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High-resolution x-ray imaging at soft diagnostic energies using a silicon photodiode array
1Imaging Research Laboratories, John P. Robarts Research Institute, London, Ontario, Canada.
Medical Physics
|September 1, 1993
Summary
A silicon photodiode array (PDA) offers high-resolution detection for X-ray computed tomography. This detector shows consistent performance across various X-ray energies, enabling detailed imaging of small objects.
Area of Science:
- Medical Imaging
- Detector Physics
- X-ray Computed Tomography
Background:
- Computed tomography (CT) requires high-resolution detectors for small object imaging.
- Soft diagnostic X-rays are utilized in specific CT applications.
- Silicon photodiode arrays (PDAs) are potential candidates for X-ray detection.
Purpose of the Study:
- To characterize the imaging performance of a linear self-scanned silicon photodiode array (PDA) for small object computed tomography.
- To evaluate the PDA's response to soft diagnostic X-ray spectra.
- To assess the PDA's suitability for high-resolution X-ray imaging applications.
Main Methods:
- Characterization of PDA imaging performance using X-ray spectra from 24 to 69 kVp.
- Measurement of modulation transfer function (MTF) up to 40 cycles/mm via double sampling.
- Assessment of detective quantum efficiency (DQE) across different X-ray energies and spatial frequencies.
- Evaluation of silicon detector effective thickness and energy required for electron-hole pair generation.
- Demonstration of CT image generation using a third-generation reconstruction algorithm.
Main Results:
- The PDA achieved high spatial resolution, with MTF measured to 40 cycles/mm.
- MTF showed minimal energy dependence, with a 10% value at 28 cycles/mm.
- Detective quantum efficiency (DQE) ranged from 1.5% to 0.4% and decreased with increasing spatial frequency.
- Effective detector thickness was 22 microns, and 4.6 eV generated an electron-hole pair.
- No radiation damage observed after 5000 R exposure.
- Successful generation of CT images for various phantoms and biological samples.
Conclusions:
- The linear self-scanned silicon photodiode array is a viable high-resolution detector for small object X-ray computed tomography.
- The PDA exhibits stable imaging performance across relevant X-ray energy spectra.
- The detector's characteristics support its use in detailed imaging of small structures and biological specimens.