Clinical Correlations Flashcards
(38 cards)
What are the 6 main cancer imaging modalities?
- X-ray
- CT
- Ultrasound
- MRI
- Gamma Camera and SPECT
- PET
What is the difference between structural imaging and functional imaging?
What are examples of Structual and Functional Imaging modalities.
Structural imaging reveals the physical structure of a object (tumor mass, calcium deposit, bullet, etc.). It can not determine its function.
- X-rays, CT, MRI, Ultrasound
Functional imaging reveals physiological activites from an image (hyperglucose metabolism, chemical composition, blood flow, absorptoin, etc.)
- PET, Gamma Camera, SPECT, MRI*
What is the difference between transmission and emission imaging?
What are examples of transmission and emission imaging modalities?
Transmission imaging - energy originates OUTSIDE the body and is directly THROUGH the body to produce an image
- X-Ray, CT, Ultrasound
Emission Imaging - energy originates INSIDE the body and emanates out of the body.
- PET, SPECT, Gamma Camera
What is a spiculated mass?
A lump of tissue with spikes or points on the surface. It is suggestive but not diagnostic of malignancy, i.e. cancer.
What are the pros and cons of X-ray imagin?
- Pros
- Good screening tool
- Cheap
- Fast, Easy on patient
- minimal radiation dose
- Cons
- 2D images only
- not as detailed as a CT/MRI
- No functional informatoin
- non-specific findings
What are the pros and cons of Ultrasound imaging?
- Pros
- Cheap
- NO radiation
- Real-time images (needle guided biopsies)
- Portable (good for breast and prostate cancer diagnosis)
- Cons
- User dependent
- Poor image resolution
- Little/no functional info
What are the pros and cons of CT imaging?
- Pros
- 3D images
- Better resolution than X-ray/Ultrasound
- Can use oral and or IV contrast to evaluate bowel lumen or vascularity.
- Fast
- Readily available
- Cons
- No functional info
- nonspecific findings (ie - lymph nodes)
- IV contrast is renotoxic
- Radiation exposure
What does SPECT stand for?
Single Photon Emission Computed Tomopgraphy - (like a CT image for Gamma camera) - its 3D.
What does PET stand for?
Positron Emission Tomography- detects engery given off by positrons. Allows for quantification.
What is the most common positron emitter used?
What is it usually attached to?
What is that molecule called?
What does it measure?
Why do cancer cells “light up” when imaged with this material.
18F
Glucose
18F-Fluorodeoxyglucose (FDG)
Measures glucose metabolism
Cancer cells use a lot of glucose because they upregulate GLUT1 receptors.
What are pros and cons of nuclear imaging?
-
Pros
- Functional Information
- Quantitative
- Assessment of treatment
- Can also be therapeutic
-
Cons
- Expensive
- Nonspecific
- Slow acquisition times
- Radiation Exposure
Who discovered x-rays?
Roentgen (playing with a Crookes tube)– blocked rays w/ lead plate and got a picture of his hand
What are x-rays and where do they fall on the electromagnetic spectrum?
X-rays are ionizing radiation with a shorter wavelength than UV light (i.e. on the right side of the electromagnetic spectrum)
What is ionizing radiation?
Ionizing radiation is composed of particles w/ enough energy to liberate an electron from an atom or molecule –> can alter chemical bonds and produce ions
How is a radiographic image made?
A tungsten wire creates a flow of electrons –> electrons are knocked off of the tungsten wire and hit a metal target –> creates x-ray –> x-rays are collected in a film on the other side of the patient
What is attenuation and how does it contribute to the different colors on an x-ray?
Attenuation is blockage of x-rays
Tissues that are more dense attenuate (block) more x-rays, so fewer x-rays reach the film on other side of patient to expose it and turn it black
What is a CT scan?
A CT scan is a rotating x-ray beam of defined thickness that irradiates patient from numerous projections
What is the houndsfield unit for water? What color is it on x-ray?
HU for water = 0
It is dark gray on x-ray
What is the houndsfield unit for air? What color is it on x-ray?
HU for air = -1000
It is very black on x-ray
What is the houndsfield unit for bone? What color is it on x-ray?
HU for bone = +1000
It is very white on x-ray
What are milliamperes (mA) and what are the advantages/disadvantages of increasing it in x-ray?
Milliamperes are the number of photons emitted from an x-ray beam
Advantage of increasing mA: decreases quantum noise, increases contrast resolution
Disadvantage of increasing mA: higher dose of radiation to patient, higher heat load on tube anode
What are kilivolts (kV) and what are the advantages/disadvantages of increasing them in x-ray?
Kilovolt (kV) is the energy level of the x-ray beam (higher energy beam are used for larger patients to acheive a greater penetration)
Advantages of increasing kV: decrease in quantum noise, greater penetration
Disadvantages of increasing kV: higher dose to patient, may reduce soft tissue density differences (lose subtle things in soft tissues)
Why does a stroke show up dark on a CT scan?
Na/K pump is affected by stroke b/c of lack of oxygen –> water follows ion gradient –> density in brain decreases because water pools –> HU for water = 0, so the affected area shows up dark gray
Where does the majority of radiation exposure occur to people?
Medical sources
