SRS (stereotactic radiosurgery) Flashcards
srs hallmarks
high degree of dose conformity & beam accuracy
srs dose uses what kind of beams
uses circular beams
3 types of rad used for srs & srt
- heavy charged particles/p+
- Co-60 gamma rays (30Ci)/MV x-rays (most commonly used)
- neutron
srs dosim requires what kind of profiles
cross beam profiles
srs dosim complicated by ? relative to field dimension
detector size
brw stands for
brown-robert-wells frame
srs cross beam measurement done with
diodes & film
srs depth dose distrib measurement done with
- parallel plate
- smaller chamber
- films
- diodes
srs output measurement for small field done with
- film
- tld
- diodes
srs collimation uses what attached below jaws to reduce geometric penumbra
-long cones to extend SDD
gamma knife delivers radiation to target by simultaneous irradiation with large # of
isocenter gamma ray beams
gamma knife distance
40.3 cm
gamma knife tx isoline
50% isoline
gamma knife CR tilted angle of
55deg
gamma knife apparatus
leksell’s frame
gamma knife treats what size lesions
small lesions (4cm)
UT- srs dose
15-24 Gy/fx
srs uses ? beams delivered through what kind of arcs
narrow multiple beams delivered thru non-coplanar isoctr arcs
srs has what size target
larger target
srs has a high/low Rx dose
lower
srs dose
12-25Gy
srt dose
42Gy (7Gy/fx, every other day) or 40Gy (4Gy/fx-10 fx daily)
linac srs is used to tx what size tumors-x-ray knife
- large tumors
- use
large tumors
linac srs uses what kind of beam orientation
mult non-cop arcs of circular beams converging @ iso placed @ target vol
srs dosimetry uses what in formulas
tmr’s or pdd (cax depth distrib), output factors (Sc, Sp), off axis ratios
srs dosimetry complicated by possible lack of
charged particle equilibrium
in srs dosimetry detector size must be ? compared to field size
as small as possible
srs output for large field done with
parallel plate
gamma ray vs x-ray knife conformality
gk more conformal than xray knife unless xray knife has dynamic mlc
gamma knife max diameter
18mm
