In diagnostic radiology it is a common interest of patient and medical staff to keep the exposure as low as reasonably
achievable (ALARA). In spite of this task being well known there is no consensus about how low the exposure for a
specific diagnostic examination can be. The methods presented in this paper allow for the mathematical determination of
the lowest exposure necessary to perform basic, well defined imaging tasks in digital radiography. The model quantifies
how different demands on the result influence the necessary exposure. Dependences on parameters describing the beam
quality used and the detector are implemented into the model. A strong rise of the necessary exposure to detect a certain
contrast of lower amplitude or with higher certainty was determined. The effects of a change of the energy of the
irradiation are as a first step investigated via the connected change of the transmission of a main absorber. By
specification of the specimen to be observed the result is connected to beam energies which can be correlated with the
energy dependent response of a realistic detector system. The calculations give basic information about the best exposure
in a simplified view of patient dimensions and diagnostic needs. Especially in pediatric radiology optimized adaptations
to the patient and the clinical question are expected to take great effects due to the great variations of patient sizes.
KEYWORDS: Monte Carlo methods, Polymethylmethacrylate, Tomography, Data modeling, Signal to noise ratio, X-rays, Aluminum, Radiography, Image resolution, Sensors
Thoracic radiography was simulated making use of a virtual pediatric model created from tomographic data
(voxelphantom) of a child eight weeks old. The dataset was scaled down to fit the dimensions of a premature newborn.
The simulation allows a quantitative and spatially resolved analysis of the x-ray image generation. The transmission
behavior of different anatomical regions present in the voxelphantom was compared to the output of the simulation of a
step-like phantom made from aluminum and PMMA. The step like structure of the simulated model can be easily built
and statements about its x-ray related behavior can be directly validated by means of experiments. A thin contrast plate
was placed on each step to make the determination of dependences e.g. between the applied radiation energy and the
contrast to noise ratio possible.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.