ICRU THEORY

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  • 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
    • 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.

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