PMID- 27908161
OWN - NLM
STAT- MEDLINE
DCOM- 20170315
LR  - 20170315
IS  - 2473-4209 (Electronic)
IS  - 0094-2405 (Linking)
VI  - 43
IP  - 12
DP  - 2016 Dec
TI  - Technical Note: Magnetic field effects on Gafchromic-film response in MR-IGRT.
PG  - 6552
AB  - PURPOSE: Magnetokinetic changes may affect crystal orientation and polymerization 
      within the active layer of radiochromic film (RCF). This effect is investigated 
      in a magnetic resonance image-guided radiotherapy unit within the context of film 
      dosimetry. METHODS: Gafchromic EBT2 RCF was irradiated in a 30 x 30 x 30 cm(3) 
      solid water phantom using a Co-60 MRI guided radiotherapy system (B = 0.35 T) 
      under normal operating conditions, and under the exact conditions and setup 
      without a magnetic field. Fifteen 20.3 x 25.4 cm(2) EBT2 film sheets were placed 
      at three different depths (d = 0.5, 5, and 10 cm) using five different treatment 
      plans. The plans were computed using the MRIdian (ViewRay, Inc.) treatment 
      planning system to deliver doses between 0 and 17.6 Gy. Films were analyzed 
      before and after irradiation to obtain the net optical density (netOD) for each 
      color channel separately. Scanning electron microscope (SEM) images were obtained 
      to compare the active layer of selected samples. RESULTS: The results indicated 
      that the red channel netOD decreased between 0.013 and 0.123 (average of 0.060 +/- 
      0.033) for doses above 2.8 Gy, with a linear increase in this effect for higher 
      doses. Green channel netOD showed similar results with a decrease between 0.012 
      and 0.105 (average of 0.041 +/- 0.027) for doses above 3.5 Gy. The blue channel 
      showed the weakest effect with a netOD decrease between 0.013 and 0.029 (average 
      of 0.020 +/- 0.006) for doses above 8.0 Gy. SEM images show changes in crystal 
      orientation within active layer in RCF exposed in a magnetic field. CONCLUSIONS: 
      The presence of a magnetic field affects crystal orientation and polymerization 
      during irradiation, where netOD decreased by an average of 8.7%, 8.0%, and 4.3% 
      in the red, green, and blue channels, respectively. The under response was 
      dependent on dose and differed by up to 15% at 17.6 Gy.
FAU - Reynoso, Francisco J
AU  - Reynoso FJ
AD  - Department of Radiation Oncology, Washington University School of Medicine, St. 
      Louis, Missouri 63110.
FAU - Curcuru, Austen
AU  - Curcuru A
AD  - Department of Radiation Oncology, Washington University School of Medicine, St. 
      Louis, Missouri 63110.
FAU - Green, Olga
AU  - Green O
AD  - Department of Radiation Oncology, Washington University School of Medicine, St. 
      Louis, Missouri 63110.
FAU - Mutic, Sasa
AU  - Mutic S
AD  - Department of Radiation Oncology, Washington University School of Medicine, St. 
      Louis, Missouri 63110.
FAU - Das, Indra J
AU  - Das IJ
AD  - Department of Radiation Oncology, New York University Langone Medical Center, New 
      York, New York 10016.
FAU - Santanam, Lakshmi
AU  - Santanam L
AD  - Department of Radiation Oncology, Washington University School of Medicine, St. 
      Louis, Missouri 63110.
LA  - eng
PT  - Journal Article
PL  - United States
TA  - Med Phys
JT  - Medical physics
JID - 0425746
SB  - IM
MH  - Equipment Design
MH  - *Film Dosimetry
MH  - *Magnetic Fields
MH  - *Magnetic Resonance Imaging
MH  - Phantoms, Imaging
MH  - *Radiotherapy, Image-Guided
EDAT- 2016/12/03 06:00
MHDA- 2017/03/16 06:00
CRDT- 2016/12/03 06:00
PHST- 2016/12/03 06:00 [entrez]
PHST- 2016/12/03 06:00 [pubmed]
PHST- 2017/03/16 06:00 [medline]
AID - 10.1118/1.4967486 [doi]
PST - ppublish
SO  - Med Phys. 2016 Dec;43(12):6552. doi: 10.1118/1.4967486.