SU-E-T-431: Vertically-Oriented Farmer-Type Chamber for Small-Field Applications

Ahmad, M; Chu, A; Lincoln, H; Chen, Z; Deng, J; Nath, R

doi:10.1118/1.4888764

Title: SU-E-T-431: Vertically-Oriented Farmer-Type Chamber for Small-Field Applications

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Abstract

Purpose: To introduce a non-conventional measurement setup using Farmer-type chambers to accommodate several situations of small-field dose measurements without compromising accuracy. The validation of this technique was demonstrated for photon small-field output measurements, and electron small-field percentage depth-dose (PDD) measurements. Methods: Initial chamber alignment was performed using the conventional (horizontally-oriented) chamber setup. A PDD was acquired for a 4×4 cm{sup 2} field size using this arrangement. This PDD was used as a positional reference for the vertically-oriented chamber (VOC) configuration. Next, a PDD was acquired for a 4×4 cm{sup 2} field size with the VOC. The PDD's were superimposed to find the effective shift of the VOC. Using the shifted VOC setup, photon small-field output factors were measured and compared to stereotactic diode output factor measurements. Additionally, electron smallfield PDD's were acquired using the VOC setup and results were compared to electron Monte Carlo (eMC) predictions in the Eclipse treatment planning system (TPS). Results: (1) For photon small-field output factors field-sizes 2×2 cm{sup 2} and larger, the difference between the VOC setup and SFD measurements were less than 0.8%. For field sizes less than 2×2 cm{sup 2} discrepancies ranged from 4.0 to 10.6%. (2) PDD's measured by VOC setup showmore »« less

Authors:

Ahmad, M; Chu, A; Lincoln, H; Chen, Z; Deng, J; Nath, R ^[1]

Yale New Haven Hospital, New Haven, CT (United States)

Publication Date:: Sun Jun 01 00:00:00 EDT 2014

OSTI Identifier:: 22369582

Resource Type:: Journal Article

Journal Name:: Medical Physics

Additional Journal Information:: Journal Volume: 41; Journal Issue: 6; Other Information: (c) 2014 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0094-2405

Country of Publication:: United States

Language:: English

Subject:: 60 APPLIED LIFE SCIENCES; ACCURACY; COMPARATIVE EVALUATIONS; DEPTH DOSE DISTRIBUTIONS; DIAGRAMS; DOSES; ELECTRONS; FARMS; MONTE CARLO METHOD; ORGANIC COMPOUNDS; PHOTONS; PLANNING; PRODUCTION; VOLATILE MATTER

Citation Formats


                    Ahmad, M, Chu, A, Lincoln, H, Chen, Z, Deng, J, and Nath, R. SU-E-T-431: Vertically-Oriented Farmer-Type Chamber for Small-Field Applications.  United States: N. p., 2014. 
        Web.  doi:10.1118/1.4888764.

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                    Ahmad, M, Chu, A, Lincoln, H, Chen, Z, Deng, J, & Nath, R. SU-E-T-431: Vertically-Oriented Farmer-Type Chamber for Small-Field Applications.  United States.  https://doi.org/10.1118/1.4888764

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                    Ahmad, M, Chu, A, Lincoln, H, Chen, Z, Deng, J, and Nath, R. 2014.  
        "SU-E-T-431: Vertically-Oriented Farmer-Type Chamber for Small-Field Applications".  United States.  https://doi.org/10.1118/1.4888764.

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@article{osti_22369582,

  title        = {SU-E-T-431: Vertically-Oriented Farmer-Type Chamber for Small-Field Applications},

  author       = {Ahmad, M and Chu, A and Lincoln, H and Chen, Z and Deng, J and Nath, R},

  abstractNote = {Purpose: To introduce a non-conventional measurement setup using Farmer-type chambers to accommodate several situations of small-field dose measurements without compromising accuracy. The validation of this technique was demonstrated for photon small-field output measurements, and electron small-field percentage depth-dose (PDD) measurements. Methods: Initial chamber alignment was performed using the conventional (horizontally-oriented) chamber setup. A PDD was acquired for a 4×4 cm{sup 2} field size using this arrangement. This PDD was used as a positional reference for the vertically-oriented chamber (VOC) configuration. Next, a PDD was acquired for a 4×4 cm{sup 2} field size with the VOC. The PDD's were superimposed to find the effective shift of the VOC. Using the shifted VOC setup, photon small-field output factors were measured and compared to stereotactic diode output factor measurements. Additionally, electron smallfield PDD's were acquired using the VOC setup and results were compared to electron Monte Carlo (eMC) predictions in the Eclipse treatment planning system (TPS). Results: (1) For photon small-field output factors field-sizes 2×2 cm{sup 2} and larger, the difference between the VOC setup and SFD measurements were less than 0.8%. For field sizes less than 2×2 cm{sup 2} discrepancies ranged from 4.0 to 10.6%. (2) PDD's measured by VOC setup show better than 1.6% agreement as compared to eMC for all electron energies measured down to the 80% depth on the 2×2 cm{sup 2} PDD curve. Disagreement between the VOC setup measurement and eMC calculations for depths down to the 50% depth on the PDD curve is 3.6% or less. Conclusion: Using the VOC setup, it is possible to use a conventional farmer chamber for small field-size measurements down to 2×2 cm{sup 2} field size without sacrificing the accuracy of measurements.},

  doi          = {10.1118/1.4888764},

  url          = {https://www.osti.gov/biblio/22369582},
  journal      = {Medical Physics},

  issn         = {0094-2405},

  number       = 6,

  volume       = 41,

  place        = {United States},

  year         = {Sun Jun 01 00:00:00 EDT 2014},

  month        = {Sun Jun 01 00:00:00 EDT 2014}

}

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