Commissioning of intensity modulated neutron radiotherapy (IMNRT)

Burmeister, Jay; Spink, Robyn; Liang, Liang; Bossenberger, Todd; Halford, Robert; Brandon, John; DeLauter, J.; Snyder, Michael

doi:10.1118/1.4766878

Cited by 6 publications

(5 citation statements)

References 36 publications

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“…The neutron treatment morbidity of 10% was comparable to the 8% morbidity for MV x-rays (Austin-Seymour et al 1994). It is important to recognize that the results of early clinical trials based on fast neutron therapy with fixed-beams and primitive blocking are not representative of the effectiveness of 3D conformal treatments delivered with the CNTS-nor of the potential effectiveness of neutron therapy using even more advanced IMRT (Snyder et al 2011, 2012, Burmeister et al 2013 or VMAT techniques with the ability to further improve normal-tissue sparing without sacrificing tumor coverage. In the case reported by Macomber et al (2017) demonstrating the efficacy of neutron therapy after treatment failure with low LET radiations, it is notable that there was no significant toxicity to the patient despite re-irradiation.…”

Section: Introductionmentioning

confidence: 99%

Dosimetric characteristics of the University of Washington Clinical Neutron Therapy System

et al. 2018

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The University of Washington (UW) Clinical Neutron Therapy System (CNTS), which generates high linear energy transfer fast neutrons through interactions of 50.5 MeV protons incident on a Be target, has depth-dose characteristics similar to 6 MV x-rays. In contrast to the fixed beam angles and primitive blocking used in early clinical trials of neutron therapy, the CNTS has a gantry with a full 360° of rotation, internal wedges, and a multi-leaf collimator (MLC). Since October of 1984, over 3178 patients have received conformal neutron therapy treatments using the UW CNTS. In this work, the physical and dosimetric characteristics of the CNTS are documented through comparisons of measurements and Monte Carlo simulations. A high resolution computed tomography scan of the model 17 ionization chamber (IC-17) has also been used to improve the accuracy of simulations of the absolute calibration geometry. The response of the IC-17 approximates well the kinetic energy released per unit mass (KERMA) in water for neutrons and photons for energies from a few tens of keV up to about 20 MeV. Above 20 MeV, the simulated model 17 ion chamber response is 20%-30% higher than the neutron KERMA in water. For CNTS neutrons, simulated on- and off-axis output factors in water match measured values within ~2% ± 2% for rectangular and irregularly shaped field with equivalent square areas ranging in a side dimension from 2.8 cm to 30.7 cm. Wedge factors vary by less than 1.9% of the measured dose in water for clinically relevant field sizes. Simulated tissue maximum ratios in water match measured values within 3.3% at depths up to 20 cm. Although the absorbed dose for water and adipose tissue are within 2% at a depth of 1.7 cm, the absorbed dose in muscle and bone can be as much as 12 to 40% lower than the absorbed dose in water. The reported studies are significant from a historical perspective and as additional validation of a new tool for patient quality assurance and as an aid in ongoing efforts to clinically implement advanced treatment techniques, such as intensity modulated neutron therapy, at the UW.

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Section: Introductionmentioning

confidence: 99%

Dosimetric characteristics of the University of Washington Clinical Neutron Therapy System

et al. 2018

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“…A neutron-sensitive pretreatment quality-assurance system is currently being verified for use before patient treatments. Although IMNT has been commissioned previously [ 32 ], our institution will be the first to implement it clinically. We expect to begin offering IMNT to selected patients with head and neck cancers in late spring of 2021.…”

Section: Discussionmentioning

confidence: 99%

“…In prospective clinical studies, IMRT has been shown to decrease the OAR toxicity from photon radiation when compared with 3DCNT [27][28][29][30][31]. Intensity-modulated neutron therapy (IMNT) has been previously commissioned [32] and has shown dosimetric advantages, although planning studies have been limited to the prostate [4,33]. The effect of IMNT on OAR doses in patients with head and neck cancers has yet to be evaluated, to our knowledge, which is the focus of this work.…”

Section: Introductionmentioning

confidence: 99%

Comparisons of 3-Dimensional Conformal and Intensity-Modulated Neutron Therapy for Head and Neck Cancers

Viscariello

Greer

Parvathaneni

et al. 2021

International Journal of Particle Therapy

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Purpose Neutron therapy is a high linear energy transfer modality that is useful for the treatment of radioresistant head and neck (H&N) cancers. It has been limited to 3-dimensioanal conformal-based fast-neutron therapy (3DCNT), but recent technical advances have enabled the clinical implementation of intensity-modulated neutron therapy (IMNT). This study evaluated the comparative dosimetry of IMNT and 3DCNT plans for the treatment of H&N cancers. Materials and Methods Seven H&N IMNT plans were retrospectively created for patients previously treated with 3DCNT at the University of Washington (Seattle). A custom RayStation model with neutron-specific scattering kernels was used for inverse planning. Organ-at-risk (OAR) objectives from the original 3DCNT plan were initially used and were then systematically reduced to investigate the feasibility of improving a therapeutic ratio, defined as the ratio of the mean tumor to OAR dose. The IMNT and 3DCNT plan quality was evaluated using the therapeutic ratio, isodose contours, and dose volume histograms. Results When compared with the 3DCNT plans, IMNT reduces the OAR dose for the equivalent tumor coverage. Moreover, IMNT is most advantageous for OARs in close spatial proximity to the target. For the 7 patients with H&N cancers examined, the therapeutic ratio for IMNT increased by an average of 56% when compared with the 3DCNT. The maximum OAR dose was reduced by an average of 20.5% and 20.7% for the spinal cord and temporal lobe, respectively. The mean dose to the larynx decreased by an average of 80%. Conclusion The IMNT significantly decreases the OAR doses compared with 3DCNT and provides comparable tumor coverage. Improvements in the therapeutic ratio with IMNT are especially significant for dose-limiting OARs near tumor targets. Moreover, IMNT provides superior sparing of healthy tissues and creates significant new opportunities to improve the care of patients with H&N cancers treated with neutron therapy.

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“…Soon, FNT is expected to become more conformal and substantially safer because of the ongoing development in intensitymodulated neutron therapy [15]. However, lack of funding might be a nonnegligible pitfall for the therapy.…”

Section: Discussionmentioning

confidence: 99%

Fast Neutron Therapy for Breast Cancer Treatment: An Effective Technique Sinking into Oblivion

Loap

Kirova

2021

International Journal of Particle Therapy

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Commissioning of intensity modulated neutron radiotherapy (IMNRT)

Cited by 6 publications

References 36 publications

Dosimetric characteristics of the University of Washington Clinical Neutron Therapy System

Dosimetric characteristics of the University of Washington Clinical Neutron Therapy System

Comparisons of 3-Dimensional Conformal and Intensity-Modulated Neutron Therapy for Head and Neck Cancers

Fast Neutron Therapy for Breast Cancer Treatment: An Effective Technique Sinking into Oblivion

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