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Pelvis and Abdomen: R&O > Brachytherapy > Flashcards

Brachytherapy Flashcards

1
Q

four types of BT

A

interstitial
intra-cavity
intra-luminal
surface applicators

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2
Q

intra-cavity

A

most common
placed in pre-exisiting body cavity
temp implant
images are captured to make sure implant is positioned correctly

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3
Q

interstitial

A

positioned surgically into tissue
sources must have small diameter
breast, tongue, anus, prostate
temp or permanent
positioned via remote after loading equipment returned to the source safe afterwards

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4
Q

surface applicators

A

treats the body surface
maintained at a short distance
useful in malignancies overlay sensitive tissue
superficial malignancies
temp

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5
Q

intra-luminal

A

positioned in the lumen
only HDR
bronchus and oesophagus
temp

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6
Q

properties of an ideal source

A

high specific activity
gamma energy approx 0.5MeV
small and flexible
half life is long enough correction for decay is minimal

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7
Q

what is temp source

A

when the radioactive source is placed in the body for a period of time which is then removed, only for treatment.
energy of the sources is normally over 0.5MeV

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8
Q

what is permanent source

A

placed inside or near the tumour which is not removed.
short half life and low energy
implantation pattern is specific to the tumour
more limited with the type of BT

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9
Q

what is a sealed source

A

radioactive material which is either permanently sealed in a capsule or bonded closely in solid form
EITHER PARTICLES OR GAMMA RAYS NOT BOTH

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10
Q

when can a gamma ray source be used

A

if the particles are removed capitulating the source removes the beta particles

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11
Q

what does a metal encasement do

A

prevent escape of the material, particularly any gaseous daughter products
absorb alpha and beta particles formed in the decay process

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12
Q

what is the only source which is not sealed

A

IRIDIUM-192
SOURCE IS RELEASED WHEN WIRES ARE CUT

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13
Q

describe BT for prostate gland

A

reached via the perineum, it is confided to this area, to reduce effects . Guide needles are placed into the prostate via a template which is attached to the perineum, once in the right position plastic applicators are threaded through the guide needed, imaging checks position

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14
Q

what is used for pelvic regions

A

gamma rays

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15
Q

what is the role of the capsule in pelvic regions

A

removes the gamma rays which shields the patient, gamma rays are emitted from the nucleus. The energy is dependent on the source

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16
Q

what is the energy that radiation protection has to be provided for

A

1.33 MeV

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17
Q

what are orphan sources

A

not managed by an authorised body

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18
Q

high activity sealed sources

A

controlled by right laws
high radiation output
potentially hazardous
BSSD have requirements for maintaining accurate and up to date records of location, composition and activity level of HASS

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19
Q

cat 1

A

death or severe injury if in close contact for a short period of time

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20
Q

cat 2

A

in contact longer than cat 1: industrial gamma radiography, HDR brachytherapy

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21
Q

cat 4

A

temp injury, longer period than cat 3, permanent injuries are unlikely
LDR brachytherapy

22
Q

loading

A

describes how sources are loaded into their applicators and placed in the body

23
Q

pre loading

A

positioning applicators into the body with rs loaded, no imaging

24
Q

after loading

A

empty applicators are loaded into the body, image to check position before active sources are placed into the patient

25
what are the types of AL
remote manual loaded by hand loaded under computer control
26
what is a LDR dose rate
0.4-1/2 Gy/hour (Caesium-137 and iridium- 192)
27
what is a medium dose rate
2-12Gy/ hour
28
what is a HDR
>12Gy/hour (iridium-192 and cobalt-60)
29
PDR
it is a combination of HDR & LDR LDR has long treatment time and uncomfortable whereas HDR is quicker it is a LDR treatment which is stimulated by pulses each pulse in 10 minutes with an hour interval higher number of fractions than HDR, lower risk of overdosing in-between pulses restrictions are lifted
30
temp has what dose rate
high
31
describe the use of stable iridium
it is placed in a neutron influx, the longer its left the more stable neutrons are able to become unstable increasing specific activity means less source is required higher number of iridium converted means a higher activity to the source as the concentration of unstable atoms is higher
32
HDR has more or less half life
less
33
LDR has more or less half lives
more
34
shielding
room design, observation via camera, temp safe for short term storage and emergency
35
time: temporary
ensure no overdose dependent on DR individual calculation if staff needs to enter it is timed procedure: source leaves AL equipment, moving into the body, remains for the calculated period of time radiographer never handles the source safe unless source gets stick
36
time: permanent
RS remains in situ: not removed isolation, emitting gamma rays constantly isolated period is calculated time limits are set for contact gamma rays are low energy measured in Kev
37
distance
achieved by forceps, never handle applicators of transfer tubes
38
remote AL
confirmation of source position inserted into applicator system no exposure to staff
39
manual AL
confirmation of source position operator inserts onto position staff will receive a measurable dose regular updates equipment for protection min exposure to staff
40
requirements for remote
accurate control of source position source positon indicator small physical size source flexible short source transit tubes [source-transit system, gets source from safe to applicator] automated return of source backup power supply exposure warning system low transit dose automated computerised correction for source decay computerised controlled planning safe
41
AL components
source safe source transit system applicator system safety system
42
HDR advantages
minimal discomfort treatment time is in minutes all four types can be used high number of treatments can be completed in a day source replacement is infrequent Co-60 every 4 years cost per patient is low day case patients radiation safety improved no visiting restrictions
43
HDR disadvantages
if an issue exposure is> than LDR shielding requirements if Co-60 is used regular source replacement for iridium- 192 radiobiology
44
LDR advantages
low levels of discomfort radiobiologically range of applicators for intracavity low staff exposure dual channel equipment, can treat two patients at the same time tissue exposure< HDR caesium working life is 20+ years shielding requirements are less than Co-60
45
LDR disadvantages
less patients through each day treatment is measured in hours doesn't treat intra-luminally cost per treatment is high iridium-192 regular replacements discomfort visiting is required
46
HDR: microelectron
heavy safe used, depends on the source type mobile unit: transports machine source travels from source safe to temp safe = holding part end part: source leaves the machine separate control panel
47
curation
6 channels fewer patients can be treated
48
stepping sources
remote AL equipment = IRS source is programmed to travel through the prescribed applicators sources move in steps inside the applicator delivering dose as it moves for every step, the source is programmed to remain in position for a period of time DWELL position source is found at the wire tip
49
flexitron: elekta
mobile unit: motor controlled RS leaves the top tungsten safe: protects up to 20Ci source to max 22Ci source 20 treatment channels, each channel takes the source out of the machine into the patient each channel has an interlock iridium-192, Yttritum-169 dual or single source used for HDR, LDR
50
radiobiology
very steep dose rates around implanted sources normal tissues receive lower doses than EBRT LDR provides sub-lethal damage, allowing for recovery treatment distance is 1-2cm, doubling distance quarters the intensity LDR= more cells survive than oxygenated tumours as they repair more easily HDR = better at killing oxygenated tumour cells, therefore better at killing tumours
51
where is recurrence likely
hypoxic región, more cells survive in HDR, due to sub lethal damage being continuous, overtime this accumulation causes damage
52
what does PDR mimic
LDR and HDR

Pelvis and Abdomen: R&O (22 decks)

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