Magnetic Resonance Imaging in Stroke

Aug 26, 2023

Magnetic Resonance Imaging in Stroke

Created by world-class clinical faculty, Learning in 10 (LIT) Reviews covers topics in the United States Medical Licensing Exam (USMLE) Step 2CK examination.

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Content

0.599 -> welcome to stripe the stroke

2.79 -> interprofessional education program in

5.1 -> this presentation you will learn about

7.44 -> the use of magnetic resonance imaging in

10.169 -> stroke my name is ron and my colleague

12.959 -> is same we are from the Department of

15.089 -> neuroradiology National Neuroscience

17.67 -> Institute

20.72 -> the content for this presentation covers

22.97 -> the following topics a brief explanation

25.31 -> of the magnetic resonance sequences used

27.89 -> in stroke imaging establishing the

30.23 -> presence and each of impacts identifying

33.14 -> large vessel pathology assessing for

35.989 -> hemorrhages and a summary of the above

40.92 -> the five sequences commonly used in mr

43.59 -> strong imaging are t2-weighted

45.77 -> diffusion-weighted imaging magnetic

48.51 -> resonance angiography gradient echo and

51.329 -> fluid attenuated inversion recovery each

54.239 -> sequence is sensitive to different

56.19 -> changes in a chemical environment of the

58.019 -> brain and complement one another the

61.26 -> t2-weighted sequence is sensitive to the

63.21 -> presence of water and fat in tissues

65.19 -> while it does not directly detect

67.68 -> strokes

68.1 -> it is useful for detecting in general

70.05 -> pathologies some of which mimic stroke

72.15 -> symptoms

73.86 -> the diffusion-weighted sequence is

75.78 -> highly sensitive to the speed of water

77.64 -> diffusion from this sequence ADC map is

81.27 -> generated the ADC map can then quantify

84.33 -> the diffusion speed

86.46 -> magnetic resonance angiography is

88.5 -> sensitive to fast flowing blood between

90.78 -> vessels

92.719 -> gradient equal imaging is sensitive to

95.27 -> the presence of iron found in hemoglobin

98.61 -> fooey attenuator inversion recovery is

101.37 -> used to detect establish edema the total

104.67 -> scan time for typical my stroke sequence

107.16 -> is about 15 minutes each additional

110.22 -> sequence at another 5 minutes not all

113.55 -> patients are suitable candidates for MRI

115.92 -> due to the presence of incompatible

118.38 -> implants clinical condition or

120.93 -> claustrophobia

123.02 -> you will now explore how MRI is used to

126.14 -> diagnose the presence h and type of

129.259 -> strokes

132.66 -> DWI is the most sensitive sequence for

135.93 -> detecting acute infox within minutes of

138.9 -> arterial occlusion ischemia leads to

141.6 -> cytotoxic edema infra cellular swelling

144.99 -> causes restricted diffusion of water

147.09 -> molecules this region experiences less

150.33 -> signal loss on the images and hence

152.67 -> appears hyper-intense or bright relative

155.79 -> to surrounding tissue

158.55 -> the ATC map which is automatically

161.07 -> generated from the DWI sequence shows

163.92 -> the opposite effect

166.15 -> the region of restricted diffusion has a

168.489 -> slower diffusion speed than surrounding

170.29 -> tissue and hence appears hypo intense or

173.5 -> dark

175.3 -> a phenomenon known as T to shine through

177.73 -> may occur where a region may appear

180.19 -> bright on DWI but not dark on ADC this

184.84 -> is due to other abnormalities and is not

187.39 -> an acute info

188.85 -> therefore care must be taken to view

191.65 -> both DWI and ADC together when assessing

194.74 -> foster

198.01 -> the appearance of an info on DWI changes

201.25 -> over time within the first week or so

204.269 -> DWI is bright while ADC is dark

208.83 -> subacute face or between one week to one

211.47 -> month cytotoxic edema starts to subside

215.12 -> twi remains bright but slowly diminishes

218.4 -> over time diffusion speed increases and

221.58 -> it is he can appear almost normal

224.77 -> in cloning in fax gliosis sets in water

229.03 -> now diffuses more freely compared to

231.25 -> within surrounding tissue and the

233.35 -> greater signal loss leads to hypo

235.12 -> intensity on the DWI the high diffusion

238.51 -> values show up as hyper intensity on ABC

244.69 -> flair appears as t2-weighted images but

247.9 -> signal from regions of water is suppress

250.09 -> and appear black tissue edema appears

253.99 -> hyper intense but usually only a few

256.6 -> hours after onset

258.829 -> flair is less sensitive compared to DWI

261.349 -> for detective in the box first

264.02 -> it is not routinely done however the

267.8 -> utility of flair comes in when the exact

270.56 -> onset time is not known such as in wake

273.289 -> up or unwitnessed books

276.06 -> if the in fact lesion is visible on DWI

278.94 -> but not on flair it is called a DWI

282.93 -> flare mismatch

285.31 -> this has been used as a surrogate marker

288.01 -> for estimating the lesion age and can

291.04 -> help determine the use of thrombolytics

292.75 -> agent or reperfusion therapy

296.49 -> in fact may be caused by a vessel

298.41 -> occlusion or hemorrhage we will now look

301.229 -> at how MRI can differentiate between the

303.93 -> two

306.919 -> magnetic resonance angiography

309.28 -> emphasizes contrast between flowing

311.629 -> blood and stationary tissue no contrast

315.05 -> injection is required

317.27 -> / faster the blood flow the brighter the

319.699 -> signal on the images therefore Payton

322.759 -> arteries appear bite while stationary

325.46 -> tissue appears dark gray

328.669 -> the images can then be processed into a

331.4 -> three-dimensional view of the blood

333.08 -> vessels without surrounding tissue in

335.389 -> the wing

336.77 -> this is very useful for assessing info

339.68 -> cranial circulation and detecting

341.87 -> vascular pathologies such as occlusions

345.069 -> aneurysms and arteriovenous

347.5 -> malformations

351.29 -> large r3 occlusions appear as southern

354.47 -> signal cut-offs on the MRA with lack of

357.26 -> downstream perfusion this could be due

360.41 -> to an acute thrombus or worsening

362.39 -> chronic stenosis the brain tissue

364.7 -> supplied by the artery is at least of

367.22 -> becoming infected and a DWI can check

370.25 -> for this patients with large artery

372.95 -> occlusions may be candidates for

374.99 -> reperfusion therapy

379.229 -> gradient echo sequences are sensitive to

382.439 -> the presence of iron in hemoglobin which

385.499 -> causes a sharp signal loss in the

387.569 -> immediate area

388.759 -> therefore blood and vessels appear black

393.42 -> larger the amount of hemoglobin the

395.61 -> further the signal loss extends this is

398.31 -> known as a blooming artifact as the

400.71 -> lesion may appear larger than his actual

403.14 -> size the gradient echo sequence cannot

406.95 -> discern the age of the Blee

408.53 -> chronic hemorrhages also appear as

411.54 -> blooming artifacts on the scan due to

414.39 -> iron which hemosiderin staining

417.5 -> a CT scan can help differentiate between

420.86 -> new and old bleeds

425.46 -> bleats maybe caused by vascular

428.07 -> pathologies tumors odd Toma and clinical

433.47 -> history can narrow this down

435.31 -> [Music]

436.9 -> and Emily may be useful to check for any

440.139 -> visions or arteriovenous malformations

442.96 -> if the pattern of bleeding is suspicious

446.05 -> for vascular anomalies

448.7 -> a DWI may confirm the presence of a

452.21 -> hemorrhagic info

455.919 -> in summary MRI is able to diagnose

458.919 -> stroke from on set and differentiate

460.81 -> between ischemic and hemorrhagic causes

463.139 -> to undergo MRI patients must not have

466.81 -> any incompatible implants and be able to

469.78 -> keep still for the duration of the scan

472.349 -> DWI can detect and in fact within

474.849 -> minutes of onset time DWI images should

478.389 -> always be viewed with a corresponding

480.219 -> ADC Flair is useful in weaker and

483.669 -> unwitnessed strokes as a DWI flare

486.46 -> mismatch may is a surrogate marker for

489.37 -> onset time

491.38 -> Mr a can assess intracranial circulation

494.35 -> and identify large vessel occlusions as

497.11 -> well as other vascular anomalies

501.09 -> myths are visible on GRE by the h of the

505.11 -> bleep maybe indeterminate

508.22 -> thank you for listening to our

510.08 -> presentation we hope you have found it

512.87 -> helpful please continue to explore

515.81 -> stripe for more strong interprofessional

518.36 -> education resources

Source: https://www.youtube.com/watch?v=L-k0oJ7rQ4k