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You searched for +publisher:"Delft University of Technology" +contributor:("Goorden, Marlies"). Showing records 1 – 3 of 3 total matches.

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Delft University of Technology

1. Vranas, Georgios (author). Performance evaluation of multipinhole μSPECT systems for short time frames.

Degree: 2017, Delft University of Technology

The need of image (frame) acquisitions within short time intervals is of major importance for preclinical SPECT imaging. The short frame times enable higher temporal resolution which is required in bio-distribution and pharmacokinetic studies where fast dynamic imaging is performed. The present study evaluates and compares the performance of two different preclinical multipinhole SPECT systems (NanoScan, VECTor) for short frames acquisitions. Prior to the systems comparison, the comparison and selection of the best performing fast imaging mode provided by NanoScan system (Mediso) was performed. The fast imaging modes of this system provide acquisitions with 1,2 and 3 detector position around the animal bed. This comparison was performed by using uniform phantoms (syringes) and the rods of the NEMA NU4IQ phantom (frames: 6-30s). The down-sized version of NU4IQ phantom (SPECTIQ phantom) was used in this study to compare the performance of VECTor (MILabs) and NanoScan when performing acquisitions with short frame times (18s-600s, whole body scans). The quality of the acquired images was assessed in terms of absolute quantification (recovery coefficient), noise levels and visual evaluation. The quantification with the NanoScan was accurate (±5%) regardless of times frames duration and activity concentrations when imaging large structures. The increase in number of detector positions yielded images with lower noise levels. In the case of small structures, acquisition with 3 detector positions (Semi-3 mode) appeared to provide more accurate activity recovery compared to acquisitions with 1 (stationary mode) and 2 detector positions (Semi-2 mode). Especially in the case of the 2mm diameter rod of the NU4IQ phantom, the Semi-3 mode appears to provide significantly more accurate activity recovery (30s frame). The systems comparison showed activity recovery with up to 5% deviation from the dose calibrator measurement when imaging the uniform region of SPECTIQ phantom (d = 21mm). Both systems could recover the three largest rods (d = 1.5, 1.0, 0.75mm) for the longest frames used(180,360,600s). None of the systems could recover the two smallest rods of the phantom (d=0.5,0.35mm). As the frame time decreased, both systems could recover less number of rods. VECTor appeared to provide higher activity recovery than NanoScan for the three largest rods of the phantom. However, as the frame time decreased the differences became less significant. Furthermore, VECTor provided and 22.2% and 46.6% less spillover in airand water-filled phantom regions (after reaching convergence) than NanoScan did. The performances of two preclinical SPECT systems (NanoScan, VECTor) for short time acquisitionswere compared. The conducted experiments showed that the systems perform equally when conducting short frames imaging. Furthermore, the fast imaging mode of NanoScan employing three detector positions showed better performance than the other two fast imaging modes provided by this system.

Biomedical Engineering

Advisors/Committee Members: Schaart, Dennis (mentor), Goorden, Marlies (mentor), Delft University of Technology (degree granting institution).

Subjects/Keywords: Preclinical SPECT; performance evaluation; Image Quality; Phantom

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Vranas, G. (. (2017). Performance evaluation of multipinhole μSPECT systems for short time frames. (Masters Thesis). Delft University of Technology. Retrieved from http://resolver.tudelft.nl/uuid:69b604da-2fa9-4a6e-8811-ddd4eb99931f

Chicago Manual of Style (16th Edition):

Vranas, Georgios (author). “Performance evaluation of multipinhole μSPECT systems for short time frames.” 2017. Masters Thesis, Delft University of Technology. Accessed April 12, 2021. http://resolver.tudelft.nl/uuid:69b604da-2fa9-4a6e-8811-ddd4eb99931f.

MLA Handbook (7th Edition):

Vranas, Georgios (author). “Performance evaluation of multipinhole μSPECT systems for short time frames.” 2017. Web. 12 Apr 2021.

Vancouver:

Vranas G(. Performance evaluation of multipinhole μSPECT systems for short time frames. [Internet] [Masters thesis]. Delft University of Technology; 2017. [cited 2021 Apr 12]. Available from: http://resolver.tudelft.nl/uuid:69b604da-2fa9-4a6e-8811-ddd4eb99931f.

Council of Science Editors:

Vranas G(. Performance evaluation of multipinhole μSPECT systems for short time frames. [Masters Thesis]. Delft University of Technology; 2017. Available from: http://resolver.tudelft.nl/uuid:69b604da-2fa9-4a6e-8811-ddd4eb99931f


Delft University of Technology

2. den Boer, Erik (author). Irregular breathing in proton therapy: The effect of irregular breathing on the interplay effect in pencil beam scanning proton therapy.

Degree: 2020, Delft University of Technology

Pencil beam scanning is becoming a more common treatment modality. However, its ability to deal with moving targets is known to be limited, as beam motion and target motion can reinforce each other, deteriorating the planned dose distribution in what is called the interplay effect. Literature concerning breathing motion usually investigates regular patterns. This work aims to investigate the magnitude of the interplay effect when considering irregular breathing signals. In silico calculations of dose distributions were made in the treatment planning system RayStation (version 7.99), using an XCAT phantom with 50 CT phases to model moving patient anatomy. An interplay calculator was included in RayStation, allowing calculation of disturbed doses based on a treatment plan and an irradiation time model for a proton therapy accelerator. The target investigated was a spherical liver tumour with 5cm diameter, irradiated with two beams delivering a prescription dose of 63 Gy. Plans without and with 5x layered repainting were created. Clinically realistic regular breathing patterns were generated to establish a baseline, after which irregularities were introduced. The basic form for all patterns was a sin4 signal, with regular signal amplitudes ranging from 6 to 18 mm, period ranging from 3 to 4 s and phase between 0 and 2π rad. Considered irregularities were baseline shifts up to 34 mm, changing amplitudes between 6 and 18 mm, changing periods between 1.6 and 5.2 s and combinations. Evaluation was done by looking at dose homogeneity HI5 and the fraction of the CTV volume that received a dose outside of the clinical limits of 95% and 107%, V107/95. For the regular patterns, both a systematic and a randomised analysis were carried out. For irregular patterns, only a systematic analysis was carried out. The mean HI5 was found to be 31% for regular patterns; the means of all irregular patterns stay below this, even though the size of the irregularities for some breathing patterns was very large. The mean V107/95 was found to be 0.7 for regular patterns. Irregularities did not cause further deterioration. Five times layered repainting causes a statistically significant decrease in magnitude of the interplay effect across all breathing patterns by 50-80%, but is approximately 50% less effective against baseline shift than against other types of breathing. Interplay effect size correlates strongly with amplitude, but this correlation can be obscured because period and phase introduce very large variance. The interplay effect in general is large for investigated target size, prescription dose, beam configuration and machine performance. It can cause up to 100% of the CTV to receive a clinically unacceptable dose and lead to large inhomogeneities. Irregular breathing was not found to be notably worse. Repainting is effective, even against irregular breathing, but baseline shifts can undermine its effectiveness. Separately considering breathing irregularities for tumours similar to that investigated here is deemed of low… Advisors/Committee Members: Perko, Zoltan (mentor), Goorden, Marlies (graduation committee), Schaart, Dennis (graduation committee), Delft University of Technology (degree granting institution).

Subjects/Keywords: Proton Therapy; Irregular breathing; Pencil beam scanning; Interplay effect

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

den Boer, E. (. (2020). Irregular breathing in proton therapy: The effect of irregular breathing on the interplay effect in pencil beam scanning proton therapy. (Masters Thesis). Delft University of Technology. Retrieved from http://resolver.tudelft.nl/uuid:b3b46f7a-a997-4905-ab77-ad4c54617e9b

Chicago Manual of Style (16th Edition):

den Boer, Erik (author). “Irregular breathing in proton therapy: The effect of irregular breathing on the interplay effect in pencil beam scanning proton therapy.” 2020. Masters Thesis, Delft University of Technology. Accessed April 12, 2021. http://resolver.tudelft.nl/uuid:b3b46f7a-a997-4905-ab77-ad4c54617e9b.

MLA Handbook (7th Edition):

den Boer, Erik (author). “Irregular breathing in proton therapy: The effect of irregular breathing on the interplay effect in pencil beam scanning proton therapy.” 2020. Web. 12 Apr 2021.

Vancouver:

den Boer E(. Irregular breathing in proton therapy: The effect of irregular breathing on the interplay effect in pencil beam scanning proton therapy. [Internet] [Masters thesis]. Delft University of Technology; 2020. [cited 2021 Apr 12]. Available from: http://resolver.tudelft.nl/uuid:b3b46f7a-a997-4905-ab77-ad4c54617e9b.

Council of Science Editors:

den Boer E(. Irregular breathing in proton therapy: The effect of irregular breathing on the interplay effect in pencil beam scanning proton therapy. [Masters Thesis]. Delft University of Technology; 2020. Available from: http://resolver.tudelft.nl/uuid:b3b46f7a-a997-4905-ab77-ad4c54617e9b


Delft University of Technology

3. Bennan, Amit (author). Automated Treatment Planning in HDR Brachytherapy for Prostate Cancer.

Degree: 2017, Delft University of Technology

Introduction: High Dose Rate (HDR) Brachytherapy is a radiotherapy modality that involves temporarily introducing a highly radioactive source into the target volume with the use of an applicator. With respect to HDR brachytherapy for prostate cancer, an 192Iridium source is driven into the target volume through catheters implanted into the prostate. The dose delivered to a point in the prostate depends on the time the source dwells at a given position. Treatment planning for brachytherapy involve the optimization of dwell times and dwell positions. The aim of the treatment plan is to deliver the prescribed dose to the target volume, the prostate, while minimizing the dose to the organs at risk (OAR), namely the urethra, bladder and rectum. In current clinical practice, the process of treatment planning involves the manual manipulation of the parameters of an optimizer until the desired dose distribution is achieved. This implies that the plan quality depends on the experience of the planner, and there is variation in plan quality between planners. The aim of this project was to develop an automated treatment planning system that would able to generate clinically acceptable plans with minimal human intervention. The brachytherapy treatment planning module is named B-iCycle and may be integrated in the future with the treatment planning software suite, called Erasmus-iCycle, developed at the Erasmus MC. Materials and methods: At the core of the treatment planning system (TPS) is a precise and fast dose engine that is able to simulate the dose to be delivered. In this project, we employ the TG-43 dose calculation formalism as it is the most widely implemented method in dose engines for brachytherapy treatment planning systems. The dose engine is then verified against the dose engine of the clinical treatment planning system. B-iCycle uses the 2-phase ϵ-constraint (2pϵc) algorithm to optimize the dwell times and positions. The 2pϵc algorithm requires a ‘wish-list’, which encapsulates the treatment protocol as goals and constraints for each critical structure. For this project three treatment protocols were chosen, four fractions of 9.5 Gy, single fraction of 19 Gy and single fraction of 20 Gy, and wish-lists were generated for each protocol. Three patient groups with different catheter geometries were selected. Treatment plans were generated for each patient and compared against the plans that were generated, for the same patients, in the clinic. The treatment plans that were generated in B-iCycle were then exported to the clinical treatment planning system (Oncentra from Elekta) to obtain the dose characteristics. The plans were compared based on the dose characteristics and the Conformity Index (COIN). The plans were also verified by a radiation oncologist. Results: The TG-43 dose engine was successfully verified against the clinical dose engine. The Gamma analysis showed that only 0.68% of the voxels failed the gamma analysis and these voxels were located within the catheters therefore they can be ignored as… Advisors/Committee Members: Schaart, Dennis (mentor), Breedveld, S. (mentor), Kolkman-Deurloo, I.K.K. (mentor), Heijman, B.J.M. (mentor), Lathouwers, Danny (mentor), Goorden, Marlies (mentor), Delft University of Technology (degree granting institution).

Subjects/Keywords: brachytherapy; Treatment Planning; prostate cancer; HDR

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Bennan, A. (. (2017). Automated Treatment Planning in HDR Brachytherapy for Prostate Cancer. (Masters Thesis). Delft University of Technology. Retrieved from http://resolver.tudelft.nl/uuid:2c0ade14-fc3a-413d-bebc-a6f9ff71fb25

Chicago Manual of Style (16th Edition):

Bennan, Amit (author). “Automated Treatment Planning in HDR Brachytherapy for Prostate Cancer.” 2017. Masters Thesis, Delft University of Technology. Accessed April 12, 2021. http://resolver.tudelft.nl/uuid:2c0ade14-fc3a-413d-bebc-a6f9ff71fb25.

MLA Handbook (7th Edition):

Bennan, Amit (author). “Automated Treatment Planning in HDR Brachytherapy for Prostate Cancer.” 2017. Web. 12 Apr 2021.

Vancouver:

Bennan A(. Automated Treatment Planning in HDR Brachytherapy for Prostate Cancer. [Internet] [Masters thesis]. Delft University of Technology; 2017. [cited 2021 Apr 12]. Available from: http://resolver.tudelft.nl/uuid:2c0ade14-fc3a-413d-bebc-a6f9ff71fb25.

Council of Science Editors:

Bennan A(. Automated Treatment Planning in HDR Brachytherapy for Prostate Cancer. [Masters Thesis]. Delft University of Technology; 2017. Available from: http://resolver.tudelft.nl/uuid:2c0ade14-fc3a-413d-bebc-a6f9ff71fb25

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