ICRU83

Question 1

ICRU83 is..

Answer 1

supplement to ICRU62
-gives more detailed recom on different margins
-introduces remaining volume of risk RVR

Question 2

RVR

Answer 2

when delineating OAR (esp. for IMRT) all normal tissues that could potentially be irradiated should be contoured

image volume within patient (not incl. OAR +CTV)=RVR

Question 3

3DCRT:
-difficulty
-type of planning
-fluence
-dose
-MU
-ISOCENTRE

Answer 3

-easy
-forward
-uniform
-uniform
-low
-dose defined to volume , spefically at isocentre

Question 4

IMRT:
-difficulty
-type of planning
-fluence
-dose
-MU
-ISOCENTRE

Answer 4

-complex
-inverse
-non-uniform
-high gradient
-high
-isocentre dose is meaningless

Question 5

ICRU 83 take home messages

Answer 5

ICRU ref point not used, volumetric prescription instead

Question 6

ICRU83 vs ICRU 50+62

Answer 6

-previous ICRU report= dose values in PTV are inbetween 95 and 107 of prescribed dose

-BUT w/ IMRT , these constraints maybe confining if avoiding OARs us more important than achieving dose homogenity in target
TF, ICRU83 suggests using D2 and D98 for regions of high and low dose

Question 7

IMRT PTV DOSE DISTRIBUTION

Answer 7

less homogenuous but more conformal than conventional.
also it can produce absorbed dose gradients

Question 8

GTV… same def but

Answer 8

specifications needed:
-TNM staging
-mention site + imaging modality
-record any changes during tx to plan during adaptive tx

Question 9

CTV … same def but

Answer 9

recommend clear annotation used
eg CTV-T+N (CT,35GY)

Question 10

ITV … same def but

Answer 10

better delineation is possible w 4D imaging

Question 11

PTV … same def but

Answer 11

-compromising PTV if overlapped with OAR is no longer recommended
-in this situation PTV is subdivided into subvolumes

Question 12

OAR … same def but

Answer 12

classification is the same (serial , parrallel ect)

Question 13

PRV… same def but

Answer 13

if overlaps w PTV…

PTV +PRV can be subdivided into subvolumes and be given individual absorbed dose constraint

Question 14

TV

Answer 14

same def

Question 15

rationale of RVR

Answer 15

-detects any unsuspected regions of high absorbed dose outside PTV and PRV
-estimates risk of late side effects

Question 16

Dose reporting:
parameters used

Answer 16

Dmean (D50)
D98.. near min
D95
D2..near max
Dv
Vd

Question 17

for reporting PTV and CTV , report

Answer 17

Dmean (D50)
D98.. near min
D2..near max

Question 18

for reporting PRV, report

Answer 18

serial= Dmax/D0 rather than D2%
parallel=Vd (volume recieving atleast the absorbed dose), D mean
serial/ parallel =all 3 parameters

Question 19

Dose homogenity

Answer 19

characterizes the uniformity of the absorbed dose in TV

D2-D98/D50
if HI=0….. dose distribution almost homogenous

Question 20

dose conformity

Answer 20

characterizes how high dose regions conform to PTV

due to use of DVH , use of CI and HI are likely to be limited