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Charged Particle Therapy with Mini-Segmented Beams.

Dilmanian FA, Eley JG, Rusek A, Krishnan S - Front Oncol (2015)

Bottom Line: 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 resulting sparing of proximal normal tissue allows radiosurgical ablative treatments with smaller impact on the skin and shallow tissues.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiation Oncology, Health Sciences Center, Stony Brook University , Stony Brook, NY , USA ; Department of Neurology, Health Sciences Center, Stony Brook University , Stony Brook, NY , USA ; Department of Radiology, Health Sciences Center, Stony Brook University , Stony Brook, NY , USA.

ABSTRACT
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.

No MeSH data available.


Related in: MedlinePlus

Schematic view of the rabbit head irradiated with four-directional interleaved carbon minibeams.
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Figure 4: Schematic view of the rabbit head irradiated with four-directional interleaved carbon minibeams.

Mentions: Figure 4 shows the schematic view of the four-directional interleaved carbon ion minibeams used to ablate a 6.5-mm target in a rabbit brain (18). The details were the following. The minibeams’ incident-beam thickness was 0.3 mm, and their beam spacing on-center was 1.05 mm on-center; this spacing was much larger than twice the incident-beam thickness to accommodate the gradual minibeam broadening in tissues. Figure 5 shows a “to-scale” presentation of two of the four carbon minibeam arrays used in the study. The study used 124–135 MeV/nucleon carbon energies to create the spread-out-Bragg-peak (SOBP). The total dose produced at the target from all four directions in the SOBP was 40 Gy physical absorbed dose, which corresponds to 120 photon-equivalent Gy (GyE) using an average relative biological effectiveness value of 3.0 at the target. The following dosimetry account shows that this dose was produced by minibeams of 14 Gy in-beam incident physical dose in each of the four interleaving arrays. First, it was shown (18) that the particular geometry involving 14 Gy “pedestal” incident dose leads to 20 Gy physical dose at the SOBP. Therefore, the target dose would have been 20 Gy (and not 40 Gy) if we had only two interleaving arrays (see Figure 2B for geometry). The 40-Gy physical target dose was produced by virtue of having a four-directional incident-beam geometry (Figure 2C).


Charged Particle Therapy with Mini-Segmented Beams.

Dilmanian FA, Eley JG, Rusek A, Krishnan S - Front Oncol (2015)

Schematic view of the rabbit head irradiated with four-directional interleaved carbon minibeams.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4664668&req=5

Figure 4: Schematic view of the rabbit head irradiated with four-directional interleaved carbon minibeams.
Mentions: Figure 4 shows the schematic view of the four-directional interleaved carbon ion minibeams used to ablate a 6.5-mm target in a rabbit brain (18). The details were the following. The minibeams’ incident-beam thickness was 0.3 mm, and their beam spacing on-center was 1.05 mm on-center; this spacing was much larger than twice the incident-beam thickness to accommodate the gradual minibeam broadening in tissues. Figure 5 shows a “to-scale” presentation of two of the four carbon minibeam arrays used in the study. The study used 124–135 MeV/nucleon carbon energies to create the spread-out-Bragg-peak (SOBP). The total dose produced at the target from all four directions in the SOBP was 40 Gy physical absorbed dose, which corresponds to 120 photon-equivalent Gy (GyE) using an average relative biological effectiveness value of 3.0 at the target. The following dosimetry account shows that this dose was produced by minibeams of 14 Gy in-beam incident physical dose in each of the four interleaving arrays. First, it was shown (18) that the particular geometry involving 14 Gy “pedestal” incident dose leads to 20 Gy physical dose at the SOBP. Therefore, the target dose would have been 20 Gy (and not 40 Gy) if we had only two interleaving arrays (see Figure 2B for geometry). The 40-Gy physical target dose was produced by virtue of having a four-directional incident-beam geometry (Figure 2C).

Bottom Line: 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 resulting sparing of proximal normal tissue allows radiosurgical ablative treatments with smaller impact on the skin and shallow tissues.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiation Oncology, Health Sciences Center, Stony Brook University , Stony Brook, NY , USA ; Department of Neurology, Health Sciences Center, Stony Brook University , Stony Brook, NY , USA ; Department of Radiology, Health Sciences Center, Stony Brook University , Stony Brook, NY , USA.

ABSTRACT
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.

No MeSH data available.


Related in: MedlinePlus