CT Pulmonary angiogram (CTPA)

Related Subjects: |Assessing Breathlessness |Pulmonary Embolism | Deep Vein Thrombosis | DVT/PE in pregnancy | CTPA

Introduction

• Computed tomography pulmonary angiogram (CTPA) is used to diagnose the presence or absence of a PE following risk stratification.
• It involves the injection of a radiopaque dye which should full the pulmonary artery and its branches
• A PE is demonstrated by evidence that contrast cannot be seen in pulmonary artery or branches
• There is a filling defect in the pulmonary artery and its branches where the artery is less bright

Anatomy

• The pulmonary artery looks like an inverted Y with one leg going back to the right and one going back to left.

Contraindications

• CTPA is best avoided where possible in pregnancy due to the amount of ionizing radiation required, which may increase the risk of breast cancer. Breasts are particularly sensitive during pregnancy. However the fetus can be protected screened from radiation.
• In pregnancy iodine may have effects on the fetus thyroid gland.
• CTPA is contraindicated in known or suspected allergy to contrast media or in renal failure (where contrast agents could worsen the renal function).
• Include the creatinine in the request and discuss with the radiologist before organising the test. There is a risk of contrast-induced nephropathy. Patients should be hydrated before CTPA.

Main PA (MPA) and Right (RPA) and left PA (LPA)

PE example

PE example

Online video

Part 2 Video on How to read a CT PA