Biomedical Engineering Reference
In-Depth Information
Chapter 25
Optimized Molecular Imaging through
Magnetic Resonance for Improved Target
Definition in Radiation Oncology
Dzevad Belkic and Karen Belkic
Abstract
Magnetic resonance spectroscopy (MRS) and spectroscopic imaging
(MRSI) are a key modality in radiation oncology for brain and prostate tumors.
Improved target definition for radiation therapy (RT) and distinction of changes
due to RT from tumor recurrence have been greatly aided by MRSI. However,
current applications of MRS/MRSI have limitations due to mainly the fast Fourier
transform (FFT) and noise. Optimization of MRS/MRSI is possible by more
advanced signal processing via the fast Pade transform (FPT). As a quotient of
two polynomials, the FPT markedly improves the resolution of
in vivo
MR time
signals encoded from the brain and reliably reconstructs all spectral parameters
of metabolites. Due to high spectral density with numerous multiplet resonances,
MRS/MRSI of the prostate is exceedingly difficult. The FPT applied to MRS data
as encoded from normal and malignant prostate resolves all the genuine resonances,
including multiplets and closely overlapping peaks. With synthesized time signals,
the FPT fully retrieves all the input spectral parameters with machine accuracy. Such
super-resolution is achieved without fitting or numerical integration of peak areas,
thereby yielding the most accurate metabolite concentrations. This needs only short
signal lengths that imply improved signal-to-noise ratios. These ratios are further
enhanced by eliminating “noisy” Froissart doublets as confluent pole-zero pairs.
Hence, only the true information is reconstructed by the FPT, as the prerequisite for
clinically meaningful interpretations of
in vivo
time signals. With these long sought
capabilities of advanced Pade-based signal processing, MRS and MRSI are poised
to reach their full potential in radiation oncology.
