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- Terzidis, Emmanouil, 1994, et al.
(författare)
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Assessing the fraction of dose originating from the penumbra region for plans of varied complexity
- 2024
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Ingår i: European Congress of Radiation Oncology (2024.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Purpose: The absorbed dose delivered to the patient that originates from a penumbra region have larger uncertainties compared to the dose delivered from the center of the treatment field. 1,2 The magnitude of these uncertainties could be important input when evaluating absorbed dose to organs at risk (OARs) and target volumes. The aim of this work was to examine the fraction of penumbra dose in three-dimensions (3D) for volumetric modulated arc therapy (VMAT) plans of different complexities. Methods and Materials: A C# software was developed in our department, able to calculate the fraction of penumbra dose in relation to the total dose in each voxel and visualize it as a 3D distribution (penumbra map). Twelve treatment plans of previously treated patients have been selected to represent different types of treatment geometry and different treatment sites (prostate, head & neck, lung and gynecological cancer). The clinical plan used for the actual treatment of the patient was reoptimized in Eclipse TPS (Varian Medical Systems, Palo Alto, CA), to create one plan with reduced complexity (“simple plan”) and one of higher complexity (“complex plan”). These additional plans were generated by altering the monitor unit constraint and the aperture shape controller level, while retaining a similar dose distribution. The fraction of penumbra dose was calculated for both the clinical and the newly generated plans creating in total 36 penumbra maps. Results: The generated penumbra maps were able to highlight anatomical regions with high fraction of penumbra dose (e.g., above 50%). These regions were mostly observed outside the planning target volume (PTV), regardless of treatment site and complexity level. Generally, the fraction of penumbra dose, both inside and outside the PTV, was increased with increased plan complexity. The average fraction of penumbra dose for the body, PTV and an example OAR are shown in Table 1 across all analyzed plans. For certain cases, the absorbed dose in parts of OARs originated from penumbra regions to a considerable degree, even for the least complex version of the plan. Examples are shown in Figure 1 featuring the rectum in a prostate plan and the parotid glands in a head & neck plan. Conclusion: The proposed method functions as a tool for assessing the extent to which the dose to certain voxels is influenced by the penumbra. A link was established between increased complexity and increased mean fraction of penumbra dose. Therefore, this approach could be used to quantify the complexity of the treatment plan in 3D
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| 2. |
- Terzidis, Emmanouil, 1994, et al.
(författare)
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Different aspects of plan complexity in prostate VMAT plans
- 2023
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Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6596.
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Konferensbidrag (refereegranskat)abstract
- In this work we evaluated VMAT plan complexity by using different methods and approaches: complexity related to the aperture shape, the nature of the dynamic delivery, the impact of delivery variations as well as complexity analyses based on measurements. Prostate cancer treatment plans with different levels of complexity were created for three different patient cases. The plans intended to be most complex were also scored to be the most complex according to the evaluation methods used. The results for the other plans were more diverse. The methods that included 3D spatial information on complexity gave additional information important for the analysis of clinical relevance. In order to use specific complexity estimation methods for taking clinical decisions it is essential to understand how different aspects of complexity are incorporated in each method.
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| 3. |
- Terzidis, Emmanouil, 1994
(författare)
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Head & neck squamous cell carcinoma: Comparison of multimodal imaging with pathological specimens
- 2022
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Ingår i: European Society Radiation Oncology (ESTRO) Congress 2022.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Purpose: In head and neck cancer, tumor volume is a major concern and despite development in imaging modalities, precise target definition remains a challenge. In this study, tumor volumes defined from multimodal imaging with PET/MRI are compared with the actual pathological tumor volumes from the surgical specimens. The mismatch between the volumes defined from imaging and pathology is estimated and the clinical impact of potential mismatch is evaluated. Methods and Materials: Twenty-eight patients with head and neck squamous cell carcinoma, were scanned on an integrated PET/MRI system, prior to surgery. Three GTV’s were delineated defined from the MRI (GTVMRI), the PET (GTVPET) and one by utilizing both anatomical images and clinical information (GTVONCO). Thirty-three specimens were extracted en bloc and scanned with the same PET/MRI and were co-registered to the patient images based on predefined anatomical landmarks. Each specimen was sectioned in blocks, which were then sliced (4-µm thick) and stained with haematoxylin and eosin. All slices were digitalized, scanned and assessed by a trained head and neck pathologist. The pathological tumor areas for each tumor were interpolated yielding a pathological 3D tumor volume (GTVPATO), which was imported in Eclipse TPS (Varian Medical Systems, Palo Alto, CA) as a structure. The GTVPATO was compared with the GTV’s defined from imaging. Additionally, the mismatch between GTV’s were assessed by dividing the GTVPATO that is outside the imaging GTV with the whole volume of the corresponding GTV. To validate current practice of a 5 mm CTV expansion, a margin of 5 mm was added to the GTVONCO and the mismatch was re-assessed. Results: For consistency, only T-sites were included in this analysis (N=27). Further thirteen patients were excluded before the analysis, because fragmentation of the specimen during histologic processing or poor interpolation and insufficient number of points to form a structure in Eclipse. For the fourteen patients that were included in the analysis the mean volume of the GTVONCO was larger than the other GTV’s. In four patients the GTVPATO was larger than the GTVMRI and for one patient the GTVPATO was larger than the GTVPET. The mean mismatch of the GTVPATO when evaluated to the GTVPET, GTVMRI and GTVONCO was 29.7%, 39.5% and 7.5% respectively (Table 1). However, after the addition of 5mm margin all GTVPATO’s were encompassed in GTVONCO. Conclusions: GTV was defined differently with different imaging modalities and a mismatch with the pathological tumor volume was observed in thirteen of the fourteen included patients. For all patients, 5mm margin appears sufficient to ensure that all of the pathological information will be included during treatment.
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| 4. |
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| 5. |
- Terzidis, Emmanouil, 1994, et al.
(författare)
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Tumor volume definitions in head and neck squamous cell carcinoma - Comparing PET/MRI and histopathology
- 2023
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Ingår i: Radiotherapy and Oncology. - : Elsevier BV. - 0167-8140. ; 180
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Tidskriftsartikel (refereegranskat)abstract
- Background and purpose: In cancer treatment precise definition of the tumor volume is essential, but despite development in imaging modalities, this remains a challenge. Here, pathological tumor volumes from the surgical specimens were obtained and compared to tumor volumes defined from modern PET/ MRI hybrid imaging. The purpose is to evaluate mismatch between the volumes defined from imaging and pathology was estimated and potential clinical impact.Methods and Materials: Twenty-five patients with head and neck squamous cell carcinoma were scanned on an integrated PET/MRI system prior to surgery. Three gross tumor volumes (GTVs) from the primary tumor site were delineated defined from MRI (GTVMRI), PET (GTVPET) and one by utilizing both anatomical images and clinical information (GTVONCO). Twenty-five primary tumor specimens were extracted en bloc, scanned with PET/MRI and co-registered to the patient images. Each specimen was sectioned in blocks, sliced and stained with haematoxylin and eosin. All slices were digitalized and tumor delineated by a head and neck pathologist. The pathological tumor areas in all slices were interpolated yielding a pathological 3D tumor volume (GTVPATO). GTVPATO was compared with the imaging GTV's and potential mismatch was estimated.Results: Thirteen patients were included. The mean volume of GTVONCO was larger than the GTV's defined from PET or MRI. The mean mismatch of the GTVPATO compared to the GTVPET, GTVMRI and GTVONCO was 31.9 %, 54.5 % and 27.9 % respectively, and the entire GTVPATO was only fully encompassed in GTVONCO in 1 of 13 patients. However, after the addition of a clinical 5 mm margin the GTVPATO was fully encompassed in GTVONCO in 11 out of 13 patients.Conclusions: Despite modern hybrid imaging modalities, a mismatch between imaging and pathological defined tumor volumes was observed in all patients. A 5 mm clinical margin was sufficient to ensure inclusion of the entire pathological volume in 11 out of 13 patients.(c) 2023 The Authors. Published by Elsevier B.V. Radiotherapy and Oncology 180 (2023) 1-8 This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
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| 6. |
- Terzidis, Emmanouil, 1994, et al.
(författare)
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Uppskattning av dosimetriska osäkerheter baserat på andel dos från penumbraregionen för VMAT-planer av olika komplexitet
- 2023
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Ingår i: Nationellt möte om sjukhusfysik 2023.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Absorbed dose delivered to the patient from a penumbra region have higher uncertainties compared to the dose delivered from the center of the treatment field. The magnitude of these uncertainties could be important input when evaluating absorbed dose to organs at risk (OARs) and target volumes, especially for plans of increased complexity. The aim of this work was to examine the fraction of penumbra dose in 3D for VMAT plans of different complexities. Methods and Materials: A C# software was developed in our department, able to estimate the fraction of penumbral dose in relation to the total dose, in each voxel and visualize it as a 3D distribution (uncertainty map). Twelve treatment plans of previously treated patients have been selected to represent different types of treatment geometry and different types of diagnose (prostate, head & neck, lung and gynecological cancer). The clinical plan used for the actual treatment of the patient was reoptimized in Eclipse TPS (Varian Medical Systems, Palo Alto, CA), to create one plan with reduced complexity (“simple plan”) and one of higher complexity (“complex plan”). These additional plans were generated by altering the MU constraint and the aperture shape controller (ASC) level, while retaining a similar dose distribution. The fraction of penumbra dose was calculated for both the clinical and the newly generated plans creating in total 36 uncertainty maps. Results: The generated uncertainty maps were able to highlight anatomical regions with high fraction of penumbra dose (e.g., above 50%). These regions were mostly observed outside the planning target volume (PTV). Generally, the fraction of penumbra dose, both inside and outside the PTV, was increased with increased plan complexity. For certain cases, the absorbed dose in OARs originated from penumbra regions to a considerable degree, even for the least complex version of the plan. An example is shown for the rectum in Figure 1. This observation proves the importance of evaluating dosimetric uncertainty in 3D. Conclusion: A connection was established between dose uncertainty due to fraction of penumbra dose and plan complexity. Furthermore, it is important to evaluate this uncertainty on a 3D-voxel-level.
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