MRA & MRV.pptx

MRA MRV
https://youtu.be/SaOggjUx4o0

1. MRA & MRV Of Brain With Normal Variant Dept. of Radiology & Imaging Dhaka Medical College & Hospital

2. Content: What is MRA & MRV? Purpose. Principle of MRA and MRV. Normal radio anatomy of blood circulation of brain. Normal anatomical variant of vessel.

3. MRA – Magnetic Resonance Angiography MRV – Magnetic Resonance Venography

4. Purpose : To see the blood vessels and blood flow and any potential abnormalities such as aneurysm, stenosis, thrombosis.

5. MRA MRA broadly divided into two – 1.contrast 2.Non contrast Non contrast can be divided into two categories – 1.black blood imaging 2.bright blood imaging

6. Black blood imaging: Spin echo sequence based. In moving blood usually don’t receive either 90 or 180 pulse. Hence signal is not produced and flowing blood appears dark.

7. Bright blood imaging GRE based technique. In GRE excitation pulse is slice selective. Rephasing is applied to the whole imaging. Short TR is used. GRE a more flow sensitive sequence.

8. Basic two type of NCMRA commonly used in routine practice include – 1.Time of flight (TOF) 2.Phase contrast (PC)

9. TOF Base sequence used for TOF MRA is spoiled GRE sequence with gradient moment rephasing . Gradients are adjusted with gradient moment rephasing or nulling (GMR) which prevent signal alteration.

10. Disadvantages of TOF Signal loss in turbulent flow and parallel to imaging slide. Poor signal in atheroma and thrombus . Long acquisition time required. Motion artifacts.

11. PC Bipolar magnetic field gradient pulse. It is of two types which are the positive and negative bipolar gradient pulse.

12. Contrast enhanced MRA 3D spoiled GRE sequence . Gadolinium based contrast agents . T1 weighted spoiled GRE sequence. Central k-space acquisition.

13. MRV Indication: Suspected cerebral venous thrombosis. Preoperative assessment. Technique: Multiple MRI technique can be used – Non contrast enhanced (TOF, PC) Contrast enhanced

14. Blood Circulation of Brain It can be divided into anterior and posterior circulation.

15. . Anterior Circulation

16. Segments of ICA 1.Cervical 2.Petrous 3.Lacerum 4.Cavernous 5.Clinoid 6.Ophthalmic 7.Communicating

17. Normal variants: Aberrant ICA. Congenital absence of ICA. Lateralized ICA. Persistent carotid-vertebrobasilar anastomoses.

18. Anterior Cerebral Artery ACA supplies the medial & superior part of frontal lobe & ant parietal lobe. Medial 2/3 of hemisphere convexity, medial basal ganglia, corpus callosum, genu, ant limb of internal capsule.

19. Segments of ACA Horizontal/pre-communicating (A1): from ICA bifurcation to AcomA Vertical/post-communicating (A2): from AcomA to Callosomarginal artery (junction of rostrum & genu of CC) Distal Part (A3) : distal to the origin of callosomarginal artery A4, A5 : above corpus callosum

20. Branch of ACA

21. Perforating Branch

22. Normal variation & Anomalies of ACA Common : Hypoplastic or absent A 1 Bihemispheric ACA AcoA can be absent, Fenestrated, Duplicated Anomalies : Azygous ACA – single ACA, AcoA absent Infraoptic ACA – A 1 pass under optic nerve (high prevalence of intracranial aneurysm)

23. Azygous ACA variant demonstrates a single midline vessel originating from the joining of bilateral A1 segments

24. Middle Cerebral Artery

25. Segments of MCA Horizontal (M1) : from terminal ICA bifurcation to sylvian fissure. Insular (M2) : from post bifurcation to top of sylvian fissure. Opercular (M3) : began at top of bifurcation and exit sylvian fissure at surface of brain Cortical (M4) : exit sylvian fissure & ramify over lateral surface of hemisphere

26. Normal Variant & Anomalies High variability in branching pattern: Early bi or trifurction True anomalies : MCA duplication (1-3%) Accesory MCA Fenestrated MCA Fenestration

27. Posterior circulation Posterior circulation is the blood supply to the posterior part of brain including the occipital lobe and cerebellum and brain stem. By2vertebral artery ,2 posterior cerebral artery and their branches and basilar artery.

28. Normal Variant & Anomalies Normal variant : VA : variation in size , Dominance (common) BA : variation in course, Brachial pattern (common) Anomalies : - May be fenestration, duplication - Embryonic carotid basilar anastomoses

29. Posterior Cerebral Artery

30. Posterior Cerebral Artery

31. Segments of PCA Pre-communicating (P1) : from basilar artery bifurcation to junction with PcoA Ambient segment (P2) : extend from P1 and curves around cerebral peduncle within ambient cistern Quadrigeminal (P3) : extend behind midbrain to calcarine fissure Calcarine (P4) : terminates above tentorium

32. Normal Variant Anomalies : Fetal origin of PCA (15-20%) Persistent carotid – basilar anastomoses

33. Artery of percheron (rare) : Solitary arterial trunk branches from the proximal segment of PCA & provides arterial supply to the para median region of the thalami bilaterally & often to the rostral part of midbrain.

34. Bilateral Thalamic Infarcts

35. Circle Of Willis Large anastomosis at the base of the brain and lies in the inter peduncular fossa which supply hypothalamus, internal capsule, optic tract, thalamus, midbrain.

36. Boundary : Laterally – by terminal part of both ICA Antero laterally – by a pair of anterior cerebral arteries Anteriorly – by AcoA Postero laterally – by a pair of PcoA Posteriorly – by a pair of PCA with terminal branch of basilar artery

37. PCA infarction

38. ACA Infarction

39. MCA (Rt) infarction

40. Venous Drainage Cerebral Vein Dural Sinus Superficial Vein Deep vein

41. MRA Findings: Both ACA,MCA,PCA are normal in course & caliber No arteriovenous malformation & aneurysm is detected Both PcomA are visualized AcomA appears normal signal intensity Scanned portion of both VA &BA are normal in course & caliber

42. MRV Findings: The superior saggital , straight, transverse & sigmoid sinuses appear normal in morphology. No abnormal narrowing, flow void or dilatation seen. The torcular herrophil , cavernous sinus regions & cortical veins appear unremarkable. The source image reveals no abnormality.

43. Thank You