Neuroscience  4.1.2  Nov. 9, 2015  

Neuroimaging Dr. Louie Gayao

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OUTLINE A. Neuroradiologic History B. Radiologic Neuroanatomy C. Diagnostic Tests

1. Roentogram 2. Cranial Ultrasound 3. Cranial CT 4. Cranial CT Angiography 5. Cranial CT Perfusion

NEUROIMAGING

A. NEURORADIOLOGIC HISTORY

Neuroimaging o Use of various techniques to directly or indirectly

image the structure or function of the nervous system o Indications:

• It follows patient history and neurologic examination to investigate a patient who may have neurologic disorder.

History

o Before the advances in radiology, direct visualization of intracranial compartment was norm

o Exploratory burrholes Indications:

1. Rapidly deteriorating neurologic exam 2. Lack of scanning facilities 3. Inaccesible remote area 4. Patients unfit for transfer

Pag naghahanap at mageextract ng tumor, drill a hole on one side; pag wala sa isa, sa kabila naman. Pag wala pa rin,tigil ka na. Hanggang dun lang ang pwede mong gawin o 1895- German physics professor discovered Xray. He

referred to radiation as X, to indicate it as ann unknown type of radiation. Xray was noted at that time to pass through human tissue but it could not pass thrugh bone or metal

o 1927- Portugese physician Egas Moniz provided contrasted xray cerebral angiography in order to diagnose several kinds of nervous diease such as tumors, artery disease and AVM.

o 1950s- Ultrasound gained in popularity o 1970s- Development of CT Scan o Eary 1980s- Development of MRI

B. RADIOLOGIC NEUROANATOMY

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C. DIAGNOSTIC TESTS • Neuroimaging • Indications:

o Rule out structural disorder o Recurring progressive headaches o Focal slowing on EEG o Comorbid seizures o Persistent unilateral headaches o Assure anxious patient or his relatives

1. Roentogram

• Photograph made with X-rays SKULL X-RAY

• Picture of bones surrounding the brain • Abnormal results may be due to: fracture, tumor,

erosion or decalcification of bone and movement of the soft tissues inside the skull

• AP view- Used to know the laterality of findings • Frontal and lateral view- Used to look for functional defects • Interpreted as hypodense (dark part) or hyperdense

(lighter part; Possibly water or air) • Metal is Hyperdense (compared to bone) • Bullet is very heavy (could migrate from one area to

another) • Intraoperative x-ray is performed to know if the area where

bullet is desired to be extracted is accessible or not

Depressed fracture

CERVICAL X-RAY • Locate the anterior vertebral line and posterior vertebral

line; assess if normally aligned and check for hernia • What to do if shoulder is not obstructing the view? Put

down the shoulder. Do not just tilt it. Tilting will obstruct the reading, too.

• 3 Views needed: AP; Lateral; Open Mouth

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THORACIC X-RAY • An x-ray of the 12 chest bones/thoracic vertebrae. The

vertebra are separated by flat pads of cartilage called disks that provide a cushion between the bones.

• Used to evaluate bone injuries, cartilage loss, diseases of the bone, tumors of the bone.

• Test can detect bone spurs, deformities of the spine, disk narrowing, dislocations, fractures, thinning of the bones (osteoporosis), degeneration of vertebrae

2. Cranial Ultrasound o Uses reflected sound waves to produce pictures

of the brain and the inner fluid chambers (ventricles) through which the CSF flows.

o Indications

i. Prematurity ii. Persistent large fontanel iii. Synostosis *** iv. Infection v. Trauma

o Limitations i. Operator dependent-Di mo alam

view ng operator, mahirap i-orient ang sarili

ii. Small acoustic window iii. Cannot assess myelination iv. Cerebellar lesions, infarcts v. Small hemorrhages could be missed vi. Deeper: blurred

ACOUSTIC WINDOWS

ACOUSTIC WINDOWS - FONTANELLES

• Anterior fontanelle (9-15 mos.); PATENT FROM 9 - 15 MOS., BY 15TH MO. NAGCLOCLOSE NA SIYA.

• Posterior fontanelle (CLOSED BY 3 mos.) • TEMPORAL FONTANELLE - AROUND MGA 3 Y/O • Mastoid fontanelle (24 mos.)

• From the anterior fontanelle, depends on the position of

your ultrasound probe you can direct it more frontally, medial, posteriorly. You could adjust your probe to go longitudinally so that you could see medially going laterally.

• From anterior fontanelle, directed anteriorly, you would expect to see your frontal lobes, interhemispheric fissure and your orbital ridge.

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• Dependent, kung hindi mo alam kung paano ang view ng

operator, it's very hard for you to orient yourself. But there are standard views in doing cranial UTZ. So may c1 hanggang c7. May use silang lahat so somehow pag sinabing c1 cut, alam mong it's more of anterior c2, c3, c4, c5, c6, c7. Somehow may idea sila kung saan yung location ng probe mo.

• Here you can see the interhemispheric fissure, frontal lobes. As you go deeper, the resolution of your structures becomes more blurred already.

• Here you can see lateral ventricles and your Cavum Septum Pellucidum. Septum Pellucidum, iniisip niyo lang is parang direct lang, isang septum lang siya. But your septum sometimes there's a space in between that is your cavum septum pellucidum.

• Then this is the end of your caudate and putamen. Hindi siya ganun kalinaw. So if I’m gonna ask a question, it would be nearer the probe to identify the structure.

• This is the very easily identifiable, eto the third ventricle, as you know beside your third ventricle would be your thalamus.

• Sylvian fissure very vague, lateral ventricle, corpus callosum, you expect na nandito lang siya. Interhemispheric fissure, frontal lobe. So it would depend on the operator for you to have an orientation.

• Lateral view of your UTZ. Corpus callosum, cingulate

gyrus, third ventricle, yung iba medyo malabo na so it's very hard to identify.

• Two modalities for cranial CT:

o Plain Study o Contrast Study

3. Cranial CT

a. PLAIN o Advantages

• Procedure of choice for acute hemorrhage and skull fractures

• Cheaper than MRI • Faster testing time • Angiography: Vascular anomaly or

aneurysm detection (To check for Intracranial Pressure)

o Disadvantages • False negative results for small lesions • Radiation exposure • Allergic reaction (some people have allergic

reactions to the contrast being used or to the iodinated contrast).

• Pregnancy is a contraindication (contraindicated because of radiation effect, they could place a radiation shield but as much as possible they do reduce the radiation exposure of the patient).

• Creatinine monitoring (your kidney is the one being used to excrete your contrast so you have to monitor that, check before you give your contrast).

o Indications • Hemorrhage • Ischemia • Fractures • Calcifications

b. CONTRAST o Iodinated contrast is injected to enhance imaging o Indications

• Neoplasms(TUMOR) • Vascular malformations(VASCULAR

ANOMALIES) • Meningitis(INFECTION)

**So you would see (the aforementioned) that would light up in the scan.

• This is somewhat a normal cranial CT scan. As you can

see there are some calcifications. CT scan has three modalities: (1) Contrast scans, (2) Plain scan, (3) Bone window So these could replace your x-rays. If the patient is really uncooperative and you could not do an x-ray, you could see fractures already with your cranial ct. You first have to identify what's normal. The sutures you might consider fractures, so somehow you should know where are the sutures and differentiate sutures from your fractures.

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• Another view of your basal skull, so you have your mastoid,

your petrous, your clivus, simple squamous temporal bone, greater wing of your sphenoid

• By anatomy, you would expect there is a small line here.

So that's your coronal suture, frontal bone, parietal bone, and occipital bone. So here it's not a fracture, ayan yung lambda structure niyo.

HYPODENSE LESION?

• The hypodense contains fluid so that's our 4th ventricle. (doc also pointed out the 4th ventricle, cerebellum and brainstem).

Sylvian fissure?

Temporal horn of lateral ventricle? • Normally you don't get to see your temporal horn of

lateral ventricle but once you see it, may hydrocephalus ka na.

What's the star?

Cistern, it's hypodense so most probably it contains fluid, most probably CSF. Nandiyan yun basal cistern, carotid cistern, suprasellar cistern, interpeduncular cistern nandiyan siya, so yun yung basal cisterns natin.

Eh yung masayang singkit?

• You can see your lateral ventricle, frontal horn, third ventricle, lateral ventricle to third ventricle connected by interventricular foramen (foramen of Monroe)

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Pineal gland calcified

In CT scan – hypodense (dark); in MRI- it's hyperintense (dark)

4. Cranial CT Angiography

• Employs rapid injection of iodinated contrast to visualized

intracranial vessels • Intracranial vessels are reconstructed after removal of bone

and parenchymal elements • 3D RECONSTRUCTION USING CT ANGIOGRAPHY • You give large dose of contrast then do scan then the

computer will reconstruct based on the flow of the contrast. • The problem here is that manually nilang tinatanggal

yung bone structures and sometimes manually din natatanggal yung ibang blood vessels.

• Depending on how good the technician, if the technician is good he will identify that as a pathology, aneursym, small blood vessels but sometimes they just remove it, binura lang nila kasama yung bone. So you could get negative angiogram.

• Advantages o Ct angio readily available o Rapid processing - important for unstable patients

• Disadvantages o More contrast used compared to conventional

angiogram o Radiation o User/processor dependent o Could not assess flow pattern

5. Cranial CT Perfusion

• The key to interpreting CT perfusion in the setting of acute

ischemic stroke is understanding and identifying the infarct core and the ischemic penumbra, as a patient with a small core and a large penumbra is most likely to benefit from reperfusion therapies.

• Penumbra - water shed, salvageable by further medication. • In plain CT, you could not see the lesion yet. In perfusion

scan, you could see the infarcted area already. • The Three parameters typically used in determining these

two areas are: o Mean Transit Time (MTT) or time to peak of the

deconvolved tissue residue function (Tmax) o Cerebral blood flow (CBF) o Cerebral blood volume (CBV)

“Blue is Bad”

T1: Fluid (CSF) is black T2: Fluid (CSF is white Better images in swelling In MRI: Hypointense – dark area Hyperintense – light area

REFERENCES • From higher batch trans • From Textbook of Radiology and Imaging, Volume 2, 7th

Ed. D. Sutton • From LANGE Basic Radiology • FROM LECTURE RECORDING