Experimental realization of fluence field modulated CT using digital beam attenuation

Area of Science:

• Medical Imaging
• Radiological Physics
• Computational Imaging

Background:

• Current CT scanners offer automatic adjustments but lack view-angle-dependent X-ray fluence control.
• Existing beam shaping filters (bowtie filters) provide fixed fluence distributions for different regions.
• There is a need for dynamic control over X-ray fluence distribution during CT acquisition.

Purpose of the Study:

• To experimentally demonstrate the first realization of fluence field modulated CT (FFMCT) using a digital beam attenuator (DBA) in a c-arm geometry.
• To evaluate the dose reduction capabilities and image quality improvements of FFMCT compared to conventional CT.
• To explore novel imaging applications enabled by the DBA, such as volume of interest (VOI) imaging.

Main Methods:

• Developed and implemented a digital beam attenuator (DBA) consisting of ten iron wedge pairs to modulate X-ray fluence.
• Acquired experimental data using a Siemens Zeego c-arm scanner on phantom objects (cylindrical and anthropomorphic).
• Performed scans with and without the DBA for comparison, including a VOI imaging scan, and developed necessary data correction algorithms.

Main Results:

• Demonstrated the feasibility of FFMCT using the DBA device in a c-arm CT system.
• Achieved dose reductions of up to 3.6 times relative to conventional 'flat field' CT scans.
• Observed significant improvements in image noise uniformity and enabled regionally enhanced signal-to-noise ratio via VOI imaging.

Conclusions:

• FFMCT implemented with a DBA is feasible for clinical translation, offering substantial dose reduction.
• The DBA technology maintains or improves image quality while reducing patient radiation exposure.
• The DBA facilitates advanced imaging techniques like photon counting and targeted VOI imaging, expanding CT's capabilities.