Figure 5.

GRE images obtained from two rat transplanted GH3 prolactinomas grown subcutaneously in the flank, acquired whilst the host breathed air and subsequently carbogen (95% O₂/5% CO₂). Images are typically heterogeneous, with regions of intense signal (long T₂* hence low [deoxyhaemoglobin]) becoming more so during carbogen breathing. Within some of these regions, intensity increases can be observed for structures that are attributed to large tumor blood vessels. Other regions giving rise to little or no signal (short T₂* hence higher [deoxyhaemoglobin]) are unaffected by carbogen breathing and probably correspond to areas of either low blood flow/hypoxia or necrosis, though this has still to be addressed. These data are from work performed by S. Robinson, with grateful acknowledgement to Prof. J.R. Griffiths.