Associazione Italiana di Fisica Medica IPOFRAZIONAMENTO E TECNICHE INNOVATIVE Roma, 29 Aprile 2014 Responsabile Scientifico: A.

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1 Ninfa Satariano U.O.C. di Fisica Sanitaria Azienda Ospedaliera di Vicenza In ipofractionation it is necessary to have: High dose to a target Sparing of surrounding normal tissue Cyberknife makes ipofractionation possible using: Small beams with multiple directions Different target tracking systems also for moving target Different dose calculation algorithm (Monte Carlo for lung target) 29/04/2014 Ninfa Satariano U.O.C. di Fisica Sanitaria Ospedale San Bortolo Vicenza 2 1

2 X-ray Sources IMAGING SYSTEM Linear Accelerator ROBOTIC DELIVERY SYSTEM TARGETING SOFTWARE Manipulator Image Detectors 29/04/2014 Ninfa Satariano U.O.C. di Fisica Sanitaria Ospedale San Bortolo Vicenza 3 LINAC: nominal 6 MV; 1000, 800, 600, 400 MU/min, X band 9.5 GHz. 6 degrees of freedom manipulator (Industrial robot KUKA 240, mechanical precision of 0.12 mm). 29/04/2014 Ninfa Satariano U.O.C. di Fisica Sanitaria Ospedale San Bortolo Vicenza 4 2

3 The radiation source can be positioned in a set of points, called nodes, distributes in a spherical surface centered in the virtual isocenter. Each node has 12 different beam orientations. NODES Nodes (130) Path Beams (12 directions) Target 29/04/2014 Ninfa Satariano U.O.C. di Fisica Sanitaria Ospedale San Bortolo Vicenza 5 Non isocentric beams give La possibilità di utilizzare fasci non isocentrici consente di: High conformed dose also for irregular shaped target Reduce dose to the surrounding normal tissue Isocentric Beam Delivery Non-Isocentric Beam Delivery 29/04/2014 Ninfa Satariano U.O.C. di Fisica Sanitaria Ospedale San Bortolo Vicenza 6 3

4 COLLIMATORS 12 fixed collimators with nominal diameters (fwhm at SAD 800 mm): 5,7.5,10,12.5,15,20,25,30,35,40,50,60 mm New IRIS dinamic collimator (same aperturesasthe fixed collimators) IRIS The two tipes of collimators can be exchanged automatically using the Exchange table. 29/04/2014 Ninfa Satariano U.O.C. di Fisica Sanitaria Ospedale San Bortolo Vicenza 7 Treated sites: HEAD & NECK SPINE PROSTATE ABDOMINAL LUNG 29/04/2014 Ninfa Satariano U.O.C. di Fisica Sanitaria Ospedale San Bortolo Vicenza 8 4

5 Each type of target needs a specific tracking method Possible tracking methods for the Cyberknife: SKULL TRACKING FIDUCIAL TRACKING XSIGHT SPINE TRACKING XSIGHT LUNG TRACKING SYNCHRONY RESPIRATORY TRACKING SYSTEM 29/04/2014 Ninfa Satariano U.O.C. di Fisica Sanitaria Ospedale San Bortolo Vicenza 9 SKULL TRACKING Used for target in head and neck, cervical spine (up to C2 or C3) No need for invasive head frame A thermoplastic mask is used to immobilize patient during CT scan and treatment 29/04/2014 Ninfa Satariano U.O.C. di Fisica Sanitaria Ospedale San Bortolo Vicenza 10 5

6 SKULL TRACKING DRR from the treatment plan Xray images from the two x ray tubes of the Cyberknife image system 29/04/2014 Ninfa Satariano U.O.C. di Fisica Sanitaria Ospedale San Bortolo Vicenza 11 SKULL TRACKING To start treatment xray images must be similar to DRR During treatment Cyberknife corrects for residual rototranslations 29/04/2014 Ninfa Satariano U.O.C. di Fisica Sanitaria Ospedale San Bortolo Vicenza 12 6

7 SKULL TRACKING The algorithm for skull tracking is described in the article: 29/04/2014 Ninfa Satariano U.O.C. di Fisica Sanitaria Ospedale San Bortolo Vicenza 13 SKULL TRACKING Roll rotations are determined comparing xray live images with a set of DRR DRR XRAY IMAGES 29/04/2014 Ninfa Satariano U.O.C. di Fisica Sanitaria Ospedale San Bortolo Vicenza 14 7

8 SKULL TRACKING It s a multiphase framework to have a fast algorithm. It starts from gross registration and then use a fine registration 29/04/2014 Ninfa Satariano U.O.C. di Fisica Sanitaria Ospedale San Bortolo Vicenza 15 SKULL TRACKING The image registration is based on the Pattern Intensity similarity measure (PI) 29/04/2014 Ninfa Satariano U.O.C. di Fisica Sanitaria Ospedale San Bortolo Vicenza 16 8

9 SKULL TRACKING DRR XRAY IMAGES Optimized Pattern Intensity for Cyberknife: 29/04/2014 Ninfa Satariano U.O.C. di Fisica Sanitaria Ospedale San Bortolo Vicenza 17 SKULL TRACKING Cyberknife corrects each beam direction to accounts for residual displacement of the patient during treatment CK corrects for: translations up to ±10 mm rotations up to ±1.5 In this example the treatment was stopped because one angle became greater than 1.5. So the patient was repositioned. 29/04/2014 Ninfa Satariano U.O.C. di Fisica Sanitaria Ospedale San Bortolo Vicenza 18 9

10 SKULL CASE 29/04/2014 Ninfa Satariano U.O.C. di Fisica Sanitaria Ospedale San Bortolo Vicenza 19 SKULL CASE In this example the 50 % isodose line is at less than 3 mm from the prescription isodose 29/04/2014 Ninfa Satariano U.O.C. di Fisica Sanitaria Ospedale San Bortolo Vicenza 20 10

11 SPINE TRACKING Used for near spine tumors, but also for targets in lung, abdomen and pelvis when is not possible to use fiducials. DRR As in skull tracking, Roll rotations are calculated comparing xray images with a set of DRR with In the plan is defined a 81 points (nodes)gridonthe spine The tracking algorithm search the same grid on the xray images (live images) Alignment Center 29/04/2014 Ninfa Satariano U.O.C. di Fisica Sanitaria Ospedale San Bortolo Vicenza 21 SPINE TRACKING Calculates global rigid rototraslations around Alignment Center, based on local motion vectors of the grid points. DRR XRAY MOTION VECTORS Image A Image B 29/04/2014 Ninfa Satariano U.O.C. di Fisica Sanitaria Ospedale San Bortolo Vicenza 22 11

12 SPINE TRACKING Also in this case Cyberknife corrects each beam direction to accounts for residual desplacement of the patient during treatment CK corrects for: translations up to ±10 mm rotations up to ±1.5 In this example the treatment was stopped because one angle became greater than 1.5. So the patient was repositioned. 29/04/2014 Ninfa Satariano U.O.C. di Fisica Sanitaria Ospedale San Bortolo Vicenza 23 FIDUCIAL TRACKING Used in soft tissue: liver, renal, pancreas, prostate. In spine targets where Spine tracking is not possible. In lung target where Lung Tracking is not possible Prostate example Guidelines for fiducials for soft tissue: Gold seed (dimentions ~ 0,9 x 3,0 mm) Inside or near the tumor (no more than mm from target Minimum 20 mm spacing between fiducials Minimum 15 angle between the fiducials (non collinear) 4 6 number of fiducials 29/04/2014 Ninfa Satariano U.O.C. di Fisica Sanitaria Ospedale San Bortolo Vicenza 24 12

13 FIDUCIAL TRACKING Alignment center = Fiducials center of mass Conditions for minimization of tracking uncertainties Minimum 20 mm spacing between fiducials Minimum 15 angle between the fiducials (non collinear) 4 6 number of fiducials Minimum of 1 fiducial is needed to track translations Minimum of 3 fiducials are needed to track rotations 29/04/2014 Ninfa Satariano U.O.C. di Fisica Sanitaria Ospedale San Bortolo Vicenza 25 FIDUCIAL TRACKING DRR XRAY Superposition of fiducials Residual corrections In the special case of prostate the threshold for rotations is ± 2, ±5, ± 3 (Roll, Pitch, Jow) as the intrafraction prostate movements can be large 29/04/2014 Ninfa Satariano U.O.C. di Fisica Sanitaria Ospedale San Bortolo Vicenza 26 13

14 FIDUCIAL TRACKING and INTEMPO SYSTEM The quality of tracking depends also from the time interval between two consecutive xray images, This time interval is selected by the user or is automatically adjusted by the software with InTempo System For prostate the is suggested a time below 40 sec To ensure submillimeter tracking accuracy, the imaging frequency can vary between fractions as well as during a fraction in order to accommodate changes in the pattern of prostate motion during treatment. 29/04/2014 Ninfa Satariano U.O.C. di Fisica Sanitaria Ospedale San Bortolo Vicenza 27 SYNCHRONY TRACKING Fiducial Tracking can be associated to Synchrony Respiratory Tracking System The breathing pattern is determined by a set of optical markers placed on the area of greater motion (diaphragm or abdomen) The light emitted from optical markers must be visible to the camera boom 29/04/2014 Ninfa Satariano U.O.C. di Fisica Sanitaria Ospedale San Bortolo Vicenza 28 14

15 SYNCHRONY TRACKING SYNCHRONY USER INTERFACE Breathing pattern waveform from tracking markers 29/04/2014 Ninfa Satariano U.O.C. di Fisica Sanitaria Ospedale San Bortolo Vicenza 29 SYNCHRONY TRACKING The internal motion of the target is determined by the xray images of fiducials In this way a correlation model between external motion and internal motion can be created In general there are 3 types of correlation model: linear and two curvilinear This is an example of linear correlation model 29/04/2014 Ninfa Satariano U.O.C. di Fisica Sanitaria Ospedale San Bortolo Vicenza 30 15

16 SYNCHRONY TRACKING Common target motions: Xorgan r r r Linear model (the most common) Curvilinear model with the target moving in one arc Curvilinear model with the target moving in two arcs 29/04/2014 Ninfa Satariano U.O.C. di Fisica Sanitaria Ospedale San Bortolo Vicenza 31 SYNCHRONY TRACKING The model is created before starting the treatment. During the treatment, xray images are used to check the position of the targhet. If the radial error between the actual position and the modeled position of the target is > 5 mm the erogation is stopped and can be necessary to create a new model. A radial error (correlation error) < 2 mm is optimal. 29/04/2014 Ninfa Satariano U.O.C. di Fisica Sanitaria Ospedale San Bortolo Vicenza 32 16

17 SYNCHRONY TRACKING The source moves with the target The beams erogates in all the breathing cycle More sparing of normal tissue Accuracy of 1.5 mm In this video you can see how the Cyberknife follows the target (fiducials are inside the ball and optical markers are on a moving plate of the phantom) 29/04/2014 Ninfa Satariano U.O.C. di Fisica Sanitaria Ospedale San Bortolo Vicenza 33 XSIGHT LUNG TRACKING Direct soft tissue tracking Does not require implanted fiducials or markers Tracks specific lung tumors o Laterally located o Greater than 15 mm in diameter Seamlessly integrated with the Synchrony Respiratory Tracking System 29/04/2014 Ninfa Satariano U.O.C. di Fisica Sanitaria Ospedale San Bortolo Vicenza 34 17

18 XSIGHT LUNG TRACKING Align Global Patient Position (6D) Using Xsight Spine Tracking System Move Patient from Align Center to Treatment Center Using AutoCouch Track Moving Tumor (3D) Using Direct Tumor Registration Dynamic lung tumor Static spine region Copyright 2008 Accuray,Incorporated. All rights reserved E 29/04/2014 Ninfa Satariano U.O.C. di Fisica Sanitaria Ospedale San Bortolo Vicenza 35 XSIGHT LUNG TRACKING 2D Tumor contour generated in each DRR projection in MultiPlan Treatment Planning System Window created containing tumor contour plus surrounding contrasted background Window utilized as the matching block in tumor registration DRR A DRR B contour window Copyright 2008 Accuray,Incorporated. All rights reserved E 29/04/2014 Ninfa Satariano U.O.C. di Fisica Sanitaria Ospedale San Bortolo Vicenza 36 18

19 XSIGHT LUNG TRACKING DRR Similarity Measure Matching window Maximum similarity LIVE Search window Copyright 2008 Accuray,Incorporated. All rights reserved E 29/04/2014 Ninfa Satariano U.O.C. di Fisica Sanitaria Ospedale San Bortolo Vicenza 37 XSIGHT LUNG TRACKING Non invasive lung radiosurgery Eliminates timely and costly procedure for implanting fiducials No risk of pneumothorax Option for medically in operable patients Option for lung compromised patients (breath holding difficult) Reduces treatment time (gating not optimum for increased treatment time) Maintains Synchrony Respiratory Tracking System accuracy of less than 1.5 mm 29/04/2014 Ninfa Satariano U.O.C. di Fisica Sanitaria Ospedale San Bortolo Vicenza 38 19

20 MONTE CARLO CALCULATION In regions of high inhomogeneities the RAY TRACING fails in dose calculations This is the case in lung tumors Tumors surrounded by a region of lower density (the lung tissue) 29/04/2014 Ninfa Satariano U.O.C. di Fisica Sanitaria Ospedale San Bortolo Vicenza 39 MONTE CARLO CALCULATION Ray Tracing: good coverage but it is not real! Monte Carlo gives the accurate dose distribution: the target is no more covered 29/04/2014 Ninfa Satariano U.O.C. di Fisica Sanitaria Ospedale San Bortolo Vicenza 40 20

21 MONTE CARLO CALCULATION 29/04/2014 Ninfa Satariano U.O.C. di Fisica Sanitaria Ospedale San Bortolo Vicenza 41 MONTE CARLO CALCULATION More complex planning The Monte Carlo Optimization in Multiplan (Cyberknife TPS) is not well implemented, so a reiterative processisused Create a PTV_mc acopyofreal PTV as Ray Tracing optimization Calculate dose with Monte Carlo Decide the best isodose (70% to 80%) IF PTV is well covered end, else continue 29/04/2014 Ninfa Satariano U.O.C. di Fisica Sanitaria Ospedale San Bortolo Vicenza 42 21

22 29/04/2014 Ninfa Satariano U.O.C. di Fisica Sanitaria Ospedale San Bortolo Vicenza 43 MONTE CARLO CALCULATION CK=95% Volume (cc) MC=0.1% Reference dose Dose (cgy) 29/04/2014 Ninfa Satariano U.O.C. di Fisica Sanitaria Ospedale San Bortolo Vicenza 44 22

23 Prostate in Vicenza Tumore primitivo 35Gy 80% 76% in 5 fz Recidiva 30Gy 80% 76% in 5 fz Recidiva 24 Gy 80% 76% in 3fz 29/04/2014 Ninfa Satariano U.O.C. di Fisica Sanitaria Ospedale San Bortolo Vicenza 45 23