tissues

Retropharyngeal Soft Tissues 1

(lateral radiographs of the neck)

(measurement made at mid-portion of C5 vertebral body on lateral radiograph)

Retrotracheal Soft Tissues 1

(lateral radiographs of the neck)

(measurement made at mid-portion of C5 vertebral body on lateral radiograph)

Note: expiratory phase and flexion of neck increases apparent thickness of tissues artifactually

Rule of 7's:

no greater than 7mm for retropharyngeal soft tissues

no greater than 14mm for retrotracheal soft tissues 2


1.Hay PD, Jr. The Neck: A roentgenological study of the soft tissues: Consideration of the normal and pathological. III. Normal necks (infants and children). Ann Roentgenol Vol 9. New York: Hoever, 1930, p22-8

2.Redman HC, Purdy PD, Miller GL, Rollins NK. Emergency Radiology. Cervical Spine. W.B. Saunders 1993. p 183-186.


Normal Measurements of the Thymus on CT: Mean Values


1. Francis IR, Glazer GM, Bookstein FL, Gross BH. The thymus: reexaminatinon of age-related changes in size and shape. AJR 1985; 145:249-254. Table and diagram used with permission.

FONTE: https://www.ohsu.edu/school-of-medicine/diagnostic-radiology/pediatric-radiology-normal-measurements