Proton and other Nuclei Spectroscopy

Question 1

overview proton Nuclear Magnetic Resonance (NMR) spectroscopy

Answer 1

protons (H) found throughout the body, particularly in water
In water 2 H and 1 O, O is more electronegative and hydrogen electropositive, causing polarity (dipole) where electron cloud larger around oxygen. This shields H from magnetic field . The frequency that H-spins resonate is a function of the electrochemical environment, hence gives a different magnetic signal in different molecules in body- this is different chemical shift whereby different molecules pick up and respond to different RF signals

Question 2

does H in H2O have a strong or weak NMR spec signal?

Answer 2

strong- because of its large concentration

Question 3

does H in less common metabolites e.g. glutamate, have a strong or weak NMR spec signal

Answer 3

weaker signal

Question 4

what is physically different in NMR spectroscopy setup?

Answer 4

uses larger voxel sizes (due to lower concentrations of certain metabolites, but blurrier) and stronger magnetic field (to push peaks further apart to delineate between them more easily in spectra)

Question 5

give an example of a use of NMR H1 spectroscopy?

Answer 5

scanning brain tumours, can see disruption in tissue through changes in metabolites

Question 6

what different set-up is required for NMR with other nuclei?

Answer 6

• separate RF coils to pick up the different signal given off by different nuclei
• tune scanner to pick up the frequency of nuclei of interest
• sometimes hyperpolarisation techniques are used to boost signal for low conc./ low signal nuclei

Question 7

name 5 nuclei that can be images by NMR

Answer 7

5 from:
2H
3He
7Li
13C
17O
4F
23Na
21P
129Xe

Question 8

overview 2H imaging

Answer 8

• deuterated infusions, used to measure metabolic uptake
• heavy water- extra neutron
• can measure water and glucose hence look at uptake therefore can visualise metabolic activity in brain

Question 9

overview 3He imaging

Answer 9

• Helium 3 is a rare isotope of helium (2p+1n)
• its magnetised using a laser
• used to image lungs looking at dynamic processes such as airflow (can link body and brain processes)

Question 10

overview 7Li imaging

Answer 10

Lithium is a treatment used in bipolar disorder- can look at the distribution of drug in the brain, hence can monitor temporally treatment uptake and distribution (improves understanding of treatment mechanism)

Question 11

overview 13C imaging

Answer 11

• metabolic imaging
• most abundant C isotope is C12, but we also have C13.
• detected in vivo, used a lot in biochem to look at metabolic cycles of metabolites e.g. krebs
• can look at BBB and cancer

Question 12

outline 17O imaging

Answer 12

• O16 most abundant but can use O17
• measure oxygen uptake how its taken from lungs to blood to brain
• looking at metabolism and healthy and diseased tissue
• O17 expensive to get hold of so not used lots

Question 13

outline 4F imaging

Answer 13

• perfluorinated agents
• not found in a high concentration in the body, but can be inhaled as a gas. Has been used to look at lung function e.g. comparing healthy to asthmatic lungs

Question 14

outline 23Na imaging

Answer 14

• sodium
• sodium distribution can be viewed in stroke- elevated Na inside infarct
• also seen in higher levels in CSF

Question 15

overview 31P imaging

Answer 15

P found in ATP- metabolism imaging

Question 16

overview 129Xe imaging

Answer 16

• xenon
• seen in lungs and brain
• long T1- can go from lungs to WM in brain to see signal their
• indicates gas uptake in brain and can few washin and washout in brain

Question 17

overall what does imaging other nuclei (than H) allow

Answer 17

sensitivity to other brain processes which may not be as clear in standard proton MRI