| 1. |
- Bjoreland, Anders, et al.
(författare)
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Liquid ionization chamber calibrated gel dosimetry in conformal stereotactic radiotherapy of brain lesions
- 2008
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Ingår i: Acta Oncologica. - : Informa UK Limited. - 1651-226X .- 0284-186X. ; 47:6, s. 1099-1109
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Tidskriftsartikel (refereegranskat)abstract
- Hypofractionated conformal stereotactic radiotherapy (HCSRT) is an established method of treating brain lesions such as arteriovenous malformations (AVMs) and brain metastases. The aim of this study was to investigate the reliability of treatment plans in the terms of dose distribution and absorbed dose for HCSRT. Methods and materials. Treatment plans for three different clinical intracerebral targets, AVMs, were transferred to a CT study of a spherical water filled phantom simulating the human head and recalculated for the phantom geometry using a standard treatment planning system utilizing a pencil beam algorithm for dose calculation. The calculated absorbed dose, relative three dimensional (3D) dose distribution and dose conformity were investigated using gel dosimetry normalized to liquid ionization chamber (LIC) measurements. Results. The measured absorbed dose to the dose reference point was found to be within 2% of the calculated dose for all three targets. The measured dose distribution was found to be within 3% and 2 mm of the calculated dose for more than 93% of all points in the target volume for all three targets. Conclusions. The results show that the investigated standard treatment planning system can correctly predict the absorbed dose and dose distribution in different types of intracerebral targets and that the treatment can be delivered according to the plan.
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| 2. |
- Daşu, Alexandru, et al.
(författare)
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The effects of hypoxia on the theoretical modelling of tumour control probability
- 2005
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Ingår i: Acta Oncologica. - : Informa UK Limited. - 0284-186X .- 1651-226X. ; 44:6, s. 563-571
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Tidskriftsartikel (refereegranskat)abstract
- Theoretical modelling of tumour response is increasingly used for the prediction of treatment result and has even been proposed as ranking criteria in some algorithms for treatment planning. Tumour response to radiation is greatly influenced by the details of tumour microenvironment, especially hypoxia, that unfortunately are not always taken into consideration for these simulations. This paper intends to investigate the effects of various assumptions regarding hypoxia distribution in tumours on the predictions of treatment outcome. A previously developed model for simulating theoretically the oxygenation in biologically relevant tissues, including results from oxygen diffusion, consumption and perfusion limitations in tumours, was used to investigate the effects of the different aspects of hypoxia on the predictions of treatment outcome. Thus, both the continuous distribution of values and the temporal variation of hypoxia patterns were taken into consideration and were compared with a 'black-and-white' simplification with a fully hypoxic compartment and a fully oxic one. It was found that the full distribution of oxygenation in the tissue is needed for accurate results. The 'black-and-white' simplification, while showing the same general trends for the predictions of radiation response, could lead to serious over-estimations of the tumour control probability. It was also found that the presence of some hypoxia for every treatment fraction leads to a decrease in the predicted local control, regardless of the change of the hypoxic pattern throughout the duration of the whole treatment. The results thus suggest that the assumptions regarding tumour hypoxia influence very much the predictions of treatment outcome and therefore they have to be very carefully incorporated into the theoretical modelling.
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| 3. |
- Daşu, Alexandru, et al.
(författare)
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The use of risk estimation models for the induction of secondary cancers following radiotherapy
- 2005
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Ingår i: Acta Oncologica. - : Informa UK Limited. - 0284-186X .- 1651-226X. ; 44:4, s. 339-347
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Tidskriftsartikel (refereegranskat)abstract
- Theoretical predictions of cancer risk from radiotherapy may be used as a complementary criterion for the selection of successful treatment plans together with the classical approach of estimating the possible deterministic effects. However, any such attempts must take into consideration the specific features of radiation treatment. This paper explores several possible methods for estimating the risk of cancer following radiotherapy in order to investigate the influences of the fractionation and the non-uniformity of the dose to the irradiated organ. The results indicate that dose inhomogeneity plays an important role in predicting the risk for secondary cancer and therefore for predictive purposes it must be taken into account through the use of the dose volume histograms. They also suggest that the competition between cell killing and the induction of carcinogenic mutations has to be taken into consideration for more realistic risk estimations. Furthermore, more realistic parameters could be obtained if this competition is also included in analyses of epidemiological data from radiotherapy applications.
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| 4. |
- Franzén, Lars, et al.
(författare)
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Fractionated irradiation and early changes in noradrenaline induced potassium efflux(86Rb+) in rat parotid gland
- 1992
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Ingår i: Acta Oncologica. - 0284-186X .- 1651-226X. ; 31:3, s. 359-364
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Tidskriftsartikel (refereegranskat)abstract
- The effects of fractionated irradiation on the electrolyte fluid secretion from rat parotid gland were studied. Secretion was measured as noradrenaline stimulated potassium efflux in vitro with Rb-86+ as tracer for potassium. The irradiation was delivered either as a five-day schedule (total dose 20, 25, 30, 35, 40, 45 Gy) or a two-day schedule (total dose 24, 32 Gy). The noradrenaline stimulated efflux was decreased in comparison with contralateral controls 10 days after the last irradiation. The effect was dose-dependent. Based on the data available, alpha/beta ratio of the used system was calculated to about 20 Gy, which corresponds to other results regarding early radiation effects.
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| 5. |
- Glimelius, B., et al.
(författare)
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Number of patients potentially eligible for proton therapy
- 2005
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Ingår i: Acta Oncol. - : Informa UK Limited. - 0284-186X .- 1651-226X. ; 44:8, s. 836-49
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Tidskriftsartikel (refereegranskat)abstract
- A group of Swedish radiation oncologists and hospital physicists have estimated the number of patients in Sweden suitable for proton beam therapy in a facility where one of the principal aims is to facilitate randomized and other studies in which the advantage of protons can be shown and the magnitude of the differences compared with optimally administered conventional radiation treatment, also including intensity-modulated radiation therapy (IMRT) and brachytherapy, can be shown. The estimations have been based on current statistics of tumour incidence in Sweden, number of patients potentially eligible for radiation treatment, scientific support from clinical trials and model dose planning studies and knowledge of the dose-response relations of different tumours together with information on normal tissue complication rates. In Sweden, it is assessed that between 2200 and 2500 patients annually are eligible for proton beam therapy, and that for these patients the potential therapeutic benefit is so great as to justify the additional expense of proton therapy. This constitutes between 14-15% of all irradiated patients annually.
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| 6. |
- Johansson, Adam, et al.
(författare)
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Improved quality of computed tomography substitute derived from magnetic resonance (MR) data by incorporation of spatial information : potential application for MR-only radiotherapy and attenuation correction in positron emission tomography
- 2013
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Ingår i: Acta Oncologica. - 0284-186X .- 1651-226X. ; 52:7, s. 1369-1373
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Tidskriftsartikel (refereegranskat)abstract
- Background: Estimation of computed tomography (CT) equivalent data, i.e. a substitute CT (s-CT), from magnetic resonance (MR) images is a prerequisite both for attenuation correction of positron emission tomography (PET) data acquired with a PET/MR scanner and for dose calculations in an MR-only radiotherapy workflow. It has previously been shown that it is possible to estimate Hounsfield numbers based on MR image intensities, using ultra short echo-time imaging and Gaussian mixture regression (GMR). In the present pilot study we investigate the possibility to also include spatial information in the GMR, with the aim to improve the quality of the s-CT. Material and methods: MR and CT data for nine patients were used in the present study. For each patient, GMR models were created from the other eight patients, including either both UTE image intensities and spatial information on a voxel by voxel level, or only UTE image intensities. The models were used to create s-CT images for each respective patient. Results: The inclusion of spatial information in the GMR model improved the accuracy of the estimated s-CT. The improvement was most pronounced in smaller, complicated anatomical regions as the inner ear and post-nasal cavities. Conclusions: This pilot study shows that inclusion of spatial information in GMR models to convert MR data to CT equivalent images is feasible. The accuracy of the s-CT is improved and the spatial information could make it possible to create a general model for the conversion applicable to the whole body.
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| 7. |
- Karlsson, Mikael, et al.
(författare)
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"Distributed proton radiation therapy"--a new concept for advanced competence support.
- 2006
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Ingår i: Acta oncologica (Stockholm, Sweden). - : Informa UK Limited. - 0284-186X .- 1651-226X. ; 45:8, s. 1094-101
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Tidskriftsartikel (refereegranskat)abstract
- The increased interest in high precision radiation therapy is to a large extent driven by the potential of modern imaging technology. The aim of this project was to analyse how an expensive proton facility best could support a multi-centre health care system. We have developed a model for distributed expert collaboration where all clinical experts will work close to their patients in regional centres. Patients who are candidates for proton therapy will be examined and dose-planned at their regional clinic, discussed in a fully information supported video conference and digitally made available at the proton treatment facility. The proton facility itself will be placed near a communication centre easily reached by all patients where they will be treated under full responsibility of their own physician at the home clinic. This concept has been analysed in detail both with respect to the overall functionality and with respect to possible weaknesses. It was found that the concept of distributed radiation therapy, as proposed here, will offer a stable clinical solution for advanced radiation therapy. It will support the spread of knowledge, serve as a fully developed backup system and the concept will further serve as an efficient base for clinical research.
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| 8. |
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| 9. |
- Mu, Xiangkui, et al.
(författare)
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Can photon IMRT be improved by combination with mixed electron and photon techniques?
- 2004
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Ingår i: Acta Oncologica. - : Informa UK Limited. - 0284-186X .- 1651-226X. ; 43:8, s. 727-735
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Tidskriftsartikel (refereegranskat)abstract
- Conformal radiotherapy or intensity modulated radiotherapy (IMRT) commonly leads to a large integral dose in the patient. Electrons would reduce the integral dose but are not suitable for treating deep-seated tumours, owing to their limited penetration. By combining electron and photon beams, the dose distributions may be improved. In this study, the possibility is explored of using a mixture of electron and photon beams for a deep-seated target volume in the head and neck region. Treatment plans were made for five simulated head and neck cancer cases. Mixed electron and photon beam plans (MB) were constructed using a manual iterative procedure. Photon IMRT plans were optimized automatically. Both electron and photon beams were collimated by a computer controlled multi-leaf collimator (MLC). Both methods were able to produce clinically acceptable plans. Criteria for the target dose were met similarly by both as were the criteria for critical organs. The integral dose outside the planning target volume (PTV) showed a tendency to be lower with MB plans compared with photon IMRT plans. A mixed electron and photon technique has the potential to treat deep-seated tumours. It is reasonable to expect that if computerized optimization tools were coupled with the mixed electron and photon beam technique, treatment goals would be more readily achieved than if using solely pure photon IMRT.
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| 10. |
- Mu, Xiangkui, et al.
(författare)
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Does electron and proton therapy reduce the risk of radiation induced cancer after spinal irradiation for childhood medulloblastoma? A comparative treatment planning study.
- 2005
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Ingår i: Acta oncologica (Stockholm, Sweden). - : Informa UK Limited. - 0284-186X .- 1651-226X. ; 44:6, s. 554-62
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this treatment planning comparison study was to explore different spinal irradiation techniques with respect to the risk of late side-effects, particularly radiation-induced cancer. The radiotherapy techniques compared were conventional photon therapy, intensity modulated x-ray therapy (IMXT), conventional electron therapy, intensity/energy modulated electron therapy (IMET) and proton therapy (IMPT).CT images for radiotherapy use from five children, median age 8 and diagnosed with medulloblastoma, were selected for this study. Target volumes and organs at risk were defined in 3-D. Treatment plans using conventional photon therapy, IMXT, conventional electron therapy, IMET and IMPT were set up. The probability of normal tissue complication (NTCP) and the risk of cancer induction were calculated using models with parameters-sets taken from published data for the general population; dose data were taken from dose volume histograms (DVH).Similar dose distributions in the targets were achieved with all techniques but the absorbed doses in the organs-at-risk varied significantly between the different techniques. The NTCP models based on available data predicted very low probabilities for side-effects in all cases. However, the effective mean doses outside the target volumes, and thus the predicted risk of cancer induction, varied significantly between the techniques. The highest lifetime risk of secondary cancers was estimated for IMXT (30%). The lowest risk was found with IMPT (4%). The risks associated with conventional photon therapy, electron therapy and IMET were 20%, 21% and 15%, respectively.This model study shows that spinal irradiation of young children with photon and electron techniques results in a substantial risk of radiation-induced secondary cancers. Multiple beam IMXT seems to be associated with a particularly high risk of secondary cancer induction. To minimise this risk, IMPT should be the treatment of choice. If proton therapy is not available, advanced electron therapy may provide a better alternative.
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