Individually tailored contrast enhancement in CT pulmonary angiography

Objective: The purpose was to evaluate individually shaped contrast media (CM) delivery in CT pulmonary angiography (CTPA) for suspected pulmonary embolism (PE). Methods: 100 consecutive emergency patients with clinical suspicion of PE were evaluated. High-pitch CTPA was performed on a second-generation dual-source CT using the following parameters: 100kV, 200-250mAsref, rotation time 0.28s, 128 x 0.6mm col. and image reconstruction 1.0/0.8mm (B30f). Group 1 (n = 50) then received a fixed CM bolus (3005mgl ml(-1), volume = 90ml and flow rate = 6ml s(-1)); Group 2 (n = 50) received a body weight-adapted CM bolus determined by dedicated contrast injection software. For analysis, groups were further subdivided into low-weight (40-75 kg) and high-weight (76-117 kg) groups. Technical image quality was graded using a four-point Likert scale (15non-diagnostic; 2 = diagnostic; 3 = good and 4 = excellent image quality) at the level of the pulmonary trunk and pulmonary arteries. Objective image quality analysis was performed by measuring contrast enhancement in Hounsfield units (HU) at the same levels. Attenuation levels > 180HU were considered diagnostic. Results: All examinations were graded as diagnostic at each level. The individual minimum pulmonary attenuation was 184 and 270HU for Group 1 and 2, respectively. Mean attenuation was as follows: Group 1: 475 +/- 105HU (40-75 kg) and 402 +/- 115HU (76-117 kg), p <0.03. Group 2: 424 +/- 76HU (40-75 kg) and 418 +/- 100HU (76-117 kg), p = 0.8. For Group 2, CM volumes were: 55 +/- 5ml (40-75 kg) and 66 +/- 5ml (76-117 kg), leading to 16-51% CM reduction. Conclusion: Even under emergency conditions, individualized CM protocols can provide diagnostic and robust image quality in CTPA for PE with a substantial reduction of CM volume for lower weight patients, compared with a fixed CM protocol. Advances in knowledge: CM volume can substantially be reduced by using individualized CM protocols in CT angiography for PE without compromising the diagnostic image quality.