clinical practice Flashcards
what is preplanning
consent
localisation
scan and tattoos
why verify ?
to ensure … patient is in same position
treat what you planned
plan is based on
CT scan
Set up error … types
systematic error
random error
what is systematic error
error is reproducable and consistent.
occurs in same direction
what is random error
varies in direction and magnitude for each delivered treatment fraction
GTV
Gross target volume … the tumour
CTV
clinical target volume .. to account for the microscopic diseases you cant see
PTV
planning target volume … to account for set up error
this size depends on what critical structures are near
what is a gross error
error of more than 1cm
what should the space be inbetween CTV and PTV
- 5cm
0. 3cm for head and neck
what is interfraction motion
target and/or patient move between each fraction
what is introfraction motion
target and/or patient move during treatment daily
why do we have set up error
poor immobolisation
poor patient positioning
internal organ motion
how to reduce errors
vertification
take care in p&im
choice of modality depends on…
pt1
technology avail.
treatment site
target positions and dose
choice of modality depends on…
pt2
-patient co-morbities
-imm
treatment intent (rad or pal)
IGRT
image guided radiation therapy
IGRT 2D imaging … used for
what
breast and whole brain
2 pics taken 2gether aka ORTHOGONAL IMAGES
IGRT 2D imaging uses
mv image…. can only see soft tissue no bone
IGRT volumetric 3D imaging uses
KV or MV image
limitation of IGRT 3D
accumlated dose bit higher
takes longer to get (adquire)
MV images can be
single or double
KV images can image
area close to isocentre
properties of kv imaging
mainly seen in RT. department requires additional software gives less dose improves image clarity has fluroscopic mode
emerging IGRT modalities…Surface guided radiation therapy
no radiation involved
surface tracks
what does surface tracking do
- align RT or Vision RT
- Track patient 3D surface in real time
- calculate patients movemnet in all 6 degrees of freedom
- monitor respiratory movement
what does seriotactic mean
delivering v high dose
CBCT means
cone beam ct
what is set up error
inconsistency between planned patient position and patient position on that treatment day
less common on treatment
IGRT modalities
high frequency imaging
implated transponders
integrated MR/linac
high frequency imaging
example and properties
cyberknife
non-invasive
use tracking software to track tumour position
0.01-20 cGy
implanted transponders example
calypso
