Simultaneous Image Reconstruction and Element Decomposition for Iodine Contrast Agent Visualization in Multienergy...

Area of Science:

• Medical Imaging
• Radiotherapy Physics
• Radiology

Background:

• Iodine contrast agents are crucial for detecting liver tumors during CT simulation for radiotherapy.
• Current cone-beam CT (CBCT) limitations in image quality and contrast dose hinder its use for image-guided radiotherapy.
• Previous development of a multi-energy element-resolved (MEER) CBCT framework offers potential for improved imaging.

Purpose of the Study:

• To investigate the feasibility of using MEER-CBCT for visualizing low-concentration iodine contrast agents.
• To evaluate the performance of MEER-CBCT in detecting iodine compared to standard methods.

Main Methods:

• Developed a MEER-CBCT framework utilizing kVp-switching and a dictionary-based reconstruction algorithm.
• Acquired projection data using sequential 80, 100, and 120 kVp settings with 600 projections.
• Included iodine material in the reconstruction algorithm's dictionary for element-resolved imaging.
• Compared iodine detectability (quantified by contrast-to-noise ratio, CNR) with standard filtered back projection (FBP) CBCT.

Main Results:

• MEER-CBCT demonstrated comparable contrast enhancement to FBP but with significantly higher CNR.
• Standard FBP achieved a CNR of 2.0 (tumor visualization standard) at 2.5% iodine concentration.
• MEER-CBCT achieved the same CNR of 2.0 with a ~6.3 times lower iodine concentration of 0.4%.

Conclusions:

• MEER-CBCT is feasible for visualizing low-concentration iodine contrast agents.
• This technique offers superior contrast-to-noise ratio, enabling detection at much lower iodine doses.
• MEER-CBCT has the potential to improve image guidance in radiotherapy by enhancing tumor visibility with reduced contrast agent requirements.