1) 4DCT exams using the VisionRT system and Toshiba scanner provide 10 respiratory phase datasets but require long reconstruction times of over 5 hours. 2) There are issues with mismatches between the breathing signal and images due to factors like couch acceleration and different velocities reported by VisionRT and Toshiba. 3) Proper definition of monitoring points, respiratory thresholds, and image reconstruction parameters like slice thickness are important to reduce artifacts but more investigation is needed on their effects.

1. LA TC - 4D CON SISTEMI DI TRACKING OTTICO DI SUPERFICIE G.Guidi, L.Binotti, L.Morini, E.Cenacchi, T.Costi Medical Physics Dpt. M.Amadori, P.Antognoni, M.Parmiggiani, P.Giacobazzi, G.Tolento, F.Bertoni U.O. Radiation Oncology Azienda Ospedaliero - Universitaria di Modena - Policlinico Gabriele Guidi Medical Physics Dpt. Az.Ospedaliero-Universitaria di Modena Email: [email_address] Phone: +39 059 422 5699 – ext. 4270

2. 4DCT AND GATING/TRACKING DEVICES (TOSHIBA + VISION RT) Advantages: 4DCT Exams (10 CT Dataset – 0-100% Breathing Phases): Very Fast (few minutes) – Retrospective Mode Range Slice thickness for our RT: 0.5 - 3 mm (5mm used for Cranio Spinal Irradiation and TBI) VisionRT detect capability: 1mm of the couch movement (VisionRT can appreciate the ramp up of the couch during the CT scan) Issues: 4DCT Images Reconstruction (>1000 Images – 10 CT Datasets – 5/6 Hours of reconstruction) Thickness 0.5mm could be useful for Radiosurgery but few dose problem must be considered during the planning calculation Troubles and investigation: Mismatch image reconstruction due to the couch ramp-up and the breathing signal (Sinogramma Editing in develop by Toshiba) Trick Necessary

3. HELICAL PITCH AND COUCH VELOCITY (RAMP EFFECT) May be in some other CT the ramp is inside the scan packet and you could not be able to see the effect of the ramp up during the image reconstruction or have “invisible” effect on the images ...Why do I have a different velocity between VisionRT and Toshiba? CT Ramp (Couch Acceleration) Scan Dimension (Constant Velocity)

5. RESPIRATORY SIGNAL REPEATABLE (PHANTOM TESTS) Respiratory signal seems to be perfect and repeatable

6. TOSHIBA HELICAL PITCH BIAS .... VISIONRT MONITORING BIAS (PATIENTS) Exams Setup Parameters: one decimals Internal Machine Parameters: two decimals Monitoring Point Calculation VisionRT Couch Velocity= Thickness*HP/Rot Time One decimal or two decimal could have a big effect on the monitoring point determination

7. VISIONRT VS. TOSHIBA BREATHING SIGNAL RAW DATA Cough: rejected by the reconstruction Mean respiration time Which is the impact of the respiration time on the image reconstructions? ...I don’t know at the moment....

8. TOSHIBA EDIT DATA TOOLS ... THRESHOLD EFFECTS Raw data Post Process data Resample with different breathing Threshold Spike adjustments Perfect Breathing (post-processing) Resample of the breathing 3 different results – Same Images?????? (I do not believe...) Game: Try to find the differences

9. FREE BREATHING VS. THERMOPLASTIC MASK (PATIENTS) Immagini CT con e senza maschera Video immagine assiale lesione Very similar but the thermoplastic mask seams to help the patients to breathing correctly

11. Coordinate Variation ... Which phases? The best reconstruction.... Phases 20% - 60% seams the most repeatable

13. PATIENTS AT MODENA .... (4 PATIENTS DONE!! BUT MANY QUESTIONS TO SHARE....)

14. 4D TOMOTHERAPY DOSE RECONSTRUCTION 4D DOSE RECONSTRUCTION OF THE RESPIRATORY PHASES (Possible!!! But I will be crazy, if it will be a clinical routine (3 days of work)) ... Some open issue about the deformation Dose Matrix (Phase 20%) + Dose Matrix (Phase 30%) + Dose Matrix (Phase 40%) + Dose Matrix (Phase 50%) + Dose Matrix (Phase 60%) + ------------------------------------ 4D Dose Reconstruction

15. Proton-Therapy..... Few questions in my mind.....may be I need to change my mind!!! ...are we sure about the dose calculation? ...we will try to investigate the problems with the mesothelioma group (BRMOTRFI)

16. ... Someone better than us...