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Introduction to Radiology

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by

Grace Bellinger

on 24 June 2016

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Transcript of Introduction to Radiology

Radiography
Primary method for diagnosis
X-rays pass through soft tissue, but are absorbed by dense tissues
The film is lighter where the x-rays are absorbed (e.g., bone, teeth, tumors)
Often used in dentistry, diagnosis of fractures, chest examinations
Con: Produces images of overlapping organs
CT
Person moved through a cylindrical machine
Low-intensity x-rays are emitted from one side and collected on the other side of the body
Produces thin slices which make up a 3-D image
Very sensitive
Pros: Little overlap of organs in thin slices, sharper image
MRI Overview
Obtains structural, functional, chemical, and dynamic information in a single scanning session
Visualizes soft tissues
Types: T1 weighted, T2 weighted, cardiac MRI, MR angiography, DTI, MRS, fMRI
Intro to Radiology
Medical Imaging Techniques
Radiography
Sonography
Computed Tomography (CT)
Magnetic Resonance Imaging (MRI)
fMRI
Positron Emission Tomography (PET)
Single Photon Emission Tomography (SPECT)
Sonography
Second most widely used method
AKA ultrasound
Handheld device
Receives high-frequency ultrasound waves reflected off of internal organs
Pros: Not harmful like x-rays, inexpensive, portable
Con: Sonograms aren't sharp images
Kinesiology 328: Human Anatomy
MRI: How It Works
Patient lays still in a cylinder surrounded by a large magnet
Strong magnetic field aligns protons in the tissues
Radio waves disrupt the natural alignment
When the pulses are stopped, the protons realign and emit radiofrequency absorbed
Emitted energy used to produce image
Cons: bone doesn't show up well, patients can feel clautrophobic in machine
T1 Weighted Scan
Mostly used to delineate anatomy
White matter appears white
Gray matter appears gray
CSF, blood, bone, and air appear black
Pathology-altered areas will have increased water content due to edema
T2 Weighted Scan
Sensitive to alteration of brain tissue
White matter appears black
Gray matter appears gray
CSF appears white
Bone, blood, and air appear black
Pathological tissue appears white due to increased water content
fMRI
Used to visualize physiology
Can map areas involved in specific functions based on oxygen concentration differences in blood flow
Neurons firing action potentials consume oxygen and cause a brief decrease and then increase in local oxygen levels
Other Types of MRI
Cardiac MRI: Images timed to beating of heart
MR Angiography: Images major blood vessels
DTI: White matter pathways reconstructed based on water movement
MRS: Visualizes regional alterations in neurochemistry
PET
Images of regional metabolic functions
Injection of radioactive tracer molecule, usually positron-emitting glucose, followed by immediate imaging
Collisions of positrons and electrons releases gamma rays, showing which tissues are most active
Used to evaluate disorders with brain metabolism disturbances (e.g., neurodegenerative diseases)
SPECT
Injection of radioactive tracers containing single photon emitting substances
Indirect measure of regional brain metabolism
Cons: Low spatial resolution and sensitivity
Pro: Less expensive than PET
Full transcript