ICRU THEORY
- Created by: alis142
- Created on: 20-11-19 13:43
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- ICRU THEORY
- ICRU 50
- Prescribing, recording and reporting photon beam RT
- Recommends on how to report a tx in external photon beam therapy.
- Followed worldwide
- Tx delivery volumes and doses must be specified. Purpose:
- Consistent practice
- Comparision of results
- Dissemination of data
- Trials and multi centre studies
- Not advised for:
- Tx techniques
- Absorbed dx
- Improvements since 1993
- MLC and IMRT
- Planning systems 3D algorithms and outlining tools.
- Imaging techniques: 3D impact on target and OAR definitions
- ICRU 62
- Intended to be used in conjunction w/ Report 50
- Complement recommendations
- Reflects their development
- 62
- Aim of therapy
- Definitions of volumes
- Specifications of doses
- ICRU Volume Recording and Reporting
- GTV Gross Tumour Volume
- The gross palpable, visible or demonstrable extend and location of malignant growth
- CTV Clinical Target Volume
- Tissue volume contained GTV and/or sub-clinical microscopic malignant disease
- PTV Planning Target Volume
- Geometrical Concecept
- To select appropriate beam sizes and beam arrangements to ensure prescribed dx is delivered to the CTV
- Concept of margins introduced in
- CI Conformity Index
- Employed when PTV fully enclosed by TV
- CI is the quotient of the TV and PTV
- Used as part of optimization procedure
- TV Treated Volume
- Volume enclosed by isodose surface, selected and specified by clinician as appropriate to achieve purpose of tx.
- IV Irradiated Volume
- Tissue volume receiving a dose considered significant in relation to normal tissue tolerance
- PRV Planning OAR Volume
- Normal tissues whose rx sensitivity may significantly influence tx planning or prescribed dx
- Margins
- IM Internal Margin
- CTV Size, shape and position variations in relation to anatomy and organ motion
- Leads to concept of ITV Internal Target Volume
- SM Setup Margin
- Uncertanties in pt positioning, immobilisation
- Uncertanties in beam positioning, mechanicqal stability
- IM Internal Margin
- GTV Gross Tumour Volume
- Intended to be used in conjunction w/ Report 50
- ICRU 83
- TARGET VOLUMES
- Concepts of GTV, CTV and PTV remain critical improtant
- GTV should be delineated on a 3D basis using clinical, anatomical and functional imaging modalities
- Accommodate delineation of multiple GTV's. Because delineation of GTV can vary according to diagnostic imaging modality, clear annotation of volume name is required.
- I.E. GTV-T (MRI-T2), GTV_N (Nodes), GTV-M (Metastases)
- Names should reflect pre or post RT I.E GTV-T (clin, 0Gy), GTV-T ( MRI-T1, 30Gy)
- OAR
- In IMRT, organs or structure not delineated can receive significant rx absorbed dx
- Contouring OAr is 1st step controlling dose in normal tissues
- For parallel-like organs; whole organ delineation
- For serial like organs; area of organ that receive high dx should be delineated in consistent way
- For serial-like organs, a planning OAR volume (PRV) should be delineated around OAR
- For tubular organs i.e rectum, delineation of wall is preferred to the whole organ.
- Tissues not in CTV or not delineated as dx limiting OAR should still be delineated and names RVR: remaining volume at risk.
- In IMRT, organs or structure not delineated can receive significant rx absorbed dx
- TARGET VOLUMES
- ICRU 50
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