Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

McGill Note- Head and Neck > RADIATION > Flashcards

RADIATION Flashcards

1
Q

Q: Name two types of ionizing radiation; which one is used in H&N Ca [?]

A
  • Photons (Xrays / Gamma rays) → H&N Use

- Particle Radiation (electrons, protons, neutrons, etc)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Q: Characteristics of Photon Radiation; which one used in H&N [?]

A
  • Low (5MeV; H&N) or high (20MeV) energy
  • Skin-sparing properties
  • Depth-dose properties (Penetration)
  • Isodose distribution (Beam Uniformity)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Q: Characteristics of Electron Beam XRT [?]

A
  • Good for Superficial lesions, deep tissue sparing.

- Range of Penetration (cm) = MeV/3.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Q: Three Advantages of Brachytherapy [?]

A
  • Better dose Localization
  • Continuous Fractionation.
  • Decreased dose to Adjacent normal tissue.
  • Radioactive source placed in proximity to lesion.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Q: Brachytherapy source placement (3 types) [?]

A

1- Interstitial: radiation source directly on target tissue (i.e. prostate or breast).
2- Intracavitary: vagina, cervix.
3- Intraluminal: trachea, esophagus.
4- Surface mold: skin.
** #2-4 → “Contact brachytherapy” = radiation source in adjacent target tissue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Q: Brachytherapy time frames of use [?]

A
  • Temporary – long-lived isotopes used (RIC = Radium, Iridium, Cesium). -Permanent – short-lived isotopes used (PIG = Palladium, Iodine, Gold).
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Q: (TK) IMRT: What is it? Disadvantages [?]

A
  • Intensity-modulated RT.
  • Use of CT & Software to use multiple beams of varying intensity from different directions for accurate delivery based on tumour size & location; conformal therapy (dose distribution around tumour)
    PROS:
    (i)Localized radiation, (ii) high dose radiation to tumour site, (iii)sparing of normal structures (reduced toxicity).

Disadvantages:
(i) expensive, (ii) time-consuming, (iii) special immobilization required, (iv)steep
radiation falloff (limit of rads depends on tumour mapping marks by physician), (v)steep learning curve

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Q: Radiotherapy Pearls [?]

A
  • Cell Death = Inability to Proliferate; both DNA strands must be knocked out.
  • Log cell kill = particular radiation Dose will kill the same Proportion of cells.
  • Therapeutic Window = Dose Response curves between Tumor cell & Tissue damage; relative positions of curves determine safety of tumor control.
  • Shrinking Field technique; now replaced by concomitant boost?
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Q: Radiotherapy: Mechanisms of cell injury(2) & percentages of each [?]

A
  • Direct injury – Electron from x-ray absorption causes DNA Damage (1/3)
  • Indirect injury – Electron from x-ray creates an Oxygen Free Radical which then damages the DNA
    (2/3)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Q: What are the 4 R’s of radiotherapy injury mechanisms [?]

A
  • Repair – Sublethal injury will be repaired by the cell if it takes no further hits, increased fractionation = increased repair (by normal tissue, since cancer cells are worse at repair).
  • Reoxygenation – Presence of oxygen increases the effects of Ionizing Radiation, radiosensitivity stays the same down to 20mmHg oxygen, below this sensitivity decreases. With fractionation hypoxic tumours reoxygenate and become more RT-sensitive.
  • Redistribution – Max. radioresistance = Late S phase; max. radiosensitivity = Early M phase (late G2 also very radiosensitive); fractionation allows increased radiosensitivity, as surviving cells redistribute themselves to other phases in cycle).
  • Repopulation – Tumors accelerate repopulation after cell reduction from surgery or radiation (this is one disadvantage of hyperfractionation, addressed by accelerated Fx’n).
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Q: (DO): What is radiosensitivity [?]

What are the key components that make cells more sensitive [?]

A

Radiosensitiviy: the ability of radiation to lead to cell death via DNA damage without
adequate DNA repair.

Components:

  • High cell division rate: rapidly dividing cell = increased susceptibility to DNA damage (M phase = radiosensitive vs. S phase = radioresistant)
  • Low capacity for DNA repair
  • High oxygen content
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Q: (DO): List examples of radiosensitive (2) and radioresistant tumours [?]

A
  • Radiosensitive: lymphoma, oral mucosa ca (SCC)

- Radioresistant: sarcomas, melanomas

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Q: Definition of a Gray and Rad [?]

A
  • Gray (Gy) = Joule/kg =The absorption of one joule of radiation energy by one kilogram of tissue
  • Rad = Radiation absorbed dose; 100 rad = 1 Gy
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Q: Describe Standard [?]

A

Standard: single dose/fraction (1.8-2.0Gy) of radiation per day, MON-FRI. (i.e 2Gy OD 5d/wk for 7 weeks (35F) = 70Gy)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Q: Describe Hyperfractionation [?]

A

Multiple fractions per day, lower doses per fraction, increased total dosing, increased duration of treatment (i.e. 1.2Gy BID 5d/wk for 7wks for 68F = 81.6Gy) Improved radiosensitivity of tumour cells via “Repair, reoxygenate, redistribute”

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Q: Describe Accelerated fractionation [?]

A

Accelerated: increases amount of dose per fraction, same total dosing, decreased duration of treatment (i.e 1.6Gy/fractions/BID 5d/wk 67.2Gy/42 fractions/6wks).
- Allows decreased time for tumour “Repopulation”

  • Intense: 1.5Gy TID 7d/wk x 36F = 54Gy
  • Split: 1.6Gy BID 5d/wk x42F (split with 2 week gap in between) = 67.2Gy
  • Concomittant Boost: 1.8Gy OD 5d/wk (30F) +1.5Gy dose BID on last 12F = 72Gy
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Q: Describe Standard, Hyperfractionation, Accelerated fractionation [?]

A
18
Q

Q: Adv / DisAdv of Hyperfractionation and Accelerated Fractionation [?]

A
19
Q

Q Discuss “BOOST” radiation [?]

A
  • Form of accelerated radiation
  • Increase the number of fractions per day at a given time of radiation treatment (usually the end)
  • Indicated for locally advanced disease → better LRC not OS
  • Allows more rads to tumour due to “shrinking field”
20
Q

Q: Discuss “SPLIT-COURSE” radiation [?]

A
  • Form of accelerated radiation
  • Gap midway between radiation course to allow healing of surrounding tissue
  • Decide during the gap whether or not to continue with palliative or curative intent
21
Q

Q: Dose limiting factors for Intensity and Total dose [?]

A
  • Intensity (Increased # of daily fractions OR reduced duration of overall treatment → Acute toxicity = Mucositis → accelerated rads and hyperfractionated rads
  • Total dose – Late toxicity = Soft tissue Fibrosis → hyperfractionated rads
22
Q

Q: Time required post-XRT to call biopsy reliable [?]

A
  • 3 months .
  • Cell lysis occurs at mitosis, 4-5 divisions occur before Lysis .
  • Lethally injured cells and Surviving cells are morphologically identical .
23
Q

Q: (DO): Options for administration of radiations [?]

A
  1. Preoperative (neoadjuvant)
  2. Postoperative (adjuvant)
  3. Concurrent (with chemotherapy)
  4. Palliative (unresectable disease; stage IVb)
24
Q

Q: PROS/CONS of Preoperative Radiotherapy for SCC [?]

A
25
Q

Q: PROS/CONs of Postoperative Radiation therapy for SCC [?]

A
26
Q

Q: Best Postoperative Time interval for Adjuvant XRT [?]

A
  • Within 6 weeks
27
Q

Q: General Indications for Post-operative Radiotherapy [?]

A
  • T3 or T4 lesion
  • Perineural invasion
  • Lymphovascular invasion
  • Extracapsular spread
  • > N1
  • Positive resection margins (considered gross residual disease, >106 cells)
28
Q

Q: Distance of tumor to resection Margin that is considered Close [?]

A
  • ≤5 mm .

- Found to have Same Prognostic significance for Recurrence as Positive Margins .

29
Q

Q: Six beneficial mechanisms of Chemoradiotherapy [?]

A
  • Can act on Different subsets of tumor cells
  • Recruit cells from G0 into radiation sensitive phases
  • Chemo Inhibits Repair of sublethal radiation injury
  • Tumor shrinkage decreases Interstitial pressure, thus increases drug and O2 delivery - Prevents Radiation Resistance
  • Cell-cycle Synchronization increases the effectiveness of both therapies
30
Q

Q: Indications for postoperative Chemo with XRT [?]

A
  • ECS
  • Positive margins
    Q: Toxic CNS doses [?]
  • Somnolence syndrome
  • Myelopathy – 50 Gy in 25 fractions - Transverse Myelitis – 50 Gy
  • Brain Necrosis – 70Gy
31
Q

Q: Nine Late Complications of Radiotherapy for NPC in 6 different sites [?]

A

SKIN

  • Skin necrosis
  • Second Primary

ORAL/MANDIBLE

  • Osteoradionecrosis
  • Xerostomia (35Gy)

EYES
- Cataracts – 6Gy

EAR

  • Middle ear effusion secondary to ET dysfunction
  • ?Osteromyelitis of temporal bone

NASOPHARYNX
- Nasopharyngeal stenosis

CNS

  • Transverse myelitis (50 Gy)
  • Somnolence syndrome,
  • Brain necrosis (65 Gy)
32
Q

Q: Seven Complications of Radiotherapy for Neck disease [?]

A
  • Xerostomia – 5-6 Gy in 5-6 weeks?
  • Mucositis
  • Dental caries
  • ORN – In up to 5% of patients, rare <60 Gy, increased if chemo-XRT
  • Soft tissue fibrosis
  • Hypothyroidism – 1% clinically overt, 10% occult after 50 Gy in 4 weeks - Immunosuppresion
  • Spinal cord Necrosis – Limit to 45-50 Gy in 5 weeks
  • 2nd primary
33
Q

Q: (TK) How is Radiation Toxicity graded [?]

A
  • RTOG Scale: Separate Acute & Late morbidity scales for each body/tissue site
  • Graded 1-5 based on severity (0= no symptoms, 5 = death directly related to XRT)
  • i.e. mucous membrane (acute): 1 = injection / mild pain; 4 = ulceration / necrosis
34
Q

Q: Osteoradionecrosis, 4 treatment modalities [?]

A
  • CONSERVATIVE/MEDICAL
  • Topical Care
  • Biopsy + culture of site
  • IV antibiotics
  • HBO
  • SURGICAL
  • Sequestration
  • Mandibulectomy with reconstruction (plates/soft tissue/ osseocutaneous free flap)
35
Q

Q: (LK) What are the different grades of ORN [?]

A
  • Grade I = exposed alveolar bone + HBO responsive (most common)
  • Grade II = exposed alveolar bone + HBO unresponsive → sequestrectomy/saucerization
  • Grade III =
    (i) full-thickness bone involvement,
    (ii) resorption of inferior mandibular border,
    (iii) orocutaneous fistula, and/or
    (iv) pathologic fracture
36
Q

Q: What is the Marx protocol: [?]

A
37
Q

Q: Three typical osseous findings of mandibular ORN on CT scans [?]

A

“LORDS of the Cort”

  • Loss of trabeculation
  • Osseous fragmentation - Radiolucency
  • Demineralization
  • Sequestration
  • Cortical thinning
38
Q

Q: Four Intraorbital Complications of Radiotherapy, Maximum Doses where applicable [?]

A
  • Cataracts – as little as 6 Gy
  • Lacrimal gland injury – ~35 Gy in 3.5 weeks - Radiation Retinopathy – 50 Gy
  • Optic Nerve injury – 50 Gy
39
Q

Q: What Spinal Cord Complication can occur Post-Radiotherapy? Sign/Dose of radiation is associated [?]

A
  • Radiation Myelopathy
  • L’Hermitte’s Sign – Electric shock sensations triggered by Flexing the Cervical Spine
  • Transverse myelitis
  • Spinal cord necrosis
  • Doses of 50 Gy in 5-6 weeks
40
Q

Q: Criteria (and name of) for diagnosis of Post-Radiation Sarcoma (PRS) [?]

A

Cahan’s criteria

  • Different Histology
  • PRS is located within the field of irradiation
  • Patients with cancer syndromes such as Li-Fraumeni (p53 mutation) and Rothmund-Thomson are excluded
  • Must be biopsy-proven
  • Latent period (period between initiation of radiotherapy and histologic diagnosis of second neoplasm) is >4yrs
41
Q

Q: Dose of XRT for Micropscopic disease and N0 neck [?]

See NCCN guidelines pg. 102

A
  • Microscopic disease = 65 Gy

- N0 neck = 55 Gy

42
Q

Q: When and for which levels to do an Elective Neck Dissection (or Irradiate) according to Primary
Tumors [?]

A

McGill Note- Head and Neck (2 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions