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Radiation Dose Reduction with Optimal Energy Weighting for a Prototype Energy-Resolved Photon-Counting Si Strip Detector


A Lam Ng

A Lam Ng1*, h ding1, H Cho1, W Barber2, J Iwanczyk2, S Molloi1, (1) University of California, Irvine, Irvince, CA, (2)Dx-ray Inc., Northridge, CA

TH-A-103-6 Thursday 8:00AM - 9:55AM Room: 103

Purpose: To develop simulation and experimental methods for optimal energy weighting to reduce dose and enhance contrast for the detection of microcalcification, soft-tissue lesions and iodine-contrast objects using a prototype energy-resolved photon-counting Si strip CT detector.

Methods:A prototype energy-resolved photon-counting Si strip CT detector was investigated for optimal energy weighting. The Si strip detector has 256 pixels with 100 μm pitch. It was placed in an edge-on geometry which results in an effective attenuation length of 0.6 mm. A tungsten anode X-ray spectrum of 65 kVp with 2 mm Al filter was used. Glandular and Adipose equivalent phantoms were constructed using PMMA and polyethylene. Water, calcium hydroxyapatite and iodine with different concentrations were used to simulate soft tissue lesion, microcalcification and contrast material in breast tissue. A simulation package was generated to reconstruct images from charge-integrated and energy-resolving photon-counting detectors. Energy weighting factors based on projection and image based methods were used in the four energy bins to enhance contrast. Different energy thresholds were investigated based on iodine K-edge, equal counts per bin, and equally spaced bins. CNR was computed to compare image quality between methods.

Results:Simulation results indicate that using an optimized energy weighting image reconstruction improves CNR for water (30%-40%), for hydroxyapatite (30% -50%), and for iodine (35%-40%) in comparison of those images from charge-integrated reconstruction.

Conclusion:The implementation of energy weighting methods in image reconstruction for the prototype energy-resolved photon-counting Si strip CT detector can improve CNR or reduce radiation dose. This technique can potentially be used for detection of microcalcification, soft-tissue lesions and iodine-contrast object in a spectral breast CT system.

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