Gamma-ray stereotactic radiosurgery systems available commercially contain either stationary or rotational source configuration. Rotational systems reduce the number of sources utilized and can also provide beneficial dosimetric properties. In this study, we explore the dosimetric advantage of a novel rotating gamma-ray design for stereotactic body radiotherapy (SBRT) as compared to the well-established CyberKnife system. CybeRay (OUR United Corp., Xian, China) is a rotating gamma-ray system (RGS). Its treatment head can rotate 360° in the axial plane and swing 35° in the superior direction. It includes 13 Co-60 sources focusing on the isocenter. The RT Pro planning system (Prowess, Concord, CA) was used for CybeRay treatment planning, while the Multiplan software (Accuray, Sunnyvale, CA) was used for CyberKnife treatment planning. Twelve SBRT patients previously treated with CyberKnife were re-planned for CybeRay, and their treatment plans were compared based on isodose distributions, dose volume histograms, conformity index (CI), and the estimated treatment time. The planning target volume ranged from 4.4 to 124.2 cc. Both treatment systems provided excellent SBRT plans that meet our clinical acceptance criteria. The mean value of CI was 1.25 for both CyberKnife and CybeRay (p = 0.03). The estimated treatment delivery time for the CyberKnife plans ranged from 13 to 53 min as compared to 6 to 54 min with CybeRay (p = 0.02). CybeRay was superior concerning peripheral doses appearing as excessive isodose lines extending to distal normal tissues. The new CybeRay machine showed promising dosimetric capabilities for stereotactic radiosurgery and radiotherapy of extra- and intra-cranial lesions.

Purpose The trend today in modern radiation therapy is toward conformal therapy with segmented or moving field techniques. Generally, this requires multifield irradiation or the use of arc/rotation therapy. Many authors have pointed out in literature that if the Co-60 machines were modernized with state of the art devices, it may be able to provide similar quality of radiation therapy as provided by linacs. Co-60 units will have the advantage of having more simple and robust design, and minimal maintenance and technical expertise to operate the machine as compared to the technologically complex linacs. Thus, in this work we conduct a dosimetric comparison between conformal arc utilizing Co-60 beams and that utilizing 6MV beam energy. Material and methods CT scans was unarchived for patient previously treated by SBRT in our department. We selected lung, breast, and head and neck cases. All of these cases were previously planned on Eclipse planning system (Varian, Palo Alto, Medical Systems). We regenerated treatment plans using conformal arcs with the arc being modeled by delivery of multiple conformal beams. Dose distributions for all plans were calculated using Monte Carlo simulation for both 6MV and Co-60 beam energies. Results As the number of fields increases, advantage of higher energies over lower radiation energies decreases. In all studied cases, conformal arc plans utilizing Co-60 beam was achieving almost same conformity when compared to the 6Mv plans. Isodose distributions were tailored similarly around the PTV. On reviewing the minimum and maximum dose reaching all targets, it was shown that both Co-60 and 6Mv plans was achieving our clinical acceptation criteria for the target coverage. The DVH of Co-60 plans were showing slightly lower dose to critical structures however the difference was small in most cases. Conclusion Our results have shown the potential for newly designed Co-60 machines as a modality that could treat a good fraction of cancer patients. The overall performance seen in the conformal arcs using Co-60 beams was encouraging as being compared to the 6MV conformal arcs. There was no significant superiority detected for the 6MV plans over the Co-60 plans for SBRT cases. The trend today in modern radiation therapy is toward conformal therapy with segmented or moving field techniques. Generally, this requires multifield irradiation or the use of arc/rotation therapy. Many authors have pointed out in literature that if the Co-60 machines were modernized with state of the art devices, it may be able to provide similar quality of radiation therapy as provided by linacs. Co-60 units will have the advantage of having more simple and robust design, and minimal maintenance and technical expertise to operate the machine as compared to the technologically complex linacs. Thus, in this work we conduct a dosimetric comparison between conformal arc utilizing Co-60 beams and that utilizing 6MV beam energy. CT scans was unarchived for patient previously treated by SBRT in our department. We selected lung, breast, and head and neck cases. All of these cases were previously planned on Eclipse planning system (Varian, Palo Alto, Medical Systems). We regenerated treatment plans using conformal arcs with the arc being modeled by delivery of multiple conformal beams. Dose distributions for all plans were calculated using Monte Carlo simulation for both 6MV and Co-60 beam energies. As the number of fields increases, advantage of higher energies over lower radiation energies decreases. In all studied cases, conformal arc plans utilizing Co-60 beam was achieving almost same conformity when compared to the 6Mv plans. Isodose distributions were tailored similarly around the PTV. On reviewing the minimum and maximum dose reaching all targets, it was shown that both Co-60 and 6Mv plans was achieving our clinical acceptation criteria for the target coverage. The DVH of Co-60 plans were showing slightly lower dose to critical structures however the difference was small in most cases. Our results have shown the potential for newly designed Co-60 machines as a modality that could treat a good fraction of cancer patients. The overall performance seen in the conformal arcs using Co-60 beams was encouraging as being compared to the 6MV conformal arcs. There was no significant superiority detected for the 6MV plans over the Co-60 plans for SBRT cases.

Cobalt beams have exhibited superior dosimetric advantages for stereotactic radiosurgery/radiation therapy (SRS/SRT) of intracranial tumors compared to higher energy megavoltage x-ray beams due to the noncoplanar multiple source arrangement and the rapid dose falloff as a result of lower secondary electron energies. This work investigates the potential clinical benefits of cobalt beams for stereotactic body radiation therapy (SBRT) of lung cancer by Monte Carlo simulations of a novel SRS/SBRT machine design with superior dose conformity/gradient and accurate stereotaxy. A new commercially available SRS/SBRT system consists of a ring gantry with 2 cobalt treatment heads: 1 is a focusing head with 16 gamma sources and the other is a diverging gamma source equipped with an adjustable primary collimator and a multileaf collimator (MLC). The MLC has 60 paired leaves, and the maximum field size is either 40 cm x 40 cm (40 pairs of 0.5-cm central leaves, 20 pairs of 1-cm outer leaves). The treatment heads can swing 35° superiorly and 8° inferiorly, allowing a total of 43° noncoplanar beam incident. The treatment couch provides 6-degrees-of-freedom motion compensation, and the kV cone beam CT (CBCT) system has a spatial resolution of 0.4 mm. Monte Carlo simulations were performed to obtain dose distributions and compare with measurements. A retrospective study of 79 previously treated patients was performed to compare cobalt beams with 6-MV x-ray beams on robotic radiosurgery and linear accelerator SBRT systems for thoracic treatments. Monte Carlo results confirmed the new cobalt system design parameters including output factors and 3D dose distributions. Its beam penumbra/dose gradient was similar to or better than that of 6-MV photon beams with variable primary collimator sizes that also resulted in adjustable dose rates required for treatment optimization and plan delivery. The new cobalt system had a 0.3-mm isocenter accuracy. The low-dose acquisition mode of the CBCT system provided fluoroscopy and 3D imaging at a dose level 3 times less than conventional CBCT systems. Since cobalt beams produced lower energy secondary electrons, the new cobalt SRS/SBRT system exhibited better dose properties in low-density lung tissues. Because of their rapid depth dose falloff, cobalt beams were favorable for peripheral lung tumors with partial-arc deliveries to spare the opposite lung and critical structures. The skin dose from cobalt beams was only 2% to 3% higher than that from 6-MV x-ray beams. Superior treatment plans were obtained using the focusing cobalt treatment head for small (up to 50 mL) tumor volumes and using the cobalt MLC treatment head for large (>30 mL) tumor volumes for more than 70% of the patients investigated compared to high-energy x-ray beams. The unique dosimetric properties of cobalt beams and the accurate stereotaxy/dose delivery make the new cobalt design an ideal system for advanced SRS/SBRT as well as conventional RT of lung cancers.

Introduction A new design of Gamma Knife consist of 30 60C0 source capsules, two circular primary collimators (diameter of 6.60 mm and 6.10 mm) and four different changeable collimators. The sources (diameter of 2.8 mm) are distributed in six groups of five sources in the spherical geometry. Each source is individually collimated to obtain four different circular fields at the isocenter (3 mm, 3.5 mm, 6 mm and 8 mm). Purpose To determine the characteristics of the Co60 beam emerging from a new design of Gamma Knife system and to calculate dose distributions at the isocenter distance for different source configurations and collimator openings Materials and methods We have used the BEAM-Monte Carlo code to realistically model the geometry design, including source capsules, primary and secondary collimators. The shielding of the head was also simulated. The dose distributions at the isocenter distance are calculated using GEPTS in a previous designed spherical component module for the circular field sizes studied. Results The spectra of particles emerging from each source-collimator configuration is calculated.The radial photon fluence does not vary significantly inside the collimator openings. The spectra of particles from different source groups are compared. Conclusion The 60Co beam emerging from each group source configuration was characterized but our preliminary results do not allow to properly determine the variation of spectra of particles at isocenter as function of source group position. Further investigations are needed.

Purpose: Dose-volume-histogram (DVH) is widely used for plan evaluation in radiation treatment. The concept of dose-mass-histogram (DMH) is expected to provide a more representative description as it accounts for heterogeneity in tissue density. This study is intended to assess the difference between DVH and DMH for evaluating treatment planning quality. Methods: 12 lung cancer treatment plans were exported from the treatment planning system. DVHs for the planning target volume (PTV), the normal lung and other structures of interest were calculated. DMHs were calculated in a similar way as DVHs expect that the voxel density converted from the CT number was used in tallying the dose histogram bins. The equivalent uniform dose (EUD) was calculated based on voxel volume and mass, respectively. The normal tissue complication probability (NTCP) in relation to the EUD was calculated for the normal lung to provide quantitative comparison of DVHs and DMHs for evaluating the radiobiological effect. Results: Large differences were observed between DVHs and DMHs for lungs and PTVs. For PTVs with dense tumor cores, DMHs are higher than DVHs due to larger mass weighing in the high dose conformal core regions. For the normal lungs, DMHs can either be higher or lower than DVHs depending on the target location within the lung. When the target is close to the lower lung, DMHs show higher values than DVHs because the lower lung has higher density than the central portion or the upper lung. DMHs are lower than DVHs for targets in the upper lung. The calculated NTCPs showed a large range of difference between DVHs and DMHs. Conclusion: The heterogeneity of lung can be well considered using DMH for evaluating target coverage and normal lung pneumonitis. Further studies are warranted to quantify the benefits of DMH over DVH for plan quality evaluation.

Purpose:Stereotactic intra and extra‐cranial body radiation therapy has evolved with advances in treatment accuracy, effective radiation dose, and parameters necessary to maximize machine capabilities. Novel gamma systems with a ring type gantry were developed having the ability to perform oblique arcs. The aim of this study is to explore the dosimetric advantages of this new system.Methods:The rotating Gamma system is named CybeRay (Cyber Medical Corp., Xian, China). It has a treatment head of 16 cobalt‐60 sources focused to the isocenter, which can rotate 360° on the ring gantry and swing 35° in the superior direction. Treatment plans were generated utilizing our in‐house Monte Carlo treatment planning system. A cylindrical phantom was modeled with 2mm voxel size. Dose inside the cylindrical phantom was calculated for coplanar and non‐coplanar arcs. Dosimetric differences between CybeRay cobalt beams and CyberKnife 6MV beams were compared in a lung phantom and for previously treated SBRT patients.Results:The full width at half maxima of cross profiles in the S‐I direction for the coplanar setup matched the cone sizes, while for the non‐coplanar setup, FWHM was larger by 2mm for a 10mm cone and about 5mm for larger cones. In the coronal and sagittal view, coplanar beams showed elliptical shaped isodose lines, while non‐coplanar beams showed circular isodose lines. Thus proper selection of the oblique angle and cone size can aid optimal dose matching to the target volume. Comparing a single 5mm cone from CybeRay to that from CyberKnife showed similar penumbra in a lung phantom but CybeRay had significant lower doses beyond lung tissues. Comparable treatment plans were obtained with CybeRay as that from CyberKnife.ConclusionThe noncoplanar multiple source arrangement of CybeRay will be of great clinical benefits for stereotactic intra and extra‐cranial radiation therapy.

Purpose:A new modernized design for cobalt 60 (Co‐60) machines is being developed with a ring type gantry. In this study we investigate the beneficial outcome of the new design for conformal arc therapy for various clinical sites. The new modality was evaluated based on isodose distributions and dose volume histograms as compared to 6MV photon beams from conventional linear accelerators.Methods:Computed tomographic images of seven different SBRT patients were selected from our patient database. All of these cases were previously planned on the Eclipse treatment planning system. New plans for these patients were generated with a modified conformal arc technique using both 6MV and Co‐60 beams. The conformal arc was created by the delivery of treatment fields conformal to the target cross‐section at every 5 or 10 degrees. The field shape was modified or turned off when it initially passed through a critical structure. Monte Carlo codes, MCBEAM and MCPLAN, were used for the machine head simulation and phantom/patient dose calculation, respectively. In the new Co‐60 machine design, the source‐to‐isocenter distance was 60cm and the treatment head included the Co‐60 source, primary collimator, jaws and MLC.Results:For all cases investigated, conformal arc plans utilizing Co‐60 beams achieved similar conformity (mean conformity index=1.19) comparing to 6MV photon beams. Isodose distributions were tailored similarly around the PTV; both Co‐60 and 6MV plans met our clinical acceptance criteria for the target coverage, and the maximum and minimum target doses. The DVH for the Co‐60 plans showed slightly lower doses to the critical structures although the differences were small in most cases.Conclusion:There were no significant dosimetric differences between 6MV and Co‐60 plans. Our results confirmed that this new Co‐60 design could be a cost‐effective machine for advanced radiotherapy due to its low cost, low maintenance and high up time.

Purpose:Co‐60 beams have unique dosimetric properties that are ideally suited for cranial treatments. Co‐60 sources with cone‐shaped collimators provide conformal dose distributions allowing for ablative treatments with rapid dose falloff to spare nearby critical structures. This work investigates a novel, image‐guided, rotational Gamma ray system that provides both superior dose conformity/gradient and accurate stereotaxy for stereotactic radiosurgery (SRS).Methods:The SupeRay system (Cyber Medical Corp., China) consists of a rotating source chamber containing 30 gamma sources focusing at the isocenter with 4 collimators measuring 3, 4, 8 and 16mm in diameter. A novel switch design enables the 30 Gamma sources to be turned off at any arbitrarily selected 60° interval in order to avoid critical structures. The 3D treatment couch provides automatic treatment positioning between individual shots and the kV imaging system provides orthogonal images with a spatial resolution of 0.24mm to facilitate target localization. Monte Carlo simulations were used to compute dose distributions and compare with measurements and other Gamma ray SRS systems.Results:Monte Carlo results confirmed the SupeRay design parameters including output factors and 3D dose distributions. Its beam penumbra/dose gradient is similar to or slightly better than that of the Elekta Gamma Knife. The penumbra in the (x,y,z) direction was (7.38mm,7.38mm,3.86mm) for the 16mm collimator, (4.83mm,4.83mm,3.12mm) for the 8mm collimator, and (3.03mm,3.03mm,2.38mm) for the 4mm collimator, respectively, on the SupeRay system while it was (9.5mm,10.0mm,2.9mm), (4.3mm,4.3mm,2.9mm) and (3.2mm,3.2mm,1.9mm) for the same collimator sizes, respectively, on the Perfexion system. The kV imaging system together with a non‐invasive relocatable frame provides accurate target localization (<0.5mm) for cases requiring multiple treatment fractions.Conclusion:Because of the unique dosimetric properties of Co‐60 sources and its accurate stereotaxy/dose delivery, SupeRay is ideally suited for single and multiple‐session ablative treatments of cranial lesions.This work was partially supported by Cyber Medical Corp.

Several specialty machines are available clinically for stereotactic radiosurgery/radiation therapy (SRS/SRT). Gamma Knife provides superior delivery accuracy for intracranial lesions and CyberKnife allows accurate SRS/SRT treatments for extracranial tumors with real-time image guidance and respiratory tracking. This work investigates a new SRS/SRT system that provides both superior dose conformity/gradient and accurate stereotaxy for intra/extracranial treatments. The CybeRay system (Cyber Medical Corp., China) consists of a ring gantry with a treatment head containing 16 gamma sources with a span of 33° in the superior-inferior direction, each focusing at the isocenter with 4 collimators measuring 4, 8, 16 and 32mm diameter. The treatment head can also swing 35° in the superior direction, allowing a total of 68° non-coplanar beam incident. The treatment couch provides 6-degrees-of-freedom motion compensation and the kV cone-beam CT system has a spatial resolution of 0.4mm for target localization. Monte Carlo simulations were used to compute dose distributions and compare with measurements. A retrospective study of 125 previously treated SBRT patients was performed to evaluate the dosimetric characteristics of the CybeRay system in comparison with existing SBRT systems. Monte Carlo results confirmed the CybeRay design parameters including output factors and 3D dose distributions. Its beam penumbra/dose gradient is similar to that of Gamma Knife and its stereotaxy/isocenter accuracy is 0.3mm. Compared to the 6 MV beams of the CyberKnife, Co-60 beams produce lower-energy secondary electrons that exhibit better dose properties in low-density lung tissues. Because of their rapid depth dose falloff, Co-60 beams are ideal for peripheral lung tumors with half-arc arrangements to spare the opposite lung and other critical structures. The table below shows the patient lateral size, body weight and target volume (mean±1SD) for the 125 patients investigated. Superior dose distributions have been obtained for brain, head and neck, breast, spine and lung tumors with half/full arc arrangements.Poster Viewing Abstracts 3416; Table 1Tumor SiteNumberLater Size (cm)Body Weight (lb)Target Volume (cc)Arc ArrangementsBrain, H&N832.9±10.9169.9±49.655.0±56.1Full ArcThorax7936.5±4.5161.0±41.944.6±47.7Half/Full ArcAbdomen1733.1±4.4166.0±45.5144.6±162.6Half/Full ArcPelvis739.4±6.0198.4±44.040.3±43.4Half/Full ArcSpine1036.3±5.3183.3±38.569.0±53.2Full ArcOther443.9±7.6161.0±37.7108.6±112.7Half/Full Arc Open table in a new tab The unique dosimetric properties of Co-60 sources and its accurate stereotaxy/dose delivery make CybeRay an ideal system for SRS/SRT of small (up to 100cc) intra/extracranial tumors. A clinical investigation of ablative treatment for multiple (1-3) discrete lung metastases with a single fraction of 25Gy is being conducted.

Introduction: The 60 Co beam emerging from the Gamma- Tomo source assembly was simulated in a previous study [1] and the authors reported the spectra of particles reaching the plane immediately (1mm) before the collimation system entrance. In the present work, we simulate the 60Co beam emerging from a novel Gamma-Tomo SBRT collimation system and calculate the output factors and dose rates for different source configurations and collimator sizes.Materials and Methods: A Gamma Tomo system includes 13 60 Co source capsules, source housing, a primary collimator and 4 different changeable collimators. The sources (6.22 mm of diameter) are located in 2 rows with different angles and distances to the longitudinal axis and the beams can be collimated to obtain four different circular field sizes at the isocenter (35 mm, 16 mm, 7mm, and 3.5mm). The BEAM- Monte Carlo [2] code is used to realistically model the collimation system geometry, including primary collimator and 4 different changeable collimators. The previously calculated phase space file [1] is used to transport particles throughout the collimation system to the patient plane for all of the changeable collimators of the Gama-Tomo System, and the respective phase space files of particles are stored at isocenter for each of the circular fields to be used as input of the GEPTS [3] to perform dose calculations. A newly designed geometry module is used to determine the dose distributions in a spherical polystyrene phantom with an 8cm radius centered at the isocenter.Results: The characteristics of the particle spectra emerging from the collimation assembly are determined and the effect of the source-collimator position on the spectra reaching the isocenter found to be dependent on field size. We observed differences up to 5% between the energy spectra and fluence distributions calculated for different configurations of the source-collimator assembly. The effect of the source-collimator position is observed (up to 6%) on dose distributions calculated at isocenter and is dependent upon the size of the circular field.Conclusions: The resulting data from the present study supports the machine design process and is valuble in building a well-represented source model for all sources to perform the dose calculations for all of the changeable collimators for this novel Gamma-Tomo system.

Purpose:Co‐60 beams have unique dosimetric properties for cranial treatments and thoracic cancers. The conventional concern about the high surface dose is overcome by modern system designs with rotational treatment techniques. This work investigates a novel rotational Gamma ray system for image‐guided, external beam radiotherapy.Methods:The CybeRT system (Cyber Medical Corp., China) consists of a ring gantry with either one or two treatment heads containing a Gamma source and a multileaf collimator (MLC). The MLC has 60 paired leaves, and the maximum field size is either 40cmx40cm (40 pairs of 0.5cm central leaves, 20 pairs of 1cm outer leaves), or 22cmx40cm (32 pairs of 0.25cm central leaves, 28 pairs of 0.5cm outer leaves). The treatment head(s) can swing 35° superiorly and 8° inferiorly, allowing a total of 43° non‐coplanar beam incident. The treatment couch provides 6‐degrees‐of‐freedom motion compensation and the kV cone‐beam CT system has a spatial resolution of 0.4mm. Monte Carlo simulations were used to compute dose distributions and compare with measurements. A retrospective study of 98 previously treated patients was performed to compare CybeRT with existing RT systems.Results:Monte Carlo results confirmed the CybeRT design parameters including output factors and 3D dose distributions. Its beam penumbra/dose gradient was similar to or better than that of 6MV photon beams and its isocenter accuracy is 0.3mm. Co‐60 beams produce lower‐energy secondary electrons that exhibit better dose properties in low‐density lung tissues. Because of their rapid depth dose falloff, Co‐60 beams are favorable for peripheral lung tumors with half‐arc arrangements to spare the opposite lung and critical structures. Superior dose distributions were obtained for head and neck, breast, spine and lung tumors.Conclusion:Because of its accurate dose delivery and unique dosimetric properties of C‐60 sources, CybeRT is ideally suited for advanced SBRT as well as conventional RT.This work was partially supported by Cyber Medical Corp.

Purpose:Estimation of Cerenkov dose from high‐energy megavoltage photon and electron beams in tissue and its impact on the radiosensitization using Protoporphyrine IX (PpIX) for tumor targeting enhancement in radiotherapy.Methods:The GEPTS Monte Carlo code is used to generate dose distributions from 18MV Varian photon beam and generic high‐energy (45‐MV) photon and (45‐MeV) electron beams in a voxel‐based tissueequivalent phantom. In addition to calculating the ionization dose, the code scores Cerenkov energy released in the wavelength range 375–425 nm corresponding to the pick of the PpIX absorption spectrum (Fig. 1) using the Frank‐Tamm formula.Results:The simulations shows that the produced Cerenkov dose suitable for activating PpIX is 4000 to 5500 times lower than the overall radiation dose for all considered beams (18MV, 45 MV and 45 MeV). These results were contradictory to the recent experimental studies by Axelsson et al. (Med. Phys. 38 (2011) p 4127), where Cerenkov dose was reported to be only two orders of magnitude lower than the radiation dose. Note that our simulation results can be corroborated by a simple model where the Frank and Tamm formula is applied for electrons with 2 MeV/cm stopping power generating Cerenkov photons in the 375–425 nm range and assuming these photons have less than 1mm penetration in tissue.Conclusion:The Cerenkov dose generated by high‐energy photon and electron beams may produce minimal clinical effect in comparison with the photon fluence (or dose) commonly used for photo‐dynamic therapy. At the present time, it is unclear whether Cerenkov radiation is a significant contributor to the recently observed tumor regression for patients receiving radiotherapy and PpIX versus patients receiving radiotherapy only. The ongoing study will include animal experimentation and investigation of dose rate effects on PpIX response.

Purpose:Modulated electron radiotherapy (MERT) has the potential to achieve better treatment outcome for shallow tumors such as those of breast and scalp. In a separate study with scalp lesions, MERT was compared to volumetric modulated arc therapy. Our results showed a reduction in the dose reaching the brain with MERT. However dose calculation accuracy and delivery efficiency challenges remain. Thus in the current study we proceed to add more cases to demonstrate MERT beneficial outcome and its delivery accuracy using an electron specific multileaf collimator (eMLC).Methods:We have used the MCBEAM code for treatment head simulation and for generating phase space files to be used as radiation source input for our Monte Carlo based treatment planning system (MC TPS). MCPLAN code is used for calculation of patient specific dose deposition coefficient and for final MERT plan dose calculation. An in‐house developed optimization code is used for the optimization process. MERT plans were generated for real patients and head and neck phantom. Film was used for dosimetric verification. The film was cut following the contour of the curved phantom surface and then sealed with black masking tape. In the measurement, the sealed film packet was sandwiched between two adjacent slabs of the head and neck phantom. The measured 2D dose distribution was then compared with calculations.Results:The eMLC allows effective treatment of scalps with multi‐lesions spreading around the patient head, which was usually difficult to plan or very time consuming with conventional applicators. MERT continues to show better reduction in the brain dose. The dosimetric measurements showed slight discrepancy, which was attributed to the film setup.Conclusion:MERT can improve treatment plan quality for patients with scalp cancers. Our in‐house MC TPS is capable of performing treatment planning and accurate dose calculation for MERT using the eMLC.