Published on February 28, 2018
1. 4D-CBCT (Symmetry) – a useful tool to verify and treat traditional ITV without 4D-CT simulation in treatment of lung cancer. Dr. Malhar Patel DNB (Radiation Oncology)
2. Introduction • Challenges in modern radiotherapy. • What to do about it??? Image guidance EPID 4D-CBCT (Symmetry)
3. Ling et al defined IGRT more broadly as ―the use of imaging for detection and Diagnosis, Delineation of target and organs at risk (OARs), Determining biological attributes, Dose distribution design, Dose delivery assurance, and Deciphering treatment response, a so-‖ called six-dimensional definition. 6D Definition
4. Lung Tumour Motion While Free Breathing Motion Artifact
5. AAMP: American Association of Physicists in Medicine AAPM TG-76 (Report 91) • Accounting for Respiratory Motion • Motion-encompassing methods (Free Breathing) • Respiratory Gating Techniques • Breath-hold Techniques • Forced shallow breathing - abdominal compression • Real-time tumor-tracking The Management of Respiratory Motion in Radiation Oncology SUPERIOR - INFERIOR ANTERIOR – POSTERIOR LEFT - RIGHT 0 – 18.5 mm 0 – 9.5 mm 0 – 10 mm
6. CONCLUSIONS: Systematic and random baseline variations constitute a substantial portion of the geometric variability present in the treatment of patients with lung cancer and require generous safety margins when relying on accurate setup/immobilization or bony anatomy-driven correction strategies. The 4D-CBCT has the ability to accurately monitor tumor trajectory shape and baseline variations and drive image-guided correction strategies that allows safe margin reduction. Int J Radiat Oncol Biol Phys. 2008 Feb 1;70(2):590-8. Epub 2007 Nov 26
7. Immobilization Combination of Thermoplastic Mask and Vac Lock For Thorax Region.
8. Patient preparation Instruct patient to breathe in 3 phase Normal Breathing Deep Inspiration Deep Expiration You Have 4D CT SCAN??
9. CT Simulation Whole Thorax region 3 phase respiration CT Slice thickness 3mm Patient aligned to the fiducials & laser marks IV contrast to enhance target & critical organs DICOM images transferred through networking FiducialFiducial
10. GTV: Gross Tumour Volume CTV: Clinical Target Volume ITV: Internal Target Volume PTV: Planning Target Volume ITV = CTV + IM (Internal Margin) PTV = ITV + SM (Setup Margin)
11. Contouring GT V
12. XVI Imaging and 4D Symmetry Pre-RT evaluation. Daily XVI Imaging was done. 4D CBCT (Symmetry) First Day and repeated weekly.
13. 4D (Symmetry) Pre RT Evaluation
14. 4D (Symmetry) After 20 #
15. Results • The defined ITV margin is adequate to cover the moving target in free respiratory cycle. • 30 4D-CBCT • 130 XVI (CBCT) Organ Motion Longitudinal (Superior-Inferior) Vertical (Anterior-Posterior) Lateral (Left Right) 4.9 mm 2.56 mm 1.89 mm SUPERIOR - INFERIOR ANTERIOR – POSTERIOR LEFT - RIGHT 0 – 18.5 mm 0 – 9.5 mm 0 – 10 mm AAMP
16. Setup Errors Transitional Setup Error Lateral Longitudinal Vertical Mean (cm) 0.1165 -0.1055 -0.187 standard deviation (SD) 0.066447 0.324877 0.093529
17. Conclusion • Accuracy • Precision • Verification FUTURE???