Relative biological effectiveness of neutron radiation and its implications for quality factor and dose limitation

Dennis, J.A.

doi:10.1016/0149-1970(87)90018-7

Cited by 11 publications

(10 citation statements)

References 64 publications

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“…Others have estimated the low-dose RBE for neutron-induced carcinogenesis in humans to be 100 for solid-cancer mortality (Kellerer et al 2006) and 63 for overall cancer incidence (Little 1997) based on the atomic-bomb survivors. Values up to 80 have been reported considering several endpoints (Dennis 1987; NCRP 1990; Edwards 1999). Thus, the effectiveness of neutron radiation is subject to significant uncertainties (Kocher et al 2005; Brenner and Hall 2008; Xu and Paganetti 2010).…”

Section: Methodology For Second Cancer Risk Modelingmentioning

confidence: 99%

Assessment of the Risk for Developing a Second Malignancy From Scattered and Secondary Radiation In Radiation Therapy

Paganetti¹

2012

Health Physics

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With the average age of radiation therapy patients decreasing and the advent of more complex treatment options comes the concern that the incidences of radiation-induced cancer might increase in the future. The carcinogenic effects of radiation are not well understood for the entire dose range experienced in radiation therapy. Longer epidemiological studies are needed to improve current risk models and reduce uncertainties of current risk model parameters. On the other hand, risk estimations are needed today to judge the risks vs. benefits of modern radiation therapy techniques. This paper describes the current state-of-the-art in risk modeling for radiation-induced malignancies in radiation therapy, distinguishing between two volumes. First, the organs within the main radiation field receiving low or intermediate doses (typically between 0.1 and 50 Gy). Second, the organs far away from the treatment volume receiving low doses mainly due to scattered and secondary radiation (typically below 0.1 Gy). The dosimetry as well as the risk model formalisms are outlined. Furthermore, example calculations and results are presented for intensity-modulated photon therapy vs. proton therapy.

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Section: Methodology For Second Cancer Risk Modelingmentioning

confidence: 99%

Assessment of the Risk for Developing a Second Malignancy From Scattered and Secondary Radiation In Radiation Therapy

Paganetti¹

2012

Health Physics

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“…The BEIR report (BEIR 2006) recommends a neutron quality factor of 10 independent of neutron energy (although it is acknowledged that this might be too low when low doses are involved). Dennis (Dennis 1987) has summarized experimental neutron RBE data and found maximum values (low dose) between 6.44 and 71 in vivo. Similarly, the NCRP has shown elevated neutron quality factors for fission neutrons considering several radiation endpoints (NCRP 1990).…”

Section: Discussionmentioning

confidence: 99%

Assessment of organ-specific neutron equivalent doses in proton therapy using computational whole-body age-dependent voxel phantoms

et al. 2008

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Proton beams used for radiotherapy will produce neutrons when interacting with matter. The purpose of this study was to quantify the equivalent dose to tissue due to secondary neutrons in pediatric and adult patients treated by proton therapy for brain lesions. Assessment of the equivalent dose to organs away from the target requires whole-body geometrical information. Furthermore, because patient geometry depends on age at exposure, age-dependent representations are also needed. We implemented age-dependent phantoms into our proton Monte Carlo dose calculation environment. We considered 8 typical radiation fields, 2 of which had been previously used to treat pediatric patients. The other 6 fields were additionally considered to allow a systematic study of equivalent doses as a function of field parameters. For all phantoms and all fields, we simulated organ specific equivalent neutron doses and analyzed for each organ (1) the equivalent dose due to neutrons as a function of distance to the target; (2) the equivalent dose due to neutrons as a function of patient age; (3) the equivalent dose due to neutrons as a function of field parameters; and (4) the ratio of contributions to secondary dose from the treatment head versus the contribution from the patient's body tissues. This work reports organ specific equivalent neutron doses for up to 48 organs in a patient. We demonstrate quantitatively how organ equivalent doses for adult and pediatric patients vary as a function of patient's age, organ, and field parameters. Neutron doses increase with increasing range and modulation width but decrease with field size (as defined by the aperture). We analyzed the ratio of neutron dose contributions from the patient and from the treatment head, and found that neutron equivalent doses fall off rapidly as a function of distance from the target, in agreement with experimental data. It appears that for the fields used in this study, the neutron dose lateral to the field is smaller than the reported scattered photon doses in a typical intensity modulated photon treatment. Most importantly, our study shows that neutron doses to specific organs depend considerably on the patient's age and body stature. The younger the patient, the higher the dose deposited due to neutrons. Given the fact that the risk also increases with decreasing patient age, this factor needs to be taken into account when treating pediatric patients of very young ages and/or of small body size. The neutron dose from a course of proton therapy treatment (assuming 70 Gy in 30

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“…However, differences may be expected between RBE for cell survival and mutation . Similarly, higher neutron RBE values have been found for in vitro scenarios than for in vivo scenarios . Nevertheless, the ICRP has stated that, in situations where high‐LET radiations are involved, an absorbed dose weighted with an appropriate RBE should be used .…”

Section: Dose Reportingmentioning

confidence: 99%

AAPM TG158: Measurement and calculation of doses outside the treated volume from external‐beam radiation therapy

et al. 2017

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The introduction of advanced techniques and technology in radiotherapy has greatly improved our ability to deliver highly conformal tumor doses while minimizing the dose to adjacent organs at risk. Despite these tremendous improvements, there remains a general concern about doses to normal tissues that are not the target of the radiation treatment; any "nontarget" radiation should be minimized as it offers no therapeutic benefit. As patients live longer after treatment, there is increased opportunity for late effects including second cancers and cardiac toxicity to manifest. Complicating the management of these issues, there are unique challenges with measuring, calculating, reducing, and reporting nontarget doses that many medical physicists may have limited experience with. Treatment planning systems become dramatically inaccurate outside the treatment field, necessitating a measurement or some other means of assessing the dose. However, measurements are challenging because outside the treatment field, the radiation energy spectrum, dose rate, and general shape of the dose distribution (particularly the percent depth dose) are very different and often require special consideration. Neutron dosimetry is also particularly challenging, and common errors in methodology can easily manifest as errors of several orders of magnitude. Task Group 158 was, therefore, formed to provide guidance for physicists in terms of assessing and managing nontarget doses. In particular, the report: (a) highlights major concerns with nontarget radiation; (b) provides a rough estimate of doses associated with different treatment approaches in clinical practice; (c) discusses the uses of dosimeters for measuring photon, electron, and neutron doses; (d) discusses the use of calculation techniques for dosimetric evaluations; (e) highlights techniques that may be considered for reducing nontarget doses; (f) discusses dose reporting; and (g) makes recommendations for both clinical and research practice.

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Relative biological effectiveness of neutron radiation and its implications for quality factor and dose limitation

Cited by 11 publications

References 64 publications

Assessment of the Risk for Developing a Second Malignancy From Scattered and Secondary Radiation In Radiation Therapy

Assessment of the Risk for Developing a Second Malignancy From Scattered and Secondary Radiation In Radiation Therapy

Assessment of organ-specific neutron equivalent doses in proton therapy using computational whole-body age-dependent voxel phantoms

AAPM TG158: Measurement and calculation of doses outside the treated volume from external‐beam radiation therapy

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