The use of radiochromic film in treatment verification of dynamic stereotactic radiosurgery

Abstract

Standard silver-based films are usually too sensitive to be used as direct indicators of dose in dynamic radiosurgery because of optical saturation. This paper describes the use of a new radiochromic film to measure 6-MV radiosurgery doses and dose distributions in a head phantom. Dose calibration of the radiochromic film was performed in the range of 2.3-50.2 Gy using light of 632- and 530-nm wavelengths. Radiosurgery dose distributions were measured using the radiochromic film in a head phantom undergoing the same treatment as a patient, and were compared with the planned distributions. For an example case (nominal 2.0-cm-diam cone), film measurement verified the calculated dose distribution in one plane. The simple measurement technique described led to experimental uncertainties of +/- 0.1 cm for the 90% and 50% isodose lines, +/- 0.3 cm for the 20% line, and +/- 0.5 cm for the 10% line. Isocenter dose was measured with an uncertainty of +/- 3%. Refinements to the technique should allow more precise measurements. It is concluded that the radiochromic film, with some limitations, is a convenient and useful tool for dynamic radiosurgery quality assurance.

A quality assurance method with submillimeter accuracy for stereotactic linear accelerators

“…The Lucy phantom ( 14 , 16 ) from Standard Imaging (Middleton, WI, USA) was used to assess the end‐to‐end accuracy of the SAlinac system. The Lucy phantom was loaded with 2.5 inch by 2.5 inch pieces of GAFCHROMIC film and CT scanned in the Radionics Brown–Robert–Wells (BRW) frame and localizer rods, as is done for patients.…”

“…For convenience, the algorithms could be generalized to process an image from an electronic portal imaging device (EPID) instead of data from the film scanner. ( 12 , 13 ) We began a study with GAFCHROMIC ( 14 ) EBT film (International Specialty Products, Wayne, NJ), but it requires at least 200 to 300 MU to obtain a reasonable image, and the scanned image was not as good as for XV film. For the Winston‐Lutz tests in this study, we exclusively used XV film and 50 MU per shot to first discover the best attainable accuracy with the system.…”

Isocenter verification for linac‐based stereotactic radiation therapy: review of principles and techniques

“…Even in one study with GAFCHROMIC films, up to $\pm 1\hspace{0.17em}\text{mm}$ uncertainty was detected in isocenter positioning. ( 64 ) …”

Qualitätssicherung im stereotaktischen Raum

“…Güte der gesamten Kette (des Systems) (Abbildung 2), zum zweiten Messungen von Outputfaktoren [6,15,33] bzw. Profilen [32] und zum dritten die experimentelle Verifizierung von komplizierten dreidimensionalen Dosisverteilungen [5,13,26]. Es ist von entscheidender Bedeutung, inwieweit berechnete bzw.…”