Term
| Give the degree of susceptibility for organs to radiation therapy: |
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Definition
Blood-forming organs > reproductive organs > skin > bone and teeth > muscle > nervous system
The tissue that are going to be most affected by radiation therapy are the ones that are actively undergoing cell division. |
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Term
| Modification of DNA bases occurs with _______ ionization, while hydroxyl ions and oxygen based radicals are produced via __________ ionization. |
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Definition
Direct ionization involves the modification of DNA bases.
Indirect ionization involves the production of hydroxyl ions and oxygen-based radicals. |
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Term
| What are the molecular effects of radiation with respect to DNA damage and free radicals? |
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Definition
Produce free radicals (hydroxyl ions, oxygen-based radicals)
Break chemical bonds (modification of DNA bases)
Produce new chemical bonds and cross-linking between macromolecules
Damage molecules that regulate vital cell processes |
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Term
| What are the four "R's" of radiation oncology? |
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Definition
Repar: normal cells respond to radiation with DNA repair, while neoplastic cells have trouble with repair.
Redistribution: Death of cells in susceptible stages and movement of other cells into susceptible stages.
Reoxygenation: Radiation fractions use local oxygen. Allow the affected tissue time for reperfusion.
Repopulation: cells successfully divide and normal tissues and tumor recover. |
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Term
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Definition
| Sum of exposure. Measured in Gray. |
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Term
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Definition
| Fractionation is the amount of radiation delivered per session. |
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Term
| Define "time" as it applies to radiation oncology: |
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Definition
| Time is the spacing of fractions. |
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Term
| What diagnostic tool MUST be done prior to initiation of radiation therapy? |
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Definition
| CT scan--must make a plan and multiple images are recommended. The idea behind forming a plan is that you want to protect normal tissue and focus the beam on the tissue that you want to irradiate. |
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Term
| What are some radiation therapies that can be performed on the brain? |
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Definition
Gamma Knife Surgery
Single Fraction Radiosurgery |
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Term
| What nasal tumors are the most responsive to radiation therapy? |
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Definition
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Term
| 2/3 of nasal cavity tumors are ___________, making them less responsive to radiation therapy and giving a MST of nasal tumors ~1 year. |
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Definition
| Carcinomas. Radiation therapy is basically the best option out of a set of difficult choices. |
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Term
| What is the most responsive oral tumor to radiation therapy? |
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Definition
| Acanthomatous ameloblastoma |
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Term
| Which oral tumor is less responsive to radiation therapy? |
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Definition
Fibrosarcomas
Note: squamous cell carcinomas may be responsive but depends on their position (rostral/caudal) |
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Term
| T/F: pre- and post-surgical radiation is common in therapy of trunk/limb tumors, especially when dealing with invasive tumors or regions that are hard to close surgically. |
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Definition
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Term
| What are the early side-effects of radiation therapy? |
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Definition
Transient demyelination that regenerates with steroids and supportive care.
Mucositis--can be oral or alimentary; usually begins 2 weeks after the start of therapy and often requires a feeding tube
Anusitis
Skin ghanges--hair loss, pigmentation changes, desquamation (dry-no treatment; wet-wound care/prevent excoriation)
Eyes- acute blephartitis/blepharospasm/ conjunctivitis/ulceration/KCS; chronic-vascular changes/retinal atrophy |
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Term
| What are the late side effects of radiation therapy? |
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Definition
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Term
| List the three delivery methods of radiation therapy: |
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Definition
Telotherapy
Bradytherapy
Radioisotope |
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Term
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Definition
| Teletherapy is when the source of radiation is distant from the tumor |
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Term
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Definition
| Bradytherapy is when there is direct application of radioactive material into the tumor--dangerous to clinicians |
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Term
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Definition
| Direct application of radioactive materials onto the tumor using a wand that emits high doses of beta radiation in one application |
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Term
| Pleisotherapy is useful for tumors in what locations? |
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Definition
Conjunctiva
Incomplete surgical margins
Small, cutaneous SCC
Mast Cell Tumors in cats |
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Term
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Definition
| Radioactive element injected IV that accumulates in a desired organ |
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Term
| List some radiation responsive tumors: |
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Definition
Equine sarcoid
Gingival SCC
Acanthomatous ameloblastoma
Plasma cell tumor
Cutaneous MCT
Perianal adenoma
TVT
Lymphoma
Nasal adenocarcinoma
Tonsillar SCC
Oral malignant melanoma
Meningioma
Feline vaccine-associated FSA
Nasal FSA/CSA
Hemangiopericytoma of the extermities
SCC of planum nasale |
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Term
| What are some causes of radiation therapy failure? |
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Definition
Radiation-related toxicity to normal tissues
Histologic tumor confers radioresistance
Larger tumor volume has higher risk of hypoxia
Inadequate dose
Geographic miss |
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Term
| Who discovered the x-ray? |
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Definition
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Term
| What veterinarian described the use of x-rays in the imaging of animals? |
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Definition
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Term
| Beta particles used for radiation therapy are most commonly derived from the decay of what isotopes? |
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Definition
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Term
| What is the most common source of gamma radiation in veterinary therapy? |
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Definition
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Term
| What are the three main types of interactions that occur between gamma rays/x-rays and matter? |
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Definition
Photoelectric effect
Compton effect
Pair production |
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Term
| T/F: tumor cells are more susceptible to host cells to the ionizing effects of radiation therapy. |
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Definition
| True. This is partially due to the fact that neoplastic cells are rapidly dividing, and radiation therapy works best on rapidly dividing cells. |
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Term
| A typical radiation protocal is _____ fractions, over ______ weeks, for a total of ______ Gy. |
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Definition
| 10-20 fractions over 2-4 weeks, for a total of 35-54 Gray |
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Term
| What are the two types of external beam radiation? |
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Definition
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Term
| T/F: one of the major drawbacks to orthovoltage is the intense skin reaction caused by a significant portion of the energy being absorbed within the first few centimeters in the outer tissues. |
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Definition
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Term
| What external beam radiation offers excellent tissue penetration and has Cobalt 60 and Linear Accelerators in its category? |
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Definition
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