Light Collection Enhancement Analysis for Digital X-Ray Detector Using Gd2O2S:Tb and CsI:Tl Phosphors in Nanoscale Treatment - Atomic Nanoscale Technology in the Nuclear Industry - page 68

compared.with.AMFPI.for.direct.digital.radiography.(Widmer.2008)..Direct.
digital.radiography.(DDR).detectors.are.lat-panel.and.CCD.types..Computed.
radiography.(CR).and.DDR.provide.quality.diagnostic.images..CR.is.a.mature.
technology.while.DDR.is.an.emerging.technology.
The. detection. imagers. typically. use. Gd 2 O 2 S:Tb. or. CsI:Tl. scintillation.
screens. to. convert. the. x-ray. into. visible. photons,. which. are. then. collected.
by. an. underlying. photodetector. array. for. digital. radiographic. and. mam-
mographic. applications.. The. study. investigated. whether. the. inclusion. of. a.
microlens. array. between. the. screen. and. photodetector. may. improve. light.
collection.when.the.photodetector.has.a.small.optical.ill.factor..The.micro-
lens.can.treat.the.nanoscale.light.collections.which.could.be.produced.by.the.
micro-thickness.screen..The.technique.for.modeling.the.modulation.trans-
fer. function. (MTF). from. measurement. obtained. for. Gd 2 O 2 S:Tb. and. CsI:Tl.
scintillation. screens. has. been. reported.. The. measurements. were. obtained.
for. a. number. of. different. mono-. and. polychromatic. x-ray. (energy). spectra..
The. screen. MTFs. were. subsequently. transformed. into. point. spread. func-
tions.(PSFs).and.used.in.a.simulation.of.the.proposed.imaging.system..This.
imaging.system.results.in.a.better.image.with.lower.radiation.exposure.to.
patients.
The.purpose.of.the.project.is.to.produce.better.images.in.mammography.
using.a.microlens.array;.that.is,.a.good.x-ray.imager.detector.as.the.AMFPI.
(Antonuk,.1997a,.1997b).photodetector.is.constructed..In.this.stage,.improved.
ray-tracing. (Shirley. 2000,. Glassner. 1989). and. Monte-Carlo. simulation. are.
done..The.screen,.microlens.array,.and.photodetector.planes.are.also.consid-
ered.. Second,.the.microlens. array. is. designed;. the.transmittance,.focusing,.
and. uniformity. are. measured;. and. the. predicted. and. measured. light. col-
lection. eficiencies. are. compared.. Third,. the. microlens. array. is. matched. to.
AMFPI..Last,.the.comparisons.with.and.without.the.microlens.are.studied.
for.uniform.ield.and.phantom.images..Figure 6.1.shows.the.simpliied.con-
iguration.for.the.microlens.
Lights
Lens
Imager
Substrate
FIGURE 6.1
Simpliied.coniguration.for.microlens.