| 1. |
- Johansson, Bengt, 1958-, et al.
(författare)
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Phantom study of radiation doses outside the target volume brachytherapy versus external radiotherapy of early breast cancer
- 2003
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Ingår i: Radiotherapy and Oncology. - Amsterdam : Elsevier. - 1879-0887 .- 0167-8140. ; 69:1, s. 107-112
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Tidskriftsartikel (refereegranskat)abstract
- Background and purpose: Brachytherapy is sometimes suggested as an adjuvant treatment after surgery of some tumours. When introducing this, it would be useful to have an estimate of the dose distribution to different body sites, both near and distant to target, comparing conventional external irradiation to brachytherapy. The aim of the present study was to determine radiation doses with both methods at different body sites, near and distant to target, in an experimental situation on an operated left sided breast cancer on a female Alderson phantom. Methods: Five external beam treatments with isocentric tangential fields were given by a linear accelerator. A specified dose of 1.0 Gy was given to the whole left sided breast volume. Five interstitial brachytherapy treatments were given to the upper, lateral quadrant of the left breast by a two plane, 10 needles implant. A dose of 1.0 Gy specified according to the Paris system was administered by a pulsed dose rate afterloading machine. Absorbed dose in different fixed dose points were measured by thermoluminescence dosimeters. Results: Both methods yielded an absorbed dose of the same size to the bone marrow and internal organs distant to target, 1.0-1.4% of the prescribed dose. There was a trend of lower doses to the lower half of the trunk and higher doses to the upper half of the trunk, respectively, by brachytherapy. A 90% reduction of absorbed dose with brachytherapy compared to external irradiation was found in the near-target region within 5 cm from target boundary where parts of the left lung and the heart are situated. If an adjuvant dose of 50 Gy is given with the external radiotherapy and brachytherapy, the absorbed dose in a part of the myocardium could be reduced from 31.8 to 2.1 Gy. Conclusions: Near target, brachytherapy yielded a considerably lower absorbed dose which is of special importance when considering radiation effects on the myocard and lungs. We could not demonstrate any difference of importance, in absorbed dose to dose points distant to target. (C) 2003 Elsevier Ireland Ltd. All rights reserved.
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| 2. |
- Kjellén, Elisabeth, et al.
(författare)
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Comparison of low dose nicotinamide versus benzamide, administered per os, as radiosensitizers in a C3H mammary carcinoma
- 1988
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Ingår i: Radiotherapy and Oncology. - : Elsevier BV. - 1879-0887 .- 0167-8140. ; 12:4, s. 327-331
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Tidskriftsartikel (refereegranskat)abstract
- We have evaluated if any differences in tumor radiosensitization exist between the two adenosine diphosphate ribosyl transferase (ADPRT) inhibitors nicotinamide and benzamide at fractionated low doses. A significant radiosensitizing effect with nicotinamide at a 10 mg/kg per day dose was found in the tumor model used. We found, however, no radiosensitizing effect with benzamide given according to this schedule.
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| 3. |
- Weber, Lars, et al.
(författare)
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Verification of a dynamic wedge implementation in a pencil beam based dose planning system
- 1995
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Ingår i: Radiotherapy and Oncology. - : Elsevier BV. - 1879-0887 .- 0167-8140. ; 37:Suppl. 1, s. 26-26
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Tidskriftsartikel (refereegranskat)abstract
- The use of dynamic movements on linear accelerators during irradiation have found a revised interest lately due to the integration of computers to control the linear accelerator. An example of this is the generation of fields that resemble ordinary wedge fields. These fields are produced by moving one of the collimator blocks during irradiation, i. e. dynamic wedges.A pencil beam based system with the possibility of modelling dynamically modulated dose distributions from collimator movement specifications has extensively been investigated. Special interest has been focused on depth doses, profiles and output factors which have been generated by dynamic wedge fields. The data from the treatment planning system has been verified with measurements in water on a Varian 4 MV linear accelerator.The results indicate that calculations accurately predicts the outcome from dynamic wedges without any additional measurements than those used for characterisation of static open beams.
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| 4. |
- Adell, Gunnar, 1953-, et al.
(författare)
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p53 status : an indicator for the effect of preoperative radiotherapy of rectal cancer.
- 1999
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Ingår i: Radiotherapy and Oncology. - 0167-8140 .- 1879-0887. ; 51:2, s. 169-174
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Rectal carcinoma is a common malignancy, with a history of high local recurrence rates following surgery. In recent years. preoperative radiotherapy and refined surgical technique have improved local control rates.AIM: To investigate the relationship between expression of nuclear p53 protein and the outcome in rectal carcinoma, with and without short-term preoperative radiotherapy.MATERIAL: Specimens from 163 patients from the Southeast Swedish Health Care region included in the Swedish rectal cancer trial between 1987-1990.METHOD: New sections from the paraffin blocks of the preoperative biopsy and the surgical specimen were examined immunohistochemically using a p53 antibody (PAb 1801).RESULT: Expression of nuclear p53 protein was seen in 41% of the tumours. The p53 negative patients treated with preoperative radiotherapy had a significant reduction of local failure compared with the non-irradiated p53 negative patients (P = 0.0008). In contrast, p53 positive patients showed no benefit from preoperative radiotherapy. The interaction between p53 status and the benefit of radiotherapy was statistically significant (P = 0.018).CONCLUSION: Expression of nuclear p53 protein in rectal carcinoma seems to be a significant predictive factor for local treatment failure after preoperative radiotherapy. Further investigations are necessary to select patients for preoperative treatment based on analysis of the preoperative biopsies.
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| 5. |
- Blomquist, M, et al.
(författare)
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Test procedures for verification of an electron pencil beam algorithm implemented for treatment planning
- 1996
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Ingår i: Radiotherapy and Oncology. - : Elsevier BV. - 0167-8140 .- 1879-0887. ; 39:3, s. 271-286
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Tidskriftsartikel (refereegranskat)abstract
- The calculation of an electron dose distribution in a patient is a difficult problem because of the presence of tissue and surface inhomogeneities. Verification of the dose planning system is therefore essential. In this investigation, a novel method is used to evaluate a commercially available system (Helax-TMS), at electron energies between 10 and 50 MeV, both for a conventional treatment unit and an MLC-collimated scanned beam unit with a helium-filled treatment head. First, the experiments were designed to verify the local beam database and some fundamental characteristics of the electron beam calculations. Secondly, a number of generalised situations that would be encountered in the clinical treatment planning were evaluated: oblique incidence, field shaping with multi-leaf collimator, bolus edges, and air cavities. Dose distributions in two generalised anatomical phantoms simulating a neck and a nose were also analysed. The results have, when so possible, been presented as the dose ratio within the 'flattened area' for dose profiles and down to the 'treatment depth' (80% dose level) for depth doses. In the penumbra region and in the dose fall-off region, the comparison has been represented by the distance deviation between calculated and measured dose profiles or depth doses. A new tool, 'volume integration', was used to evaluate the deviations from a more clinical point of view. Most results were within +/-2% in dose for volumes larger than a sphere with a diameter of 15 mm, or +/-2 mm in position. Dose deviations were generally found for oblique incidences and below heterogeneities such as small air cavities and bolus edges in limited volumes.
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| 6. |
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| 7. |
- Brynolfsson, Patrik, et al.
(författare)
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Gray-level invariant Haralick texture features
- 2018
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Ingår i: Radiotherapy and Oncology. - : Elsevier. - 0167-8140 .- 1879-0887. ; 127, s. S279-S280
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 8. |
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| 9. |
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| 10. |
- Daşu, Alexandru, et al.
(författare)
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New insights into factors influencing the clinically relevant oxygen enhancement ratio
- 1998
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Ingår i: Radiotherapy and Oncology. - 0167-8140 .- 1879-0887. ; 46:3, s. 269-277
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND AND PURPOSE: This paper deals with the variations in the oxygen enhancement ratios that could be observed (OER') when comparing oxic and hypoxic cells in different types of fractionated experiments as a consequence of the non-linearity of the underlying cell survival curves. Calculations have been made of the OER' that would be obtained for fractionated irradiations with a series of small doses to allow the comparison of isoeffective doses in oxic and hypoxic conditions. Two styles of fractionated experiment were modelled. In one, the dose per fraction was kept constant in the oxic and hypoxic arms of the experiment, necessitating more fractions in hypoxia to achieve the same level of cell kill. In the other the number of fractions was kept constant and the fraction size was varied to obtain equal levels of damage. The first is the relevant design for the clinic, whereas the second is the design most commonly used in animal studies. MATERIALS AND METHODS: Three models of the survival curve were used to simulate the response of cells to radiation injury, all based on the linear quadratic model, but with various added assumptions. A simple classical LQ model is compared with two models in which the concept of inducible repair is added. In one of these the induction dose for 'switching on' the more resistant response is assumed to be increased in hypoxia and in the other it is assumed to be independent of the oxygen tension. RESULTS: These calculations show a clear and previously unsuspected dependence of the measured OER' on the design of the fractionated experiment. The values obtained in the clinical and animal types of study differ considerably with all three models. The direction and magnitude of that difference depends critically on the assumptions about the fine structure of the survival curve shape. The authors suggest that the inducible repair version with an oxygen-dependent induction dose is probably the most relevant model. Using this, the measured OER' is reduced at doses around 2 Gy for the clinically relevant design of constant sized fractions to the oxic and hypoxic cells. It may even, in certain model assumptions, fall below unity resulting in an increased sensitivity, not resistance, from the hypoxia. CONCLUSIONS: These calculations indicate the urgent need for more knowledge about the fine structure of the low dose region of the survival curves for human tumour cells and especially for comparisons in the presence and absence of oxygen. The extent of the hypersensitivity at very low doses, the trigger dose needed to induce the repair and its oxygen modification may be dominant factors in determining the response of tumour cells to clinically relevant fractionation schedules.
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| 17. |
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| 18. |
- Johansson, Bengt, 1958-
(författare)
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Brachytherapy a useful tool for nasal and peri-nasal tumours
- 2021
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Ingår i: Radiotherapy and Oncology. - : Elsevier. - 0167-8140 .- 1879-0887. ; 158:Suppl. 1, s. S62-S62
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- There is an increasing incidence of Basal cell carcinoma (BCC) and Squamous cell carcinoma (SCC) on the external nose. Surgery is the main treatment but often face problems with respect to cosmetic defects and non-radical resection. Brachytherapy (BT) can be used in the primary treatment to preserve cosmetic appearance and to treat with appropriate margins. Brachytherapy are also indicated in tumor recurrence after surgery and in case of non-radical resection. Long-term local control rate (LCR) in literature is 90-95 %. Treatment time is short 1-2 weeks.There are different BT techniques available such as -Surface BT (Valencia applicator or Mould BT), -interstitial BT (trans-nasal or along nasal) or a combination of both.The choice of BT technique is depending on; -thickness of the tumor, -location on the nose (cartilage part vs bony part), -tumor growth (flat part, curvature part, exophytic part), -extension to peri-nasal areas (upper lip, cheek, medial eye corner).Usually a full dose of BT is prescribed ike 60 Gy PDR (0.83 Gy/ 2nd hour) or 45, 5 Gy HDR (3.5 Gy 2fx/d) (GEC-ESTRO recommendations for head/neck BT RTO 20016:10 and skin RTO 2018:126). Own experience 1998-2019 in 121 patients confirms published results of 93.4 % long-term LCR.Side effects are uncommon and include: septum perforation, telangiectasia, atrophy and sclerosis. Multidisciplinary conferences and teaching of plastic surgeons about potential benefits of BT are fundamental to avoid unnecessary mutilation.
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| 19. |
- Jonsson, Joakim, 1984-
(författare)
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Different methods of creating pseudo-CT images
- 2018
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Ingår i: Radiotherapy and Oncology. - : Elsevier. - 0167-8140 .- 1879-0887. ; 127, s. S349-S349
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 20. |
- Karlsson, Mikael, et al.
(författare)
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Exploration of new treatment modalities offered by high energy (up to 50 MeV) electrons and photons
- 1997
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Ingår i: Radiotherapy and Oncology. - 0167-8140 .- 1879-0887. ; 43:3, s. 303-309
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Tidskriftsartikel (refereegranskat)abstract
- Background and purpose: A number of deep seated tumours are difficult to treat conformally with photon beams mainly dub to the almost exponential dose decrease with depth. Materials and methods: In order to improve the conformity of these treatments a number of useful characteristics of high energy (above 20 MeV) electron beams of the MM50 Racetrack Microtron have been systematically investigated and clinically applied. Results: A typical characteristic of electron beams with energies up to 20 MeV is the sharp dose fall-off with depth. At higher energies this effect is less pronounced but may be improved by adding a small fraction of photons with a matching dose gradient (wedge). With this technique, high energy electrons can be used close to sensitive organs down to 17 cm depth. Another physical characteristic of high energy electrons is the sharp penumbra at depths down to 4-5 cm and the possibility to use opposed electron beams in order to enhance the dose centrally or near the centre of a body. Skin sparing by delivering a part of the absorbed dose with photons through the same beam portal as the electrons has also been systematically studied. These characteristics of the high-energy electron beams have been utilised in the optimisation of some clinical treatments. Conclusions: Electron beams in this high energy region give increased possibilities to achieve dose conformity. Enhanced conformity can be obtained especially if electrons and photons are combined to augment some specific characteristics of the electron beams.
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| 21. |
- Karlsson, Magnus G, et al.
(författare)
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Semi-conductor detectors in output factor measurements
- 1997
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Ingår i: Radiotherapy and Oncology. - 0167-8140 .- 1879-0887. ; 42:3, s. 293-296
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Tidskriftsartikel (refereegranskat)abstract
- Background and purpose: Output factors are generally measured with cylindrical ionization chambers. It was investigated if Si-diodes of p-type instead could be used. The advantage would be the small detector size and the robust construction of the detector. Materials and methods: Two types of diodes were studied, one with a shielding layer of tungsten specially made to reduce the excess response for scattered photons and one standard diode without any extra shielding. The measurements were performed at accelerating potentials between 4 and 50 MV and beam sizes between 4 cm x 4 cm and 40 cm x 40 cm. Results: The results showed that both types of diodes are suitable for measurements of head scatter factors in mini-phantoms. However, the diodes were found inappropriate for measurement of output factors for large fields in extended water phantoms. For small fields (<10 cm x 10 cm) a small detector is advantageous and no errors due to the scatter contribution were seen. Conclusions: An cylindrical ionization chamber is the best choice for output factor measurements in extended water phantoms for large field sizes while diodes are an alternative in small fields. There were negligible differences between the detectors in head scatter measurements in mini phantoms.
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| 22. |
- Karlsson, Mikael, et al.
(författare)
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Matching of electron and photon beams with a multi-leaf collimator
- 1993
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Ingår i: Radiotherapy and Oncology. - : Elsevier BV. - 0167-8140 .- 1879-0887. ; 29:3, s. 317-326
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Tidskriftsartikel (refereegranskat)abstract
- Multi-leaf collimators (MLCs) are offered as an accessory to many accelerators for radiation therapy. However, beam edges generated with these collimators are not as smooth as can be achieved with individually made blocks. The clinical drawbacks and benefits of this ripple were evaluated both for single field treatments and for combined adjacent fields of different beam qualities. In this investigation the MLC-collimated beams of the MM50 racetrack microtron were studied. The distance between the field edge and the 90% isodose was measured at the reference depth for four beam qualities (20 MV photons and 10, 20 and 50 MeV electrons). This distance was found to vary from approximately 6 mm for straight beam edges (i.e., all collimator leaves aligned) to approximately 2 mm from the tip of the leaves for a saw-tooth shaped beam edge. The over- and under-dosage in the joint between combined adjacent fields was found to be typically +/- 10% in small volumes. Improved clinical techniques using adjacent photon and electron fields with the same isocentre and source position (without moving the gantry) have been developed. For treatments of the breast, including the mammary chain, a uniform dose distribution was created with special attention given to the irradiation of the heart and lung outside the target volume. A method for head and neck treatments was optimised to give uniform dose distribution in the joint between the photon and electron fields and a method of treating the mediastinum, including the chest wall in front of the left lung, was analysed with respect to dose uniformity in the tumour and shielding of the lung.
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| 23. |
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| 24. |
- Mu, Xiangkui, et al.
(författare)
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The effect of fraction time in intensity modulated radiotherapy : theoretical and experimental evaluation of an optimisation problem.
- 2003
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Ingår i: Radiotherapy and Oncology. - 0167-8140 .- 1879-0887. ; 68:2, s. 181-187
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND AND PURPOSE: In intensity modulated radiotherapy (IMRT), the complexity and the number of treatment fields have expanded. This may imply that the delivery time for each fraction becomes prolonged. In a number of IMRT techniques used in the clinic, the delivery time per fraction is usually 10-15 min, sometimes more than 15 min. In studies on human skin, prolonged delivery time is shown to cause significant reduction of radiation effects compared with acute irradiation. In this paper the effect of changes in fraction delivery time was studied by in vitro irradiation of mammalian cells. MATERIAL AND METHODS: Chinese hamster fibroblasts (V79-379-A) were used for simulating clinical situations. Most experiments were performed with 2Gy/fraction with 4-h intervals in 40-60 replicates. Each fraction was divided into different subfractions, simulating the delivery of a complicated treatment. The effect of changing the delivery time for each fraction was studied. Parameters for the cell survival curve and repair kinetics were determined experimentally. The same methods were also used for large fraction sizes (8Gy). The validity of the most widely used models in the literature, all derived from linear-quadratic formalism, were tested against the experimental results. RESULTS: The effect of prolonging the fraction time for 2-Gy fractions was underestimated by the biological models. The experiments showed that 10-min prolonged delivery time gave a ratio between surviving fractions at 2Gy (S-ratio) of 1.054 with a 95% confidence interval (CI) 1.030-1.080, while the models predicted 1.007 and 1.009. Extending the fraction time to 20 min gave an S-ratio of 1.063 with CI of 1.045-1.080, while the models predicted 1.012 and 1.014. For 8-Gy fractions, there was a good agreement between predications and experimental results. The ratio between surviving fractions at 8Gy is 1.370 with CI of 1.300-1.440, while the models predicated 1.37 and 1.35. CONCLUSIONS: The effect of prolonging fraction time at conventional dose/fraction is underestimated by biological models. Prolonging the fraction time will spare tissues with a fast DNA repair. There is a risk for sparing tumours. This should be considered when IMRT technique is implemented in the clinic.
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| 25. |
- Olofsson, Jörgen, et al.
(författare)
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A widely tested model for head scatter influence on photon beam output
- 2003
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Ingår i: Radiotherapy and Oncology. - 0167-8140 .- 1879-0887. ; 67:2, s. 225-238
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: To construct and test a semi-analytical model describing the effects on Monitor Unit (MU) verification caused by scattering in the treatment head. The implementation of the model should be accomplished using a small set of experimental data. Furthermore, the model should include a geometry dependent estimation of the resulting uncertainty. Material and methods: The input required by the created model consists of basic treatment head geometry and 10 measured output factors in air (OFair) for square fields. It considers primary energy fluence, scattered radiation from an extra-focal source and from secondary collimators, as well as backscatter to the monitor chamber. Measurements and calculations were performed in open symmetric and asymmetric fields at points located both on and off the collimator axis, as well as at arbitrary treatment distances. The model has been verified for 19 photon beams in the range from 4 up to 50 MV, provided by nine different treatment units from six manufacturers. Results: The presented model provided results with errors smaller than 1% (2 S.D.) in typical clinical situations for all beams tested. In more exceptional situations, i.e. combinations of unconventional treatment head designs, very elongated fields, and dosimetry points far away from the isocenter, the total uncertainty increased to approximately 2%. The spread in the results was further analysed in order to create a method for predicting the uncertainties under different treatment conditions. Conclusions: A general head scatter model that is easy to implement has been developed and can be used as the basis for computerised MU verification. The model handles all commercially available treatment units adequately and also includes an estimation of the resulting uncertainty.
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