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| 2. |
- Hedin, Emma, 1985, et al.
(författare)
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Impact of lung density on the lung dose estimation for radiotherapy of breast cancer
- 2017
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Ingår i: Physics and Imaging in Radiation Oncology. - : Elsevier BV. - 2405-6316. ; 3, s. 5-10
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Tidskriftsartikel (refereegranskat)abstract
- Background and purpose: To investigate the impact of the clinical implementation particle transport method on the lung dose evaluation for radiotherapy of breast cancer focusing on dosimetric effects of the lung density. Material and methods: Fourteen patients with left sided breast cancer having both deep inspiration breath hold (DIBH) and free breathing CT scans were studied. Lung density variations for 157 patients treated under DIBH were quantified and the cases with the lowest lung densities for breast and for loco regional treatment added to the study. Dose calculations were performed with the class-b type algorithm AAA and the deterministic algorithm Acuros XB. Monte Carlo method was utilized as reference. Differences in the dose distributions were evaluated by comparing DVH parameters. Results: Lung density variations between 0.08 and 0.3 g/cm3 and between 0.02 and 0.25 g/cm3 were found for loco-regional and tangential breast treatments under DIBH, respectively. Lung DVH parameters for patients with medium and high lung density obtained by the different algorithms agreed within 3%. Larger differences were observed for low lung density cases where the correction based algorithm underestimated V10Gy and overestimated V40Gy by up to 5%. The least affected parameter, V20Gy, deviated by less than 2% for all cases and densities. Conclusions: Dosimetric constrains for lung based on V20Gy required minimum changes due to implementation of the new algorithm regardless of breathing technique or type of treatment. Evaluation criteria utilizing V10Gy or V40Gy needed reconsideration, especially for treatments under DIBH involving low lung density.
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| 3. |
- Hedin, Emma, 1985, et al.
(författare)
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Implementation of Acuros XB in Treatment Planning of SBRT of Lung Cancer
- 2017
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Ingår i: Annals of Radiation Therapy and Oncology. - 2577-8757. ; 1:2
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Tidskriftsartikel (refereegranskat)abstract
- Goal: The overall goal of this study is to present data assisting the implementation of the principle based dose calculation algorithm Acuros XB for Stereotactic Body Radiation Treatments (SBRT) of lung tumors. In particular, the goal is to investigate differences in target dose distributions calculated by the clinical algorithms AAA and Acuros XB as well as by the Monte Carlo method. Materials and Methods: Twenty conventional 3D conformal plans for SBRT of lung cancer were investigated. The prescribed dose was 3 Gy × 22 Gy at the center and 3 Gy × 15 Gy at the periphery of PTV. The plans were originally designed with AAA based on the requirement PTV-V100% (percentage of PTV receiving a dose larger than 100%=45 Gy), to be 100%. Recalculations were performed by utilizing Acuros XB as well as by full Monte Carlo method. Dose variations were evaluated in terms of DVH parameters D5%, D50%, D98% for GTV and PTV as well as PTV-V100%. Five plans showing large algorithm sensitivity in terms of PTV-V100% were re-planned by Acuros XB using the same treatment planning criteria. Results: AAA systematically overestimated the PTV dose compared to Acuros XB and Monte Carlo. Differences between AAA and Acuros XB of up to 8%, 10% and 5% were observed for PTV-D50%, PTV-D98% and PTV-V100%, correspondingly. The values obtained by the Monte Carlo method were up to 7% lower than these for Acuros XB. The variations in the PTV dose estimation could not be related to patient/plan characteristics like target volume, lung tissue volume included in the target or tumor proximity to the lung wall. The variations in the GTV parameters were smaller and the agreement between AAA and AXB as well as between Acuros XB and Monte Carlo was within 3%. Planning with Acuros XB increased the volume of the lung tissue close to the tumor receiving full dose by more than 20%. Conclusion: PTV dose coverage was overestimated in plans calculated by AAA. Transition to Acuros XB without changing the treatment planning criteria increased the dose to the lung tissue close to the tumor. The GTV dose coverage was more robust with respect to the algorithm changes.
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| 4. |
- Hedin, Emma, 1985, et al.
(författare)
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Jaw position uncertainty and adjacent fields in breast cancer radiotherapy.
- 2015
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Ingår i: Journal of applied clinical medical physics / American College of Medical Physics. - : Wiley. - 1526-9914. ; 16:6
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Tidskriftsartikel (refereegranskat)abstract
- Locoregional treatment of breast cancer involves adjacent, half blocked fields matched at isocenter. The objective of this work is to study the dosimetric effects of the uncertainties in jaw positioning for such a case, and how a treatment planning protocol including adjacent field overlap of 1 mm affects the dose distribution. A representative treatment plan, involving 6 and 15 photon beams, for a patient treated at our hospital is chosen. Monte Carlo method (EGSnrc/BEAMnrc) is used to simulate the treatment. Uncertainties in jaw positioning of ± 1 mm are addressed, which implies extremes in reality of 2 mm field gap/overlap when planning adjacent fields without overlap and 1 mm gap or 3 mm overlap for a planning protocol with 1 mm overlap. Dosimetric parameters for PTV, lung and body are analyzed. Treatment planning protocol with 1 mm overlap of the adjacent fields does not considerably counteract possible underdosage of the target in the case studied. PTV-V95% is for example reduced from 95% for perfectly aligned fields to 90% and 91% for 2 mm and 1 mm gap, respectively. However, the risk of overdosage in PTV and in healthy soft tissue is increased when following the protocol with 1 mm overlap. A 3 mm overlap compared to 2 mm overlap results in an increase in maximum dose to PTV, PTV-D2%, from 113% to 121%. V120% for 'Body-PTV' is also increased from 5 cm3 to 14 cm3. A treatment planning protocol with 1 mm overlap does not considerably improve the coverage of PTV in the case of erroneous jaw positions causing gap between fields, but increases the overdosage in PTV and doses to healthy tissue, in the case of overlapping fields, for the case investigated.
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| 5. |
- Pettersson, Erik, 1987, et al.
(författare)
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Structure delineation in the presence of metal - A comparative phantom study using single and dual-energy computed tomography with and without metal artefact reduction
- 2019
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Ingår i: Physics and Imaging in Radiation Oncology. - : Elsevier BV. - 2405-6316. ; 9, s. 43-49
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Tidskriftsartikel (refereegranskat)abstract
- Background and purpose: Metal artefacts in computed tomography (CT) images impairs structure delineation. These artefacts can potentially be reduced with dual-energy CT (DECT) with or without using metal artefact reduction (MAR). The purpose was to investigate how structure delineation in DECT with or without MAR and single-energy CT (SECT) images were affected by metals. Materials and methods: A phantom with known irregular structures was developed. References tructures were determined from a low-noise scan without metal. Bilateral hip prostheses were simulated with steel or titanium inserts. The phantom was scanned with SECT and fast-kV switching DECT with optional MAR. Four radiation oncologists delineated the structures in two phantom set-ups. Delineated structures were evaluated with Dice similarity coefficient (DSC) and Hausdorff distance relative to the reference structures. Results: With titanium inserts, more structures were detected for non-MAR DECT compared to SECT while the same or less were detected with steel inserts. MAR improved delineation in DECT images. For steel inserts, Three structures in the region of artefacts, were delineated by at least two oncologists with MAR-DECT compared to none with non-MAR DECT or SECT. The highest values of DSC for MAR-DECT were 0.69, 0.81 and 0.77 for those structures. Conclusions: Delineation was improved with non-MAR DECT compared to SECT, especially for titanium inserts. A larger improvement was seen with the use of MAR for both steel and titanium inserts. The improvement was dependent on the location of the structure relative to the inserts, and the structure contrast relative to the background.
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| 6. |
- Sarudis, Sebastian, 1981, et al.
(författare)
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Evaluation of deformable image registration accuracy for CT images of the thorax region
- 2019
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Ingår i: Physica Medica-European Journal of Medical Physics. - : Elsevier BV. - 1120-1797. ; 57, s. 191-199
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: Evaluate the performance of three commercial deformable image registration (DIR) solutions on computed tomography (CT) image-series of the thorax. Methods: DIRs were performed on CT image-series of a thorax phantom with tumor inserts and on six 4-dimensional patient CT image-series of the thorax. The center of mass shift (CMS), dice similarity coefficient (DSC) and dose-volume-histogram (DVH) parameters were used to evaluate the accuracy. Dose calculations on deformed patient images were compared to calculations on un-deformed images for the gross tumor volume (GTV) (D-mean, D-98%), lung (V-20Gy,V-12Gy), heart and spinal cord (D-2%). Results: Phantom structures with constant volume and shifts <= 30 mm were reproduced with visually acceptable accuracy (DSC >= 0.91, CMS <= 0.9 mm) for all software solutions. Deformations including volume changes were less accurate with 9/12 DIRs considered visually unacceptable. In patients, organs were reproduced with DSC >= 0.83. GTV shifts <= 1.6 cm were reproduced with visually acceptable accuracy by all software while larger shifts resulted in failures for at least one of the software. In total, the best software succeeded in 18/25 DIRs while the worst succeeded in 12/25 DIRs. Visually acceptable DIRs resulted in deviations <= 3.0% of the prescribed dose and <= 3.6% of the total structure volume in the evaluated DVH-parameters. Conclusions: The take home message from the results of this study is the importance to have a visually acceptable registration. DSC and CMS are not predictive of the associated dose deviation. Visually acceptable DIRs implied dose deviations <= 3.0%.
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| 7. |
- Stervik, Louise, 1993, et al.
(författare)
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Modelling the risk of fatal acute toxicity following radiotherapy of lung cancer
- 2018
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Ingår i: Physica medica. Vol. 52, Suppl. 1, p. 30. 2nd European Congress of Medical Physics. - : Elsevier BV. - 1120-1797 .- 1724-191X.
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Konferensbidrag (refereegranskat)abstract
- Purpose:To model the risk of fatal acute toxicity after conventionally fractionated curative radiotherapy of patients with non-small-cell lung cancer (NSCLC). Methods:Scripting was used to automatically extract treatment-related data for all patients treated for NSCLC between 2008 and 2016 from three hospitals. Inclusion criteria were conventionally fractionated curative radiotherapy and no prior treatment in the thorax region. Maximum likelihood estimation and logistic regression (LR) were used to model the risk of fatal acute toxicity defined as death within 90 days from treatment start. Mean lung dose (MLD), patient age and the volume of the gross tumour volume (GTV) were investigated as predictors in a univariable LR analysis. We performed analysis on the data from the three hospitals separately and merged. Predictor variables were considered statistically significant if p < 0.05. All predictor variables with a p < 0.1 were further analysed in multivariable LR models. Confidence intervals (CIs) for the predictors were calculated using the likelihood ratio test. CIs for the multivariable models were calculated by bootstrapping. Results:Data was extracted for 848 patients. The incidence of death within 90 days from treatment start was 3.8% (32/848) for the merged data set and varied from 1.8% to 5.4% between hospitals. For the hospital with the highest incidence, a statistically significant relationship between MLD and the risk of fatal acute toxicity (p = 0.020) was found. The model parameters and their 95% CIs were D50=42.8 (31.4-167.7) Gy and γ50=1.20 (0.77-1.68). In the univariable LRs with patient age and GTV volume, patient age had p-values < 0.1 and GTV volume p-values > 0.2. Multivariable LR with MLD and patient age resulted in a statistically significant multivariable model (p = 0.005) for the merged data. The calculated risks and their 95% CIs for a patient with MLD = 20 Gy were 1.6% (0.5-3.3%), 2.8% (1.3-4.5%), 4.9% (3.1-6.8%), and 8.6% (4.8-13.5%) at 50, 60, 70, and 80 years of age, respectively. Conclusions:A statistically significant multivariable model quantifying the risk of fatal acute toxicity with MLD and patient age as predictor variables was found.
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| 8. |
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| 9. |
- Stock, M., et al.
(författare)
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Harmonization of proton treatment planning for head and neck cancer using pencil beam scanning: first report of the IPACS collaboration group
- 2019
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Ingår i: Acta Oncologica. - : Informa UK Limited. - 0284-186X .- 1651-226X. ; 58:12, s. 1720-1730
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Tidskriftsartikel (refereegranskat)abstract
- Background and purpose: A collaborative network between proton therapy (PT) centres in Trento in Italy, Poland, Austria, Czech Republic and Sweden (IPACS) was founded to implement trials and harmonize PT. This is the first report of IPACS with the aim to show the level of harmonization that can be achieved for proton therapy planning of head and neck (sino-nasal) cancer. Methods: CT-data sets of five patients were included. During several face-to-face and online meetings, a common treatment planning protocol was developed. Each centre used its own treatment planning system (TPS) and planning approach with some restrictions specified in the treatment planning protocol. In addition, volumetric modulated arc therapy (VMAT) photon plans were created. Results: For CTV1, the average D-median was 59.3 +/- 2.4 Gy(RBE) for protons and 58.8 +/- 2.0 Gy(RBE) for VMAT (aim was 56 Gy(RBE)). For CTV2, the average D-median was 71.2 +/- 1.0 Gy(RBE) for protons and 70.6 +/- 0.4 Gy(RBE) for VMAT (aim was 70 Gy(RBE)). The average D-2% for the spinal cord was 25.1 +/- 8.5 Gy(RBE) for protons and 47.6 +/- 1.4 Gy(RBE) for VMAT. The average D-2% for chiasm was 46.5 +/- 4.4 Gy(RBE) for protons and 50.8 +/- 1.4 Gy(RBE) for VMAT, respectively. Robust evaluation was performed and showed the least robust plans for plans with a low number of beams. Discussion: In conclusion, several influences on harmonization were identified: adherence/interpretation to/of the protocol, available technology, experience in treatment planning and use of different beam arrangements. In future, all OARs that should be included in the optimization need to be specified in order to further harmonize treatment planning.
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| 10. |
- Thurin, Erik, et al.
(författare)
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Proton therapy for low-grade gliomas in adults : A systematic review
- 2018
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Ingår i: Clinical neurology and neurosurgery (Dutch-Flemish ed. Print). - : Elsevier BV. - 0303-8467 .- 1872-6968. ; 174, s. 233-238
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Tidskriftsartikel (refereegranskat)abstract
- For adult patients with diffuse low-grade glioma (LGG) proton therapy is an emerging radiotherapy modality. The number of proton facilities is rapidly increasing. However, there is a shortage of published data concerning the clinical effectiveness compared to photon radiotherapy and potential proton-specific toxicity. This study aimed to systematically review and summarize the relevant literature on proton therapy for adult LGG patients, including dosimetric comparisons, the type and frequency of acute and long-term toxicity and the clinical effectiveness. A systematic search was performed in several medical databases and 601 articles were screened for relevance. Nine articles were deemed eligible for in-depth analysis using a standardized data collection form by two independent researchers. Proton treatment plans compared favorably to photon-plans regarding dose to uninvolved neural tissue. Fatigue (27-100%), alopecia (37-85%), local erythema (78-85%) and headache (27-75%) were among the most common acute toxicities. One study reported no significant long-term cognitive impairments. Limited data was available on long-term survival. One study reported a 5-year overall survival of 84% and 5-year progression-free survival of 40%. We conclude that published data from clinical studies using proton therapy for adults with LGG are scarce. As the technique becomes more available, controlled clinical studies are urgently warranted to determine if the potential benefits based on comparative treatment planning translate into clinical benefits.
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