| 1. |
- Ceberg, Sofie, et al.
(författare)
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Evaluation of breathing interplay effects during VMAT by using 3D gel measurements
- 2013
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Ingår i: 7th International Conference on 3D Radiation Dosimetry (IC3DDose). - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 444, s. 012098-012098
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Konferensbidrag (refereegranskat)abstract
- Respiratory motion during dynamic radiotherapy may affect the absorbed dose distribution both by dose-reducing smoothing and by more complicated interplay effects. In this study we present a novel method to determine the relative importance of these two effects. For the two dynamic deliveries studied in this work, the expected target dose reduction due to the smoothing effect was estimated by measurements convolved by the motion function. Remaining absorbed dose differences were attributed to interplay effects between the motion of the gel phantom and the movement of the modulating MLC leaves during modulated arc radiotherapy. The total dosimetric effect due to breathing motion and dynamic MLC motion during VMAT delivery resulted in an average of about 4% target dose reduction. Comparing with only the smoothing effect, the average difference was decreased to around 1%, and the remaining distribution was attributed to interplay effects. Although the interplay effects were small compared to the smoothing effect, the standard deviations of 1.4-2.3% (1SD) were larger than the narrow distribution for repeated stationary measurement with a standard deviation between 0.5-0.9% (1SD).
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| 2. |
- Ceberg, Sofie, et al.
(författare)
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Modelling the dynamic dose response of an nMAG polymer gel dosimeter.
- 2012
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Ingår i: Physics in Medicine and Biology. - : IOP Publishing. - 1361-6560 .- 0031-9155. ; 57:15, s. 4845-4853
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Tidskriftsartikel (refereegranskat)abstract
- Gel dosimetry measures the absorbed radiation dose with high spatial resolution in 3D. However, recently published data show that the response of metacrylic-based polymer gels depends on the segmented delivery pattern, which could potentially be a considerable disadvantage for measurements of modern dynamic radiotherapy techniques. The aim of this study is to design a dynamic compartment model for the response of a gel dosimeter, exposed to an arbitrary irradiation pattern (segmented delivery and intensity modulation), in order to evaluate the associated effects on absorbed dose measurements. The model is based on the separation of the protons affecting the magnetic resonance signal (i.e. the R2 value) into six compartments, described by a set of differential equations. The model is used to calculate R2 values for a number of different segmented delivery patterns between 0-4 Gy over 1-33 fractions. Very good agreement is found between calculated and measured R2 values, with an average difference of 0.3 ± 1.1% (1 SD). The model is also used to predict the behaviour of a gel dosimeter exposed to irradiation according to typical IMRT, VMAT and respiratory gating scenarios. The calculated R2 values are approximately independent of the segmented delivery, given that the same total dose is delivered during the same total time. It is concluded that this study helps to improve the theoretical understanding of the dependence of metacrylic-based polymer gel response to segmented radiation delivery.
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| 3. |
- Edvardsson, Anneli, et al.
(författare)
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Motion induced interplay effects for VMAT radiotherapy
- 2018
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Ingår i: Physics in Medicine and Biology. - : IOP Publishing. - 0031-9155 .- 1361-6560. ; 63:8
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this study was to develop a method to simulate breathing motion induced interplay effects for volumetric modulated arc therapy (VMAT), to verify the proposed method with measurements, and to use the method to investigate how interplay effects vary with different patient-and machine specific parameters. VMAT treatment plans were created on a virtual phantom in a treatment planning system (TPS). Interplay effects were simulated by dividing each plan into smaller sub-arcs using an in-house developed software and shifting the isocenter for each sub-arc to simulate a sin(6) breathing motion in the superior-inferior direction. The simulations were performed for both flattening-filter (FF) and flattening-filter free (FFF) plans and for different breathing amplitudes, period times, initial breathing phases, dose levels, plan complexities, CTV sizes, and collimator angles. The resulting sub-arcs were calculated in the TPS, generating a dose distribution including the effects of motion. The interplay effects were separated from dose blurring and the relative dose differences to 2% and 98% of the CTV volume (Delta D-98% and Delta D-2%) were calculated. To verify the simulation method, measurements were carried out, both static and during motion, using a quasi-3D phantom and a motion platform. The results of the verification measurements during motion were comparable to the results of the static measurements. Considerable interplay effects were observed for individual fractions, with the minimum Delta D-98% and maximum Delta D-2% being - 16.7% and 16.2%, respectively. The extent of interplay effects was larger for FFF compared to FF and generally increased for higher breathing amplitudes, larger period times, lower dose levels, and more complex treatment plans. Also, the interplay effects varied considerably with the initial breathing phase, and larger variations were observed for smaller CTV sizes. In conclusion, a method to simulate motion induced interplay effects was developed and verified with measurements, which allowed for a large number of treatment scenarios to be investigated. The simulations showed large interplay effects for individual fractions and that the extent of interplay effects varied with the breathing pattern, FFF/FF, dose level, CTV size, collimator angle, and the complexity of the treatment plan.
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| 4. |
- Edvardsson, Anneli, et al.
(författare)
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Verification of motion induced thread effect during tomotherapy using gel dosimetry
- 2015
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Ingår i: 8th International Conference on 3D Radiation Dosimetry (IC3DDOSE). - : IOP Publishing. - 1742-6596 .- 1742-6588. ; 573, s. 012048-012048
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Konferensbidrag (refereegranskat)abstract
- The purpose of the study was to evaluate how breathing motion during tomotherapy (Accuray, CA, USA) treatment affects the absorbed dose distribution. The experiments were carried out using gel dosimetry and a motion device simulating respiratory-like motion (HexaMotion, ScandiDos, Uppsala, Sweden). Normoxic polyacrylamide gels (nPAG) were irradiated, both during respiratory-like motion and in a static mode. To be able to investigate interplay effects the static absorbed dose distribution was convolved with the motion function and differences between the dynamic and convolved static absorbed dose distributions were interpreted as interplay effects. The expected dose blurring was present and the interplay effects formed a spiral pattern in the lower dose volume. This was expected since the motion induced affects the preset pitch and the theoretically predicted thread effect may emerge. In this study, the motion induced thread effect was experimentally verified for the first time.
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| 5. |
- Haraldsson, André, et al.
(författare)
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Surface-guided tomotherapy improves positioning and reduces treatment time : A retrospective analysis of 16 835 treatment fractions
- 2020
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Ingår i: Journal of Applied Clinical Medical Physics. - : Wiley. - 1526-9914. ; 21:8, s. 139-148
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: In this study, we have quantified the setup deviation and time gain when using fast surface scanning for daily setup/positioning with weekly megavoltage computed tomography (MVCT) and compared it to daily MVCT. Methods: A total of 16 835 treatment fractions were analyzed, treated, and positioned using our TomoTherapy HD (Accuray Inc., Madison, USA) installed with a Sentinel optical surface scanning system (C-RAD Positioning AB, Uppsala, Sweden). Patients were positioned using in-room lasers, surface scanning and MVCT for the first three fractions. For the remaining fractions, in-room laser was used for setup followed by daily surface scanning with MVCT once weekly. The three-dimensional (3D) setup correction for surface scanning was evaluated from the registration between MVCT and the planning CT. The setup correction vector for the in-room lasers was assessed from the surface scanning and the MVCT to planning CT registration. The imaging time was evaluated as the time from imaging start to beam-on. Results: We analyzed 894 TomoTherapy treatment plans from 2012 to 2018. Of all the treatment fractions performed with surface scanning, 90 % of the residual errors were within 2.3 mm for CNS (N = 284), 2.9 mm for H&N (N = 254), 8.7 mm for thorax (N = 144) and 10.9 for abdomen (N = 134) patients. The difference in residual error between surface scanning and positioning with in-room lasers was significant (P < 0.005) for all sites. The imaging time was assessed as total imaging time per treatment plan, modality, and treatment site and found that surface scanning significantly reduced patient on-couch time compared to MVCT for all treatment sites (P < 0.005). Conclusions: The results indicate that daily surface scanning with weekly MVCT can be used with the current target margins for H&N, CNS, and thorax, with reduced imaging time.
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| 6. |
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| 7. |
- Mannerberg, Annika, et al.
(författare)
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Surface guided electron FLASH radiotherapy for canine cancer patients
- 2023
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Ingår i: Medical Physics. - 0094-2405. ; 50:7, s. 4047-4054
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundDuring recent years FLASH radiotherapy (FLASH-RT) has shown promising results in radiation oncology, with the potential to spare normal tissue while maintaining the antitumor effects. The high speed of the FLASH-RT delivery increases the need for fast and precise motion monitoring to avoid underdosing the target. Surface guided radiotherapy (SGRT) uses surface imaging (SI) to render a 3D surface of the patient. SI provides real-time motion monitoring and has a large scanning field of view, covering off-isocentric positions. However, SI has so far only been used for human patients with conventional setup and treatment.PurposeThe aim of this study was to investigate the performance of SI as a motion management tool during electron FLASH-RT of canine cancer patients.MethodsTo evaluate the SI system's ability to render surfaces of fur, three fur-like blankets in white, grey, and black were used to imitate the surface of canine patients and the camera settings were optimized for each blanket. Phantom measurements using the fur blankets were carried out, simulating respiratory motion and sudden shift. Respiratory motion was simulated using the QUASAR Respiratory Motion Phantom with the fur blankets placed on the phantom platform, which moved 10 mm vertically with a simulated respiratory period of 4 s. Sudden motion was simulated with an in-house developed phantom, consisting of a platform which was moved vertically in a stepwise motion at a chosen frequency. For sudden measurements, 1, 2, 3, 4, 5, 6, 7, and 10 Hz were measured. All measurements were both carried out at the conventional source-to-surface distance (SSD) of 100 cm, and in the locally used FLASH-RT setup at SSD = 70 cm. The capability of the SI system to reproduce the simulated motion and the sampling time were evaluated. As an initial step towards clinical implementation, the feasibility of SI for surface guided FLASH-RT was evaluated for 11 canine cancer patients.ResultsThe SI camera was capable of rendering surfaces for all blankets. The deviation between simulated and measured mean peak-to-peak breathing amplitude was within 0.6 mm for all blankets. The sampling time was generally higher for the black fur than for the white and grey fur, for the measurement of both respiratory and sudden motion. The SI system could measure sudden motion within 62.5 ms and detect motion with a frequency of 10 Hz. The feasibility study of the canine patients showed that the SI system could be an important tool to ensure patient safety. By using this system we could ensure and document that 10 out of 11 canine patients had a total vector offset from the reference setup position ConclusionsWe have shown that SI can be used for surface guided FLASH-RT of canine patients. The SI system is currently not fast enough to interrupt a FLASH-RT beam while irradiating but with the short sampling time sudden motion can be detected. The beam can therefore be held just prior to irradiation, preventing treatment errors such as underdosing the target.
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| 8. |
- Nordström, Fredrik, et al.
(författare)
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3D geometric gel dosimetry verification of intraprostatic fiducial guided hypofractionated radiotherapy of prostate cancer
- 2010
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Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6596. ; 250, s. 287-291
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Konferensbidrag (refereegranskat)abstract
- This pre-study is aimed to investigate the feasibility of a normoxic polyacrylamide gel (nPAG) dosimeter with implanted gold fiducials to evaluate the geometric precision, including setup correction strategies, in the delivery of hypofractionated treatments. For this purpose a phantom consisting of three parts was constructed: (1) the patient simulating volume, providing realistic scatter conditions and weight, (2) a bottle containing the active dosimetric volume and (3) the gold fiducials and the fiducial support structure. A 6.1 Gy prostate IMRT treatment was delivered to the phantom using the sliding-window technique. The phantom was positioned prior to the treatment using the implanted fiducials and kV on-board imaging. An overlay of the 95% isosurface of the TPS calculated dose distribution and the measured dose distribution using gel showed good agreement. The clinical target volume (CTV) was well centred inside the 95% isodose surface of the measured volume. It was shown for the evaluated case that the use of on-board imaging and integrated setup correction tools could be used to compensate for a deliberately introduced offset in CTV position. The study showed that MRI based nPAG gel dosimetry can be used to verify setup correction procedures using implanted gold fiducials.
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| 9. |
- Abdollahi, Sara, et al.
(författare)
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A dose planning study for cardiac and lung dose sparing techniques in left breast cancer radiotherapy : Can free breathing helical tomotherapy be considered as an alternative for deep inspiration breath hold?
- 2023
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Ingår i: Technical Innovations and Patient Support in Radiation Oncology. - : Elsevier BV. - 2405-6324. ; 25
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: To investigate the possibility to be able to offer left sided breast cancer patients, not suitable for DIBH, an organ at risk saving treatment. Materials and Methods: Twenty patients receiving radiotherapy for left breast cancer in DIBH were enrolled in the study. Planning CT scans were acquired in the same supine treatment position in FB and DIBH. 3DCRT_DIBH plans were designed and optimized using two parallel opposed tangent beams (with some additional segments) for the breast and chest wall and anterior-posterior fields for regional lymph nodes irradiation. Additionally, FB helical tomotherapy plans were optimized to minimize heart and lung dose. All forty plans were optimized with at least 95% of the total CTV covered by the 95% of prescribed dose of 50 Gy in 25 fractions. Results: HT_FB plans showed significantly better dose homogeneity and conformity compared to the 3DCRT_DIBH specially for regional nodal irradiation. The heart mean dose was almost comparable in 3DCRT_DIBH and HT_FB while the volume (%) of the heart receiving 25 Gy had a statistically significant reduction from 7.90 ± 3.33 in 3DCRT_DIBH to 0.88 ± 0.66 in HT_FB. HT_FB was also more effective in left descending artery (LAD) mean dose reduction about 100% from 30.83 ± 9.2 Gy to 9.7 ± 3.1. The ipsilateral lung volume receiving 20 Gy has a further reduction of 43 % in HT_FB compared with 3DCRT_DIBH. For low dose comparison, 3DCRT_DIBH was superior for contralateral organ sparing compared to the HT_FB due to the limited angle for dose delivery. Conclusion: For patients who cannot be a candidate for DIBH for any reason, HT in free breathing may be a good alternative and provides heart and ipsilateral lung dose sparing, however with the cost of increased dose to contralateral breast and lung.
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| 10. |
- Abdollahi, Sara, et al.
(författare)
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Dynamic anthropomorphic thorax phantom for quality assurance of motion management in radiotherapy
- 2024
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Ingår i: Physics and imaging in radiation oncology. - 2405-6316. ; 30
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Tidskriftsartikel (refereegranskat)abstract
- Background and purpose: Motion management techniques are important to spare the healthy tissue adequately. However, they are complex and need dedicated quality assurance. The aim of this study was to create a dynamic phantom designed for quality assurance and to replicate a patient's size, anatomy, and tissue density. Materials and methods: A computed tomography (CT) scan of a cancer patient was used to create molds for the lungs, heart, ribs, and vertebral column via additive manufacturing. A pump system and software were developed to simulate respiratory dynamics. The extent of respiratory motion was quantified using a 4DCT scan. End-to-end tests were conducted to evaluate two motion management techniques for lung stereotactic body radiotherapy (SBRT). Results: The chest wall moved between 4 mm and 13 mm anteriorly and 2 mm to 7 mm laterally during the breathing. The diaphragm exhibited superior-inferior movement ranging from 5 mm to 16 mm in the left lung and 10 mm to 36 mm in the right lung. The left lung tumor displaced ± 7 mm superior-inferiorly and anterior-posteriorly. The CT numbers were for lung: −716 ± 108 HU (phantom) and −713 ± 70 HU (patient); bone: 460 ± 20 HU (phantom) and 458 ± 206 HU (patient); soft tissue: 92 ± 9 HU (phantom) and 60 ± 25 HU (patient). The end-to-end testing showed an excellent agreement between the measured and the calculated dose for ion chamber and film dosimetry. Conclusions: The phantom is recommended for quality assurance, evaluating the institution's specific planning and motion management strategies either through end-to-end testing or as an external audit phantom.
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| 11. |
- Abdollahi, Sara, et al.
(författare)
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Surface guided 3DCRT in deep-inspiration breath-hold for left sided breast cancer radiotherapy : implementation and first clinical experience in Iran
- 2022
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Ingår i: Reports of Practical Oncology and Radiotherapy. - 1507-1367. ; 27:5, s. 881-896
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Tidskriftsartikel (refereegranskat)abstract
- Background: The aim of the study is to evaluate the overall accuracy of the surface-guided radiotherapy (SGRT) workflow through a comprehensive commissioning and quality assurance procedures and assess the potential benefits of deep-inspiration breath-hold (DIBH) radiotherapy as a cardiac and lung dose reduction approach for left-sided breast cancer irradiation. Materials and methods: Accuracy and reproducibility of the optical surface scanner used for DIBH treatment were evaluated using different phantoms. Patient positioning accuracy and reproducibility of DIBH treatment were evaluated. Twenty patients were studied for treatment plan quality in target dose coverage and healthy organ sparing for the two different treatment techniques. Results: Reproducibility tests for the surface scanner showed good stability within 1 mm in all directions. The maximum position variation between applied shifts on the couch and the scanner measured offsets is 1 mm in all directions. The clinical study of 200 fractions showed good agreement between the surface scanner and portal imaging with the isocenter position deviation of less than 3 mm in each lateral, longitudinal, and vertical direction. The standard deviation of the DIBH level showed a value of < 2 mm during all evaluated DIBHs. Compared to the free breathing (FB) technique, DIBH showed significant reduction of 48% for heart mean dose, 43% for heart V25, and 20% for ipsilateral lung V20. Conclusion: Surface-guided radiotherapy can be regarded as an accurate tool for patient positioning and monitoring in breast radiotherapy. DIBH treatment are considered to be effective techniques in heart and ipsilateral lung dose reductions for left breast radiotherapy.
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| 12. |
- Adjeiwaah, Mary, 1980-
(författare)
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Quality assurance for magnetic resonance imaging (MRI) in radiotherapy
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The use of Magnetic Resonance Imaging (MRI) in the radiotherapy (RT) treatment planning workflow is increasing. MRI offers superior soft-tissue contrast compared to Computed Tomography (CT) and therefore improves the accuracy in target volume definitions. There are, however concerns with inherent geometric distortions from system- (gradient nonlinearities and main magnetic field inhomogeneities) and patient-related sources (magnetic susceptibility effect and chemical shift). The lack of clearly defined quality assurance (QA) procedures has also raised questions on the ability of current QA protocols to detect common image quality degradations under radiotherapy settings. To fully implement and take advantage of the benefits of MRI in radiotherapy, these concerns need to be addressed.In Papers I and II, the dosimetric impact of MR distortions was investigated. Patient CTs (CT) were deformed with MR distortion vector fields (from the residual system distortions after correcting for gradient nonlinearities and patient-induced susceptibility distortions) to create distorted CT (dCT) images. Field parameters from volumetric modulated arc therapy (VMAT) treatment plans initially optimized on dCT data sets were transferred to CT data to compute new treatment plans. Data from 19 prostate and 21 head and neck patients were used for the treatment planning. The dCT and CT treatment plans were compared to determine the impact of distortions on dose distributions. No clinically relevant dose differences between distorted CT and original CT treatment plans were found. Mean dose differences were < 1.0% and < 0.5% at the planning target volume (PTV) for the head and neck, and prostate treatment plans, respectively. Strategies to reduce geometric distortions were also evaluated in Papers I and II. Using the vendor-supplied gradient non-linearity correction algorithm reduced overall distortions to less than half of the original value. A high acquisition bandwidth of 488 Hz/pixel (Paper I) and 488 Hz/mm (Paper II) kept the mean geometric distortions at the delineated structures below 1 mm. Furthermore, a patient-specific active shimming method implemented in Paper II significantly reduced the number of voxels with distortion shifts > 2 mm from 15.4% to 2.0%.B0 maps from patient-induced magnetic field inhomogeneities obtained through direct measurements and by simulations that used MR-generated synthetic CT (sCT) data were compared in Paper III. The validation showed excellent agreement between the simulated and measured B0 maps.In Paper IV, the ability of current QA methods to detect common MR image quality degradations under radiotherapy settings were investigated. By evaluating key image quality parameters, the QA protocols were found to be sensitive to some of the introduced degradations. However, image quality issues such as those caused by RF coil failures could not be adequately detected.In conclusion, this work has shown the feasibility of using MRI data for radiotherapy treatment planning as distortions resulted in a dose difference of less than 1% between distorted and undistorted images. The simulation software can be used to produce accurate B0 maps, which could then be used as the basis for the effective correction of patient-induced field inhomogeneity distortions and for the QA verification of sCT data. Furthermore, the analysis of the strengths and weaknesses in current QA tools for MRI in RT contribute to finding better methods to efficiently identify image quality errors.
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| 13. |
- Ceberg, Crister, et al.
(författare)
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Performance of sulfhydryl boron hydride in patients with grade III and IV astrocytoma: a basis for boron neutron capture therapy
- 1995
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Ingår i: Journal of Neurosurgery. - 0022-3085. ; 83:1, s. 79-85
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Tidskriftsartikel (refereegranskat)abstract
- This study investigated the rationale of boron neutron capture therapy (BNCT) for the treatment of Grade III and IV astrocytoma. The European Community joint research program on BNCT plans to use sulfhydryl boron hydride (BSH) in clinical trials. The work presented here, examines the performance of BSH in eight patients with Grade III and IV astrocytoma using a measurement technique which precisely correlates the boron uptake with the histology of the tumor and the peritumoral brain. Astrocytomas are exceptionally heterogeneous and spread migrating tumor cells into the surrounding brain. The patients were infused with 50 mg BSH per kilogram of body weight at 12, 18, 24 or 48 hours before surgery. At the time of operation, specimens were obtained of the tumor, skin, muscle, dura, blood, urine, and, when surgically possible, the brain adjacent to tumor. In three patients the intracellular boron distribution was investigated by subcellular fractionation. The blood clearance was biphasic with half-lives of 0.6 and 8.2 hours. After 3 days, approximately 70% of the dose injected was excreted in the urine. The maximum boron concentration in the tumor was 20 ppm, 12 hours after the infusion. The tumor-to-blood ratios ranged between 0.2 and 1.4, with the highest values after 18 to 24 hours. In the brain specimens the boron concentration never exceeded 1 ppm. This work confirms a selective uptake of boron in the tumor compared to the surrounding brain and that boron, to some extent, is incorporated in the tumor cells.
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| 14. |
- Ceberg, Sofie
(författare)
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3D Verification of Dynamic and Breathing Adapted Radiotherapy using Polymer Gel Dosimetry
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Polymer gel dosimetry has been used since the 1990s, and several studies have shown that this detector system can be used for verification of static absorbed dose distributions in three dimensions (3D). Its unique properties, such as high resolution, normal tissue equivalence and independency of energy, field size and direction of the incident radiation, should also be advantageous for dosimetric verification of radiotherapy using today’s and tomorrow’s dynamic delivery techniques. However, unfavourable properties have also been reported, such as dose rate-, temperature-, oxygen contamination-, and cooling rate dependencies. It has been shown in this thesis that these shortcomings can be overcome by using a good practice strategy, and that results can be obtained with an uncertainty comparable to other detector systems. Modern dynamic treatment techniques such as for example breathing adapted radiotherapy have created a need for dosimetry during motion, which poses new challenges. The purpose of this thesis was to investigate the performance of polymer gel dosimetry in such situations. For comparison, measurements using 1D, 2D and quasi-3D detector systems, as well as Monte Carlo simulations, were used to validate the results obtained using gel dosimetry. The absorbed dose integrating property during fractionated irradiation delivery was investigated for two different polymer gel systems. A fractionation dependency was observed, especially pronounced for one of the systems. This effect was further investigated using compartment modelling. The results indicated that the dose response was approximately independent of the fractionation scheme, provided that the total absorbed dose was delivered during the same total delivery time. Under respiratory-like motion no influence of the dose rate variation related to motion in and out of the beam was observed. Full 3D absorbed dose verifications were also carried out for advanced delivery techniques involving simultaneous beam intensity modulation and gantry rotation around the patient, so called volumetric modulated arc therapy (VMAT). Using both gel measurements and Monte Carlo simulations it was successfully demonstrated that the VMAT plan was both accurately calculated and delivered as planned. Additionally, the performance of a tumour-tracking system during VMAT delivery was investigated. The dosimetric measurements, obtained using both gel and a bi-planar diode array, verified the improved dose conformity when enabling the target tracking system. In this thesis the unique 3D properties of gel dosimetry were fully utilized, and the known uncertainties were minimized in every step of the procedure. It was shown that polymer gel is a useful tool for relative 3D dosimetry in dynamic and breathing adaptive radiotherapy.
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| 15. |
- Ceberg, Sofie, et al.
(författare)
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Dosimetric verification of breathing adapted radiotherapy using polymer gel
- 2006
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Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6596 .- 1742-6588. ; 56:1, s. 300-303
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Konferensbidrag (refereegranskat)abstract
- In radiation therapy patient movement caused by respiration can be a major challenge to the ambition to deliver a high absorbed dose to the target volume while minimizing the dose to normal tissues. Large respiratory motion requires increased margins, which implies an increased risk of morbidity from late toxicity. It is therefore important to take respiratory motion into account when treating targets in the thorax region. The aim of this study was to investigate the feasibility of using a 3D gel dosimeter for dose verification of breathing adapted radiotherapy
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| 16. |
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| 17. |
- Ceberg, Sofie, et al.
(författare)
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Radiotherapy delivery during motion
- 2010
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Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 250
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Tidskriftsartikel (refereegranskat)abstract
- This paper discusses the 3D dosimetric consequences of radiotherapy delivery during two kinds of motion, (i) the respiratory motion by the patient and (ii) the motion by the gantry while rotating around the patient. Respiratory motion primarily compromises treatments in the thorax and abdomen regions. Several strategies to reduce respiratory motion effects have been developed or are under development. The organ motion could for instance be measured and incorporated in the treatment planning, or adapted to by using respiratory gating and tumour-tracking delivery techniques. Gantry motion is involved in various forms of intensity-modulated arc-therapy techniques. The purpose is to increase the modulation by simultaneously varying the MLC positions, the rotation speed of the gantry, and the dose rate during the treatment. The advantage of these techniques is the increased possibility to deliver a high absorbed dose to the target volume while minimizing the dose to normal tissues. However, the dosimetric uncertainties associated with motion, small fields and steep dose gradients, has to be evaluated in detail, and this requires adequate true 3D dose-verification tools.
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| 18. |
- Ceberg, Sofie, et al.
(författare)
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RapidArc treatment verification in 3D using polymer gel dosimetry and Monte Carlo simulation.
- 2010
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Ingår i: Physics in Medicine and Biology. - : IOP Publishing. - 1361-6560 .- 0031-9155. ; 55:17, s. 4885-4898
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to verify the advanced inhomogeneous dose distribution produced by a volumetric arc therapy technique (RapidArc) using 3D gel measurements and Monte Carlo (MC) simulations. The TPS (treatment planning system)-calculated dose distribution was compared with gel measurements and MC simulations, thus investigating any discrepancy between the planned dose delivery and the actual delivery. Additionally, the reproducibility of the delivery was investigated using repeated gel measurements. A prostate treatment plan was delivered to a 1.3 liter nPAG gel phantom using one single arc rotation and a target dose of 3.3 Gy. Magnetic resonance imaging of the gel was carried out using a 1.5 T scanner. The MC dose distributions were calculated using the VIMC-Arc code. The relative absorbed dose differences were calculated voxel-by-voxel, within the volume enclosed by the 90% isodose surface (VOI(90)), for the TPS versus gel and TPS versus MC. The differences between the verification methods, MC versus gel, and between two repeated gel measurements were investigated in the same way. For all volume comparisons, the mean value was within 1% and the standard deviation of the differences was within 2.5% (1SD). A 3D gamma analysis between the dose matrices were carried out using gamma criteria 3%/3 mm and 5%/5 mm (% dose difference and mm distance to agreement) within the volume enclosed by the 50% isodose surface (VOI(50)) and the 90% isodose surface (VOI(90)), respectively. All comparisons resulted in very high pass rates. More than 95% of the TPS points were within 3%/3 mm of both the gel measurement and MC simulation, both inside VOI(50) and VOI(90). Additionally, the repeated gel measurements showed excellent consistency, indicating reproducible delivery. Using MC simulations and gel measurements, this verification study successfully demonstrated that the RapidArc plan was both accurately calculated and delivered as planned.
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| 19. |
- Ceberg, Sofie, et al.
(författare)
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RapidArc™ treatment verification using polymer gel dosimetry
- 2009
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Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 164:1
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to verify a novel volumetric arc therapy technique, RapidArc". Polymer gel dosimetry system was used to measure the advanced inhomogeneous 3D dose distribution produced using the technique RapidArc". A preclinical installation of the novel beam delivery approach was set up on a linear accelerator at Rigshospitalet in Copenhagen. A prostate treatment plan was delivered to a 1.3 l nPAG gel phantom using one single arc rotation from 200 to 160 degrees, and a target dose of 3.3 Gy. Magnetic resonance imaging of the gel was carried out using the 1.5 T scanner and MATLAB was used for image processing and 3D rendering. The difference in relative absorbed dose between the treatment planning system (TPS) and gel measurement was calculated voxel by voxel within the 80% and the 95% isodose volume, respectively. Measurements agreed well with the TPS within the treated volume. Within both isodose volumes 90% of the voxels showed a deviation less or equal to 5%. This study shows that the 3D gel dosimetry system is a useful tool for dose verification of advanced treatment delivery techniques.
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| 20. |
- Ceberg, Sofie, et al.
(författare)
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Surface guided radiotherapy decreases the uncertainty in breast cancer patient setup
- 2018
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Konferensbidrag (refereegranskat)abstract
- (Sunday, 7/29/2018) 3:00 PM - 6:00 PMRoom: Exhibit HallPurpose: The aim was to investigate if the setup of breast cancer patients could be improved using surface guided radiotherapy, compared to the conventional method using lasers and skin markings.Methods: Forty-seven patients, who received tangential or locoregional adjuvant radiotherapy, were positioned using a surface-based setup (SBS). Thirty-eight patients were positioned using the conventional laser-based setup (LBS). For the patient group positioned using a SBS, correction for posture was performed under guidance of a color map projected onto the patients' skin in real time. The surface tolerance for the color map was 5 mm. For both setup techniques the deviation of the breast position was measured using verification images. In total, 897 images were analysed. The frequency distributions of the deviations were analysed.Results: The result showed a significant improvement in the interfractional variation of the setup deviation for SBS compared to the LBS (pConclusion: Conventional laser-based setup can be replaced by surface-based setup, both for tangential and locoregional breast cancer treatments.
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| 21. |
- Ceberg, Sofie, et al.
(författare)
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Tumor-tracking radiotherapy of moving targets; verification using 3D polymer gel, 2D ion-chamber array and biplanar diode array
- 2010
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Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 250:1, s. 235-239
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to carry out a dosimetric verification of a dynamic multileaf collimator (DMLC)-based tumor-tracking delivery during respiratory-like motion. The advantage of tumor-tracking radiation delivery is the ability to allow a tighter margin around the target by continuously following and adapting the dose delivery to its motion. However, there are geometric and dosimetric uncertainties associated with beam delivery system constraints and output variations, and several investigations have to be accomplished before a clinical integration of this tracking technique. Two types of delivery were investigated in this study I) a single beam perpendicular to a target with a one dimensional motion parallel to the MLC moving direction, and II) an intensity modulated arc delivery (RapidArc®) with a target motion diagonal to the MLC moving direction. The feasibility study (I) was made using an 2D ionisation chamber array and a true 3D polymer gel. The arc delivery (II) was verified using polymer gel and a biplanar diode array. Good agreement in absorbed dose was found between delivery to a static target and to a moving target with DMLC tracking using all three detector systems. However, due to the limited spatial resolution of the 2D array a detailed comparison was not possible. The RapidArc® plan delivery was successfully verified using the biplanar diode array and true 3D polymer gel, and both detector systems could verify that the DMLC-based tumor-tracking delivery system has a very good ability to account for respiratory target motion.
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| 22. |
- Ceberg, Sofie, et al.
(författare)
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Verification of dynamic radiotherapy: the potential for 3D dosimetry under respiratory-like motion using polymer gel.
- 2008
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Ingår i: Physics in Medicine and Biology. - 1361-6560. ; 53:20, s. 387-396
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Tidskriftsartikel (refereegranskat)abstract
- Following the implementation of advanced treatment procedures in radiotherapy, there is a need for dynamic dose verification in 3D. Gel dosimetry could potentially be used for such measurements. However, recently published data show that certain types of gels have a dose rate and fractionation dependence. The aim of this study was to investigate the feasibility of using a polymer gel dosimeter for dose verification of dynamic radiotherapy. To investigate the influence of dose rate dependence during respiratory-like motion in and out of the beam, a respiration robot together with two types of gel systems (normoxic methacrylic acid gel (nMAG) and normoxic polyacrylamide gel (nPAG)) were used. Reference measurements were obtained using a linear diode array (LDA). Expected results, if there was no influence of the dose rate variation, were calculated by convolving the static irradiated gel data with the motion function controlling the robot. To investigate the fractionation dependence, the gels were irradiated using gated and ungated deliveries. Magnetic resonance imaging was used to evaluate the absorbed dose response of the gel. The measured gel data coincided well with the LDA data. Also, the calculated data agreed well with the measured dynamic gel data, i.e. no dose rate dependence due to motion was observed. The difference in the R2 response for the gels receiving ungated and gated, i.e. fractionated, deliveries was less than 1% for the nPAG and 4% for the nMAG, for absorbed doses up to 2 Gy. The maximum difference was 1.2% for the nPAG and 9% for the nMAG, which occurred at the highest given dose (4 Gy). The investigated gels were found to be feasible detectors for dose measurements under respiratory-like motion. For dose verification of dynamic RT involving gated delivery, e.g. breathing-adapted radiotherapy, relative absorbed dose evaluation should be used in order to minimize the effects of fractionated irradiation.
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| 23. |
- Edvardsson, Anneli, et al.
(författare)
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Comparative treatment planning study for mediastinal Hodgkin’s lymphoma : impact on normal tissue dose using deep inspiration breath hold proton and photon therapy
- 2019
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Ingår i: Acta Oncologica. - 0284-186X. ; 58:1, s. 95-104
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Tidskriftsartikel (refereegranskat)abstract
- Background: Late effects induced by radiotherapy (RT) are of great concern for mediastinal Hodgkin’s lymphoma (HL) patients and it is therefore important to reduce normal tissue dose. The aim of this study was to investigate the impact on the normal tissue dose and target coverage, using various combinations of intensity modulated proton therapy (IMPT), volumetric modulated arc therapy (VMAT) and 3-dimensional conformal RT (3D-CRT), planned in both deep inspiration breath hold (DIBH) and free breathing (FB). Material and methods: Eighteen patients were enrolled in this study and planned with involved site RT. Two computed tomography images were acquired for each patient, one during DIBH and one during FB. Six treatment plans were created for each patient; 3D-CRT in FB, 3D-CRT in DIBH, VMAT in FB, VMAT in DIBH, IMPT in FB and IMPT in DIBH. Dosimetric impact on the heart, left anterior descending (LAD) coronary artery, lungs, female breasts, target coverage, and also conformity index and integral dose (ID), was compared between the different treatment techniques. Results: The use of DIBH significantly reduced the lung dose for all three treatment techniques, however, no significant difference in the dose to the female breasts was observed. Regarding the heart and LAD doses, large individual variations were observed. For VMAT, the mean heart and LAD doses were significantly reduced using DIBH, but no significant difference was observed for 3D-CRT and IMPT. Both IMPT and VMAT resulted in improved target coverage and more conform dose distributions compared to 3D-CRT. IMPT generally showed the lowest organs at risk (OAR) doses and significantly reduced the ID compared to both 3D-CRT and VMAT. Conclusions: The majority of patients benefited from treatment in DIBH, however, the impact on the normal tissue dose was highly individual and therefore comparative treatment planning is encouraged. The lowest OAR doses were generally observed for IMPT in combination with DIBH.
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| 24. |
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| 25. |
- Edvardsson, Anneli, et al.
(författare)
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The effect of systematic set-up deviations on the absorbed dose distribution for left-sided breast cancer treated with respiratory gating
- 2013
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Ingår i: 7th International Conference on 3D Radiation Dosimetry (IC3DDose). - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 444, s. 012099-012099
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Konferensbidrag (refereegranskat)abstract
- The aim of this study was 1) to investigate interfraction set-up uncertainties for patients treated with respiratory gating for left-sided breast cancer, 2) to investigate the effect of the inter-fraction set-up on the absorbed dose-distribution for the target and organs at risk (OARs) and 3) optimize the set-up correction strategy. By acquiring multiple set-up images the systematic set-up deviation was evaluated. The effect of the systematic set-up deviation on the absorbed dose distribution was evaluated by 1) simulation in the treatment planning system and 2) measurements with a biplanar diode array. The set-up deviations could be decreased using a no action level correction strategy. Not using the clinically implemented adaptive maximum likelihood factor for the gating patients resulted in better set-up. When the uncorrected set-up deviations were simulated the average mean absorbed dose was increased from 1.38 to 2.21 Gy for the heart, 4.17 to 8.86 Gy to the left anterior descending coronary artery and 5.80 to 7.64 Gy to the left lung. Respiratory gating can induce systematic set-up deviations which would result in increased mean absorbed dose to the OARs if not corrected for and should therefore be corrected for by an appropriate correction strategy.
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| 26. |
- Johansson, Edvin, et al.
(författare)
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Perfusion assessment with bolus differentiation : a technique applicable to hyperpolarized tracers
- 2004
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Ingår i: Magnetic Resonance in Medicine. - : Wiley. - 0740-3194 .- 1522-2594. ; 52:5, s. 51-1043
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Tidskriftsartikel (refereegranskat)abstract
- A new technique for assessing tissue blood flow using hyperpolarized tracers, based on the fact that the magnetization of a hyperpolarized substance can be destroyed permanently, is described. Assessments of blood flow with this technique are inherently insensitive to arterial delay and dispersion, and allow for quantification of the transit time and dispersion in the arteries that supply the investigated tissue. Renal cortical blood flow was studied in six rabbits using a 13C-labeled compound (2-hydroxyethylacrylate) that was polarized by the parahydrogen-induced polarization (PHIP) technique. The renal cortical blood flow was estimated to be 5.7/5.4 +/- 1.6/1.3 ml/min per milliliter of tissue (mean +/- SD, right/left kidney), and the mean transit time and dispersion in the renal arteries were determined to be 1.47/1.42 +/- 0.07/0.07 s and 1.78/1.93 +/- 0.40/0.42 s2, respectively.
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| 27. |
- Jönsson, Mattias, et al.
(författare)
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Technical evaluation of a laser-based optical surface scanning system for prospective and retrospective breathing adapted computed tomography.
- 2015
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Ingår i: Acta Oncologica. - 1651-226X. ; 54:2, s. 261-265
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Tidskriftsartikel (refereegranskat)abstract
- Background. For breathing adapted radiotherapy, the same motion monitoring system can be used for imaging and triggering of the accelerator. Purpose. To evaluate a new technique for prospective gated computed tomography (CT) and four-dimensional CT (4DCT) using a laser based surface scanning system (Sentinel(™), C-RAD, Uppsala, Sweden). The system was compared to the AZ-733V respiratory gating system (Anzai Medical, Tokyo, Japan) and the Real-Time Position Management System (RPM(™)) (Varian Medical Systems, Palo Alto, CA, USA). Material and methods. Temporal accuracy was evaluated using a moving phantom programmed to move a platform along trajectories following a sin(6)(ωt) function with amplitudes from 6 to 20 mm and periods from 2 to 5 s during 120 s while the motion was recorded. The recorded data was Fourier transformed and the peak area at the fundamental and harmonic frequencies compared to data generated using the same sinusoidal function. For verification of the 4DCT reconstruction process, the phantom was programmed to move along a sinusoidal trajectory. Ten phase series were reconstructed. The distance from the couch to the platform was measured in each image. By fitting the function sin(ωt-ϕ) to the values measured in the images corresponding to each slice, the phase of each image was verified. Results and conclusion. In the recorded data, the peak area at the fundamental frequency covered on average 104 ± 4%, 102 ± 4% and 91 ± 27% of the peak area in the generated data for the Sentinel(™), RPM(™) and AZ-733V systems, respectively. All systems managed to resolve both harmonic frequencies. The second experiment showed that all images were sorted into the correct series using breathing data recorded by each system. The systems generated very similar results, however, it is preferable to use the same system both for imaging and treatment.
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| 28. |
- Jönsson, Mattias, et al.
(författare)
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Technical evaluation of different motion-monitoring systems for respiratory gating in radiation therapy
- 2013
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Ingår i: Medical Physics in the Baltic States. - 1822-5721. ; , s. 38-41
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Konferensbidrag (refereegranskat)abstract
- The purpose of this work was to evaluate three motion-monitoring systems: Sentinel (TM), Catalyst (TM) (both C-RAD) and Real-time Position Management (RPM (TM)) system (Varian Medical Systems Inc) for respiratory gating in radiotherapy. To measure the systems. latency, an in-house built circuit with a microcontroller operating a piston was used. The trigger pulse was sent from the gating systems to the accelerator within 300 mu s. However, the response time of the accelerator could be over 300 ms
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| 29. |
- Karlsson, Anna, et al.
(författare)
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Dose integration characteristics in normoxic polymer gel dosimetry investigated using sequential beam irradiation
- 2007
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Ingår i: Physics in Medicine and Biology. - : IOP Publishing. - 1361-6560 .- 0031-9155. ; 52:15, s. 4697-4706
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Tidskriftsartikel (refereegranskat)abstract
- Dose integration properties were investigated for normoxic polymer gels based on methacrylic acid (nMAG) and acrylamide/ N, N'-methylenebisacrylamide (nPAG). The effect of sequential irradiation was studied for different fractionation schemes and varying amounts of methacrylic acid for the nMAG gels. Magnetic resonance imaging (MRI) was used for read out of the absorbed dose response. The investigated gels exhibited a dependence on the fractionation scheme. The response when the total dose was divided into fractions of 0.5 Gy was compared with the response when the total dose was delivered in a single fraction. The slope of the R2 versus the absorbed dose response decreased when the absorbed dose per fraction was increased. Also, for higher amounts of methacrylic acid in the nMAG system the difference in the response increased. For gels containing 2, 4, 6 and 8% methacrylic acid, the R2 versus the absorbed dose response increased by 35, 37, 63 and 93%, respectively. Furthermore, the effect of the fractionation was larger when a higher total absorbed dose was given. The effect was less pronounced for the investigated nPAG, containing 3% acrylamide and 3% N, N'-methylenebisacrylamide, than for the nMAG systems. Consequently, this study indicates that the nPAG system has preferable beam integration characteristics compared with the nMAG system.
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| 30. |
- Kristensson, Elias, et al.
(författare)
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Quantification of the absorbed dose in 3D by means of advanced optical diagnostics based on structured illumination
- 2015
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Ingår i: 8th International Conference on 3D Radiation Dosimetry (IC3DDOSE). - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 573, s. 012010-012010
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Konferensbidrag (refereegranskat)abstract
- The purpose of this study was to present a novel optical diagnostic tool that corrects for undesired contribution of multiply scattered light, thus opening up for e.g. quantitative optical CT measurements of opaque samples. The approach is based on a technique called Structured Illumination (SI), which is commonly employed within microscopic imaging to enhance the depth-resolution. The concept of SI applies for many types of source-detector arrangements and the configuration employed in this paper relies on side-scattering detection. A nPAG polymer gel phantom was irradiated using 6 MV beam. Three-dimensional information was obtained by translating the sample perpendicular to the direction of light, thus sequentially probing different sections. These were then stacked together to form a 3D representation of the sample. By altering the polarization of the laser light during the data acquisition it was discovered that the aggregates responsible for the scattering of light followed Rayleigh scattering, implying that their individual sizes are smaller than, or in the order of, 500 nm.
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| 31. |
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| 32. |
- Kügele, Malin, et al.
(författare)
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Dosimetric effects of intrafractional isocenter variation during deep inspiration breath-hold for breast cancer patients using surface-guided radiotherapy
- 2018
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Ingår i: Journal of Applied Clinical Medical Physics. - : Wiley. - 1526-9914. ; 19:1, s. 25-38
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to investigate potential dose reductions to the heart, left anterior descending coronary artery (LAD), and ipsilateral lung for left-sided breast cancer using visually guided deep inspiration breath-hold (DIBH) with the optical surface scanning system Catalyst™, and how these potential dosimetric benefits are affected by intrafractional motion in between breath holds. For both DIBH and free breathing (FB), treatment plans were created for 20 tangential and 20 locoregional left-sided breast cancer patients. During DIBH treatment, beam-on was triggered by a region of interest on the xiphoid process using a 3 mm gating window. Using a novel nonrigid algorithm, the Catalyst™ system allows for simultaneous real-time tracking of the isocenter position, which was used to calculate the intrafractional DIBH isocenter reproducibility. The 50% and 90% cumulative probabilities and maximum values of the intrafractional DIBH isocenter reproducibility were calculated and to obtain the dosimetric effect isocenter shifts corresponding to these values were performed in the treatment planning system. For both tangential and locoregional treatment, the dose to the heart, LAD and ipsilateral lung was significantly reduced for DIBH compared to FB. The intrafractional DIBH isocenter reproducibility was very good for the majority of the treatment sessions, with median values of approximately 1 mm in all three translational directions. However, for a few treatment sessions, intrafractional DIBH isocenter reproducibility of up to 5 mm was observed, which resulted in large dosimetric effects on the target volume and organs at risk. Hence, it is of importance to set tolerance levels on the intrafractional isocenter motion and not only perform DIBH based on the xiphoid process.
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| 33. |
- Kügele, Malin, et al.
(författare)
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Surface guided radiotherapy (SGRT) improves breast cancer patient setup accuracy
- 2019
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Ingår i: Journal of Applied Clinical Medical Physics. - : Wiley. - 1526-9914. ; , s. 61-68
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: The purpose of the study was to investigate if surface guided radiotherapy (SGRT) can decrease setup deviations for tangential and locoregional breast cancer patients compared to conventional laser-based setup (LBS). Materials and Methods: Both tangential (63 patients) and locoregional (76 patients) breast cancer patients were enrolled in this study. For LBS, the patients were positioned by aligning skin markers to the room lasers. For the surface based setup (SBS), an optical surface scanning system was used for daily setup using both single and three camera systems. To compare the two setup methods, the patient position was evaluated using verification imaging (field images or orthogonal images). Results: For both tangential and locoregional treatments, SBS decreased the setup deviation significantly compared to LBS (P < 0.01). For patients receiving tangential treatment, 95% of the treatment sessions were within the clinical tolerance of ≤ 4 mm in any direction (lateral, longitudinal or vertical) using SBS, compared to 84% for LBS. Corresponding values for patients receiving locoregional treatment were 70% and 54% for SBS and LBS, respectively. No significant difference was observed comparing the setup result using a single camera system or a three camera system. Conclusions: Conventional laser-based setup can with advantage be replaced by surface based setup. Daily SGRT improves patient setup without additional imaging dose to breast cancer patients regardless if a single or three camera system was used.
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| 34. |
- Lempart, Michael, et al.
(författare)
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Development of a novel radiotherapy motion phantom using a stepper motor driver circuit and evaluation using optical surface scanning
- 2017
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Ingår i: Australasian Physical and Engineering Sciences in Medicine. - : Springer Science and Business Media LLC. - 0158-9938 .- 1879-5447. ; 40:3, s. 717-727
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Tidskriftsartikel (refereegranskat)abstract
- Abstract: Recent developments in radiotherapy have focused on the management of patient motion during treatment. Studies have shown that significant gains in treatment quality can be made by ‘gating’ certain treatments, simultaneously keeping target coverage, and increasing separation to nearby organs at risk (OAR). Motion phantoms can be used to simulate patient breathing motion and provide the means to perform quality control (QC) and quality assurance (QA) of gating functionality as well as to assess the dosimetric impact of motion on individual patient treatments. The aim of this study was to design and build a motion phantom that accurately reproduces the breathing motion of patients to enable end-to-end gating system quality control of various gating systems as well as patient specific quality assurance. A motion phantom based on a stepper motor driver circuit was designed. The phantom can be programmed with both real patient data from an external gating system and with custom signals. The phantom was programmed and evaluated with patient data and with a square wave signal to be tracked with a Sentinel™ (C-Rad, Uppsala, Sweden) motion monitoring system. Results were compared to the original curves with respect to amplitude and phase. The comparison of patient curve data showed a mean error value of −0.09 mm with a standard deviation of 0.24 mm and a mean absolute error of 0.29 mm. The square wave signals could be reproduced with a mean error value of −0.03 mm, a standard deviation of 0.04 mm and a mean absolute error of 0.13 mm. Breathing curve data acquired from an optical scanning system can be reproduced accurately with the help of the in-house built motion phantom. The phantom can also be programmed to follow user designed curve data. This offers the potential for QC of gating systems and various dosimetric quality control applications. Graphical Abstract: [Figure not available: see fulltext.]
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| 35. |
- Mannerberg, Annika, et al.
(författare)
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Abdominal compression as motion management for stereotactic radiotherapy of ventricular tachycardia
- 2023
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Ingår i: Physics and imaging in radiation oncology. - 2405-6316. ; 28
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Tidskriftsartikel (refereegranskat)abstract
- Background and purpose: Stereotactic body radiotherapy (SBRT) has emerged as a promising treatment for patients with ventricular tachycardia (VT) who do not respond to standard treatments. However, the management of respiratory motion during treatment remains a challenge. This study aimed to investigate the effect of abdominal compression (AC) on respiratory induced motion in the heart. Materials and methods: A patient cohort of 18 lung cancer patients was utilized, where two four-dimensional computed tomography (4DCT) scans were performed for each patient, one with and one without AC. The patient setup consisted of an AC plate together with a stereotactic body frame. The left coronary artery, the left anterior descending artery, the lateral wall of the left ventricle, the heart apex, the carina, and the right and left diaphragm were delineated in max expiration and max inspiration phases in both 4DCT scans. The center of mass shift from expiration to inspiration phase was determined to assess the AC's impact on respiratory motion. Results: A significant reduction in motion in the superior-inferior direction was found for all heart structures when AC was used. The median respiratory motion of the heart structures decreased by approximately 1–3 mm with AC in the superior-inferior direction, and approximately 60% of the patients had a motion reduction ≥3 mm in the left ventricle wall. Conclusion: These findings suggest that AC has the potential to improve the motion management of SBRT for VT patients, by reducing the respiratory induced motion in the heart.
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| 36. |
- Mannerberg, Annika, et al.
(författare)
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Dosimetric effects of adaptive prostate cancer radiotherapy in an MR-linac workflow
- 2020
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Ingår i: Radiation oncology (London, England). - : Springer Science and Business Media LLC. - 1748-717X. ; 15:1
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The purpose was to evaluate the dosimetric effects in prostate cancer treatment caused by anatomical changes occurring during the time frame of adaptive replanning in a magnetic resonance linear accelerator (MR-linac) workflow. METHODS: Two MR images (MR1 and MR2) were acquired with 30 min apart for each of the 35 patients enrolled in this study. The clinical target volume (CTV) and organs at risk (OARs) were delineated based on MR1. Using a synthetic CT (sCT), ultra-hypofractionated VMAT treatment plans were created for MR1, with three different planning target volume (PTV) margins of 7 mm, 5 mm and 3 mm. The three treatment plans of MR1, were recalculated onto MR2 using its corresponding sCT. The dose distribution of MR2 represented delivered dose to the patient after 30 min of adaptive replanning, omitting motion correction before beam on. MR2 was registered to MR1, using deformable registration. Using the inverse deformation, the structures of MR1 was deformed to fit MR2 and anatomical changes were quantified. For dose distribution comparison the dose distribution of MR2 was warped to the geometry MR1. RESULTS: The mean center of mass vector offset for the CTV was 1.92 mm [0.13 - 9.79 mm]. Bladder volume increase ranged from 12.4 to 133.0% and rectum volume difference varied between -10.9 and 38.8%. Using the conventional 7 mm planning target volume (PTV) margin the dose reduction to the CTV was 1.1%. Corresponding values for 5 mm and 3 mm PTV margin were 2.0% and 4.2% respectively. The dose to the PTV and OARs also decreased from D1 to D2, for all PTV margins evaluated. Statistically significant difference was found for CTV Dmin between D1 and D2 for the 3 mm PTV margin (p < 0.01). CONCLUSIONS: A target underdosage caused by anatomical changes occurring during the reported time frame for adaptive replanning MR-linac workflows was found. Volume changes in both bladder and rectum caused large prostate displacements. This indicates the importance of thorough position verification before treatment delivery and that the workflow needs to speed up before introducing margin reduction.
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| 37. |
- Mannerberg, Annika, et al.
(författare)
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Faster and more accurate patient positioning with surface guided radiotherapy for ultra-hypofractionated prostate cancer patients
- 2021
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Ingår i: Technical Innovations and Patient Support in Radiation Oncology. - : Elsevier BV. - 2405-6324. ; 19, s. 41-45
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: The aim of this study was to evaluate if surface guided radiotherapy (SGRT) can decrease patient positioning time for localized prostate cancer patients compared to the conventional 3-point localization setup method. The patient setup accuracy was also compared between the two setup methods. Materials and methods: A total of 40 localized prostate cancer patients were enrolled in this study, where 20 patients were positioned with surface imaging (SI) and 20 patients were positioned with 3-point localization. The setup time was obtained from the system log files of the linear accelerator and compared between the two methods. The patient setup was verified with daily orthogonal kV images which were matched based on the implanted gold fiducial markers. Resulting setup deviations between planned and online positions were compared between SI and 3-point localization. Results: Median setup time was 2:50 min and 3:28 min for SI and 3-point localization, respectively (p < 0.001). The median vector offset was 4.7 mm (range: 0–10.4 mm) for SI and 5.2 mm for 3-point localization (range: 0.41–17.3 mm) (p = 0.01). Median setup deviation in the individual translations for SI and 3-point localization respectively was: 1.1 mm and 1.9 mm in lateral direction (p = 0.02), 1.8 and 1.6 mm in the longitudinal direction (p = 0.41) and 2.2 mm and 2.6 mm in the vertical direction (p = 0.04). Conclusions: Using SGRT for positioning of prostate cancer patients provided a faster and more accurate patient positioning compared to the conventional 3-point localization setup.
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| 38. |
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| 39. |
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| 40. |
- Pallotta, Stefania, et al.
(författare)
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Validation of a commercial deformable image registration for surface-guided radiotherapy using an ad hoc-developed deformable phantom
- 2020
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Ingår i: Medical Physics. - : Wiley. - 0094-2405 .- 2473-4209. ; 47:12, s. 6310-6318
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: The use of optical surface systems (OSSs) for patient setup verification in external radiation therapy is increasing. To manage potential deformations in a patient’s anatomy, a novel deformable image registration (DIR) tool has been applied in a commercial OSS. In this study we investigate the accuracy of the DIR as compared to rigid image registration (RR). Methods and Materials: The positioning accuracy of the DIR and RR implemented in the OSS was investigated using an ad hoc-developed anthropomorphic deformable phantom, named Mary. The phantom consists of 33 slices of expanded polystyrene slabs shaped thus to simulate part of a female body. Anatomical details, simulating the ribs and spinal cord, together with 10 inner targets at different depths are included in thorax and abdominal parts. Mary is capable of realistic body movements and deformations, such as head and arm rotations, body torsion and moderate breast/abdomen swelling. The accuracy of DIR and RR was investigated for four internal targets after deliberately deforming the phantom nine times. Breast and abdomen enlargements and torsions around x, y, and z axes were applied. For reference purposes, rigid displacements (where Mary’s anatomy was kept intact) were included. The phantom was positioned on the linac couch under the OSS guidance and for each target and displacement a CBCT was acquired. The accuracy of DIR and RR was assessed evaluating the difference in means of absolute values between CBCT and the OSS registration parameters (lateral, longitudinal, vertical, rot, pitch, and roll), using both a reference surface extracted from CT (CTr) or acquired with the OSS (OSSr). A comparison of the four different combinations, DIR + OSSr, DIR + CTr, RR + OSSr, and RR + CTr, was carried out to evaluate the position accuracy for the various combinations. Finally, the positioning accuracy of the different target positions using only OSSr was investigated for the DIR. A paired sample Wilcoxon signed-rank test (P < 0.05) and a two-tailed Mann–Whitney test (P < 0.05) were carried out. Results: The DIR in combination with OSSr showed significantly (P < 0.05) improved positioning accuracy in the lateral and longitudinal directions and in pitch, compared to RR, when deformations were applied to Mary. The positioning accuracy improved from 1.9 ± 1.5 mm, 1.1 ± 0.8 mm to 1.1 ± 1.2 mm, 0.6 ± 0.5 mm in lateral and longitudinal directions, respectively, and from 0.8 ± 0.6° to 0.4 ± 0.4° in pitch, using DIR compared to RR. Both the DIR and RR showed a similar positioning accuracy when rigid displacements of Mary were applied. For DIR, the OSSr generally showed improved calculation accuracy compared to CTr. Independent of the reference image used, the target position influenced the registration accuracy, and hence, one target could not be evaluated using RR due to its inability to calculate the correct position. Conclusions: Improved positioning accuracy was observed for DIR with respect to RR when deformations of Mary’s anatomy were applied. For both DIR and RR, improved positioning accuracy was observed using OSSr as compared to CTr. The position of the target inside the phantom influenced the positioning accuracy for DIR.
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| 41. |
- Persson, Emilia, et al.
(författare)
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Investigation of the clinical inter-observer bias in prostate fiducial marker image registration between CT and MR images
- 2021
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Ingår i: Radiation Oncology. - : Springer Science and Business Media LLC. - 1748-717X. ; 16:1
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Tidskriftsartikel (refereegranskat)abstract
- Background and purpose: Inter-modality image registration between computed tomography (CT) and magnetic resonance (MR) images is associated with systematic uncertainties and the magnitude of these uncertainties is not well documented. The purpose of this study was to investigate the potential uncertainty of gold fiducial marker (GFM) registration for localized prostate cancer and to estimate the inter-observer bias in a clinical setting. Methods: Four experienced observers registered CT and MR images for 42 prostate cancer patients. Manual GFM identification was followed by a landmark-based registration. The absolute difference between observers in GFM identification and the displacement of the clinical target volume (CTV) was investigated. The CTV center of mass (CoM) vector displacements, DICE-index and Hausdorff distances for the observer registrations were compared against a clinical baseline registration. The time allocated for the manual registrations was compared. Results: Absolute difference in GFM identification between observers ranged from 0.0 to 3.0 mm. The maximum CTV CoM displacement from the clinical baseline was 3.1 mm. Displacements larger than or equal to 1 mm, 2 mm and 3 mm were 46%, 18% and 4%, respectively. No statistically significant difference was detected between observers in terms of CTV displacement. Median DICE-index and Hausdorff distance for the CTV, with their respective ranges were 0.94 [0.70–1.00] and 2.5 mm [0.7–8.7]. Conclusions: Registration of CT and MR images using GFMs for localized prostate cancer patients was subject to inter-observer bias on an individual patient level. A CTV displacement as large as 3 mm occurred for individual patients. These results show that GFM registration in a clinical setting is associated with uncertainties, which motivates the removal of inter-modality registrations in the radiotherapy workflow and a transition to an MRI-only workflow for localized prostate cancer.
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| 42. |
- Persson, Emilia, et al.
(författare)
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MR-PROTECT : Clinical feasibility of a prostate MRI-only radiotherapy treatment workflow and investigation of acceptance criteria
- 2020
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Ingår i: Radiation Oncology. - : Springer Science and Business Media LLC. - 1748-717X. ; 15:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: Retrospective studies on MRI-only radiotherapy have been presented. Widespread clinical implementations of MRI-only workflows are however limited by the absence of guidelines. The MR-PROTECT trial presents an MRI-only radiotherapy workflow for prostate cancer using a new single sequence strategy. The workflow incorporated the commercial synthetic CT (sCT) generation software MriPlanner™ (Spectronic Medical, Helsingborg, Sweden). Feasibility of the workflow and limits for acceptance criteria were investigated for the suggested workflow with the aim to facilitate future clinical implementations. Methods: An MRI-only workflow including imaging, post imaging tasks, treatment plan creation, quality assurance and treatment delivery was created with questionnaires. All tasks were performed in a single MR-sequence geometry, eliminating image registrations. Prospective CT-quality assurance (QA) was performed prior treatment comparing the PTV mean dose between sCT and CT dose-distributions. Retrospective analysis of the MRI-only gold fiducial marker (GFM) identification, DVH- analysis, gamma evaluation and patient set-up verification using GFMs and cone beam CT were performed. Results: An MRI-only treatment was delivered to 39 out of 40 patients. The excluded patient was too large for the predefined imaging field-of-view. All tasks could successfully be performed for the treated patients. There was a maximum deviation of 1.2% in PTV mean dose was seen in the prospective CT-QA. Retrospective analysis showed a maximum deviation below 2% in the DVH-analysis after correction for rectal gas and gamma pass-rates above 98%. MRI-only patient set-up deviation was below 2 mm for all but one investigated case and a maximum of 2.2 mm deviation in the GFM-identification compared to CT. Conclusions: The MR-PROTECT trial shows the feasibility of an MRI-only prostate radiotherapy workflow. A major advantage with the presented workflow is the incorporation of a sCT-generation method with multi-vendor capability. The presented single sequence approach are easily adapted by other clinics and the general implementation procedure can be replicated. The dose deviation and the gamma pass-rate acceptance criteria earlier suggested was achievable, and these limits can thereby be confirmed. GFM-identification acceptance criteria are depending on the choice of identification method and slice thickness. Patient positioning strategies needs further investigations to establish acceptance criteria.
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| 43. |
- Svensson, Henrik, et al.
(författare)
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An investigation of a potential multipurpose readout modality for two and three-dimensional dosimetry using optical computed tomography scanners
- 2011
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Ingår i: Medical Physics in the Baltic States. - 1822-5721. ; , s. 39-44
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Konferensbidrag (refereegranskat)abstract
- Radiochromic film, polymer gel and radiochromic plastic are three different kinds of dosimeters developed for radiation therapy and suitable for optical readout. In this study, different optical CT scanners are used to scan the dosimeters to find out if they could be used as multi-purpose scanners, i.e. for readout of the different kinds of dosimeters. Promising results are found but further development needs to be done before any of the scanners could be categorized as multi-purpose scanners.
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| 44. |
- Svensson, H., et al.
(författare)
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Feasibility study using MRI and two optical CT scanners for readout of polymer gel and Presage (TM)
- 2013
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Ingår i: 7th International Conference on 3D Radiation Dosimetry (IC3DDose). - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 444, s. 012079-012079
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Konferensbidrag (refereegranskat)abstract
- The aim of this study was to compare the conventional combination of three-dimensional dosimeter (nPAG gel) and readout method (MRI) with other combinations of three-dimensional dosimeters (nPAG gel/Presage (TM)) and readout methods (optical CT scanners). In the first experiment, the dose readout of a gel irradiated with a four field-box technique was performed with both an Octopus IQ scanner and MRI. It was seen that the MRI readout agreed slightly better to the TPS. In another experiment, a gel and a Presage (TM) sample were irradiated with a VMAT field and read out using MRI and a fast laser scanner, respectively. A comparison between the TPS and the volumes revealed that the MRI/gel readout had closer resemblance to the TPS than the optical CT/Presage (TM) readout. There are clearly potential in the evaluated optical CT scanners, but more time has to be invested in the particular scanning scenario than was possible in this study.
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