Date of Award

11-1999

Document Type

Thesis

Degree Name

Master of Science (MS)

Program

Biomedical Engineering

Research Advisor

Herbert D. Zeman

Committee

Frank DiBianca Sanjiy Samant Milan Buncick

Abstract

The purpose of this research was to design a high performance digital portal imaging
system, using a transparent x-ray scintillator coupled to a cooled CCD camera. Theoretical
analysis using Monte Carlo simulation was performed to calculate the QDE, SNR and DQE of
the system. A prototype electronic portal imaging device (EPID) was built, using a 12.7 mm
thick, 20.32 cm diameter, CsI (Tl) scintillator, coupled to an Astromed ® liquid nitrogen cooled
CCD TV camera. The system geometry of the prototype EPID was optimized to achieve high
spatial resolution. Experimental evaluation of the prototype EPID was performed, by
determining its spatial resolution, contrast resolution, depth of focus and light scatter. Images of
phantoms, animals and human subjects were acquired using the prototype EPID and were
compared with those obtained using conventional and high contrast portal film and a commercial
EPID. An image processing protocol was developed. The protocol was comprised of
preprocessing, noise removal and image enhancement algorithms. An adaptive median filter
algorithm for the removal of impulse noise was developed, analyzed and incorporated into the
image processing protocol.

Results from the theoretical analysis and experimental evaluation have indicated that the performance of the CsI (Tl) - CCD system is comparable or superior to that of current commercial and experimental portal imaging technologies, such as high contrast portal film, commercial TV camera based EPIDs, and amorphous silicon based flat panel EPIDs.

DOI

10.21007/etd.cghs.1999.0277

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