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Radiation oncology considerations
Published in Charles F. Levenback, Ate G.J. van der Zee, Robert L. Coleman, Clinical Lymphatic Mapping in Gynecologic Cancers, 2022
Gwendolyn Joyce McGinnis, Anuja Jhingran
An essential element of high-quality radiation treatment is accurate patient positioning and treatment delivery. A number of factors introduce uncertainty in this process, including imprecise patient positioning, inherent organ motion, and technical variation. In order to compensate for this uncertainty inherent in the patient setup and treatment process, radiation oncologists use an additional margin when designing target volumes in excess of the volumes of clinical interest. However, the use of real-time image guidance can allow for the use of smaller margins, as the treating radiation oncologist can be certain of the position of the treatment target and organs at risk at the time of treatment. Image guidance may include x-rays aligning to bone or cone beam computed tomography (CT) scans aligning to soft tissue, or even just looking at positions of target organs or a combination of both.
Equipment for Patient Data Acquisition
Published in W. P. M. Mayles, A. E. Nahum, J.-C. Rosenwald, Handbook of Radiotherapy Physics, 2021
The direct use of digital flat panels eliminates the need for extra detectors. Provided that the panel area is large enough, a 3D image of the body can be acquired with a single 360° rotation.* This approach has been named cone-beam computerised tomography (CBCT). CBCT has been developed concurrently for patient data acquisition with a simulator and for 3D verification of the patient position in the treatment room (for IGRT) (Jaffray et al. 2002). This second option is discussed in Sections 13.3.2 and 13.3.3.
Clinical Commissioning Guidelines
Published in Jinzhong Yang, Gregory C. Sharp, Mark J. Gooding, Auto-Segmentation for Radiation Oncology, 2021
More importantly, the large geometric uncertainties resulting from manual segmentation constrain the dose that can be safely delivered to target tumors. This is because of the large field treatment margins [18] necessary to account for the geometric uncertainties, which invariably lead to higher doses delivered to the nearby normal OARs. In-treatment-room X-ray-based cone beam computed tomography (CBCT) imaging is currently available as part of standard equipment. CBCT has been used for positional and setup corrections during treatments. Incorporating geometric corrections has been shown to lead to improved accuracy of the conformal treatment [4, 19], and with it the potential for improving outcomes. However, a key obstacle for these treatments is a lack of robust, fast, and accurate segmentation methods. Atlas-based methods are computationally expensive and are impacted by changing anatomy; anatomical changes are common during radiation therapy and imaging appearance may change, reducing the accuracy of atlas-based deformation techniques.
Image-guided radiotherapy (IGRT) in Lombardy, Italy: a survey by the Lombardy section of the Italian Association of Radiotherapy and Clinical Oncology (AIRO-Lombardy)
Published in Expert Review of Anticancer Therapy, 2023
Sara Pedretti, Maria Carmen De Santis, Vittorio Vavassori, Barbara Bortolato, Riccardo Ray Colciago, Emanuela Cagna, Daniela Patrizia Doino, Alessandra Cocchi, Marianna Alessandra Gerardi, Daniela Alterio, Stefano Maria Magrini, Sandro Tonoli
Image-guided radiation therapy (IGRT) is the acquisition and evaluation of target images before, during, or after a course of radiation therapy (RT) with the goal to achieve high-precision treatments [1]. In 2008, Verellen [2] authored a review concluding that technological developments coupled with better knowledge of functional and morphologic information have renewed the interest in IGRT. Over the decades, devices evolved from planar X-ray imaging to cone beam-computed tomography (CBCT). The most recent form of IGRT is represented by MRI-based linear accelerators (LINAC), not yet in routine use in Lombardy, but clinically and routinely used by many centers outside Lombardy. CBCT is the most widely used system for IGRT [3]. The multiplanar reconstruction of images permits to identify the target volume/organs at risk and correct eventual anatomical and physiological differences from the baseline images. Thus, inter-fraction alterations will be corrected and IGRT enables full target coverage and the best normal tissue sparing, improving outcomes in terms of safety and efficacy [4]. Additionally, IGRT lays the foundation for adaptive RT: modification of the delivery plan to better manage all variations occurring during the radiotherapy course [5,6].
Patient-specific pre-operative simulation of the surgically assisted rapid maxillary expansion using finite element method and Latin hypercube sampling: workflow and first clinical results
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2023
L. Bonitz, A. Volf, S. Hassfeld, A. Pugachev, B. Ludwig, S. Chhatwani, A. Bicsák
The planning was performed on preoperative CT scans, and the follow-up was based on cone-beam computed tomography (CBCT) scans taken 4 months postoperatively. The volumetric data were segmented using ScanIP and transformed into the same coordinate system for superimposition. Using the CloudCompare V2.1.1. for superimposition, three bone areas were manually stacked, the zygomatic arch on both sides, the great foramen, and the sella turcica. For the best fit, fine-tuning was subsequently performed using the iterative closest point (ICP) registration algorithm. A median plane in the midline orthogonal to the Frankfort horizontal plane was constructed. For further analysis, we used only the vestibular surface shells from the dentoalveolar and maxillary bone formation by removing the other surfaces using the ANSYS SpaceClaim V19.2. Finally, we compared the spatial differences of the surface shell using a heatmap diagram and extracted from the deviation histogram the minimal and maximal distances from each side with the calculation of the modal values.
Yttrium-90 for colorectal liver metastasis - the promising role of radiation segmentectomy as an alternative local cure
Published in International Journal of Hyperthermia, 2022
Pouya Entezari, Ahmed Gabr, Riad Salem, Robert J. Lewandowski
Although promising outcomes of radiation segmentectomy in treatment of early-stage HCC are now established [42,45–47,51,52], available data on efficacy of such treatment in patients with CRLM is limited, with this concept now being explored for patients with oligometastatic disease. (Figure 2) There are challenges in utilizing Y90 radioembolization in the treatment of CRLM patients. Since most of these patients have been heavily pretreated with multiple chemotherapeutic regimens, their hepatic vasculature flow can be profoundly altered [53]. This can limit the ability to perform super-selective catheterization required for this approach. Further, CRLMs are often hypovascular, making tumor targeting more challenging. This can mostly be overcome with the application of intra-procedure cone-beam computed tomography (CT).