1. Med Phys. 2010 Oct;37(10):5434-41.

Noninvasive mapping of spontaneous fluctuations in tumor oxygenation using 19F
MRI.

Magat J, Jordan BF, Cron GO, Gallez B.

Biomedical Magnetic Resonance Unit, Louvain Drug Research Institute, Université
Catholique de Louvain, Brussels 1200, Belgium.

PURPOSE: Acute hypoxia (transient cycles of hypoxia-reoxygenation) is known to
occur in solid tumors and may be a poorly appreciated therapeutic problem as it
can be associated with resistance to radiation therapy, impaired delivery of
chemotherapeutic agents, or metastasis development. The objective of the present 
study was to use MR 19F relaxometry maps to analyze the spontaneous fluctuations 
of partial pressure of oxygen (pO2) over time in experimental tumors.
METHODS: The pO2 maps were generated after direct intratumoral administration of 
a fluorine compound (hexafluorobenzene) whose relaxation rate (1/T1) is
proportional to the % O2. The authors used a SNAP inversion-recovery sequence at 
4.7 T to acquire parametric images of the T1 relaxation time with a high spatial 
and temporal resolution. Homemade routines were developed to perform regions of
interest analysis, as well as pixel by pixel analysis of pO2 over time.
RESULTS: The authors were able to quantify and probe the heterogeneity of
spontaneous fluctuations in tumor pO2: (i) Spontaneous fluctuations in pO2
occurred regardless of the basal oxygenation state (i.e., both in oxygenated and 
in hypoxic regions) and (ii) spontaneous fluctuations occurred at a rate of 1
cycle/12-47 min. For validation, the analysis was performed in dead mice for
which acute changes did not occur. The authors thereby demonstrated that 19F MRI 
technique is sensitive to acute change in pO2 in tumors.
CONCLUSIONS: This is the first approach that allows quantitative minimally
invasive measurement of the spontaneous fluctuations of tumor oxygenation using a
look-locker approach (e.g., SNAP IR). This approach could be an important tool to
characterize the phenomenon of tumor acute hypoxia, to understand its
physiopathology, and to improve therapies.


PMID: 21089779 [PubMed - indexed for MEDLINE]