Lecture 4 - Modalities

X-ray of the breast.

What is mammography?

Powders, perfumes, lotions, and deodorant.

What should be avoided before mammography?

X-ray done in real time showing moving images of internal structures.

What is fluoroscopy?

Similar radiation dose.

How does fluoroscopy radiation dose compare with CT?

Low to intermediate cost and operator dependent.

What are fluoroscopy's cost and operator characteristics?

GI, GU, skeletal, and pulmonary systems, plus angiography/interventional procedures.

What systems can fluoroscopy image?

Barium x-rays, cardiac catheterization, arthrography, intravenous pyelogram, hysterosalpingogram, and percutaneous vertebroplasty.

What are fluoroscopy examples listed?

As an adjunct to see coronary blood flow and evaluate arterial blockages.

How is fluoroscopy used in cardiac catheterization?

The uterus and fallopian tubes.

What does an HSG examine?

Structural defects in the uterus and blockage of the fallopian tubes.

What can an HSG show?

Endoscopic Retrograde Cholangiopancreatography.

What does ERCP stand for?

An endoscope is passed into the duodenum and contrast is injected into the bile ducts and/or pancreatic duct.

What happens during ERCP?

The esophagus, stomach, and duodenum using oral contrast.

What does an upper GI fluoroscopic study evaluate?

Polyps, masses, malpositioned bowel, motility problems, GE reflux, and hiatal hernia.

What can an upper GI study detect?

The colon using rectal contrast.

What does an enema fluoroscopic exam evaluate?

Small polyps or other precancerous lesions.

What can an enema exam detect?

The mouth, esophagus, and swallowing mechanism using oral contrast.

What does a barium swallow evaluate?

NPO for 6 hours.

What is usual preparation for GI fluoroscopy?

Bowel prep.

What preparation may be needed for rectal contrast?

No prep.

What prep is needed for spinal fluoroscopic exams?

Transmission of high-frequency sound waves through tissues to provide contrast and make images from reflected waves (echoes).

What is ultrasound?

Pediatrics, obstetrics, vascular imaging, orthopedics, renal imaging, and scrotal imaging.

What are ultrasound uses listed?

For guidance of biopsies, thoracentesis, and other interventional procedures.

How is ultrasound used for procedures?

None needed routinely.

What is the routine prep for plain X-ray?

5-10 minutes.

How long does the actual plain X-ray take?

magnetic resonance angiography

MRA

Orthopedic hardware, prosthetic valves, titanium wires, and coronary stents.

What hardware should be OK with MRI according to the deck?

Whether they have a card given after the implant.

What should a patient with an implant be asked about before MRI?

Consult the imaging facility or MRIsafety.com.

What should be done if MRI implant safety is uncertain?

Fat.

What does T1-weighted MRI make bright?

Intermediate.

How does muscle appear on T1?

Dark.

How does water, blood, or CSF appear on T1?

Gray matter is darker than white matter.

How does gray matter compare with white matter on T1 brain MRI?

Water.

What does T2-weighted MRI make bright?

Slightly less bright.

How does fat appear on T2?

Intermediate.

How does muscle appear on T2?

White matter is darker than gray matter.

How does white matter compare with gray matter on T2 brain MRI?

Dark/hypointense on T1 and bright/hyperintense on T2.

How does CSF appear on T1 versus T2?

Dark on T1 and bright on T2.

How does fluid appear on T1 and T2?

Black on both.

How does air appear on T1 and T2?

Very dark on both.

How does tendon appear on T1 and T2?

Black on both.

How does bone cortex appear on T1 and T2?

Bright on T1; intermediate to bright on T2.

How does bone marrow appear on T1 and T2?

Very bright on T1; intermediate to bright on T2.

How does fat appear on T1 and T2 in the tissue table?

Bright to very bright.

How does gadolinium appear on T1?

Neuroradiology; restricted diffusion is an early sign of cerebral ischemia.

What is diffusion-weighted imaging mainly used for?

As early as 30 minutes after arterial occlusion.

How early can DWI detect ischemic stroke?

It is more sensitive to early changes than traditional T1 or T2 measurements.

Why is DWI useful after stroke?

Diffusion of water molecules.

What generates DWI contrast?

Cell membranes restrict it.

Why is water motion normally restricted in tissues?

Signal increases.

What happens to DWI signal when water diffusion is restricted by disease?

Pulse sequences that generate T1-, T2-, or PD-weighted images while suppressing signal from specific tissues.

What are inversion recovery images?

Short tau inversion recovery.

What does STIR stand for?

Fat.

What does STIR suppress?

High signal.

What can STIR show in edema such as a more severe stress fracture?

Fluid attenuated inversion recovery.

What does FLAIR stand for?

Fluid by using an inversion time that nulls fluids.

What does FLAIR suppress?

Lacunar infarction, MS plaques, SAH, and meningitis.

What conditions are listed as high-signal examples on FLAIR?

Fat signal suppression with bright areas around the tibia indicating stress fracture.

What does the STIR lower-leg example show?

Enhancement of the meninges at the tentorium and parietal region with evidence of dilated ventricles.

What does postcontrast FLAIR show in the meningitis example?

Neurologic and musculoskeletal imaging.

What are common uses of MRI?

Tumors, degenerative diseases, and trauma.

What can brain MRI detect/evaluate?

Multiple sclerosis.

What condition is specifically listed as a brain MRI use?

Soft tissues of the spine, disc herniations, and spinal cord injuries.

What does spine MRI evaluate?

By CT.

How are fractures usually evaluated?

To further evaluate ambiguous findings such as liver or adrenal masses.

Why might body MRI follow CT?

It images disease based on cellular function and physiology rather than physical tissue anatomy.

What is nuclear medicine's main imaging principle?

Injected, inhaled, or swallowed.

How is a nuclear medicine tracer administered?

A radioisotope targets the organ of interest and images are obtained with a gamma camera.

How are nuclear medicine images obtained?

Yes, to specific targets.

Can nuclear medicine deliver radiation therapy?

Demonstrates organ function, reactions are rare, relatively noninvasive, and offers patient ease and comfort.

What advantages of nuclear medicine are listed?

Intermediate to high cost, low to intermediate radiation dose, and long examination times.

What are nuclear medicine's cost, radiation dose, and exam-time characteristics?

The type of scan.

What is nuclear medicine prep dependent on?

No; exceptions include hepatobiliary scans and some GI exams.

Do most nuclear medicine studies require fasting?

An initial injection, a wait, and sometimes a repeat injection 1-4 hours later followed by the scan.

What timing may be required for nuclear medicine injections?

Examples include blood thinners before cisternogram and thyroid medications before a thyroid I-123 whole-body scan.

What medications may need to be held before nuclear medicine studies?

Diminished uptake/photopenia: abnormally low concentration of radiopharmaceutical.

What does 'cold' mean in nuclear medicine?

Increased uptake/activity: abnormally high concentration of radiopharmaceutical.

What does 'hot' mean in nuclear medicine?

The gallbladder and biliary tree.

What is a HIDA scan used to evaluate?

Hepatobiliary iminodiacetic acid.

What does HIDA stand for?

It is taken up by hepatocytes and excreted like bile.

What happens to HIDA?

99mTc-MAA.

What tracer is used for lung V/Q perfusion imaging?

Regional lung perfusion; particles become trapped in pulmonary arterioles.

What does lung scan show?

99mTc-RBC.

What tracer is used for GI bleeding scans?

Visualizing the source of a GI bleed.

What is 99mTc-RBC used for?

99mTc-MDP.

What tracer is used for bone scans?

Areas of osteoblastic activity and bone pathology.

What does bone scan show?

I-131.

What isotope is used for thyroid imaging?

Evaluating thyroid abnormalities or searching for metastatic thyroid cancer.

What is thyroid imaging used for?

Pulmonary embolism.

What does the abnormal lung V/Q scan in the deck indicate?

Positron emission tomography, a branch of nuclear medicine using positron emissions to produce detailed functional images.

What is PET?

Relatively costly; reimbursement can be an issue.

What are PET cost and reimbursement characteristics?

For complex questions regarding tissue function.

When is PET best used?

Cancer/metastasis, follow-up of chemo/radiation success, heart abnormalities, brain abnormalities, and other CNS disorders.

What are PET diagnostic uses listed?

Coronary artery disease and damage after a heart attack.

What heart abnormalities can PET evaluate?

Brain tumors, memory disorders, and seizures.

What brain abnormalities can PET evaluate?

NPO 6 hours prior; heart patients should have no caffeine for 24 hours prior.

What is PET preparation?

By injection, inhalation, or swallowing; then wait 30 minutes-1 hour, with the test taking another hour or so.

How is the PET tracer administered and what is the timing?

PET reveals cellular-level metabolic changes and can detect early changes; CT/MRI detect structural changes later as disease alters organs/tissues.

How does PET differ from CT/MRI?

Bone densitometry/dual X-ray energy absorptiometry.

What is DEXA/DXA?