Transcript Radiology Modalities ppt - Logan Radiology

Jeff Binder R.T. (R)
STRENGTHS
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WEAKNESSES
Readily available
Low cost
Well known uses
Best line pair performance
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False negatives (fx)
Ionizing radiation
Poor resolution
Poor soft tissue
visualization
Poor spacial localization
C1/c2, c6/c7 hard to
visualize
Attenuating technology
 Rule
out advanced imaging
 Introductory study
 Evaluates IVF well
 Not good for central canal stenosis
 Xray
images taken in “sections” (slices)
 Blurs areas that are not of interest
 Similar strengths and weaknesses as
plain film
 Attenuating technology
 Xray
images taken of spinal cord after
radiopaque contrast is injected
 When used with CT it is the best tool to
visualize central canal stenosis
 Dr. looks for displacement of contrast on
xray
 Attenuating technology
 Headache
(most common)
 Infections
 Arterial
bleeding
 Arachnoiditis
 First
contrast used was air
 Technetium
99 radio isotope used
 Emission technology (from the patient)
 “hot spots” on scan are osteoblastic
activity
SPECT: Single Photon Emission
Computerized Tomography
Phosphate used as carrier molecule
PET: Positron Emission Tomography
Glucose used as carrier molecule
 Attenuating
technology
 Computer generated pictures
 Hounsfield Units
 Pixels and voxels
 Volume averaging used
 Slice thickness scout films used
STRENGTHS
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Widely available
Improved soft tissue
visualization
3d imaging
Accurately measure a
variety of structures
Image manipulation
possible (bone and soft
tissue windowing)
May be combined with
myelogram for canal
stenosis exam
WEAKNESSES
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Ionizing radiation
Higher cost
Intracranial artifacts
Artifacts secondary to
metallic implants
Radiation dose
 Sound
waves used to form images
 No radiation
 Readily accessible
 Lower cost
 Interact with patient
 Emission
technology (from the patient)
 Hydrogen molecules used for emission
 Cortex of bone=black
• Due to lack of hydrogen (water molecules)
 Evaluates
Physiology
 Spinal
fracture
 Soft tissue injury
 Skeletal survey for metastasis
 Post traumatic complications
 Peripheral entrapment
 Central canal stenosis
 Intracranial abnormalities
 Vascular imaging (MRA first choice)
 Magnet
(field) strength depicts image
quality
• 1.5 tesla magnetic minimum
• Larger the magnet= better image quality
 RF
coils are placed on or near the patient
to excite the tissue
 Larmor equation
• Frequency of procession= gyro magnetic ratio x strength of
field
White= high signal, Many H+ emitting
signal
Black= low signal, No H+ emitting signal
Tr= Repetition time
Te= echo time
 Cortex=black
 CSF=black
 Fat=white
 Tr=
200-600ms
 Te= 25ms
 Cortex=black
 CSF=white
 Tr=
~1500+ ms
 Te= 50+ ms
 BOLD:
Blood Oxygen Level Dependant
 Physiology presented
• Cortical activation
• Retinotopic organization of the visual cortex
• Cerebral basis for language
• Mapping of the motor cortex
• Memory
• Studying psychiatric disorders
 Advantages
over PET
• No ionizing radiation, less expensive, widely available, studies can be
frequently repeated
 Fake
functional
 Computer tricks to make a study look
like a motion study.
 Really a series of static images