Abstract
Purpose: Small radiation felds (<30 mm) are typically involved in stereotactic body radiation therapy procedures. Output factor measurements are subjected to large uncertainties. The signal ratio (SR) readings, defned as the ratio of central axis reading, respectively, in the actual feld size and in the reference feld size, were evaluated in several centers and a common mathematical description of the SR curve was investigated. Methods: A couple of new unshielded stereotactic diodes (Razor, IBA) was tested under eight di?erent TrueBeams using 10 MV ?attering flter free beams with high dose rate (2400 MU/min). Small felds, ranging from 6 to 50 mm, were analyzed in terms of profles and central axis point measurements. SRs were normalized to 30 mm feld and were calculated as a function of nominal feld size (NFS) and effective feld size (EFS). From SRs acquired using Razor1 (four centers), a theoretical equation was extrapolated. Three centers with Razor2 were used to test the mathematical relationship. Finally, the two diodes were directly compared in the last center. Results: The EFS was systematically smaller than NFS (p < 0.01) for all feld size ranges, with mean difference of 0.9±0.5 mm. The SR fts using the NFS and EFS had, respectively, R2 = 0.989 and R2 0.999. The Razor2 centers' mean deviation from the predicted SRs, using the NFS and EFS fts, was, respectively, 3.4% and 0.5%. The maximum deviations were 5.0% (6 mm feld size) for NFS and 1.9% for EFS. Maximum deviation of 0.5% between the two Razors was observed. Conclusions: EFS measurements were confrmed to be mandatory when comparing SRs over different centers. An equation establishing a functional relation between SRs and the EFS was obtained and tested for the new Razor diode.
| Original language | English |
|---|---|
| Pages (from-to) | 5570-5576 |
| Number of pages | 7 |
| Journal | Medical Physics |
| Volume | 43 |
| Issue number | 10 |
| DOIs | |
| Publication status | Published - Oct 1 2016 |
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Keywords
- flattening filter free beam
- multicenter study
- radiotherapy
- silicon diode detector
- small field dosimetry
- TrueBeam
ASJC Scopus subject areas
- Biophysics
- Radiology Nuclear Medicine and imaging
Cite this
Technical Note : Multicenter study of TrueBeam FFF beams with a new stereotactic diode: Can a common small field signal ratio curve be defined? / Cagni, Elisabetta; Russo, Serenella; Reggiori, Giacomo; Bresciani, Sara; Fedele, David; Iori, Mauro; Marino, Carmelo; Nardiello, Barbara; Ruggieri, Ruggero; Strigari, Lidia; Mancosu, Pietro.
In: Medical Physics, Vol. 43, No. 10, 01.10.2016, p. 5570-5576.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Technical Note
T2 - Multicenter study of TrueBeam FFF beams with a new stereotactic diode: Can a common small field signal ratio curve be defined?
AU - Cagni, Elisabetta
AU - Russo, Serenella
AU - Reggiori, Giacomo
AU - Bresciani, Sara
AU - Fedele, David
AU - Iori, Mauro
AU - Marino, Carmelo
AU - Nardiello, Barbara
AU - Ruggieri, Ruggero
AU - Strigari, Lidia
AU - Mancosu, Pietro
PY - 2016/10/1
Y1 - 2016/10/1
N2 - Purpose: Small radiation felds (<30 mm) are typically involved in stereotactic body radiation therapy procedures. Output factor measurements are subjected to large uncertainties. The signal ratio (SR) readings, defned as the ratio of central axis reading, respectively, in the actual feld size and in the reference feld size, were evaluated in several centers and a common mathematical description of the SR curve was investigated. Methods: A couple of new unshielded stereotactic diodes (Razor, IBA) was tested under eight di?erent TrueBeams using 10 MV ?attering flter free beams with high dose rate (2400 MU/min). Small felds, ranging from 6 to 50 mm, were analyzed in terms of profles and central axis point measurements. SRs were normalized to 30 mm feld and were calculated as a function of nominal feld size (NFS) and effective feld size (EFS). From SRs acquired using Razor1 (four centers), a theoretical equation was extrapolated. Three centers with Razor2 were used to test the mathematical relationship. Finally, the two diodes were directly compared in the last center. Results: The EFS was systematically smaller than NFS (p < 0.01) for all feld size ranges, with mean difference of 0.9±0.5 mm. The SR fts using the NFS and EFS had, respectively, R2 = 0.989 and R2 0.999. The Razor2 centers' mean deviation from the predicted SRs, using the NFS and EFS fts, was, respectively, 3.4% and 0.5%. The maximum deviations were 5.0% (6 mm feld size) for NFS and 1.9% for EFS. Maximum deviation of 0.5% between the two Razors was observed. Conclusions: EFS measurements were confrmed to be mandatory when comparing SRs over different centers. An equation establishing a functional relation between SRs and the EFS was obtained and tested for the new Razor diode.
AB - Purpose: Small radiation felds (<30 mm) are typically involved in stereotactic body radiation therapy procedures. Output factor measurements are subjected to large uncertainties. The signal ratio (SR) readings, defned as the ratio of central axis reading, respectively, in the actual feld size and in the reference feld size, were evaluated in several centers and a common mathematical description of the SR curve was investigated. Methods: A couple of new unshielded stereotactic diodes (Razor, IBA) was tested under eight di?erent TrueBeams using 10 MV ?attering flter free beams with high dose rate (2400 MU/min). Small felds, ranging from 6 to 50 mm, were analyzed in terms of profles and central axis point measurements. SRs were normalized to 30 mm feld and were calculated as a function of nominal feld size (NFS) and effective feld size (EFS). From SRs acquired using Razor1 (four centers), a theoretical equation was extrapolated. Three centers with Razor2 were used to test the mathematical relationship. Finally, the two diodes were directly compared in the last center. Results: The EFS was systematically smaller than NFS (p < 0.01) for all feld size ranges, with mean difference of 0.9±0.5 mm. The SR fts using the NFS and EFS had, respectively, R2 = 0.989 and R2 0.999. The Razor2 centers' mean deviation from the predicted SRs, using the NFS and EFS fts, was, respectively, 3.4% and 0.5%. The maximum deviations were 5.0% (6 mm feld size) for NFS and 1.9% for EFS. Maximum deviation of 0.5% between the two Razors was observed. Conclusions: EFS measurements were confrmed to be mandatory when comparing SRs over different centers. An equation establishing a functional relation between SRs and the EFS was obtained and tested for the new Razor diode.
KW - flattening filter free beam
KW - multicenter study
KW - radiotherapy
KW - silicon diode detector
KW - small field dosimetry
KW - TrueBeam
UR - http://www.scopus.com/inward/record.url?scp=84988734832&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84988734832&partnerID=8YFLogxK
U2 - 10.1118/1.4961744
DO - 10.1118/1.4961744
M3 - Article
VL - 43
SP - 5570
EP - 5576
JO - Medical Physics
JF - Medical Physics
SN - 0094-2405
IS - 10
ER -