The purpose of this study is to assess the effect of three different strategies to inject at reduced volume of contrast medium in Computed Tomography Pulmonary Angiography (CTPA).

330 patients referred for CTPA are randomized to receive either a low-concentration, a low-volume or a saline-diluted injection.

Effects on the level and homogeneity of contrast enhancement are measured and compared between groups.

Spectral detector CT facilitates large reductions in contrast medium in vascular CT examinations. To our knowledge, no studies have so far compared different strategies to inject this reduced contrast dose.

The purpose of this study is to assess the effect of three different strategies to inject at reduced volume of contrast medium in Computed Tomography Pulmonary Angiography (CTPA).

330 patients referred for clinically indicated CTPA are randomized to receive either a low-concentration, a low-volume or a saline-diluted injection. All patients receive the same amount of iodine (140 mg/kg).

Effects on the level and homogeneity of contrast enhancement, image noise, contrast-to-noise-ratio and signal-to-noise-ratio are measured in the CT images and the results are compared between groups.

Inclusion Criteria:

• Inpatients and outpatients with kidney function (eGFR) allowing for safe administration of contrast dose (as calculated with the OmniVis calculator).
• Patients with clinical suspicion of disease of PE
• Referral to CTPA diagnosis, treatment planning or follow-up.
• Peripheral venous catheter (PVC) =/< 18 G

Exclusion Criteria:

• Contraindication to iodinated contrast medium
• Age < 18 years
• Lack of informed consent
• Pregnancy

Acquired CT images are identical for all participants. The study arm is unknown to all, except the radiographers (radiology technicians) performing the examination.