For SBU Dosimetry Program 2017-2018.
- Transfer the CT images to the treatment planning system (TPS) and verify that the patient information and the number of slices are accurate.
- Rename the CT and structure set appropriately.
- The CT and structure set should be named based on the site of treatment and the date that the treatment CT took place; e.g. RT BREAST 11_20_17.
- Set the user origin to the coincident location where the AP and lateral BBs intersect unless the user origin was manually set by the physician at the CT simulation. This is the point at which the therapists will align the patient to prior to making isocenter shifts as used in the plan.
- Import the appropriate plan template according to the treatment machine and technique to be used for the treatment. Using the template will automatically insert fields and setup fields with the correct specifications (Verify room geometry).
- Rename the plan based on the treatment site; e.g. RT BREAST.
- Fuse any ancillary images (PET/MRI/previous CT) to the current treatment CT scan that is requested by the physician.
- Import the appropriate structure set template for the treatment site, and delete structures that will be unused for the plan.
- Create two reference points that are attached to the treatment volume structure:
- e.g. RT BREAST – delete this reference point from the image only, and, in the prescription tab, set it to be the primary reference point, which will tracks how much dose the patient has received from daily treatment.
- e.g. RC_RT BREAST – the RadCalc point to be used to calculate the plan. In a 3D plan, it can be used to be a point to prescribe dose to in Plan Normalization. In IMRT/VMAT plans, this reference point is strictly for RadCalc use.
- Create all the fields that will be used in this treatment.
- Try to use gantry, couch, and collimator rotations of whole numbers, ideally in increments of 5.
- Avoid X/Y/Z shifts if doing so offers no significant dosimetric advantage. If shifts are used, round to a whole number or to the tenths decimal place unless extreme precision is required; e.g. SRS.
- Apply and/or verify the appropriate beam parameters (e.g. name, energy, dose rate, beam tolerance), geometry, and room geometry.
- The ID and Name will be identical and are written based on the total number of beams in all courses, the gantry angle, the orientation, and/or the direction of arc:
- 3D Plan: 01 RT LAT, 02 RT MED, 03 RAO, 04 LAO, 05 AP, 06 PA.
- Static Field: 01 G60, 02 G120, 03 G150.
- VMAT Arcs: 01 RA CCW, 02 RA CW, 03 RA CCW.
- Arrange the fields in CCW order to minimize patient time on the table.
- Dose Rate should be 400 MU/min for 3D plans, 600 MU/min for most static IMRT plans, 600 MU/min for VMAT, 1400 MU/min for 6X FFF, and 2400 MU/min for 10X FFF.
- Tolerance should be CL21EX for photons, 21EX ELC for electrons, or SRS_SRT_SBRT for SRS/SRT/SBRT.
- Set the Room Geometry to the following specifications: Couch Vrt at 0, Couch Lng at +100, Couch Lat at 0, Imager Vrt at +50, Imager Lng at 0, and Imager Lat at 0.
- For an electron plan, the SSD of the field should be 100 CM or greater in increments of 5 CM (105 CM, 110 CM, etc.):
- Set block properties to “eTray” and “Aperture”.
- Remember to print the block out in the BEV at 95 CM.
- Check for any possible collision issues for all fields.
- The ID and Name will be identical and are written based on the total number of beams in all courses, the gantry angle, the orientation, and/or the direction of arc:
- Create setup fields based on what is necessary for the treatment machine. Though a 3D plan template on the SIL calls for 9 setup fields (CBCT, kV AP/LATs/PA, MV AP/LATs/PA), a prone breast plan will require you to add only one kV PA setup field.
- MV setup fields will have a tolerance of CL21EX.
- kV and CBCT setup fields will have a tolerance of OBI.
- Attach a digitally reconstructed image (DRR) to every field according to the treatment area.
- Input the correct dose prescription (verify that the dose/fraction and fractions are not mixed up).
- If field-in-field technique is utilized, merge the subfields into a new plan. Name the new plan to be the treatment area, and rename the old plan to “subfields”.
- Re-add DRRs to all the fields of the new plan.
- Re-normalize the new plan to the original intended normalization (now renamed to “subfields”).
- Export the plan to RadCalc.
- 3D plan: Do not include setup fields or structure set.
- Verify beam specifications (SSD/bolus/RC point/etc.).
- Adjust the equivalent path and SSD under the “Points & Off Axis Assistance” tab. These values are found in the plan by going to Print -> Report -> Stony Brook Short Summary> Preview.
- Dose difference must be within 3% for 3D plans, or 5% for field-in-field & EDW & electron technique plans, or 1% of the fractional dose for either type of plan.
- IMRT/VMAT plan: Include the structure set but not the setup fields.
- Verify beam specifications (SSD/bolus/RC point/etc).
- Calculate.
- Dose difference must be within 5% or 1% of the fractional dose difference for all fields.
- Go to the “MLC Data” tab -> Volume Average Dose -> Select the number closest to 0%.
