E. Mezzenga 1, E. Cagni 1, A. Botti 1, M. Orlandi 1, W.D. Renner 2, M. Iori 1 1. Medical Physics Unit, ASMN-IRCCS of Reggio Emilia, Italy 2. MathResolution LLC, Columbia, MD, USA Physics General Session Thursday, October 10 th, 2013

Patient-specific treatment plan workflow Tomotherapy Hi-ART treatment system (Accuray Inc., Madison, WI, USA Plan verification on a phantom: patient-specific pre-treatment plan Plan delivered on patient (daily treatment plan) Plan optimization on a dedicated Treatment Planning System (TPS) Patient Computed Tomography with contoured target(s) and organ(s) at risk imported into TPS Plan optimization (based on target(s) dose coverage and organ(s) at risk constraint(s))

Patient Computed Tomography with contoured target(s) and organ(s) at risk imported into TPS Starting point Computed Tomography (CT) used for patient set up Treatment Planning System (TPS) Plan optimization Beam energy, geometry, shape profile, machine components Patient-specific treatment plan

The goal of a patient-specific treatment plan Treatment plan Delivering the correct dose to the patient Patient set up Machine (energy, field shape, radiation ammount) Treatment verification (daily verified before each treatment session) (periodically verified on the basis of international reports) Be sure that the TPS dose and that delivered by the treatment unit be as close as possible!!! Dosimetric verification on a phantom

Beam fluences Pre-treatment plan Patient-specific Tomotherapy treatment plan projections recalculated on phantom 3D dose distribution 2D dose distribution computed on a phantom-detector combined system Planning CT Patient specific 2D pre-treatment plan verification a)TPS dose distribution b)Mesured dose distribution c)Gamma index evaluation*, on the basis of 3% dose difference (  D M ) and 3mm distance to agreement (  d M ) * Low DA et al., Med. Phys Stating point a) b) c) Detector: seven29 (PTW, Freiburg, Germany)

Pre-Treatment dosimetry Improvement: both dosimetric evaluations rely on data collected from Tomotherapy’s MVCT detectors!!! Patient specific 3D plan verification: the DOSIMETRY CHECK TM software...still before treatment, but without phantom! Transit dosimetry …during treatment, but with daily patient anatomy! New: Transversal section of the Tomotherapy MVCT detector number of detectors : 640 radius of detector : 98.6cm spacing of detectors along arc: 0.118cm Tungsten septal plates

Delivered fluence Radiological pathway Dose computed by projection Beam fluences D OSIMETRIC OPTIONS : PRE - TREATMENT 2D/3D IN VIVO 2D/3D Treatment plan (pre-treatment or transit) Patient CT 3D di dose distribution DICOM-CT DICOM-RS DICOM-CT DICOM-RS DICOM-RP DICOM-RD pre-treatment or transit sinogram How does it work?

Detector signal Intensity (a.u.) Normalized detector signal Detector signal (pulse/MeV cm 2 ) Calibration signal (a.u.) Beam profile measurements % dose (a.u.) Depth in water (cm)Transversal couch direction(cm)Longitudinal couch direction (cm) DOSIMETRY CHECK TM : porting phase Tangent angle Detector channel

DOSIMETRY CHECK TM : fine tuning phase Gaussian monoenergatic dose kernel Minimizing the difference between measured and computed Percent Depth Dose (PDD) Modelling New photonic spectra Polyenergetic dose kernel (not gaussian) YES NO

The DOSIMETRY CHECK TM calibration Virtual water phantom (“Cheese” phantom) TPS (blue) and DC (green) dose distribution comparison obtained in a pre-treatment validation a) b) c) a): TPS dose distribution. b): DC dose distribution; c): gamma analysis 93.9% agreement

Seven29 (a) vs DC (b) dose distribution. c) gamma analysis. (simulation of in-vivo dosimetry for the pelvis anatomical region) The DOSIMETRY CHECK TM validation a) b) c) 90.1% agreement Transverse view of the phantom-detector system with the TPS dose distribution Seven29 (PTW, Freiburg, Germany) detector Octaviu II with Seven29 detector inserted

Sagittal viewCoronal viewTransverse view Line profiles (dotted TPS, continuous DOSIMETRY CHECK) along the dotted yellow line in the corresponding upper view. In-vivo dosimetry of brain plan

Sagittal viewCoronal view Transverse view Line profiles (dotted TPS, continuous DOSIMETRY CHECK) along the dotted yellow line in the corresponding upper view. In-vivo dosimetry of prostate plan

Sagittal viewCoronal view Transverse view Line profiles (dotted TPS, continuous DOSIMETRY CHECK) along the dotted yellow line in the corresponding upper view. In-vivo dosimetry of head&neck plan

Sagittal view Coronal view Transverse view Line profiles (dotted TPS, continuous DOSIMETRY CHECK) along the dotted yellow line in the corresponding upper view. In-vivo dosimetry of thorax plan

Conclusions… Time computation (depending on the voxel dimension and plan modulation) Transit Pros: Can be done on a daily basis Provides both Gamma and DVH analysis Catch change in patient anatomy/setup Cons: Pencil beam dose calculation Transit calculation does not correct for scatter, only attenuation. Susceptible to error from patient geometry or setup. Pre-Treatment Pros: No heavy phantoms Less set-up time Provides both Gamma and DVH analysis Cons: Pencil beam dose calculation Implementation in clinical routine (time computation to be reduced!!!); Impact on daily dose delivered in relation to the patient anatomical variation. …& future work

Acknowledgments E. Cagni, A. Botti, M. Orlandi, M. Iori Medical Physics Unit, ASMN-IRCCS of Reggio Emilia, Italy W.D. Renner MathResolution LLC, Columbia, MD, USA A. Peroni, D. Raspanti, L.Valli TemaSinergie spa, Faenza, Italy

Thanks! QUESTIONS?