This document provides an overview of CT and MRI imaging in neurology. It discusses the basics of CT imaging, including orientation, planes, windows, density, slice thickness, and contrast enhancement. It also covers common CT findings such as hyperdensities, hypodensities, and ring enhancing lesions. For MRI, it outlines the basic sequences of T1, T2, FLAIR, DWI, and advanced techniques like perfusion imaging and MR spectroscopy. The document aims to explain the key concepts and findings in CT and MRI neuroimaging to help interpret scans.

1. CT/MRI IMAGING
IN NEUROLOGY
AVINASH CHANDRA, MD, FELLOW MS
LECT. KIST MEDICAL COLLEGE, KATHMANDU

2. EXPECT AND NOT TO EXPECT
Able to
do on-call confidently
intreprete important CT findings
interprets CT /MRI scan like a 'pro’
pass medical examination with flying colors

3. THE EYES DON’T SEE
WHAT THE MIND DON’T
KNOW

4. COMPUTED TOMOGRAPHY (CT)
 Based on differential absorption of Xray
 by various tissues.
 • Darker shades correspond to lesser
 attenuation.
 • Slice thickness may vary, but in general,
 it is between 5 and 10 mm for a routine
 Head CT.

5. BASICS OF CT
NEUROIMAGING
 Orientation
 Region/Planes
 Windows
 Density
 Slice thickness
 Contrast enhancement
 Symmetry

6. BASICS OF CT
NEUROIMAGING:
SYMMETRY
 MIRROR IMAGE
 CT brain – 2 identical half

7. BASICS OF CT NEUROIMAGING: PLANES

8. BASICS OF CT NEUROIMAGING: WINDOW

9. CT WINDOWS
 A: Brain window (WW 80, WL 40);
 B: Bone window (WW 3000, WL 500);
 C: Soft tissue window (WW 260, WL 80);
 D: Stroke window (WW 40, WL 40).

10. HYPERDENSITI
ES
 Most common:
•Blood
•Calcification
Exception to
the rule:
– Pineal gland
– Choroid plexus
-Physiological calcification

12. HYPODENSITIES
 Most common:
•Infarction
•Fluid
– edema, infection,
 tumour
•Hydrocephalus
•Air

14. BASICS OF CT
NEUROIMAGING:
DENSITY
 The Density of Blood
Changes with Time!

15. CT BRAIN:
CONTRAST VS
NON-
CONTRAST
 Contrast:
 – Vascular lesion
 – Tumor
 – Sites of infection
 • CTA (stenosis)
 • CTV (CVT)
 • Leptomenigeal
 enhancement
 (meningitis)
 • Ring enhancing lesion

16. RING ENHANCING
LESION
 Tumour
 – Primary (GBM, lymphoma)
 – Metastasis
 • Infections:
 – Abscess
 – HIV associated:
 toxoplasma, crytococcus
 – TB/ tuberculoma
 – Neurocysticercosis
 • Resolving hematoma (10-21
 days)
 • Radiation necrosis
 • Postoperative change
 • Aneurysm
 • Multiple sclerosis/ADEM (MRI)

17. RING ENHANCING LESION

18. MRI
 1.Atoms with an odd number of protons have spin
 2.A moving electric charge, be it positive or negative, produces a magnetic field
 • Body has many such atoms that can act as good MR nuclei (1H, 13C, 19F, 23Na)
 • MRI utilizes this magnetic spin property of protons of hydrogen to produce images.

19. BASIC MR BRAIN SEQUENCES
 T1 • T2 • FLAIR • DWI • ADP • MRS • PERFUSION IMAGING

21. T1 W IMAGES T2 W IMAGES
 Most pathologies dark on T1
 • Bright on T1 – Fat – Haemorrhage – Melanin – Early Calcification – Protein Contents (Colloid
cyst/ Rathke cyst) – Posterior Pituitary appears BRIGHT ON T1 – Gadolinium
 Better pathological details • Fluid bright • Gray matter relatively bright • White matter dark

22. MR SPECTROSCOPY

23. PERFUSION IMAGING SUSCEPTIBILITY-WEIGHTED
IMAGING