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Motion-free thoracic infant scan follow-up study after chemotherapy

Author: Susann Skoog, MD, Nils Dahlström, MD,
and Petter Quick, Technologist and Application Specialist
Department of Radiology and Center for Medical Image Science and Visualization (CMIV),
University Hospital, Linköping, Sweden

History

A three-year-old boy with small (7-8 mm diameter) lung metastases from a germ cell tumor, successfully treated with chemotherapy, was referred for follow-up CT of the thorax. In a previously acquired CT examination without sedation, utilized 59.95 DLP / scan length 140 mm, the patient was not cooperative.
In the present Flash scan, no remaining metastases where identified, and the serum tumor marker Alpha Fetoprotein (AFP) levels are normal.
 

Diagnosis

The ultra-fast thoracic scan mode using pitch value of 3 did not reveal any metastatic lesions or other pathological findings in the thorax. Both lungs are well perfused and there is no sign of any enlarged lymph nodes. The size of the thymus has increased moderately. Inverted Maximum Intensity Projection (MIP) showed a regular bronchial tree.
 

Comments

Continuous follow-up CT examinations are necessary to monitor the treatment effect and determine the complete patient response. Using Somatom Definition Flash CT for a high-pitch spiral acquisition the patient is examined with greatly reduced radiation dose in comparison to standard CT protocols, in this case only 1.08 mSv where applied.
The fast scan mode which acquires the patients’ thorax in only 0.42 seconds avoids the need to sedate the pediatric patient; and a motion free scan results in a valuable examination (and diagnosis) without the need of a second scan.
 

Fused volume rendered view of the entire chest.
A sagittal view highlights the absence of motion, especially seen in the patients’ diaphragm.
Inverted Maximum Intensity Projection (MIP) shows a regular bronchial tree.
Bilateral well-perfused lung in this coronal view.
Coronal view from previous CT Scanner (59.95 DLP, arrows) showing motion caused of breathing.
Sagittal view from previous CT Scanner of breathing patient making diagnosis more difficult.

Examination Protocol

Scanner SOMATOM Definition Flash
Scan area Thorax CTA
Scan length 172 mm
Scan direction Cranio -Caudal
Scan time 0.42 sec
Tube voltage 120 kV
Tube current 20 mAs
Dose modulation CARE Dose 4D
CTDIvol 1.23 mGy
DLP 30 mGy/cm
Effective Dose 1.08 mSv
Rotation time 0.28 s
Pitch 3
Slice collimation 128 x 0.6 mm
Slice width 0.75 mm
Spatial Resolution 0.33 mm
Reconstruction kernel B31f
Contrast  
Volume 30 ml Ultravist 370 mg/ml
Flow rate 1 ml/s
Start delay 30 s

Date: Jun 16, 2010


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