Introduction to Medical Introduction to Medical ImagingImaging

Jeff Benseler, D.O.Jeff Benseler, D.O.

ObjectivesObjectives

Medical Imaging: What to expect in Medical Imaging: What to expect in your first 2 years at OUHCOMyour first 2 years at OUHCOM

Overview: How do x-rays create an Overview: How do x-rays create an image of internal body structures?image of internal body structures?

What are the advantages of CT, MRI What are the advantages of CT, MRI and Ultrasound?and Ultrasound?

Medical Imaging (Radiology)

Nearly all medical disciplines utilize medical imaging

As you move from block to block we will learn: How each modality works to create an

image of internal body structures Selecting the best imaging tests for a given

clinical presentation Develop a stepwise repeatable pattern of

evaluating medical images

Method for learning medical image interpretation

Most blocks will contain recorded presentations

These recordings last approximately 10 to 30 minutes each

Most blocks will have 2 to 4 recordings to view before the live class

The recordings can be viewed and reviewed as needed anytime 24/7

In class, we will learn by interpreting unknown cases

Questions about medical imaging

Please feel free to contact me with questions

My preferred contact method is email

benseler@ohio.edu

What are x-rays?

No mass No mass No charge No charge Energy Energy

X-rays are a typeof electromagneticenergy

Objective 2

How do x-rays passing How do x-rays passing through the body create an through the body create an

image?image? X-rays that pass through the body X-rays that pass through the body

render the image dark (black)render the image dark (black) X-rays that are totally blocked X-rays that are totally blocked

render the image light (white)render the image light (white) Air = low atomic # = x-rays get Air = low atomic # = x-rays get

through = image is dark (black)through = image is dark (black) Metal = high atomic # = x-rays Metal = high atomic # = x-rays

blocked = image is light (white)blocked = image is light (white)

5 Basic Radiographic 5 Basic Radiographic DensitiesDensities

AirAir FatFat Soft tissue/fluidSoft tissue/fluid MineralMineral MetalMetal

1.

2.

3.

4.

5.

Name these radiographic densities.

Optimal environment for Optimal environment for visual perception visual perception

Dedicated source of light (5 to 9 Dedicated source of light (5 to 9 mega pixel monitors)mega pixel monitors)

Darkened environment (like a movie Darkened environment (like a movie theater)theater)

Limit distractionLimit distraction

X-ray viewing station

Can you recognizeshapes and density?

Find the pathologyWhat clues do you have?

Medical Imaging InterpretationMedical Imaging Interpretation3 basic steps3 basic steps

First learn how each modality creates an image First learn how each modality creates an image of internal body structuresof internal body structures

Next, be able to accurately label normal Next, be able to accurately label normal anatomy (body structures)anatomy (body structures)

Then, search for structures that don’t belong Then, search for structures that don’t belong and for body structures that are abnormal in and for body structures that are abnormal in size, shape, position and/or densitysize, shape, position and/or density

History: 11 year old twistinginjury of the foot

Proximal

Distal

1.

2.

3.

Word bank: epiphysis, metaphysis, diaphysis, cortex, medullary cavity

Naming the parts of a long bone

Review: What are the 5 basic Review: What are the 5 basic radiographic densities from radiographic densities from

black to bright white?black to bright white? AirAir FatFat Soft tissue/fluidSoft tissue/fluid Bone/mineralBone/mineral MetalMetal

Summary for objective 2: Summary for objective 2: How do How do x-rays create an image of internal x-rays create an image of internal

body structures?body structures?

X-rays pass through the body to X-rays pass through the body to varying degreesvarying degrees

Higher atomic number structures Higher atomic number structures block x-rays better, example boneblock x-rays better, example bone

Lower atomic number structures Lower atomic number structures allow x-rays to pass through, example: allow x-rays to pass through, example: air in the lungsair in the lungs

Objective 3Advantages of CT, MRI and

Ultrasound

These modalities are cross sectional imaging

Cross sections are like slices

X-ray studies are a 2 dimensional representation of 3 dimensional structures can result in undesirable overlapping densities and artifacts

CT

Advantages Eliminates

overlapping densities Excellent resolution Excellent for

detecting intracranial bleeding

Excellent in the neck, chest and abdomen

Excellent for evaluating fractures

Disadvantages More expensive

than x-ray and ultrasound

Much more radiation

Dense bone (petrous ridge for example) and metal cause severe artifacts

CT scan of the abdomenX-rays used skin

What density is this?

air

MRI Advantages

No overlapping artifact

Excellent resolution Very good at

detecting fluid Excellent for imaging

the brain, spine and joints

No radiation Multiple imaging

tests within the same study (T1, T2, IR, GE)

Disadvantages Very expensive Patients cannot

have a pacemaker or ferromagnetic material

Slower to acquire images

(approximately 45 minutes)

Ultrasound Advantages

No radiation Portable Instantaneous (real

time) Excellent for cysts and

fluid Doppler ultrasound is

excellent to assess blood flow

Excellent for newborn brain, thyroid, gall bladder, female pelvis, scrotum, pregnancy

Disadvantages Does not work well in

large or obese patients Resolution less than CT

and MRI Air or bowel gas

prevents visualization of structures

Ultrasound of thegall bladder showinga gall stone

X-rays, CT, MRI and ultrasound help us see into the

body

Internal body structures are composed of varied material (fat, muscle, bone, gland) or contain air, water or minerals that “show up” differently on each type of imaging test.

Each modality has its own advantages allowing us the choose the best one for each medical circumstance.

What an excellent medical student at your level can

do:

Be able to describe how x-rays can create an image of internal body structures

Recognize and label the 5 basic densities on an x-ray

Be familiar with the advantages for CT, for MRI and for ultrasound