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New 70 kV Protocol Ensures Low Radiation Dose in Patients with Congenital Heart Disease

SOMATOM Definition AS+ scanning

Author: Michael Lell, MD, PD*; Oliver Rompel, MD*´; Andreas Blaha**
* Departement or Radiology, University of Erlangen-Nuremberg, Erlangen, Germany;
** Computed Tomography, Siemens Healthcare, Forchheim, Germany

History

A 10-month-old male baby underwent surgery for multiple ventricular septal defects (VSD) as well as a secundumtype atrial septal defect (ASD). Partially anomalous pulmonary venous return, insufficiency of the tricuspid valve and a patent ductus arteriosus were corrected in prior surgical procedures, as was banding of the pulmonary artery. The post-operative phase, after closure of the VSDs and ASD, was complicated with infection and secretion from the sternotomy wound appeared. Before re-thoracotomy, a low-dose chest CT was performed as planning base for the following surgery.

 

Diagnosis
The scan on a SOMATOM Definition AS+ revealed the proper location of the ductus arteriosus clip. A sickle shaped retrosternal fluid collection could be demonstrated as well as interstitial edema and dystelectasis. The right ventricle is enlarged and the right ventricular wall significantly thickened.

 

Comments
With the fast acquisition time of 1.2 seconds covering 129 mm, precise diagnosis could be established in mild sedation. Children with CHD usually require multiple imaging studies in the Follow-Up. Therefore, it is critical to keep the cumulative radiation dose as low as possible. A dedicated low-dose pediatric acquisition protocol, with auto selection and adjustment of kV and mAs is very useful in this patient group to ensure consistently high image quality at reasonably low dose.

 

Fig. 1: VRT Overview of the 70 kV chest acquisition.
Fig. 2: Fused VRT and MPR image shows the location of the ductus arteriosus botalli clip.
Fig 3: Coronal view of paediatric chest shows the extension of the retrosternal fluid deposit.
Fig 4: In this axial slice a fluid depot retrosternal is well visible.

Examination Protocol

Scanner SOMATOM Definition AS+
Scan area Thorax
Scan length 129 mm
Scan direction Caudo-Cranial
Scan time 1.2 s
Tube voltage 70 KV
Tube current 130 eff. mAs
Dose modulation CARE Dose4D
CTDIvol 3.07 mGy
DLP 29 mGycm
Rotation time 0.5 s
Pitch 1.4
Slice collimation 32 x 1.2 mm
Slice width 1.5 mm
Spatial resolution 0.33 mm
Reconstruction kernel B30f / I30
Contrast  
Volume 5 ml
Flow rate Injection by hand
Start delay after injection completed

Date: 2011-07-26


Case Studies

The information presented is for illustration only and is not intended to be relied upon by the reader for instruction as to the practice of medicine. Any health care practitioner reading this information is reminded that they must use their own learning, training and expertise in dealing with their individual patients. This material does not substitute for that duty and is not intended by Siemens Healthcare to be used for any purpose in that regard.

The drugs and doses mentioned herein are consistent with the approval labelling for uses and/or indications of the drug. The treating physician bears the sole responsibility for the diagnosis and treatment of patients, including drugs and doses prescribed in connection with such use. The Operating Instructions must always be strictly followed when operating the system. The source for the technical data is the corresponding data sheets. Results may vary.

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