[10.13] Radiologic Modalities in Neurology V2.3.pdf

CT Scan

What is the predominant imaging modality for the initial evaluation of patients with suspected stroke?

Fluoroscopy

Which modality is used for interventional procedures in neurology?

Ultrasound

Which imaging modality is primarily used for pediatric patients?

Speed, availability, and relatively cheaper price

What are the three main reasons CT scans are typically ordered first for stroke patients?

Hemorrhage, tumors, infections, and vascular malformations

What are four stroke mimics that a CT scan can exclude?

Normal

How do most CT scans appear in the first 6 hours after symptom onset?

4 to 6 hours

What is the duration of the golden period for stroke management?

Treat the patient, not the imaging

What is the rule regarding clinical correlation and imaging in stroke management?

Prognostication

What is crucial for the patient during the first 6 hours of a stroke evaluation?

Thrombectomy

A neurological interventionalist may perform which procedure if a patient is evaluated within the early stroke window?

Poor definition of the gray matter-white matter interface

What is a primary brain feature of early stroke visible on a CT scan?

Transition zone

What term describes the area where brain tissue abruptly changes on imaging?

Pale or White

How does the cortex/gray matter appear on a CT scan?

Grayish

How does white matter appear on a CT scan?

Opposite of their names

What is the irony regarding the CT appearance of gray and white matter?

Loss of the insular cortex and external capsule

What anatomical change is highlighted by the red circle in Figure 2/3 as a sign of early infarct?

Post-ictus

What term means "after the onset of symptoms"?

Completed infarct

What does extensive edema and brain herniation toward the contralateral side after 3 days indicate?

5 to 7 days

When does edema typically peak after a stroke?

Dense Middle Cerebral Artery Sign or Hyperdense Artery Sign

What is the term for a bright-looking M1 segment of the MCA on a CT scan?

White

What color is blood on a CT scan?

Thrombus

What specific finding causes a hyperdense artery sign?

Stagnation of blood flow

Why does a thrombus become detectable on a plain CT study?

Thrombolytic drugs

What medication is contraindicated if a patient presents with intraparenchymal hemorrhage instead of an infarct?

Timed to see early arterial enhancement

How is a bolus of contrast timed during a CT angiography procedure?

Arteries then venous system

In what order do brain vessels light up during CT angiography?

Candidates for thrombectomy

What does impeded or absent contrast flow in the MCA indicate for the patient's treatment plan?

Magnetic Resonance Imaging or MRI

Which modality is more sensitive and specific than CT for detecting cerebral ischemia in the first few hours?

CT Scan

Which modality is not good for posterior circulation infarcts due to bone artifacts?

Infarcts are hyperintense on T2

How does a relatively late-stage stroke appear on a T2-weighted MRI?

T1WI, T2WI, DWI, GRE, and SWI

What are the five MRI sequencing techniques mentioned in the overview?

Diffusion-Weighted Imaging or DWI

Which MRI sequence is most sensitive for hyperacute infarcts?

Decreased water diffusion

What specific phenomenon do areas of infarct exhibit on a DWI?

Restricted diffusion

What is the term for water not flowing freely between intracellular and extracellular compartments during an infarct?

Failure of ion channels

What cellular mechanism leads to restricted water diffusion in an infarct?

Sodium and water retention inside the cell

What happens where sodium goes in the context of cell swelling during an infarct?

Areas of increased signal or Bright

How are areas of decreased water diffusion seen on DWI?

10 to 30 minutes

How soon after an ischemic insult can a bright signal be seen on DWI?

Infarct Core

What is the term for the dead part of the brain that has suffered irreversible damage?

Penumbra

What is the term for the salvageable part of the brain that can recover with timely reperfusion?

T2 or T2-FLAIR

Which sequences can be used to estimate the penumbra in MRI?

Clinical eyes

Besides imaging confirmation, what must a doctor trust when a CT is clear but symptoms are high degree of suspicion?

Effacement of sulci and loss of gray matter

What two signs on CT point to an infarction undergoing hemorrhagic transformation?

Full extent is better visualized

What is an advantage of DWI over CT when assessing an area of infarction?

Vessels become more fragile

Why do large infarcts have a higher tendency to undergo hemorrhagic transformation?

Reperfusion

What process can cause fragile vessels in a large infarct to bleed?

One third

Physicians are cautious about thrombolytics if the infarct is more than what fraction of the MCA territory?

Tumors, inflammation, MS, hemorrhage, seizures, and CPM

What are six differentials for a bright signal on DWI besides an infarct?

Encephalomalacic changes

What term describes brain tissue loss due to damage or atrophy in chronic infarcts?

Resorbed

What happens to dead brain tissue in a focal area of volume loss over time?

Lack of edema and mass effects

How do chronic infarcts differ from acute infarcts in terms of pressure?

More than 3 to 4 weeks

How old is a chronic infarct defined in this lecture?

MRI

Is it easier to age infarcts using CT scan or MRI?

Gradient Echo Sequence or GRE

Which special MRI sequence is used specifically to look for the presence of blood?

Dark

How do bleeds appear on GRE or SWI sequences?

Magnetic Susceptibility

What term refers to certain substances like iron and calcium distorting the local magnetic field?

Iron-containing hemoglobin

What substance in a bleed causes it to appear dark on susceptibility imaging?

Susceptibility-Weighted Imaging or SWI

Which MRI sequence is more sensitive than GRE for detecting blood?

Less than 30 seconds to a minute

How long does a cranial CT scan typically take?

Scanned one time

How many times is a patient typically scanned in a CT procedure?

20 to 30 minutes

How long does an MRI typically take?

Imaged separately

In an MRI, how are individual sequences produced compared to CT?

Patient cooperation

What is a major limiting factor for MRI that is not as problematic for CT?

Similar

How does the sensitivity of a CT scan for an infarct compare to an MRI after 12 hours?

Vascular anomalies

What term refers to the absence of intervening capillaries between arteries and veins?

Shunting of blood from artery to veins

What results from the absence of capillaries in an AVM?

Bag of black worms or flow voids

How do flowing blood vessels in an AVM appear on MRI?

Blood is moving too fast

Why does flowing blood appear as black flow voids on MRI?

Strong enhancement

How does an AVM appear on a T1 contrast-enhanced study?

Aneurysm

What is a weakness in the wall of a blood vessel that causes bulging?

Bifurcations where flow is turbulent

Where do aneurysms usually occur in the vascular system?

Saccular and Fusiform

What are the two general shapes of aneurysms?

Saccular

Which type of aneurysm has an outpouching on one side and is more prone to rupture?

Fusiform

Which type of aneurysm involves an outward bulging in all directions?

Anterior communicating artery

What is the most common site for a brain aneurysm?

M1 to M2 bifurcation

What is the second most common site for a brain aneurysm?

Conventional Angiography

What is the gold standard for aneurysm detection?

Radiation dose is high

What is a significant drawback of conventional angiography?

Diagnostic purposes only

CTA and MR angiography are primarily used for what?

Clipping

What procedure involves opening the skull vault to treat a large aneurysm?

Coiling

What procedure involves placing material in a small aneurysm to thrombose it?

Nipple sign

What sign on a CTA indicates a lobulated saccular aneurysm that has likely ruptured?

3D Reconstruction

What type of CT angiography visualization is shown in Figure 20?

EDH, SDH, and SAH

What are the three extra-axial traumatic brain injuries?

Diffuse Axonal Injury and Parenchymal Contusion

What are the two intra-axial traumatic brain injuries?

CT Scan

What is the main imaging modality for patients with trauma?

Skull X-ray

Which modality is described as not helpful and not recommended for traumatic injuries?

Biconvex or Lentiform

What is the characteristic shape of an epidural hematoma?

Calvarium and brain parenchyma

Between which two structures is an EDH convex?

Suture lines

What anatomical boundaries do EDHs typically not cross?

Falx and Tentorium

Which two dural reflections can an EDH cross?

Artery

What type of vessel is the most common source of an EDH?

Inner skull table and the dura mater

Between which two layers is the blood in an EDH contained?

Displaced dura

What does the black line between an EDH and the brain on a T2 MRI represent?

Hyperacute

If a hemorrhage is intermediate on T1 and bright on T2, what is its age?

Old

If a hemorrhage is dark on both T1 and T2, what is its age?

Methemoglobin

Which hemoglobin state appears dark on SWI or GRE regardless of age?

Shaken Baby Syndrome

Dating bleeds using MRI is particularly important in which pediatric case type?

Bridging cortical veins

What vessels are typically stretched or torn to cause a subdural hematoma?

High velocity trauma

What type of trauma usually causes the shearing of vessels in an SDH?