ALU 101 Chapter 1

X-ray

beam of radiation emitted, scattered/absorbed in differing amt by diff tissues. 2-D images, several views may be necessary

Fluoroscopy

view moving parts of body in real time. continuous x-ray beam. used for both dx and tx, visual aid for minimally invasive surgery. often used w/ contrast agents

Contrast agent

enable better image of tubular/hollow structures. Barium, iodine, gadolinium based are most common. Used in x-rays, CT, MRIs.

Nuclear Medicine

small amounts of short-lived radioactive substance formulated to be absorbed by targeted tissues. radionuclide imaging uses scanning device to records distribution of radioactive material in the target organ. Useful for imaging bone and determination of thyroid and hepatobiliary fxn. Used to assess for CAD d/t ability to image aspects of cardiac physiology

Ultrasonography (US)

high-freq sound waves to image soft tissue and produce an ultrasound. transducer w/ transmitting gel placed on skin, sound waves transmitted into individual and echoes received back. Size of organ calculated by measuring time it takes for sound waves to travel from transducer to reflecting surface being studied and back to the transducer where they’re amplified and displayed on a monitor

Hyperechoic

US. tissues that reflect many sound waves. white on the image. fascia, connective tissue strands

Hypoechoic

US. tissues that reflect a few sound waves. gray on image. cartilage, muscles, lymph nodes

Anechoic

US. total absence of reflected sound waves. black on the image. bone, blood vessels, fat

Advantages of US over MRI and CT

ability to differentiate solid from fluid filled structures, lower cost, portability, accessibility, no exposure to ionizing radiation

Limitations of US

skill level of person, lower image resolution, “noise” when US waves hit gas and bone

Doppler US

used to measure velocity and direction of blood flow w/in heart and blood vessels by measuring changes in pitch/sound-wave freq. Useful for eval of venous insufficiency, blood clots, arterial occlusion, stenosis, valvular disorders and congenital defects

Computed Tomography (CT)

pass a rotating beam of x-rays into an individual and obtain thousands of point images at specific depths. produces cross-sectional 2D image. Computer can be used to manipulate stored data to produce rotating 3-D images. Much higher resolution than x-rays or US but higher dose of radiation

Electronic beam computed tomography (EBCT)

electron beam that allows such rapid acquisition of images that it can produce images of the coronary arteries despite motion of the heart

Multidetector CT scan (MDCT)

used in coronary artery calcium (CAC) scoring and in contrast-enhanced coronary CT angiography (cCTA)

Magnetic resonance imaging (MRI)

uses magnetic field to induce changes in proton spin w/in tissues. radio waves emitted at spec freqs that make atoms resonate and absorb energy. tissues then release weak radio wave that can be measured by a scanner and amplified. computer used to take cross-sectional slices of the body part part and reconstruc these images in 2 or 3-D

MRI vs. CT

MRI preferred when soft tissue resolution needed

Positron emission tomography (PET)

diagnostic images obtained from decay of a positron emitting redionuclide agent. Flourine-18/F-labeled deoxyglucose (FDG) is agent used for PET scans. FDG metabolized by active cells that utilize glucose for energy. Abnormal cells absorb and utilize FDG differently than normal cells.

PET scan uses

evaluate pulmonary nodules, lung cancer, colorectal cancer, esophageal cancer, head and neck cancer, lymphoma, melanoma. useful adjunct in dx of alzheimer’s, parkinson’s, epilepsy, hibernating myocardium

PET limitations

cost, accessibility, nature of radionuclide agent, elevated serum glucose or insulin lvls can adversely affect results, limited sensitivity for defining tumors smaller than 10mm, high degree of expertise required for proper interpretation

Angiography

imaging study used to visualize major blood vessels in body including heart, carotids, brain, kidneys, lungs, and legs. gold standard for vessel imaging and is the study of choice when intervention is necessary

Endoscopy

investigation of cavities and hollow organs

Acute head trauma (type of diagnostic test)

CT

Transient ischemic attack, TIA (type of diagnostic test)

CT/CTA, MRI/MRA, carotid ultrasound

Computed tomography angiography (CTA)

advanced version of angiography for blood vessel imaging, less invasive and less risk

Magnetic resonance angiography (MRA)

advanced version of angiography for blood vessel imaging, less invasive and less risk. blood vessel and blood flow abnormalities

Acute hemorrhage, acute hemorrhagic stroke (type of diagnostic test)

CT/CTA, MRI/MRA

Brain Abscess (type of diagnostic test)

CT or MRI

Sinus disease (type of diagnostic test)

CT, MRI

Hydrocephalus (type of diagnostic test)

CT, MRI, Cisternography

Cisternography

medical imaging procedure used to visualize the flow of cerebrospinal fluid (CSF) in the brain and spinal cord

Anyeurysm, ateriovenous malformation (type of diagnostic test)

MRA, CTA

Acute non-hemorrhagic stroke (type of diagnostic test)

CT/CTA, MRI/MRA, TCD ultrasound

Brain/nervous system tumor or metastasis (type of diagnostic test)

CT/MRI

Multiple sclerosis (type of diagnostic test)

MRI

Alzheimer’s (type of diagnostic test)

MRI, PET/CT scan

Carotid duplex ultrasound

measures focal blood flow velocities in the carotid artery. provides estimate of carotid stenosis and residual lumen diameter

Transcranial doppler ultrasound (TCD)

used to image intracranial vessels and assess their patency. Can dx intra-arterial stenosis in real time in pts w/ stroke

Cerebral angiography

catheter inserted into femoral artery and threaded thru aorta to inject contrast into targeted arteries of head and neck. higher risk. not used as screening test

single photon emission computed tomography (SPECT)

similar to PET. for functional brain imaging. uses gamma camera, computer, IV radionuclide to look at blood flow and provide 3D mages. for dx of dementias and neurodegenerative disorders, less sensitive than PET

lumbar puncture/spinal tap

insert needle in between vertebrae to withdraw cerebrospinal fluid for testing. dx of subarachnoid hemorrhage, infection, MS, guillian barre syndromeor tumors

tilt table test

evaluate syncope. pt fasts and then an IV line is inserted. pt lies flat and is strapped to table. After 15 mins, table tilted to 60-80 degrees causing venous blood to pool in legs and can trigger vasovagal syncope

electroencephalography

measures and records low voltage electrical activity produced by the brain. electrodes placed at defined points on the scalp