Document Detail

Measurement of LINAC 90 degrees head leakage radiation TVL values.
MedLine Citation:
PMID:  17022250     Owner:  NLM     Status:  MEDLINE    
One of the key components in modern LINAC room shielding design is the amount of 90 degrees head leakage radiation levels. With the general clinical acceptance of intensity-modulated radiation therapy (IMRT) technique, accurate knowledge of this quantity has become even more important. Measurement of 90 degrees head leakage radiation of medical linear accelerators can be technically challenging due to the low dose rate causing poor signal-to-noise ratios in most detectors. 90 degrees leakage tenth-value layer (TVL) values in concrete have not been reported for the Elekta linear accelerators. This report describes our measurements of 90 degrees leakage TVL values for 6, 10, and 18 MV x-ray beams for an Elekta Precise Treatment System. A large-volume (1000 cm3) unpressurized ionization chamber and a high sensitivity electrometer, together with a separate chamber bias power supply, were used in these measurements in order to maximize the signal-to-noise ratio. A lead enclosure, of minimum thickness 10 cm, was constructed inside the treatment room to house the ion chamber to reduce the influence of room-scattered radiation. A square aperture of 10 X 10 cm2 area was left in the shield and aimed towards the accelerator head. Measurements were performed with the chamber placed at approximately 2 m from the accelerator isocenter. Concrete slabs with individual dimensions of approximately 40 X 40 cm2 cross-sectional area and 5 cm thickness were placed between the accelerator head and the ion chamber for these measurements. The measurements were performed with total concrete thickness of up to 80 cm, so that values up to the third TVL were measured. These measurements showed thatthe first concrete TVL values are 22, 23, and 28 cm (8.6, 9.1, and 10.5 in.) for 6, 10, and 18 MV beams, while the average of the first 3 TVL's were 25, 26, and 29 cm (9.9, 10.2, and 11.5 in.). Measured values agreed to within 10% of previously reported values for Varian linear accelerators for equivalent radiation beam qualities.
Zuofeng Li; Sasa Mutic; Daniel Low
Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Medical physics     Volume:  33     ISSN:  0094-2405     ISO Abbreviation:  Med Phys     Publication Date:  2006 Sep 
Date Detail:
Created Date:  2006-10-06     Completed Date:  2006-11-20     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0425746     Medline TA:  Med Phys     Country:  United States    
Other Details:
Languages:  eng     Pagination:  3541-5     Citation Subset:  IM    
Department of Radiation Oncology, Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
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MeSH Terms
Equipment Design
Equipment Failure Analysis
Particle Accelerators*
Radiation Dosage
Radiation Injuries / prevention & control
Radiation Protection / methods*
Radiometry / instrumentation*,  methods*
Risk Assessment / methods*
Risk Factors

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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