Poster Session

P354. Detection of lactate and other metabolites in ovarian tumours using 1H NMR Spectroscopy

Nur Nahdiyat (ID), Ross Maxwell (GB)

[Nahdiyat] Cipto Mangunkusumo Hospital, Jakarta, [Maxwell] Newcastle University, Newcastle

A new biomarker is needed to assess treatment response in ovarian tumours. Lactate concentration is a good indicator of tumour malignancy, which can be identified using MR spectroscopy. Aims: To observe lactate and other metabolites in ovarian tumours and find a robust method for lipid suppression. Methods: Metabolic profiles of tumours were observed by single voxel (PRESS) and multivoxel (CSI) 1H MRS in subcutaneous A2780 xenograft tumours in mice. Phantom measurements were used to optimise the technique. Muscle was selected as reference tissue and an ex vivo lactate assay was performed. An inversion recovery (IR) pulse was evaluated for lipid suppression. Results: A negative peak at 1.4ppm, consistent with lactate, was found using PRESS with TE1=128 ms in tumour models. Choline and glycine were also detected. Lactate concentrations (7-15 mM) were confirmed by ex vivo analysis. Using an IR pulse compromised water suppression. Discussion: The negative peak chemical shift, suggested it could originate from alanine (1.45ppm) rather than lactate (1.33ppm). Ex vivo analysis showed that relative lactate content of the tumours (n=3) was similar to that observed by in vivo MRS. In one tumour, lactate contaminated with lipid was observed. Lactate could not be reliably identified in CSI due to inconsistent phasing and lipid contamination. Conclusion: The choice of radio-frequency coil, pulse sequence, and echo time were optimised but an IR pulse was not helpful in detecting lactate. Applying PRESS to ovarian tumours and skeletal muscle showed distinct metabolite patterns where signal consistent with lactate or alanine could be identified.