Radiation Protection in Radiotherapy

Transcription

1 Radiation Protection in Radiotherapy Albert Lisbona Medical Physics Department CLCC Nantes Atlantique Saint-Herblain France

2 Radiation therapy The lecture is oriented to the patient optimisation radiation therapy treatment : Intensity Modulated Radiation Therapy (IMRT) Head and Neck, prostate, Respiratory gated radiotherapy Image Guided Radiation Therapy (IGRT) which is not a treatment technique but an imaging technique used for patient setup

3 External Radiotherapy Dose variations between 5 to 10% to the target volume can lead to a significant change in the local tumor control and/or in the toxicity Random errors Human factor Systematic errors Network, TPS, beam calibration,...

4 IMRT medical Justification Centre de Lutte Contre le Cancer Medical justification : IMRT two objectives : Dose limitation to OAR to decrease toxicity, Dose escalation to target to increase local control Dose limitation to : Spinal cord, Parotids (to preserve salivary function) Rectal wall and bladder wall

5 IMRT IMRT : to modulate static or rotational xray beams in order to get a better target coverage AND a good healthy tissue sparing Prostate cancer rectum, bladder, H&N cancer parotids, cord, oral cavity.

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7 3D CRT Qualitative and quantitative evaluation IMRT

8 Qualitative and quantitative evaluation 3D CRT IMRT

9 Qualitative evaluation 3D CRT IMRT

10 Quantitative evaluation 3D CRT IMRT

11 3DCRT 4 beams 90

12 3DCRT 5 beams 72

13 5 beams 72 + IMRT

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16 Respiratory gated radiotherapy

17 Respiratory gated radiotherapy Justification Problems with 3D CRT or IMRT How to reduce radiation field size to protect closed healthy tissue? Limitation : lack of precise data on organs movements => empirical margins from 1.5 cm à 2 cm Main organs concerned by respiration Chest : lungs, heart, esophagus, diaphragm, mediastinum, breasts Abdomen : liver, kidneys, pancreas, spleen

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19 Centre de Lutte Contre Tumor le Cancer position variation during respiratory cycle Right lung dilatation variation M. Ayadi CLCC Lyon

20 M. Ayadi CLCC Lyon

21 Dose distribution calculated from Internal Target Volume defined on CT ITV superposition obtained from a 4D CT showing => Under coverage of 4DITV M. Ayadi CLCC Lyon

22 "Respiratory" lung showing the superposition of calculated isodoses lines from a 3DCRT on an "averaged" 4DCT M. Ayadi CLCC Lyon

23 IGRT IGRT is an advanced technique (using imaging devices) that allows radiation to be delivered to tumors with more precision than is traditionally possible.

24 IGRT If we can : Improve, patient setup (reproducibility), Reduce uncertainties on patient movements (intra, interfractions), Reduce uncertainties on target movements (intra, interfractions). So we could : Reduce margins around targets used to take into account movement, Obtain a possible strategy to adapt to target modifications, or to the patient, Obtain the opportunity to increase dose.

25 Imaging techniques for IGRT Centre de Lutte Contre le Cancer Electronic Portal Imaging Device : Portal images of radiation patient fields Implanted fiducials (gold seeds) Stereoscopic kv imaging Cone Beam Computed Tomography (CBCT) kv MV Echography CT Scanner in linac vault MVCT Tomotherapy

26 Cone Beam Computed Tomography Centre de Lutte Contre le Cancer Setup Adjustment Patient alig Reconstruction Acquisition

27 CBCT Centre de Lutte Contre le Cancer Example : prostate CT slices CBCT slices

28 CBCT Reconstruction Skull Centre de Lutte Contre le Cancer H&N Lung Bladder Spine

29 Conclusion Optimisation in radiotherapy for patient can be apply : To reduce target margins, To increase (or at least to keep) dose to the targets, To reduce dose to healthy tissues (organs). From medical community we need more evaluation studies : tumor control, treatment complication rates, and patient survival. Adequate staff, and sufficient training for all the members of the team involved. Guidance, recommendation on quality assurance for new techniques.

30 GRACIAS THANK YOU