An Investigation of the INTERPRET Spectra using Automated Pattern Recognition Techniques Rosemary Tate St George’s Hospital Medical School,

Questions 1. Can the most common types of tumour be distinguished using single voxel spectroscopy? 2. If so, which spectral features provide the best discrimination? 3. Do these features generalise across centres? 4. Can spectra from different centres be combined?

Data St George's Hospital, London 35 patients 13 glioblastomas, 6 grade II astrocytomas 4 grade III astrocytomas, 5 meningiomas, 7 metastases STEAM 30 GE PROBE 2048 pts SW 2500 IDI Bellvitge, Barcelona 77 patients 24 glioblastomas, 11 grade II 14 grade III astrocytomas, 13 meningiomas, 20 metastases PRESS 30 Philips 512 pts SW 1000

Automated Spectral processing Frequency modulation correction, water resonance filtering chemical shift scale adjustment line broadening 0.8 Hz Fourier transformation Zero water region magnitude spectrum Interpolate to same resolution select intensities between ppm normalise vector to unit length

Mean Magnitude (PRESS) Spectra from IDI Barcelona

Pattern Recognition Analysis Correlation analysis for feature selection Principal component analysis Linear discriminant analysis - with leave one out for testing.

Answers 1. Can the most common types of tumour be distinguished? 3 groups benign (meningiomas) low grade aggressive (metastases and glioblastomas) 3 groups discriminant analysis ~98% correctly classified

astII gbm met mn Discriminant scores for 3 groups “aggressive’’(metastasis (met) glioblastoma (gbm)), meningiomas (mn) and low grade(astII) 3 group discrimination: aggressive/low grade/benign dscore1dscore1 dscore 2

Answers 1. Distinguishing between tumours Grading Astrocytomas astII and astIII vs. glioblastomas ~ 90%, distinguishing between the 3 grades ~75%

Discriminant scores for the three grades of astrocytomas astII gbm astIII dscore1dscore1 dscore 2

Answers Which spectral features provide good discrimination? Combination of selected spectral intensities or Principal Components calculated from the whole spectrum Do features generalise? Yes, most of them

Spectral intensities representing lipid and glutamine(+) gbm astII mn lipid g glutamineglutamine IDI SGH *

Values of pts from lipid and myoinostol region for astrocytic tumours. astII gbm astIII IDI SGH * myoinosItolmyoinosItol lipid

Answers Can spectra from different centres be combined for classification? Looks promising

1st 2 Principal Components of the IDI spectra gbm met astII mn astIII PC 1 2 PC2PC2

1st 2 Principal Components of the SGH spectra weights calculated using the IDI spectra gbm met astII mn astII PC2PC2 PC1

IDI SGH * gbm met astII mn astII PC2PC2 PC 1

astII 2nd and 3rd Principal Components of the IDI spectra for astrocytoma grade II and III.

IDI SGH * astII 1st 2 Principal Components of the IDI and SGH spectra weights calculated using the IDI spectra

Conclusions 1. Magnitude spectra give good results. 2. PCA gives excellent data compression for these groups of short-echo spectra 3. Individual intensity values give good separation between groups. 4. Most features generalise across centres.

Next Questions to be answered 1. What type of normalisation should we use? 2. What to do about uncommon groups? 3. Mets vs.. GBMs? 4. What other information can we use - e.g image and clinical information? 5.Measures of confidence? 6. Quality control.

Example spectra - glioblastoma and meningioma. Normalised using unsuppressed water

Bottlenecks Lack of test data Problems with processing - e.g phasing Software for the GUI

Acknowledgements SGHMS John Griffiths, Franklyn Howe, Christophe Ladroue, Alison Loosemore, Mary Murphy, Tony Bell, Peter Wilkins, Sarah Barton UOS Joshua Underwood, Dionisio Acosta, Rose Luckin, Des Watson Barcelona Carles Arus, Margarida Julia, Mohamed Zakari, Antoni Capdevila, Carles Majos