Dual-source computed tomography protocols for the pediatric chest - scan optimization techniques

Abstract

The gold standard for pediatric chest imaging remains the CT scan. An ideal pediatric chest CT has the lowest radiation dose with the least motion degradation possible in a diagnostic scan. Because of the known inherent risks and costs of anesthesia, non-sedate options are preferred. Dual-source CTs are currently the fastest, lowest-dose CT scanners available, utilizing an ultra-high-pitch mode resulting in sub-second CTs. The dual-energy technique, available on dual-source CT scanners, gathers additional information such as pulmonary blood volume and includes relative contrast enhancement and metallic artifact reduction, features that are not available in high-pitch flash mode. In this article we discuss the benefits and tradeoffs of dual-source CT scan modes and tips on image optimization.

Keywords: Chest; Children; Computed tomography; Dual energy; Dual source; Metal reduction; Ultra-high pitch.

Fig. 1

Diagram depicts the third-generation dual-source scanner. Two tubes are located 95° apart. The lower-kilovoltage (kV) tube (blue) has a larger field of view (50 cm), while the higher-kV tube (orange) has a smaller field of view (35 cm)

Fig. 2

Dynamic airway CT in a 5-month-old girl with a history of tracheoesophageal fistula status post repair with continued need for ventilatory support. CT was performed with a second-generation scanner at 80 kVp and 6 mAs. Multiple images were obtained at the same level without table movement. a, b Axial CT in maximum collapse (a) and maximum distention (b) during free-breathing. c, d Coronal reconstruction images in maximum collapse (c) and maximum distension (d) demonstrate severe tracheal stenosis at site of the surgical repair. L left, R right

Fig. 3

Dual-energy techniques in a 15-year-old boy with a history of recurrent diffuse large B cell lymphoma. a Axial CT image through the chest in soft-tissue window demonstrates a subcarinal enhancing lymph node. b Axial CT iodine map overlay shows an iodine density of 2.2 mg/mL while the background musculature is 0.3 mg/mL. c, d Axial CT of the chest in soft-tissue window (c) shows a right-upper-lobe lung abscess, with axial iodine overlay (d) demonstrating no significant iodine uptake within the abscess

Fig. 4

Pulmonary blood volume technique in a 3-year-old boy born at 24 weeks of gestational age with severe bronchopulmonary dysplasia. a Axial CT in in lung window demonstrates hyperinflated right lung with architectural distortion. b Corresponding pulmonary blood volume (dense lung) tool at the same axial level demonstrates diminished perfusion to the right lung. c, d Coronal pulmonary blood volume (c) and corresponding nuclear medicine perfusion scan (d) (anterior view) performed the same day both show marked decreased perfusion to the right lung

Fig. 5

CT angiogram dense lung tool in a 16-year-old girl with pulmonary embolism. This was a technically challenging study with presence of posterior spinal rods in a 125-kg patient. The study was performed on a third-generation scanner using 80 kVp/150 kVp plus tin filter. a–c Axial CT chest in lung window (a) and with lung perfusion pulmonary blood volume overlay (b), and axial CT with pulmonary blood volume dense lung tool (c). Note that despite improved perfusion map with the dense lung, artifact related to the metal persists (arrow). The yellow circle denotes the field-of-view limitations for the high-energy tube. No pulmonary embolism was identified

Fig. 6

Metal artifact in a 17-year-old girl with chronic lung disease, arthrogryposis and posterior spinal hardware. She was imaged with dual-energy CT using 80 kVp and 140 kVp. a–d Sagittal CT of the chest in bone windows using the monoenergetic+ tool for reducing metal artifact at 60 keV (a), 80 keV (b), 120 keV (c) and 150 keV (d). Note how the bone surrounding the hardware is more easily resolved with progressively higher kiloelectron volts, though it is just minimally improved between 120 keV and 150 keV

Fig. 7

Dual-energy chest CT in a 17-year-old boy with a history of pneumonia. a–d Axial (a) and sagittal (b) contrast-enhanced chest CT images and corresponding axial (c) and sagittal (d) virtual non-contrast images. Left-upper-lobe superior segment bronchial narrowing with post-obstructive pneumonia with a small calcification (arrow) is suggested on the contrast-enhanced CT (a, b) and confirmed on virtual non-contrast (c, d) images. Bronchoscopy with biopsy was performed and pathology showed endobronchial carcinoid tumor

Fig. 8

CT angiography in a 4-year-old boy with suspected vascular ring and aortic root dilatation. CT angiography was performed using electrocardiography (ECG)-gated cardiac ultra-high-pitch scan technique on a second-generation scanner. a–c Axial oblique (a) and coronal oblique (b) to the aortic root axis images with corresponding coronal oblique three-dimensional (3-D) reformat (c) demonstrate a normal-size aortic root (arrow). d, e Axial CT image at the level of the aberrant subclavian artery with a diverticulum of Kommerell (arrow) (d) indicates a vascular ring; corresponding coronal oblique 3-D reformat (e)

Fig. 9

CT angiography in a 5-month-old boy with pulmonary vein stenosis. a, b Axial CT angiogram of the chest performed with electrocardiography (ECG)-gated ultra-high-pitch flash (a) and dual-energy CT (b). Note the increased motion artifact caused by the decreased temporal resolution and lack of cardiac gating. The lingula pulmonary vein is narrowed (arrow) and is more easily depicted on the gated study (a)