[Reduction of radiation exposure during computed tomography perfusion using an iterative reconstruction method]

Area of Science:

• Medical Imaging
• Radiology
• Image Processing

Background:

• Computed tomography (CT) perfusion (CTP) imaging is crucial for diagnosing cerebrovascular diseases.
• Radiation exposure is a concern in CTP, necessitating dose reduction strategies.
• Iterative reconstruction (IR) techniques offer potential for noise reduction and dose optimization.

Purpose of the Study:

• To evaluate the image noise reduction capabilities of IR for lowering radiation exposure in CT perfusion.
• To assess the accuracy of low-dose IR-generated CTP maps (CBV, MTT, CBF) in simulating ischemic conditions.
• To identify the optimal IR filter for noise reduction in low-dose CTP imaging.

Main Methods:

• A contrast phantom was scanned using varying radiation doses.
• Images were reconstructed using filtered back projection (FBP) and adaptive iterative dose reduction 3D (AIDR3D) at four noise reduction levels.
• The accuracy of low-dose IR CTP maps was evaluated using a digital perfusion phantom simulating ischemic cases.
• The optimal IR filter was determined by analyzing the noise power spectrum (NPS) in the low-frequency area at low doses.

Main Results:

• An optimal IR filter was identified, achieving noise levels equivalent to the reference (150 mA, FBP) at low doses.
• CTP maps generated with the optimal IR filter enabled dose reduction to 80 mA.
• A total dose reduction of 46% compared to the reference was achieved using NPS analysis and IR.
• Low-dose IR images accurately simulated dynamic curves of ischemic cases.

Conclusions:

• Iterative reconstruction (IR) significantly reduces radiation exposure in CT perfusion imaging.
• The use of NPS analysis aids in selecting optimal IR filters for dose reduction.
• IR technology holds substantial potential for minimizing radiation dose in CTP while preserving diagnostic image quality.