Dr. Alexander L. C. Kwan Profile

Dr. Alexander L. C. Kwan

SPIE Involvement:

Author

Publications (6)

Proceedings Article | 21 March 2007 Paper

Evaluation of noise power spectra of CT images

Kathrine Metheany, Alexander Kwan, John Boone

Proceedings Volume 6510, 65101S (2007) https://doi.org/10.1117/12.708308

KEYWORDS: Computed tomography, Bone, Scanners, Image filtering, Spatial frequencies, X-ray computed tomography, Interference (communication), Photons, Signal detection, Cancer

Read Abstract +

Proceedings Article | 15 March 2007 Paper

Evaluation of the spatial resolution of a dedicated breast CT system using computer simulation

Kai Yang, Alexander Kwan, John Boone

Proceedings Volume 6510, 65101P (2007) https://doi.org/10.1117/12.713286

KEYWORDS: Modulation transfer functions, Sensors, Computer simulations, X-rays, Computing systems, X-ray computed tomography, Breast, Spatial resolution, X-ray detectors, Scanners

Read Abstract +

Proceedings Article | 20 April 2005 Paper

Evaluation of an optically coupled CCD digital radiography system

J. Seibert, Alexander Kwan, John Boone, Paul Brown, Robin Winsor

Proceedings Volume 5745, (2005) https://doi.org/10.1117/12.595751

KEYWORDS: Sensors, Modulation transfer functions, Scintillators, X-rays, Imaging systems, CCD image sensors, Radiography, Charge-coupled devices, Quantum efficiency, Spatial frequencies

Read Abstract +

Proceedings Article | 20 April 2005 Paper

Contrast-enhanced dual-energy digital subtraction mammography: optimization of the beam energy

Alexander Kwan, John Boone, Huong Le-Petross, Karen Lindfors, J. Seibert, John Lewin

Proceedings Volume 5745, (2005) https://doi.org/10.1117/12.595887

KEYWORDS: Digital mammography, Breast, Mammography, Iodine, Scanners, Tissues, Magnetic resonance imaging, Imaging systems, Tumors, X-ray computed tomography

Read Abstract +

The implementation of contrast-enhanced dual-energy digital subtraction mammography may lead to better identification of breast tumors, and thus provide a lower cost and more widely available alternative to breast MRI. This technique involves the acquisition of low- and high-energy images after the IV administration of iodinated contrast agent. In this study, the effect of the beam energy (kVp) was examined using the CNR²/dose metric, where CNR is the contrast-to-noise ratio and dose implies the mean glandular dose. The mean glandular dose was calculated using parameterized normalized glandular dose coefficients (DgN), which allowed the computation of the mean glandular dose for the modeled spectra considered in this study, coupled with incident kerma measurements. Optimization studies were performed using a dedicated cone-beam breast CT scanner designed and fabricated in our laboratory, with the system operating in stationary imaging mode. A flat tissue-equivalent phantom (7.5 cm in thickness) was placed at the isocenter of the scanner, and an air gap of 34.5 cm was used in lieu of a grid. Dilute iodine-based contrast agent was introduced into the phantoms using plastic vials. Data were acquired from 40 to 90 kVp at 10 kVp intervals. Due to the low mA available on the breast CT system, a large number of images (1000) were acquired in fluoroscopic mode, which allowed us to match the dose and noise properties for each kVp combinations by changing the number of images used for averaging. Preliminary results demonstrate that the best CNR2/dose is achieved with a 50 kVp low-energy image and a 90 kVp high-energy image. Consequently, radiation doses for contrast-enhanced mammography should be far lower than regular mammography. Since the spatial resolution requirements should also be lower than regular mammography, dual-energy contrast-enhanced mammography, when performed using the optimal technique factor, may indeed provide very similar diagnostic information as breast MRI but at significantly reduced costs.

Proceedings Article | 20 April 2005 Paper

Performance assessment of a pendant-geometry CT scanner for breast cancer detection

John Boone, Alexander Kwan, Thomas Nelson, Nikula Shah, George Burkett, J. Seibert, Karen Lindfors, Gerhardt Roos

Proceedings Volume 5745, (2005) https://doi.org/10.1117/12.595706

KEYWORDS: Breast, Scanners, X-ray computed tomography, Breast cancer, Modulation transfer functions, Sensors, Mammography, Computed tomography, X-rays, X-ray detectors

Read Abstract +

Proceedings Article | 6 May 2004 Paper

Progress in the development of a dedicated breast CT scanner

Alexander Kwan, Nikula Shah, George Burkett, J. Anthony Seibert, Karen Lindfors, Thomas Nelson, John Boone

Proceedings Volume 5368, (2004) https://doi.org/10.1117/12.537029

KEYWORDS: Breast, Sensors, Scanners, X-ray computed tomography, X-rays, Modulation transfer functions, Optical filters, X-ray detectors, Fourier transforms, Breast cancer

Read Abstract +

Showing 5 of 6 publications

View contact details

UPDATE YOUR PROFILE

Is this your profile? Update it now.

Sign into your SPIE.org account

Don’t have a profile and want one?

Create an account on SPIE.org

Keywords/Phrases

Search In:

Publication Years