Instructions for SRS Quality Audit SystemPage 1/5

INSTRUCTIONS FOR SRS QUALITY AUDIT SYSTEM

Enclosed is a head phantom with two inserts; an imaging insert containing the "tumor," and a dosimetry insert containing film and TLD. The purpose of the phantom is to verify dose and dose distribution, as well as localization of the dose relative to a simulated “tumor."

The imaging insert contains a nylon sphere suspended in water as the target volume (tumor). The dosimetry insert contains two orthogonal sheets of GAF chromic film passing through the center of the target and two TLD within 0.5 cm of the center of the target (see the figure).

In order to assure optimum precision of our evaluation, the following constraints should be observed in planning the treatment:

  • The maximum dose to the film should be at least 30 Gy.
  • The dose to the TLD (at the center of the target) should be approximately 30 Gy.

Our report to you will include the following:

  • The dose at the center of the target (nylon ball) measured by TLD.
  • Dose profiles in three plans measured by film.
  • Field size at the prescription isodose line in three dimensions measured by film.
  • Location of the prescription dose relative to the target center.
  • Treatment volume related to target volume, and minimum dose to the target.

Image, plan, and treat this phantom as if it were a real patient (according to the RTOG Quality Assurance Guidelines), and send us enough of the documentation so we can tell what you have done. Please follow the enclosed instructions and return as soon as possible.

The phantom has been shipped to you with the following:

  1. Anthropomorphic Phantom Shell
  1. Imaging Insert
  2. Dosimetry Insert
  3. Drain Plug Tool (blue)
  4. Securing plate

RETURN SHIPPING INSTRUCTIONS

Please return the phantom using the enclosed prepaid mailing label.

Please email the IROC Houston ()to let us know when you are going to irradiate the phantom(exactly day); we will irradiate standards to meet your schedule. For technical questions and questions regarding the return shipment contact Nadia Hernandez or Andrea Molineu. Phone: (713)7458989 Fax: (713)794-1364

Procedures:

Imaging:

  1. Remove the large white filler plug on the head phantom, using the enclosed blue tool if necessary, and the small red thumbscrew, which is a vent plug. Fill the phantom with water, rotating the phantom to minimize the amount of trapped air. It will be necessary to overfill the head to ensure that it is full. Check for excessive air and add more water if necessary. When the phantom is filled, first secure the large white plug, then the small red thumbscrew on the vent hole.
  2. Remove the small white bolt in the center of the Imaging Insert and fill the insert with water, minimizing the amount of trapped air, also by overfilling. Replace the bolt, ensuring black ring is in place. Hand tightening should be enough.
  3. Ensure that all bolts and plugs are tight and not leaking. Use the blue tool to tighten the large filler plug if necessary. Dry off all excess water from the phantom and insert. Be sure to dry the surfaces of the insert receptacle.
  4. Insert the imaging insert into the neck of the phantom. The flat side, with no writing on it, should be inserted into the phantom first. Press in very slowly, allowing air to escape. The approximate position is obtained by aligning the thick yellow lines on the phantom and the insert.
  5. Attach the securing plate over the imaging insert using the two green screws provided. Notice the red line on one side of the securing plate. There is an alignment pin between the insert and the securing plate; you may have to rotate the insert in order to attach the securing plate.
  6. If you use a headframe, position it on the phantom. The target is located roughly between the upper parts of the ears. The dose profiles will be in the sagittal and coronal planes of the phantom; mount the headframe so that these planes correspond with the dose plane produced by your treatment planning system. If possible have your physician participate in the mounting of the frame.
  7. Locate the target with either CT or MRI, whichever is most frequently used for protocol patients. Please provide scout and axial images if CT imaged, sagittal and coronal or axial images if MRI imaged.
  8. Remove the two green screws, which hold the securing plate.
  9. Remove the Imaging Insert. It will come out very slowly due to the tight fit.
  10. Planning:
  11. The target is the nylon ball that should be evident in either the CT or the MRI scans. The center of the ball defines the center of the target volume. Since contrast is excellent GTV=CTV, PTV should only be a function of your usual setup margins
  12. Plan a treatment using the smallest single field that will cover the target volume with the dose distribution centered on the nylon ball delivering approximately 30 Gy to the center of the target and at least 15 Gy to the prescription line (see constraints in the introduction). Remember the RTOG QA guidelines require the prescription line to be no higher than 85%. It should be between 50-80%.
  13. Treatment:
  14. Insert the Dosimetry Insert (white plastic). The dosimetry insert should be placed in the phantom with the white section first so that the writing is visible. Press in very slowly, allowing air to escape. The approximate position is obtained by aligning the thick yellow lines on the phantom and the insert.
  15. Attach the securing plate over the imaging insert using the two green screws provided. Notice the red line on one side of the securing plate. There is an alignment pin between the insert and the securing plate; you may have to rotate the insert in order to attach the securing pate.
  16. Irradiate the phantom according to your plan.
  17. Remove the dosimetry insert. Lift the insert out first
  18. Fill out the data sheet.
  19. Drain the water from the phantom.
  20. Drain the Imaging Insert.
  21. Wipe excess water off all surfaces of the phantom.
  22. Pack and return all items. Please include copies of treatment plans and diagnostic images used to plan the treatment.
  23. Have a nice day.

Stereotactic Radiosurgery Quality Audit Data Form

Institution:______

Address:______

______

______

Person performing irradiation:______

Person to receive report:______

Person to call in case of questions:______

Phone Number:______Email address: ______Fax Number:______

Treatment Unit (Linear Accelerator or Gamma Knife):

Manufacturer:______Model:______

In-house specification:______

If linac:

Photon Energy:______Ionization Ratio (TMR 20/TMR 10):______

Collimator (if appropriate):______

Stereotactic System (if modification to linac):______

Manufacturer:______Model:______

Please enclose original copies of your treatment plans.

If gamma knife:

Collimators plugged (if any):______

For Office Use Only / Batch / Phantom ID # / Code / Date Sent / Date Rec'd

Immobilization System (Head frame):

Manufacturer:______Model:______

Treatment Planning System:

Treatment Planning System: ______

Software:______Version Number:______

Treatment of Phantom:

Date of Irradiation:______

Dose in:_ Muscle _Water

(Note: Several of the following may be the same.)

Maximum dose:______Gy

Isodose line this represents:______%

Dose to center of the target:______Gy

Isodose line this represents:______%

Prescription dose:______Gy

Isodose line this represents:______%. Should be between 50-80%

Minimum dose to target:_____Gy

Isodose line this represents:______%

Diameter of treatment volume (identified by prescription isodose line) along: (Required). Determined from your treatment planing system.

Right/Left Profile:______

Anterior/Posterior Profile:______

Superior/Inferior Profile:______

If you are doing this phantom to credential for NCCTG protocol N-0574, please fill out the Facility Questionnaire, you can find it on the IROC Houston website, Look under credentialing on the top menu, and click on NCCTG tab, protocol N-0574.

Comments:______