Using Pinnacle 16 Deformable Image registration in a re-treat scenario

Transcription

1 Introduction Using Pinnacle 16 Deformable Image registration in a re-treat scenario This short Hands On exercise will introduce how the Deformable Image Registration (DIR) tools in Pinnacle can be used in a Re-treat workflow. The scenario we will consider is as follows 1. Patient has already received a treatment (in this case a VMAT Head & Neck) at another centre. 2. The patient is now referred for further radiotherapy 3. A new planning CT scan is performed 4. We need to consider the dose from the old treatment in designing the current treatment. The detailed steps in the workflow are 1. The original plan was performed on image Scan1 1. This is Original Plan in the training case. 2. A planning CT has been acquired `Scan2 3. The new planning CT (scan2) is imported Pinnacle as the primary dataset and some contouring has been performed on it. 4. The old planning CT (scan1) has been imported into the same plan as a secondary dataset 5. The DicomRT Dose from the original plan has been sent to Pinnacle 6. The original plans RT Dose is imported onto the original planning CT (scan1) 1. The ability to import RT Dose onto a secondary image was introduced in Pinnacle Deformable Image Registration is performed between scan1 & scan2 8. The resulting Deformation Vector Field (DVF) is applied to the imported dose to propagate it onto the new planning CT (scan2) 9. In the design of the new treatment plan on Scan2 the previous dose can be accounted for. Getting Started Select patient head_and_neck and plan CopyMeToStartExercise Copy this plan Note, in this plan scan2 is the primary image and scan1, the old planning CT, is the secondary Enter Fusion Page 1 of 7

2 Some contouring has already been performed on scan2 Importing the old dose. Select File - Import DICOM and select patient head_and_neck from the list Select the RT Dose from the available messages and select Import Select OK to the following message Page 2 of 7

3 The Record Viewer window will open showing the imported dose. The imported dose is automatically associated with the correct image. In the Evaluation tab in the Record Viewer note that the Dose Type is set to imported Close the record viewer window and the Import DICOM window. Page 3 of 7

4 Creating a Deformation between old and new planning CTs Go to the Deformation tab in Fusion Select Primary Image Modality = CT Filter Images = Yes Smoothing = 1.5 Select Create Deformed Image Note, in this case we are only performing a deformable registration for reasons of brevity. In practice the two images are likely to be more different than in this example so a rigid registration would be performed before the deformable. The initial rigid registration gives the deformable a better starting point. Using the tools introduced in the previous exercise ensure the deformation is acceptable. Approve the Deformation Once approved it will change to the screen shot below Page 4 of 7

5 Propagating the old dose onto the new planning CT Select ctrl P to open the Prescription window Select the dose display mode as Prior Dose Only and Select Manage Prior Dose to open the Prior Dose Manager Under the Include column select Deformed. Rigid is not available as only deformable registration has been approved. Page 5 of 7

6 The previously delivered dose will now propagate to the new planning CT (scan2) and the display will state Prior Dose Only Orange line indicates limit of Deformed Dose The thick orange line is the 1% isodose line (it is 1% of the maximum dose) and is displayed to show the limits of where dose has been propagated to. It can be switched off by switching off display of the dose grid. If dose is required outside of this the dose grid can be redrawn in Planning. Note, that dose will only be propagated where the DVF exists. If a bounding box has been used for the DIR then the dose will only be present inside the bounding box. In the Manage Prior Dose window adjust the scale factor and observe the change in the dose displayed on scan2. This can be used to scale dose from previous treatments to allow for any tissue repair. Note; the scaling of prior dose can be used for tissue repair just for one critical organ. E.g. cord. As not all organs repair by the same percentage. It can also be used if the previous treatment was not completed. Page 6 of 7

7 Note that in the Manage Prior Dose window Selected For Treatment & Clinically Valid have no status as we have used Dose imported from outside Pinnacle. If the Prior dose was generated in Pinnacle then these would be have values. Continue with new treatment plan on scan2 This is the end of this exercise. Now the previous dose has been propagated onto the new planning CT (scan2) it can be accounted for in the design of a new treatment plan. To display the total dose resulting from both treatments the Dose display mode can be set to Current Dose & Prior Dose. In addition, Pinnacle 3 16 adds a new RT Dose export option so that the sum of Current and Prior dose can be exported. Page 7 of 7