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Titolo:
Evaluation of polymer gels and MRI as a 3-D dosimeter for intensity-modulated radiation therapy
Autore:
Low, DA; Dempsey, JF; Venkatesan, R; Mutic, S; Markman, J; Haacke, EM; Purdy, JA;
Indirizzi:
Edward Mallinckrodt Inst Radiol, Div Radiat Oncol, St Louis, MO 63110 USA Edward Mallinckrodt Inst Radiol St Louis MO USA 63110 Louis, MO 63110 USA Edward Mallinckrodt Inst Radiol, Dept Radiol Sci, St Louis, MO 63110 USA Edward Mallinckrodt Inst Radiol St Louis MO USA 63110 Louis, MO 63110 USA
Titolo Testata:
MEDICAL PHYSICS
fascicolo: 8, volume: 26, anno: 1999,
pagine: 1542 - 1551
SICI:
0094-2405(199908)26:8<1542:EOPGAM>2.0.ZU;2-G
Fonte:
ISI
Lingua:
ENG
Soggetto:
DYNAMIC MULTILEAF COLLIMATION; PENCIL-BEAM ALGORITHM; DOSE-CALCULATION ALGORITHM; QUANTITATIVE-EVALUATION; DISTRIBUTIONS; OPTIMIZATION; VERIFICATION; SYSTEM; HEAD;
Keywords:
intensity-modulated radiation therapy; BANG polymerizing gel; three-dimensional dose distribution analysis;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Clinical Medicine
Life Sciences
Citazioni:
29
Recensione:
Indirizzi per estratti:
Indirizzo: Low, DA Edward Mallinckrodt Inst Radiol, Div Radiat Oncol, 510 S Kingshighway Blvd, St Louis, MO 63110 USA Edward Mallinckrodt Inst Radiol 510 S Kingshighway Blvd St Louis MO USA 63110
Citazione:
D.A. Low et al., "Evaluation of polymer gels and MRI as a 3-D dosimeter for intensity-modulated radiation therapy", MED PHYS, 26(8), 1999, pp. 1542-1551

Abstract

BANG(R) gel (MGS Research, Inc., Guilford, CT) has been evaluated for measuring intensity-modulated radiation therapy (IMRT) dose distributions. Treatment plans with target doses of 1500 cGy were generated by the Peacock IMRT system (NOMOS Corp., Sewickley, PA) using test target volumes. The gels were enclosed in 13 cm outer diameter cylindrical glass vessels. Dose calibration was conducted using seven smaller (4 cm diameter) cylindrical glass vessels irradiated to 0-1800 cGy in 300 cGy increments. Three-dimensional maps of the proton relaxation rate R-2 were obtained using a 1.5 T magnetic resonance imaging (MRI) system (Siemens Medical Systems, Erlangen, Germany) and correlated with dose. A Hahn spin echo sequence was used with TR=3 s, TE=20 and 100 ms, NEX=1, using 1X1X3 mm(3) voxels. The MRI measurements wererepeated weekly to identify the gel-aging characteristics. Ionization chamber, thermoluminescent dosimetry (TLD), and film dosimetry measurements of the IMRT dose distributions were obtained to compare against the gel results. The other dosimeters were used in a phantom with the same external cross-section as the gel phantom. The irradiated R-2 values of the large vesselsdid not precisely track the smaller vessels, so the ionization chamber measurements were used to normalize the gel dose distributions. The point-to-point standard deviation of the gel dose measurements was 7.0 cGy. When compared with the ionization chamber measurements averaged over the chamber volume, 1% agreement was obtained. Comparisons against radiographic film dose distribution measurements and the treatment planning dose distribution calculation were used to determine the spatial localization accuracy of the geland MRI. Spatial localization was better than 2 mm, and the dose was accurately determined by the gel both within and outside the target. The TLD chips were placed throughout the phantom to determine gel measurement precision in high- and low-dose regions. A multidimensional dose comparison tool that simultaneously examines the dose difference and distance-to-agreement was used to evaluate the gel in both low-and high-dose,gradient regions. When3% and 3 mm criteria were used for the comparisons, more than 90% of the TLD measurements agreed with the gel, with the worst of 309 TLD chip measurements disagreeing by 40% of the criteria. All four MRI measurement session gel-measured dose distributions were compared to evaluate the time behaviorof the gel. The low-dose regions were evaluated by comparison with TLD measurements at selected points, while high-dose regions were evaluated by directly comparing measured dose distributions. Tests using the multidimensional comparison tool showed detectable degradation beyond one week postirradiation, but all low-dose measurements passed relative to the test criteria and the dose distributions showed few regions that failed. (C) 1999 AmericanAssociation of Physicists in Medicine. [S0094-2405(99)02508-0].

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 31/03/20 alle ore 18:42:28