Research Projects
The major research interest of our lab is to develop new detector technologies for medical imaging and investigate their performance in advanced clinical applications. During recent years, we have been investigating the feasibility of a large area flat-panel imager with avalanche gain. It will provide quantum noise limited performance down to a single x-ray photon, and permit substantial image quality improvement for low-dose x-ray projection and tomographic imaging applications.
Digital Breast Tomosynthesis & Clinical Studies
The Department of Radiology at Stony Brook University is a clinical trial site (the second in the US) for the digital breast tomosynthesis option of Siemens’ Inspiration mammography system. Since 2006, we have been conducting physics research on the optimization of image acquisition geometry, detector operational mode, x-ray beam quality and reconstruction algorithms for improving lesion conspicuity in the reconstructed image slices. This research has been supported by Siemens and a Baldwin Breast Cancer Research Award.
Comparison of Lesion Conspicuity and Dose in Breast Tomosynthesis with Minimal vs. Standard Compression
The objective of the present study is to demonstrate that a decrease in compressive force to less than 40% of that used in standard mammography and tomosythesis does not result in any significant reduction in lesion conspicuity. Studies will be performed on the Siemens MAMMOMAT Inspiration prototype Digital Breast Tomosynthesis system.
PI: Paul Fisher, M.D.
Combined Contrast Enhanced Digital Mammography (CEDM) and Digital Breast Tomosynthesis (DBT) for Improved Diagnosis of Breast Cancer
We are investigating the use of an iodinated radiocontrast agent to improve lesion conspicuity in digital mammography, combined with digital breast tomosynthesis to improve the diagnosis of breast cancer. Images are acquired on the Siemens MAMMOMAT Inspiration prototype Digital Breast Tomosynthesis system that has been modified to support imaging at x-ray energies higher than those typically used in mammography.
PI: Paul Fisher, M.D.
Detector Physics
Optimization of direct conversion flat-panel mammography detectors for digital breast tomosynthesis
Our expertise in the detector physics of direct conversion flat-panel detectors has given us the unique opportunity to collaborate with detector manufacturers for optimization of detector structure, material and post-processing techniques to improve the low-dose and high-speed imaging performance of full-field digital detectors for their application in digital breast tomosynthesis. Digital breast tomosynthesis (DBT) is a 3D imaging modality that acquire a series of projection images of a compressed breast from different angles and reconstructs image slices that are parallel to the detector. This work has been supported by the US Army Breast Cancer Research Program through an IDEA award, and the NIH through an R01 University-Industry partnership grant.
Development of the next generation flat-panel imager with avalanche gain: SHARP-AMFPI
One of the remaining problems of existing flat-panel imagers is its poor low-dose performance in fluoroscopy (or other applications such as cone-beam CT and tomosynthesis). This is due to the degradation effect of detector electronic noise. We are investigating the feasibility of a new flat-panel imager with avalanche gain, which we call SHARP-AMFPI (Scintillator HARP Active Matrix Flat Panel Imager). The signal is amplified through avalanche multiplication in amorphous selenium (a-Se) HARP (High gain Avalanche Rushing Photoconductor) so that even the signal due to a single x-ray interaction can overcome the electronic noise of AMFPI. Furthermore, the avalanche gain can be turned off during high dose radiographic imaging so that the detector response will not be saturated. This detector promises to deliver a wide dynamic range (from a single x-ray photon to raw exposure in radiography), making it ideal for R/F interventional procedure, cone-beam CT and other advanced clinical applications of flat-panel imagers. This project is supported by the NIH/NIBIB through a R01 research grant.
Development of amorphous Selenium based photon counting detector for breast imaging
Spectral photon counting detectors (PCDs) with energy resolving capabilities have the potential to significantly outperform conventional energy integrating detectors. We are developing a novel direct conversion amorphous Selenium (a-Se) based photon counting detector (SWAD) at the wafer scale. SWAD utilizes embedded Frisch grids which establish separate non-avalanche absorption (bulk) and avalanche (sensing) regions, achieving tunable avalanche gain and fast unipolar time differential charge sensing. This project is being conducted through collaboration with the Instrumentation Division and Center for Functional Nanomaterial of Brookhaven National Laboratory.
Development of novel multi-layer hybrid flat panel imagers
Direct active matrix flat panel imagers (AMFPIs) using amorphous selenium (a-Se) offer high intrinsic spatial resolution but have limited x-ray quantum efficiency at general radiographic energies due to selenium’s low atomic number. Conversely, indirect AMFPIs using inorganic scintillators typically have superior x-ray quantum efficiency at these energies, but inferior spatial resolution and increased noise due to optical effects in the scintillator. These inherent limitations motivate alternative AMFPI designs to further improve detector x-ray sensitivity and signal-to-noise performance. Towards this goal, we are investigating the x-ray imaging performance of a novel direct-indirect prototype imager referred to as Hybrid AMFPI, which comprises a direct conversion a-Se layer coupled to a scintillator screen via a transparent blocking layer and high voltage electrode.