ICRU 50 and ICRU62

Question 1

volumes defined prior to treatment planning

Answer 1

GTV
CTV

Question 2

volumes defined during treatment planning

Answer 2

PTV
OAR
TREATED VOLUME
IRRADIATED VOLUME

Question 3

PTV

Answer 3

-geometircal concept
-used for dose planning
-selects apt beam arrangement, taking net effects of all possible geometrical variations into consideration

Question 4

treated volume

Answer 4

-enclosed by isodose surface
-may closely match to PTV or larger
-if small=probability of tumour control↓ and treatment re-evaluated

Question 5

Irradiated volume

Answer 5

tissue that recieves dose considered significant compared to normal tissue tolerance

Question 6

OAR

Answer 6

normal tissue whose radiation sensitivity may significantly affect treatment planning or/and prescribed dose

Question 7

OAR classification

Answer 7

CLASS I= fatal or severe morb
CLASS II= mild to moderate morb
CLASS III=mild/transient/reversible/no morb

Question 8

TARGET VOLUME WAS SEPARATED INTO 3 VOLUMES

Answer 8

GTV
CTV
PTV

Question 9

GTV
CTV

Answer 9

-visible tumour
-volume to account for microscopic tumour spread uncertainties

Question 10

significance of identification of GTV

Answer 10

-adequate dose can be delivered to GTV to have TUMOUR CONTROL
-to allow recording of TUMOUR RESPONSE in relation to dose and its variation

Question 11

ICRU 62:
what does it do

Answer 11

-more detail recommendations on different margins
-introduces conformity index and PRV
-new way to classify OAR
-redefines PTV by introducing concept of : SM and IM (these compensate for different types of uncertainties)

Question 12

ITV

Answer 12

-CTV+internal margin
-compensates for all variations in site shape and size of organs adjacent or in CTV eg. respiration or rectum motion

Question 13

PTV… by ICRU62

Answer 13

-ITV+SM
introduces the concept of set up margin.

margin for uncertainty in positioning and mechincal equip which can arise from things like couch sag

Question 14

internal margin

Answer 14

takes into account variation of size shape and position of CTV in reference to its internal reference point.

due to physiological variations eg filling of bladder

Question 15

New classification of OARS

Answer 15

serial
parallel
serial and parallel

Question 16

serial

Answer 16

continous unit , damage at one point will cause complete damage of whole organ eg spinal cord

point dose is significant

Question 17

parallel

Answer 17

several functional units , if one part is damaged , the rest of organ will make up for its loss eg lung or bladder

dose delivered to a given volume OR mean dose is considered

Question 18

serial parrallel

Answer 18

eg kidney (glomerulus is parallel and tubules sare serial)

Question 19

report 62 addresses a limitation. of report 50

Answer 19

didnt account for OAR movement and changes in size and / or shape

PRV= margin around OAR to compensate for geometric uncertainties

Question 20

Conformity Index

Answer 20

-quotient of TV and volume of PTV
-used when PTV is fully enclosed by TV

Question 21

Both ICRU 50&62 define series of doses

Answer 21

min dose
max dose
icru reference dose (defined at ICRU reference point)

Question 22

ICRU reference point should be chosen based on this criteria

Answer 22

-clinically revelent and defined in an unambigious way
-located where the dose can. be accurately determind
-in a region where there are no steep dose gradients

this should be in the middle of the PTV

Question 23

Max dose

Answer 23

-max dose to PTV and OARs
-dose reported as maximum only when the volume of the tissues’s diameter is. more than 15mm
-if max dose outside the pTV exceeds prescribed dose=hot spot

Question 24

Min dose

Answer 24

-min dose in defined volume
-no volume limit recommended when reporting min dose