Korean J Radiol.  2017 Oct;18(5):860-866. 10.3348/kjr.2017.18.5.860.

Combined Electrocardiography- and Respiratory-Triggered CT of the Lung to Reduce Respiratory Misregistration Artifacts between Imaging Slabs in Free-Breathing Children: Initial Experience

• Goo HW
• Allmendinger T

• KMID: 2427223
• DOI: http://doi.org/10.3348/kjr.2017.18.5.860

Abstract

OBJECTIVE
Cardiac and respiratory motion artifacts degrade the image quality of lung CT in free-breathing children. The aim of this study was to evaluate the effect of combined electrocardiography (ECG) and respiratory triggering on respiratory misregistration artifacts on lung CT in free-breathing children.
MATERIALS AND METHODS
In total, 15 children (median age 19 months, range 6 months-8 years; 7 boys), who underwent free-breathing ECG-triggered lung CT with and without respiratory-triggering were included. A pressure-sensing belt of a respiratory gating system was used to obtain the respiratory signal. The degree of respiratory misregistration artifacts between imaging slabs was graded on a 4-point scale (1, excellent image quality) on coronal and sagittal images and compared between ECG-triggered lung CT studies with and without respiratory triggering. A p value < 0.05 was considered significant.
RESULTS
Lung CT with combined ECG and respiratory triggering showed significantly less respiratory misregistration artifacts than lung CT with ECG triggering only (1.1 ± 0.4 vs. 2.2 ± 1.0, p = 0.003).
CONCLUSION
Additional respiratory-triggering reduces respiratory misregistration artifacts on ECG-triggered lung CT in free-breathing children.

Keyword

Lung CT; ECG triggering; Respiratory triggering; Children; Motion artifacts

MeSH Terms

*Artifacts
Child
Child, Preschool
*Electrocardiography
Female
Humans
Image Enhancement
Infant
Lung/*diagnostic imaging
Male
Respiration
*Tomography, X-Ray Computed

Figure

• 

  Fig. 1 Schematic drawing of combined ECG and respiratory triggering.From ECG leads, R wave (dot) is detected and end-systolic phase (arrows) is determined by trigger delay. Pressure-sensing belt is placed in upper abdomen to continuously monitor respiratory signal; in this case, respiratory triggering (dot) is produced at inspiration peak. When they occur concurrently, these two triggering signals can be passed through gate box to CT system. Combined ECG and respiratory triggering at R wave on ECG (dot) is displayed on CT console. From combined ECG and respiratory triggering, end-systolic sequential scanning is acquired every three R waves in this case. ECG = electrocardiography

• 

  Fig. 2 Measurement of respiratory misregistration artifacts between imaging slabs on sagittal formatted lung CT image.Respiration misregistration occurred at three levels and degree of misregistration was measured in length (brackets) at six locations. Among them, maximal length (Max, orange yellow bracket) was used for semi-quantitative grading (grade 1, < 2 mm; grade 2, 2–5 mm; grade 3, 5–10 mm; and grade 4, > 10 mm).

• 

  Fig. 3 5-year-old boy with Langerhans cell histiocytosis.A, B. Free-breathing coronal (A) and sagittal (B) ECG-triggered lung CT images acquired at end-systole show grade 4 respiratory misregistration artifacts. C, D. Respiratory misregistration artifacts grade was grade 1 on free-breathing coronal (C) and sagittal (D) lung CT images with combined ECG and respiratory triggering at end-systole and inspiration peak.

• 

  Fig. 4 2-year-old girl with multifocal congenital pulmonary airway malformation.Free-breathing axial (A), coronal (B), and sagittal (C) lung CT images with combined ECG and respiratory triggering at end-systole and expiration peak demonstrate excellent normal anatomic and pathologic details without any motion artifacts.

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