6 Nuclear Medicine Physics
scattering, attenuation, and dead time) or to other sources such as patient
movement are also considered and some solutions are indicated.
The techniques most commonly used to process data in NM are presented,
including the preprocessing of raw data acquired before image reconstruction
(e.g.,corrections for intrinsic efficiencyvariations, geometry, deadtime, decay,
arc, scatter, attenuation, and various other corrections).
Both two- and three-dimensional analytic and iterative image reconstruc-
tion algorithms are described, and a short description of rebinning methods
is included. The chain of different data processing sequences, from raw data
to reconstructed images, is explained in relation to NM techniques (PET
and SPECT). The real possibilities of extracting quantitative information in
NM functional imaging studies and the necessary correction techniques,
particularly in PET, are analyzed.
The new challenge of PET–CT is considered, particularly within the context
of new nuclear oncology methodologies. The evolution of NM methods has
led to an increasing number of studies in nuclear oncology, related to an
improved understanding of the molecular mechanisms that are the basis of
malignant transformation, from the alterations associated with innumerable
metabolic steps to angiogenesis, hypoxia, and various genetic alterations and
modifications in the cells. This chapter demonstrates how every step in this
process can be evaluated with the aid of NM, obtaining information not only
from the metabolic situation of the tumor tissue being studied but also from
the therapeutic response.
The application of physiological models to the central nervous system
(CNS) is the focus of the final part of this chapter, which also considers
the anatomy, physiology, and pharmacology of the CNS, particularly the
brain, in terms of understanding self-regulating mechanisms (including the
individual–environmentrelationship) and the progression of pathologies that
afflict brain tissues in all phases of human life. The anatomy of the CNS is
briefly described, and the crossing of the blood and neuronal tissue barriers is
explained, with important historical references that reflectthe evolution of the
concept of the hematoencephalic barrier. The neuronal intercommunication
systems are introduced in their common form among neurotransmitters, with
reference to the synthesis, liberation, and neuronal recapture of the neuro-
transmitteras well as its action at postsynapticreceptorlevel.As an interesting
and practical supplement, references are made to the most important clini-
cal applications of methods using radionuclides for the purpose of collecting
information on neurological disease mechanisms and evaluating the response
to existing and new medication. Finally, physiological models are considered
in relation to clinical applications, in general NM and CNS diseases.
Chapter 7 presents an introduction to biological systems theory and NM
methods as systems theory procedures as well as aspects of kinetic modeling.
This chapter first considers the general properties of biological systems,
their elements and relationships with the external medium, feedback and
self-regulation, open and closed systems, homeostasis, and entropy and