Table 1.

Different causes of abnormal contrast flow, key imaging findings and solutions to obtain a diagnostic CTA

Etiology of altered contrast flow	Key imaging features	Solution
Access cannula and vein mismatch	1. Suboptimal target vessel opacification 2. Injection flow rate may be lower than planned	1. New cannula or access vein 2. When access veins are small: Dual energy scan with 50–60 keV monoenergetic reconstruction
Incorrectly placed region of interest	1. Assess location of region of interest from the bolus tracker/ bolus timing images	Correct placement of ROI, reinjection, and reimage
Extravasation	1. No target vessel opacification 2. Contrast presence in soft tissues of access vein extremity	1. New cannula and access vein at a different site
Thoracic venous outlet obstruction	1. Contrast pooling in the collaterals around axilla & chest wall	1. Asymptomatic: reinjection with arm down position 2. Symptomatic: new access site in contralateral extremity
Transient interruption of contrast bolus	1. Transient decreased contrast attenuation. 2. Presence of normal contrast in upstream vessels	1. Shallow breath hold 2. End expiratory imaging 3. Free breathing high pitch acquisition
Differential enhancement in pulmonary artery		1. Delayed acquisition 2. Biphasic injection
Differential enhancement in aorta		1. Multiplanar reformats to evaluate coarctation, shunts.
Mixing artifact in aorta	Contrast blood level, dependent pooling of contrast	1. Assessment of cardiac function Repeat delayed (30 sec) limited Z axis scan
Mixing artifact in left atrium	Contrast blood level in left atrium, pulmonary veins	Assessment of cardiac function
Poor opacification of left ventricle	No opacification of left ventricle on a pulmonary artery CTA	Assessment of cardiac function
Early enhancement on left compared to right heart	Intracardiac shunt	Assessment of cardiac function
Asystole	Dependent pooling of contrast in central veins, liver	Initiate cardiopulmonary resuscitation and page the code team