Recent Clinical Experience with the Grid in the X-Ray Treatment of Advanced Cancer

Harris, William C.

doi:10.1148/58.3.343

Cited by 16 publications

(9 citation statements)

References 2 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…As indicated above, dose–volume effect means that the tissue’s tolerance to radiation increases as the volume of the irradiated tissue decreases ( 2 , 3 ). The effect, valid for any target size, has been the basis for grid therapy ( 1 ) and stereotactic radiosurgery ( 4 ). On the other hand, the prompt, microscopic, biological repair is specific to microbeams and minibeams at beam sizes below about 0.7 mm.…”

Section: Discussionmentioning

confidence: 99%

“…The first utilization of segmented beams to increase superficial normal tissue tolerance to radiation was in grid therapy ( 1 ). The method was used in conjunction with 250-kVp orthovoltage x-rays in the early twentieth century to ameliorate the skin damage produced during radiation therapy of deeply seated tumors because of the low-dose penetration of the low-energy x-rays.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Charged Particle Therapy with Mini-Segmented Beams

et al. 2015

View full text Add to dashboard Cite

One of the fundamental attributes of proton therapy and carbon ion therapy is the ability of these charged particles to spare tissue distal to the targeted tumor. This significantly reduces normal tissue toxicity and has the potential to translate to a wider therapeutic index. Although, in general, particle therapy also reduces dose to the proximal tissues, particularly in the vicinity of the target, dose to the skin and to other very superficial tissues tends to be higher than that of megavoltage x-rays. The methods presented here, namely, “interleaved carbon minibeams” and “radiosurgery with arrays of proton and light ion minibeams,” both utilize beams segmented into arrays of parallel “minibeams” of about 0.3 mm incident-beam size. These minibeam arrays spare tissues, as demonstrated by synchrotron x-ray experiments. An additional feature of particle minibeams is their gradual broadening due to multiple Coulomb scattering as they penetrate tissues. In the case of interleaved carbon minibeams, which do not broaden much, two arrays of planar carbon minibeams that remain parallel at target depth, are aimed at the target from 90° angles and made to “interleave” at the target to produce a solid radiation field within the target. As a result, the surrounding tissues are exposed only to individual carbon minibeam arrays and are therefore spared. The method was used in four-directional geometry at the NASA Space Radiation Laboratory to ablate a 6.5-mm target in a rabbit brain at a single exposure with 40 Gy physical absorbed dose. Contrast-enhanced magnetic resonance imaging and histology 6-month later showed very focal target necrosis with nearly no damage to the surrounding brain. As for minibeams of protons and light ions, for which the minibeam broadening is substantial, measurements at MD Anderson Cancer Center in Houston, TX, USA; and Monte Carlo simulations showed that the broadening minibeams will merge with their neighbors at a certain tissue depth to produce a solid beam to treat the target. The resulting sparing of proximal normal tissue allows radiosurgical ablative treatments with smaller impact on the skin and shallow tissues. This report describes these two methods and discusses their potential clinical applications.

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Charged Particle Therapy with Mini-Segmented Beams

et al. 2015

View full text Add to dashboard Cite

show abstract

“…The former is the basis for Grid Therapy (22) and stereotactic radiosurgery, while the latter is specific for microbeams and minibeams, and is related to the fast repair of capillary blood vessels via the regeneration of angiogenic cells surviving between the microbeams. The effect was documented in the chicken chorio-allantoic membrane (12), and in the mouse brain; the latter, using 25-μm beams at 250-Gy, showed no leakage of intravenously injected FITC-dextran any time after 12 hours (13).…”

Section: Introductionmentioning

confidence: 99%

Minibeam Therapy With Protons and Light Ions: Physical Feasibility and Potential to Reduce Radiation Side Effects and to Facilitate Hypofractionation

Dilmanian

Eley

Krishnan

2015

International Journal of Radiation Oncology*Biology*Physics

View full text Add to dashboard Cite

Purpose Despite several advantages of proton therapy over megavoltage x-ray therapy its lack of proximal-tissue sparing is a concern. The method presented here adds proximal-tissue sparing to protons and light ions by turning their uniform incident beams into arrays of parallel, small or thin (0.3 mm) pencil or planar minibeams, which are known to spare tissues. As these minibeams penetrate the tissues they gradually broaden and merge with each other to produce a solid beam. Methods and Materials Broadening of 0.3-mm-diameter, 109-MeV proton pencil minibeams was measured using a stack of radiochromic films with plastic spacers. Monte Carlo simulations were used to evaluate the broadening in water of minibeams of protons and several light ions and the dose from neutron generated by collimator. Results A central parameter was the tissue depth where the beam full-width-at-half-maximum (FWHM) reached 0.7 mm, beyond which tissue sparing decrease. This depth was measured to be 22 mm for 109-MeV protons in a film-stack. It was also found by simulations a) for protons to be 23.5 mm for 109-MeV pencil minibeams and 26 mm for 116-MeV planar minibeams, and b) for light ions, all with 10-cm range in water, to increase with particle size; specifically it was 51 mm for Li-7 ions. The ~2.7% photon equivalent neutron skin dose from the collimator was reduced 7-fold by introducing a gap in between the collimator and the skin. Conclusions Proton minibeams can be implemented at existing particle therapy centers. Because they spare the shallow tissues they could augment the efficacy of proton therapy and light particle therapy particularly in treating tumors that benefit from sparing of proximal tissues such as pediatric brain tumors. They should also allow hypofractionated treatment of all tumors by allowing the use of higher incident doses with less concern about proximal tissue damage.

show abstract

“…[ 3 4 ] Using GRID therapy allowed to reduce the amount of damage by shielding a part of the field and turning it into a large number of small fields. [ 2 3 4 5 ] By introducing linear accelerators (LINACs) in the field of radiotherapy that enables to produce megavoltage beams with advantages such as good skin sparing, less scattering, sharp field edges, small penumbra and uniform spatial dose distribution,[ 6 ] the use of orthovoltage beams and subsequently GRID therapy were stopped. However, studies have recently been conducted to suggest that GRID therapy with megavoltage photons can be useful in palliative treatments of bulky tumors or in treating tumors that do not respond well to conventional radiotherapy.…”

Section: Introductionmentioning

confidence: 99%

Photoneutron dose estimation in GRID therapy using an anthropomorphic phantom: A monte carlo study

et al. 2018

View full text Add to dashboard Cite

Background:In the past, GRID therapy was used as a treatment modality for the treatment of bulky and deeply seated tumors with orthovoltage beams. Now and with the introduction of megavoltage beams to radiotherapy, some of the radiotherapy institutes use GRID therapy with megavoltage photons for the palliative treatment of bulky tumors. Since GRID can be a barrier for weakening the photoneutrons produced in the head of medical linear accelerators (LINAC), as well as a secondary source for producing photoneutrons, therefore, in terms of radiation protection, it is important to evaluate the GRID effect on photoneutron dose to the patients.Methods:In this study, using the Monte Carlo code MCNPX, a full model of a LINAC was simulated and verified. The neutron source strength of the LINAC (Q), the distributions of flux (φ), and ambient dose equivalent (H*[10]) of neutrons were calculated on the treatment table in both cases of with/without the GRID. Finally, absorbed dose and dose equivalent of neutrons in some of the tissues/organs of MIRD phantom were computed with/without the GRID.Results:Our results indicate that the GRID increases the production of the photoneutrons in the LINAC head only by 0.3%. The calculations in the MIRD phantom show that neutron dose in the organs/tissues covered by the GRID is on average by 48% lower than conventional radiotherapy. In addition, in the uncovered organs (by the GRID), this amount is reduced to 25%.Conclusion:Based on the findings of this study, in GRID therapy technique compared to conventional radiotherapy, the neutron dose in the tissues/organs of the body is dramatically reduced. Therefore, there will be no concern about the GRID effect on the increase of unwanted neutron dose, and consequently the risk of secondary cancer.

show abstract

Recent Clinical Experience with the Grid in the X-Ray Treatment of Advanced Cancer

Cited by 16 publications

References 2 publications

Charged Particle Therapy with Mini-Segmented Beams

Charged Particle Therapy with Mini-Segmented Beams

Minibeam Therapy With Protons and Light Ions: Physical Feasibility and Potential to Reduce Radiation Side Effects and to Facilitate Hypofractionation

Photoneutron dose estimation in GRID therapy using an anthropomorphic phantom: A monte carlo study

Contact Info

Product

Resources

About