TBI

Question 1

what is TBI used for

Answer 1

acute/chronic leukaemia
relapsed lymphoma
non malignant but life threatening: anaplastic anaemia
advanced disseminated, resistant disease: neuroblastoma (aggressive solid tumour of childhood)

Question 2

what is the aim of TBI

Answer 2

kill all malignant cells
suppress immune system minimise GvHD

Question 3

what is the target volume

Answer 3

all immune system cells + haem tissue

Question 4

what is the main dose limiting structure

Answer 4

lung V20 30%

Question 5

why is TBI good

Answer 5

it eradicates all malignant disease in the BM, chemo doesn’t fully deplete the BM, BBB prevents this

Question 6

what is the conditioning regime

Answer 6

chemo + TBI

Question 7

what is done after chemo

Answer 7

an allogenic SCT

Question 8

what type of dose is it

Answer 8

homogenous and independent of the blood supply

Question 9

what is TBI important for

Answer 9

the conditioning regime prior to the SC for haem malignancies i.e acute leukaemia and lymphoma

Question 10

what does TBI accomodate

Answer 10

complete engraftment through BM depletion if not done, they are likely to reject the transplant. It immunosuppresses the pt to prevent rejection of the transplant/ donor bone marrow

Question 11

what sites can TBI reach that chemo cant

Answer 11

scar tissue, skin surface, sanctuary sites

Question 12

what is needed to treat the whole body

Answer 12

complex modality which delivers a uniform dose (+/-10%) of radiation to the entire body - heterogeneous

Question 13

referral for TBI

Answer 13

BMT following MDT + relevant investigations
counselled in clinic [part of obtaining consent]

Question 14

suitability for TBI

Answer 14

cardiovascular fitness + dose to organs
women under 36 should be counselled regarding their increased risk of breast cancer, should be referred to high risk breast screening programme

Question 15

consent for TBI

Answer 15

RCR RT form
16+ and lack capacity should fill an all wales consent form 4
form should be kept with RT trt prescription sheet
RT is also authorised on WCP
request form by practitioner

Question 16

clinical responsibility of TBI

Answer 16

review pt and approve for TBI
explain the procedure
obtain informed consent
pacemaker and ICD
prescribe to pt midline @ level of axillae
authorised eIRMER trt
ensure optimal medical management of pt and that each fraction is given in a timely manner

Question 17

bookings for TBI

Answer 17

2 slots per month
blocks out trt machine
pt becomes an inpatient, remain in an isolation room until their last trt

Question 18

what is the pt prep prior to TBI

Answer 18

consent: awareness on toxicities and risks
ward visit
visit trt unit and staff
key radiographer: explains procedure, answers qu and addresses concerns

Question 19

what are the radiographer responsibilities

Answer 19

team liases with the consultant and medical physics and chemo ward
team ensures TBI is carried out
act within limits of their knowledge, skills and experience
most senior member is responsible in checking preg status

Question 20

what are the medical physics responsibilities

Answer 20

ensuring dosimeters are prepped for each fraction
specifiying MU, brass compensators and measurement sites for each fraction
measurement + calc of pt dose, recorded on eIRMER
calc is independently checked

Question 21

what is the TBI technique

Answer 21

lat POP @ extended FSD
4.5m to midline
12Gy in 6 fractions, 2 a day with a 6 hour gap
10MV

Question 22

what angle is the gantry on

Answer 22

86 not fully lateral or 274

Question 23

what is the coll head on

Answer 23

45 degrees to give a diamond shape

Question 24

what is the field size

Answer 24

38x38 = varian
40x40 = elekta

Question 25

if the couch was close to the wall what would that cause

Answer 25

an increase in scatter

Question 26

what are the accessorises

Answer 26

acrylic/perspex screen [act as bolus: max dose to skin surface]

Question 27

where is the trolley positioned

Answer 27

in line with the couch lasers, attached to the TBI bed with the 4.2m black line marked on the floor

Question 28

what is the pt position

Answer 28

supine: head on curved sponge arms by side: hand clasped, shielding bottom part of lung head needs to be straight pt squashed, knees bent fairly free set up all positions are noted so can be reproduced

Question 29

dosimetry

Answer 29

probes need to be positioned directly opposite each other to give an accurate reading brass is a compensator, sheets are used with a set thickness

Question 30

what are the standard measurements

Answer 30

shoulder: 40cm hip: 30cm feet: 10cm

Question 31

what happens if the measurements are wrong

Answer 31

cause lead to radiation pneumonitis

Question 32

low dose TBI

Answer 32

single exposure part of the conditioning regime split into two parts to allow medical physics time to calculate the dose, MU left and changes to brass thickness

Question 33

how long dose a single exposure take

Answer 33

4 hours if a third calc is needed it will take another hour pt advised to go to the toilet during the second calculation, pt will then need to be re-set up and diodes replaced

Question 34

what are the low exposure ref points

Answer 34

2Gy

Question 35

how much is the first part

Answer 35

40%

Question 36

how many diodes at each position

Answer 36

at least one

Question 37

what are the low dose fields

Answer 37

rt lat x3 lt lat x3

Question 38

what is the dose for lymphomas

Answer 38

as radiosensitive 2Gy single exposure

Question 39

where do centres prescribe to

Answer 39

max lung dose some prescribe to pelvis

Question 40

what will happen if there is a gross difference between remaining MU and brass compensator

Answer 40

2 re-calculations

Question 41

whats the dose for the ALL-RIC trial

Answer 41

8Gy in 4

Question 42

what is the dose for specific BM transplants

Answer 42

14.4Gy in 6, 2x a day

Question 43

what is the dose for umbilical transplants

Answer 43

4Gy in 2 in 2 days

Question 44

what is the dose for a reduced intensity allogenic SCT

Answer 44

2Gy in 1

Question 45

what is the varian MU/min

Answer 45

300

Question 46

what is the elekta MU/min

Answer 46

320 (in mosaiq 350)

Question 47

what is the total MU

Answer 47

2100/2600

Question 48

how many MU can be delivered in one go

Answer 48

1000, which is split into three for each field

Question 49

what does fractionation do

Answer 49

spares late damage affects normal tissue toxicity

Question 50

what is implications for single exposure

Answer 50

greater normal tissue damage

Question 51

what does dose rate influence

Answer 51

normal tissue toxicity

Question 52

early toxicities

Answer 52

nausea + vomiting diarrhoea (1/3 pts) circulating platelets [risk of haemorrhage] circulating WBC [neutropenic sepsis - 5% mortality due to this or pneumonitis] photophobia conjunctival oedema dry eye syndrome xerostomia parotitis (swelling of parotid glands, jaw pain) pancreatitis skin erythema (except 20-22MeV) headache hyperpyrexia (not common after 24 hrs)

Question 53

what are the intermediate toxicities

Answer 53

radiation induced interstitial pneumonitis moist desquamation somnolence syndrome - drowsiness, headache, anorexia (6 wks post) alopecia immunodeficiency - defective T and B cells heaptic-veno-occlusive disease - jaundice, hepatomegaly and ascites - had a 50% mortality rate [occurs in 25% of pts]

Question 54

why do we destroy a pt immune system

Answer 54

to reduce the risk of GvHD, due to the T cell depletion of donor BM

Question 55

what are the late toxicities

Answer 55

infertility menopausal symptoms endocrine failure - thyroid no longer functioning, no metabolism if no medication is given growth impairment [likely with a single fraction] osteoporosis + aseptic necrosis intellectual impairment pulmonary bronchiolitus obliterans [popcorn lung- narrowed airways] hyper-pigmentation early cataracts [5-30%] hepatic/renal damage carcinoma induction: lymphomas/solid tumours

Question 56

what happens with higher doses

Answer 56

incidence rates increase for inducing carcinomas

Question 57

what does toxicity depend on

Answer 57

dose single exposure: around 2nd hour fractionated: 2nd/3rd fraction [approx half way]

Question 58

what is the advice for returning back to normal

Answer 58

careful eating and drinking libido reduced for months can socialise after 3-6 months avoid travelling aborad for a year avoid sunburn for two years