Transcript Materials covered in lecture - School of Medicine Department of

University of South Carolina
School of Medicine
RADIOLOGY
ICM
Introduction To
Clinical Medicine
Francis Neuffer M.D.
U.S.C. School of Medicine
Radiology Website: http://radiology.med.sc.edu
GOALS
Overview
• Image creation
• Different modalities
• Strengths and weakness
RADIOLOGY TOOLS
X- RAY
ULTRASOUND
NUCLEAR MEDICINE
MAGNETIC RESONANCE
COMPUTED TOMOGRAPHY
3
HOW IS IMAGING DONE?
 IONIZING RADIATION
X-ray, CT, Nuclear Medicine
 SOUND WAVES
Ultrasound
 MAGNETIC FIELDS / RADIO WAVES
Magnetic Resonance
4
X-ray, visible light and radio waves are all
electromagnetic radiation and only vary in frequency.
X-RAY
X-ray beam
 High Energy Photon
--Kilo Electron Volts
 Ionizing Radiation
 Exposes Film /
Detector
 Projection Data
detector
6
X- RAY
• Bone
• Soft
tissue
• Fat
• Air
UPPER GI--(GASTRO INTESTINAL)
STOMACH
ORAL BARIUM CONTRAST
WITHOUT CONTRAST-plain or
scout film
ARTERIOGRAM
INTRAVASCULAR IODINE CONTRAST
8
COMPUTED
TOMOGRAPHY
HIGH ENERGY PHOTON
IONIZING RADIATION
EXPOSES DETECTOR
TOMOGRAPHIC DATA
9
SOFT TISSUE WINDOW
LUNG WINDOW
THE
HOUNSFIELD SCALE
-1000
-20 - -80
0
+20 - +80
AIR
1000
BONE
WATER
FATTY TISSUE
SOFT TISSUE
LT
ARTERIOGRAM
CT WITH INTRAVENOUS IODINE CONTRAST
WITHOUT
CONTRAST
INTRA-ARTERIAL IODINE CONTRAST
AXIAL
SAGITTAL
ENHANCING RING LESION
NON-CONTRAST
STUDY
IV IODINE CONTRAST
STUDY
NUCLEAR MEDICINE
 High Energy Photon
 Ionizing Radiation
--Radiopharmaceutical
 Dynamic / Physiologic
16
Normal Bone Scan
NORMAL LUNG SCAN
NUCLEAR MEDICINE
Exposure
•
•
•
Physical half-life
Biological half-life
Effective half-life
•Definitions:
•The effective half-life for a radionuclide is the time needed for the
compound to be decreased by 50%. This is the combined biological halflife and the physical half-life .
•• The biological half-life is excretion dependent.
•• The physical half-life is due to nuclear decay.
RADIATION
• Ionizing radiation:
X-Ray
CT
Nuclear Medicine / PET
• Non-ionizing radiation:
US
MR
WHICH
ONE
DOESN’T
THAT’S MORE LIKE IT.
FIT?
22
RADIATION RISK
•
CT scans contribute approximately 45% of the U.S.
population's collective radiation dose from all medical xray examinations.
•
CT is the LARGEST contributor to medical exposure to
the U.S. population.
Estimated Number of CT Scans Performed
Annually in the United States
Increased CT Utilization





Indications
Availability
Certainty
Speed
Demand—patient / physician / insurance
Emergency Radiology 2006 Oct: 13(1); 25-30
RADIATION RISK
IONIZING RADIATION
Ionizing radiation can cause free radicals which
can break DNA.
Incomplete DNA repair can be lethal to cell or
increase cancer risk or increase genetic defects
in fetus.
RADIATION DOSAGE
RADS
REMS
GRAYS
SIEVERTS
NCRP 160 Report (2009)
Background Population
Radiation
Adapted from: Radiology 2009;253:293-296 Figure 2
RADIATION DOSAGE
CXR= 1/100 Background Radiation/Yr.
CT Scan= 1-4x Background Radiation/Yr.
Denver = 2x Background Radiation/Yr.
RADIATION RISK
Deterministic effects—dose dependent.
Stochastic effects—probability of event
DETERMINISTIC
THRESHOLD - DOSE RELATED
• Cataracts, Skin Erythema & Burns,
(very rare -interventional procedures)
• Acute Radiation Sickness-(Radiation
accidents)
Bone marrow-depression
GI tract sloughing
Cerebral edema
Death
STOCHASTIC EFFECTS
LOWER DOSE:
• probability increase - population
effect
• Cancer incidence
• Hiroshima Nuclear Bomb survivors
Excess Risk of Cancer
50-100 mSv exposure
Nuclear Bomb Survivors
Small Statistical Increased
Risk
The estimated lifetime cancer mortality risks from a single fullbody CT examination at age 45.
CT DOSE IS IN RANGE OF
HIROSHIMA BOMB SURVIVORS
DOSE
•
•
There is an excess cancer risk seen in
large groups of Hiroshima survivors.
•
Statistically CT scans WOULD increase
risk of cancer.
PEDIATRIC EXPOSURE
• Children are considerably more sensitive to radiation than adults by
about 3 times.
• Children also have a longer life expectancy than adults, resulting in a
larger opportunity for effect.
• Radiation-induced cancers effects delayed 1 to 2 decades or longer
after exposure.
• Children can receive a higher dose( ADULT SCAN) than
• necessary.
• Thus risk for developing a radiation-related cancer can be several times
higher for a pediatric patient.
FOR MORE
PHYSICS…
www.youhavenolife.com
University of South Carolina
School of Medicine
RADIOLOGY
ICM
Introduction To
Clinical Medicine
Francis Neuffer M.D.
U.S.C. School of Medicine
Radiology Website: http://radiology.med.sc.edu
NO IONIZING RADIATION
 SOUND WAVES
Ultrasound
 MAGNETIC FIELDS / RADIO WAVES
Magnetic Resonance
ULTRASOUND
• Sound Wave - high
Frequency-megahertz
• No Ionizing Radiation
B Mode-brightness
Most common use
Presents “real time” image
 Ultrasound Sector Scanning
ULTRASOUND
ideal for fluid filled structures
Gallbladder
Kidney
Obstetrics
42
PLAX VIEW OF THE HEART
CAROTID ARTERY
color doppler
MAGNETIC RESONANCE
• HYDROGEN PROTONS ALIGN
IN MAGNETIC FIELD
• RADIO FREQUENCY
EXCITATION and
TRANSMISSION
• NO IONIZING RADIATION
RF
MR SIGNAL
T1 SCAN
T2 SCAN
SCANS ARE MADE TO SEPARATE TISSUE BASED ON
THEIR T1 AND T2 TIMES.
MRI OF THE LUMBAR SPINE
Sagittal
views
MR ANGIOGRAPHY WITH
GADOLINIUM
Standard catheter
Angiogram
MR SCAN + GADOLINIUM
CONTRAST
Sella Mass
IMAGING
PROSAND CONS
 IONIZING RADIATION
X-ray, CT, Nuclear Medicine
 SOUND WAVES
Ultrasound
 MAGNETIC FIELDS / RADIO WAVES
Magnetic Resonance
X-RAY
PRO’S
 Available
 Inexpensive
 General Skills
CON’S
 Ionizing Radiation
 Contrast Issues
 Projection Data
IODINE and BARIUM
Contrast Issues
IODINATED AGENTS are WATER SOLUABLE and can be given by
oral or vascular routes.
With IODINE, there is a potential for RENAL TOXICITY in certain
patients and ALLERGIC REACTIONS can occur.
BARIUM is a GI CONTRAST. It is a particulate inert material.
Therefore it is not a vascular agent. It could be a problem if it
perforated into the peritoneum.
CT SCANNING
PRO’S
• Available
• Fast
•Sectional data
• Soft tissue detail
CON’S
• Radiation
• IV Contrast
• Cost
NUCLEAR MEDICINE
CON’s
PRO’s
•
•
•
Physiologic data
Quantifiable
Tissue specific
•
Limited anatomy
•
Radiation
•
Speed / Motion limited
•
Cost
Ultrasound
PRO’S
• non-ionizing radiation
• not motion limited
• portable / multiplanar
• lower cost
CON’S
• operator dependent
• Limited FOV
MAGNETIC RESONANCE IMAGING
PRO’S
•
Soft tissue resolution
•
No iodine toxicity
•
No ionizing radiation
MAGNETIC RESONANCE IMAGING
CON’S
•
•
•
•
•
•
Cost / Availability
Motion
Air- lungs / bowel
Bone- skeleton / calcium
Hemorrhage /
hemoglobin
MAGNETIC RESONANCE
IMAGING
CON’S
•
•
ICU patients and Claustrophobia
Metal artifact
•
•
•
•
•
RF Energy – pacemaker overide
Magnetic field - aneurysm clips –
Occular metal -missile effect
Nephrogenic Systemic Fibrosis
Gadolineum toxicity in renal failure
GADOLINIUM CONTRAST
•Physiology similar to iodine
•Blood pool and tissue enhancement
•MINIMAL allergic issue
•TOXICITY in patients with renal failure
•Nephrogenic Systemic Fibrosis
GADOLINIUM RISK?
RADIATION
• Ionizing radiation:
X-Ray
CT
Nuclear Medicine / PET
• Non-ionizing radiation:
US
MR