Low-dose spiral CT: applicability to paediatric chest imaging.
BACKGROUND
Spiral CT of the chest is an imaging technique with unequivocal indications and proven higher sensitivity and specificity than conventional chest X-rays. However, particularly in children, attempts should be made to reduce radiation exposure to a minimum. OBJECTIVE. To evaluate whether a low-dose technique in spiral CT scanning results in adequate diagnostic information.


METHODS
In a prospective study, 27 children (range 3 weeks to 14 years, mean 7 years) underwent a low-dose CT examination of the chest for various indications. The tube energy was 12.5 mAs (n = 5), 25 mAs (n = 17), 50 mAs (n = 3), or 75 mAs (n = 2) per slice. Two radiologists evaluated, in consensus, the CT scans with respect to their diagnostic value and comparison was made with 20 standard-dose chest CT examinations of adults (175 mAs per slice, mean age 56 years) with respect to technical image quality (noise and artefacts). In a second part of the study, dose measurements were carried out by means of exposing thermoluminescent dosimeters attached to a water/air phantom simulating a child's chest.


RESULTS
All low-dose CT scans were of diagnostic image quality and no additional studies were necessary. The average image noise was significantly higher than in standard-dose CT examinations (SD 39.5 compared with 12.5 for unenhanced soft tissue, P < 0.01), but did not hinder accurate diagnosis. Artefacts were exclusively due to patient motion. Radiation exposure per slice was approx. 4 mGy at 25 mAs and 34 mGy at 250 mAs, regardless of slice thickness.


CONCLUSIONS
For all indications in paediatric CT scanning of the chest, low-dose technique provides adequate image quality without loss of diagnostic information. The radiation exposure is approximately 5-20 % of a standard-dose CT.
Department of Diagnostic and Interventional Radiology, Charité Hospital, Humboldt-Universität zu Berlin, Schumannstrasse 20/21, D-10 117 Berlin, Germany.
P
P
Rogalla
B
B
Stöver
I
I
Scheer
R
R
Juran
G
G
Gaedicke
B
B
Hamm
D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007223:Infant; D007231:Infant, Newborn; D008171:Lung Diseases / Q000000981:diagnostic imaging*; D008297:Male; D019047:Phantoms, Imaging; D011446:Prospective Studies; D011829:Radiation Dosage; D013902:Radiography, Thoracic / Q000379:methods*; D018709:Statistics, Nonparametric; D014057:Tomography, X-Ray Computed / Q000379:methods*