Shadow Tray Research Articles

Tissue compensators for megavoltage radiotherapy fabricated from hollowed Styrofoam filled with wax.

HomeRadiologyVol. 111, No. 1 PreviousNext ArticlesTissue Compensators for Megavoltage Radiotherapy Fabricated from Hollowed Styrofoam Filled with WaxR. Jerome Boge, Robert W. Edland, David C. Matthes22R. Jerome Boge, Robert W. Edland, David C. Matthes22Author Affiliations Department of Radiation Oncology Gundersen Clinic, Ltd. 1836 South Avenue La Crosse, Wis. 54601R. Jerome BogeRobert W. EdlandDavid C. Matthes22Published Online:Apr 1 1974https://doi.org/10.1148/111.1.193MoreSectionsPDF ToolsImage ViewerAdd to favoritesCiteTrack CitationsPermissionsReprints ShareShare onFacebookTwitterLinked In AbstractA method of tissue compensation for megavoltage radiation therapy is described. A small motor-driven routing tool is made to slide up and down along a bar which pivots from a fixed point simulating the radiation source. As the pointer moves over the patient's surface, the routing tool which is rigidly connected to it cuts a minified surface into a Styrofoam block which is in the position of the shadow tray. The hollowed Styrofoam is filled with wax and the compensator is completed. The wax mold with an appropriate compensating factor of 1.05 produces a uniform dose beneath the patient's surface.Article HistoryAccepted: Nov 1973Published in print: Apr 1974 FiguresReferencesRelatedDetailsCited ByJournal of Mechanics in Medicine and Biology, Vol. 06, No. 03Medical Physics, Vol. 32, No. 5Journal of Mechanics in Medicine and Biology, Vol. 04, No. 03Physics in Medicine and Biology, Vol. 48, No. 1Medical Physics, Vol. 29, No. 10Medical Physics, Vol. 25, No. 4Radiotherapy and Oncology, Vol. 34, No. 1Medical Dosimetry, Vol. 19, No. 4Physics in Medicine and Biology, Vol. 39, No. 12The Journal of Prosthetic Dentistry, Vol. 67, No. 3Medical Dosimetry, Vol. 16, No. 2Medical Dosimetry, Vol. 14, No. 1International Journal of Radiation Oncology*Biology*Physics, Vol. 13, No. 7BibliographyInternational Journal of Radiation Oncology*Biology*Physics, Vol. 6, No. 3International Journal of Radiation Oncology*Biology*Physics, Vol. 5, No. 2A compensation filter for chest portalsInternational Journal of Radiation Oncology*Biology*Physics, Vol. 2, No. 11-12Recommended Articles RSNA Education Exhibits RSNA Case Collection Vol. 111, No. 1 Metrics Altmetric Score PDF download

Radiotherapy compensators fabricated from hollowed styrofoam filled with wax

The method described was developed for use during external beam irradiation of Hodgkin's disease where the field is shaped by the hotwire-styrofoam technique. A small, motor-driven routing tool is made to slide up and down along a bar which pivots from a fixed point which simulates the radiation source. This bar thus follows the diverting path of the photons as does the routing tool. The routing tool is rigidly connected to a pointer which is moved back and forth over the patient's treatment surface, and it thus is able to cut a minified surface into the styrofoam block placed at the position of the shadow tray. The hollowed-out styrofoam is then filled with wax and the compensator is completed.

Effect of shadow trays on surface dose and build-up for megavoltage radiation.

EFFECT OF SHADOW TRAYS ON SURFACE DOSE AND BUILD-UP FOR MEGAVOLTAGE RADIATIONP. S. RAO, PH.D., K. PILLAI, M.S. and E. C. GREGG, PH.D.Audio Available | Share

Male gonadal shielding during cobalt teletherapy.

A male gonadal shield for use in cobalt teletherapy of the pelvic area is described. Reduction of the dose to the gonads by lead blocks placed on a shadow tray is enhanced another 50% by the use of a simple scatter shield.

Effect of shadow trays on dose to superficial layers of skin in 6 MV X-ray therapy

It is common practice to attach plastic shadow trays to the collimating heads of megavoltage teletherapy units for holding lead shielding blocks. The presence of the trays leads to some electron contamination in the beam and to consequent increase in the skin dose. Using lithium fluoride and thin sheets of Lucite, the authors have measured actual doses at the surface and at depths of up to 25 mm in a Lucite phantom for 6 MV X-rays, both with and without a shadow tray. As expected, the increase in dose due to the tray depends on the field size. For example, for a field of 25*25 cm at an SSD of 100 cm, the tray (at a distance of 30 cm from the surface) increases the surface dose from 37 to 53% of the maximum dose, and the dose at a depth of 1 mm from 50 to 75%. The depth for an 80% dose changes from 2.6 to 1.4 mm. For a field of 5*5 cm, the changes are negligible. That the changes are due to electrons is very simply demonstrated by introducing a thin lead sheet under the shadow tray, when the doses return to their pre-tray levels. These results and their implications for skin-sparing effects were fully discussed.