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Technical issues in breast radiotherapy

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Technical issues in breast radiotherapy

  1. 1. TECHNICAL ISSUES IN BREAST RADIOTHERAPY Dr Bharti Devnani Moderator:- Dr Manoj Kumar Sharma
  2. 2. RADIOTHERAPY BY CONVENTIONAL METHOD
  3. 3. IMMOBILIZATION METHODS FOR IMPLEMENTATION
  4. 4. BREAST BOARD
  5. 5.  Several adjustable features to allow for the manipulation of patients arms, wrists, head and shoulders.  To make chest wall surface horizontal, brings arms out of the way of lateral beams.  Arm abducted at 90⁰ & hand holds handle of arm rest.  Face turned towards opposite side.  Thermoplastic breast support can be added.  Constructed of carbon fiber which has lower attenuation levels permitting maximum beam penetration.
  6. 6. VAC-LOCK
  7. 7. Breast ring with valecro Alpha cradle
  8. 8. FIELD BORDERS
  9. 9. FOR TANGENTIAL FIELDS  Upper border – 2nd ICS (angle of Louis) when supra clavicular field used. When SCF not irradiated – head of clavicle  Medial border – at or 1cm away from midline  Lateral border – 2-3cm beyond all palpable breast tissue – mid axillary line  Lower border – 2cm below inframammary fold  Anterior -2cm margin of light, above the highest point of breast.
  10. 10.  A pectoralis major muscle  B axillary lymph nodes: levels I  C axillary lymph nodes: levels II  D axillary lymph nodes: levels III  E supraclavicular lymph nodes  F internal mammary lymph nodes
  11. 11. HOW TO IMPLEMENT IT? Deciding angle of rotation of gantry for tangential fields:  Lead wire placed on lateral border  Field opened at 0⁰ rotation on chest wall and central axis placed along medial border of marked field  Gantry rotated , until on fluoroscopy, central axis & lead wire intersect – angle of gantry at that pt. noted – medial tangent angle
  12. 12. CENTRAL LUNG DISTANCE  Perpendicular distance from post. tangential field edge to post part of ant. chest wall at centre of field  Best predictor of %age of ipsilateral lung vol. treated by tangential fields CLD (cm) % of lung irradiated 1.5 cm 6% 2.5 cm 16% 3.5 cm 26%
  13. 13. IMPORTANCE OF BEAM MODIFICATION DEVICES (WEDGES)
  14. 14. Higher dose to the apex without wedges
  15. 15. BOLUS  Increases dose to skin & scar after mastectomy  Cosmetic results may be inferior  Universal wax bolus used
  16. 16. IRRADIATION OF REGIONAL LYMPHATICS
  17. 17. SCF IRRADIATION
  18. 18. SCF  Single anterior field is used. Field borders –  Upper border : thyrocricoid groove  Medial border : at or 1cm across midline extending upward following medial border of SCM ms to thyrocricoid groove  Lateral border: insertion of deltoid muscle  Lower border : matched with upper order of tangential fields
  19. 19.  A pectoralis major muscle  B axillary lymph nodes: levels I  C axillary lymph nodes: levels II  D axillary lymph nodes: levels III  E supraclavicular lymph nodes  F internal mammary lymph nodes SUPRACLAVICULAR-AXILLARY FIELD
  20. 20. Humeral head shielding:– • If arm angled >90⁰: Ax nodes overlap head of humerus anteriorly. • Larger the angle – less the head of humerus spared in s.c port
  21. 21. MATCHING SUPRACLAV & CHEST WALL FIELDS
  22. 22. Angulation By inferior angulation of the tangential fields. Half beam block technique Blocking the supraclav field’s inferior half, eliminating its divergence inferiorly . Hanging block technique Superior edge of tangential beam made vertical by vertical hanging block.
  23. 23. Single isocentre technique: • Isocentre placed at the junction of tangential and supraclavicular field • Inferior portion of field blocked for supraclavicular treatment and superior portion blocked for tangential field
  24. 24. IMN IRRADIATION
  25. 25. 1. Extension of tangential fields– by extending medial border – 3cm across midline or by using imaging techniques 2. Separate field – • Medial border – midline , matching with tangential field border • Lateral border – 5-6cm from midline • Superior border – abuts inferior border of supraclav field or at 1st ICS (superior border of head of clavicle) if only IMNs are to be treated • Inferior border – at xiphoid or higher if 1st three ICS covered
  26. 26. More normal tissue is being irradaited. (lung, heart and contralateral breast)
  27. 27. Anterior field Oblique field
  28. 28. MATCHING THE TANGENTIAL BEAMS WITH INTERNAL MAMMARY FIELD
  29. 29. ISSUES WITH DIRECT ANTERIOR FIELD (LARGE BREASTED WOMEN) Cold region:- large amount of breast tissue over the matchline
  30. 30. POSTERIOR AXILLARY BOOST
  31. 31.  Medial border – To allow 1.5-2cm of lung on the portal film  Inferior border – at same level of inferior border of s.c field  Lateral border – just blocks fall off across post axillary fold  Superior border – splits the clavicle  Superolaterally – shields or splits humeral head  Centre – at acromial process of scapula
  32. 32. ELECTRON BOOST
  33. 33. BOOST-ELECTRONS  Appropriate energy selected to allow 85 -90% isodose line to encompass target volume & decrease dose to the lung.  Clinical set up - post lumpectomy volume or scar on skin +3 cm in all directions.  Energy – 9-16 MeV  Dose – 10-20Gy
  34. 34. TREATMENT IN PRONE POSITION
  35. 35. Plexiglas plateform with rounded opening
  36. 36. TREATMENT IN LATERAL DECUBITUS POSITION
  37. 37. Carbon epoxy disposer Opposite breast retracted upwards & outwards from the field by elastic straps
  38. 38. •Useful for voluminous breast •For patients who are heavy smoker and previous history of lung or cardiac disease •For deep seated tumor Disadvantage – For nodal RT treatment position has to be changed
  39. 39. TREATMENT OF BILATERAL BREAST CANCER WITH CONVENTIONAL TECHNIQUE
  40. 40. ROLE OF IMRT IN BREAST CANCER
  41. 41.  Reduces the hotspots specially in the superior and inframammary portions of the breast. Increases homogenity Manifests clinically into decrease in moist desqumation in these areas.
  42. 42. IMRT BREAST: WHY? (1) Better dose homogeneity for whole breast RT (2) Better coverage of tumor cavity (3) Feasibility of SIB (4) Decrease dose to the critical organs (5) Left sided tumors- decrease heart dose
  43. 43. FORWARD PLAN IMRT
  44. 44. ROLE OF 4D-CRT
  45. 45. RTOG GUIDELINES
  46. 46. DURING CT SIMULATION Post-BCS Post-Mastectomy
  47. 47. REGIONAL NODAL CONTOURING
  48. 48. Breast-superior Breast-inferior
  49. 49. SCF begins
  50. 50. Axillary level III begins
  51. 51. Axillary level II begins
  52. 52. Axillary level I begins
  53. 53. Axillary level I ends
  54. 54. IMC begins
  55. 55. IMC ends
  56. 56. THANK YOU
  57. 57. INTERSTICIAL BOOST
  58. 58. When the CTV extends deeper than 28 mm under the epidermal surface, implants have a higher ballistic selectivity in terms of the volume of the irradiated breast tissue and dose to the skin blood vessels than electron beam boosts.
  59. 59. LOCALIZATION OF LUMPECTOMY CAVITY  Pre-op clinical finding , pictures  Imaging- mammogram,usg,MRI  Per-op finding  HPR  Surgical clips  Post op imaging with USG,CT or MRI
  60. 60. Use of marker clips to localise the boost target volume and simulate entrance points of guide needle at the skin of the breast
  61. 61. Use of mammography in defining the boost target localisation in breast conserving treatment
  62. 62. A. Defining the implantation isocentre and definitive needle entrance and exit points at the skin for a breast implant. Reconstruction boost target isocentre from mammography, by simulator, or CT. The indicated entrance points are too close to the target volume (A) B. Inclination of the implantation equator plane away from the target to avoid an overlap of the boost PTV and needle exit points at the skin
  63. 63. (C). Indication of new entrance and exit points, further away from the boost CTV, to avoid skin teleangiectases . (D)Occurrence of severe teleangiectasic ‘stars’ at skin entrance or exit points if rules for implementation are not followed Why this planning so important. With a delivered dose of 50 Gy , chances of late teleangiectases may occur in 30% of cases Vessels may have already received 20–40 Gy from the breast irradiation.Therefore, there is usually only a small dose amount left in skin vessel tolerance for teleangiectases
  64. 64. ANAESTHESIA  Breast implants can easily be carried out under L.A. and premedication with 2.5–5 mg midazolam given 15–30 min before the implantation.(GA, <0.5%)  The patient is placed in supine position with the homolateral arm in 90° abduction.  After the design of implant geometry and localisation of entrance and exit points of the needles, the skin is infiltrated at each point with 0.5–1 ml 1% lidocaine.  Retroareolar region is painful (1-5 ml extra infiltrate in that area)
  65. 65. DESIGN OF THE IMPLANT GEOMETRY  Needles are implanted parallel and equidistance from each other (Paris system).  In most cases inserted in a mediolateral direction.  In very medially or laterally located tumor sites, needles should be implanted in a craniocaudal direction .to enable separate target area from skin points.  In some rare cases, the upper outer quadrant has to be implanted with needles orientated in a 45° angle to avoid overlap of source positions and skin
  66. 66.  2 planes of needles are usually needed to cover the PTV.  A single plane may be sufficient in case of a target thickness of less than 12 mm.  Three planes are required in a large breast where the targeted breast tissue between pectoral fascia and skin is thicker than 30 mm.  Five to nine needles spaced 15–20 mm are usually required.
  67. 67.  Reference needle is first implanted at the posterior (deepest) side into the centre of the PTV.  For definitive positioning, the needle should pass about 5 mm behind the internal scar.  The other needles of the posterior plane are then implanted parallel to the first one.  For definitive positioning, the needle should pass about 5 mm behind the internal scar.  The other needles of the posterior plane are then implanted parallel to the first one.

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