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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
Q

what are the types of AL

A

remote
manual
loaded by hand
loaded under computer control

26
Q

what is a LDR dose rate

A

0.4-1/2 Gy/hour (Caesium-137 and iridium- 192)

27
Q

what is a medium dose rate

A

2-12Gy/ hour

28
Q

what is a HDR

A

> 12Gy/hour (iridium-192 and cobalt-60)

29
Q

PDR

A

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
Q

temp has what dose rate

A

high

31
Q

describe the use of stable iridium

A

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
Q

HDR has more or less half life

A

less

33
Q

LDR has more or less half lives

A

more

34
Q

shielding

A

room design, observation via camera, temp safe for short term storage and emergency

35
Q

time: temporary

A

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
Q

time: permanent

A

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
Q

distance

A

achieved by forceps, never handle applicators of transfer tubes

38
Q

remote AL

A

confirmation of source position
inserted into applicator system
no exposure to staff

39
Q

manual AL

A

confirmation of source position
operator inserts onto position
staff will receive a measurable dose
regular updates
equipment for protection
min exposure to staff

40
Q

requirements for remote

A

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
Q

AL components

A

source safe
source transit system
applicator system
safety system

42
Q

HDR advantages

A

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
Q

HDR disadvantages

A

if an issue exposure is> than LDR
shielding requirements if Co-60 is used
regular source replacement for iridium- 192
radiobiology

44
Q

LDR advantages

A

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
Q

LDR disadvantages

A

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
Q

HDR: microelectron

A

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
Q

curation

A

6 channels
fewer patients can be treated

48
Q

stepping sources

A

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
Q

flexitron: elekta

A

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
Q

radiobiology

A

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
Q

where is recurrence likely

A

hypoxic región, more cells survive in HDR, due to sub lethal damage being continuous, overtime this accumulation causes damage

52
Q

what does PDR mimic

A

LDR and HDR

Pelvis and Abdomen: R&O (22 decks)

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