this slide is about the report 83 which is published by international commission for units and measurements on the topic dose prescription reporting and recording in intensity modulated radiation therapy . it is useful for personals and students in the field of radiation oncology.

1. ICRU 83
Prescribing, Recording, and
Reporting Photon-Beam
Intensity-Modulated Radiation
Therapy
Anagha S Pachat
MSc Radiation Physics
University of Calicut

2. ICRU 83
 The present report is based on concepts
and definitions previously introduced
in ICRU Reports 50 and 62.
This provides the information
necessary to standardize techniques and
procedures and to harmonize the
prescribing, recording and reporting of
IMRT.

3. Why we need this report??
 By the evolution of modern
technologies conformity of
radio therapy techniques
has increased
 It necessitate extreme care
in volume delineation , dose
prescription and recording

4. ICRU83
▪ IMRT has large number of degree of freedom
and it use variable intensity beam lets
▪ Manual comparisons of all possible intensity
patterns are not practical
▪ Thus some evaluation tools have to be used
such as DVH

5. ICRU 83
▪ In this report the use of DVHs in
prescribing, recording and reporting is
emphasized
▪ The dose-volume histogram ( DVH ) has
become a critical tool to evaluate complex
3D absorbed-dose distributions, and its use
is even more important for IMRT.

6. ICRU 83
▪ It is recommended that the dose-volume
specifications be used for reporting the
treatment plan.The absorbed dose that
covers a specified fractional volumeV, DV,
should be reported. ( For example, D95% is
the absorbed dose that covers 95% of the
volume).

7. ICRU83
▪ The report recommends that the median absorbed
dose, specified by D50%, should be reported, instead
of previously defined dose at the ICRU reference
point Dref.
▪ D50% – is the absorbed dose received by 50% of the
volume, is often a good choice for a representative
absorbed-dose value for the PTV.

8. ICRU 83
▪ The dose-volume metric D100%would be
commonly called the minimum absorbed dose.
▪ The minimum absorbed dose might not be
accurately determined because it is often
located in a high-gradient region at the edge of
the PTV, making it highly sensitive to the
resolution of the calculation.

9. ICRU 83
▪ Therefore, reporting of D100% is not recommended
because the PTV cannot be determined with
sufficient accuracy .
▪ Reporting of minimum absorbed dose should be
replaced by the better determined near-minimum
absorbed dose, D98% , also designed Dnear-min.
▪ Other dose-volumes values, such as D95%, may also
be reported but should not replace the reporting of
D98%.

10. ICRU 83
In previous ICRU Reports, it was recommended to report the
“ maximum absorbed dose “.
In the ICRU83 Report, is recommended the near-maximum
absorbed dose, D2% , as a replacement for the “ maximum
absorbed dose “
It is recommended that D2% also be reported as it is simple to
obtain and will add to consistency of reporting.

12. ICRU 83 Prescribing and Reporting
Historically, the ICRU ( 1993, 1999, 2004
and 2007 ) identified three levels of
prescribing and reporting:
 - Level 1
 - Level 2
 - Level 3

13. ICRU 83 – P & R Level 1
▪ Is considered the minimum standard
required in all centers, a standard below
which radiotherapy should not be
performed
▪ Level 1 is sufficient for treatments and
implies that knowledge of absorbed
doses on the central beam axis is
known and that simple two-
dimensional ( 2D ) absorbed-dose
distributions at the central axis are
available.

14. ICRU 83 – P & R Level 2
▪ Level 2 prescribing and reporting implies
that the treatments are performed using
computational dosimetry and 3D
imaging. At this level, it is assumed that
all volumes of interest are defined using
CT or MR and the 3D dose distributions
are available and include heterogeneity
corrections.

15. ICRU 83 – P & R Level 2 cont..
▪ It is expected that dose-volume
histograms ( DVH´s) for all volumes
of interest are routinely computed.
▪ It is also assumed that a complete
QA program is in place to ensure
that the prescribed treatment is
accurately delivered.

16. ICRU 83 – P & R Level 3
▪ Reporting at Level 3 includes the
development of new techniques
and
▪ approaches for which reporting
criteria are not yet established .
Examples include the use of
concepts such as tumor-control-
probability (TCP ) normal tissue
complication probability ( NTCP ),

17. TCP and NTCP
 TCP is then interpreted as the
probability of tumor
clonogens not surviving
anywhere in the tumor.
 NTCP stands for normal tissue
complication probability
 TCP follows a sigmoid curve
from zero control at some low
absorbed dose to certain local
control at high absorbed
doses

18. MATHEMATICAL FORMULA
TCP = e-(SF × N) NTCP=
1/1+(D50D)k
SF=survival fraction
k = slope of dose–
response curve
D = total dose
D50 = tolerance dose
The main aim of radiation
therapy is to maximize the
TCP and minimize NTCP

19. ICRU 83 – Homogeneity & Conformity
Dose homogeneity
characterizes the
uniformity of the
absorbed-dose
distribution within the
target .
Homogeneiy index is defined as,
HI = D2%-D98%
D50%
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

20. CONFORMITY AND CONFORMITY INDEX
Dose conformity
characterizes the degree to
wich the high-dose region
conforms to the target
volume, usually the PTV.
CI=TV/PTV
It can be employed when the PTV is fully
enclosed by theTreatedVolume.
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.

21. Examples of low and high dose homogeneity and dose conformity.

22. ICRU VOLUMES
▪ Delineation of volumes is an obligatory step
in the planning process
▪ several volumes related to both tumor and
normal tissues have been defined for use in
the treatment-planning and reporting
processes.

23. DEFINEDVOLUMES ARE
Gross tumor volume or GTV
 Clinical target volume or CTV
 Planning target volume or
PTV
 Organ at risk or OAR
 Planning organ-at-risk
volume or PRV
 Internal target volume or ITV
Treated volume orTV
 Remaining volume at risk or

24. Gross tumor volume (GTV)
▪ The GTV is the gross demonstrable extent and location of the tumor.
▪ The GTV may consist of
▪ primary tumor (primary tumor GTV or GTV-T),
▪ metastatic regional node(s) (nodal GTV or GTV-N),
▪ distant metastasis (metastatic GTV, or GTV-M)
▪ In case of post-operative irradiation there is no GTV to define, and only a
CTV needs to be delineated
▪ An adequate absorbed dose must be delivered to the whole GTV to
obtain local tumor control.

25. CLINICAL TARGET VOLUME
The CTV is a volume of tissue that contains a demonstrable GTV and/or
subclinical malignant disease with a certain probability of occurrence
considered relevant for therapy
typically a probability of occult disease higher than from 5 % to 10 % is
assumed to require treatment
The delineation of the CTV is currently based on clinical experience

26. INTERNAL TARGET VOLUME
ITV was defined as the CTV plus a margin taking
into account uncertainties in size, shape, and
position of the CTV within the patient. Such a
margin was called the internal margin
It was first introduced in ICRU62

27. PLANNING TARGET VOLUME
The PTV is a geometrical concept introduced for
treatment planning and evaluation. It is the
recommended tool to shape absorbed-dose distributions
to ensure that the prescribed dose is actually absorbed in
the CTV .
The delineation of the PTV utilizes knowledge of the
presence and impact of uncertainties and variations in
both the tumor location and machine parameters

28. PTV cont..
To ensure accurate reporting of absorbed dose to the PTV in cases for
which the PTV encroaches or overlaps another PTV, OAR, or PRV, it is now
recommended that the delineation of the primary PTV margins should not
be compromised
in such cases subdivision of the PTV into regions with different prescribed
absorbed doses (so-called PTV-sub volumes, PTVSV) may be used
The dose reporting should, however, be done for the whole PTV

29. Pictorial representation

30. ORGAN AT RISK
The OAR or critical normal structures are tissues that if irradiated
could suffer significant morbidity and thus might influence the
treatment planning and the absorbed-dose prescription
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.

31. 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.

32. TREATED VOLUME
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, 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

33. REMAINING VOLUME AT RISK (RVR)
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

34. Conclusion
ICRU 83 is the recent update published on
prescribing recording and reporting
The aim of this report is to standardize and
harmonize all these process
It is very important to follow these
recommendations to achieve the aim of
radiotherapy
This report is being followed since 2010 by most of
the institutions