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Clinical Imaging of Microwave Mammography
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Large area CMOS active pixel sensor x-ray imager for digital breast tomosynthesis: Analysis, modeling, and
Chumin Zhao1, Jerzy Kanicki1, Anastasios C Konstantinidis2
1Solid-State Electronics Laboratory, Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan 48109.
Medical Physics
|November 2, 2015
Summary
This study shows that a 75 μm pixel pitch CMOS APS x-ray imager can detect microcalcifications in digital breast tomosynthesis (DBT) with reduced radiation dose. The imager achieved high detective quantum efficiency (DQE) and improved contrast-to-noise ratio (CNR) compared to existing systems.
Area of Science:
- Medical Imaging
- X-ray Detector Technology
- Digital Breast Tomosynthesis
Background:
- Complementary metal-oxide-semiconductor (CMOS) active pixel sensor (APS) technology offers low electronic noise for advanced x-ray imaging.
- Shrinking pixel pitch in CMOS APS imagers is crucial for detecting microcalcifications and potentially reducing patient radiation dose in digital breast tomosynthesis (DBT).
Purpose of the Study:
- To characterize and model the imaging performance of a large-area CMOS APS x-ray imager with a 75 μm pixel pitch.
- To evaluate the imager's suitability for microcalcification detection in DBT and assess potential mean glandular dose (MGD) reduction.
Main Methods:
- Imaging performance of a 29x23 cm² CMOS APS x-ray imager (Dexela 2923 MAM) with 75 μm pixel pitch was characterized using broadband and synchrotron radiation.
- A cascaded system model was developed and validated against experimental data (MTF, NPS, DQE) for both high and low full well (LFW) modes.
- Contrast-to-noise ratio (CNR) for microcalcifications (165-400 μm) was extracted at various MGDs, and the impact of electronic noise was evaluated.
Main Results:
- The LFW mode demonstrated superior detective quantum efficiency (DQE) at low air kerma, making it suitable for DBT.
- High DQE (>0.7 at 0.5 lp/mm, ~0.3 at Nyquist frequency ~6.7 lp/mm) was achieved in LFW mode under typical DBT conditions (28 kVp).
- Microcalcifications (165-400 μm) were resolvable at MGDs of 0.3-1 mGy, and the imager showed a ~10-fold increase in CNR at a lower MGD compared to a prototype DBT system.
Conclusions:
- The Dexela 2923 MAM CMOS APS x-ray imager exhibits high imaging performance up to 6.7 lp/mm, enabling the visualization of 165 μm microcalcifications due to its 75 μm pixel pitch.
- The imager facilitates improved contrast-to-noise ratio (CNR) for microcalcification detection at reduced mean glandular doses (MGDs).
- This technology holds promise for dose reduction in digital breast tomosynthesis (DBT) while maintaining or enhancing diagnostic image quality.
