Instrumental and spectroscopic quality control Major conclusions,

1. Instrumental and spectroscopic quality control Major conclusions, problems detected, suggestions for the future Marinette van der Graaf UMCN (International Network for Pattern Recognition of Tumours Using Magnetic Resonance)

2. System Quality Assurance (SQA): Extensive SQA measurements Bi-monthly SQA measurements Volunteer measurements MR Quality in INTERPRET Phantom In vivo • Quality Control of MR spectra of patients

3. Cube: 0.1 M lithium lactate (C3H5LiO3) 0.1 M creatine (C4H9N3O2) 1 gr/l sodium azide (NaN3) pH 7.6 INTERPRET phantom for SQA Measurements Outer Volume: 0.15 M sodium acetate (C2H3O2Na) 1 gr/l sodium azide (NaN3) pH 8.3 Prototype phantom

4. Phantom is suitable to test- artefacts- accuracy of volume selection- linearity- homogeneity at various positions Use of a cylinder instead of a sphere gives no problems Phantom solutions remain stable for a long period Evaluation INTERPRET phantom

5. Possible improvements replacement of creatine in inner cube by something else- Creatine resonance at 3.9 ppm overlaps with part of lactate quartet which complicates quantification.- Creatine may slowly convert into creatinine Addition of some Gd-DTPA to shorten T2 relaxation Evaluation INTERPRET phantom

6. SVS measurements with short and long TE(short TE both STEAM and PRESS, if possible) volumes center: (10 mm)3, (15 mm)3, ..., (50 mm)3volumes below: (10 mm)3, (15 mm)3, (20 mm)3 CSI PRESS 136 and STEAM 20 (if possible)axial slide at center through cube All measurements with and without water suppression Extensive SQA measurements, protocol

7. Extensive SQA measurements VOI in center of phantom PRESS 136 Ac Signal Area (a.u.) Cre (3.0 ppm) Selection volume (cc)

8. 8 cc Extensive SQA measurements VOI in center of phantom PRESS 136 Cre (3.0 ppm) Signal Area (a.u.) Ac Selection volume (cc)

9. Extensive SQA measurements Ac Cre (3.0 ppm) Selection volume (cc) PRESS 30, VOI in center of phantom

10. Extensive SQA measurements Cre (3.0 ppm) Ac Selection volume (cc) PRESS 30, VOI in center of phantom

11. In general: spectral quality in range of metabolite signals OK selectivity OK linearity OK Extensive SQA measurements, results

12. In general: spectral quality in range of metabolite signals OK selectivity OK linearity OK Some Philips spectra (off-center) show stimulated echos. Long relaxation times of metabolite spins may play a role. UMCN: selectivity of STEAM better than PRESS IDI: PRESS 30 Increase of Ac signal lower than at other sites. Why??? Extensive SQA measurements, results

13. Measurements give a lot of information But … entire SQA measurement protocols takes a lot of time One has to be careful not to start a complete project on SQA Evaluation extensive SQA measurements

14. To be performed during the first half of every odd month: January, March, May, ... Testing of:- Field homogeneity (FWHM H2O at 3 positions)- Signal-to-Noise ratio- Selectivity of water suppression- Phasing Bi-monthly SQA measurements

15. SVS measurements with short and long TEaccording to protocol 1 or 2 (identical to in vivo measurements) volumes of (15 mm)3 positioned- in the center of the inner cube- 40 mm below the central position- 40 mm left from the central position All measurements with and without water suppression Bi-monthly SQA measurements, protocol

16. Measurements not always performed at all sites(due to system problems or for other reasons) Data conversion and analysis by MRUI: FWHM of H2O: from Lorentzian line shape (time domain fitting) S/N: maximum peak height (0 - 4 ppm) devided by SD of noise (9-11 ppm) selectivity water suppression: ratio of peak areas of Cre resonances fitted as Lorentzians (spectra central cube) phase: automatic phasing by MRUI after ECC Bi-monthly SQA measurements, results

17. Homogeneity: FWHM (< 4 Hz in example, < 0.05 ppm) well below 8 Hz (limit for in vivo spectra). S/N: > 50approximation of a detection limit of ~1.5 mM creatine in voxel of 3.4 cc or ~ 0.6 mM in voxel of 8 cc using 128 scans (in vivo protocol) Generally, S/N inversely correlated with the field homogeneity. Bi-monthly SQA measurementsGeneral results

18. Cr3.9/Cr3.0 showed no dramatic decrease due to water suppression. (NB. Quantitative evaluation complicated by presence of some signal intensity of lactate multiplet at 3.9 ppm.) Phasing: automatic phasing by MRUI after ECC shows that additional phasing (both zero- and first-order) is recommended Bi-monthly SQA measurements showed also stimulated echos in Philips spectra. Bi-monthly SQA measurementsGeneral results

19. Suitable to monitor the performance of the MR systems Performing the protocol is easily and can be quickly carried out Serious artefacts or problems can be picked up, but generally all spectra are OK Spectra of different sites could be used to solve the problems with normalisation (reported by Andy Devos, Leuven) Evaluation bi-monthly SQA measurements

20. SQA volunteer measurements • Purpose: • test of in vivo protocols on healthy volunteers • test quality of in vivo spectra • obtain reference data for pattern recognition • test if data will not be grouped in five sets corresponding to the various acquisition sites

21. SQA volunteer measurements, example SVS, measured at UMCN STEAM 20 spectrum PRESS 136 spectrum

22. Normal spectra present in SVS training list:13 from SGHMS, 5 from UMCN, 5 from IDI, 5 from CDP; do they classify into groups?? Volunteer data from MUL available, but not yet in DB; from UJF in DB; from FLENI?? QA of spectra will also be applied on normal spectra CSI data UMCN volunteers used for MV software Evaluation SQA volunteer measurements

23. Recommendation for future projects:perform the measurements on the healthy volunteers early in the project-> measurement protocol can be tested-> early access to differences between sites in real in vivo spectra Evaluation SQA volunteer measurements

24. Intention: to write a manuscript on the results of the bi-monthly and extensive SQA measurements, and possibly the volunteer measurements However….Presently still part of the data not processed SQA measurements: future plans

25. Purpose: to ensure quality of spectra in the database1. Validation by each site: Linewidth (< 8 Hz) and SNR (> 5) If not or obvious artefacts => ‘bad’ + reason2. Data are uploaded to DB. Approved spectra are judged by 2nd spectroscopist from another site 3. Approval of 2nd spectroscopist => ‘good’ Disapproval of 2nd spectroscopist: 3rd spectroscopist for final decision Quality Control of MR spectra of patients

26. Decision Tree

27. FWHM (Hz): obtained by fitting a Lorentzian lineshape to the water spectrum after ECC S/N : S: signal height in region 0 - 3.4 ppm to be measured after ECC, water filtering and 1 Hz line broadeningN: SD of the noise in region 9 - 11 ppm Other artefacts of any kind, e.g. signal from outside VOI, phase distortions, technical failures. If process cannot be automated, decision based on expert spectroscopist’s eye. Quality Control of MR spectra of patients

28. expert spectroscopists:Carles Arus (UAB), Anne Ziegler (UJF), Franklyn Howe (SGHMS), Marinette van der Graaf (UMCN) Couples: 3rd spectroscopist:UAB - UMCN Franklyn (SVS) Anne (CSI)UJF - SGHMS Carles (SVS) Marinette (CSI) Quality Control of MR spectra of patients

29. Present DB has possibilities to view the spectra with standard processing Process of QC by spectroscopists is going on Quality Control of MR spectra of patients

30. Problems encountered: Good spectra without a water spectrum or with a bad water spectrum will be rejected QC limits (SNR and WBW) may still be discussed Difficult to describe hard criteria by which spectra should be accepted/discarded Evaluation of CSI data Quality Control of MR spectra of patients

31. Good spectra without a water spectrum or with a bad water spectrum will be rejected Quality Control of MR spectra of patients I0018 Selected by CDP for clinical evaluation But no water file

32. Good spectra without a water spectrum or with a bad water spectrum will be rejected Quality Control of MR spectra of patients STEAM20 I1286: problems with ECC

33. QC limits (SNR and WBW) may still be discussed: - Spectra with WBW between 8 and 10 Hz might be borderline cases - S/N: formula and region for noise calculation: Proposal: S/N = H/SD(9-11ppm) < 10 (This approximates S/N = 2.5 H/h < 5) At previous London meeting no decision was made (values stored in DB) Quality Control of MR spectra of patients

34. Typical spectral features of the three manufacturers: Philips, I0410 Quality Control of MR spectra of patients Polyspiculated Phase

35. Typical spectral features of the three manufacturers: Siemens, I1288 Quality Control of MR spectra of patients Signal folded in

36. Typical spectral features of the three manufacturers: GE, I0450 Quality Control of MR spectra of patients Hump

37. Recommendation for future: A more flexible processing will result in a larger number of acceptable spectra:e.g. with phasing (zero + first order)possibility to omit eddy current correction, etc. Quality Control of MR spectra of patients

38. MR quality control in INTERPRET People involved at UMCN: Y. van der Meulen M. Rijpkema D. Klomp M. van der Graaf A. Heerschap