Radiological advancement made so much progress that results in the development of new diagnostic regime and certain application

1. Start with the Great of Allah, the Most Beneficent, the most
merciful

2. Dr Zeeshan Nasir

3.  Interaction of intrinsic magnetic moment of nucleus
with an externally imposed magnetic field results the
phenomena known as nuclear magnetic resonance
 Bloch and colleagues; liquid water
 Purcell and hansen; solid paraffin
 Purcell; describes T1 and T1 processes
 Develop after 30 year latter
 1946- 1976 laboratory NMR
 Name change from NMR to MRI due to public concern

4.  Hydrogen; Detectable, abundance, water molecule
 Creating the signals; super coli conducting system;
alloy that conducts electricity without resistance; 3-T
clinical MRI system
 Detecting signals; radiofrequency coil that generates
electric current then amplified and detected
 MRI room enclosed in electrically shielded rooms with
six sided copper box
 Localizing the signal; spatial origin depends upon
receiving frequency signals

6. Origin of contrast: Three principle intensity factors
• Proton Density
• T1: Rate at which the excitation repeated; TR
• T2: Rate at which spins has been excited into transverse
plane lose coherence
For example: Bone appear hypointense, lung parenchyma
appears hypointese on T2 weighted, CSf appears hypointense
on T1
Pulse sequence parameter known as Echo time (TE) and TR
TI; White matter, grey matter and CSF
T2; CSF, Grey matter, white matter

7.  After repeated TR, the coherence of spinning
molecules will not dissipated and results in production
of TE (Spin echo)
Repetition Time
(TR)
Echo time (TE)
Short TE Long TE
Short TR T1 weighted image Mixed constrast
Long TR Proton Density-
Weighted images
T2 weighted image

8.  Gadolium Chelate; strongly paramagnetic, Acts to
shorten T1 relaxation time of nearby water proton in
blood
 Agent doesn’t cross Blood brain barrier
 Rapidly use of MRA
 High grade usually demonstrate more prominent
enhancement as compare to low grade

9.  Decrease scan time by increasing the efficiency of data
collection
 Either decrease scan time or increase the signal to
noise ratio of resulting image
 This effect will create blurring of image
 To image uncooperative patients with some image
blurring

10.  Transmission of 180 degree RF pulse before pulse
sequencer
 Used to increase contrast between structures,
such as grey matter or white matter
 Intensity White matter, gray matter, CSF
 T1 of 15o miliseconds nullify white matter
 T1 of 375 mili-seconds nullify grey matter
 FlAIR images; nullify CSF signals while
preserving Signals from edematous tissue.

12.  No use of 180 degree pulse;
uses only 90 degree pulse
 Speedy in nature by
decreasing TR
 Flip angles; Low i.e. 5 to 20
degrees results in more of
T2, high I.e. 4o to 90 degree
results in more of T1
weighted images
 Can’t replace conventional
Spin Echo
 MRA, ability to visualize
hemosiderin and ferritin

13.  The entire image can be collected in approx 40 mili-second
 Limits the resolution obtainable (128 x128)
 Essential to DWI, PWI and fMRI

14.  Diffusion of water; ischemic process, the diffusion of
water decreased with increase extracellular space
due to swelling.
 Decrease diffusion: hyper-intense; Acute infarct.
 Increase diffusion: hypo-intense; Chronic infarct.

15.  Two magnetic resonance approach
o Arterial Spin labeling: change of image intensity in
the parenchyma that is caused by spatial Pre-
saturation of blood in ICA
o Bolus injection of contrast; also called dynamic
susceptibility contrast, gadolinium contrast (4 to 5
ml/sec); used to evaluate intracranial neoplasm,
usually to differentiate between Radiation necrosis
and recurrent neoplasm.

17.  Chemical shift; The chemical micro-environment of given
nucleus results in a slight change in resonance frequency of
nucleus from pure expected state.
 Myoinositol, choline; key indicator of membrane turnover
 Creatine and phosphocreatine; part of energy pool
 Glutamate and glutamine; primary excitatory
neurotransmitter
 N-acetyl aspartate; key indicator of neuronal health
 Lactate; indicator of anabolic metabolism shift.
 Elevation of Choline in relation to creatine or NAA indicate
recurrent neoplasm and

20.  Image the change in the ratio of oxy-hemoglobin to
deoxy-hemoglobin in cerebral blood in response to the
stimulus.
 Local metabolic changes in relation to function with
utilization of oxygen by activated cortical structure
 The oxy- hemoglobin > paramagnetic than deoxy-
hemoglobin.

22.  Allow direct visualization of
white matter bundles in the
brain
 Isotropic diffusion; no color in
image
 Anisotropy diffusion ( left to
right); red
 Anisotropy diffusion (ant to
posterior); Green

23. Three principle Method of Displaying DTI data
Fractional Anisotropy
Color eigenvector Image
Tractographic Image

24.  Screening MRI includes, T1, T2 and FLAIR images
 Contrast Images usually include Axial or coronal T1
weighted images or both and sagittal cuts for further
evaluation
 Axial and coronal images are 5 mm thick slices, with or
without an inter-slice Gap of 1 to 2 mm.
 Tailored MRI; High clinical suspicion to focus on
certain entity with thin 3mm contiguous T1 weighted
coronal cuts before and after contrast.
 MRI appearance on Histology grades; lower grade
exhibit no peritumoral vasogenic edema.

26.  20 to 30 % all Glioma
 Hypo-intense (homogenous) to normal brain on T1
weighted
 Mildly to significant hyper-intense to normal brain on
T2 weighted and flairs images
 Low grade; well circumscribed with no peri-tumoral
edema, homogeneous on both T1 and T2 weighted
images
 Rare cases; demonstrate signal intensity that are
similar or identical to those of CSF on T1 and T2
weighted images

28.  High grade tumor; Heterogenous hyper-intense on T2
weighted, cystic component due to necrosis on
contrast
 Some solids neoplasms whose parenchymal
composition and organization produces signals that
mimic CSF lesions.

30.  Hypo- intense of T1 weighted and mixture of hyper-
intense and Iso-intense on T2 weighted
 Gliomatosis Cerebri; diffusely infiltrating without a
descrete mass.

32.  Adults with 40 to 60 peak ages
 Can be mixed and contain both astrocytic and OD
component
 T2 - weighted well circumscribed, homogeneously
hyper-intense
 T1 weighted, contrast enhanced, heterogenously hypo-
intense with no significant enhancement
 70 % calcified; hypo intense on T1 and T2, but micro
calcification can demonstrate hyperintense on T1
weighted

34.  Variable signal intensity; typically hypo-intense on T1
weighted and Hyper-intense on T2 weighted
 But calcification or cystic or hemorrhagic component
often results in variable heterogeneous
 T1 contrast demostrate hetrogenous enhancement of
this lesion
 Can be supra-tentorial typically within lateral
ventricle.
 Can be intra-ventricle or predominantly
extraventricular appearance

36.  In children; atrium of lateral ventricle
 In adults; common in fourth ventricle
 Hypo-intense of T1, Iso-intense to Hyper-intense with
prominent enhancement on T2 weighted
 Homogenous contrast enhancement
 Well circumscribed and lobulated
 Classic Cauliflower like appearance
 Associated with hydrocephlus

38.  Arise from arachnoid cap cells
 Iso-intense in relation to grey matter on T1 and T2
(except synctial and angioblastic )
 On contrast; homogeneous enhancement
 Enhanced thickened dura along the lateral margin of
tumor known as dural tail but its not unique to it, it
can be occur in exophytic glioma, dural metastases,
lymphoma and granulomatous infections

40.  Secretory or non secretory in types
 Micro-adenoma <1 cm, macro-adenoma >1 cm
 Tailored examination
 T1 contrast weighted image (2 to 3mm) coronal images
showed contrast enhancement
 MRA is also an important modility.

42.  Contrast enhancement
 MRI appearance depends; cell of origin, cellular
density and associated pigments
 Localizes at the junction of white and grey matter,
more frequently associated with ACA
 Iso-intense to hypo-intense on T1 weighted
 Iso-intense to hyper-intense on T2 weighted
 Neoplastic cysts; lung, breast, colon
 Meningeal carcinomatosis; breast

44.  Schwann cells
 Most common from CN VIII
 Iso-intense to hypo-intense on T1; hyper-intense on T2
and contrast enhancement.
 Small; homogenously enhance; larger the size, greater
the heterogenous
 Other includes; trigerminal, facial, Glassopharyngeal,
vagus, spinal accessory and hypoglossal nerve

46.  Arise from germinal matrix surrounding the fourth
ventricle, along anterolateral cerebellar hemisphere
 Small round cells; hypercellular, high N:C ratio
 Hypo-intense to iso-intense on T1 weighted
 Iso-intense on T2 weighted
 Contrast enhancement
 Homogenously solid tumor but can have cystic and
necrotic component