|Year : 2020 | Volume
| Issue : 6 | Page : 1454-1458
Investigation of deep-seated brain tumor treatment based on Tehran research reactor new boron neutron capture therapy facility
Mohadeseh Golshanian, Yaser Kasesaz
Reactor and Nuclear Safety Research School, Nuclear Science and Technology Research Institute (NSTRI), Tehran, Iran
|Date of Submission||26-Feb-2017|
|Date of Decision||18-Jul-2017|
|Date of Acceptance||25-Feb-2018|
|Date of Web Publication||26-Oct-2018|
Reactor and Nuclear Safety Research School, Nuclear Science and Technology Research Institute (NSTRI), Tehran
Source of Support: None, Conflict of Interest: None
Aim: The main objective of this study is to evaluate the new proposed boron neutron capture therapy (BNCT) neutron beam based on the use of Tehran Research Reactor medical room to treat deep-seated brain tumors.
Material and Methods: The Snyder head phantom has been simulated through the MCNPX Monte Carlo code to calculate different dose profiles and desired medical merits. The simulation consists of the full geometry of new beamline and the phantom.
Results: The medical merits related to the new proposed BNCT beamline have a good agreement with other facilities, which indicates the potential use of this new beam for treatment of deep-seated brain tumors.
Conclusion: The obtained results show the capability of the new setup to treat deep-seated brain tumor, which was located up to ~5 cm of the skin surface.
Keywords: Boron neutron capture therapy, MCNPX Monte Carlo code, Snyder phantom, Tehran research reactor
|How to cite this article:|
Golshanian M, Kasesaz Y. Investigation of deep-seated brain tumor treatment based on Tehran research reactor new boron neutron capture therapy facility. J Can Res Ther 2020;16:1454-8
|How to cite this URL:|
Golshanian M, Kasesaz Y. Investigation of deep-seated brain tumor treatment based on Tehran research reactor new boron neutron capture therapy facility. J Can Res Ther [serial online] 2020 [cited 2021 Dec 4];16:1454-8. Available from: https://www.cancerjournal.net/text.asp?2020/16/6/1454/244206
| > Introduction|| |
Boron neutron capture therapy (BNCT) is a promising modality of radiation therapy, especially in inoperable malignant tumor treatment in which associated with a high risk of early tumor recurrence. Maintaining the normal tissue is the major concern of a cancer treatment plan during the radiation therapy. Theoretically, BNCT provides a way to selectively eliminate cancer cells and simultaneously spare normal cells., The nonradioactive10 B and thermal neutron interaction produce high linear energy transfer (LET) alpha particle and recoiling lithium-7. The lethal DNA damage occurs, due to the limited path length in tissue (~5–9 μm) of these high LET particles.,, There are some factors that have crucial role to improve BNCT process such as a proper neutron beam and10 B delivery drug. The qualified neutron beam is recommended by the International Atomic Energy Agency as presented in [Table 1]. In general, in BNCT approach, two different neutron beams are applied depends on the tumor position as follows:
|Table 1: The characteristic of neutron beam parameters based on Tehran research reactor new neutron beamline in comparison to the International Atomic Energy Agency recommended values|
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- The thermal neutron beam is limited to shallow tumors such as skin melanoma
- The epithermal neutron beam with potentially more penetration in tissue, which is used for deep-seated brain tumors.
Several studies have been performed to produce neutron beam at sufficient level intensity as a major concern of BNCT approach.,,,,,,, In Iran, Tehran Research Reactor (TRR) is the only active neutron source, which can be used practically for BNCT application.,, Recent researches show that the thermal column of TRR could be modified for shallow tumors' treatment, but it cannot be used for brain tumors., According to the prospective plan of BNCT project at TRR, the medical room has a good potential to become a new BNCT approach for the patient with brain tumors.,
The main objective of this study is to evaluate the new proposed BNCT neutron beam based on the use of TRR medical room to treat deep-seated brain tumors. To do this, the Snyder head phantom has been simulated through the MCNPX Monte Carlo code, to calculate different dose profiles and desired medical merits. The simulation consists of the full geometry of new beamline and the Snyder head phantom.
| > Materials and Methods|| |
Neutron beam features
The fission neutrons, which are generated in the core, cannot be used directly for BNCT. To prepare BNCT epithermal neutron beam, a typical Beam Shaping Assembly (BSA) consisting of moderator, reflector, collimator, thermal, and gamma neutron filter should be designed.
The new BNCT facility at TRR is an in-pool BSA, which is located between the reactor core and the medical room wall. The BSA consists of fluental as a neutron moderator, an air-filled incomplete cone as a collimator, Pb as a gamma shield and a reflector, and Cd as a thermal neutron filter as shown in [Figure 1]a. As displayed in [Table 1], the epithermal neutrons flux is approximately 2.96 × 109 (n/cm2.s) which is the appropriate neutron flux for BNCT.,
|Figure 1: (a) The schematic scheme of Beam Shipping Assembly facilty, (b) snyder head phantom with tumor. (c) Cross-section view of modified Snyder head phantom at the plane y = 0|
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Simulation of the Snyder head phantom
The analytical modified Snyder head phantom including skin, bone, and brain was applied in the geometry with surfaces are defined as follows:
The material of the phantom component including skin, skull, and brain has been driven from ICRU 46 which was presented in [Table 2]. According to [Figure 1]b, the head was located at the exit side of the beam aperture where the head was irradiated from the top of the head. Moreover, the tumor volume of around 33 cm3, which was located at 3 and 5 cm from the brain in each examination, respectively. [Figure 1] shows the MCNP simulation of the phantom including a brain tumor.
|Table 2: The head phantom components to the International Commission on Radiation Units 46|
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BNCT dose calculation
In BNCT, the radiobiological weighted dose is defined as follows:
Where, the first part arises from the thermal neutron capture on14 N. Dfast comes from the neutron elastic collision on1 H. DB is due to the boron thermal neutron capture reaction10 B (n,α)7 L i. Moreover, finally, Dγ arises both from radioactive neutron activation on1 H and from primary gamma rays in the beam. The corresponding weighting factors are presented in [Table 3]. Different concentrations of10 B have been studied as presented in [Table 4] as well.
|Table 4: In-phantom boron neutron capture therapy parameter for various10 B concentration in tumor/normal tissue|
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The dose distribution in tissue has been calculated using the following MCNP cards:
1. F4:N/E4 cards for dose rate in unit of (Gy/s).
Using these cards, one can calculate the quantity of the following form:
Where, is the neutron flux and R (E) is the dose-response function, EL and EU are the lower and upper limit of the desired energy range, respectively.
Desired medical merits
To investigate the efficiency of new proposed neutron beam, four major medical merits have been calculated through the obtain dose profiles as follows:
- Advantage depth dose rate (ADDR) is the maximum healthy tissue dose
- Therapeutic gain (TG) which is the ratio of effective tumor dose to maximum healthy tissue dose
- AD is the depth in phantom at which the TG quantity is equal to 1
- Therapeutic depth is the depth in phantom at which the TG quantity is equal to 2.
| > Results|| |
[Figure 2] illustrates the dose profiles for different components for normal and tumor brain tissues. According to the [Figure 2], the AD is obtained to be 10.5 cm and the ADDR is 105.8 cGy/min.
- [Table 4] gives the information data about the effect of various boron accumulations which are calculated in this work. As seen in [Table 4], the medical merits are dependent on boron concentration ratio. The ADDR is only depended on the boron concentration in normal tissue, while the other merits are dependent on the boron concentration in both normal and tumor tissues. [Figure 3] shows the TG for various10 B concentrations ratio. The result shows that the maximum value of TG is corresponding to 65/10 concentration ratio; however, according to other researches,, the 65/18 ratio has been selected which allow us to compare our results with similar works. It is remarkable that, the therapeutic time to reach allowed dose to normal tissue (12.5 Gy-eq,) with this ratio is about 12 min in this study
- [Figure 4]a and [Figure 4]b represent the dose distribution component for two typical cases for tumor depth in the brain (3 and 5 cm)
|Figure 3: Therapeutic gain along the center line for various boron concentrations|
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|Figure 4: Calculated various dose components in the head phantom,(a) tumor in 3-cm depth of brain (tumor/normal 18:65) (b) and tumor in 5 cm depth of brain (tumor/normal 18:65)|
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To provide a deeper understanding about the intensity of thermal flux distribution in the phantom, the useful mesh tally function of MCNP code has been used. To do this, the Snyder head phantom has been divided into 0.7 mm × 0.2 mm × 0.7 mm voxel cells, and then the thermal neutron flux has been calculated as shown in [Figure 5]
- The medical merit of this investigation and other neutron beam facilities are compared to [Table 5]. The results show that the medical merits related to the new proposed BNCT beamline have a good agreement with other facilities which indicates the potential use of this new beam for treatment of deep-seated brain tumors.
|Table 5: Comparison of in-phantom boron neutron capture therapy parameter for different boron neutron capture therapy source|
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| > Discussion|| |
The therapeutic potency of deep-seated brain tumor based on the new BNCT facility of TRR has been performed through dose estimation in Snyder head phantom. To come a deeper understanding of the thermal flux intensity, a mesh tally function of MCNP code has been used as well. The AD and TG for a deep-seated brain tumor are found to be 10.5 and 5.9 cm, respectively. The medical merits related to the new proposed BNCT beamline have a good agreement with other facilities, which indicates the potential use of this new beam for treatment of deep-seated brain tumors.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]