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Foundations 2 - Week 6 > Clinical Correlations > Flashcards

Clinical Correlations Flashcards

1
Q

What are the 6 main cancer imaging modalities?

A
  1. X-ray
  2. CT
  3. Ultrasound
  4. MRI
  5. Gamma Camera and SPECT
  6. PET
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2
Q

What is the difference between structural imaging and functional imaging?

What are examples of Structual and Functional Imaging modalities.

A

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*
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3
Q

What is the difference between transmission and emission imaging?

What are examples of transmission and emission imaging modalities?

A

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
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4
Q

What is a spiculated mass?

A

A lump of tissue with spikes or points on the surface. It is suggestive but not diagnostic of malignancy, i.e. cancer.

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5
Q

What are the pros and cons of X-ray imagin?

A
  • 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
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6
Q

What are the pros and cons of Ultrasound imaging?

A
  • 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
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7
Q

What are the pros and cons of CT imaging?

A
  • 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
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8
Q

What does SPECT stand for?

A

Single Photon Emission Computed Tomopgraphy - (like a CT image for Gamma camera) - its 3D.

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9
Q

What does PET stand for?

A

Positron Emission Tomography- detects engery given off by positrons. Allows for quantification.

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10
Q

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.

A

18F

Glucose

18F-Fluorodeoxyglucose (FDG)

Measures glucose metabolism

Cancer cells use a lot of glucose because they upregulate GLUT1 receptors.

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11
Q

What are pros and cons of nuclear imaging?

A
  • Pros
    • Functional Information
    • Quantitative
    • Assessment of treatment
    • Can also be therapeutic
  • Cons
    • Expensive
    • Nonspecific
    • Slow acquisition times
    • Radiation Exposure
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12
Q

Who discovered x-rays?

A

Roentgen (playing with a Crookes tube)– blocked rays w/ lead plate and got a picture of his hand

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13
Q

What are x-rays and where do they fall on the electromagnetic spectrum?

A

X-rays are ionizing radiation with a shorter wavelength than UV light (i.e. on the right side of the electromagnetic spectrum)

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14
Q

What is ionizing radiation?

A

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

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15
Q

How is a radiographic image made?

A

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

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16
Q

What is attenuation and how does it contribute to the different colors on an x-ray?

A

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

17
Q

What is a CT scan?

A

A CT scan is a rotating x-ray beam of defined thickness that irradiates patient from numerous projections

18
Q

What is the houndsfield unit for water? What color is it on x-ray?

A

HU for water = 0

It is dark gray on x-ray

19
Q

What is the houndsfield unit for air? What color is it on x-ray?

A

HU for air = -1000

It is very black on x-ray

20
Q

What is the houndsfield unit for bone? What color is it on x-ray?

A

HU for bone = +1000

It is very white on x-ray

21
Q

What are milliamperes (mA) and what are the advantages/disadvantages of increasing it in x-ray?

A

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

22
Q

What are kilivolts (kV) and what are the advantages/disadvantages of increasing them in x-ray?

A

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)

23
Q

Why does a stroke show up dark on a CT scan?

A

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

24
Q

Where does the majority of radiation exposure occur to people?

A

Medical sources

25
Q

What is the risk of being exposed to lots of ionizing radiation?

A

CANCER

26
Q

What is the difference between x-rays and gamma rays?

A

X rays are man made, gamma rays are released from decay of radioactive material

27
Q

How do clinicians decide what energy photons (or electrons) to use?

A

Based on the depth of tissues they’re trying to treat (higher energy for deeper tissues)

28
Q

How does ionizing radiation cause double-stranded DNA breaks?

A

Ionized particles create free electrons –> electrons interact w/ water –> release hydroxyl radical (OH-) –> radical damages tissues –> causes single-stranded and double-stranded DNA breaks (but single-stranded breaks are not that hard to repair)

29
Q

How do double-stranded DNA breaks cause problems in the body?

A

One DNA repair pathway involves non-homologous end joining, which is a LOW fidelity repair mechanism

Chromosomes are joined at the wrong end, which can cause 2 centromeres in 1 chromsome or a ring pattern, which are not compatible with dividing cells

Cell becomes locked in “mitotic catastrophe”

30
Q

Different cancer cell types are sensitive to different levels of radiation– what 4 factors determines sensitivity to radiation?

A
  1. Unknown genetic factor of tumors
  2. Oxygen levels (hypoxic tumors are less sensitive to radiation than normoxic tumors)
  3. Cell cycle distribution (cells in G2 and M are more sensitive to radiation)
  4. Repair of sublethal radiation damage
31
Q

What are the 4 goals of radiation biology (4 R’s)?

A
  1. Repair of cellular damage
  2. Reoxygenation of tumor
  3. Redistribution of cells within cell cycle
  4. Repopulation of cells (but this is counterproductive)
32
Q

What are the 2 ways in which radiation therapy is used?

A
  1. Cure cancer (destroy tumors that haven’t metastasized, reduce risk that cancer will return after surgery or chemo)
  2. Reduce symptoms (palliative care, shrink tumors to improve quality of life and alleviate pain)
33
Q

What is brachytherapy?

A

Brachy means “close,” the radioactive source is in direct contact with the tumor (eg. Interstitial implants, intracavitary implants, or surface molds)

Common sites: prostate, cervix, endometrium

Ex.: implant radioactive seeds into prostate gland

34
Q

What is intra-operative radiation therapy?

A

Intra-operative radiation therapy is used to treat margins at the time of surgery (with a machine or by wiring radioactive catheters through surgical opening)

35
Q

What is total body irradiation?

A

TBI wipes out patient’s bone marrow so that donor marrow can be implanted

36
Q

What is sterotactic radiosurgery (Gamma knife)?

A

Gamma knife is a surgery-like system that delivers very high dose radiation to very pinpointed area in brain to ablate that tissue

Uses radioactive cobalt at core and a bowl-shaped head covering w/ small apertures that all converge at the same spot

37
Q

What is sterotactic body radiation therapy?

A

SBRT is ike gamma knife, but is used for other parts of the body, like lung, liver, vertebral bodies

Patient is immobilized with special “bean bags” so that they are in the exact same orientation every time, radiation comes in from many different angles

Machine moves w/ breathing, follows tumor as it moves with diaphragm

38
Q

What is selective internal radiation therapy?

A

SIRT treats liver tumors by accessing hepatic artery

Liver has dual blood supply from hepatic artery and portal vein (liver tumors take most of their blood from hepatic artery, while healthy cells take most of their blood from portal vein)

VERY SMALL radioactive glass beads are released into hepatic artery, lodge in capillaries, deliver radiation to liver tumors

Foundations 2 - Week 6 (3 decks)

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