Abstract

Step-and-Shoot Mode: 0.9 mSv Effective Dose

posted by Hatem Alkadhi, M.D. | Jan 2, 2008

Case history

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 step-and-shoot mode was selected to achieve the lowest possible radiation exposure.

Diagnosis

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 the CARE bolus technique. The patient had a heart rate of 54 beats per minute during the data acquisition. CT coronary angiography did not reveal any significant stenoses, with multiple minor soft plaques without hemodynamic relevance.

Comments

In this patient, a coronary CT angiography examination was performed in the step-and-shoot mode, also called cardiac sequence technique. This technique is characterized by a prospectively triggered acquisition mode that results in the lowest possible radiation exposure. In this patient (BMI 22.9 kg/m2, 58 kg, 1.59 m) the CTA was associated with an effective dose of 0.9 mSv.