Ultra Low Dose CT Pulmonary Angiography with Iterative Reconstruction

Area of Science:

• Radiology
• Medical Imaging
• Cardiovascular Imaging

Background:

• Pulmonary embolism (PE) diagnosis relies on computed tomography pulmonary angiography (CTPA).
• Reducing radiation dose in CTPA is crucial for patient safety.
• Novel reconstruction algorithms are needed to maintain diagnostic quality at lower doses.

Purpose of the Study:

• To evaluate a new Iterative Model Reconstruction (IMR) algorithm for PE detection in ultra-low dose CTPA.
• To compare IMR with standard filtered back projection (FBP) and iDose algorithms at simulated reduced radiation doses.
• To assess the impact of dose reduction on image quality, diagnostic confidence, and PE detectability.

Main Methods:

• Simulated ultra-low dose CTPA datasets from 16 PE patients were created at dose levels of 50% down to 3.1% of original settings.
• Datasets were reconstructed using FBP, iDose, and IMR algorithms.
• Two blinded radiologists evaluated 288 datasets for image quality, diagnostic confidence, PE detectability, and contrast-to-noise ratio (CNR).

Main Results:

• IMR and iDose demonstrated superior PE detectability compared to FBP.
• IMR achieved 100% sensitivity for PE detection down to 12.5% dose level (0.45 mSv).
• IMR significantly improved CNR and subjective image quality metrics over FBP and iDose across all dose levels.

Conclusions:

• Iterative Model Reconstruction (IMR) enables significant dose reduction in CTPA for PE detection, up to 75%.
• Diagnostic confidence and image quality are maintained even at substantially reduced radiation doses with IMR.
• The use of IMR can lead to a mean effective dose of approximately 0.9 mSv for CTPA examinations.