External beam radiation therapy with kilovoltage x-rays

Breitkreutz, D.; M, Weil; Bazalova‐Carter, Magdalena

doi:10.1016/j.ejmp.2020.11.001

Cited by 21 publications

(15 citation statements)

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“…Most studies focused on conventional RT with high-energy megavoltage (MV) and low energy kilovoltage (kV) X-rays, as reviewed in (4,9,(11)(12)(13)(14). Up until now, the radiosensitizing effect of AuNPs are most pronounced for kV X-rays and while there is a motivation to use this radiation quality in the clinic alongside MV X-rays, its usage remains limited due to its shallow penetration depth in the patient (12,15).…”

Section: Introductionmentioning

confidence: 99%

Radiosensitization Effect of Gold Nanoparticles in Proton Therapy

Cunningham

Kock

Engelbrecht

et al. 2021

Front. Public Health

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The number of proton therapy facilities and the clinical usage of high energy proton beams for cancer treatment has substantially increased over the last decade. This is mainly due to the superior dose distribution of proton beams resulting in a reduction of side effects and a lower integral dose compared to conventional X-ray radiotherapy. More recently, the usage of metallic nanoparticles as radiosensitizers to enhance radiotherapy is receiving growing attention. While this strategy was originally intended for X-ray radiotherapy, there is currently a small number of experimental studies indicating promising results for proton therapy. However, most of these studies used low proton energies, which are less applicable to clinical practice; and very small gold nanoparticles (AuNPs). Therefore, this proof of principle study evaluates the radiosensitization effect of larger AuNPs in combination with a 200 MeV proton beam. CHO-K1 cells were exposed to a concentration of 10 μg/ml of 50 nm AuNPs for 4 hours before irradiation with a clinical proton beam at NRF iThemba LABS. AuNP internalization was confirmed by inductively coupled mass spectrometry and transmission electron microscopy, showing a random distribution of AuNPs throughout the cytoplasm of the cells and even some close localization to the nuclear membrane. The combined exposure to AuNPs and protons resulted in an increase in cell killing, which was 27.1% at 2 Gy and 43.8% at 6 Gy, compared to proton irradiation alone, illustrating the radiosensitizing potential of AuNPs. Additionally, cells were irradiated at different positions along the proton depth-dose curve to investigate the LET-dependence of AuNP radiosensitization. An increase in cytogenetic damage was observed at all depths for the combined treatment compared to protons alone, but no incremental increase with LET could be determined. In conclusion, this study confirms the potential of 50 nm AuNPs to increase the therapeutic efficacy of proton therapy.

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Section: Introductionmentioning

confidence: 99%

Radiosensitization Effect of Gold Nanoparticles in Proton Therapy

Cunningham

Kock

Engelbrecht

et al. 2021

Front. Public Health

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“…The lower energy dosimetry we have evaluated in the simplified geometry of the 15.6 cm diameter cylindrical, acrylic phantom used in this study, is encouraging for that next engineering step. In follow‐on studies, this will also be addressed by comparison and validation with inverse optimized MC simulated results such as those presented in previous papers by members of our team 7,11–13 …”

Section: Discussionmentioning

confidence: 99%

“…In follow-on studies, this will also be addressed by comparison and validation with inverse optimized MC simulated results such as those presented in previous papers by members of our team. 7,[11][12][13] Although the main objective of this study was to evaluate the dose distributions within phantoms for LCRS, the dose rate can also be estimated from the film dosimetry data for LCRS at 140 and 145 kVp. Dose rate can be found by dividing the dose by the total time of delivery, where the delivery time can be projected from the beam quantity (mAs) divided by the operating beam current (mA).…”

Section: Discussionmentioning

confidence: 99%

“…Imaging may be generated via illumination of an opposing flat panel detector 5 . Furthermore, the ability to rapidly change between imaging and therapy tungsten targets, coupled with the programmable deflection and focusing of the scanning electron‐beam system, enables precise tumor‐tracking during treatment 6,7 . The LCRS is capable of both cone‐beam CT (CBCT) imaging and real‐time digital 3D tomosynthesis, utilizing technology developed for another project, the 130 kVp TumoTrak X‐ray source 3 …”

Section: Introductionmentioning

confidence: 99%

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Dosimetry of a novel converging X‐ray source for kilovoltage radiotherapy

Stalbaum¹,

Partain²,

M³

et al. 2021

Medical Physics

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Purpose:The objective of this work was to evaluate phantom dosimetry of a novel kilovoltage (kV) X-ray source, which employs a stationary tungsten anode and a linearly swept scanning electron beam. The source utilizes converging Xray collimation along with orthogonal mechanical rotation to distribute surface flux over large area. In this study, this was investigated as a potential solution to fast-falloff limitations expected with kV radiotherapy. This was done with the aim of future clinical development of a lower cost radiotherapy alternative to megavoltage (MV) linac systems. Methods: Radiochromic film was employed for dosimetry on the kV X-ray source of the linear-converging radiotherapy system (LCRS). The source utilizes charge particle optics to magnetically deflect and focus an electron beam along a stationary, reflection tungsten target in an ultra-high-vacuum stainlesssteel chamber. Resulting X-rays were collimated into converging beamlets that span a large planar angle and converge at the system isocenter. In this study, radiochromic film dosimetry was done at 140 and 145 kVp for a designated planning treatment volume (PTV) of 4 cm diameter. An acrylic phantom was employed for dose distribution measurements of stationary and rotational delivery. Film dosimetry was evaluated in planes parallel to the source X-ray window at various depths, as well as in the plane of gantry rotation. Results: At 140 and 145 kVp and using a collimated 4 cm square field at depth, lesion-to-skin dose ratio was shown to improve with additional beams from different relative source positions, where the different beams are focused at the same isocenter and do not overlap at the phantom surface. It was only possible to achieve a 1:1 D max -to-surface ratio with four delivery beams, but the ratio improved to 4:1 with 12 beams, focused at the same isocenter depth of 7.8 cm in an acrylic phantom. For the tests conducted, the following D max -to-surface ratios were obtained: 0.4:1 lesion-to-skin ratio for stationary delivery from one entry beam, 0.71:1 lesion-to-skin ratio was obtained for two beams, 1.07:1 ratio for four beams, and 4:1 for 12 beams. Dose-depth profiles were evaluated for stationary and rotational dosimetry. Additionally, rotational dosimetry was measured for a case more analogous to a clinical scenario, where the isocenter was located at an off -center simulated lesion. Conclusions:The results demonstrate potential dose-depth improvements with kV arc therapy by distributing the surface flux with a wide converging beam along with perpendicular mechanical source rotation of the LCRS. The system delivered tolerable dose to a large surface area when a threshold of multiple,

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“…It is not only the technical progress in X-ray tube design, but the variety of special applications up to even IMRT and not least the cost-effectiveness which brings back the interest of kV-Xray radiotherapy beyond the established indications of treatment of superficial tumors and benign diseases. The article of D. Breiktreutz et al [12] presents a comprehensive review of the current status and an overview of promising developments.…”

Section: X-ray Radiotherapymentioning

confidence: 99%