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

NCT ID: NCT07342374

Last Updated: 2026-01-15

Basic Information

• Recruitment Status: COMPLETED
• Clinical Phase: NA
• Total Enrollment: 72 participants
• Study Classification: INTERVENTIONAL
• Study Start Date: 2023-02-01
• Study Completion Date: 2024-12-16

Brief Summary

This randomized controlled trial evaluates a protocol optimization for Computed Tomography Pulmonary Angiography (CTPA). The study investigates the impact of repositioning the bolus-tracking region-of-interest (ROI) from the standard pulmonary trunk (PT) to the superior vena cava (SVC). The goal is to compensate for the CT scanner's inherent transit delay time (TDT) to better align the scan with the peak arterial phase. By optimizing this timing, the study assesses whether contrast media volume can be safely reduced by 40% (from 50 ml to 30 ml) while maintaining diagnostic image quality and preventing venous contamination.

Detailed Description

Background and Rationale: Computed Tomography Pulmonary Angiography (CTPA) is the gold standard for diagnosing pulmonary embolism (PE). However, standard bolus tracking (BT) protocols that place the monitoring region-of-interest (ROI) on the main pulmonary trunk (PT) often face challenges due to the system's inherent Transit Delay Time (TDT). This delay, typically 5 seconds, can cause the diagnostic scan window to overlap with the venous phase, leading to suboptimal arterial opacification and venous contamination. This study proposes repositioning the monitoring ROI upstream to the superior vena cava (SVC) to utilize the TDT as transit time for the bolus, thereby aligning the scan window with the peak arterial phase.

Study Objectives: The primary objective is to evaluate the effect of SVC ROI repositioning on diagnostic image quality while investigating the feasibility of reducing contrast media (CM) volume by 40% (from 50 ml to 30 ml).

Methodology: This is a single-center, prospective, randomized controlled trial involving 72 adult patients. Participants are randomized into four protocol groups:

Group A (Control): ROI at PT, 50 ml contrast media. Group B: ROI at PT, 30 ml contrast media. Group C: ROI at SVC, 50 ml contrast media. Group D: ROI at SVC, 30 ml contrast media.

Protocol Details:

• Contrast Administration: Non-ionic contrast medium (370 mgI/ml) is injected at a rate of 4 ml/s, followed by a 20 ml saline flush.
• Bolus Tracking: An elliptical ROI is placed either on the PT (above the carina) or SVC depending on the group assignment.
• Triggering: The diagnostic scan is automatically initiated when enhancement reaches a threshold of 100 HU. The TDT is set to a fixed 5 seconds.
• Assessment: Diagnostic quality is assessed quantitatively by calculating arterial-venous enhancement differences (HU) and qualitatively via a 5-point Likert scale by three blinded radiologists.

Conditions

Pulmonary Artery Embolism; Pulmonary Embolism (PE)

Study Design

• Allocation Method: RANDOMIZED
• Intervention Model: PARALLEL
• Primary Study Purpose: DIAGNOSTIC
• Blinding Strategy: SINGLE

Study Groups

Group A: PT-ROI, 50 ml (Control)

Standard CTPA protocol using the bolus tracking technique with the monitoring region of interest (ROI) placed at the pulmonary trunk (PT) and 50 ml of contrast media.

Group Type: ACTIVE_COMPARATOR

Optimized CTPA Protocol

Intervention Type: DIAGNOSTIC_TEST

CTPA scans are performed on a 128-slice CT scanner using the bolus tracking technique. Non-ionic contrast medium (370 mgI/ml) is administered at a rate of 4 ml/s, followed by a 20 ml saline flush. The diagnostic scan is automatically triggered when enhancement in the monitoring region of interest (ROI) reaches a threshold of 100 HU, with a fixed transit delay time (TDT) of 5 seconds.

Group B: PT-ROI, 30 ml

Modified CTPA protocol using the bolus tracking technique with the monitoring ROI at the pulmonary trunk (PT) and a reduced contrast volume of 30 ml.

Group Type: EXPERIMENTAL

Optimized CTPA Protocol

Intervention Type: DIAGNOSTIC_TEST

CTPA scans are performed on a 128-slice CT scanner using the bolus tracking technique. Non-ionic contrast medium (370 mgI/ml) is administered at a rate of 4 ml/s, followed by a 20 ml saline flush. The diagnostic scan is automatically triggered when enhancement in the monitoring region of interest (ROI) reaches a threshold of 100 HU, with a fixed transit delay time (TDT) of 5 seconds.

Group C: SVC-ROI, 50 ml

Modified CTPA protocol using the bolus tracking technique with the monitoring ROI repositioned upstream to the superior vena cava (SVC) and 50 ml of contrast media.

Group Type: EXPERIMENTAL

Optimized CTPA Protocol

Intervention Type: DIAGNOSTIC_TEST

CTPA scans are performed on a 128-slice CT scanner using the bolus tracking technique. Non-ionic contrast medium (370 mgI/ml) is administered at a rate of 4 ml/s, followed by a 20 ml saline flush. The diagnostic scan is automatically triggered when enhancement in the monitoring region of interest (ROI) reaches a threshold of 100 HU, with a fixed transit delay time (TDT) of 5 seconds.

Group D: SVC-ROI, 30 ml

Modified CTPA protocol using the bolus tracking technique with the monitoring ROI repositioned upstream to the superior vena cava (SVC) and a reduced contrast volume of 30 ml.

Group Type: EXPERIMENTAL

Optimized CTPA Protocol

Intervention Type: DIAGNOSTIC_TEST

CTPA scans are performed on a 128-slice CT scanner using the bolus tracking technique. Non-ionic contrast medium (370 mgI/ml) is administered at a rate of 4 ml/s, followed by a 20 ml saline flush. The diagnostic scan is automatically triggered when enhancement in the monitoring region of interest (ROI) reaches a threshold of 100 HU, with a fixed transit delay time (TDT) of 5 seconds.

Interventions

Optimized CTPA Protocol

CTPA scans are performed on a 128-slice CT scanner using the bolus tracking technique. Non-ionic contrast medium (370 mgI/ml) is administered at a rate of 4 ml/s, followed by a 20 ml saline flush. The diagnostic scan is automatically triggered when enhancement in the monitoring region of interest (ROI) reaches a threshold of 100 HU, with a fixed transit delay time (TDT) of 5 seconds.

Intervention Type: DIAGNOSTIC_TEST

Eligibility Criteria

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.

• Minimum Eligible Age: 18 Years
• Maximum Eligible Age: 90 Years
• Eligible Sex: ALL
• Accepts Healthy Volunteers: No

Sponsors

Universiti Sultan Zainal Abidin

OTHER

Sponsor Role: collaborator

Hospital Queen Elizabeth, Malaysia

OTHER_GOV

Sponsor Role: lead

Responsible Party

MOHD ARI-NADZAHARI BIN ABD RAHMAN

Diagnostic Radiographer

Responsibility Role: PRINCIPAL_INVESTIGATOR

Principal Investigators

Kamarul Amin. bin Abdullah @ Abu Bakar., Assoc. Prof. Ts. Dr.

Role: STUDY_CHAIR

Universiti Sultan Zainal Abidin (UniSZA)

Locations

Hospital Queen Elizabeth

Kota Kinabalu, Sabah, Malaysia

Countries

Malaysia

Other Identifiers

NMRR-20-699-54086 (IIR)

Identifier Type: -

Identifier Source: org_study_id