Repositioning the Bolus Tracking ROI to the Superior Vena Cava in CTPA Facilitates Contrast Volume Reduction

Inclusion Criteria: * All patients scheduled for a Computed Tomography Pulmonary Angiography (CTPA) examination. * Provision of written informed consent by the subject, guardian, or medical specialist. * Patients with an upper extremity intravenous (IV) line using a 16-20 gauge cannula. * Patients with a stable heart rate between 60 and 120 beats per minute (bpm). Exclusion Criteria: * Pregnancy, breastfeeding, or use of non-reliable methods of contraception. * Patients with impaired renal function, including acute kidney injury or chronic kidney disease (CKD) with an eGFR less than 30 mL/min/1.73m². * Patients with a lower extremity IV line, as this bypasses the Superior Vena Cava (SVC) and results in bolus tracking technique failure. * Patients with a heart rate lower than 60 bpm or higher than 120 bpm. * Patients with a cannula size of 22g or smaller, as it cannot accommodate the high flow rate (4 mL/s) required by the power injector. * Patients with severe cardiac impairment or congenital heart disease. * Patients with a Body Mass Index (BMI) exceeding 35 kg/m², as severe obesity causes beam hardening effects that degrade image quality.