title: Modification of tumour perfusion and oxygenation monitored by gradient recalled echo MRI and 31P MRS.
abstract: Gradient recalled echo (GRE) 1H images can be used to monitor changes in blood oxygenation via the dephasing effects of paramagnetic deoxyhaemoglobin (Hb). We have modulated the blood flow/oxygenation of GH3 rat tumours by i.v. calcitonin gene-related peptide (CGRP) or carbogen (95% O2, 5% CO2) inhalation, and obtained GRE 1H images interleaved with 31P spectra before, during and after the insult. With CGRP the GRE image intensity decreased (6/10) by > 10% with a concomitant 40% decrease (4/4) in beta NTP/P1 and a small decrease in pH. Both the image intensity and 31P spectra returned to near their pre-CGRP levels after 50 min, consistent with a transient episode of hypoxia. Carbogen breathing (5/5) caused > 40% increases in average GRE image intensity, with no significant changes in the 31P spectra (4/4). Three-dimensional GRE images were obtained to confirm that a T2* increase, rather than just an 'in-flow' effect due to increased blood flow, was responsible for the GRE enhancement. Increases in average image intensity > 40% were observed for the three-dimensional GRE images (2/2), indicating a T2* increase. Using Hb as an endogenous contrast agent, the high sensitivity of the GRE technique may provide a method of monitoring heterogeneous tumour perfusion and oxygenation, both in the laboratory and the clinic.
authors.affiliation: Division of Biochemistry, St George's Hospital Medical School, London, UK.
authors.forename: F A
authors.initials: FA
authors.lastname: Howe
authors.forename: S P
authors.initials: SP
authors.lastname: Robinson
authors.forename: J R
authors.initials: JR
authors.lastname: Griffiths
mesh_terms: D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000494:pharmacology; D002245:Carbon Dioxide / Q000494:pharmacology; D008279:Magnetic Resonance Imaging / Q000379:methods; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D010084:Oxidation-Reduction; D010100:Oxygen / Q000097:blood* / Q000494:pharmacology; D010477:Perfusion; D010758:Phosphorus; D010911:Pituitary Neoplasms / Q000098:blood supply* / Q000378:metabolism*; D015175:Prolactinoma / Q000098:blood supply* / Q000378:metabolism*; D051381:Rats; D011920:Rats, Inbred WF
chemical_list: D002245:Carbon Dioxide; D010758:Phosphorus; C011700:carbogen; D015740:Calcitonin Gene-Related Peptide; D010100:Oxygen