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Figure 2. Behaviour of NMR signal intensity in response to a bolus intravenous dose of paramagnetic contrast agent. The signal intensity was derived from the tumour that had previously been outlined. The T1 weighted sequence records a rise in signal intensity due to shortening of the spin-lattice relaxation time of water protons. With a T2* weighted sequence there is a transient loss of signal intensity due to the sequence detecting a first pass effect of the contrast agent. The rapid change in the local magnetic fields induced by the first pass of contrast agent induces a strong susceptibility effect. The area under the T2* curve is theoretically related to the blood volume in the region of interest.
