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Title: SU-E-I-60: Quality Assurance Testing Methods and Customized Phantom for Magnetic Resonance Imaging and Spectroscopy

Abstract

Purpose: The objectives of this study are to develop an magnetic resonance imaging and spectroscopy (MRI-MRS) fused phantom along with the inserts for metabolite quantification and to conduct quantitative analysis and evaluation of the layered vials of brain-mimicking solution for quality assurance (QA) performance, according to the localization sequence. Methods: The outer cylindrical phantom body is made of acrylic materials. The section other than where the inner vials are located was filled with copper sulfate and diluted with water so as to reduce the T1 relaxation time. Sodium chloride was included to provide conductivity similar to the human body. All measurements of MRI and MRS were made using a 3.0 T scanner (Achiva Tx 3.0 T; Philips Medical Systems, Netherlands). The MRI scan parameters were as follows: (1) spin echo (SE) T1-weighted image: repetition time (TR), 500ms; echo time (TE), 20ms; matrix, 256×256; field of view (FOV), 250mm; gap, 1mm; number of signal averages (NSA), 1; (2) SE T2-weighted image: TR, 2,500 ms; TE, 80 ms; matrix, 256×256; FOV, 250mm; gap, 1mm; NSA, 1; 23 slice images were obtained with slice thickness of 5mm. The water signal of each volume of interest was suppressed by variable pulse power and optimizedmore » relaxation delays (VAPOR) applied before the scan. By applying a point-resolved spectroscopy sequence, the MRS scan parameters were as follows: voxel size, 0.8×0.8×0.8 cm{sup 3}; TR, 2,000ms; TE, 35ms; NSA, 128. Results: Using the fused phantom, the results of measuring MRI factors were: geometric distortion, <2% and ±2 mm; image intensity uniformity, 83.09±1.33%; percent-signal ghosting, 0.025±0.004; low-contrast object detectability, 27.85±0.80. In addition, the signal-to-noise ratio of N-acetyl-aspartate was consistently high (42.00±5.66). Conclusion: The MRI-MRS QA factors obtained simultaneously using the phantom can facilitate evaluation of both images and spectra, and provide guidelines for obtaining MRI and MRS QA factors simultaneously. This study was supported by grant (2012-007883 and 2014R1A2A1A10050270) from the Mid-career Researcher Program through the NRF funded by Ministry of Science. In addition, this study was supported by the Industrial R&D of MOTIE/KEIT (10048997, Development of the core technology for integrated therapy devices based on real-time MRI-guided tumor tracking)« less

Authors:
; ;  [1]
  1. Department of Biomedical Engineering, Research Institute of Biomedical Engineering, College of Medicine, The Catholic University of Korea, Seoul, Seoul (Korea, Republic of)
Publication Date:
OSTI Identifier:
22494012
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 42; Journal Issue: 6; Other Information: (c) 2015 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; IMAGES; NMR IMAGING; PHANTOMS; QUALITY ASSURANCE; RADIOTHERAPY; RELAXATION TIME; SIGNAL-TO-NOISE RATIO; SPECTROSCOPY

Citation Formats

Song, K-H, Lee, D-W, and Choe, B-Y. SU-E-I-60: Quality Assurance Testing Methods and Customized Phantom for Magnetic Resonance Imaging and Spectroscopy. United States: N. p., 2015. Web. doi:10.1118/1.4924057.
Song, K-H, Lee, D-W, & Choe, B-Y. SU-E-I-60: Quality Assurance Testing Methods and Customized Phantom for Magnetic Resonance Imaging and Spectroscopy. United States. doi:10.1118/1.4924057.
Song, K-H, Lee, D-W, and Choe, B-Y. Mon . "SU-E-I-60: Quality Assurance Testing Methods and Customized Phantom for Magnetic Resonance Imaging and Spectroscopy". United States. doi:10.1118/1.4924057.
@article{osti_22494012,
title = {SU-E-I-60: Quality Assurance Testing Methods and Customized Phantom for Magnetic Resonance Imaging and Spectroscopy},
author = {Song, K-H and Lee, D-W and Choe, B-Y},
abstractNote = {Purpose: The objectives of this study are to develop an magnetic resonance imaging and spectroscopy (MRI-MRS) fused phantom along with the inserts for metabolite quantification and to conduct quantitative analysis and evaluation of the layered vials of brain-mimicking solution for quality assurance (QA) performance, according to the localization sequence. Methods: The outer cylindrical phantom body is made of acrylic materials. The section other than where the inner vials are located was filled with copper sulfate and diluted with water so as to reduce the T1 relaxation time. Sodium chloride was included to provide conductivity similar to the human body. All measurements of MRI and MRS were made using a 3.0 T scanner (Achiva Tx 3.0 T; Philips Medical Systems, Netherlands). The MRI scan parameters were as follows: (1) spin echo (SE) T1-weighted image: repetition time (TR), 500ms; echo time (TE), 20ms; matrix, 256×256; field of view (FOV), 250mm; gap, 1mm; number of signal averages (NSA), 1; (2) SE T2-weighted image: TR, 2,500 ms; TE, 80 ms; matrix, 256×256; FOV, 250mm; gap, 1mm; NSA, 1; 23 slice images were obtained with slice thickness of 5mm. The water signal of each volume of interest was suppressed by variable pulse power and optimized relaxation delays (VAPOR) applied before the scan. By applying a point-resolved spectroscopy sequence, the MRS scan parameters were as follows: voxel size, 0.8×0.8×0.8 cm{sup 3}; TR, 2,000ms; TE, 35ms; NSA, 128. Results: Using the fused phantom, the results of measuring MRI factors were: geometric distortion, <2% and ±2 mm; image intensity uniformity, 83.09±1.33%; percent-signal ghosting, 0.025±0.004; low-contrast object detectability, 27.85±0.80. In addition, the signal-to-noise ratio of N-acetyl-aspartate was consistently high (42.00±5.66). Conclusion: The MRI-MRS QA factors obtained simultaneously using the phantom can facilitate evaluation of both images and spectra, and provide guidelines for obtaining MRI and MRS QA factors simultaneously. This study was supported by grant (2012-007883 and 2014R1A2A1A10050270) from the Mid-career Researcher Program through the NRF funded by Ministry of Science. In addition, this study was supported by the Industrial R&D of MOTIE/KEIT (10048997, Development of the core technology for integrated therapy devices based on real-time MRI-guided tumor tracking)},
doi = {10.1118/1.4924057},
journal = {Medical Physics},
number = 6,
volume = 42,
place = {United States},
year = {Mon Jun 15 00:00:00 EDT 2015},
month = {Mon Jun 15 00:00:00 EDT 2015}
}
  • Purpose: To test the sensitivity of the quality assurance (QA) tools actively used on a clinical MR-IGRT system for potential delivery errors. Methods: Patient-specific QA procedures have been implemented for a commercially available Cobalt-60 MR-IGRT system. The QA tools utilized were a MR-compatible cylindrical diode-array detector (ArcCHECK) with a custom insert which positions an ionization chamber (Exradin A18) in the middle of the device, as well as an in-house treatment delivery verification program. These tools were tested to investigate their sensitivity to delivery errors. For the ArcCHECK and ion chamber, a baseline was established with a static field irradiation tomore » a known dose. Variations of the baseline were investigated which included rotated gantry, altered field size, directional shifts, and different delivery time. In addition, similar variations were tested with the automated delivery verification program that compared the treatment parameters in the machine delivery logs to the ones in the plan. To test the software, a 3-field conformal plan was generated as the baseline. Results: ArcCHECK noted at least a 13% decrease in passing rate from baseline in the following scenarios: gantry rotation of 1 degree from plan, 5mm change in field size, 2mm lateral shift, and delivery time decrease. Ion chamber measurements remained consistent for these variations except for the 5 second decrease in delivery time scenario which resulted in an 8% difference from baseline. The delivery verification software was able to detect and report the simulated errors such as when the gantry was rotated by 0.6 degrees, the beam weighting was changed by a percent, a single multileaf collimator was moved by 1cm, and the dose was changed from 2 to 1.8Gy. Conclusion: The results show that the current tools used for patient specific QA are capable of detecting small errors in RT delivery with presence of magnetic field.« less
  • Purpose: Due to the effect of the magnetic field on the dose deposition (skewing the beam), machine quality assurance (QA) tests for the MR-linac (MRI combined with a linear accelerator) need to be redesigned. In this work we focus on the redesign of QA tests that address geometrical accuracy of the system. Methods: Using electron dense materials (e.g. copper in our experiment) the dose kernel is minimized and thereby the effect of the magnetic field on the dose distribution. This approach is supported by Monte-Carlo simulations and can be used in practice with film measurements. Two examples of QA testsmore » are presented: beam profile and star-shot measurements. Results: The novel method was verified by performing both measurements on a conventional linac and the MR-linac with a film that was sandwiched between copper layers. Measurements were compared with a reference setup which was similar to setup used in clinical practice. On a conventional linac the experimental outcome showed good agreement between the reference and the new setup for both QA tests. The results from the MR-linac showed that the symmetry of the beam profile was restored in presence of the copper layers in the setup and that the isocenter size can be determined accurately with the introduced star-shot setup (see supporting material). Conclusion: The use of electron dense materials for QA tests was shown to be a simple and effective method to remove the effects on the dose distribution enabling assessment of geometrical accuracy of a MR-linac system. The use of high dense materials is not limited to the presented QA tests only, but has a broad applicability for beam specific QA tests in presence of a magnetic field.« less
  • Purpose: Use of Small Animal Radiation Research Platform (SARRP) systems for conducting state-of-the-art image guided radiotherapy (IGRT) research on small animals has become more common over the past years. The purpose of this work is to develop and test the suitability and performance of a comprehensive quality assurance (QA) phantom for the SARRP. Methods: A QA phantom was developed for carrying out daily, monthly and annual QA tasks including imaging, dosimetry and treatment planning system (TPS) performance evaluation of the SARRP. The QA phantom consists of nine (60×60×5 mm3) KV-energy tissue equivalent solid water slabs that can be employed formore » annual dosimetry QA with film. Three of the top slabs are replaceable with ones incorporating Mosfets or OSLDs arranged in a quincunx pattern, or a slab drilled to accommodate an ion chamber insert. These top slabs are designed to facilitate routine daily and monthly QA tasks such as output constancy, isocenter congruency test, treatment planning system (TPS) QA, etc. One slab is designed with inserts for image QA. A prototype of the phantom was applied to test the performance of the imaging, planning and treatment delivery systems. Results: Output constancy test results showed daily variations within 3%. For isocenter congruency test, the phantom could be used to detect 0.3 mm deviations of the CBCT isocenter from the radiation isocenter. Using the Mosfet in phantom as target, the difference between TPS calculations and measurements was within 5%. Image-quality parameters could also be assessed in terms of geometric accuracy, CT number accuracy, linearity, noise and image uniformity, etc. Conclusion: The developed phantom can be employed as a simple tool for comprehensive performance evaluation of the SARRP. The study provides a reference for development of a comprehensive quality assurance program for the SARRP, with proposed tolerances and frequency of required tests.« less
  • Purpose: To perform a routine quality assurance procedure for Truebeam multi-leaf collimator (MLC) using MLC QA phantom, verify the stability and reliability of MLC during the treatment. Methods: MLC QA phantom is a specialized phantom for MLC quality assurance (QA), and contains five radio-opaque spheres that are embedded in an “L” shape. The phantom was placed isocentrically on the Truebeam treatment couch for the tests. A quality assurance plan was setted up in the Eclipse v10.0, the fields that need to be delivered in order to acquire the necessary images, the MLC shapes can then be obtained by the images.more » The images acquired by the electronic portal imaging device (EPID), and imported into the PIPSpro software for the analysis. The tests were delivered twelve weeks (once a week) to verify consistency of the delivery, and the images are acquired in the same manner each time. Results: For the Leaf position test, the average position error was 0.23mm±0.02mm (range: 0.18mm∼0.25mm). The Leaf width was measured at the isocenter, the average error was 0.06mm±0.02mm (range: 0.02mm∼0.08mm) for the Leaf width test. Multi-Port test showed the dynamic leaf shift error, the average error was 0.28mm±0.03mm (range: 0.2mm∼0.35mm). For the leaf transmission test, the average inter-leaf leakage value was 1.0%±0.17% (range: 0.8%∼1.3%) and the average inter-bank leakage value was 32.6%±2.1% (range: 30.2%∼36.1%). Conclusion: By the test of 12 weeks, the MLC system of the Truebeam is running in a good condition and the MLC system can be steadily and reliably carried out during the treatment. The MLC QA phantom is a useful test tool for the MLC QA.« less
  • Purpose: To test the accuracy and reproducibility of both translational and rotational movements for a couch with six degrees of freedom (6DoF) using a novel phantom design Methods: An end-to-end test was carried out using two different phantoms. A 6 cm3 cube with a central fiducial BB (WL-QA Sun Nuclear) and a custom fabricated rectangular prism (31 cm x 8 cm x 8 cm), placed on a baseplate with known angular offsets for pitch, roll and yaw with a central fiducial BB and unique surface structures for registration purposes, were used. The end-to-end test included an initial CT simulation formore » a reference study, setup to an offset mark on each phantom, registration of the reference CT to the acquired cone-beam CT, and final Winston-Lutz delivery at four cardinal gantry angles. Results for both translational and rotational movements were recorded and compared for both phantoms. Results: Translational and rotational measurements were performed with a PerfectPitch (Varian) couch for 10 trials for both phantoms. Distinct translational shifts were [−5.372±0.384mm, −10.183±0.137mm, 14.028±0.155mm] for the cube and [7.520±0.159mm, −9.117±0.101mm, 16.273±0.115mm] for the prototype phantom for lateral, longitudinal, and vertical shifts, respectively. Distinct rotational adjustments were [1.121±0.102o, −1.067±0.235o, −2.662±0.380o] for the cube and [2.534±0.059o, 1.994±0.025o, 2.094±0.076o] for the prototype for pitch, roll, and yaw, respectively. Winston-Lutz test results performed after 6DoF couch correction from each cardinal gantry angle ranged from 0.26–0.72mm for the cube and 0.55–0.86mm for the prototype. Conclusion: The prototype phantom is more precise for both translational and rotational adjustments compared to a commercial phantom. The design of the prototype phantom allows for a more discernible visual confirmation of correct translational and rotational adjustments with the prototype phantom. Winston-Lutz results are more accurate for the commercial phantom but are still within tolerance for the prototype phantom.« less