Molecular MRI

F. NIKOLAS QEZI

MRI DEPT.

KENT & CANTERBURY HOSPITAL

EAST KENT HOSPITALS UNIVERSITY NHS FOUNDATION TRUST

ENGLAND / UK

Aim of study :What is molecular MRI ?

Molecular MRI is a special implementation of molecular imaging which allows the non-invasive visualization of the biological processes at the cellular and nano-molar level .

Modalities

PET-CT & SPECT

are the most sensitive modalities which have been the forefront in molecular imaging

In recent years molecular imaging has commanded attention beyond the field of nuclear medicine

New technologies

The advance of technology in medical imaging

has brought a new era of innovations.

Especially with the introduction of new state of art

scanners such as the :

Biograph mMR

which combines the spatial

resolution of MRI and the

metabolic sensitivity of PET

Usefulness / Versatility Molecular MRI is useful both in medical diagnostics and research

Medical diagnostics :

1. Improves the visualization in early detection of disease

2. Assist the therapy planning

3. Monitor / follow up the outcome

mMRI in Research

In Research mMRI is very effective to characterize :

1.Angiogenesis ( + / - )

2.Apoptosis ( programmed cell death )

3.Gene expression in living organisms

4.Facilitates the examination of cell migration

Methodology : Study

A recent study evaluates the mMR differentiation of VEGFR-2 levels ( vascular endothelial growth factor-receptor 2 ) in untreated gliomas in GL261 mouse model . The expression of VEGFR-2 levels was evaluated by using a anti-VEGFR2-albumin-Gd-DTPA probe with mMri

Treatment groups show different uptake of those levels in tumour region .

Results : Focusing on the study it confirmed that in vivo VEGFR-2 levels can be monitored as function of therapeutic evaluation .

Utilisation /advantages

The advantages that molecular MRI offers can be best utilised when we have the assistance of high sensitivity and cutting-edge equipment capable of quantitative measurements to detect probes that interact with targets

( contrast agents ) at the nano-molar level in vivo.

Contrast agents

Molecular MRI has proved effective in both cell tracking and detection of molecular process through the use of contrast agents comprised of micro-particles

of iron oxide ( MPIO ) - T2*-

MPIO ‘s provide high sensitivity contrast , owing to their potent super-paramagnetic properties.

Contrast agents are divided into two basic categories :

Negatives : reduction of T2 signal ( SPIO’s )

Positives : enhancing the T1 signal

( i.e. Lanthanide chelate /Gd-DTPA )

Nanoparticles

A category of substances that can act as novel contrast agents are nanoparticles which can be targeted with enhanced diagnostic specificity.

A special category of nanoparticles has also been designed to image dynamic studies / events and could be used in vitro as biosensors

Future role / Perspectives

The application of MRI in molecular imaging

is limited by its intrinsic low sensitivity.

A number of techniques have been developed to overcome this , which utilise a phenomenon termed ‘hyperpolarisation’.

Which is a change in membrane voltage

These techniques have been used

to image tissue pH , cellular necrosis

and to image the lungs.

Although most of the applications have been developed in animal models , they are increasingly being translated into human imaging

Results : Synopsis

Molecular MRI uses probes that can image :

o Biological / anatomical targets in vivo

o Dynamic events in vivo / in vitro

o Enzyme activity in vivo

o Multi–spectral imaging

References

A.Hengerer PhD & J Grimm MD : Molecular magnetic resonance imaging

Biomed imaging interv J. 2006 Apr-Jun, 2(2) : e8

Szatmari T. , Lumniczky K. , Desaknai S. , Trajecevski S. : Detailed characterisation of the mouse glioma 261 tumour model for experimental glioblastoma therapy 2006 Cancer Sci. Jun 97(6) : 546-53

Sosnovik DE. , Weissleder R. : Emerging concepts in molecular MRI ,

Curr Opin biotechnol. 2007 Feb 18(1) : 4-10 Epub 2006 Nov 28.

Gallagher FA . : Clin.Radiol.2010.Jul.65(7) 557-66 doi. 10.1016 / j.crad.2010.04.006

Patricia Coutinho de Souza , Krithika Balasubramanian , Nataliya Smith ,

Debra Saunders , Hong Chen et al. Oklahoma medical research foundation ,

Oklahoma city , USA : molecular MRI differentiation of VEGFR-2 levels on four different

experimental anti-glioma therapies within a GL261 mouse model

Margaret Bennewitz ; Cellular and molecular MRI approaches for cancer diagnosis

Thank You

nikolasqezi@gmail.com

nikolasqezi@yahoo.co.uk