Prostate MR Spectroscopy in vivo
Supervisor(s): Dr Geoffrey Payne and Professor Nandita DeSouza
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Summary
Prostate cancer is the most prevalent cancer in men in the UK, with about 34,000 new cases per year [1]. Detection at an early stage of disease greatly improves the chances of survival. PSA testing is now becoming more widespread, but while this is the most effective first-pass screening technique currently available it is far from perfect. In particular cancer is not the only reason for elevated PSA, and of the cancers detected many will not be clinically significant. The gold-standard is currently histology of biopsy samples, but these suffer both from sampling error, even when collected under ultrasound guidance, and the Gleason score of the sample is often not sufficient to predict the following behaviour of the cancer.
Magnetic resonance is a method that may be used to obtain anatomical, functional and biochemical information from tissues non-invasively. In particular it has been shown using magnetic resonance spectroscopic imaging (MRSI) that compared with normal prostate, concentrations of citrate are reduced in cancer, while concentrations of choline metabolites are elevated [2, 3]. These measurements are performed using MRI scanners, with the MR images as a basis for anatomical localisation. For spectroscopic measurements the current state-of-the-art achieves a spatial resolution of approximately 6mm. These measurements are non-invasive, take about half an hour in total, and can cover the entire prostate. Several institutions have demonstrated that the inclusion of MRSI in the imaging package adds significantly to the overall sensitivity and specificity of cancer detection. There is also the possibility (as yet unconfirmed) that there are biochemical differences between those tumours that will become aggressive and need treatment, and those that will only grow very slowly and are safe to leave alone. MRS measurements may offer the potential of differentiating tumours of differing biological aggressiveness.
References
- Cancer Research UK website: CancerStats Key Facts on Prostate Cancer
- Rajesh, A., et al. (2007) 3D MR spectroscopic imaging in the evaluation of prostate cancer. Clin Radiol Vol 62, No 10, p921-9
- Scheenen, T.W., et al. (2007) Three-dimensional proton MR spectroscopy of human prostate at 3T without endorectal coil: feasibility. Radiology Vol 245, No 2, p507-16
