Cardiac Sequence: 0.9 mSv Effective Dose

SOMATOM Definition Dual Energy scanning

Paul Stolzmann, MD; Borut Marincek, MD; Hatem Alkadhi, MD
Institute of Diagnostic Radiology, Zurich University Hospital, Zurich, Switzerland
 |  2007-10-16


A 51-year-old male patient, who had suffered a single episode of atypical chest pain a few days prior, was referred to cardiac CT to rule out severe calcification and significant stenoses of the coronary arteries. The patient had a history of high cholesterol as well as a positive family history of cardiovascular disease. Since the patient showed a stable heart rate, a cardiac sequence mode was selected to achieve the lowest possible radiation exposure.


Calcium scoring demonstrated mild coronary calcifications with a total Agatston score below the 25th age- and gender-related percentile. Nitroglycerin was administered prior to the CT coronary angiography. The scan was performed from the carina to the diaphragm. A bolus of 80 ml contrast media was injected into an antecubital vein via an 18-gauge catheter with a flow rate of 5 ml/s followed by the same amount as the first phase with a dilution of 1:5 parts saline solution. The scan was started with a delay of 21 s that had been determined with the use of CARE bolus technique. The patient had a heart rate of 54 beats per minute. CT coronary angiography did not reveal any significant stenoses, with multiple very minor soft plaques without any hemodynamic relevance.


The SOMATOM Definition, the world’s first Dual Source CT, allows for a true temporal resolution of 83 ms and thus increases robustness for cardiac scanning. Here a coronary CT angiography was performed with cardiac sequence technique, the so-called step-and-shoot mode. For this, a prospectively triggered acquisition mode is used resulting in lowest possible radiation exposure. In this patient (BMI 23, 58 kg, 1.59 m) the CTA was performed with an effective dose of 0.9 mSv.


Fig. 1+2: Clear Visualization of the coronary vessels using the cardiac-sequence mode. In this right-dominant heart, no significant stenoses were evident. A myocardial bridging of the distal LAD was seen. A coronary artery disease was safely ruled out.

Examination Protocol


SOMATOM Definition
Scan area
Scan length 7 x 32 x 0.6 (134) mm
Exposure time 2 s
Scan direction Cranio-caudal
mAs/Rot 192
Rotation time
Slice collimation 0.6 mm
Reconstructed slice thickness
0.6 mm
4.01 mGy
Contrast Amount
1.80 ml Enhance /
2.16 ml Enhance+ 64 ml NaCl
Contrast Flow rate 5.0 ml/sec
Start Delay CARE Bolus


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