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Dosimeters and Devices for IMRT QA
Published in Arash Darafsheh, Radiation Therapy Dosimetry: A Practical Handbook, 2021
Nesrin Dogan, Matthew T. Studenski, Perry B. Johnson
The daily QA should be quick and efficient. Typically, a detector array containing ion chamber and diodes is used to measure the output, energy, flatness, symmetry, and field size simultaneously. SunNuclear DailyQA3, PTW QuickCheck, and IBA StarTrack are examples of such devices. A separate imaging phantom is used for the imaging tests where an image is taken and compared to a DRR or CT image to assess isocenter coincidence. The QUASAR PentaGuide is an example of such a phantom.
Imaging of Cardiovascular Disease
Published in George C. Kagadis, Nancy L. Ford, Dimitrios N. Karnabatidis, George K. Loudos, Handbook of Small Animal Imaging, 2018
Aleksandra Kalinowska, Lawrence W. Dobrucki
As a whole, however, no imaging modality is ideal. Magnetic resonance studies provide unparalleled versatility and soft tissue contrast but are not highly sensitive, which makes injections of relatively large amounts of nanoparticles (2–20 mg Fe/kg) necessary for sufficient signal enhancement. Lower concentrations of nanoparticles can be used by nuclear techniques, such as PET, which are incomparably more sensitive. In a recent study, the detection threshold of a nanoparticle in an imaging phantom was ≈5 µg Fe/mL using T2-weighted MRI and 0.1 µg Fe/mL for PET–CT imaging (Nahrendorf et al. 2008b). Although the nanoparticle dose is reduced in nuclear imaging, PET in turn does not offer high spatial resolution. Currently, the application of hybrid systems shows the greatest potential, which combine the high sensitivity of PET with the anatomic detail provided by CT or MRI. To enhance sensitivity, USPIO nanoparticles have been introduced. By attaching optical or nuclear reporters to the magnetic agents, the application of hybrid molecular techniques is made possible.
Quality assurance of IGRT
Published in Jing Cai, Joe Y. Chang, Fang-Fang Yin, Principles and Practice of Image-Guided Radiation Therapy of Lung Cancer, 2017
Krishni Wijesooriya, Taeho Kim, Josh Evans, Quan Chen
Alternative methods can also be used for the geometric accuracy verification. One approach is to first establish the agreement between the room laser system and the treatment isocenter, then by imaging phantom with markers align to the laser, the agreement between the imaging isocenter and treatment isocenter can be inferred [45]. This alternative method is more applicable to the MRIdian system because the MRI system is not capable of finding the treatment isocenter. In addition, end-to-end tests that include imaging, registration, reposition, and treatment have also been recommended as a test for the geometric accuracy [18,22,46].
Assessment of quantitative magnetic resonance imaging metrics in the brain through the use of a novel phantom
Published in Brain Injury, 2018
Elisabeth A. Wilde, James M. Provenzale, Brian A. Taylor, Michael Boss, Anthony Zuccolotto, Rebecca Hachey, Sudhir Pathak, David F. Tate, Tracy J. Abildskov, Walter Schneider
The use of phantoms in MRI-based experiments has a long history. Phantoms have been used in imaging experiments to provide a ground truth (or ‘gold standard’) for various mathematical imaging models (11–15) to evaluate, analyse, and test the performance of imaging systems (16–20), and to evaluate and calibrate multimodal MR signals from various MR pulse sequences. They are also used to test scanner performance and to validate MR-derived metrics at many imaging centres (21). A formal testing mechanism and validation framework for reproducibility and reliability of MR metrics (22,23) is provided by Quantitative Imaging Biomarkers Alliance and American College of Radiology. The goal of any imaging phantom in the field of MR is to provide reproducible quantitative results from imaging methods for multivendor, multisite and test–retest assessments (24–26). Finally, physical and digital reference objects may play a role in evaluating and optimizing imaging protocols and in creating reproducible analysis pipelines.
Tactics: an open-source platform for planning, simulating and validating stereotactic surgery
Published in Computer Assisted Surgery, 2020
David S. P. Adair, Keith S. Gomes, Zelma H. T. Kiss, David G. Gobbi, Yves P. Starreveld
We tested the software in three distinct stages to determine its usability and accuracy. Initial tests consisted of planning biopsies with Tactics in parallel with standard clinical tools, providing qualitative evidence that Tactics is an intuitive, efficient, and effective tool that improves on standard techniques. To measure the accuracy of the application, experts targeted fiducial markers within an imaging phantom using both Tactics and the physical stereotactic frame and compared the results. These tests demonstrated accuracy of the software within the resolution of the stereotactic frame itself, validating that the software produces accurate target coordinates.
Evaluation of an MRI receive head coil for use in transcranial MR guided focused ultrasound for functional neurosurgery
Published in International Journal of Hyperthermia, 2021
Rachel Rinat Bitton, Evgeni Sheingaouz, Benny Assif, Nathaniel Kelm, Mor Dayan, Kim Butts Pauly, Pejman Ghanouni
Using a large spherical imaging phantom (16.8 cm diameter), sensitivity maps were constructed to determine receive-only coil performance and uniformity. For receive sensitivity maps only, B1 mapping was used to correct the transmit field due to the presence of the transducer. The head coil was then tested in two main areas: 1) image quality relevant to in-treatment planning and 2) image quality relevant to treatment monitoring through MR thermometry performance.