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Semiconductor Dosimeters
Published in Arash Darafsheh, Radiation Therapy Dosimetry: A Practical Handbook, 2021
Giordano Biasi, Nicholas Hardcastle, Anatoly B. Rosenfeld
A further application of MOSFETs to in vivo dosimetry uses a MOSFET implanted inside the planning treatment volume (PTV). Commercial implantable wireless MOSFETs (DVS® dose verification system, Sicel Technologies, Morrisville, NC) were investigated by several groups [135–143]. Implanted MOSFETs can be imaged and located with ultrasonography [140, 142], kilovoltage [138–140, 142] or megavoltage [144] computerized tomography (CT) scans. Also, they can be used as fiducial markers in image-guided radiotherapy (IGRT); a feasibility study on their use for extracranial-target treatments delivered with the CyberKnife system was also reported [107].
Precision and Uncertainties in Planning and Delivery *
Published in Harald Paganetti, Proton Therapy Physics, 2018
Daniel K. Yeung, Jatinder R. Palta
Implanted fiducials have been used in various clinical sites to improve target localization in image-guided radiation therapy. Most commercially available fiducial markers are made of high-Z materials that cause artifacts in CT scans and can significantly perturb dose because of the steep dose gradient in particle beams, especially for IMPT [61–64]. Fiducial markers should, therefore, possess the following desirable features: visibility in the required imaging modality (CT, MRI, X-ray), absence of (or with minimal) artifacts, low perturbation of the target dose, and stability after insertion. A thorough study by Habermehl et al. [65] included Visicoils (IBA (Ion Beam Applications, Louvain-La-Neuve, Belgium): gold coils with diameters 1.1, 0.75, 0.5, and 0.35 mm), Gold Anchor (Naslund Medical AB, gold, 0.27 mm diameter), Beammarks (Beampoint AB: nitinol, 1.2 mm diameter), and BiomarC (Carbon Medical Technologies: Zirconium oxide covered with pyrolytic carbon, 1 mm diameter). All markers demonstrated good visibility. Carbon-coated thin gold markers produced the least artifacts and minor dose perturbation. Gold markers >0.5 mm are not recommended, except for use laterally or distally to the treatment field. For markers with high-Z material and thickness greater than 0.5 mm, the water-equivalent path length and dosimetric impact of the markers should be carefully evaluated.
Sensor-Enabled 3D Printed Tissue-Mimicking Phantoms: Application in Pre-Procedural Planning for Transcatheter Aortic Valve Replacement
Published in Ayman El-Baz, Jasjit S. Suri, Cardiovascular Imaging and Image Analysis, 2018
Kan Wang, Chuck Zhang, Ben Wang, Mani A Vannan, Zhen Qian
Latex rubber is another popular material for vascular phantoms. Zhang and Greenleaf fabricated a femoral artery phantom using latex rubber tubing and mounted tubing within a gelatin filled frame to mimic the adjacent soft tissue [20]. Kawase et al. used a rubber ring with wires attached to the outer surface to provide fiducial markers [21].
The Swedish national guidelines on prostate cancer, part 1: early detection, diagnostics, staging, patient support and primary management of non-metastatic disease
Published in Scandinavian Journal of Urology, 2022
Ola Bratt, Stefan Carlsson, Per Fransson, Camilla Thellenberg Karlsson, Johan Stranne, Jon Kindblom
MRI-based dose-planning with the use of fiducial markers for image-guided RT (IGRT) with volumetric arc radiation treatment (VMAT) or intensity-modulated radiation treatment (IMRT) techniques are recommended as standard of care. Using a pre-rectal hydrogel spacer should be considered in patients with an increased risk of significant rectal toxicity [36]. Recommended doses for EBRT with curative intent are either 78 Gray in 39 fractions (conventional fractionation), 66 Gray in 20 fractions (moderate hypofractionation) as in the CHHIP trial [37] or, since 2020, ultra-hypofractionated radiotherapy with 42.7 Gray in 7 fractions. The ultra-hypofractionated was shown to be equally effective as the standard radiotherapy in the Nordic HYPO-RT-PC trial [38]. Most Swedish radiotherapy centres participated in this trial and are therefore highly experienced in planning and delivering ultra-hypofractionated radiotherapy. Not least patients living far away from a radiation centre appreciate avoiding the otherwise long radiation treatment course. Ultra-hypofractionation is the radiation treatment of choice for men with intermediate-risk and is considered a valid option for some, selected men with favourable localised high-risk cancer. This contrasts with the European guidelines, which still recommend ultra-hypofractionated radiotherapy in prospective clinical trials only [2].
Smartphone-based computer vision travelling aids for blind and visually impaired individuals: A systematic review
Published in Assistive Technology, 2022
Andrius Budrionis, Darius Plikynas, Povilas Daniušis, Audrius Indrulionis
Navigation indoors is a well-known use case where traditional navigation systems based on GPS sensors fail. Five papers selected an indoor scenario as the main focus and addressed the challenges using various approaches. To estimate position and direction of movement, computer vision functionality was supplemented by data from motion sensors (Ko, 2013; Ko & Kim, 2017; Rituerto et al., 2016). Such sensors were sufficient to track the location of a VI user within a static map of a building, while providing guidance toward the goal. However, motion sensors have their limitations – they require maps and continuous tracking of movements to localize the user. The use of fiducial markers to improve localization was proposed in three papers (two of which originated from the same project). Locations of interest were QR coded (Ko, 2013; Ko & Kim, 2017), simplifying the computer vision and localization tasks to the recognition of the QR codes. Pure computer vision solutions for indoor environments were discussed in two publications, demonstrating the feasibility of such systems (Elloumi et al., 2013; Garcia & Nahapetian, 2015).
A comprehensive motion analysis – consequences for high precision image-guided radiotherapy of esophageal cancer patients
Published in Acta Oncologica, 2021
Catharina T. G. Roos, Zohra Faiz, Sabine Visser, Margriet Dieters, Hans Paul van der Laan, Lydia A. den Otter, John T. M. Plukker, Johannes A. Langendijk, Antje-Christin Knopf, Christina T. Muijs, Nanna M. Sijtsema
Daily changes in diaphragm and consequently in tumor position may result in clinically relevant dose deviations. The target can be partially missed when large off-sets occur, especially if patient position verification is based on bony anatomy. Bone matching is common clinical practice for CBCT-pCT registration in most institutes. The use of fiducial markers at the tumor borders would improve the visibility of the target, and consequently the quality of position verification using CBCTs [12,17]. However, Jin et al. [23] recommended against using marker-based position corrections due to the large tissue deformations that can occur in the distal esophagus. Instead they suggest position corrections based on bony anatomy, and using the markers to check that the tumor is still inside the projected PTV.