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Chan E, Goodall SK, Finnegan R, Moorfoot P, Jameson M, Dunn L. Dosimetric impact of variable air cavity within PTV for rectum cancer. J Appl Clin Med Phys 2025; 26:e14539. [PMID: 39361507 PMCID: PMC11714072 DOI: 10.1002/acm2.14539] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2024] [Revised: 09/04/2024] [Accepted: 09/23/2024] [Indexed: 10/05/2024] Open
Abstract
PURPOSE The aim of this study is to determine the impact of rectal air volume changes on treatment plan quality, and subsequently inform daily cone-beam computed tomography (CBCT) evaluation constraints, in terms of acceptable rectal air volume during treatment. METHODS Twelve rectal cancer patients who exhibited rectal air within the PTV on their planning CT were selected. A study was conducted to evaluate the deterioration in plan quality due to expanding air volume. For each case, the air cavity volume was isotropically expanded in three dimensions using predefined margins of 3, 5, 7, and 10 mm, while deforming bladder and rectum contours. A constraint was applied to the bony anatomy to restrict the deformation. Treatment plans were then generated for all twelve patients by recalculating the reference plan with the expanded air cavity volume. RESULTS As the air cavity expanded, the maximum relative change in D98% coverage, compared to the reference plan, decreased by 10.8% ± 3.5%, while the D2% increased by 3.5% ± 0.9%. The positioning of the air cavity notably influenced the D98% variability with the 3 mm expansion. D98% coverage falls below 95% when the air cavity volume exceeds 17 cm3. On average, D2% coverage increased by 0.5% with each expansion. At the largest expansion, extensive coverage of 102% and 105% isodoses was observed compared to the reference plan. CONCLUSION Air cavity volumes above 17 cm3 can potentially degrade the high-dose PTV coverage while increasing the regions covered by the 102% and 105% isodoses. Clinical CBCT guidelines were deduced, recommending a maximum threshold of 3.2 cm in diameter in any direction.
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Affiliation(s)
- Eujin Chan
- GenesisCare VictoriaMelbourneVictoriaAustralia
| | - Simon K. Goodall
- GenesisCare Western AustraliaWembleyWestern AustraliaAustralia
- School of Physics, Mathematics, and Computing, Faculty of Engineering and Mathematical SciencesUniversity of Western AustraliaCrawleyWestern AustraliaAustralia
| | - Robert Finnegan
- Royal North Shore HospitalNorthern Sydney Cancer CentreSt LeonardsNew South WalesAustralia
| | | | - Michael Jameson
- GenesisCare New South WalesAlexandriaNew South WalesAustralia
- University of New South WalesSydneyNew South WalesAustralia
- University of WollongongWollongongNew South WalesAustralia
| | - Leon Dunn
- GenesisCare VictoriaMelbourneVictoriaAustralia
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Oliver PAK, Yip E, Tari SY, Wachowicz K, Reynolds M, Burke B, Warkentin B, Fallone BG. Skin dose investigations on a 0.5 T parallel rotating biplanar linac-MR using Monte Carlo simulations and measurements. Med Phys 2024; 51:6317-6331. [PMID: 38873942 DOI: 10.1002/mp.17246] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2024] [Revised: 05/06/2024] [Accepted: 05/30/2024] [Indexed: 06/15/2024] Open
Abstract
BACKGROUND The Alberta rotating biplanar linac-MR has a 0.5 T magnetic field parallel to the beamline. When developing a new linac-MR system, interactions of charged particles with the magnetic field necessitate careful consideration of skin dose and tissue interface effects. PURPOSE To investigate the effect of the magnetic field on skin dose using measurements and Monte Carlo (MC) simulations. METHODS We develop an MC model of our linac-MR, which we validate by comparison with ion chamber measurements in a water tank. Additionally, MC simulation results are compared with radiochromic film surface dose measurements on solid water. Variations in surface dose as a function of field size are measured using a parallel plate ion chamber in solid water. Using an anthropomorphic computational phantom with a 2 mm-thick skin layer, we investigate dose distributions resulting from three beam arrangements. Magnetic field on and off scenarios are considered for all measurements and simulations. RESULTS For a 20 × 20 cm2 field size,D 0.2 c c ${D_{0.2cc}}$ (the minimum dose to the hottest contiguous 0.2 cc volume) for the top 2 mm of a simple water phantom is 72% when the magnetic field is on, compared to 34% with magnetic field off (values are normalized to the central axis dose maximum). Parallel plate ion chamber measurements demonstrate that the relative increase in surface dose due to the magnetic field decreases with increasing field size. For the anthropomorphic phantom,D ∼ 0.2 c c ${D_{ \sim 0.2cc}}$ (minimum skin dose in the hottest 1 × 1 × 1 cm3 cube) shows relative increases of 20%-28% when the magnetic field is on compared to when it is off. With magnetic field off, skinD ∼ 0.2 c c ${D_{ \sim 0.2cc}}$ is 71%, 56%, and 21% for medial-lateral tangents, anterior-posterior beams, and a five-field arrangement, respectively. For magnetic field on, the corresponding skinD ∼ 0.2 c c ${D_{ \sim 0.2cc}}$ values are 91%, 67%, and 25%. CONCLUSIONS Using a validated MC model of our linac-MR, surface doses are calculated in various scenarios. MC-calculated skin dose varies depending on field sizes, obliquity, and the number of beams. In general, the parallel linac-MR arrangement results in skin dose enhancement due to charged particles spiraling along magnetic field lines, which impedes lateral motion away from the central axis. Nonetheless, considering the results presented herein, treatment plans can be designed to minimize skin dose by, for example, avoiding oblique beams and using a larger number of fields.
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Affiliation(s)
- Patricia A K Oliver
- Dept. of Medical Physics, Cross Cancer Institute, Edmonton, Alberta, Canada
- Dept. of Oncology, Medical Physics Division, University of Alberta, Edmonton, Alberta, Canada
- Dept. of Medical Physics, Nova Scotia Health and Dept. of Radiation Oncology, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Eugene Yip
- Dept. of Medical Physics, Cross Cancer Institute, Edmonton, Alberta, Canada
- Dept. of Oncology, Medical Physics Division, University of Alberta, Edmonton, Alberta, Canada
| | - Shima Y Tari
- Dept. of Medical Physics, Cross Cancer Institute, Edmonton, Alberta, Canada
- Dept. of Oncology, Medical Physics Division, University of Alberta, Edmonton, Alberta, Canada
| | - Keith Wachowicz
- Dept. of Medical Physics, Cross Cancer Institute, Edmonton, Alberta, Canada
- Dept. of Oncology, Medical Physics Division, University of Alberta, Edmonton, Alberta, Canada
| | - Michael Reynolds
- Dept. of Medical Physics, Cross Cancer Institute, Edmonton, Alberta, Canada
| | - Ben Burke
- Dept. of Medical Physics, Cross Cancer Institute, Edmonton, Alberta, Canada
- Dept. of Oncology, Medical Physics Division, University of Alberta, Edmonton, Alberta, Canada
| | - Brad Warkentin
- Dept. of Medical Physics, Cross Cancer Institute, Edmonton, Alberta, Canada
- Dept. of Oncology, Medical Physics Division, University of Alberta, Edmonton, Alberta, Canada
| | - B Gino Fallone
- Dept. of Medical Physics, Cross Cancer Institute, Edmonton, Alberta, Canada
- Dept. of Oncology, Medical Physics Division, University of Alberta, Edmonton, Alberta, Canada
- MagnetTx Oncology Solutions, Edmonton, Alberta, Canada
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Westley R, Casey F, Mitchell A, Alexander S, Nill S, Murray J, Ratnakumaran R, Pathmanathan A, Oelfke U, Dunlop A, Tree AC. Stereotactic Body Radiotherapy (SBRT) to Localised Prostate Cancer in the Era of MRI-Guided Adaptive Radiotherapy: Doses Delivered in the HERMES Trial Comparing Two- and Five-Fraction Treatments. Cancers (Basel) 2024; 16:2073. [PMID: 38893193 PMCID: PMC11171331 DOI: 10.3390/cancers16112073] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2024] [Revised: 05/19/2024] [Accepted: 05/20/2024] [Indexed: 06/21/2024] Open
Abstract
HERMES is a phase II trial of MRI-guided daily-adaptive radiotherapy (MRIgART) randomising men with localised prostate cancer to either 2-fractions of SBRT with a boost to the tumour or 5-fraction SBRT. In the context of this highly innovative regime the dose delivered must be carefully considered. The first ten patients recruited to HERMES were analysed in order to establish the dose received by the targets and organs at risk (OARS) in the context of intrafraction motion. A regression analysis was performed to measure how the volume of air within the rectum might further impact rectal dose secondary to the electron return effect (ERE). One hundred percent of CTV target objectives were achieved on the MRI taken prior to beam-on-time. The post-delivery MRI showed that high-dose CTV coverage was achieved in 90% of sub-fractions (each fraction is delivered in two sub-fractions) in the 2-fraction cohort and in 88% of fractions the 5-fraction cohort. Rectal D1 cm3 was the most exceeded constraint; three patients exceeded the D1 cm3 < 20.8 Gy in the 2-fraction cohort and one patient exceeded the D1 cm3 < 36 Gy in the 5-fraction cohort. The volume of rectal gas within 1 cm of the prostate was directly proportional to the increase in rectal D1 cm3, with a strong (R = 0.69) and very strong (R = 0.90) correlation in the 2-fraction and 5-fraction cohort respectively. Dose delivery specified in HERMES is feasible, although for some patients delivered doses to both target and OARs may vary from those planned.
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Affiliation(s)
- Rosalyne Westley
- The Royal Marsden NHS Foundation Trust, London SM2 5PT, UK
- Radiotherapy and Imaging Division, Institute of Cancer Research, London SM2 5NG, UK
| | - Francis Casey
- Joint Department of Physics, The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, London SM2 5PT, UK
| | - Adam Mitchell
- Joint Department of Physics, The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, London SM2 5PT, UK
| | - Sophie Alexander
- The Royal Marsden NHS Foundation Trust, London SM2 5PT, UK
- Radiotherapy and Imaging Division, Institute of Cancer Research, London SM2 5NG, UK
| | - Simeon Nill
- Joint Department of Physics, The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, London SM2 5PT, UK
| | - Julia Murray
- The Royal Marsden NHS Foundation Trust, London SM2 5PT, UK
- Radiotherapy and Imaging Division, Institute of Cancer Research, London SM2 5NG, UK
| | - Ragu Ratnakumaran
- The Royal Marsden NHS Foundation Trust, London SM2 5PT, UK
- Radiotherapy and Imaging Division, Institute of Cancer Research, London SM2 5NG, UK
| | - Angela Pathmanathan
- The Royal Marsden NHS Foundation Trust, London SM2 5PT, UK
- Radiotherapy and Imaging Division, Institute of Cancer Research, London SM2 5NG, UK
| | - Uwe Oelfke
- Joint Department of Physics, The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, London SM2 5PT, UK
| | - Alex Dunlop
- Joint Department of Physics, The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, London SM2 5PT, UK
| | - Alison C. Tree
- The Royal Marsden NHS Foundation Trust, London SM2 5PT, UK
- Radiotherapy and Imaging Division, Institute of Cancer Research, London SM2 5NG, UK
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Nardini M, Meffe G, Galetto M, Boldrini L, Chiloiro G, Romano A, Panza G, Bevacqua A, Turco G, Votta C, Capotosti A, Moretti R, Gambacorta MA, Indovina L, Placidi L. Why we should care about gas pockets in online adaptive MRgRT: a dosimetric evaluation. Front Oncol 2023; 13:1280836. [PMID: 38023178 PMCID: PMC10679396 DOI: 10.3389/fonc.2023.1280836] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Accepted: 10/27/2023] [Indexed: 12/01/2023] Open
Abstract
Introduction Contouring of gas pockets is a time consuming step in the workflow of adaptive radiotherapy. We would like to better understand which gas pockets electronic densitiy should be used and the dosimetric impact on adaptive MRgRT treatment. Materials and methods 21 CT scans of patients undergoing SBRT were retrospectively evaluated. Anatomical structures were contoured: Gross Tumour Volume (GTV), stomach (ST), small bowel (SB), large bowel (LB), gas pockets (GAS) and gas in each organ respectively STG, SBG, LBG. Average HU in GAS was converted in RED, the obtained value has been named as Gastrointestinal Gas RED (GIGED). Differences of average HU in GAS, STG, SBG and LBG were computed. Three treatment plans were calculated editing the GAS volume RED that was overwritten with: air RED (0.0012), water RED (1.000), GIGED, generating respectively APLAN, WPLAN and the GPLAN. 2-D dose distributions were analyzed by gamma analysis. Parameter called active gas volume (AGV) was calculated as the intersection of GAS with the isodose of 5% of prescription dose. Results Average HU value contained in GAS results to be equal to -620. No significative difference was noted between the average HU of gas in different organ at risk. Value of Gamma Passing Rate (GPR) anticorrelates with the AGV for each plan comparison and the threshold value for GPR to fall below 90% is 41, 60 and 139 cc for WPLANvsAPLAN, GPLANvsAPLAN and WPLANvsGPLAN respectively. Discussions GIGED is the right RED for Gastrointestinal Gas. Novel AGV is a useful parameter to evaluate the effect of gas pocket on dose distribution.
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Affiliation(s)
- Matteo Nardini
- Fondazione Policlinico Universitario ‘‘A. Gemelli’’ IRCCS, Rome, Italy
| | - Guenda Meffe
- Fondazione Policlinico Universitario ‘‘A. Gemelli’’ IRCCS, Rome, Italy
| | - Matteo Galetto
- Radiotherapy Department, Università Cattolica del Sacro Cuore, Rome, Italy
| | - Luca Boldrini
- Fondazione Policlinico Universitario ‘‘A. Gemelli’’ IRCCS, Rome, Italy
| | - Giuditta Chiloiro
- Fondazione Policlinico Universitario ‘‘A. Gemelli’’ IRCCS, Rome, Italy
| | - Angela Romano
- Fondazione Policlinico Universitario ‘‘A. Gemelli’’ IRCCS, Rome, Italy
| | - Giulia Panza
- Fondazione Policlinico Universitario ‘‘A. Gemelli’’ IRCCS, Rome, Italy
| | - Andrea Bevacqua
- Fondazione Policlinico Universitario ‘‘A. Gemelli’’ IRCCS, Rome, Italy
| | - Gabriele Turco
- Fondazione Policlinico Universitario ‘‘A. Gemelli’’ IRCCS, Rome, Italy
| | - Claudio Votta
- Fondazione Policlinico Universitario ‘‘A. Gemelli’’ IRCCS, Rome, Italy
| | - Amedeo Capotosti
- Fondazione Policlinico Universitario ‘‘A. Gemelli’’ IRCCS, Rome, Italy
| | - Roberto Moretti
- Fondazione Policlinico Universitario ‘‘A. Gemelli’’ IRCCS, Rome, Italy
| | - Maria Antonietta Gambacorta
- Fondazione Policlinico Universitario ‘‘A. Gemelli’’ IRCCS, Rome, Italy
- Radiotherapy Department, Università Cattolica del Sacro Cuore, Rome, Italy
| | - Luca Indovina
- Fondazione Policlinico Universitario ‘‘A. Gemelli’’ IRCCS, Rome, Italy
| | - Lorenzo Placidi
- Fondazione Policlinico Universitario ‘‘A. Gemelli’’ IRCCS, Rome, Italy
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Liu X, Yin P, Li T, Yin Y, Li Z. Influence and optimization strategy of the magnetic field in 1.5 T MR-linac liver stereotactic radiotherapy. Radiat Oncol 2023; 18:162. [PMID: 37794505 PMCID: PMC10548616 DOI: 10.1186/s13014-023-02356-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2023] [Accepted: 09/26/2023] [Indexed: 10/06/2023] Open
Abstract
OBJECTIVE To compare intensity reduction plans for liver cancer with or without a magnetic field and optimize field and subfield numbers in the intensity-modulated radiotherapy (IMRT) plans designed for liver masses in different regions. METHODS This retrospective study included 62 patients who received radiotherapy for liver cancer at Shandong Cancer Hospital. Based on each patient's original individualized intensity-modulated plan (plan1.5 T), a magnetic field-free plan (plan0 T) and static intensity-modulated plan with four different optimization schemes were redesigned for each patient. The differences in dosimetric parameters among plans were compared. RESULTS In the absence of a magnetic field in the first quadrant, PTV Dmin increased (97.75 ± 17.55 vs. 100.96 ± 22.78)%, Dmax decreased (121.48 ± 29.68 vs. 119.06 ± 28.52)%, D98 increased (101.35 ± 7.42 vs. 109.35 ± 26.52)% and HI decreased (1.14 ± 0.14 vs. 1.05 ± 0.01). In the absence of a magnetic field in the second quadrant, PTV Dmin increased (84.33 ± 19.74 vs. 89.96 ± 21.23)%, Dmax decreased (105 ± 25.08 vs. 104.05 ± 24.86)%, and HI decreased (1.04 ± 0.25 vs. 0.99 ± 0.24). In the absence of a magnetic field in the third quadrant, PTV Dmax decreased (110.21 ± 2.22 vs. 102.31 ± 26)%, L-P V30 decreased (10.66 ± 9.19 vs. 5.81 ± 3.22)%, HI decreased (1.09 ± 0.02 vs. 0.98 ± 0.25), and PTV Dmin decreased (92.12 ± 4.92 vs. 89.1 ± 22.35)%. In the absence of a magnetic field in the fourth quadrant, PTV Dmin increased (89.78 ± 6.72 vs. 93.04 ± 4.86)%, HI decreased (1.09 ± 0.01 vs. 1.05 ± 0.01) and D98 increased (99.82 ± 0.82 vs. 100.54 ± 0.84)%. These were all significant differences. In designing plans for tumors in each liver region, a total number of subfields in the first area of 60, total subfields in the second zone of 80, and total subfields in the third and fourth zones of 60 or 80 can achieve the dose effect without a magnetic field. CONCLUSION In patients with liver cancer, the effect of a magnetic field on the target dose is more significant than that on doses to organs at risk. By controlling the max total number of subfields in different quadrants, the effect of the magnetic field can be greatly reduced or even eliminated.
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Affiliation(s)
- Xin Liu
- Department of Oncology, The Affiliated Hospital of Southwest Medical University, Luzhou, 646000, China
- Department of Radiation Physics, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, 250117, China
| | - Peijun Yin
- Department of Radiation Physics, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, 250117, China
| | - Tengxiang Li
- School of Nuclear Science and Technology, University of South China, Hengyang, 421001, China
| | - Yong Yin
- Department of Oncology, The Affiliated Hospital of Southwest Medical University, Luzhou, 646000, China.
- Department of Radiation Physics, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, 250117, China.
| | - Zhenjiang Li
- Department of Radiation Physics, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, 250117, China.
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Lapaeva M, La Greca Saint-Esteven A, Wallimann P, Günther M, Konukoglu E, Andratschke N, Guckenberger M, Tanadini-Lang S, Dal Bello R. Synthetic computed tomographies for low-field magnetic resonance-guided radiotherapy in the abdomen. Phys Imaging Radiat Oncol 2022; 24:173-179. [DOI: 10.1016/j.phro.2022.11.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2022] [Revised: 11/13/2022] [Accepted: 11/23/2022] [Indexed: 11/29/2022] Open
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Dosimetric Effects of Air Cavities for MRI-Guided Online Adaptive Radiation Therapy (MRgART) of Prostate Bed after Radical Prostatectomy. J Clin Med 2022; 11:jcm11020364. [PMID: 35054061 PMCID: PMC8780446 DOI: 10.3390/jcm11020364] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2021] [Revised: 01/08/2022] [Accepted: 01/10/2022] [Indexed: 02/06/2023] Open
Abstract
PURPOSE To evaluate dosimetric impact of air cavities and their corresponding electron density correction for 0.35 tesla (T) Magnetic Resonance-guided Online Adaptive Radiation Therapy (MRgART) of prostate bed patients. METHODS Three 0.35 T MRgRT plans (anterior-posterior (AP) beam, AP-PA beams, and clinical intensity modulated radiation therapy (IMRT)) were generated on a prostate bed patient's (Patient A) planning computed tomography (CT) with artificial rectal air cavities of various sizes (0-3 cm, 0.5 cm increments). Furthermore, two 0.35 T MRgART plans ('Deformed' and 'Override') were generated on a prostate bed patient's (Patient B) daily magnetic resonance image (MRI) with artificial rectal air cavities of various sizes (0-3 cm, 0.5 cm increments) and on five prostate bed patient's (Patient 1-5) daily MRIs (2 MRIs: Fraction A and B) with real air cavities. For each MRgART plan, daily MRI electron density map was obtained by deformable registration with simulation CT. In the 'Deformed' plan, a clinical IMRT plan is calculated on the daily MRI with electron density map obtained from deformable registration only. In the 'Override' plan, daily MRI and simulation CT air cavities are manually corrected and bulk assigned air and water density on the registered electron density map, respectively. Afterwards, the clinical IMRT plan is calculated. RESULTS For the MRgRT plans, AP and AP-PA plans' rectum/rectal wall max dose increased with increasing air cavity size, where the 3 cm air cavity resulted in a 20%/17% and 13%/13% increase, relative to no air cavity, respectively. Clinical IMRT plan was robust to air cavity size, where dose change remained less than 1%. For the MRgART plans, daily MRI electron density maps, obtained from deformable registration with simulation CT, was unable to accurately produce electron densities reflecting the air cavities. However, for the artificial daily MRI air cavities, dosimetric change between 'Deformed' and 'Override' plan was small (<4%). Similarly, for the real daily MRI air cavities, clinical constraint changes between 'Deformed' and 'Override' plan was negligible and did not lead to change in clinical decision for adaptive planning except for two fractions. In these fractions, the 'Override' plan indicated that the bladder max dose and rectum V35.7 exceeded the constraint, while the 'Deformed' plan showed acceptable dose, although the absolute difference was only 0.3 Gy and 0.03 cc, respectively. CONCLUSION Clinical 0.35 T IMRT prostate bed plans are dosimetrically robust to air cavities. MRgART air cavity electron density correction shows clinically insignificant change and is not warranted on low-field systems.
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Ricotti R, Pella A, Mirandola A, Fiore MR, Chalaszczyk A, Paganelli C, Antonioli L, Vai A, Tagaste B, Belotti G, Rossi M, Ciocca M, Orlandi E, Baroni G. Dosimetric effect of variable rectum and sigmoid colon filling during carbon ion radiotherapy to sacral chordoma. Phys Med 2021; 90:123-133. [PMID: 34628271 DOI: 10.1016/j.ejmp.2021.09.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/26/2021] [Revised: 08/13/2021] [Accepted: 09/23/2021] [Indexed: 11/17/2022] Open
Abstract
PURPOSE Carbon ion radiotherapy (CIRT) is sensitive to anatomical density variations. We examined the dosimetric effect of variable intestinal filling condition during CIRT to ten sacral chordoma patients. METHODS For each patient, eight virtual computed tomography scans (vCTs) were generated by varying the density distribution within the rectum and the sigmoid in the planning computed tomography (pCT) with a density override approach mimicking a heterogeneous combination of gas and feces. Totally full and empty intestinal preparations were modelled. In addition, five different intestinal filling conditions were modelled by a mixed density pattern derived from two combined and weighted Gaussian distributions simulating gas and feces respectively. Finally, a patient-specific mixing proportion was estimated by evaluating the daily amount of gas detected in the cone beam computed tomography (CBCT). Dose distribution was recalculated on each vCT and dose volume histograms (DVHs) were examined. RESULTS No target coverage degradation was observed at different vCTs. Rectum and sigma dose degradation ranged respectively between: [-6.7; 21.6]GyE and [-0.7; 15.4]GyE for D50%; [-377.4; 1197.9] and [-95.2; 1027.5] for AUC; [-1.2; 10.7]GyE and [-2.6; 21.5]GyE for D1%. CONCLUSIONS Variation of intestinal density can greatly influence the penetration depth of charged particle and might compromise dose distribution. In particular cases, with large clinical target volume in very close proximity to rectum and sigmoid colon, it is appropriate to evaluate the amount of gas present in the daily CBCT images even if it is totally included in the reference planning structures.
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Affiliation(s)
- R Ricotti
- Bioengineering Unit, Clinical Department, National Center for Oncological Hadrontherapy (CNAO), Pavia, Italy.
| | - A Pella
- Bioengineering Unit, Clinical Department, National Center for Oncological Hadrontherapy (CNAO), Pavia, Italy
| | - A Mirandola
- Medical Physics Unit, Clinical Department, National Center for Oncological Hadrontherapy (CNAO), Pavia, Italy
| | - M R Fiore
- Radiation Oncology Unit, Clinical Department, National Center for Oncological Hadrontherapy (CNAO), Pavia, Italy
| | - A Chalaszczyk
- Radiation Oncology Unit, Clinical Department, National Center for Oncological Hadrontherapy (CNAO), Pavia, Italy
| | - C Paganelli
- Department of Electronics Information and Bioengineering, Politecnico di Milano, Milano, Italy
| | - L Antonioli
- Bioengineering Unit, Clinical Department, National Center for Oncological Hadrontherapy (CNAO), Pavia, Italy
| | - A Vai
- Medical Physics Unit, Clinical Department, National Center for Oncological Hadrontherapy (CNAO), Pavia, Italy
| | - B Tagaste
- Bioengineering Unit, Clinical Department, National Center for Oncological Hadrontherapy (CNAO), Pavia, Italy
| | - G Belotti
- Department of Electronics Information and Bioengineering, Politecnico di Milano, Milano, Italy
| | - M Rossi
- Department of Electronics Information and Bioengineering, Politecnico di Milano, Milano, Italy
| | - M Ciocca
- Medical Physics Unit, Clinical Department, National Center for Oncological Hadrontherapy (CNAO), Pavia, Italy
| | - E Orlandi
- Radiation Oncology Unit, Clinical Department, National Center for Oncological Hadrontherapy (CNAO), Pavia, Italy
| | - G Baroni
- Bioengineering Unit, Clinical Department, National Center for Oncological Hadrontherapy (CNAO), Pavia, Italy; Department of Electronics Information and Bioengineering, Politecnico di Milano, Milano, Italy
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