Density resolution of proton computed tomography.
Conformal proton radiation therapy requires accurate prediction of the Bragg peak position. Protons may be more suitable than conventional x-rays for this task since the relative electron density distribution can be measured directly with proton computed tomography (CT). However, proton CT has its own limitations, which need to be carefully studied before this technique can be introduced into routine clinical practice. In this work, we have used analytical relationships as well as the Monte Carlo simulation tool GEANT4 to study the principal resolution limits of proton CT. The noise level observed in proton CT images of a cylindrical water phantom with embedded tissue-equivalent density inhomogeneities, which were generated based on GEANT4 simulations, compared well with predictions based on Tschalar's theory of energy loss straggling. The relationship between phantom thickness, initial energy, and the relative electron density resolution was systematically investigated to estimate the proton dose needed to obtain a given density resolution. We show that a reasonable density resolution can be achieved with a relatively small dose, which is comparable to or even lower than that of x-ray CT.
Schulte
Reinhard W
RW
Department of Radiation Medicine, Loma Linda University Medical Center, Loma Linda, California 92354, USA. rschulte@dominion.llumc.edu
Bashkirov
Vladimir
V
Klock
Márgio C Loss
MC
Li
Tianfang
T
Wroe
Andrew J
AJ
Evseev
Ivan
I
Williams
David C
DC
Satogata
Todd
T
D000465:Algorithms; D004583:Electrons; D007091:Image Processing, Computer-Assisted; D015233:Models, Statistical; D009010:Monte Carlo Method; D019047:Phantoms, Imaging; D011522:Protons; D011829:Radiation Dosage; D011874:Radiometry; D011879:Radiotherapy Dosage; D020266:Radiotherapy, Conformal / Q000379:methods*; D012984:Software; D014054:Tomography / Q000379:methods*; D015898:Tomography Scanners, X-Ray Computed; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000379:methods*; D014965:X-Rays
D011522:Protons