| 1. |
- 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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| 2. |
- Lundman, Josef Axel, et al.
(författare)
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Patient-induced susceptibility effects simulation in magnetic resonance imaging
- 2017
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Ingår i: Physics and Imaging in Radiation Oncology. - : Elsevier. - 2405-6316. ; 1, s. 41-45
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Tidskriftsartikel (refereegranskat)abstract
- Background and purpose A fundamental requirement for safe use of magnetic resonance imaging (MRI) in radiotherapy is geometrical accuracy. One factor that can introduce geometrical distortion is patient-induced susceptibility effects. This work aims at developing a method for simulating these distortions. The specific goal being to help objectively identifying a balanced acquisition bandwidth, keeping these distortions within acceptable limits for radiotherapy.Materials and methods A simulation algorithm was implemented in Medical Interactive Creative Environment (MICE). The algorithm was validated by comparison between simulations and analytical solutions for a cylinder and a sphere. Simulations were performed for four body regions; neck, lungs, thorax with the lungs excluded, and the pelvic region. This was done using digital phantoms created from patient CT images, after converting the CT Hounsfield units to magnetic susceptibility values through interpolation between known values.Results The simulations showed good agreement with analytical solutions, with only small discrepancies due to pixelation of the phantoms. The calculated distortions in digital phantoms based on patient CT data showed maximal 95th percentile distortions of 39%, 32%, 28%, and 25% of the fat-water shift for the neck, lungs, thorax with the lungs excluded, and pelvic region, respectively.Conclusions The presented results show the expected pixel distortions for various body parts, and how they scale with bandwidth and field strength. This information can be used to determine which bandwidth is required to keep the patient-induced susceptibility distortions within an acceptable range for a given field strength.
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| 3. |
- Petersson, Kristoffer, et al.
(författare)
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A clinical distance measure for evaluating treatment plan quality difference with Pareto fronts in radiotherapy
- 2017
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Ingår i: Physics and imaging in radiation oncology. - : Elsevier BV. - 2405-6316. ; 3, s. 53-56
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Tidskriftsartikel (refereegranskat)abstract
- We present a clinical distance measure for Pareto front evaluation studies in radiotherapy, which we show strongly correlates (r = 0.74 and 0.90) with clinical plan quality evaluation. For five prostate cases, sub-optimal treatment plans located at a clinical distance value of >0.32 (0.28–0.35) from fronts of Pareto optimal plans, were assessed to be of lower plan quality by our (12) observers (p < .05). In conclusion, the clinical distance measure can be used to determine if the difference between a front and a given plan (or between different fronts) corresponds to a clinically significant plan quality difference.
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