Neutron Capture Therapy Research Articles

Design of Moderator Assemblies for Fast, Epithermal, or Thermal Neutron–Dominated n-γ Mixed Fields Using a D-D Neutron Source

The treatment field of boron neutron capture therapy (BNCT) is a n-γ mixed field. In the Osaka University BNCT project, a material-filtered radio-photoluminescence glass dosimeter (RPLGD) was proposed for the simultaneous measurement of neutron and gamma-ray doses. In this study, to validate the material-filtered RPLGD, various types of n-γ mixed fields are designed by irradiating different moderator assemblies with a D-D neutron source at the OKTAVIAN facility, Osaka University, Japan. The n-γ mixed fields are classified into fast neutron–, epithermal neutron–, or thermal neutron–dominated fields and a gamma-ray-only field with the specific characteristics as follows: (1) the dose ratios of gamma ray to neutron are 1.0% to 977.0% for the fast neutron–dominated field, 5.0% to 921.1% for the epithermal neutron–dominated field, 5.0% to 921.1% for the thermal neutron–dominated field, and 11880.6% for the gamma-ray-only field; (2) the proportions of fast, epithermal, and thermal neutron doses to total neutron dose are 98.4% to 100.0% for the fast neutron–dominated field, 74.0% to 85.4% for the epithermal neutron–dominated field, and 90.1% to 90.8% for the thermal neutron–dominated field, respectively; and (3) the maximum gamma-ray energy is up to 12 MeV.

A Comparative Study of Neutron Shielding Performance in Al-Based Composites Reinforced with Various Boron-Containing Particles for Radiotherapy: A Monte Carlo Simulation

This study aimed to assess and compare the shielding performance of boron-containing materials for neutrons generated in proton therapy and used in boron neutron capture therapy (BNCT). Five composites, including AlB2, Al-B4C, Al-TiB2, Al-BN, and Al-TiB2-BN, were selected as shielding materials, with concrete used as a benchmark. The mass fraction of boron compounds in these materials ranged from 10% to 50%. The Monte Carlo toolkit Geant4 was employed to calculate shielding parameters, including neutron ambient dose equivalent, dose values, and macroscopic cross-section. Results indicated that, compared to concrete, these boron-containing materials more effectively absorb thermal neutrons. When the boron compound exceeds 30 wt.%, these materials exhibit better shielding performance than concrete of the same thickness for neutrons generated by protons. For a given material, its shielding capability increases with boron content. Among the five materials when the material thickness and boron compound content are the same, the shielding performance for neutrons generated by protons, from best to worst, is as follows: Al-TiB2, Al-B4C, AlB2, Al-TiB2-BN, and Al-BN. For BNCT, the shielding performance from best to worst is in the following order: Al-B4C, AlB2, Al-TiB2, Al-TiB2-BN, and Al-BN. The results of this study provide references and guidelines for the selection and optimization of neutron shielding materials in proton therapy and BNCT facilities.

Comparative Study of Cytotoxicity and Accumulation of Boron and Lithium-Containing Drugs in Skin Melanoma Cells In Vitro.

We studied cytotoxicity and accumulation of boron and lithium by cultured human fibroblasts and human and mouse skin melanoma cell cultures. The cytotoxicity of boron and lithium drugs was assessed by MTT tests in the boron and lithium concentration range of 10-640 μg/ml. Cell viability was significantly reduced after incubation with boron and lithium at concentrations >160 μg/ml. To assess accumulation of boron and lithium, the concentration of elements was measured using inductively coupled plasma atomic emission spectrometry. Melanoma cells more intensively accumulated lithium in comparison with boron. The results indicate the possibility of safe application of lithium salts in concentrations minimally required for successful neutron capture therapy.

Development of an online neutron beam monitoring system for accelerator-based boron neutron capture therapy in a hospital.

Boron neutron capture therapy (BNCT) is a next-generation radiotherapy, utilizing both an external neutron beam and a -containing pharmaceutical. A compact accelerator for a high intensity neutron source was installed to conduct BNCT in a hospital. The dose administered to a patient was evaluated by measuring the proton beamcurrent. Neutron intensity should be monitored in real-time by measuring the neutrons emitted from the target during BNCT irradiation. This is crucial due to potential neutron target degradation. Online neutron beam monitoring systems are required for reliable measurements of the administered neutron dose. An online neutron beam monitoring system was developed to monitor neutron intensity irradiating on the patient at the National Cancer Center Hospital (NCCH). The neutron detector comprised a back-illuminated thin Si diode of 40- thickness and an ultrathin natural LiF neutron converter of 0.05- thickness. The neutron detector was installed on the neutron target unit, regardless of whether a patient was present, without any additional modifications to the setup. The response functions for high photon dose rates of upto 100 Gy/h were measured. The pulse heights were measured using the neutron beam monitor during BNCT neutron irradiation. Neutron temporal response measured using the online beam monitor was acquired and compared with the proton beam current and the measurements at a patient position. From this measurement at the patient position, the neutron fluence rate irradiating on a patient wasobtained. The neutron events were separated from the photon events. The neutron counting rates increased rapidly with the starting of proton beam irradiation and dropped to zero upon its termination. During intermittent drops and recoveries in the proton beam, the neutron beam monitor for counting rates responded quickly, synchronizing with the beam current. A scatter plot of the neutron counting rate and proton beam current indicated a good linear correlation. A direct relationship between the online neutron beam monitor's neutron counting rates and those of the patient neutron detector showed a good correlation coefficient of 0.84. A ratio of the both neutron counting rates showed a standard deviation of 6%. The correlation coefficient and standard deviation were improved to 0.94 and 1.5%, by re-binning the neutron temporal response with longer acquisition period than 1 s. Using the online neutron beam monitor, the neutron fluence rate was obtained from the direct relationship within 1.5%. Therefore, real-time monitoring of neutron intensity was achieved within the acceptable level as per the International Commission on Radiation Units and Measurementsreport. The online neutron beam monitoring system was developed to monitor the BNCT neutron beam intensity at NCCH. The temporal response of the neutron beam monitor was synchronized with the neutron counting rate at the patient position. Using the online neutron beam monitor, the neutron fluence rate irradiating on the patient can be monitored from the direct relationship. Fluctuation of the neutron beam intensity through BNCT irradiation and the degradation of the lithium target through the lifespan of the neutron target could be monitored using the neutron beammonitor.

A novel quantitative method for the determination of 10B-carrier boronophenylalanine in rat plasma by UHPLC-MS/MS and comparison with ICP-MS

L-Boronophenylalanine (BPA), a widely used 10B carrier for clinical boron neutron capture therapy (BNCT), was quantified in rat plasma through a simple, effective and stable ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method. Chromatographic separation was performed on an ACQUITY UPLC HSS T3 (100 mm × 2.1 mm, 1.8 μm) column with the mobile phase of 0.5 % formic acid aqueous solution and acetonitrile. For the detector, the m/z ion pairs used for quantification were 209.1→120.1 for BPA and 210.1→120.1 for internal standard in a positive mode by electrospray ionization (ESI) using multiple reaction monitoring (MRM). The method is specific and robust with rare affection by endogenous substances in the matrix. A good linear relationship was observed over 80–80000 ng/mL (r2 = 0.9993). The values of inter- and intra-day accuracy and precision were within the acceptance criteria of ±15 %. BPA was found to be stable under different experimental conditions. This developed method was successfully applied on a pharmacokinetic experiment on Sprague-Dawley rats (intravenous injection, 125 mg/kg) and a comparation between UHPLC-MS/MS and ICP-MS for BPA was carried out.

Medical staffs' required capability and workload for accelerator-based boron neutron capture therapy: correspondence.

Medical staffs' required capability and workload for accelerator-based boron neutron capture therapy: correspondence.

Thermal cross section of poly(2-hydroxyethyl methacrylate) hydrogels for neutron dose calculation

Phantom materials are used to design radiation safety and protection strategies by means of numerical dose calculation. In the case of thermal neutrons, the radiation transport in the phantom relies on mass attenuation coefficients and total cross sections which are dependent on the physical and chemical properties of the material. Specifically for medical applications, such as neutron capture therapy, the neutron-induced dose is mainly related to the neutron absorption by hydrogen and nitrogen in the human tissue and body. Here, we investigate the use of poly(2-hydroxyethyl methacrylate) as a phantom material by experimental measurement and modeling of its total neutron scattering cross section and mass attenuation coefficient. We show that by varying the hydration level from 10 to 40 w%, one can obtain a neutron attenuation coefficient similar to polymethyl methacrylate or more representative of the human body, respectively. By benchmarking our phenomenological model on the experimental data, we provide a new example of how to use the average functional group approximation to accurately model total neutron cross sections in the framework of personalized medicine approaches.

Boron Agent Delivery Platforms Based on Natural Products for Boron Neutron Capture Therapy.

Boron neutron capture therapy (BNCT) is one of the most promising modalities for cancer treatment due to its minimal invasiveness. Although two types of boron agents are clinically used, several issues persist in their delivery, including poor water solubility, instability in aqueous media, selectivity toward cancer cells, accumulation in cancer cells, retention time in tumor tissue, and efficiency in achieving the boron neutron capture reaction. Addressing these challenges, numerous groups have explored various boron agents to enhance the therapeutic benefits of BNCT. This review summarizes delivery platforms based on natural products for BNCT.

Cobaltabis(Dicarbollide) [o-COSAN]- for Boron Neutron Capture Therapy of Head and Neck Cancer: Biodistribution and Irradiation Studies in an Experimental Oral Cancer Model.

Boron neutron capture therapy (BNCT) is a tumor-selective particle radiotherapy that combines preferential boron accumulation in tumors and neutron irradiation. Based on previous studies in tumor-bearing mice, this study evaluated the biodistribution of the sodium salt of cobaltabis(dicarbollide) (Na[3,3'-Co(C2B9H11)2], abbreviated as Na[o-COSAN]) in the hamster cheek pouch oral cancer model and the Na[o-COSAN]/BNCT therapeutic effect on tumors and induced radiotoxicity. The synthesis and comprehensive characterization of 10B-enriched trimethylammonium salt of nido-[7,8-C210B9H12]-o-carborane, along with the cesium and sodium salts of [o-10COSAN] cobaltabis(dicarbollide) are reported here for the first time. Hamsters bearing tumors were injected with Na[o-COSAN] (7.5 mg B/kg) and euthanized at different time-points after injection (30 min, 2, 3, 5, and 18 h post-administration) to evaluate boron uptake in different tissues/organs. Based on these results, tumor-bearing animals were treated with Na[10B-o-COSAN]/BNCT (7.5 mg B/kg b.w., 3 h), prescribing 5 Gy total in absorbed dose to the precancerous tissue surrounding tumors, i.e., the dose-limiting tissue. Na[o-10COSAN] exhibited no toxicity. Although biodistribution studies employing Na[o-COSAN] have shown low absolute boron concentration in the tumor (approx. 11 ppm), Na[o-10COSAN]/BNCT induced a high and significant therapeutic effect on tumors versus the control group (cancerized, untreated animals). Moreover, only half of the animals exhibited severe mucositis in the precancerous dose-limiting tissue after BNCT, which resolved completely at 21 days after irradiation. Na[o-10COSAN] would be potentially useful to treat head and neck cancer with BNCT.

Assessing the biological effects of boron neutron capture therapy through cellular DNA damage repair model.

Boron neutron capture therapy (BNCT) is a targeted radiotherapy that relies on the 10B (n, α) 7Li reaction, which produces secondary particles with high linear energy transfer (LET), leading to a high relative biological effectiveness (RBE) in tumors. The biological effectiveness of BNCT is influenced by factors such as boron distribution and concentration, necessitating improved methods for assessing its radiobiological effects and clarifying the sensitivity of the differences in different factors to the biological effects. This paper introduces a method to evaluate the biological effects of BNCT using the cellular repair model. This method aims to overcome some of the limitations of current evaluation approaches. The primary goal is to provide guidance for clinical treatments and the development of boron drugs, as well as to investigate the impact of the synergistic effects of mixed radiation fields in BNCT on treatment outcomes. The approach involves three key steps: first, extending the radial energy deposition distribution of BNCT secondary particles using Geant4-DNA. This allows for the calculation of initial DNA double-strand breaks (DSBs) distributions for a given absorbed dose. Next, the obtained initial DSB distributions are used for DNA damage repair simulations to generate cell survival curves, then thereby quantifying RBE and compound biological effectiveness (CBE). The study also explores the synergistic effects of the mixed radiation fields in BNCT on assessing biological effects were also explored in depth. The results showed that the RBE of boronophenylalanine (BPA) and sodium borocaptate (BSH) drugs at cell survival fraction 0.01 was 2.50 and 2.15, respectively. The CBE of the boron dose component was 3.60 and 0.73, respectively, and the RBE of the proton component was 3.21, demonstrating that BPA has a significantly higher biological impact than BSH due to superior cellular permeability. The proton dose significance in BNCT treatment is also underscored, necessitating consideration in both experimental and clinical contexts. The study demonstrates that synergistic effects between disparate radiation fields lead to increased misrepairs and enhanced biological impact. Additionally, the biological effect diminishes with rising boron concentration, emphasizing the need to account for intercellular DNA damage heterogeneity. This methodology offers valuable insights for the development of new boron compounds and precise assessment of bio-weighted doses in clinical settings and can be adapted to other therapeutic modalities.

Preliminary study of a compact epithermal neutron absolute flux intensity measurement system for real-time in-vivo dose monitoring in boron neutron capture therapy

Boron neutron capture therapy (BNCT) is a radiotherapy technology that selectively kills tumor cells via the 10B(n, α)7Li reactions. Epithermal neutrons (0.5 eV–10 keV) are emitted and converted into thermal neutrons, which have a larger neutron capture reaction cross-section, by slowing down in the human body before reaching the tumor. Recently, the development of an epithermal neutron absolute flux intensity measurement technique has become crucial for real-time in-vivo dose monitoring in BNCT. In this study, a concept for a measurement system consisting of multiple compact scintillator with optical fibers detectors covered with neutron absorbers of various thicknesses is proposed. The designed system achieves a consistent response to epithermal neutrons with a theoretical coefficient of variation not higher than 5% for both LiCAF and EJ-254 scintillators. The theoretical feasibility of the proposed measurement system was investigated by an irradiation experiment carried out at the heavy water neutron irradiation facility at the Kyoto University Reactor. The experimental results indicated that further improvement and refinement are necessary to meet the high accuracy and precision required for real-time dose monitoring in clinical applications.

Cobaltabis(dicarbollide) Interaction with DNA Resolved at the Atomic Scale.

Boron neutron capture therapy represents a promising avenue for cancer treatment that requires nontoxic drugs with a high boron content efficiently distributed into cancerous cells. The metallacarborane o-cobaltabis(dicarbollide) ([COSAN]-) fulfills these requirements and constitutes an attractive candidate. Nevertheless, the interaction of this promising drug with nucleic acids, the assumed target of the biological damage, is poorly understood since contradictory results are reported in the literature. This work establishes the DNA/[COSAN]- interaction strength, mechanism, and time scale at the atomistic level by using a combination of microsecond-molecular dynamics and hybrid quantum mechanics/molecular mechanics simulations and by quantifying the absolute binding free energy. Results show that the DNA/[COSAN]- interaction is highly dependent on the ionic strength of the medium. A relatively weak DNA major groove binding (ΔGbind= -2.49 kcal/mol) driven mostly by dihydrogen B-H···H-N bonding is observed in the simulations only at a high NaCl concentration, whereas DNA intercalation mode is deemed highly unlikely.

Luminescence Modulation in Boron-Cluster-Based Luminogens via Boron Isotope Effects.

Recent advances in luminescent materials highlight the significant impact of hydrogen isotope effects on improving optoelectronic properties. However, the research on the influence of the boron isotope effects on photophysical properties remains underdeveloped. This study focused on exploring the boron isotope effects in boron-cluster-based luminogens. In doing so, we designed and synthesized carborane-based luminogens containing 98% 10B and 95% 11B, respectively, and observed distinct photophysical behaviors. Compared to the 10B-enriched luminogens, the 11B-enriched counterparts can significantly enhance luminescence efficiency, prolong emission lifetime, and reduce full-width at half-maximum. Additionally, increased thermal stability, redshifted B-H vibrations, and a fourfold enhanced electrochemiluminescence intensity have also been observed. On the other hand, the biological assessments of a 10B-enriched luminogen reveals low cytotoxicity, high boron uptake, and excellent fluorescence imaging capability, indicating the potential application in boron neutron capture therapy (BNCT). This work presents the first comprehensive exploration on the boron isotope effects in boron clusters, and provides valuable insights into the rational design of organic luminogens for advanced optoelectronic and biomedical applications.

Luminescence Modulation in Boron‐Cluster‐Based Luminogens via Boron Isotope Effects

Recent advances in luminescent materials highlight the significant impact of hydrogen isotope effects on improving optoelectronic properties. However, the research on the influence of the boron isotope effects on photophysical properties remains underdeveloped. This study focused on exploring the boron isotope effects in boron‐cluster‐based luminogens. In doing so, we designed and synthesized carborane‐based luminogens containing 98% 10B and 95% 11B, respectively, and observed distinct photophysical behaviors. Compared to the 10B‐enriched luminogens, the 11B‐enriched counterparts can significantly enhance luminescence efficiency, prolong emission lifetime, and reduce full‐width at half‐maximum. Additionally, increased thermal stability, redshifted B–H vibrations, and a fourfold enhanced electrochemiluminescence intensity have also been observed. On the other hand, the biological assessments of a 10B‐enriched luminogen reveals low cytotoxicity, high boron uptake, and excellent fluorescence imaging capability, indicating the potential application in boron neutron capture therapy (BNCT). This work presents the first comprehensive exploration on the boron isotope effects in boron clusters, and provides valuable insights into the rational design of organic luminogens for advanced optoelectronic and biomedical applications.

Effect of neutron beam properties on dose distributions in a water phantom for boron neutron capture therapy.

From the viewpoints of the advantage depths (ADs), peak tumor dose and skin dose, we evaluated the effect on the dose distribution of neutron beam properties, namely the ratio between thermal and epithermal neutron fluxes (thermal/epithermal ratio), fast neutron component and γ-ray component. Several parameter surveys were conducted with respect to the beam properties of neutron sources for boron neutron capture therapy assuming boronophenylalanine as the boron agent using our dose calculation tool, called SiDE. The ADs decreased by 3% at a thermal/epithermal ratio of 20-30% compared with the current recommendation of 5%. The skin dose increased with the increasing thermal/epithermal ratio, reaching a restricted value of 14 Gyeq at a thermal/epithermal ratio of 48%. The fast neutron component was modified using two different models, namely the 'linear model', in which the fast neutron intensity decreases log-linearly with the increasing neutron energy, and the 'moderator thickness (MT) model', in which the fast neutron component is varied by adjusting the MT in a virtual beam shaping assembly. Although a higher fast neutron component indicated a higher skin dose, the increment was <10% at a fast neutron component of <1 × 10-12Gycm2 for both models. Furthermore, in the MT model, the epithermal neutron intensity at a fast neutron component of 6.8 × 10-13Gycm2 was 41% higher compared with that of 2 × 10-13Gycm2. The γ-ray component also caused no significant disadvantages up to several times larger compared with the current recommendation.

Borane-Mediated Polyhedral Expansion to Access Metal-Free Neutral and Cationic Derivatives of closo-Heptaboranes.

Boranes with closed polyhedral structures feature peculiar bonding and structural characteristics, rendering them widely applicable in diverse research areas ranging from basic functionalization reactions to applications such as medicine, nanomaterials, molecular electronics, and neutron capture therapy. Among the closed borane family, the neutral and cationic heptaborane B7 clusters have been missing in contemporary boron cluster chemistry to date. Herein, we report a polyhedral expansion protocol to construct a neutral derivative of closo-heptaborane (B7) from closo-hexaborane (B6) mediated by borane. Conversion of the neutral derivative of closo-heptaborane to a cationic derivative is also demonstrated. X-ray crystallographic and spectroscopic analyses with the aid of quantum chemical calculations reveal that both neutral and cationic derivatives of closo-heptaborane exhibit a pentagonal-bipyramidal geometry and involve the delocalized σ skeletal electrons, leading to three-dimensional aromaticity. Moreover, the B7 core of the former undergoes a complexation reaction with silver tetrafluoroborate, representing the first experimental demonstration of the nucleophilic nature of the closo-heptaborane.

Retrospective analysis of treatment-positioning accuracy and dose error in boron neutron capture therapy using a sitting-position treatment system for head and neck cancer

The neutron beam in boron neutron capture therapy (BNCT) exhibits poor directionality and significantly decreasing neutron flux with increasing distance. Therefore, the treatment site must be close to the irradiation aperture. Some patients with head and neck cancer may benefit from a sitting-position setup. The study aim was to evaluate the treatment-positioning accuracy and dose error in sitting patients receiving BNCT. Thirty-two patients with head and neck cancer who underwent sitting-position BNCT at Southern Tohoku BNCT Research Center were included in the study. Horizontal (ΔX) and vertical (ΔY) errors were defined as the displacement between the treatment planning system (TPS) digital reconstructed radiograph and the pre-treatment X-ray image. Using in-house software, image matching was performed. The beam-axial directional (ΔZ) error was compared with the parameters entered into the TPS and the actual pre-treatment measured values. The translational-position error was reflected in the TPS’s patient coordinate system with respect to the reference plan. Re-dose calculations were performed to evaluate the effect of positional error on tumor and normal-tissue doses. The [ΔX, ΔY, ΔZ] DRR-CR mean ± 1SD were − 0.40 ± 2.0, 0.30 ± 2.3, and − 1.4 ± 1.5 mm, respectively. The Dmean and D98% tumor-dose errors were 1.22 % ± 1.44 % and 0.99 % ± 1.63 %, respectively. The D2% pharyngeal and oral mucosal-dose errors were 0.98 % ± 1.91 % and 1.21 % ± 1.78 %, respectively. The tumor- and normal-tissue dose errors were typically < 5 %. High-precision treatment was feasible in sitting-positioned BNCT.

Synthesis and mechanistic investigation of BPA fluorescent probes targeting BPA for potential application in Boron Neutron Capture Therapy (BNCT)

Boronic acid analogs are crucial in modern organic chemistry and drug development, serving as versatile reagents and intermediates with significant therapeutic applications. This area has gained increased interest with the recent development of the drug 4-boron-L-phenylalanine (L-BPA) for boron neutron capture therapy (BNCT). Fluorescent probe technology offers an essential pathway for imaging drugs in vitro and in vivo, providing high sensitivity with great spatial and temporal resolution for both disease diagnosis and drug development. In this paper, we designed and investigated three fluorescent probes—W-1-NN, W-2-NS and W-3-NO—for sensing 4-boron-L-phenylalanine (L-BPA). Among these, only W-1-NN reacts with L-BPA, resulting in a spectral blue-shift change. This probe can “ratiometrically” and specifically detect L-BPA among various metals, with a limit of detection (LOD) of 7.11 μM. Mechanistic studies revealed that the addition of L-BPA disrupts the inherent ESIPT mechanism of W-1-NN in protonic solutions, resulting in the appearance of a new peak at 372 nm. Additionally, theoretical computational studies have also demonstrated that the complexation of W-1-NN with L-BPA triggers a change in the resonance structure, resulting in a larger energy gap and causing a blue shift in the spectrum. Furthermore, W-1-NN has been successfully applied to the detection of L-BPA in human urine. Therefore, the template probe with N/O as the target and the introduction of N atoms can specifically detect L-BPA. This template probe lays the foundation for the detection of L-BPA, and provides great possibilities for the future realization of the template probe to be connected with different fluorophores to make it emit at long wavelengths to reach the target of the near-infrared.

Use of a Xenon Gamma Spectrometer for Dosimetry in Boron–Neutron Capture Therapy

Use of a Xenon Gamma Spectrometer for Dosimetry in Boron–Neutron Capture Therapy

Computational assessment dose distribution of the antero-posterior and postero-anterior in Boron Neutron Capture Therapy for colorectal cancer

Abstract Colorectal is part of the gastrointestinal system that anatomically and physiologically, is excretory and extends throughout the abdominal region. In BNCT (Boron Neutron Capture Therapy) treatment for colorectal cancer, special projections are needed to ensure the dose is distributed effectively in cancer cells. Computational evaluation was carried out using PHITS 3.30 version, to determine the number of doses for organs at risk in the Antero-Posterior (AP) projection compared to the Postero-Anterior (PA) projection in this case, if the cancer cells are located in different parts, there are rectum and colon (transverse). BNCT treatment planning was designed using a female abdomen phantom voxel with the patient position Left Lateral Decubitus. Based on the simulation and evaluation results, it’s confirmed that isoeffective dose and irradiation time examined in the rectum is significantly reduced in the postero-anterior position so that postero-anterior and antero-posterior calculation results are 0.74 Gy and 20.61 Gy. However, if the cancer cells are in the transverse colon, antero-posterior projection is more effective for cases of colon cancer in the transverse colon of 0.71 Gy, and the postero-anterior projection with a dose of 29.15 Gy.