Diagnostic imaging quiz 1

The four radiology rights

Do the right exam

Do it the right way

Do it on the right person

Do it at the right time

ALARA

Radiology exams are performed based on this principle

“As low as reasonably achievable”

Radiology

The science dealing with X-rays and other high-energy radiation, especially the use of such radiation for the diagnosis and treatment of disease.

Radiologists are consult physicians.

If you are unsure of the best test to order for any given pathology, ask the radiologist.

Illuminators (view boxes)

The “old” standard

PACS

Picture archiving and communication system

Ability to store and electronically share information

Basics of image viewing

Identify:

Type of study done?

Patient name, age, DOB

Date and time of exam

Left/Right markers

Previous films?

In AP, PA, and oblique projections

Viewed as if the patient is looking at you

Exceptions:

Hands, wrist, feet: viewed as if you are looking at your own

Radiographic densities

The human body is composed of four basic radiographic densities:

Air, Fat, Water (soft tissue and blood), and Bone

Summation density

reflects the density and thickness of intervening structures (two bones overlapping appear brighter than an individual bone)

Radio-opaque/hyperdense

Absorbs photons, demonstrated on images as white

Metal and bone are examples

Radiolucent/hypodense

Materials that allow x-rays to pass through with minimum absorption appear black

Fat and air are examples

Radiographic densities

Four out of 5 densities

PA view

Beam goes back to front

AP view

beam goes front to back

PA vs AP

X-ray comparison

Lateral/side view

x-ray beam passes from one side of the patient or body to the other

Decubitus

Patient who is lying down, with the central ray horizontal. Taken front to back. Useful when looking for abnormal fluid or air collections. Air rises, fluid falls.

Oblique

Rotated view. this is left lateral oblique. Useful for shoulder joint dislocation or fractures

Grashey view

Oblique shoulder

Summary of positions

Radiology report breakdown

Indication- Why are we doing the study?

Procedure- What study is being done?

Comparison- what previous imaging do they have that we can compare?

Findings- What was evaluated on the study?

Impression- what was the outcome of the study?

Signature- Radiologist's signature with time stamp and date

Radiology modalities

X-ray/mammography

Fluoroscopy (OR)

CT scan (lot of radiation)

MRI (expensive, long, no radiation)

Nuclear medicine (invasive)

Ultrasound (miss a lot)

Radiation

Ionizing radiation in large doses is known to produce cell mutations that can lead to forms of cancer and cell anomalies.

Generally accepted principle is ONLY MEDICALLY NECESSARY diagnostic exams should be performed

Teratogens

Drugs, chemicals, infections, or other environmental factors that can cause abnormal fetal development.

Studies using x-ray should be avoided during pregnancy/teratogenic times

Radiation basics

1. Routine radiography (x-ray) requires two views for most diagnoses

2. Radiation has a cumulative effect, benefit should outweigh risk

3. Most radiosensitive body parts are eyes, thyroid, breasts, and gonads (lead covers)

Radiography/X-ray/Plain films

medical images that are “shadows” projected on a flat plate when x-rays are passed through the patient

x-ray/mammography compared to other modalities

Pros:

Low cost

Generally low radiation dose

Fast and available

High spatial resolution- ability to differentiate two adjacent structures as being distinct from one another

Cons:

Misleading appearance of overlapping structures

Poor soft tissue contrast resolution- ability to distinguish between differences in intensity in an image

x-ray common uses

Evaluation of bones- dense bone is surrounded by muscle and fat

Fractures, bone tumors

Initial evaluation of abdominal pain

Evaluation of solid organs in the abdomen is limited, but the bowel gas pattern can be readily seen (alterations in pattern may indicate disease)

CXR- due to different densities of internal structures

can get a detailed exam of the lung parenchyma, pulmonary blood vessels, and of the heart

Plain x-ray prep?

Non routinely needed

Patient education: tell patient x-ray will take 5-10 minutes

Mammography

x-ray of the breast

Patient ed/prep:

No powders, perfumes, lotions, or deodorant prior to exam (summation density, lump)

Fluoroscopy

Live action x-ray viewed on a closed-circuit TV

Used for GI, GU, skeletal, pulmonary system imaging and angiography/interventional procedures

To evaluate specific areas of the body, includes the bones, muscles, and joints, as well as solid organs, such as the heart, lungs, or kidneys

Fluoroscopy examples

Barium x-rays (swallowing test, contrast GI test, obstruction)

Cardiac catheterization (dilate BV, make sure no blockage)

Arthrography (leakage in joint space)

Intravenous pyelogram (kidney stones or infection)

Hysterosalpingogram (fertility test, through cervix- fallopian tubes)

Percutaneous vertebroplasty (putting vertebrae together)

Cardiac catheterization

Fluoroscopy used as an adjunct to see the flow of blood through the coronary arteries in order to evaluate the presence of arterial blockages

Endoscopic retrograde cholangiopancreatography (ERCP)

Endoscope is passed into the duodenum and contrast is injected into the bile ducts and/or pancreatic duct

Upper GI (barium)

Evaluation of the esophagus, stomach, and duodenum using oral contrast.

Detect polyps, masses, malpositioned bowel, motility problems, GE reflux, and hiatal hernia

Fluoroscopy uses

Enema exam (go up the rectum)

Evaluation of the colon using rectal contrast

Useful to detect small polyps or other precancerous lesions

Barium swallow

Evaluation of the mouth, esophagus and swallowing mechanism using oral contrast

Fluoroscopy prep/patient ed

Depends on what is being imaged

Usually, for GI studies NPO for 6 hours before study

For rectal contrast, you may need bowel prep

For spinal exams- no prep

Computed Tomography = CT scan

Combines x-ray and computer technology- digital processing is used to generate a 3D image of the inside of an object from a large series of 2D images taken

Hounsfield units

Characterizes the relative density of a substance (amount of x-ray radiation absorbed by each element in tissue)

Bone/metal: 1000 HU (brightest)

Liver: 40-60 HU

White matter: 46 HU

Grey Matter: 43 HU

Blood: 40 HU

Muscle: 10-40 HU

Kidney: 30 HU

CSF: 15 HU

Water: 0 HU

Fat: -50 to -100 HU

Air: -1000 HU (darkest)

Hounsfield scale

CT window- range of the densities that are compressed into shades of gray for viewing

Soft tissue, bone, lung window

CT imagine Pros/Cons

Intermediate cost

Much improved soft tissue evaluation compared to plain radiography

Fast and available

Higher radiation dose than plain x-ray (10-100 times more)

Axial CT images

Presented as if the viewer is standing at the foot of the patient’s bed; the patient’s right is to the viewer’s left; the anterior aspect of the patient is toward the top of the image

Coronal CT images

Viewed the same way that most radiographs are viewed: the images are oriented as though the patient is looking at you

Sagittal CT images

Shown as though the patient is looking towards the viewer’s left

High resolution CT scan

Enhances resolution to show parenchymal abnormalities that may not show up on x-ray

Assesses interstitial lung disease (pulmonary fibrosis), chronic infiltrative lung disease, pneumoconiosis, bronchiectasis, and emphysema

Patient may be placed in the prone position to enhance the lung bases

Common uses for CT

Many- used extensively for chest, abdominal, neurological, and musculoskeletal disease

Chest CT

—for evaluation or detection of lung cancer, pathologies of the lung

—CT guided biopsies of chest lesions are also commonly performed

Abdominal and pelvic CT

Evaluating the abdominal organs for pathology such as acute abdomen or trauma

Head and neck CT

Evaluating traumatic injury or to rule out bleeding or fracture, intercranial bleeds

CT scan prep

May be performed with or without contrast (or both)

The contrast may be IV, oral, rectal, or a combo

May need to arrive 1 hour before exam

If scanning the abdomen/pelvis = NPO for 4 hours prior to the study

Fluoroscopy pros/cons

X-ray done in real-time: shows moving images of the internal structures of a patient

Similar radiation dose compared to CT

Low to intermediate cost

Operator dependent

Magnetic resonance imagine (MRI)

MRA = magnetic resonance angiography

No x-rays used

Relies on different # and behavior of hydrogen ions in diff tissues of the body to provide contrast

Uses a magnetic field and radiofrequency pulses to provide imge

Most MRI machines are 1.5T or 3T devices

MRI pros/cons

Higher cost

MRI has better soft tissue contrast resolution than CT

Long study time, very sensitive to patient motion

No exposure to ionizing radiation

MRI precautions

Remove anything potentially magnetic from the room and from the patient

May be contraindicated in patients with:

Claustrophobia

Metal clips, pacemakers, spinal cord stimulators

Cardiac defibrillators

MRI- orthopedic hardware

Should be ok with ortho hardware, prosthetic valves, titanium wires, and coronary stents

Ask patient if they have a card given to them after the implant

MRI: T1 weighted images

Highlights fat as bright

Muscles as intermediate

Water (blood, CSF) as dark

Brain- gray matter is darker than white matter

MRI: T2 weighted images

Highlights water as bright

Fat as slightly less bright

Muscle as intermediate

Brain- white matter is darker than gray matter

Comparison of the typical tissue appearances on T1 and T2

Diffusion weighted imaging (DWI, type of MRI)

Main use is neuroradiology, where restricted diffusion is an early sign of cerebral ischemia (stroke)

—can detect ischemic stroke as early as 30 minutes after arterial occlusion

—more sensitive to early changes after a stroke than more tradition MRI measurements such as T1 or T2 relaxation rates

DWI uses the diffusion of water molecules to generate contrast in MR images

Motion is normally restricted in tissues because of cell membranes

Disease that result in restricted diffusion of water molecules result in increased signal on DW images

Inversion recovery images

Pulse sequences are used to generate T1-, T2, or PD-weighted images while suppressing signal from specific tissues

STIR (short tau inversion recovery)

—Suppresses fat will give a high signal in edema such as in more severe stress fracture

FLAIR (fluid attenuated inversion recovery)

—suppresses fluid by setting an inversion time that nulls fluids will give a high signal in lacunar infarction, MS plaques, SAH, and meningitis

STIR MRI

Coronal STIR (fat signal suppressed) MRI of a lower leg showing high signal (bright) areas around the tibia as signs of stress fracture

FLAIR MRI

Postcontrast. FLAIR MRI of a case of meningitis

Shows the enhancement of meninges at the tentorium and in the parietal region, with evidence of dilated ventricles

Comparison of MRI’s

Common uses for MRI

Brain, spinal cord, spine, orthopedic injury

Used in neurological and musculoskeletal imaging

Brain MRI

—used to detect and evaluate tumors, degenerative diseases and trauma

—Multiple sclerosis (MS)

Spine MRI

—evaluating soft tissues of the spine, disc herniations and spinal cord injuries, fractures are usually evaluated by CT

Body MRI

—done as a follow-up exam to further evaluate ambiguous findings on CT, such as liver or adrenal masses

Joint MRI

—evaluating soft tissues injuries, such as ACL or meniscal tears

MRI/MRA prep

No special prep but remember those who may be excluded from exam

Let patients know

—need to be still

—in an enclosed space depending on body part images

—scanners are loud

What is nuclear medicine?

Ability to image the extent of a disease process in the body, based on the cellular function and physiology rather than relying on physical changes in the tissue anatomy

Uses radioactive isotopes- radioactive tracer is injected, inhaled, swallowed by patient - radioisotope targets organ of interest - then images obtained with a gamma camera

Can also be used to deliver radiation therapy to specific targets

—Thyroid mets, lymphoma

Nuclear med pros/cons

Demonstrates organ function

Reactions are rare

Relatively noninvasive

Patient ease and comfort

Intermediate to high cost

Low to intermediate radiation dose

Long exam times

NMR scan prep?

Patient prep is dependent on type of scan being done

Most don’t require fasting

—Exception: hepatobiliary scans, some GI scans

Many require initial injection, patient waits, and then repeat injection may be 1-4 hours later with scan then

Patient may need to hold meds prior (for specific organ scans)

—Bloos thinners held before cisternogram, hold thyroid I123 whole body scan

Important terms in NM

Cold

—Diminished uptake, photopenia: refer to areas of abnormally low concentration of radiopharmaceutical

Hot

—Increased uptake, increased activity: refer to areas of abnormally high concentration of radiopharmaceutical

Hepatobiliary scans

HIDA- taken up by the hepatocytes and excreted like bile, used to evaluate the GB and biliary tree

Lung-ventilation perfusion imaging

99mTc-MAA- these particles get trapped in arterioles in the lungs to show regional perfusion in the lungs

**99 = nuclear med

Common NM scan- GI bleeding scans

99mTc-RBC- radioactive labeled RBCs that can be used to visualize the source of a GI bleed

Common NM scan- Bone scans

99mTc-MDP- taken up in areas of osteoblastic activity and is used to evaluate bone pathology, CANCER (blast)

Common NM scan- Thyroid imagine

NUCLEAR MED ONLY SHOWS FUNCTION-not anatomy

I-131 - take up by the thyroid tissue, used to evaluate thyroid abnormalities or to search for metastatic thyroid cancer

Normal lung (V/Q, ventilation and perfusion) scan

Abnormal lung scan= PE

Normal bone scan vs abnormal bone scan with metastisis

Positron emission tomography=PET scan

A brand of nuclear medicine that uses positron emissions to produce detailed functional images

Relatively costly

Reimbursement can be an issue

Best used for complex questions regarding tissue function

PET diagnostic uses

Detect cancer/metastasis

Follow up to see if chemo/radiation treatments are successful

Heart abnormalities (coronary artery disease and damage following an MI)

Brain abnormalities (brain tumors, memory disorders, seizures)

Other central nervous system disorders

PET prep/patient education

NPO 6 hours prior

No caffeine for 24 hours prior in heart patients

Injection, inhalation, or swallow tracer then wait for test for 30 mins-1 hour

Test may take another hour or so

Pet vs CT or MRI scan

PET scan reveals the cellular level metabolic changes occurring in an organ or tissue -thyroid, cancers, brain

PET scan can often detect very early changes whereas a CT or MRI detect changes later as the disease begins to cause changes in the structure of organs or tissues

Active bleed- CT is faster

Structure: CT

Function: NM, PET

Ultrasound (cheap and easy)

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

Used for peds, OB, vascular imaging, ortho, renal, scrotal, ovarian

Used for guidance of interventional procedures (biopsies, thoracentesis)- good for use in real time

Sonogram = image produced

U/S pros and cons

Low cost

No radiation

Operator dependent

Good soft tissue evaluation in specific clinical scenarios (cyst vs mass)

Fast and readily available

Echogenicity

Level of gray or brightness on an ultrasound image

Described in relation to surrounding tissues

Isoechoic

Uniform in color

Liver

Hypoechoic

abscesses, fatty tissue

Darker = less echoes

Hyperechoic

Bone, kidney/gallbladder stone

lighter = more echoes

Anechoic

no echos

Bladder, cystic fluid, gallbladder

Artifacts-enhancement

Acoustic enhancement- sound travels through fluid uninterrupted, so the echoes deep to a fluid collection are brighter than the adjacent tissue

In poorly attenuating objects such as a cyst, the echoes returning from regions deep to the object are of higher amplitude

Artifacts- shadowing

A structure that blocks the sound wave causes acoustic shadowing (gallstones)

Strongly attenuating or highly reflective surface, the returning echoes posterior to the structure are decreased in amplitude

U/S prep

Vascular studies = no prep

Abdominal = NPO for 6 hours prior

Trans-abdominal pelvic= drink 32 oz of water a half hour prior (requires a full bladder)

Fetal U/S

DEXA scan

DEXA or DXA scan = bone densiometry = dual x-ray energy absorptiometry

Type of x-ray: measuring bone mineral content and density (BMD) od specific skeletal sites

Used to diagnose osteoporosis and assess fracture risk

Relatively inexpensive

simple for patient and operator

Used for planning and follow up of treatment

DEXA prep

No calcium supplements for 24 hrs prior

Scan only takes 10-15 minutes

Peripheral or p-DEXA

Scan measures bones on the body’s periphery- such as the heel, wrist, or finger

Should not be used for diagnosis or tracking progress from year to year (IS A SCREENING TEST)

Central DEXA

Bone mineral density score in lumbar spine and femoral neck

Provide an accurate diagnosis and method of tracking progress in bone growth or loss from year to year

T-SCORE

Indicated patients BMD in standard deviations above or below that of mean for young adult women

For each 1 SD in T score, fracture risk nearly doubles

Osteoporosis: below -2.5

Osteopenia: between -1 and -2.5

Normal score>-1

Z SCORE

Used for children, young adults, men, pre-menopausal women

Compares your bone density to the average bone density of people your own age and gender

Ex. If you are a 50 year old male, a Z score compares your bone density to the average bone density of other 50 year old males

DEXA scan example

Measurements of the lumbar spine demonstrate a total T-score in the range of osteopenia