2D, 3D, VMAT and electron planning done for IMN field considering all aspects, including PTV coverage, dose homogeneity, OAR doses, Electron for IMN was the best

1. Planning Meet
24 Jan 2019

2. To discuss the techniques of IMN irradiation
• 2D planning on Cobalt
• 3D Conformal Radiotherapy
• VMAT
• electrons

3. • Mrs X, diagnosed with ca Lt Breast, Post Neoadjuvant chemotherapy,
Post TMAC pT2N3M0 being planned for radiotherapy to Lt Chest wall
and drainage area
• Drainage : Axilla + SCF + IMN

4. 2D Planning
Simulator : lied down on couch with head first position
Positioning : Breast Board, head turned to opposite side, lt arm
abducted and rt arm straight by side of body
Breast Board Parameters
E : 4
H : D
A : 20
W : 3

5. • Gantry at 0, arbitrary field opened, Borders for IMN was set
• Upper border : superior aspect of medial 1st rib
• Cranial border at the end of 4th rib
• Lateral borders : 3 cm on each side from the mid line, and markings done
• Chest wall field :
• the medial border matching with the lt lateral border of IMN field
• Lateral border : at the mid axillary line, radio-opaque marker placed
• Superior border matched with the superior border of IMN
• Inferior border : 2 cm below the infra-mammary fold of C/L breast

6. • Gantry rotated arbitrarily to 3200 and image taken, the centre of the
Beam Eye View was matched with the lateral field
• Looked for Chest wall coverage : adequate and CLD : 2
• Borders marked after rotating gantry to 00
• But, at the angle of 3200 there was gap of around 1 cm between the
lateral border of IMN and medial border of Chest wall
• This was due to different directions of the IMN field and CW field
and it could be the potential “cold spot”

7. • Since this region lies in the chest wall region where cold spot could
eventually lead to under dosing and recurrence of disease.
• To avoid this cold spot, we give arbitrarily 150 tilt to IMN field to
opposite side, such that IMN field could be somewhat paralled to
Chest wall tangential fields.
• Dose of IMN prescribed at 4 cm depth based on the anatomical
knowledge of IMN location.

8. 3D Conformal RT
• The depth at which we prescribe IMN dose varies from patient to
patient so, if imaging done, this could be better irradiated after
measuring the depth of IMN
• Appropriate energy of machine could be selected
• Planning CT taken in exactly same position in which patient was
simulated for 2D planning

9. • Contouring
• IMN :
• superior aspect of medial 1st rib
• Inferior : cranial aspect of 4th rib
• Medial, lateral, anterior and posterior borders : followed the
thoracic bundle and contoured the space

10. Chest wall, IMN, B/L lungs, Heart

11. IMN field : direct incident with tilt

12. IMN + CW : dose covered by 95% Isodose

13. 3DCRT Heart Dose

14. 3DCRT Lung Dose

15. VMAT Planning

16. VMAT Heart Dose

17. VMAT Lung dose

18. IMN with direct incident Electron field

19. Selection of appropriate Electron Energy
Electron Energy IMN @ 3cm depth Heart @ 5 cm depth Spine at 13 cm depth
6 MeV 6%
(90% : 17 mm)
1.5% 0
9 MeV 83%
(90% : 27 mm)
Skin : 80%
10 % 0
12 MeV 99.8%
(Skin : 87% )
48% 00

20. 2D 3DCRT VMAT Electron IMN
+ CW Photon
Coverage IMN : 90-85 %
Cold spot/hot
spot at jxn of
IMN and CW
Spillage +
Hot spot :
115%
High
conformity
index
No spillage
Hot spot :
109%
90-85 %
Heart 80-50% V30 : 40% V25 : 14% 6 %
Lung CLD = 2 V20 : 47%
V40 : ???
V30 : 30% Very less,
negligile