Functional magnetic resonance imaging for defining the biological target volume

Abstract

Morphology as demonstrated by CT is the basis for radiotherapy planning. Intensity-modulated and adaptive radiotherapy techniques would greatly benefit from additional functional information allowing for definition of the biological target volume. MRI techniques include several which can characterize and quantify different tissue properties and their tumour-related changes. Results of perfusion MRI represent microvascular density and permeability; MR spectroscopy depicts particular metabolites; diffusion weighted imaging shows tissue at risk and tumour cellularity; while dynamic 3D acquisition (4D MRI) shows organ motion and the mobility of tumours within them.

Vascular oxygen content and the tissue oxygenation-A theoretical analysis

“…34 The present study expanded from our previous model 28 to include the effects of distributions of vascular oxygenations in order to study the relationship to tissue oxygenation and the factors that may influence it. Functional information on tumor vasculature could be available from several techniques, 22,35,36 but the accuracy of cor- relations with the parameters thought to influence directly tissue response to radiation, mainly the tissue oxygenation, has to be investigated before such information is used for predictive purposes in a clinical environment. Previous analyses of tissue oxygenations have highlighted the complex relationship that is to be expected between the oxygenation of the blood vessels and that of the cells in the tissue, 28 but did not attempt to correlate them quantitatively.…”

Hypofractionated Boost to the Dominant Tumor Region With Intensity Modulated Stereotactic Radiotherapy for Prostate Cancer: A Sequential Dose Escalation Pilot Study

“…However, recent progress in functional MRI and 11 C or 18 F marked tracers such as choline or acetate positron emission tomography (PET) may help to accurately define a biological target volume within the prostate, thus optimizing tumor dose ''painting'' (34)(35)(36)(37). Use of PET imaging of tumor hypoxia with specific radiotracers such as 64 Cu-ATSM or 18 F-FMISO may further optimize biological targeting by defining Hypofractionated boost with intensity modulated stereotactic radiotherapy for prostate cancer d R. MIRALBELL et al 5 5 relatively radioresistant hypoxic regions within the tumor volume where dose escalation may be required to optimize tumor control (38).…”

Diffusion‐weighted MRI for tumour volume delineation: Comparison with morphological MRI

“…Image‐guided cancer therapeutic methodologies, such as radiation therapy, mainly rely on morphological information from computed tomography and magnetic resonance imaging (MRI), optionally supplemented by metabolic information from positron emission tomography (PET). Additionally, recent developments in MRI methods, such as diffusion‐weighted MRI (dwMRI), dynamic contrast enhanced MRI and high‐speed temporo‐spatial MRI, may further complement morphological imaging with biological, functional and temporal information 1 . Therefore, our continuing intent is to investigate dwMRI as a tool for radiotherapy and radiobiology.…”

“…Additionally, recent developments in MRI methods, such as diffusion-weighted MRI (dwMRI), dynamic contrast enhanced MRI and high-speed temporo-spatial MRI, may further complement morpho-logical imaging with biological, functional and temporal information. 1 Therefore, our continuing intent is to investigate dwMRI as a tool for radiotherapy and radiobiology. dwMRI assesses the random molecular motion of water in tissues.…”