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PERFUSION MRI IMAGING. Dr. Mohamed El Safwany , MD. Intended learning outcome. The student should learn at the end of this lecture principles of Perfusion MRI studies. Perfusion imaging. Definitions Principles Some more definitions Perfusion technique Applications Future. Definitions.

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PERFUSIONMRI IMAGING

Dr. Mohamed El Safwany, MD.


Intended learning outcome
Intended learning outcome

The student should learn at the end of this lecture principles of Perfusion MRI studies.

.


Perfusion imaging
Perfusion imaging

  • Definitions

  • Principles

  • Some more definitions

  • Perfusion technique

  • Applications

  • Future


Definitions
Definitions

  • Perfusion is refer to the delivery of oxygen and nutrients to the cells via capillaries

  • Perfusion is identified with blood flow which is measured in milliliters per minute per 100 g of tissue


Principles
Principles

After injection of a contrast agent

  • In normal brain, the paramagnetic contrast agent remains enclosed within the cerebral vasculature because of the blood brain barrier

  • The difference in magnetic susceptibility between the tissue and the blood results in local magnetic field finally to large signal loss


Some more definitions
Some more Definitions

  • rCBF “ the rate of supply of Gd chelate to a specified mass ” ( ml / 100g / min)

  • rCBV - “ the volume of distribution of the Gd chelate during its first passage through the brain ” ( % or ml / 100g )

  • MTT - “ the average time required for any given particle to pass through the tissue, following an idealised input function ” (min or s) MTT = rCBV / rCBF


  • Passage of Gd. can be followed by the changes in the relaxation rates concentration of local contrast.

  • Linear relation bet. concentration and rates of signal changes can be expressed as curve.

  • Tissue contrast concentration time curve can be used to determine tissue micro vascularity, volume and flow.


At each voxel we observe : relaxation rates concentration of local contrast.

slice n

~ ‘mean transit time’

time

Integral:=

cerebral blood volume

intensity

time


Principles1
Principles relaxation rates concentration of local contrast.

  • Each one of these effects is linearly proportional to the concentration of the paramagnetic agent

  • To date, this technique results in non-quantitative perfusion parameters (like rCBV,rCBF or MTT) because of the ignorance of the arterial input function


Hemodynamics Bl. volume relaxation rates concentration of local contrast.

Bl. flow

Aim 1. Diagnosis

2. Monitoring management

3. Understanding intracranial lesions

Dynamic MR perfusion


rCBV relaxation rates concentration of local contrast.

rCBV, processed with “Negative Enhancement Integral”(NEI)

is related to area under curve


MTT relaxation rates concentration of local contrast.

MTT is related to the time to peak and to the width of the peak ; it is processed with “Mean Time to Enhance“(MTE)


Cerebral blood perfusion by bolus tracking
Cerebral blood perfusion by bolus tracking relaxation rates concentration of local contrast.

Requires very high

speed imaging

power injector - Gadolium

5ml/sec

Procedure :

1 - Start Imaging

2 - Inject Contrast*

3 - Continue Imaging

10 slices - 50 images of each slice - TOTAL time 1:34 min

*Push Gadolinium with 20 cc of saline flush


Applications of perfusion mri
Applications of Perfusion MRI relaxation rates concentration of local contrast.

  • Neurology

  • Neuro-oncology

  • Neurophysiology

  • Neuropharmacology


Perfusion imaging findings in infarction

Stroke relaxation rates concentration of local contrast.

Perfusion Imaging: Findings in Infarction

  • CBV

    • regional perfusion deficit

    • compensatory increased volume

  • MTT

    • regional prolongation of transit time


Findings with perfusion imaging for neuro oncology
Findings with Perfusion imaging for Neuro-oncology relaxation rates concentration of local contrast.

  • Critical imaging to BBBB imaging of neoplasm

    • many tumors have high rCBV

    • regions of increased rCBV correlate with areas of active tumor.

    • heterogeneous patterns of perfusion suggest high grade

    • radiation necrosis typically demonstrates low rCBV

  • Lesion characterization may be possible

    • meningiomas have very high CBV in contrast to schwannomas


Neuro oncology
Neuro-oncology relaxation rates concentration of local contrast.

rCBV maps

  • low rCBV in tumour infers low grade glioma


Text book
Text Book relaxation rates concentration of local contrast.

David Sutton’s Radiology

Clark’s Radiographic positioning and techniques


Assignment
Assignment relaxation rates concentration of local contrast.

Two students will be selected for assignment.


Question
Question relaxation rates concentration of local contrast.

Describe the rCBF, rCBV & MTT?


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