Applications of Magnetic Resonance Imaging (MRI)

and Computed Tomography CT)

Lecture 1

F33AB5

What are CT and MRI?

• CT uses X-rays to produce tomographs (images of slices)

• MRI uses magnetic fields to probe the intrinsic magnetisation of hydrogen nuclei

http://www.mri-ny.com/scannersound.html

Overview

• Advantages and problems of each technique

• Anatomical imaging

• Functional imaging

Phillips

Problems of CT

• Dose (fluroscopy/dynamic mode not possible)

• (Speed- improving)

• (3D- now available using helical scanning)

• Artefacts behind bone

Advantages of CT

• (Limited) soft tissue contrast

• Spatial measurements exact (if set up correctly)

Problems of MRI

• Not for people who are claustrophobic• Not for people with metal in their bodies• Susceptibility differences (eg between air and

tissue) cause distortions in most sequences, compromising surgical planning

• Can be slow (not EPI), can have motion artefacts

• Can be expensive (£750k)

Advantages of MRI

• Excellent (and controllable) soft tissue contrast

• Much functional information

• Steerable imaging planes

• Safe

• Hugely versatile

Anatomical- CT

• Intracranial bleeds

• Radiotherapy planning– low geometric distortion– CT contrast relates to radiation attenuation

• Stereotactic surgery– low geometric distortion

• Angiography

Anatomical- CT• Intracranial bleeds• Radiotherapy planning

– low geometric distortion– CT contrast relates to

radiation attenuation

• Stereotactic surgery– low geometric distortion

• Angiography

Chronic subdural haematoma

http://www.radiology.co.uk/xrayfile/xray/tutors/cttrauma/tutor.htm

Anatomical- CT

• Intracranial bleeds

• Radiotherapy planning– low geometric distortion– CT contrast relates to radiation attenuation

• Stereotactic surgery– low geometric distortion

• Angiography

Real Time Multi-Trial Window

http://www.adaclabs.com/prodSolu/rtp/3dtp/3dtp.shtml

Anatomical- CTRadiotherapy planning

Anatomical- CT

Dose distribution along path shown as histogram colored according to the volumes of interest.

http://www.uke.uni-hamburg.de/institute/imdm/idv/publikationen/car1993/

Radiotherapy planning

Anatomical- CT

• Intracranial bleeds

• Radiotherapy planning– low geometric distortion– CT contrast relates to radiation attenuation

• Stereotactic surgery– low geometric distortion

• Angiography

Anatomical- CTMRI CT

CT generally has better geometric accuracyPatient a metal sterotactic frame, ( 'spots' around the head in the images). Streaking artifacts on the CT scans, because of beam-hardening effects.

Brain with a deep central tumour

Dr Paul Morgan, from Academic Radiology

Anatomical- CT

• Intracranial bleeds

• Radiotherapy planning– low geometric distortion– CT contrast relates to radiation attenuation

• Stereotactic surgery– low geometric distortion

• Angiography

Anatomical- CT

Left carotid artery showing aneurysm

Angiography

Anatomical- CT

Ascending aortic aneurysm

Angiography

Anatomical MRI• Head (grey/white matter contrast)

– Tumours – Multiple sclerosis– Myelination in childhood

• Orthopaedic (no bone artefacts)– Spine (sagittal views)

• Great vessels (no contrast agent)

• Bone and soft tissue tumours and disease

• Fluroscopy and Microscopy

Fetal Brain

Placenta

Fetal Lung Fetal Liver

Anatomical MRIFetal imaging-brain

L R

Liver

Spleen

Kidneys

Meal in fundus

Meal in antrumSpinal cord

Anatomical MRI

Anatomical MRI• Head (grey/white matter contrast)

– Tumours – Multiple sclerosis– Myelination in childhood

• Orthopaedic (no bone artefacts)– Spine (sagittal views)

• Great vessels (no contrast agent)• Bone and soft tissue tumours and disease• Fluroscopy and Microscopy

MRI gives flexible contrast

Anatomical MRI• Head (grey/white matter contrast)

– Tumours – Multiple sclerosis– Myelination in childhood

• Orthopaedic (no bone artefacts)– Spine (sagittal views)

• Great vessels (no contrast agent)

• Bone and soft tissue tumours and disease

• Fluroscopy and Microscopy

Anatomical MRI

Orthopaedic MRI (sports injury)

Anatomical MRI• Head (grey/white matter contrast)

– Tumours – Multiple sclerosis– Myelination in childhood

• Orthopaedic (no bone artefacts)– Spine (sagittal views)

• Great vessels (no contrast agent)

• Bone and soft tissue tumours and disease

• Fluroscopy and Microscopy

MR Functional imaging Angiography

Pulmonary arteries

http://www.cardiac-mri.com

Anatomical MRI• Head (grey/white matter contrast)

– Tumours – Multiple sclerosis– Myelination in childhood

• Orthopaedic (no bone artefacts)– Spine (sagittal views)

• Great vessels (no contrast agent)

• Bone and soft tissue tumours and disease

• Fluroscopy and Microscopy

Anatomical MRI• Head (grey/white matter contrast)

– Tumours – Multiple sclerosis– Myelination in childhood

• Orthopaedic (no bone artefacts)– Spine (sagittal views)

• Great vessels (no contrast agent)

• Bone and soft tissue tumours and disease

• Fluroscopy and Microscopy

Functional MRI

Cardiac MRI

End diastole

http://www.cardiac-mri.com

MR Functional imaging Fluroscopy

MRI microscopy

Pharmaceutical Pharmaceutical Dosage FormDosage Form

Castor Bean Seedling

Aplysia Neuron

MaterialsMaterials Plants (Plants (in vivoin vivo)) Excised samples Excised samples ((in vitroin vitro))

Professor Bowtell

Anatomical MRI and CT• Abdominal cancer

– rectal– prostate– cervical, uterine– bladder– breast

• Brain cancer (meninges)• Congential heart disease• Dementia

CT Functional Imaging

• CT is not a very functional modality

• However with contrast agents it can measure– perfusion– angiography– renography

• But- this all requires dynamic repeated scanning… dose is a problem

MRI is a Functional Imaging Technique• Perfusion• Tracers

– Blood brain barrier permeability– Lung function– Molecular imaging?

• Physical properties of tissues– microstructure from relaxation times– microstructure from diffusion– elastic properties

• fMRI- brain activation

MRI is a Functional Imaging Technique• Perfusion• Tracers

– Blood brain barrier permeability– Lung function– Molecular imaging?

• Physical properties of tissues– microstructure from relaxation times – microstructure from diffusion– elastic properties

• fMRI- brain activation

Perfusion rateml/100g/min

>1000500-1000300-500<100

MR Functional imaging- Perfusion

MR Functional imaging Blood brain barrier permeability

MRI is a Functional Imaging Technique• Perfusion• Tracers

– Blood brain barrier permeability– Lung function– Molecular imaging?

• Physical properties of tissues– microstructure from relaxation times– microstructure from diffusion– elastic properties

• fMRI- brain activation

Lung ventilation using hyperpolarized helium

MR Functional imaging Tracers

Dr Owers-Bradley

MRI is a Functional Imaging Technique• Perfusion• Tracers

– Blood brain barrier permeability– Lung function– Molecular imaging?

• Physical properties of tissues– microstructure from relaxation times microstructure from

diffusion– elastic properties

• fMRI- brain activation

MRI is a Functional Imaging Technique• Perfusion• Tracers

– Blood brain barrier permeability– Lung function– Molecular imaging?

• Physical properties of tissues– microstructure from relaxation times– microstructure from diffusion– elastic properties

• fMRI- brain activation

liquid

viscous

36 min 48 min 72 min

Spleen Spinal cord

L R

LiverMeal

Anatomical reference

MR Functional imaging Physical properties: T1, T2

Measuring dilution in the stomach

MRI is a Functional Imaging Technique• Perfusion• Tracers

– Blood brain barrier permeability– Lung function– Molecular imaging?

• Physical properties of tissues– microstructure from relaxation times– microstructure from diffusion– elastic properties

• fMRI- brain activation

MR Functional imaging Diffusion• Staging stroke

• White matter tracts (diffusion anisotropy)

lesion

MRI is a Functional Imaging Technique• Perfusion• Tracers

– Blood brain barrier permeability– Lung function– Molecular imaging?

• Physical properties of tissues– microstructure from relaxation times – microstructure from diffusion– elastic properties

• fMRI- brain activation

MRI is a Functional Imaging Technique• Perfusion• Tracers

– Blood brain barrier permeability– Lung function– Molecular imaging?

• Physical properties of tissues– microstructure from relaxation times – microstructure from diffusion– elastic properties

• fMRI- brain activation

Unit 5

Unit 1

Both digits

Unit 7

Unit 8

Both units

1

2

3 4

FA I

SA I

5

6

8

7

MR Functional imaging fMRI

Which part of your brain senses touch? Dr Francis

Fetuses can think too!

MR Functional imaging fMRI

An MRI study day