Response to “Comment on ‘Verification of absorbed dose determined with plane-parallel chambers in clinical electron beams following AAPM Task Group 39 protocol using ferrous sulphate dosimetry’ ” [Med. Phys. 23 , 377-381 (1996)]

1996 ◽  
Vol 23 (10) ◽  
pp. 1817-1817
Author(s):  
Zhigang Xu ◽  
Hui Li ◽  
P. R. Almond ◽  
T. Y. Guan
Keyword(s):  
Electron Beams ◽  
Ferrous Sulphate ◽  
Absorbed Dose ◽  
Task Group ◽  
Plane Parallel

The calibration and use of plane-parallel ionization chambers for dosimetry of electron beams: An extension of the 1983 AAPM protocol report of AAPM Radiation Therapy Committee Task Group No. 39

1994 ◽  
Vol 21 (8) ◽  
pp. 1251-1260 ◽  
Author(s):  
Peter R. Almond ◽  
Frank H. Attix ◽  
Leroy J. Humphries ◽  
Hideo Kubo ◽  
Ravinder Nath ◽  
...  
Keyword(s):  
Radiation Therapy ◽  
Electron Beams ◽  
Task Group ◽  
Ionization Chambers ◽  
Plane Parallel

New dosimetric approach for multidimensional dose evaluation in gamma knife radiosurgery

2000 ◽  
Vol 93 (supplement_3) ◽  
pp. 239-242 ◽  
Author(s):  
R. Foroni ◽  
G. Gambraini ◽  
U. Danesi ◽  
M. Mauri ◽  
E. Pompilio ◽  
...  
Keyword(s):  
Gamma Knife ◽  
Metal Ion ◽  
Light Transmission ◽  
Xylenol Orange ◽  
Ferrous Sulphate ◽  
Gamma Knife Radiosurgery ◽  
Absorbed Dose ◽  
Content Type ◽  
3D Representation ◽  
Fine Print

✓ During the past two decades, the progress in computerized treatment planning systems has led to more accurate imaging and therapy by using the gamma knife, especially with the smallest collimators (4 mm). However, the ionization chambers that have been used to calibrate the gamma knife are not useful with the smallest collimators because the chambers are too big compared with the irradiated volume. Therefore, it is important to develop more suitable dosimeters. This study proposes a new dosimeter method. The FriXyGel method proposed here is based on a phantom dosimeter, an acquisition chain, and dedicated software. This dosimeter uses an agarose gel into which a ferrous sulphate solution (Fricke solution) and a metal ion indicator (xylenol orange) are incorporated. The absorbed dose is detected through measurements of visible light transmission, imaged by means of a charge-coupled device camera provided with a suitable optical filter. Gel layers are imaged before and after irradiation, and the differences in light absorption are related to the absorbed dose. By choosing convenient thickness of gel layers and by building up a phantom with different gel slices, it is possible to obtain a three-dimensional (3D) representation of the absorbed dose. The final 3D representation is reached after several mathematical processes have been applied to the images. The first step identifies and reduces all factors that could alter the original data, such as nonuniformity in illumination. Then, after calibration procedures, it is possible to obtain absorbed dose values and to discover their 3D representation. This goal has been reached by developing appropriate software that performs all the calculations necessary for spatial representation routines and prompt comparison with theoretical calculations.

The calibration and use of plane-parallel ionization chambers for dosimetry of electron beams

1995 ◽  
Vol 22 (8) ◽  
pp. 1307-1314 ◽  
Author(s):  
P. R. Almond ◽  
Zhigang Xu ◽  
Hui Li ◽  
H. C. Park
Keyword(s):  
Electron Beams ◽  
Ionization Chambers ◽  
Plane Parallel
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