Introduction to Radiology

INTRODUCTION To IMAGING And RADIOLOGIC INTERPRETATION

James G. Smirniotopoulos, M. D. Professor and Chairman Department of Radiology and Nuclear Medicine USUHS

http://rad.usuhs.mil GOALS

Introduce Basics of Radiologic Imaging

Clinical Relevance of Basic Sciences

Glossary of Radiology Terms

Learn the Lingo

Become an Educated Consumer of Imaging

Learn Systematic Approach to CXR

Radiology

XR - X-Ray Images (films, digital, etc)

NM - Never Mind

US - Uncertain Signals

CT - Costly Tomography

More Radiology Income

Radiology

1. Radiography (XR Plain Films)

2. Nuclear Medicine (NM)

3. Ultrasonography (US)

4. Computed Tomography (CT)

5. Magnetic Resonance Imaging (MR, MRI) X-RAYS

1. A Form of radiant electormagnetic energy

2. Invisible to human eye

3. Passes through objects opaque to light

4. Causes fluorescence

5. Exposes film etc..

PHYSICAL PRINCIPLES of Radiology

1. Radiographic Density

2. Density Interface

3. Magnification

4. Motion Unsharpness

5. Superimposition (planar imaging like CXR)

6. Volume Averaging

(cross-sectional imaging e.g. CT, MR) RADIOGRAPHIC DENSITY

electron density

2. Thickness of object Thicker has more density BASIC DENSITIES

1. Gas (Air)

2. Fat and Lipid

3. Soft Tissue (Muscle)

4. Calcium (Bone)

5. Heavy Metal PRINCIPLES

1. Interface or edge seen only with density difference

2. "Silhouette Sign” (Don't See Interface) MAGNIFICATION

(farther object => larger shadow)

(closer tube magnifies more)

TERMINOLOGY

1. Direction of beam (e.g. PA chest) X-Rays pass from P to A

2. Body Part Closest to Film (E.G. Left Lateral Chest) IMAGING TECHNIQUES

2. Tube and film move around a focal point inside of patient
3. Patient remains stationary (usually!)

CONTRAST RADIOGRAPHY (Never say “Dye”)

Barium studies

2. Cholecystography (Gall Bladder)

3. Urography (Kidney function) (IV)

4. Pyelography (Retrograde)

5. Angiography/Venography

6. Arthrography

7. Hysterosalpingography

8. Lymphangiography (Rare)

ANGIOGRAPHY

1. Visualization of vessels

2. Important in surgery

3. Relatively invasive

(puncture vessel, inject contrast)

4. Complications

(hemorrhage, embolus)

5. Can be both diagnostic and therapeutic NUCLEAR MEDICINE

1. Radioactive isotopes

(Physiologic analogues)

2. Gamma rays from radioactive nucleus

3. Multiple images

Bolus injection
Bleeding (labeled RBC's)
Gall Bladder secretion

NUCLEAR MEDICINE

1. Skeleton

2. Liver

3. Lungs

4. Thyroid/Parathyroid, Adrenal

5. Heart

6. Kidney

7. Abscess and Inflammation PPT Slide
Cross-Sectional Imaging:

US - Ultrasound

CT - Computed Tomography

MRI - Magnetic Resonance Imaging

PET and SPECT Scanning

MagnetoEncephaloGraphy (MEG)

ULTRASOUND

1. Sound waves propagated through body

2. Waves reflected by tissue interfaces

3. Information processed and displayed (like RADAR)

4. "Echogenicity" characteristics Ultrasound

Solid vs. Cystic ULTRASOUND

1. No Ionizing Radiation

2. Ideal for OB/GYN, children

3. Morphologic and Dynamic information (peristalsis)

4. Doppler technique shows flow

5. Real-time Images (biopsy, fetal movement, heart, etc.) US TERMS

1. Anechoic

2. Hypoechoic

3. Echogenic

4. Hyperechoic US TERMS

1. Fluid:Anechoic

2. Tissue: Echogenic

3. Calcium, Air: Hyperechoic Cross-Sectional Imaging:

US - Ultrasound

CT - Computed Tomography

MRI - Magnetic Resonance Imaging

PET and SPECT Scanning

MagnetoEncephaloGraphy (MEG)

Computed Tomography

Low Cost
Available

Volume Averaging
X-Rays used to create image

CT Terms

1. Attenuation (density) (X-Ray beam is blocked)

2. Hounsfield Units (Inventor of CT)

3. Low Attenuation: Black (Gas)

4. High Attenuation: White (Bone) CT

(1500x Better Than X)

2. 1-2 second scan time is routine

3. $ 1 M Equipment

4. $200- $800 Scan Cost Cross-Sectional Imaging:

US - Ultrasound

CT - Computed Tomography

MRI - Magnetic Resonance Imaging

PET and SPECT Scanning

MagnetoEncephaloGraphy (MEG)

Magnetic Resonance Imaging

Cost (>>CT)
Generally Available (~ CT)

Metal and other artifacts
Magnetic Field and RF create image

Magnetic Resonance Imaging

Large Magnetic Field, RF (MHz range)

Measure PROTON Resonance

Cross-sectional Anatomy

Sensitivity vs. Specificity

Flow Imaging (MR Angiography)

Speed and Resolution ~ CT PPT Slide
PPT Slide
No Magnetic Influence
Magnetic Field Effect
MR Terms

Signal Intensity

Short T1 is BRIGHT

Proton Density (in between)

Long T2 is Bright

Indications for MR

White Matter (Leukoencephalopathy)

Acute Brain Infarction?

Spinal Cord Problems

Posterior Fossa

Pediatric (or any ? Of Radiation)

Head Trauma

Liver

“Normal” CT Contraindications for MR

Cranial Metal (Head, Brain, Orbit)

Pacemaker (sensing)

Hx of Metal Work, Shrapnel, etc

Claustrophobia MR Pulse Sequence

The Recipe for the MR Scan MR Pulse Sequence

“Recipe” for Cooking MR Scans

TR - Repetition Time (between “sets”)

TE - Echo Time (delay for “listening”)

IR - Inversion Time MR Pulse Sequence

“Designer Acronyms”

MOTSA, STEAM, etc.

Pulse Sequences from Physics

Physics from PhD’s and MD’s

(Spin Doctors of Radiology) MAGNETIC RESONANCE IMAGING

1. Signal Intensity (S.I.) related to "proton density" and resonance properties of those protons MAGNETIC RESONANCE IMAGING

b. Cortical bone
c. Flowing blood
d. Fibrous tissue
e. Water/Edema (on T1W)

MAGNETIC RESONANCE IMAGING

b. Hemorrhage
c. High protein
d. Melanin
e. Microcalcifications
f. Water/Edema (on T2W)

MRI ADVANTAGES

1. No ionizing radiation

2. Multi planar imaging

3. High contrast resolution

4. Non-invasive vascular imaging ROLE OF RADIOLOGIST

1. Identify abnormality (Nl or Abnl)

2. Characterize abnormality

3. Extent of disease (Staging)

4. Differential diagnosis

5. Suggest further work up ROLE OF CLINICIAN

1. Relevant history

2. Consult with radiologist

3. Pursue further work up

4. Treat or refer patient RADIOLOGIST:

An in Vivo Gross Macroscopist

PATHOLOGIST:

An in Vitro Microscopist

BASIC RADIOLOGIC SIGNS

1. Size

2. Number

3. Density/Intensity/Echogenicity

4. Shape

5. Position

6. Architecture/Texture

7. Function THE END
Cross-Sectional Imaging:

US - Ultrasound

CT - Computed Tomography

MRI - Magnetic Resonance Imaging

PET and SPECT Scanning

MagnetoEncephaloGraphy (MEG)