Methods of Sample Preparation for Analysis and Quality Assurance of Prostate MR Spectroscopy

Transcription

1 Methods of Sample Preparation for Analysis and Quality Assurance of Prostate MR Spectroscopy Kristina KRISTINAITYTĖ 1,2*, Jonas RAŽANSKAS 3, Vaida PAKETURYTĖ 3, Nomeda R. VALEVIČIENĖ 2,3, Vytautas BALEVIČIUS 1 1 Faculty of Physics, Vilnius University, Vilnius, Lithuania 2 Vilnius University Hospital Santaros Klinikos, Lithuania 3 Faculty of Medicine, Vilnius University, Vilnius, Lithuania 4 Vilnius University, Life Sciences Center, Lithuania MEDPHYS 2017 * Corresponding author: kkristinaityte@gmail.com

2 Application of 1 H-NMR in clinics (MRS) Magnetic resonance spectroscopy (MRS) is a noninvasive imaging modality that provides in vivo metabolite profile of the target tissue. In most diseases metabolic changes occur prior to structural changes. In addition to anatomic images of an area, MRS offers information about the metabolic composition and its changes of the tissue, which occurs before structural changes. 2

3 What is already known? Typical spectra of prostate health tissue vs malignant ((Cho + Cr)/Cit). 3

4 VULSK prostate spectra ((Cho + Cr)/Cit) 4

5 Purpose of the present work To develop a model of prostate phantom which can be used for further development of MRS technique at Vilnius University Hospital Santaros Klinikos: To study the methods of sample preparation. To study ph effects on 1 H-NMR spectra of water or deuterated water solutions of metabolites. Methods Main metabolites that are found in prostate citrate (Cit), creatine (Cr), spermine (Spm) and choline (Cho). Bruker Assend 400WB NMR spectrometer operating at 400 MHz for 1 H. 3T Philips MR scanner operating at 128 MHz. 5

6 1 H-NMR experiment (50 mm) (6 mm) (1 mm) (5 mm) 6

7 Cr

8 Size of the sample (Cr)

9 Size of the sample and the voxel (Cr)

10 MRS vs 1 H-NMR An expansion of 128 MHz 3T MRSI (1) and 400 MHz 1H NMR (2) spectra of prostate metabolites: citrate (Cit), creatine (Cr), spermine (Spm) and choline (Cho). 10

11 Chemical shift of metabolites in solutions with different ph An expansion of 400 MHz 1 H NMR spectra of prostate metabolites. First two from the top are deuterated water solutions with different ph containing metabolites which are shown below each of them dissolved in water. 11

12 Chemical shift of citrate under influence of ph An expansion of 400 MHz 1 H NMR spectra of citrate (Cit) in water solutions with different ph (DSS at 0 ppm). 12

13 Chemical shift between citrate and choline Δδ(Cho-Cit) 13

14 Measuring chemical shift changes in MRS Chemical shift changes between middle point of Cit and DSS in 400 MHz 1 H NMR spectra (left) and between Cit and Cho in 128 MHz (3T) 1 H MRSI spectra (right) of solutions with different ph. 14

15 Concluding remarks Ratio of prostate metabolites ((Cho + Cr)/Cit) in MRSI is the main indicator for malignant tissue. However getting a good quality of spectrum is difficult even after QC using a phantom. So some intensities of metabolites, like creatine, can be too insufficient to be evaluated. Considering spectrum behavior under changes of ph, which occurs if benign tissue becomes malignant, it might be worth taking into account changes of chemical shifts as well. According to our results we have reasons to believe that a difference of chemical shifts between ph-dependent citrate and a significantly more stable (ph independent) metabolite choline is a good indicator for malignant tissue and might be used as additional information for early diagnosis. 15

16 THANK YOU FOR YOUR ATTENTION! 16

17 Localization of the voxel (Cr)

18 Unsupressed water signal from Cr sample