Lab & Diagnostic

When is CT preferred?

Emergencies, acute hemorrhage, trauma, fractures, calcifications, rapid imaging.

When is MRI preferred?

Tumors, demyelinating disease (MS), subtle infarcts, soft tissue evaluation, spinal cord, ligaments, nerves.

CT is best for what two Bs?

Blood and Bone.

MRI is best for what?

Soft tissues and brain pathology.

Which modality uses ionizing radiation?

CT.

Which modality has no ionizing radiation?

MRI.

CT contrast commonly uses

Iodinated contrast.

MRI contrast commonly uses

Gadolinium.

Important MRI contraindications

Non-MRI compatible pacemakers, metallic foreign bodies, cochlear implants, some neurostimulators.

Gadolinium should be used cautiously in patients with

Renal insufficiency.

Fresh blood appears how on CT?

Hyperdense (white).

Bone appears how on CT?

White.

Air appears how on CT?

Black.

CSF appears how on CT?

Dark gray/black.

Gray matter compared to white matter

Gray matter is slightly lighter than white matter.

Loss of gray-white differentiation suggests

Cerebral edema.

Midline shift indicates

Neurologic emergency.

Epidural hematoma shape

Lens-shaped (biconvex).

Epidural hematoma vessel

Middle meningeal artery.

Epidural hematoma associated with

Skull fracture.

Classic epidural presentation

Lucid interval.

Subdural hematoma shape

Crescent-shaped.

Subdural hematoma vessel

Bridging veins.

Most common patients with subdural hematoma

Elderly, alcoholics, falls.

Subarachnoid hemorrhage location

Blood in the sulci and cisterns.

Most common cause of spontaneous SAH

Ruptured berry aneurysm.

Classic symptom of SAH

Worst headache of life.

Intracerebral hemorrhage occurs where?

Within the brain tissue.

T1-weighted MRI

Fat bright, water dark.

T2-weighted MRI

Water bright.

Memory trick for MRI

T2 = H2O (water is bright).

Edema appears bright on which MRI sequence?

T2.

MS plaques are best seen with

MRI.

Normal CSF opening pressure

90–180 mm H₂O.

Normal CSF WBC

Normal CSF protein

Normal CSF glucose

50–80 mg/dL.

Viral meningitis WBC predominance

Lymphocytes.

Viral meningitis glucose

Normal.

Viral meningitis protein

Mildly elevated.

Bacterial meningitis WBC predominance

Neutrophils (PMNs).

Bacterial meningitis glucose

Low.

Bacterial meningitis protein

High.

Bacterial meningitis opening pressure

High.

Ultrasound uses

Sound waves.

Advantages of ultrasound

No radiation, portable, bedside, inexpensive.

Disadvantages of ultrasound

Operator dependent, poor through bone and air.

Best first test for gallstones

Ultrasound.

FAST exam uses

Ultrasound.

Best imaging during pregnancy

Ultrasound.

Nuclear medicine evaluates

Function (physiology).

PET evaluates

Metabolism.

Most common use for PET

Cancer staging.

PET has better resolution than

SPECT.

SPECT commonly evaluates

Cardiac perfusion.

Bone scan indications

Osteomyelitis, metastases, occult fractures.

HIDA scan evaluates

Gallbladder function.

V/Q scan evaluates

Pulmonary embolism.

Fluoroscopy provides

Real-time imaging.

Angiography uses

Fluoroscopy.

ERCP evaluates

Biliary tree (bile ducts).

IVP evaluates

Kidneys, ureters, bladder.

Myelogram evaluates

Subarachnoid space/spinal canal.

Arthrogram evaluates

Joint spaces.

Modified barium swallow evaluates

Swallowing.

Upper GI series evaluates

Esophagus, stomach, duodenum.

Barium enema evaluates

Colon.

ALARA stands for

As Low As Reasonably Achievable.

Highest radiation among common imaging modalities

CT.

MRI radiation

None.

Ultrasound radiation

None.

Fluoroscopy uses

Continuous X-rays.

First imaging for acute stroke

Noncontrast CT.

Best imaging for head trauma

CT.

Best imaging for brain tumor

MRI.

Best imaging for multiple sclerosis

MRI.

Best imaging for ligament injury

MRI.

Best imaging for meniscus tear

MRI.

Best imaging for skull fracture

CT.

Best imaging for spinal cord compression

MRI.

Best imaging for PE when CTA is contraindicated

V/Q scan.

Best imaging for cancer staging

PET/CT.

CT =

Blood + Bone.

MRI =

Brain + Soft tissue.

PET =

Cancer staging.

SPECT =

Heart (cardiac perfusion).

Ultrasound =

Gallbladder + Pregnancy.

HIDA =

Gallbladder function.

ERCP =

Bile ducts.

IVP =

Urinary tract.

Myelogram =

Spinal canal.

Epidural hematoma =

Lens-shaped + Middle meningeal artery.

Subdural hematoma =

Crescent-shaped + Bridging veins.

Subarachnoid hemorrhage =

Blood in sulci + Worst headache of life.

T2 MRI =

Water is bright.

Bacterial meningitis =

PMNs + Low glucose + High protein.

Viral meningitis =

Lymphocytes + Normal glucose.