PROCEEDINGS OF THE 7 INTERNATIONAL ... - Fizika

MEDICAL PHYSICS IN THE BALTIC STATES 7 (2009)
Proceedings of the International Conference “Medical Physics 2009”
9 - 10 October 2009, Kaunas, Lithuania
RECENT ADVANCES AND TRENDS IN
MEDICAL X-RAY AND MOLECULAR IMAGING
Sören MATTSSON
Medical Radiation Physics Malmö, Lund University, Malmö University Hospital, SE-205 02 Malmö, Sweden
Abstract: This paper is intended to give an overview of clinically used imaging methods with special reference to
digital techniques and 3D techniques for X-ray and nuclear medicine/molecular imaging such as CT, SPECT and PET.
The paper will focus on recent advances and trends.
Keywords: Medical imaging, tomography, X-ray, CT, PET, MRI, tomosynthesis, hybrid imaging
1. Introduction
Medical imaging is an invaluable part of modern health
care. It is used for disease detection, classification,
prognostic staging and to validate therapeutic response.
In fact, recent advances in imaging technology have
redefined how physicians diagnose and treat some of
the most life threatening diseases like cancer and heart
disease, and have nearly eliminated the need for
exploratory surgery. Good images are the base for
planning of therapies such as surgery and radiotherapy.
Imaging is also an important instrument for clinical
research, where the requirements for quantitative and
reproducible image data are especially high.
Clinical diagnostic imaging is currently using five
major modalities: 1) Planar X-ray imaging, 2)
computed tomography (CT), 3) magnetic resonance
imaging (MRI), 4) nuclear medicine imaging (using
planar gamma cameras, single-photon-emissioncomputed
tomography (SPECT) and positron-emission
tomography (PET)) and 5) ultrasound.
This paper will concentrate on X-ray and nuclear
medicine imaging – methods that use ionising
radiation. These techniques are currently undergoing
major improvements and a change towards
technologies that facilitate quantitative tomographic
imaging.
2.1 Planar X-rays
2. X-ray imaging
X-ray imaging is still based on the X-ray tube as
radiation source. Tungsten is the most common anode
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material, except for mammography, which use Mo- and
Rh- anodes. Filters of Al, Cu, Mo, and Rh are used to
cut off different parts of the photon energy distribution.
Currently used X-ray tubes are very efficient radiation
sources. They have, however, shortcomings as high
operating temperature. With a new cooling principle
utilizing convective cooling, the need for waiting times
due to cooling has been reduced. Moreover, an
electronic beam deflection system for focal spot
position and size control has opened for advanced
applications. The ongoing nanotechnology based field
emission X-ray source technology (Xintek,
www.xintex.com), enables the generation of radiation
with fine control of the spatial distribution of the Xrays
and temporal modulation of the radiation [1]. The
technology also enables the design of gantry-free
stationary tomography imaging systems with faster
scanning speed and potentially better imaging quality
compared to today’s commercial tomographic systems.
For the detection and imaging of the X-rays transmitted
through the patient, flat-panel detectors have been
developed for use in radiography and fluoroscopy to
replace standard X-ray film, film-screen combinations
and image intensifiers. Current technology use flatpanel
detectors, made from evaporated CsI or Gd2O2S
on a matrix of a-Si photodiodes for higher energies or a
layer a-Se, directly converting the absorbed energy to a
current for low energies (mammography).
The development of detectors for planar X-ray imaging
has resulted in increased detection efficiency without
significant loss of spatial resolution.
The availability of flat panel detector technology has
also stimulated a number of new developments for
tomographic imaging (See section 2.2).