MRI pada Stroke MRI pada Stroke MRI pada Stroke

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1. MRI PADA STROKE ISKEMIK DAN PERDARAHAN Andreas Christian Annisa Pertiwi Emir Aryaputra Fathinah Zuhudan Noprianty EP Pungky Permata Putri Zsa zsa Septriani

2. BASIC MRI

3. Westbrook C, Talbot J. MRI in Practice. John Wiley & Sons; 2018 Oct 22. Three types of motion are present within the atom: • Electrons spinning on their own axis • Electrons orbiting the nucleus • The nucleus itself spinning about its own axis. Magnetic Resonance

4. The nucleus has a magnetic field induced around it and acts as a small magnet . The magnet of each hydrogen nucleus has a north and a south pole of equal strength . The north/south axis of each nucleus is represented by a magnetic moment and is shown by an arrow. The length of the arrow represents the magnitude of the magnetic moment or the strength of the magnetic field that surrounds the nucleus. Westbrook C, Talbot J. MRI in Practice. John Wiley & Sons; 2018 Oct 22. Magnetic

5. Westbrook C, Talbot J. MRI in Practice. John Wiley & Sons; 2018 Oct 22. When placed in a strong static external magnetic field), the magnetic moments of hydrogen nuclei orientate with this magnetic field . Low-energy nuclei do not have enough energy to oppose the main B0 field. These are nuclei that align their magnetic moments parallel or spin-up to the main B0 field. High-energy nuclei do have enough energy to oppose the main B0 field. These are nuclei that align their magnetic moments antiparallel or spin-down.

6. At thermal equilibrium, there are more spin-up, low-energy than spin-down, high-energy spins so the net magnetic vector (NMV) of the patient is orientated in the same direction as B0. The influence of B0 produces an additional spin or wobble of the magnetic moments of hydrogen around B0. This secondary spin is called precession and causes the magnetic moments to circle around B0 . Precessional frequency = Larmor frequency , determined by the Larmor equation.

7. Larmor Equation ω0 is the precessional or Larmor frequency (MHz) γ is the gyromagnetic ratio (MHz/T) B0 is the strength of the external magnetic field (T) ω0 = γB0 • At 1.5 T, the precessional frequency is 63.87 MHz (42.58 MHz × 1.5 T). • At 1.0 T, the precessional frequency is 42.57 MHz (42.58 MHz × 1.0 T). • At 0.5 T, the precessional frequency is 21.29 MHz (42.58 MHz × 0.5 T).

8. Westbrook C, Talbot J. MRI in Practice. John Wiley & Sons; 2018 Oct 22. Resonance

9. Westbrook C, Talbot J. MRI in Practice. John Wiley & Sons; 2018 Oct 22. Because of resonance, in-phase or coherent magnetization precesses in the transverse plane. This changing magnetic field generates an electric current. = Faraday’s Law

10. Free Induction Decay (FID) Signal When the RF excitation pulse is switched off, the NMV is influenced only by B0, and it tries to realign with it. To do so, the hydrogen nuclei lose energy given to them by the RF excitation pulse. The process by which hydrogen loses this energy is called relaxation . As the magnitude of transverse coherent magnetization decreases, so does the magnitude of the voltage induced in the receiver coil. The induction of decaying voltage is called the free induction decay (FID) signal .

11. Pulse Timing Parameters The TR (repetition time) determines the amount of T1 relaxation that has occurred when signal is read. The TE controls the amount of T2 relaxation that has occurred when signal is read.

12. Fat and Water Hydrogen in fat recovers more rapidly along the longitudinal axis than water and loses transverse magnetization faster than water . Subsequently, fat and water appear differently in MR images.

13. The difference in T1 recovery and T2 decay Between Fat and Water

14. Concepts of Magnetic Resonance Four basic steps Placing the patient in the Magnet Sending Radiofrequency (RF) pulse Receiving signals from the patient Transformation of signals into image Chavan, BG. MRI Made Easy. USA. 2013

15. Hydrogen has protons that are positively charred and have rotatory movement called spin → magnetic field Normally protons in human body move randomly in any direction When external magnetic field is applied, these moving protons will align and spin in the direction of external magnetic field. Chavan, BG. MRI Made Easy. USA. 2013

16. Chavan, BG. MRI Made Easy. USA. 2013

17. Relaxations Relaxation means recovery of protons back towards equilibrium after been disturbed by RF excitation T1 T2 Proton density Chavan, BG. MRI Made Easy. USA. 2013

18. Longitudinal Relaxation When RF pulse is switched off, spinning protons start losing their energy. The low energy protons tend to align along the Z-axis Chavan, BG. MRI Made Easy. USA. 2013

19. Longitudinal Relaxation The time taken by LM to recover to its original value after RF pulse is switched off is called longitudinal relaxation time or T1 Chavan, BG. MRI Made Easy. USA. 2013

20. Transverse Relaxation The transverse magnetization represents composition of magnetic forces of protons precessing at similar frequency. More the number of protons precessing at the same frequency (in-phase) stronger will be the TM. These protons are constantly exposed to static or slowly fluctuating local magnetic fields. Hence they start losing phase after RF pulse is switched off. Chavan, BG. MRI Made Easy. USA. 2013

21. Transverse Relaxation The time taken by TM to reduce to its original value is transverse relaxation time or T2 Chavan, BG. MRI Made Easy. USA. 2013

22. TR and TE TR (Time to Repeat) is the time interval between start of one RF pulse and start of the next RF pulse TE (Time to Echo) is the time interval between start of RF pulse and reception of the signal (echo) Chavan, BG. MRI Made Easy. USA. 2013

23. Möllenhoff, K., Oros-Peusquens, A.-M., & Shah, N. J. (2012). Introduction to the Basics of Magnetic Resonance Imaging (pp. 75–98). https://doi.org/10.1007/7657_2012_56

24. RADIOANATOMI

25. Mtui E, Gruener G, Dockery P. Fitzgerald's Clinical Neuroanatomy and Neuroscience E-Book. Elsevier Health Sciences. 2020.

26. Mtui E, Gruener G, Dockery P. Fitzgerald's Clinical Neuroanatomy and Neuroscience E-Book. Elsevier Health Sciences. 2020.

27. Mtui E, Gruener G, Dockery P. Fitzgerald's Clinical Neuroanatomy and Neuroscience E-Book. Elsevier Health Sciences. 2020.

28. Mtui E, Gruener G, Dockery P. Fitzgerald's Clinical Neuroanatomy and Neuroscience E-Book. Elsevier Health Sciences. 2020.

29. Mtui E, Gruener G, Dockery P. Fitzgerald's Clinical Neuroanatomy and Neuroscience E-Book. Elsevier Health Sciences. 2020.

30. Hypertensive hemorrhage Dixon A. CT Brain “Bleeds”. Radiopaedia.org. [Internet] Accessed 1 December 2022.

31. PATOFISIOLOGI STROKE

32. PATOFISIOLOGI STROKE ISKEMIK Stroke iskemik merupakan suatu kondisi terjadinya hambatan aliran/sirkulasi darah otak yang terjadi secara mendadak, menyebabkan gangguan fungsi neurologis Iskemia -> hipoksia sel -> deplesi ATP -> kekurangan energi untuk mempertahankan gradien pada membran sel dan depolarisasi sel -> ion Na, Ca, dan air masuk ke sel -> edema sitotoksik Iskemia -> merusak blood-brain barrier dalam 4-6 jam setelah infark -> protein dan air masuk ke ruang ekstraseluler -> vasogenik edema -> edema semakin membesar dan terdapat efek massa pada onset 3-5 hari -> membaik dalam beberapa minggu dengan adanya resorpsi air dan protein Infark -> kematian sel astrosit, oligodendrial, dan microglial -> nekrosis likuefaksi -> removed by macrophage -> pembentukan volume loss parenkim -> ensefalomalasia

33. PATOFISIOLOGI STROKE ISKEMIK Oklusi pembuluh darah -> iskemik pada teritori vaskuler Area yang mengalami iskemik dengan cerebral blood flow (CBF) <100ml/100 g jaringan/menit disebut Ischemic core Area dengan penurunan perfusi dengan CFB <25 ml/100g jaringan/menit disebut Ischemic penumbra

34. STROKE ISKEMIK DENGAN TRANSFORMASI PERDARAHAN Salah satu komplikasi pada stroke iskemik adalah terjadinya transformasi perdarahan Terjadi akibat ekstravasasi darah melalui blood brain barrier yang mengalami kerusakan Faktor risiko terjadinya transformasi perdarahan pada stroke iskemik: Tingkat keparahan dari stroke Terapi reperfusi (trombolisis atau trombektomi) Hipertensi Hiperglikemi Usia

35. PATOFISIOLOGI STROKE HEMORAGIK Adanya ruptur pada pembuluh darah otak yang dapat disebabkan oleh: Hipertensi Longstanding hypertension → merusak T. media pembuluh darah Nekrosis fibrinoid di subendhothelium Lipohyalinosis pada arterial musculature Lokasi yang sering terjadi di: basal ganglia (50%), lobus cerebral (10-20%), thalamus (15%), pons dan brain stem (10-20%) Hematom: Ganggu sel neuron dan glia → oligaemia, disfungsi mitokondrial dan cellular swelling Trombin → aktifasi mikroglia, inflamasi dan edema Kompresi jaringan otak → meningkatkan ICP (cedera primer) Menekan ventrikel 4 → hidrosefalus Cedera sekunder dari edema, peradangan, gangguan pada BBB, dan produksi radikal bebas (ROS), glutamate-induced excitotoxicity dsb Terdapat area hipoperfusi disekitar hematom

36. GAMBARAN MRI STROKE ISKEMIK

37. Gambaran MRI pada kasus stroke iskemik Berbagai sekuens MRI: ADC mapping Diffusion-weighted imaging (DWI) Fluid-attenuated inversion recovery (FLAIR) Non-contrast and contrast enhanced T1-Weighted T2-weighted Susceptibility-weighted atau gradient-echo Allen LM, Hasso AN, Handwerker J, Farid H. Sequence-specific MR imaging findings that are useful in dating ischemic stroke. Radiographics. 2012 Sep-Oct;32(5):1285-97; discussion 1297-9.

38. Allen LM, Hasso AN, Handwerker J, Farid H. Sequence-specific MR imaging findings that are useful in dating ischemic stroke. Radiographics. 2012 Sep-Oct;32(5):1285-97; discussion 1297-9.

39. Stroke Early Hyperacute ADC → area restricted diffusion tampak hypointense DWI → hyperintense FLAIR → slightly hyperintense T1W dengan kontras → early arterial enhancement, tidak ada parenchymal enhancement T2 → hyperintense (panah hitam), beberapa area di subcortical nampak hyperintense Susceptibility-weighted MR imaging → tak tampak hemorrhagic transformation Wanita 49 tahun dengan kelemahan ekstremitas bawah kanan sejak 3 jam sebelumnya.

40. Allen LM, Hasso AN, Handwerker J, Farid H. Sequence-specific MR imaging findings that are useful in dating ischemic stroke. Radiographics. 2012 Sep-Oct;32(5):1285-97; discussion 1297-9.

41. ADC → area hypointense di parieto occipital junction FLAIR → area hyperintense T1W→ area hypointense T1W dengan kontras → parenchymal enhancement T2 → hyperintense F dan G. Susceptibility-weighted MR imaging → Early blood products (panah) menandakan hemorrhagic transformation → gambaran stroke subakut 7-10 hari Stroke Early Subacute Wanita 87 tahun dengan kelemahan tubuh sisi kiri, onset tidak diketahui

42. DWI → hypointense di lobus occipital kanan dengan hyperintense rim (T2-shine through) ADC → area hyperintense Susceptibility weighted → hemorrhage products di lobus oksipital kanan T2W → hyperintense T1W → hypointense T1W dengan kontras → parenchymal enhancement Stroke kronik 3 minggu - 2 bulan Stroke kronik Stroke pada laki-laki 67 tahun dengan riwayat head and neck cancer

43. Gambaran MRI pada chronic lacunar stroke DWI → hypointense di centrum semiovale kiri ADC → hyperintense T1W tanpa kontras → hypointense T1W dengan kontras → contrast enhancement di centrum semiovale kiri T2W → hyperintense Chronic lacunar stroke pada laki-laki 82 tahun dengan diabetes, hipertensi, dan penurunan kesadaran

44. GAMBARAN MRI STROKE HEMORAGIK

45. Proses transformasi hemoragik hemorrhagic infarction (petechial hemorrhages) (89%) parenchymal hematoma (11%) Gambaran MRI transformasi hemoragik -restriksi difusi pada sekuens DWI/ADC -pada SWI lebih sensitif dari CT →terjadi signal drop out

46. Heit JJ, Iv M, Wintermark M. Imaging of intracranial hemorrhage. Journal of Stroke. 2017;19(1):11–27. (1) petechial hemorrhage along the infarcted tissue margin (HI1), (2) confluent petechial hemorrhage within the infarcted tissue (HI2), (3) parenchymal hematoma involving 30% or less of the infarcted tissue with slight mass effect (PH1), (4) parenchymal hematoma involving greater than 30% of the infarcted tissue with significant mass effect (PH2) European Cooperative Acute Stroke Study (ECASS II

47. Konversi hemoragik pada infark arteri cereblar posteroinferior kiri Dekompresi dengan kraniektomi suboksipital Heit JJ, Iv M, Wintermark M. Imaging of intracranial hemorrhage. Journal of Stroke. 2017;19(1):11–27. DWI