New methods and applications in nuclear magnetic resonance microscopy using small RF coils [Elektronische Ressource] / vorgelegt von Edmund Armin Purea

Sujets

• Physik

Informations

• Publié par: julius-maximilians-universitat_wurzburg
• Publié le: 01 janvier 2008
• Nombre de lectures: 11
• Langue: English
• Poids de l'ouvrage: 3 Mo

Extrait

New Methods and Applications
in Nuclear Magnetic Resonance Microscopy
using small RF Coils
Dissertation zur Erlangung des
naturwissenschaftlichen Doktorgrades
der Bayerischen Julius-Maximilians-Universit¨at Wu¨rzburg
vorgelegt von
Edmund Armin Purea
aus
Lugosch, Rum¨anien
Wu¨rzburg 2008Eingereicht am:
bei der Fakult¨at fu¨r Physik und Astronomie
1. Gutachter: Prof. Dr. Peter Jakob
2. Gutachter:
der Dissertation.
1. Pru¨fer: Prof. Dr. Peter Jakob
2. Pru¨fer:
im Promotionskolloquium.
Tag des Promotionskolloquiums:
Doktorurkunde ausgeh¨andigt am:CONTENTS
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2. Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.1 NMR basics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.1.1 Spins and Magnetization . . . . . . . . . . . . . . . . . . . . . . . . 9
2.1.2 Relaxation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.1.3 The spin echo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.1.4 The gradient echo . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.1.5 The Bloch-Torrey equation and the diffusion amplitude . . . . . . . 12
2.2 NMR imaging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.2.1 Principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
~2.2.2 The discrete k-space and the resolution limit . . . . . . . . . . . . . 14
2.2.3 2D and 3D imaging . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.3 Relaxation time and diffusion measurement methods . . . . . . . . . . . . 17
2.3.1 Longitudinal relaxation time T . . . . . . . . . . . . . . . . . . . . 171
2.3.2 Transverse relaxation time T . . . . . . . . . . . . . . . . . . . . . 172
2.3.3 Apparent diffusion coefficient ADC . . . . . . . . . . . . . . . . . . 18
2.4 Small solenoids as RF coils . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.4.1 The principle of reciprocity . . . . . . . . . . . . . . . . . . . . . . 20
2.4.2 Sensitivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
2.4.3 The quality factor Q . . . . . . . . . . . . . . . . . . . . . . . . . . 21
3. Quantitative imaging methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
3.1 Measurement of T . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251
3.2 Measurement of T . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262
∗3.3 Measurement of T . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262
3.4 Measurement of diffusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
4. Multiple coil probehead . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
4.0.1 Probehead construction . . . . . . . . . . . . . . . . . . . . . . . . 30
4.0.2 Parallel data acquisition . . . . . . . . . . . . . . . . . . . . . . . . 31
4.0.3 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
5. Susceptibility matching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
5.1 Alternative substances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
5.1.1 BTCM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
5.1.2 Fomblin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
5.2 The dipole field around a capillary . . . . . . . . . . . . . . . . . . . . . . 384 Contents
5.3 Measurement of susceptibility . . . . . . . . . . . . . . . . . . . . . . . . . 39
5.4 Results and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
6. NMR microscopy of P. triangulum . . . . . . . . . . . . . . . . . . . . . . . . . 43
6.1 Imaging of the head . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
6.1.1 Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
6.1.2 Results and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . 45
6.2 Imaging of the antenna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
6.2.1 Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
6.2.2 Results and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . 46
7. Chemical fixation of single cells . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
7.1 The X. laevis oocyte as a model organism . . . . . . . . . . . . . . . . . . 50
7.2 Cell preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
7.3 NMR experiments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
7.4 Results and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
7.4.1 Fixed samples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
7.4.2 Fixed samples reimmersed in buffer . . . . . . . . . . . . . . . . . . 55
7.4.3 Gadolinium experiments . . . . . . . . . . . . . . . . . . . . . . . . 55
7.4.4 Spectroscopic experiments . . . . . . . . . . . . . . . . . . . . . . . 56
7.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
8. Morphological studies of X. laevis embryos . . . . . . . . . . . . . . . . . . . . . 59
8.1 Embryo preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
8.2 NMR imaging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
8.2.1 Time lapse study . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
8.2.2 HMGN study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
8.2.3 H1A study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
8.3 Results and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
8.3.1 Time lapse study . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
8.3.2 HMGN study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
8.3.3 H1A study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
8.4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
9. Specific labeling using iron oxide . . . . . . . . . . . . . . . . . . . . . . . . . . 65
9.1 Quantification of iron concentration . . . . . . . . . . . . . . . . . . . . . . 66
9.1.1 Relaxivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
9.1.2 Iron quantification . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
9.1.3 Verification using mass spectrometry . . . . . . . . . . . . . . . . . 72
9.1.4 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
9.2 Specific labeling of X. laevis embryos . . . . . . . . . . . . . . . . . . . . . 73
9.2.1 Preliminary experiments . . . . . . . . . . . . . . . . . . . . . . . . 73
9.2.2 Methods and Materials . . . . . . . . . . . . . . . . . . . . . . . . . 74
9.2.3 Results and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . 74
10.Conclusion and outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79Contents 5
11.Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
12.Zusammenfassung. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
Appendix 85
A. Multichannel operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
A.1 Sequential acquistion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
A.2 Simultaneous acquisition . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
A.3 Practical details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
A.3.1 Sequential acquisition. . . . . . . . . . . . . . . . . . . . . . . . . . 88
A.3.2 Simultaneous acquisition . . . . . . . . . . . . . . . . . . . . . . . . 896 Contents1. INTRODUCTION
After its discovery by Rabi in 1937 [1] and the first extensive experiments independently
conducted by Bloch [2, 3] and Purcell [4] in 1946, the effect of nuclear magnetic resonance
(NMR) has developed into a powerful tool for studying a multitude of different problems.
Spectroscopic NMR allows structural and dynamical analysis of inorganic and organic
molecules including proteins. The combination of NMR with spatially varying magnetic
fields as introduced by Lauterbur [5] and Mansfield [6] in 1973 has opened up the field of
magnetic resonance imaging (MRI), which is nowadays a standard diagnostic method in
radiology, due to its advantages such as true non-invasiveness, rich contrast mechanisms
and access to a variety of physical parameters. The NMR signal depends on many differ-
ent microscopic parameters such as relaxation times, diffusion, locals field strength and
macroscopic parameters such as temperature and viscosity.
3Drivenbytheideaofobtainingspatialresolutionssignificantlylowerthan(1mm) ,in-
strumentation techniques were improved and specifically designed for this purpose. Most
important advances were made by increasing the static magnetic field strength and op-
timizing the gradient coils necessary for spatial encoding as well as optimizing the ac-
tual NMR signal detector, the radiofrequency (RF) coil. The field of NMR microscopy,
also termed NMR microimaging, evolved from within MRI. It was loosely defined by
3Callaghan [7] as NMR imaging at spatial resolutions below (100 m) . The method has
been shown useful on a variety of applications, among which are in vivo imaging on small
animals such as mice, imaging of ti