The document discusses guidelines from the International Commission on Radiation Units and Measurements (ICRU) for prescribing, recording, and reporting intensity-modulated radiation therapy (IMRT). It describes the different target volumes and organs at risk that must be delineated for treatment planning according to ICRU reports 50, 62, and 83. These include the gross tumor volume, clinical target volume, planning target volume, internal target volume, treated volume, and irradiated volume. Factors such as margins for internal motion and patient setup must be considered when defining volumes. Dose specifications, dose-volume histograms, conformity, and homogeneity are also discussed. Proper delineation of volumes and standardization of dose reporting are emphasized.

1. ICRU Volumes for
Prescribing, Recording, and
Reporting
Photon-Beam Intensity-
Modulated
Radiation Therapy (IMRT)
ALTHAF JOUHAR K
M.Sc. RADIATION PHYSICS
CALICUT UNIVERSITY
ICRU 50,62,83

2. Turn Up Your Volume
ICRU Guidelines
Internationally accepted recommendations on
Radiation-related quantities and units, measurement
procedures, and reference data for the safe and
efficient application of ionizing radiation to
medical diagnosis and therapy, radiation science and
technology, and radiation protection of individuals
and populations

3. INTERNATIONAL COMMISSION ON
RADIATION UNITS AND
MEASUREMENTS ( ICRU )
ICRU 50 (1993): 1993 to 1999
ICRU 62 (1999): 1999 to till date
ICRU 83 (2010): 2010 on wards

4. Volumes defined prior to treatment planning :
- Gross Tumor Volume (GTV)
- Clinical Target Volume (CTV)
Volumes defined during the treatment planning :
- Planning target Volume (PTV)
- Organs at Risk (OAR)
- Treated Volume (TV)
- Irradiated Volume (IrV)
ICRU 50

5. GROSS TUMOR VOLUME ( GTV)
 Gross palpable or visible/demonstrable extent and
location of the malignant growth.
 It consists of :
- Primary tumor
- Metastatic lymphadenopathy
- Other metastasis
 If the tumor has been removed prior to radiotherapy
then no GTV can be defined.

6.  GTV can be determined by using either clinical
examination (inspection, palpation) and by various
imaging techniques (X-rays, CT, MRI etc).
 Method used for determination of GTV should meet the
requirements for staging the tumor according to the
clinical TNM.

7.  It is a tissue volume that contains a GTV and/or subclinical
microscopic disease, which has to be eliminated.
 This volume has to be treated adequately in order to
achieve the aim of therapy : cure or palliation.
 The delineation of this volume requires consideration of
factors like local invasive capacity of the tumor and its
potential to spread to different regions ( eg: regional
lymph nodes).
CLINICAL TARGET VOLUME ( CTV )

8. The delineation of GTV and CTV are based on purely
anatomic-topographic and biological considerations
without regard to technical factors of treatment.
GTV CTV

9. PLANNING TARGET VOLUME ( PTV )
 The planning target volume is a geometrical concept, and it
is defined to select appropriate beam arrangements, taking
into consideration the net effect of all possible geometrical
variations, in order to ensure that the prescribed dose is
actually absorbed in the CTV .
 It is used for dose planning and for specification of dose.
 The PTV is linked to the reference frame of the treatment
machine.
 It is often described as the CTV plus a fixed or variable
margin (e.g., PTV = CTV + 1 cm).
 Usually a single PTV is used to encompass one or several
CTVs to be targeted by a group of fields.

10. Planning Target Volume (PTV)

11.  It is a volume enclosed by isodose surface, selected and
specified by the radiation oncologist as being appropriate to
achieve the purpose of treatment .
 It may closely match to the PTV or may be larger than the PTV.
 If, however, it is smaller than the PTV, or not wholly enclosing
the PTV, then the probability of tumor control is reduced and
the treatment plan has to be re-evaluated or the aim of the
therapy has to be reconsidered.
TREATED VOLUME

12.  It is that tissue volume which receives a dose that is
considered significant in relation to normal tissue
tolerance.
 It depends on the treatment technique used.
IRRADIATED VOLUME ( IrV )

13. ORGANS AT RISK (OAR)
 These are normal tissues whose radiation sensitivity may
significantly influence the treatment planning and/or
prescribed dose.
 They may be divided into 3 classes :
Class I : Radiation lesions are fatal or result in severe
morbidity.
Class II : Radiation lesions result in mild to moderate
morbidity.
Class III : Radiation lesions are mild, transient, and
reversible, or result in no significant morbidity.

14. ICRU 50
Irradiated Volume
Treated Volume
Planning Target Volume
(PTV)
Clinical Target Volume
(CTV)
Gross Tumor Volume
(GTV)

15. ICRU REPORT 62 ( Supplement to ICRU
REPORT 50 )
 Gives more detailed recommendations on the different
margins that must be considered to account for
anatomical and geometrical variations and uncertainties.
 Introduces the concept of Conformity Index ( CI )
 Gives information about how to classify Organs at Risk.
 Introduces a Planning Organ at Risk Volume ( PRV )
 Gives recommendations on graphics.

16.  Consists of the CTV plus an internal margin.
 It is the margin given around the CTV to compensate for all
variations in the site, size and shapes of organs and tissues
contained in or adjacent to CTV.
 The internal margin is designed to take into account the
variations in the size and position of the CTV relative to the
patient’s reference frame (usually defined by the bony
anatomy), i.e., variations due to organ motions such as
breathing, bladder or rectal contents, etc.
Internal Target Volume (ITV)
Internal target volume (ITV) = CTV+IM

17. PLANNING TARGET VOLUME ( PTV ) by ICRU 62
PTV=CTV+IM+SM
 Introduce the concept of setup margin.
 Setup margin is the Uncertainty in patient
positioning and mechanical uncertainty of the
equipment which arise due to sagging of gantry
or collimator or couch, Dosimetric uncertainty,
transfer setup error , human error, etc.

18. Planning Organ at Risk Volume (PRV)
 This is a volume which gives into consideration the
movement of the Organs at Risk during the treatment.
 An integrated margin must be added to the Organ at
Risk to compensate for the variations and uncertainties,
using the same principle as PTV and is known as the
Planning Organ at Risk volume ( PRV ).
 A PTV and PRV may occasionally overlap.

19. ICRU REPORT 83 ( Supplement to ICRU
REPORT 62 )
 Gives more detailed recommendations on the different
margins that must be considered to account for
anatomical and geometrical variations and uncertainties
 Introduces a Remaining Volume at Risk ( RVR )

20. Ideally when delineating the OAR, especially for
IMRT, all normal tissues that could potentially be
irradiated should be outlined. The imaged volume
within the patient, excluding any delineated OAR
and the CTV(s), should be identified as the RVR
Remaining Volume at Risk (RVR)

21.  It is defined as the quotient of the Treated Volume (TV)
and the Planning Target Volume (PTV).
 It can be employed when the PTV is fully enclosed by the
Treated Volume.
 It can be used as a part of the optimization procedure.
 Dose conformity characterizes the degree to which the
high-dose region conforms to the target volume,
usually the PTV.
CONFORMITY INDEX ( CI )

22. Dose Homogeneity
 Dose homogeneity characterizes the uniformity of the
absorbed-dose distribution within the target volume.
 Homogeneity index is defined as,
Dose-volume reporting
 - D50% (Dmedian), Dose received by 50% of PTV
 - D98% : Dose received by 98% volume of PTV
 - D2% : Dose received by 2% volume of PTV
HI = D2%-D98%
D50%

23.  Delineation of these volumes is an obligatory step in the
planning process, as absorbed dose cannot be prescribed,
recorded, and reported without specification of target
volumes and volumes of normal tissue at risk.
 The ICRU previously recommended that the absorbed
dose in the PTV be confined within 95 % to 107 % of the
prescribed absorbed dose(ICRU, 1999). With IMRT, these
constraints can be unnecessarily confining if the
avoidance of normal tissue is more important than target-
dose homogeneity. In the present Report, it is
recommended that the extent of high- and low-dose
regions is specified using dose–volume quantities such as
D2 % and D98 % for regions of high and low absorbed
dose, respectively.
Dose Volume Specifications

24.  DVH summarizes the entire dose distribution into a
single curve for each anatomic structure of interest.
 The main use of DVH is as a plan evaluation tool.
 IMRT is an approach to conformal therapy that not only
conforms (high) dose to the target volume but also
conforms (low) dose to sensitive structures.
 Volume out side PTV that receives dose larger than 100%
of PTV dose is called Hot Spot.
 Volume inside the PTV that receives dose lower than 95%
that of PTV dose is called Cold Spot.
Additional information which is ultimately contributes to
the developments and improvements in Radiotherapy.

25.  Proper identification and delineation of GTV is the
most important factor in treatment.
 Other volumes like CTV, PTV, ITV should also be
properly delineated.
 The errors like set-up error and human errors should
be kept to a minimum.
 Dose prescription, fractionation and calculation
should be done in the same way by all the different
centers throughout the world for the proper exchange
of information and reporting.
CONCLUSIONS

26. Thank you