Energy spectra, sources, and shielding considerations for neutrons generated by a flattening filter-free Clinac

Journal Article · Thu May 15 04:00:00 EDT 2008 · Medical Physics

DOI:https://doi.org/10.1118/1.2905029· OSTI ID:21120692

Kry, Stephen F; Howell, Rebecca M; Titt, Uwe; Salehpour, Mohammad; Mohan, Radhe; Vassiliev, Oleg N ^[1]

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1. Department of Radiation Physics, University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030 (United States)

Neutron production is an unwanted result of high-energy radiation therapy and results in secondary exposure of patients and radiation therapists to radiation. Recent studies have shown that delivering therapy using a standard medical accelerator with the flattening filter removed may reduce neutron fluence by nearly 70% over the course of prostate intensity-modulated radiation therapy (IMRT). In the current study, the {sup 197}Au Bonner sphere technique was used to compare the neutron spectrum produced when the filter is present and when it is absent. In addition, the following was calculated: (1) the neutron-shielding parameters of source strength and ambient dose equivalent (H{sub 0}) and (2) using the Monte Carlo technique, the sources of neutron production in the accelerator head. It was found that the neutron spectrum was nearly constant, regardless of the presence of the flattening filter; however, the total fluence and ambient dose equivalent over the course of prostate IMRT were more than 70% lower when the filter was removed. Similarly, shielding parameters were lower when the filter was removed. Finally, the primary collimator and jaws accounted for the majority of neutron production, both with and without the flattening filter; however, with the flattening filter removed, the upper jaw accounted for much more neutron production relative to when the filter was present. Ultimately, removal of the flattening filter may offer several clinical advantages, including a reduction in the dose from neutrons to the patient and to radiation personnel.

• OSTI ID: 21120692
• Journal Information: Medical Physics, Journal Name: Medical Physics Journal Issue: 5 Vol. 35; ISSN 0094-2405; ISSN MPHYA6
• Country of Publication: United States
• Language: English

Related Subjects

61 RADIATION PROTECTION AND DOSIMETRY
COLLIMATORS
DOSE EQUIVALENTS
DOSIMETRY
LINEAR ACCELERATORS
MODULATION
MONTE CARLO METHOD
NEUTRON FLUENCE
NEUTRON SOURCES
NEUTRON SPECTRA
PATIENTS
PROSTATE
RADIATION PROTECTION
RADIOTHERAPY
SHIELDING