CSF flowmetry

Basic principles-:

  CSF circulation is related to the cardiac cycle.During systole as blood flow into the brain…, CSF

flows down the aqueduct of sylvius. During diastole the reverse occurs.

So, CSF systole is characterized by caudal CSF motion

& CSF diastole by cranial CSF motion

Routine MRI Brain : Is done including sagittal T2, axial T1,T2, FLAIR , coronal T2

Flow Studies : The direction of velocity encoding is caudo-cranial , so…

Any caudal flow --- low SI (systole)

& any cranial flow --- high SI (diastole)

Retrospective cardiac gating is applied (EGG Synchronization)

A) Qualitative Study Provides visual appreciation of the CSF flow through the

aqueduct & basal cisterns. A sagittal midline image is taken as a reference image,

a midline vertical phase is placed passing through the aqueduct.

Phase images are then obtained, again displaying caudal CSF systole flow as low S.I & cranial CSF diastolic flow as high S.I

B) Quantitative Study We take a midline sagittal T2 image as reference

image. An Image Plane is drawn perpendicular to the

proximal third of the cerebral aqueduct. Then the cursor is placed at its level in the center of

the aqueduct (O). Axial phase images are then obtained showing the

aqueduct as a rounded structure (in cross section). (12-16 phase image are obtained alternating systole & diastole)

=Systolic images =Diastolic images =CSF flow in aqueduct =CSF has in aqueduct =Is of low S.I =is of high S.I

An annular ROI is then placed within the aqueduct on one of the phase image. The ROI should include more of the aqueduct area(excluding brain tissue).

The ROI area (determined by the (right click, Statistics) pixel area) represents the aqueduct area (usually 1-5mm2)

After placing the ROI , copy all is applied to all phase images

Then right click → intensity wave option is selected so that we obtain the velocity of CSF as a curve.

The curve displaying the velocity & flow values along the cardiac cycle.

(Down flow) represent CSF wave during systole (-ve values) (Up flow) represent wave during diastole (+ve values )

• Each curve has a corresponding table (obtained by right click & select table option)

The following parameters must then be calculated & obtained

from the table. 

 

 

 

     

1- End diastolic peak velocity (cm/sec)

2- Peak systolic velocity (cm/sec)

3- Mean systolic velocity (obtained by

calculating the mean value of all

systolic velocities in the table)

4- Peak systolic flow (cm/sec) (table)

5- Mean systolic flow(ml/cm/sec)

calculated from table)

6- Onset of CSF systole (msec)

7- Duration of CSF systole (msec)

8-Aqueducted area (see above)

Finally 9- Calculation of the aqueduct stroke volume (SV) SV = Mean systolic flow x duration of CSF systole (& is expressed in micro liters)

Indications: The main value of the study is to identify

patients with normal pressure hydrocephalus (NPH)

NPH is associated with a classic triad of dementia, gait disturbance, and urinary incontinence.

NPH patients are candidates to shunting procedures with marked improvement while patients with atrophy are not.

NPH During systole… blood goes to the brain, but

the marked ventriculomegaly prevents any outward expansion of the brain. ….So expansion is directed inwards , squeezing the ventricles & expressing a large amount of CSF through the aqueduct, resulting into elevated stroke volume (SV) valves :

These is called HYPERDYNAMIC CSF CIRCULATION.

(SV)> 42 is usually found in such patients.

Atrophy Blood flow to the brain is reduced , therefore CSF

flow & velocities are usually close to base- line values(< 1cm /sec) :

This is called HYPODYMAMIC CSF CIRCULATION

Summary

NPH all values are elevated (HYPERDYNAMIC CIRCULATION)

Atrophy: all values are reduced (HYPODYMAMIC CIRCULATION)

Normal patients of CSF flow quantification (according to a study conducted by

schcecle HWS et al 2000) ( Mean +/-SD)

End diastolic peak velocity 4.73+/-1.73cm/sec

Systolic peak velocity 5.56+/- 1.87 cm/sec

Mean systolic velocity 3.07 +/- 1.09 cm/sec

Mean systolic flow 0.06 +/- 0.06 cm/sec

Duration of CSF systole 465 +/- 84msec

Systolic SV 28 +/- 28.4 cm/sec

CASE 1

Dilated supra and infra tentorial ventricular system out of proportion to the degree of the cortical atrophic changes.

Calculated mean systolic flow (summation of all –ve flow values / their number) = 0.617 cm/sec

Aqueduct stroke volume (SV) = Mean systolic flow x duration of CSF systole = 0.617x 320 = 197 microliters (hyperdynamic circulation).

Report example Technique (at our hospital)

Axial FLAIR

Sagittal T2

Axial images showing CSF flow at the Aqiduct of sylvius.

CSF flow curve:- End diastolic peak velocity = the highest positive velocity value in the table Cm/sec.

Peak systolic velocity = the highest negative velocity value in the table Cm/sec.

Mean systolic velocity= Summation of all positive velocity values / their number Cm/sec.

Peak systolic flow= the highest negative flow value in the table ml/sec

Mean systolic flow = Summation of all the negative flow values/ their number ml/sec.

Onset of CSF systole = From beginning of the curve till the end of the diastole msec.

Duration of CSF systole = from the end of diastole till end of the systole msec.

Systolic stroke volume = mean systolic flow x duration microliters. …(the most important value)

The conventional MR images show:-

- Dilated supra and infra tentorial ventricular system out of proportion to the degree of the cortical atrophic changes.

Conclusion:-

Elevated stroke volume denoting hyperdynamic circulation, being in favor of normal pressure hydrocephalus, for clinical correlation.

THANK YOU

PATIENT NAME:DATE: PROF. DR.: Trans rectal US for the prostate and seminal vesicles revealed:

•Urinary bladder shows normal wall thickness with no stones or masses seen.•Average size prostate measuring ……… mm, volume … cm3, with no foci of calcifications.•The central and the peripheral zones show homogenous echopattern with no focal lesions. •No periprostatic congestion.•Normal seminal vesicles.

OPINIONNormal transrectal ultrasound study.