radiotherapy

Question 1

what is radiotherapy?

Answer 1

use of ionising radiation to treat cancer. use of LINAC.

Question 2

what is the difference between proton and photon radiotherapy?

Answer 2

proton: covers smaller amount of body, expensive, invasive, radiation beam stops as it enters tissue.

photon: beams attenuate but go all the way through people

Question 3

what is the patient pathway?

Answer 3

stimulation (CT) , registration, contouring, dose planning, quality control checks, treatment, follow up.

Question 4

what happens in the mould room?

Answer 4

immobilisation devices are made (thermoplastic mask, vac bag). and bolus out of wax or vaseline are made to act like tissue

Question 5

what happens in treatment planning?

Answer 5

Combine CT and or MRI scans and plan where radiation beams are going to hit trying to minimise dose to healthy tissue.

Question 6

what QC and QA is done?

Answer 6

• Treatment machine
  
  • Treatment plan
    -Ionisation chamber (used to measure radiation dose)

Question 7

what are 2 radiotherapy modalities for treating a small tumour within the brain and describe an advantage to each technique?

Answer 7

i. Stereotactic radiosurgery: delivers high dose of radiation precisely to the tumour while minimising exposure to healthy brain tissue

ii. Intensity-modulated Radiation therapy: conformal dose distribution. Delivers radiation with varying intensities across multiple beams allowing a more conformal dose distribution to the irregular shape of the tumour

Question 8

What IR(ME)R duty holder role is assumed by a healthcare scientist during the treatment planning process? What are the key responsibilities of this role?

Answer 8

Practitioner: responsible for the treatment plan in line with the protocols. Quality assurance and safety (does the plan deliver the prescribed dose accurately to the target volume while minimising exposure to healthy tissue), collaborate with MDT (oncologists, physicists, dosimetrists), optimisation (consider tumour size, location, surrounding anatomy), documentation.

Question 9

How does the healthcare scientist contribute to safe, accurate delivery of radiotherapy?

Answer 9

i. Treatment planning: design treatment plans that deliver the prescribed dose to the tumor while minimizing radiation exposure to surrounding healthy tissues

ii. QA: responsible for implementing and overseeing quality assurance programs. Perform routine checks and calibration of treatment delivery equipment.

iii. Equipment commissioning and maintenance

iv. Radiation safety
Patient-specific dosimetry: appropriate dose distribution for each individual

Question 10

what are the 5 R’s of fractionation

Answer 10

Radiosensitivity: different tumours have different sensitivities to radiation
re-oxygenation: more cells killed if oxygen present as tumours die and oxygen reaches hypoxic cells.
reassortment: in the cell cycle the mitotic phase is the most radiosensitive
recovery: cells need time to recover from sub-lethal damage
repopulation: prolonging treatment allows surviving cells to proliferate

Question 11

what is fractionation?

Answer 11

alpha to beta ratio