| 1. |
- Brodin, N Patrik, et al.
(författare)
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Radiobiological risk estimates of adverse events and secondary cancer for proton and photon radiation therapy of pediatric medulloblastoma.
- 2011
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Ingår i: Acta oncologica (Stockholm, Sweden). - 1651-226X. ; 50:6, s. 806-16
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Tidskriftsartikel (refereegranskat)abstract
- Abstract Introduction. The aim of this model study was to estimate and compare the risk of radiation-induced adverse late effects in pediatric patients with medulloblastoma (MB) treated with either three-dimensional conformal radiotherapy (3D CRT), inversely-optimized arc therapy (RapidArc(®) (RA)) or spot-scanned intensity-modulated proton therapy (IMPT). The aim was also to find dose-volume toxicity parameters relevant to children undergoing RT to be used in the inverse planning of RA and IMPT, and to use in the risk estimations. Material and methods. Treatment plans were created for all three techniques on 10 pediatric patients that have been treated with craniospinal irradiation (CSI) at our institution in 2007-2009. Plans were generated for two prescription CSI doses, 23.4 Gy and 36 Gy. Risk estimates were based on childhood cancer survivor data when available and secondary cancer (SC) risks were estimated as a function of age at exposure and attained age according to the organ-equivalent dose (OED) concept. Results. Estimates of SC risk was higher for the RA plans and differentiable from the estimates for 3D CRT at attained ages above 40 years. The risk of developing heart failure, hearing loss, hypothyroidism and xerostomia was highest for the 3D CRT plans. The risks of all adverse effects were estimated as lowest for the IMPT plans, even when including secondary neutron (SN) irradiation with high values of the neutron radiation weighting factors (WR(neutron)). Conclusions. When comparing RA and 3D CRT treatment for pediatric MB it is a matter of comparing higher SC risk against higher risks of non-cancer adverse events. Considering time until onset of the different complications is necessary to fully assess patient benefit in such a comparison. The IMPT plans, including SN dose contribution, compared favorably to the photon techniques in terms of all radiobiological risk estimates.
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| 2. |
- af Rosenschöld, Per Munck, et al.
(författare)
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The MCNP Monte Carlo Program
- 2012. - 2nd
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Ingår i: Monte Carlo Calculations in Nuclear Medicine : Applications in Diagnostic Imaging - Applications in Diagnostic Imaging. - : Taylor & Francis. - 9781439841099 - 9781439841105 ; , s. 153-172
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Bokkapitel (refereegranskat)abstract
- Monte Carlo N-Particle (MCNP) is a Monte Carlo code package allowing coupled neutron, photon, and electron transport calculations. Also, the possibility of performing heavy charged particle transport calculations was recently introduced with the twin MCNPX code package. An arbitrary three-dimensional problem can be formulated through the use of surfaces defining building blocks (“cells” that are assigned density, material, and relevant cross-section tables. The source can be specified as point, surface, or volumes using generic or as a phase/space file.
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| 3. |
- Brodin, N Patrik, et al.
(författare)
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Hippocampal sparing radiotherapy for pediatric medulloblastoma: impact of treatment margins and treatment technique.
- 2014
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Ingår i: Neuro-oncology. - : Oxford University Press (OUP). - 1523-5866 .- 1522-8517. ; 16:4, s. 594-602
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundWe investigated how varying the treatment margin and applying hippocampal sparing and proton therapy impact the risk of neurocognitive impairment in pediatric medulloblastoma patients compared with current standard 3D conformal radiotherapy.MethodsWe included 17 pediatric medulloblastoma patients to represent the variability in tumor location relative to the hippocampal region. Treatment plans were generated using 3D conformal radiotherapy, hippocampal sparing intensity-modulated radiotherapy, and spot-scanned proton therapy, using 3 different treatment margins for the conformal tumor boost. Neurocognitive impairment risk was estimated based on dose-response models from pediatric CNS malignancy survivors and compared among different margins and treatment techniques.ResultsMean hippocampal dose and corresponding risk of cognitive impairment were decreased with decreasing treatment margins (P < .05). The largest risk reduction, however, was seen when applying hippocampal sparing proton therapy-the estimated risk of impaired task efficiency (95% confidence interval) was 92% (66%-98%), 81% (51%-95%), and 50% (30%-70%) for 3D conformal radiotherapy, intensity-modulated radiotherapy, and proton therapy, respectively, for the smallest boost margin and 98% (78%-100%), 90% (60%-98%), and 70% (39%-90%) if boosting the whole posterior fossa. Also, the distance between the closest point of the planning target volume and the center of the hippocampus can be used to predict mean hippocampal dose for a given treatment technique.ConclusionsWe estimate a considerable clinical benefit of hippocampal sparing radiotherapy. In choosing treatment margins, the tradeoff between margin size and risk of neurocognitive impairment quantified here should be considered.
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| 4. |
- Brodin, N. Patrik, et al.
(författare)
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Modeling freedom from progression for standard-risk medulloblastoma : A mathematical tumor control model with multiple modes of failure
- 2013
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Ingår i: International Journal of Radiation Oncology, Biology, Physics. - : Elsevier BV. - 0360-3016. ; 87:2, s. 422-429
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Tidskriftsartikel (refereegranskat)abstract
- Purpose As pediatric medulloblastoma (MB) is a relatively rare disease, it is important to extract the maximum information from trials and cohort studies. Here, a framework was developed for modeling tumor control with multiple modes of failure and time-to-progression for standard-risk MB, using published pattern of failure data. Methods and Materials Outcome data for standard-risk MB published after 1990 with pattern of relapse information were used to fit a tumor control dose-response model addressing failures in both the high-dose boost volume and the elective craniospinal volume. Estimates of 5-year event-free survival from 2 large randomized MB trials were used to model the time-to-progression distribution. Uncertainty in freedom from progression (FFP) was estimated by Monte Carlo sampling over the statistical uncertainty in input data. Results The estimated 5-year FFP (95% confidence intervals [CI]) for craniospinal doses of 15, 18, 24, and 36 Gy while maintaining 54 Gy to the posterior fossa was 77% (95% CI, 70%-81%), 78% (95% CI, 73%-81%), 79% (95% CI, 76%-82%), and 80% (95% CI, 77%-84%) respectively. The uncertainty in FFP was considerably larger for craniospinal doses below 18 Gy, reflecting the lack of data in the lower dose range. Conclusions Estimates of tumor control and time-to-progression for standard-risk MB provides a data-driven setting for hypothesis generation or power calculations for prospective trials, taking the uncertainties into account. The presented methods can also be applied to incorporate further risk-stratification for example based on molecular biomarkers, when the necessary data become available.
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| 5. |
- Ceberg, Sofie, et al.
(författare)
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Tumor-tracking radiotherapy of moving targets; verification using 3D polymer gel, 2D ion-chamber array and biplanar diode array
- 2010
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Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 250:1, s. 235-239
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to carry out a dosimetric verification of a dynamic multileaf collimator (DMLC)-based tumor-tracking delivery during respiratory-like motion. The advantage of tumor-tracking radiation delivery is the ability to allow a tighter margin around the target by continuously following and adapting the dose delivery to its motion. However, there are geometric and dosimetric uncertainties associated with beam delivery system constraints and output variations, and several investigations have to be accomplished before a clinical integration of this tracking technique. Two types of delivery were investigated in this study I) a single beam perpendicular to a target with a one dimensional motion parallel to the MLC moving direction, and II) an intensity modulated arc delivery (RapidArc®) with a target motion diagonal to the MLC moving direction. The feasibility study (I) was made using an 2D ionisation chamber array and a true 3D polymer gel. The arc delivery (II) was verified using polymer gel and a biplanar diode array. Good agreement in absorbed dose was found between delivery to a static target and to a moving target with DMLC tracking using all three detector systems. However, due to the limited spatial resolution of the 2D array a detailed comparison was not possible. The RapidArc® plan delivery was successfully verified using the biplanar diode array and true 3D polymer gel, and both detector systems could verify that the DMLC-based tumor-tracking delivery system has a very good ability to account for respiratory target motion.
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| 6. |
- Enger, Shirin A., et al.
(författare)
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Dosimetry for gadolinium neutron capture therapy (GdNCT)
- 2013
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Ingår i: Radiation Measurements. - : Elsevier BV. - 1879-0925 .- 1350-4487. ; 59, s. 233-240
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Tidskriftsartikel (refereegranskat)abstract
- Background Gadolinium (Gd) neutron capture therapy (GdNCT) is based on a neutron capture reaction (NCR) that involves emission of both short and long range products. The aim of this study was to investigate both the microscopic and macroscopic contributions of the absorbed dose involved in GdNCT. Methods Cylindrical containers with diameters 1-30 mm filled with a solution of Gd were irradiated with epithermal neutrons. The background neutron dose as well as the prompt gamma dose has been calculated and measured by means of film dosimetry for the largest cylinder. Monte Carlo codes MCNP5(b) and GEANT4 have been utilized for calculation the absorbed dose. Results and discussion Results from the film dosimetry are in agreement with the calculations for high doses while for low doses the measured values are higher than the calculated results. For the largest cylinder, the prompt gamma dose from GdNCR neutron is at least five times higher than the background dose. For a cell cluster model, in the first 0.1 mm the major contribution to the absorbed dose is from IC electrons. If Gd atoms were homogeneously distributed in the nuclei of all tumour cells, capture events between neutron and Gd atoms close to DNA could kill the tumour cells and give cross-fire dose from IC electrons to the cells located in the 0.1 mm range. Conclusions For a correct GdNCT dosimetry both microscopic part of the dose delivered by short-range low energy electrons and macroscopic part delivered by the prompt gamma should be considered.
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| 7. |
- Persson, Bertil R, et al.
(författare)
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“Abscopal” Effect of Radiation Therapy Combined with Immune-Therapy Using IFN-γ Gene Transfected Syngeneic Tumor Cells, in Rats with Bilateral Implanted N29 Tumors
- 2011
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Ingår i: ISRN Immunology. - : Hindawi Limited. - 2090-5645 .- 2090-5653. ; 2011
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Tidskriftsartikel (refereegranskat)abstract
- The tumor growth rate response was studied on N29 rat glioma tumor cells subcutaneously implanted on both hind legs of Fischer-344 rats. At around 30 days after inoculation, RT was given with 60Co gamma radiation with 4 daily fractions of 5 Gy only to the right-lateral tumors. At days 26, 42, and 54 after inoculation, immunization was performed with irradiated syngeneic IFNγ-gene transfected cells. Tumor growth rate (TGR % per day) of the right-lateral irradiated tumor was significantly decreased (P<0.01) after RT alone and with the combination of RT and immunization. But immunization alone gave no significant decrease of the TGR but significantly increased time of survival. The TGR of the unirradiated left-lateral tumors was significantly decreased (P<0.02) only in the group of rats treated with RT alone. It is apparent that tumor cells killed by the radiation mediate suppression of tumor cells outside the target area. This effect is called the abscopal effect.
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| 8. |
- Persson, Bertil R, et al.
(författare)
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Radiation immunomodulatory gene tumor therapy of rats with intracerebral glioma tumors.
- 2010
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Ingår i: Radiation Research. - 0033-7587. ; 173:4, s. 433-440
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Tidskriftsartikel (refereegranskat)abstract
- Single-fraction radiation therapy with 5 or 15 Gy (60)Co gamma radiation was combined with intraperitoneal injections of syngeneic interferon gamma (IFN-gamma)-transfected cells in rats with intracerebral N29 or N32 glioma tumors at days 7, 21 and 35 after inoculation. For intracerebral N29 tumors, single-fraction radiation therapy with 5 or 15 Gy had no significant effect on the survival time. Immunization with IFN-gamma-transfected N29 cells significantly increased the survival time by 61%. Single-fraction radiation therapy with 5 Gy combined with immunization increased the survival time significantly by 87% and complete remissions by 75% while with 15 Gy the survival time increased 45% with 38% complete remissions. For intracerebral N32 tumors, single-fraction radiation therapy with 15 Gy increased the survival time significantly by 20%. Immunization by itself had no significant effect with IFN-gamma-transfected N32 cells, but combined with 15 Gy single-fraction radiation therapy it increased survival time significantly by 40%, although there were no complete remissions. Based on these findings, we suggest a new therapeutic regimen for malignant glioma using single-fraction radiation therapy with a target absorbed dose of the order of 5-10 Gy combined with clinically verified immunotherapy.
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