Development of an IAEA phase-space dataset for the Leksell Gamma Knife® Perfexion™ using multi-threaded Geant4 simulations

Kim, Tae Hoon; Schaarschmidt, Thomas; Yang, Hye Jeong; Kim, Yong Kyun; Chun, Kook Jin; Choi, Y.; Chung, Hyun‐Tai

doi:10.1016/j.ejmp.2019.07.002

Cited by 11 publications

(13 citation statements)

References 23 publications

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“…The Penelope low‐energy electromagnetic physics model was employed, and the secondary particle production cut value was 990 eV, which was the minimum energy value in the physics list. The simulation was verified using dose distributions measured with films 22 . The absorbed doses to water in the CV, a 0.5 × 0.5 × 0.5 mm 3 cube, and the ISSs in water spheres with radii of 8 cm were obtained using simulations (Figure 5a,b).…”

Section: Methodsmentioning

confidence: 90%

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Feasibility of isodose‐shaped scintillation detectors for the measurement of gamma knife output factors

et al. 2022

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Purpose Scintillation detectors were 3D printed based on a gamma knife (GK) dose distribution to calculate the volume averaging effect. The collimator output factors were measured using isodose‐shaped scintillators (ISSs) and compared with those of a micro‐diamond detector and previous reports. Methods An absorbed dose distribution in a spherical dosimetry phantom with a radius of 8 cm was obtained from GK treatment planning software (Leksell GammaPlan [LGP], Elekta AB, Stockholm, Sweden). Two types of ISSs were fabricated to fit the 97.2% (ISS‐1) and 95.6% (ISS‐2) isodose surfaces. The volume averaging correction factors were obtained by dividing the absorbed dose to water in the central voxel (CV) by that in the ISS. The correction effect due to the difference between the ISS and water was calculated by Monte Carlo simulations. Ten ISS detectors, five of each type, were used to measure the output factors of the 4‐ and 8‐mm collimators of a GK Icon to assess system consistency. The output factors of seven GKs were measured using two ISS detectors, one of each type, and a PTW T60019 (PTW, Freiburg, Germany) micro‐diamond detector. Results The detector output ratios (DORs) measured using the five ISSs of each type were consistent, with standard uncertainties less than 0.2%. In the 4‐mm field, the volume averaging correction factor ratios were 1.018 and 1.026, and the output factors after all corrections were 0.827 (0.006) and 0.825 (0.006) for ISS‐1 and ISS‐2, respectively. In the 8‐mm field, the volume averaging correction factor ratios were 1.000 for both ISS types, and the output factors were 0.898 (0.003) and 0.900 (0.003) for ISS‐1 and ISS‐2, respectively. The ISS detectors could measure the output factors of a GK with uncertainties comparable to that of the PTW 60019 detector. The output factors of all detectors decreased with the dose rate. Conclusion The volume averaging effect of an ISS developed in‐house could be calculated using known dose distributions. The collimator output factors of the GK Perfexion/Icon models measured using ISS detectors were consistent with those of a commercial synthetic micro‐diamond detector and recent studies.

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Section: Methodsmentioning

confidence: 90%

“…The correction factors were also obtained with MC simulation codes developed in-house. 22 Eight simulations with 1.92 × 10 10 primary photons were performed for each collimator. The simulated volume averaging correction factor ratios and the LGP values were within 0.3% of each other.…”

Section: Correction Factor Ratiosmentioning

confidence: 99%

Feasibility of isodose‐shaped scintillation detectors for the measurement of gamma knife output factors

et al. 2022

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“…Figure 2 shows the overlapping particle positions sampled from all 24 GK phase spaces manifesting three collimator sizes (color coded by red for 16 mm, green for 8 mm, and blue for 4 mm), eight sectors (at different azimuth angles), and five rings (at different zenith angles). Note that the display in Figure 2 is on the phase spaces, not the real source distribution, which is on a conical surface for GK Perfexion/Icon 11–13 . Also note that since the current GK treatment planning and delivery can only be modulated at the level of sectors, not at the level of rings or individual sources, we do not need to record the phase space for each source or ring for the purpose of calculating reference kernels.…”

Section: Methodsmentioning

confidence: 99%

Dose kernel decomposition for spot‐based radiotherapy treatment planning

et al. 2021

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Pre-calculation of accurate dose deposition kernels for treatment planning of spot-based radiotherapies, such as Gamma Knife (GK) and Gamma Pod (GP), can be very time-consuming and may require large data storage with an enormous number of possible spots. We proposed a novel kernel decomposition (KD) model to address accurate and fast (real-time) dose calculation with reduced data storage requirements for spot-based treatment planning. The application of the KD model was demonstrated for clinical GK and GP radiotherapy platforms. Methods: The dose deposition kernel at each spot (shot position) is modeled as the product of a shift-invariant kernel based on a reference kernel and spatially variant scale factor. The reference kernel, one for each collimator, is defined at the center of the commissioning phantom for GK and at the center of the treatment target for GP and calculated using the Monte Carlo (MC) method. The spatially variant scale factor is defined as the ratio of the mean tissue maximum ratio (TMR) at the candidate shot position to that at the reference kernel position, and the mean TMR map is calculated within the entire volume through parallel beam ray tracing on the density image followed by averaging over all source directions. The proposed KD dose calculations were compared with the MC method and with the GK and GP treatment planning system (TPS) computations for various shot positions and collimator sizes utilizing a phantom and 14 and 12 clinical plans for GK and GP, respectively. Results: For the phantom study, the KD Gamma index (3%/1 mm) passing rates were greater than 99% (median 100%) relative to the MC doses, except for the shots close to the boundary. The passing rates dropped below 90% for 8 mm (16 mm) shots positioned within ∼1 cm (∼2 cm) of the boundary. For the clinical GK plans, the KD Gamma passing rates were greater than 99% (median 100%) compared to the MC and greater than 92% (median 99%) compared to the TPS. For the clinical GP plans, the KD Gamma passing rates were greater than 95% (median 98%) compared to the MC and greater than 91% (median 97%) compared to the TPS. The scale factors were calculated in sub-seconds with GPU implementation and only need to be calculated once before treatment plan optimization. The calculation of the dose kernel was also within sub-seconds without requiring beam-by-beam calculation commonly done in the TPS. Conclusion:The proposed model can provide an accurate dose and enables real-time dose and derivative calculations by kernel shifting and scaling without pre-calculating or requiring large data storage for GK and GP dose deposition kernels during treatment planning. This model could be useful for spot-based radiotherapy treatment planning by allowing an efficient global fine search for optimal spots.

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“…The 60 Co ra dio ac tive iso tope-based irradiator is widely used in med i cal sci ence, ra di a tion mea surement, radionuclide anal y sis, in dus try ap pli ca tions, bio log i cal ex per i ments, and stan dard ir ra di a tion [1][2][3][4][5][6][7]. Dongnam In sti tute of Ra dio log i cal and Med i cal Sciences (DIRAMS) has a 60 Co irradiator (Gammabeam X-200, BEST Theratronics) for re search pur poses.…”

Section: Introductionmentioning

confidence: 99%

Measurement of absorbed dose rate in water phantom maintained at body temperature by 60Co irradiator – comparison of experimental results and Monte Carlo simulation

et al. 2021

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To analyze the biological effects of radiation, it is important that the conditions of in vitro experiments match closely with those of in vivo experiments. In this study, we constructed an irradiation system to conduct irradiation experiments under conditions similar to those of in vivo experiments. The Dongnam Institute of Radiological and Medial Sciences has a gamma irradiator including 60Co radioisotope for research purposes and accreditation for standard calibration of the ion chamber. The temperature of the water phantom was maintained the same as that of the normal human body, and the physical dosimetry was carried out accurately using the ion chamber with traceability. We report the measurement of lateral profiles, depth profiles, and absorbed dose rate in water, Dw, at the irradiation location of the blood samples using a farmer-type ion chamber. We simulated the source, collimator, irradiator, phantom, and extra structure of the gamma irradiation system using the Monte Carlo code and compared the simulated and the experimental results. The experimentally and theoretically evaluated dose rates were 0.2975 ? 0.0055 Gymin?1 (at coverage factor k = 2) and 0.2978 ? 0.0052 Gymin?1 (at coverage factor k = 2) at source-to-surface distance of 100 cm and 5 gcm?2 depth in the water phantom, respectively. Blood irradiation will be conducted in vitro, under conditions similar to in vivo conditions, to provide the dose-response curve based on dosimetry with traceability.

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Development of an IAEA phase-space dataset for the Leksell Gamma Knife® Perfexion™ using multi-threaded Geant4 simulations

Cited by 11 publications

References 23 publications

Feasibility of isodose‐shaped scintillation detectors for the measurement of gamma knife output factors

Feasibility of isodose‐shaped scintillation detectors for the measurement of gamma knife output factors

Dose kernel decomposition for spot‐based radiotherapy treatment planning

Measurement of absorbed dose rate in water phantom maintained at body temperature by 60Co irradiator – comparison of experimental results and Monte Carlo simulation

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