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Title: SU-F-T-580: New Tumor Modeling Using 3D Gel Dosimeter for Brain Stereoctactic Radiotherpy (SRT)

Abstract

Purpose: The purpose of this study is to develop new tumor model using 3D printing with 3D dosimeter for brain stereoctactic radiotherpy (SRT). Methods: BANG{sup 3} polymer gel was prepared and the gel-filled glass vials were irradiated with a 6 MV photon beam to acquire the calibration curve that present the change of R2 (1/T{sub 2}) value with dose. Graded doses from 0 to 12 Gy with an interval of 2 Gy were delivered. A kit for calibration of gel dosimeter and an 2 tumor model phantoms with a spherical shape were produced using a 3D printer with a polylactic acid after its 3D images were created using Autodesk software. 3D printed tumor phantoms and EBT3 films were irradiated to compare with treatment plan. After irradiation, vials for calibration and tumor model phantoms were scanned at 9.4T MRI. The spin-spin relaxation times (T{sub 2}) according to the each dose were calculated to evaluate the dose response. Acquired images were analyzed using an ImageJ. Scanned MRI images of tumor models were transferred treatment planning system and these were registered to the CT images. In all treatment plans, two arc plans (CW and CCW) were designed to deliver 50 Gy for 10more » fractions. For first PTV, treatment plan was accurately designed that 95% of dose to cover 100% of PTV. But 2nd PTV was not intentionally cover 100% of PTV to evaluate the intensity of delivered tumor phantom with polymer gel. We compared the 3D dose distributions obtained from measurements with the 3D printed phantom and calculated with the TPS. Results: 3D printed phantom with a polymer gel was successfully produced. The dose distributions showed qualitatively good agreement among gel, film, and RTP data. Conclusion: A hybrid phantom represents a useful to validate the 3D dose distributions for patient-specific QA.« less

Authors:
; ; ; ; ; ; ;  [1]
  1. Asan Medical Center, Seoul, Seoul (Korea, Republic of)
Publication Date:
OSTI Identifier:
22649155
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 43; Journal Issue: 6; Other Information: (c) 2016 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; 61 RADIATION PROTECTION AND DOSIMETRY; BRAIN; CALIBRATION; CAT SCANNING; COMPUTER CODES; DOSEMETERS; GELS; IMAGES; IRRADIATION; NEOPLASMS; NMR IMAGING; PHANTOMS; PHOTON BEAMS; PLANNING; POLYMERS; RADIATION DOSE DISTRIBUTIONS; SIMULATION

Citation Formats

Chang, K, Kim, M, Kwak, J, Kim, S, Ji, Y, Cho, B, Yoon, S, and Lee, S. SU-F-T-580: New Tumor Modeling Using 3D Gel Dosimeter for Brain Stereoctactic Radiotherpy (SRT). United States: N. p., 2016. Web. doi:10.1118/1.4956765.
Chang, K, Kim, M, Kwak, J, Kim, S, Ji, Y, Cho, B, Yoon, S, & Lee, S. SU-F-T-580: New Tumor Modeling Using 3D Gel Dosimeter for Brain Stereoctactic Radiotherpy (SRT). United States. doi:10.1118/1.4956765.
Chang, K, Kim, M, Kwak, J, Kim, S, Ji, Y, Cho, B, Yoon, S, and Lee, S. 2016. "SU-F-T-580: New Tumor Modeling Using 3D Gel Dosimeter for Brain Stereoctactic Radiotherpy (SRT)". United States. doi:10.1118/1.4956765.
@article{osti_22649155,
title = {SU-F-T-580: New Tumor Modeling Using 3D Gel Dosimeter for Brain Stereoctactic Radiotherpy (SRT)},
author = {Chang, K and Kim, M and Kwak, J and Kim, S and Ji, Y and Cho, B and Yoon, S and Lee, S},
abstractNote = {Purpose: The purpose of this study is to develop new tumor model using 3D printing with 3D dosimeter for brain stereoctactic radiotherpy (SRT). Methods: BANG{sup 3} polymer gel was prepared and the gel-filled glass vials were irradiated with a 6 MV photon beam to acquire the calibration curve that present the change of R2 (1/T{sub 2}) value with dose. Graded doses from 0 to 12 Gy with an interval of 2 Gy were delivered. A kit for calibration of gel dosimeter and an 2 tumor model phantoms with a spherical shape were produced using a 3D printer with a polylactic acid after its 3D images were created using Autodesk software. 3D printed tumor phantoms and EBT3 films were irradiated to compare with treatment plan. After irradiation, vials for calibration and tumor model phantoms were scanned at 9.4T MRI. The spin-spin relaxation times (T{sub 2}) according to the each dose were calculated to evaluate the dose response. Acquired images were analyzed using an ImageJ. Scanned MRI images of tumor models were transferred treatment planning system and these were registered to the CT images. In all treatment plans, two arc plans (CW and CCW) were designed to deliver 50 Gy for 10 fractions. For first PTV, treatment plan was accurately designed that 95% of dose to cover 100% of PTV. But 2nd PTV was not intentionally cover 100% of PTV to evaluate the intensity of delivered tumor phantom with polymer gel. We compared the 3D dose distributions obtained from measurements with the 3D printed phantom and calculated with the TPS. Results: 3D printed phantom with a polymer gel was successfully produced. The dose distributions showed qualitatively good agreement among gel, film, and RTP data. Conclusion: A hybrid phantom represents a useful to validate the 3D dose distributions for patient-specific QA.},
doi = {10.1118/1.4956765},
journal = {Medical Physics},
number = 6,
volume = 43,
place = {United States},
year = 2016,
month = 6
}
  • Purpose: To clinically evaluate a highly accelerated T1-weighted dynamic contrast-enhanced (DCE) MRI technique that provides high spatial resolution and whole-brain coverage via undersampling and constrained reconstruction with multiple sparsity constraints. Methods: Conventional (rate-2 SENSE) and experimental DCE-MRI (rate-30) scans were performed 20 minutes apart in 15 brain tumor patients. The conventional clinical DCE-MRI had voxel dimensions 0.9 × 1.3 × 7.0 mm{sup 3}, FOV 22 × 22 × 4.2 cm{sup 3}, and the experimental DCE-MRI had voxel dimensions 0.9 × 0.9 × 1.9 mm{sup 3}, and broader coverage 22 × 22 × 19 cm{sup 3}. Temporal resolution was 5 smore » for both protocols. Time-resolved images and blood–brain barrier permeability maps were qualitatively evaluated by two radiologists. Results: The experimental DCE-MRI scans showed no loss of qualitative information in any of the cases, while achieving substantially higher spatial resolution and whole-brain spatial coverage. Average qualitative scores (from 0 to 3) were 2.1 for the experimental scans and 1.1 for the conventional clinical scans. Conclusions: The proposed DCE-MRI approach provides clinically superior image quality with higher spatial resolution and coverage than currently available approaches. These advantages may allow comprehensive permeability mapping in the brain, which is especially valuable in the setting of large lesions or multiple lesions spread throughout the brain.« less
  • Purpose: This work presents an end-to-end test using a Gel-Alanine phantom to validate the three-dimensional (3D) dose distribution (DD) delivered by a single isocenter VMAT technique on the simultaneous treatment of multiple brain metastases. Methods: Three cylindrical phantons containing MAGIC-f gel dosimeter were used to measure the 3D DD of a VMAT treatment, the first two were filled with the gel dosimeter (Gel 1 and 2) and the third one was filled with gel and 12 alanine dosimeters distributed along it (Gel 3). Gels 1 and 3 were irradiated and gel 2 was used to map the magnetic resonance imagemore » (MRI) scanner field inomogeneities. A CT scan of gel 3 was used for the VMAT treatment planning and 5 alanine pellets were chosen as lesions, around them a PTV was grown and different dose prescriptions were assigned for each one, varying from 5 to 9Gy. Before treatment, the plan was approved in a QA based on an ionization chamber absolute dose measurement, a radiochromic film planar dose measurement and a portal dosimetry per field verification; and also the phantons positioning were verified by ExacTrac 6D correction and OBI kV Cone Beam CT. The gels were irradiated, the MRIs were acquired 24 hours after irradiation and finally, the alanine dosimeters were analysed in a X-band Electron Spin Resonance spectrometer. Results: The association of the two detectors enabled the 3D dose evaluation by gel and punctually inside target volumes by alanine. In the gamma analyses (3%/3mm) comparing the 5 PTVs’ central images DD with TPS expected DD more than 95% of the points were approved. The alanine absolute dose measurements were in agreement with TPS by less than 5%. Conclusion: The gel-alanine phantom enabled the dosimetric validation of multiple brain metastases treatment using VMAT, being an almost ideal tool for this application. This work is partially supported by FAPESP.« less
  • An evaluation was made of the ability of different isotopes, injected intravenously, to give a higher concentration in brain tumors and other pathological cerebral tissues than in normal brain tissue. Thus, a comparison was made of various isotopes and labeled substances in the same system, to determine which could be expected to give the best results in patients, and to find out more about the mechanism of the method. Uptake of the radioactive substances was measured at different times after injection, in brain, tumor and other organs in rats with subcutaneous transplanted fibrosarcoma. Each radioactive substance was investigated in onlymore » a few animals as these experiments were intended to detect large differences between substances, and not to obtain accurate values of organ concentrations or extracellular spaces. Bi/sup 206/ gives much higher tumor brain concentration ratios than any other isotope tested. This can be accounted for by considering that it is an intracellular ion which is rapidly cleared from the blood and which enters brain slowly. Its low concentration in muscle and blood makes this isotope especially suitable for brain tumor localization. Br/sup 82/, Ga/sup 68/, Zr/sup 95/, Sb/sup 122/, I/ sup 131/ , I/sup 131/iododeoxyuridine, AgNonel, NbNonegNones, and NonelNonelNoneaNonelNone-human seru m albumin behave as extracellular substances up to the times studied (2 days), and equilibrate with the extracellular spaces of tumor and brain. These substances therefore all give a tumor/brain concentration ratio of about 8-25: 1 (except Br/sup 82/, which probably enters brain cells). For these substances, tumor and brain concentrations are roughly proportional to blood concentration. The Ag/sup */ used consisted of Ag/sup 105/ , Ag/sup 106/, Ag/sup 110/, and Ag/sup 111/. K/sup 43/, Rb/sup 84/ , An/sup 65/, Hg/sup 203/ (as neohydrin), Bi/sup 206/ and Mn/sup 52/ behave as intracellular substances. Their concentrations in tumor do not vary greatly and are independent of blood concentration. In brain their concentrations are roughly proportional to blood concentration. The tumor/brain concentration ratio therefore varies with blood concentration and is greatest for those which are rapidly cleared from the blood such as Bi/sup 206/. These results are consistent with two possible explanations for the blood-brain barrier: that it is due to both lack of extracellular space and to reduced cell permeability or uptake in the brain, and that it is due to a physical barrier impermeable to extracellular substances but slowly permeable to intracellular substances. As/sup 74/ is concentrated by red cells in rats, but not in man. In rats nearly all the radioactivity is in the blood several hr after injection. The concentration in kidney is also high, and the lowest concentrations are in the brain, muscle, and intestine. When the effect of increasing the amount of carrier injected was investigated, for K/sup 43/ there was no effect, since stable K is already present. For arsenite there was no significant effect, but with arsenate the addition of carrier greatly reduced red cell uptake and kidney concentration and increased excretion, since both tumor and brain concentration were reduced. For Ag/sup */ and Bi/sup 206/ nitrate, addition of carrier causes precipitation of AgCl and BiONO/sub 3/, respectively, and hence increased uptake by the reticuloendothelial system. For Bi/sup 206/ nitrate this reduced tumor uptake considerably with little effect on brain uptake. Bi/sup 206/ citrate is more soluble, and addition of carrier did not cause precipitation, and therefore reduces tumor uptake to a much smaller extent. With Ag/sup */, tumor uptake appeared to increase by addition of carrier, while brain uptake was decreased. (BBB)« less