• Selma Uysal Ramadan, Pinar Kosar, Iclal Sonmez, Sevilay Karahan, and Ugur Kosar.
• Department of Radiology, Ankara Training and Research Hospital, Ankara, Turkey. uysalselma@yahoo.com
• Eur Radiol. 2010 Sep 1;20(9):2100-7.

ObjectiveTo compare the image quality of computed tomography pulmonary angiography (CTPA) obtained with the injection of various low doses of contrast medium (CM) with different injection-related factors.MethodsA total of 90 patients (42 females, 48 males; 54.3 +/- 18.6 years) undergoing CTPA were included. Three CM protocols, each containing 30 patients, were created. Protocols 1, 2 and 3 consisted of a CM of 60 ml, 55 ml and 50 ml, and a bolus trigger level of 120 HU, 90 HU and 75 HU, respectively. Injection was uniphasic for protocols 1 and 2 (flow rate 5 ml/s), and biphasic for protocol 3 (flow rates 5 and 4 ml/s); with saline flushing afterwards. Enhancement was measured in three central and six peripheral pulmonary arteries.ResultsThe mean attenuation value for pulmonary arteries was over 250 HU for all protocols. There was no difference between the attenuation levels with the protocols (p > 0.05). The percentage of pulmonary arteries exceeding optimal attenuation (> or =250 HU) showed that protocols 2 and 3 were 90-100% successful (p < 0.05).ConclusionThe use of proper injection-related factors during CTPA, such as a low trigger level and a high flow rate with saline injection following a decreased CM volume (55 ml or 50 ml), will enable adequate pulmonary artery contrast enhancement.

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