Biomedical Instruments (EXAM 2) Flashcards
What are 3 examples of Radiation Therapy
- X-Ray
- Gamma Knife
- Hadron Therapies
What is the Goal of Radiation Therapy
- Use radiation to KILL cancer tumor tissues while minimizing damage to healthy tissue
What does dose mean in Radiation Therapy? What does it generate?
- Measure of energy deposited by the radiation in the body
- This energy generates ionization of cell molecules that ultimately leads to cell death
X-rays deposit more dosage at which penetration depth? What about ions such as protons and carbon?
- More energy near the body entrance for X-rays
- Protons and Carbon concentrate more dose at the tumor (more penetration)
The depth of the energy deposition peak (Bragg peak) can be efficiently tuned by changing what?
Changing the ION ENERGY!
Killing Cancer cells by these radiation therapies induce what?
Induce SIGNIFICANT DNA DAMAGE to prevent cell replication
Double strand break of the DNA is required since cells are very efficient at repairing single strand breaks by two mechanisms. Name them!
- Direct Route
- Ionization of DNA directly from the radiation - Indirect Route
- Radiation interacts with water (H2O) to create free radicals HO- which then induce DNA damage
Explain Stereotactic Radiosurgery
- Called “Stereotaxy”
- Non-invasive form of “surgery”
- Results compare to conventional surgery
- Highly precise delivery of radiation (accurate to 1-2 mm of target)
What does Stereotactic Radiosurgery rely on?
- 3D imaging (such as CT scan)
- Highly focused gamma ray beams
- Image-guided radiation therapy
Names Treatment applications of Stereotactic Radiosurgery
- Brain tumors
- Arteriovenous malformations (AVMs) = Tangling of expanded blood vessels limiting blood flow
- Trigeminal neuralgia
- Tremors
- Epilepsy
Case SCENARIO!!!!
A patient has headaches and nausea, diagnosis involves an MRI where we diagnosed a Benign Brain Tumor
What is the treatment of choice?
- Chemo/Immuno therapy?
- Invasive Brain Surgery?
- Non-invasive radiotherapy?
- Non-invasive stereotactic radiosurgery?
- Chemo/Immuno therapy? No, Blood brain barrier
- Invasive Brain Surgery? No, High risk
- Non-invasive radiotherapy? No, too non-specific
- Non-invasive stereotactic radiosurgery? YES! Localization of specific area for radiation
What is Stereotactic Radiosurgery?
Explain 3D Stereotactic Localization
Describe Tomographic Techniques
- PET (CT) and MRI
- Good for tumor pathologies
- Use multiple layers to get 3D image
Describe X-Ray based Techniques
- X-ray and Digital Subtracted Angiography
- Good for vascular imaging (for treatment of vascular malformations)
- Use pins and depth perception methods to get 3D localization
Describe Radiosurgery
How is Radiosurgery therapeutic?
How long does it take for a benign tumor to disappear?
What about Metastatic (Cancerous) tumors (with a much faster growth rate)?
- Benign = Up to 2 years
- Metastatic = Only months
What are some side effects of Radiosurgery?
- Swelling: Cells lose ability to retain fluid, edema may occur
- Necrosis: Dead tumor cells may cause complications (inflammation, fibrosis)
- Psychological side effects: Loss of memory and decreased cognitive abilities
- Radiation-induces tumor/cancer: Radiation-induced mutations may result in a new tumor or cancer
What are the applications of Radiosurgery?
- Mostly used for CNS, head and neck surgery
What are the different types of radiation plus their sources
- High energy X-Ray: from Linear accelerator systems
- Gamma Radiation: From Cobalt-60 source
- Proton: From particle beam or cyclotron
Explain Gamma Knife
- From Cobalt-60 source
- Uses multiple beams to treat tissue volume
- Multiple targets can be easily treated in one session
Explain LINAC (Linear Accelerator-based) systems
Explain CyberKnife
What is the process of Gamma Knife
What are the ADVANTAGES of Gamma Knife
What are the DISADVANTAGES of Gamma Knife
Explain LINAC-based systems in terms of accuracy and efficiency
Explain CyberKnife
Recognize the Radiosurgery history
Compare Gamma Knife to Radiation Therapy
What are the 4 Forces of Nature
- Strong Nuclear Force
- Weak Nuclear Force
- Electromagnetic Force
- Gravitational Force
What are Hadrons?
- Subatomic particles which experience the STRONG NUCLEAR FORCE
- They are composed of fundamental particles called quarks, anti-quarks, and gluons
- Hadrons are divided into 2 categories based on type of quarks they are: Baryons and Mesons
Define Baryons
- One of the categories of quarks
- STABLE!
- Proton and Neutron
Define Mesons
- One of the categories of quarks
- NOT STABLE!
- Kaon, Antiproton, Antineutron
Higgs boson particle is known as the
” God particle”
Why are Hadrons useful in Cancer Therapy?
- Penetration depth can be well defined and adjustable
- Most energy deposited at end-of0range
- No dose beyond target
- Leak to normal tissue minimized
Good tumor kill
Hadrons can reach a depth of what?
In slideshow, it went as deep as 25 cm which is a lot more than X-rays for instance.
Compare Fission to Fusion
- Fission: Break one molecule into two. Easy to get started. Not as safe.
- Fusion: Combine 2 into one. Tremendous amount of energy required to initiate reaction. Safer to use.
Explain the properties of Neutrons
- Mass = 1.67 e^-27 kg
- No Charge
- Indirectly Ionizing Radiation
- Neutron Half-life = 10 minutes
All neutrons are initially what?
All neutrons are initially FAST Neurons which lose kinetic energy through interactions with their environment until they become thermal neutrons which are captured by nuclei in matter
Explain the properties of Protons
- Mass: 1.67 e^-27 kg
- Positive Charge
- Directly Ionizing Radiation
- Proton Half-life = 10^35 years
Understand Proton vs Photon Depth Dose in Water
- Look at slides
- Increasing energy 130MeV –> 190 MeV increase depth of penetration.
- Higher energy = more depth
Defend why Protons are of good use
- Protons have GOOD DOSE distribution
- Low entry dose
- Most of the energy deposited at a SPECIFIC DEPTH
- No dose beyond specific range (minimizing damage to surroundings)
Make sure you can compare Protons and X-Ray
- Protons: More directly radiated to a specific range
- x-Ray: Target not just the specific range, but surrounding cells as well. X-Ray is not as good in targeting as protons.
Custom components involved in proton therapies
Range compensator:
- Made of GLASS-like which conforms dose distribution to the DISTAL shape of the target
- Made from water equivalent material
Beam Aperture:
- Made of BRASS and it Conforms dose distribution LATERALLY
What are Heavy Ions?
-Ionized atoms which are usually heavier than Carbon
- Refers to atoms that are generally completely ionized i.e. they are bare atomic nuclei
- Ex.) C, Si, W, Au, Pb, U
- The nuclei can be directed to a fixed target, or can be split into two beams moving in opposite directions that are brought into collision at a well-defined spot
Collision of heavy ions can produce what?
HADRONS!!!
Explain Fusion Reaction
- More energy produced than Fission Reaction
- No harmful radiation produced
E = mc^2 Special Theory of Relativity
What is the correct/full equation?
Correct equation is:
E= mc^2/ sqrt(1-V^2/C^2)
What are the 3 Laws of Robots by Isaac Asimov
- A robot may NOT injure a human being or, through inaction, allow a human being to come to harm
- A robot MUST obey the orders given it by human beings, except where such orders would conflict with the First Law
- A robot MUST protect its own existence as long as such protection does NOT conflict with the First or second Law
Briefly describe the PUMA 560 CT guided brain biopsy device
- A robot with improved absolute positioning accuracy for CT-guided stereotactic brain surgery
- Collect biopsies of brain and neck region
Explain the Da Vinci Surgical System
- 1st robotic system approved by the FDA for general laparoscopic surgery
- The 1cm diameter surgical arms represent a significant advancement
- Extend the benefits of minimally invasive surgery to patients
- 3D magnification screen allows the surgeon to view the operative area with the clarity of high resolution
Pros and Cons of Robotic technology for surgery for Patients
Pros:
- Fast recovery
- Less pain
- Less scarring
- Less loss of blood
- Less need for blood transfusion
- Smaller incision
Cons:
- Inexperienced surgeon
- Power/Network dependent
- Expensive
Pros and Cons of Robotic technology for surgery for Surgeons
Pros:
- Less liability for the surgeon
- Surgeons are less fatigued
- More comfortable during surgery
- Better visibility during surgery
- Da Vinci is dependent on surgeons
Cons:
- Cost about $2.5 million
- Steep learning curve
- Not easy to operate
