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Introduction to Neuroimaging Dr Mohamed El Safwany, MD.

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1 Introduction to Neuroimaging Dr Mohamed El Safwany, MD.

2  The student should be able to recognize an introduction to neuroimaging.

3 Neuroimaging Modalities Radiography (X-Ray) Fluoroscopy (guided procedures) AngiographyAngiography DiagnosticDiagnostic InterventionalInterventional MyelographyMyelography Ultrasound (US) Gray-ScaleGray-Scale Color DopplerColor Doppler Computed Tomography (CT) CT Angiography (CTA)CT Angiography (CTA) Perfusion CTPerfusion CT CT MyelographyCT Myelography Magnetic Resonance (MR) MR Angiography/Venography (MRA/MRV)MR Angiography/Venography (MRA/MRV) Diffusion and Diffusion Tensor MRDiffusion and Diffusion Tensor MR Perfusion MRPerfusion MR MR Spectroscopy (MRS)MR Spectroscopy (MRS) Functional MR (fMRI)Functional MR (fMRI) Nuclear Medicine Positron Emission Tomography (PET)Positron Emission Tomography (PET) “Duplex”

4 Radiography (X-Ray)

5 Disorders of spine: Disorders of spine: Trauma Trauma Degenerative Disorders Degenerative Disorders Post-opeerative Post-opeerative

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

7 Fluoroscopy (Real-Time X-Ray)

8 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 Ultrasound carotid US transducer

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

15 Ultrasound - Color Doppler Peak Systolic Velocity (cm/sec) ICA Stenosis (% diameter) 125 – 22550 – 70 125 – 22550 – 70 225 – 35070 – 90 225 – 35070 – 90 >350 >90 >350 >90

16 Computed Tomography (CT)

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

18 Computed Tomography Typical HU Values: Air–1000 Fat–100 to –40 Water0 Other fluids (e.g. CSF) 0–20 White matter20–35 Gray matter30–40 Blood clot55–75 Calcification>150 Bone1000 Metallic foreign body>1000 Brain


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

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

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

23 Skull and skull base, vertebrae Fractures

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

31 CT Angiography - Head Circle of Willis Aneurysms Vascular Malformations

32 CT Angiography - Neck Carotidbifurcations Vertebral arteries Aortic arch

33 AtherosclerosisAtherosclerosis ThromboembolismThromboembolism Vascular dissectionVascular dissection AneurysmsAneurysms Vascular malformationsVascular malformations Penetrating traumaPenetrating trauma CT Angiography - Indications

34 CT Perfusion CBV CBF MTT

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

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

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



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

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

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

43 Arachnoid Cyst T2T1

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

45 Magnetic Resonance Imaging Diffusion 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 DWI

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 MRA Perfusion MR MRA Perfusion MR Magnetic Resonance Angiography with Perfusion MR

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

49 1.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) 2.Tissue that gets brighter with IV contrast is said to “enhance” (Brightness, in and of itself, is not enhancement!) 3.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 IV Contrast in Neuroimaging

50 Enhancement T1 T1+C Hemorrhagic melanoma metastasis

51  State three different orientations of the brain?

52  5 Students will be selected for assignments.

53  Sutton’s Radiology


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