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Introduction to Neuroimaging

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Presentation on theme: "Introduction to Neuroimaging"— Presentation transcript:

1 Introduction to Neuroimaging
Dr Mohamed El Safwany, MD.

2 Intended Learning Outcomes
The student should be able to recognize an introduction to neuroimaging.

3 Neuroimaging Modalities
Radiography (X-Ray) Fluoroscopy (guided procedures) Angiography Diagnostic Interventional Myelography Ultrasound (US) Gray-Scale Color Doppler Computed Tomography (CT) CT Angiography (CTA) Perfusion CT CT Myelography Magnetic Resonance (MR) MR Angiography/Venography (MRA/MRV) Diffusion and Diffusion Tensor MR Perfusion MR MR Spectroscopy (MRS) Functional MR (fMRI) Nuclear Medicine Positron Emission Tomography (PET) “Duplex”

4 Radiography (X-Ray)

5 Radiography (X-Ray) Disorders of spine: Trauma Degenerative Disorders

6 Fluoroscopy (Real-Time X-Ray)
Fluoro-guided procedures: Angiography Myelography

7 Fluoroscopy (Real-Time X-Ray)

8 Fluoroscopy (Real-Time X-Ray) Digital Subtraction Angiography

9 Fluoroscopy (Real-Time X-Ray) Digital Subtraction Angiography

10 Fluoroscopy (Real-Time X-Ray)
Myelography Lumbar or cervical puncture Inject contrast intrathecally with fluoroscopic guidance Follow-up with post-myelo CT (CT myelogram)

11 carotid US transducer Ultrasound

12 Ultrasound Indications: Advantages: Disadvantages: Carotid stenosis
Vasospasm - Transcranial Doppler (TCD) Infant brain imaging (open fontanelle = acoustic window) Noninvasive, well-tolerated, readily available, low cost Quantitates blood velocity Reveals morphology (stability) of atheromatous plaques Severe stenosis may appear occluded Limited coverage, difficult through air/bone Operator dependent Advantages: Disadvantages:

13 Ultrasound – Gray Scale Gray-scale image of carotid artery

14 Ultrasound – Gray Scale Gray-scale image of carotid artery
Plaque in ICA Gray-scale image of carotid artery

15 Ultrasound - Color Doppler
Peak Systolic Velocity (cm/sec) ICA Stenosis (% diameter) 125 – – 70 225 – – 90 > >90

16 Computed Tomography (CT)

17 Bright = “hyper-attenuating” or “hyper-dense”
Computed Tomography A CT image is a pixel-by-pixel map of X-ray beam attenuation (essentially density) in Hounsfield Units (HU) HUwater = 0 Bright = “hyper-attenuating” or “hyper-dense”

18 Computed Tomography Typical HU Values: Air –1000 Fat –100 to –40
Water 0 Other fluids (e.g. CSF) 0–20 White matter 20–35 Gray matter 30–40 Blood clot 55–75 Calcification >150 Bone Metallic foreign body >1000 Brain


20 “Soft Tissue Window” “Bone Window”
Computed Tomography “Soft Tissue Window” “Bone Window”

21 …stack and re-slice in any plane
Computed Tomography Scan axially… …stack and re-slice in any plane “2D Recons”

22 CT Indications Skull and skull base, vertebrae (trauma, bone lesions)
Ventricles (hydrocephalus, shunt placement) Intracranial masses, mass effects (headache, N/V, visual symptoms, etc.) Hemorrhage, ischemia (stroke, mental status change) Calcification (lesion characterization)

23 Skull and skull base, vertebrae

24 Ventricles Hydrocephalus

25 Intracranial masses, mass effects
Solid mass Cystic mass

26 Intracranial masses, mass effects
L hemisphere swelling Generalized swelling

27 Acute Hemorrhage Intraparenchymal Subarachnoid Subdural Epidural

28 Acute Ischemia Loss of gray-white distinction and swelling in known arterial territory

29 Calcification Hyperparathyroidism

30 CT Angiography Rapid IV contrast bolus
Dynamic scanning during arterial phase Advanced 2D and 3D Reconstructions: 2D multi-planar (sagittal, coronal) Volume–rendered 3D recons

31 Vascular Malformations
CT Angiography - Head Circle of Willis Vascular Malformations Aneurysms

32 CT Angiography - Neck Carotid bifurcations Vertebral arteries
Aortic arch

33 CT Angiography - Indications
Atherosclerosis Thromboembolism Vascular dissection Aneurysms Vascular malformations Penetrating trauma

34 CT Perfusion CBV CBF MTT

35 Hemodynamic Parameters Derived From Concentration-Time Curves
Bolus arrival Vein Artery

36 Hemodynamic Parameter Maps
Transit Time (sec) Blood Flow (mL/min/g) Blood Volume (mL/g)

37 CT Myelography Spinal CT immediately following conventional myelogram
Cross-sectional view of spinal canal along with spinal cord and nerve roots Assess spinal stenosis/nerve root compression (e.g. disc herniation, vertebral fracture, neoplasm)

38 CT Myelography

39 CT Myelography

40 Magnetic Resonance (MR) Hydrogen proton in water or fat

41 Magnetic Resonance Imaging
RF Transmitter Receiver RF = Radio Frequency energy COMPUTER Received signal magnetic field

42 “T2-weighted” w/ fat suppression
Magnetic Resonance “T1-weighted” “T2-weighted” w/ fat suppression

43 Magnetic Resonance T1 T2 Arachnoid Cyst

44 CYTOTOXIC EDEMA (Acute Ischemia)
Diffusion MR Imaging NORMAL CYTOTOXIC EDEMA (Acute Ischemia) Diffusion  MR Signal 

45 Magnetic Resonance Imaging Diffusion DWI
Highly sensitive to acute ischemia— + within a few hours! No other imaging is more sensitive to acute ischemia although perfusion imaging reveals hypoperfused tissue at risk for ischemia Acute left MCA infarction

46 Magnetic Resonance Angiography
Axial “source” images… …reformatted to “maximum intensity projections” (MIP) Multiple projections allow 3D-like display No need for IV contrast!

47 Magnetic Resonance Angiography with Perfusion MR
MRA Perfusion MR

48 Magnetic Resonance Tissue contrast in MR may be based on:
Proton density Water/fat/protein content Metabolic compounds (MR Spectroscopy) e.g. Choline, creatine, N-acetylaspartate, lactate Magnetic properties of specific molecules e.g. Hemoglobin Diffusion of water Perfusion (capillary blood flow) Bulk flow (large vessels, CSF)

49 IV Contrast in Neuroimaging
CT: Iodine-based Iodine is highly attenuating of X-ray beam (bright on CT) MRI: Gadolinium-based Gadolinium is a paramagnetic metal that hastens T1 relaxation of nearby water protons (bright on T1-weighted images) Tissue that gets brighter with IV contrast is said to “enhance” (Brightness, in and of itself, is not enhancement!) Enhancement reflects the vascularity of tissue, but… The blood-brain barrier keeps IV contrast out of the brain! Enhancement implies BBB is absent or dysfunctional Remember: Some brain anatomy lives outside the BBB

50 Hemorrhagic melanoma metastasis
Enhancement T1 T1+C Hemorrhagic melanoma metastasis

51 Question State three different orientations of the brain?

52 Assignments 5 Students will be selected for assignments.

53 Suggested Readings Sutton’s Radiology

54 Thanks

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