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SOMATOM Definition Flash provides the entire extension of aortic dissection in 2 seconds scan time

SOMATOM Definition Flash Scanning

Author: Eva Hendrich* , Stefan Martinoff, MD* , Tanja Gassert**, Andreas Blaha**
*Department of Radiology and Nuclear Medicine, German Heart Center Munich, Germany
**Business Unit CT, Siemens Healthcare, Forchheim, Germany

History

A 62-year-old male patient with a known Type B aortic dissection affecting the entire descending and abdominal aorta was referred to the radiology department of the German Heart Center Munich for a follow-up examination after stenting of the right renal artery. Additionally, an actual vascular status was needed in preparation for implantation of a thoracic aortic stent. The examination was done with the new SOMATOM Definition Flash, utilizing ultrafast Flash spiral acquisition made possible by 2 X-ray tubes simultaneously collecting information. The actual scan time was only 2 seconds.
 

Diagnosis

Aortic dissection originates closely distal to the ostium of the left subclavian artery. The true lumen of the descending thoracic aorta is very narrow and comprises only about 1/3 of the aortic lumen. The cranial part of the false lumen shows a good contrast-enhancement. The worse contrast-enhanced caudal part of the false lumen indicates a low blood flow und thus predisposition to thrombosis in the false lumen. The coeliac trunk, the superior mesenteric artery and both renal arteries are feed by a very small sickle shaped true lumen of the abdominal aorta.
By contrast the inferior mesenteric artery originates from the barely perfused false lumen, therefore its proximal part is not contrast-enhanced. The distal part however is well collateralized over Riolan´s anastomosis.
The dissection ends 2 cm above aortic bifurcation.
Due to the acquisition time of only 2 seconds for thorax and abdomen, it was possible to freeze the motion of the coronary arteries. The coronary arteries show significant calcifications, especially in the proximal part of the right coronary artery (RCA).
 

Comments

Due to the lack of distance between the cranial end of the aortic dissection and the ostium of the left subclavian artery, it will be difficult to place an aortic stent.
subclavian artery, it will be difficult to place an aortic stent. The relation of true and false lumen of this type B dissection was quickly and accurately displayed. Due to the extremely fast scan time of only 2 seconds for 69 cm and highest temporal resolution of 75 msec, it was easily possible to freeze motion of the aortic arch.

Aortic Arch with RCA and Left artery descending (LAD, arrow), no motion detected (arrowhead)
Maximum Intensity Projection (MIP) of the entire aorta (arrow) highlighting stented and patent right renal artery (arrowhead)
Sagittal MIP display of aortic dissection, sickle shaped true lumen (arrowhead)
True and false lumen (arrowhead); collaterals of Riolan´s anastomosis (arrow)

Examination Protocol

Scanner SOMATOM Definition Flash
Scan area Aortic CTA
Scan length 685 mm
Scan direction Cranio-Caudal
Scan time 2 s
Tube voltage 120/120
Tube current 180 Eff. mAs
Dose modulation Care Dose
CTDIvol 10.5 mGy
Rotation time 0.28 s
Pitch 2.1
Slice collimation 128 x 0.6
Slice width 0.75 mm
Spatial resolution 0.33 mm
Reconstruction Increment 0.70
Reconstruction kernel B20f
Volume 80 ml contrast
Flow rate 4.5 ml/s
Start delay CARE Bolus

The information presented in this case study 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 Medical Systems to be used for any purpose in that regard.


The drugs and doses mentioned herein are consistent with the approval labeling 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 CT System. The source for the technical data is the corresponding data sheets. Results may vary.

Date: Apr 21, 2009


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