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Nardini M, Capotosti A, Mazzoni LN, Cusumano D, Boldrini L, Chiloiro G, Romano A, Valentini V, Indovina L, Placidi L. Tuning the optimal diffusion-weighted MRI parameters on a 0.35-T MR-Linac for clinical implementation: A phantom study. Front Oncol 2022; 12:867792. [PMID: 36523999 PMCID: PMC9745186 DOI: 10.3389/fonc.2022.867792] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2022] [Accepted: 11/07/2022] [Indexed: 12/06/2023] Open
Abstract
PURPOSE This study aims to assess the quality of a new diffusion-weighted imaging (DWI) sequence implemented on an MR-Linac MRIdian system, evaluating and optimizing the acquisition parameters to explore the possibility of clinically implementing a DWI acquisition protocol in a 0.35-T MR-Linac. MATERIALS AND METHODS All the performed analyses have been carried out on two types of phantoms: a homogeneous 24-cm diameter polymethylmethacrylate (PMMA) sphere (SP) and a homemade phantom (HMP) constating in a PMMA cylinder filled with distilled water with empty sockets into which five cylindrical vials filled with five different concentrations of methylcellulose water solutions have been inserted. SP was used to evaluate the dependence of diffusion gradient inhomogeneity artifacts on gantry position. Four diffusion sequences with b-values of 500 s/mm2 and 3 averages have been acquired: three with diffusion gradients in the three main directions (phase direction, read direction, slice direction) and one with the diffusion gradients switched off. The dependence of diffusion image uniformity and SNR on the number of averages in the MR sequences was also investigated to determine the optimal number of averages. Finally, the ADC values of HMP have been computed and then compared between images acquired in the scanners at 0.35 and 1.5 T. RESULTS In order to acquire high-quality artifact-free DWI images, the "slice" gradient direction has been identified to be the optimal one and 0° to be the best gradient angle. Both the SNR ratio and the uniformity increase with the number of averages. A threshold value of 80 for SNR and 85% for uniformity was adopted to choose the best number of averages. By making a compromise between time and quality and limiting the number of b-values, it is possible to reduce the acquisition time to 78 s. The Passing-Bablok test showed that the two methods, with 0.35 and 1.5 T scanners, led to similar results. CONCLUSION The quality of the DWI has been accurately evaluated in relation to different sequence parameters, and optimal parameters have been identified to select a clinical protocol for the acquisition of ADC maps sustainable in the workflow of a hybrid radiotherapy system with a 0.35-T MRI scanner.
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Affiliation(s)
- Matteo Nardini
- Fondazione Policlinico Universitario “Agostino Gemelli” Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS), Rome, Italy
| | - Amedeo Capotosti
- Fondazione Policlinico Universitario “Agostino Gemelli” Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS), Rome, Italy
| | - Lorenzo Nicola Mazzoni
- Azienda Unità Sanitaria Locale (AUSL) Toscana Centro, Medical Physics Unit, Prato-Pistoia, Italy
| | - Davide Cusumano
- Fondazione Policlinico Universitario “Agostino Gemelli” Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS), Rome, Italy
- Mater Olbia Hospital, UOS Fisica Medica, Olbia, Italy
| | - Luca Boldrini
- Fondazione Policlinico Universitario “Agostino Gemelli” Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS), Rome, Italy
| | - Giuditta Chiloiro
- Fondazione Policlinico Universitario “Agostino Gemelli” Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS), Rome, Italy
| | - Angela Romano
- Fondazione Policlinico Universitario “Agostino Gemelli” Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS), Rome, Italy
| | - Vincenzo Valentini
- Fondazione Policlinico Universitario “Agostino Gemelli” Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS), Rome, Italy
| | - Luca Indovina
- Fondazione Policlinico Universitario “Agostino Gemelli” Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS), Rome, Italy
| | - Lorenzo Placidi
- Fondazione Policlinico Universitario “Agostino Gemelli” Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS), Rome, Italy
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Stanescu T, Shessel A, Carpino-Rocca C, Taylor E, Semeniuk O, Li W, Barry A, Lukovic J, Dawson L, Hosni A. MRI-Guided Online Adaptive Stereotactic Body Radiation Therapy of Liver and Pancreas Tumors on an MR-Linac System. Cancers (Basel) 2022; 14:cancers14030716. [PMID: 35158984 PMCID: PMC8833602 DOI: 10.3390/cancers14030716] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Revised: 01/24/2022] [Accepted: 01/25/2022] [Indexed: 02/06/2023] Open
Abstract
Simple Summary The hybrid magnetic resonance imaging and medical linear accelerator (MR-Linac) systems are expected to revolutionize radiation therapy, uniquely offering high quality soft-tissue contrast and fast imaging to facilitate the online re-planning and guidance of the treatment delivery. While the clinical procedures for stereotactic body radiotherapy are well-established for conventional linacs (with their strengths and weaknesses), they still require significant development and refinement for the MR-Linac systems. Adjustment of fractionation schemes including clinical goals, patient selection, organ motion management, treatment session length, staff logistics, and overall complexity of the online re-planning sessions are key factors that drive the adoption of MR-Linac technologies. In this report, we present the clinical implementation of an MRI-guided radiation therapy workflow, which was used to treat 16 upper gastro-intestinal cancer patients on a 1.5 T MR-Linac platform. The workflow was proven to be feasible for a wide range of clinical scenarios, and the overall treatment session time was significantly reduced as tasks were optimized and the clinical team gradually gained expertise. Abstract Purpose: To describe a comprehensive workflow for MRI-guided online adaptive stereotactic body radiation therapy (SBRT) specific to upper gastrointestinal cancer patients with abdominal compression on a 1.5T MR-Linac system. Additionally, we discuss the workflow’s clinical feasibility and early experience in the case of 16 liver and pancreas patients. Methods: Eleven patients with liver cancer and five patients with pancreas cancer were treated with online adaptive MRI-guidance under abdominal compression. Two liver patients received single-fraction treatments; the remainder plus all pancreas cancer patients received five fractions. A total of 65 treatment sessions were investigated to provide analytics relevant to the online adaptive processes. The quantification of target and organ motion as well as definition and validation of internal target volume (ITV) margins were performed via multi-contrast imaging provided by three different 2D cine sequences. The plan generation was driven by full re-optimization strategies and using T2-weighted 3D image series acquired by means of a respiratory-triggered exhale phase or a time-averaged imaging protocol. As a pre-requisite for the clinical development of the procedure, the image quality was thoroughly investigated via phantom measurements and numerical simulations specific to upper abdominal sites. The delivery of the online adaptive treatments was facilitated by real-time monitoring with 2D cine imaging. Results: Liver 1-fraction and 5-fraction online adaptive session time were on average 80 and 67.5 min, respectively. The total session length varied between 70–90 min for a single fraction and 55–90 min for five fractions. The pancreas sessions were 54–85 min long with an average session time of 68.2 min. Target visualization on the 2D cine image data varied per patient, with at least one of the 2D cine sequences providing sufficient contrast to confidently identify its location and confirm reproducibility of ITV margins. The mean/range of absolute and relative dose values for all treatment sessions evaluated with ArcCheck were 90.6/80.9–96.1% and 99/95.4–100%, respectively. Conclusion: MR-guidance is feasible for liver and pancreas tumors when abdominal compression is used to reduce organ motion, improve imaging quality, and achieve a robust intra- and inter-fraction patient setup. However, the treatment length is significantly longer than for the conventional linac, and patient compliance is paramount for the successful completion of the treatment. Opportunities for reducing the online adaptive session time should be explored. As the next steps, dose-of-the-day and dose accumulation analysis and tools are needed to enhance the workflow and to help further refine the online re-planning processes.
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Affiliation(s)
- Teo Stanescu
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON M5G 2M9, Canada; (A.S.); (C.C.-R.); (E.T.); (O.S.); (W.L.); (A.B.); (J.L.); (L.D.); (A.H.)
- Department of Radiation Oncology, University of Toronto, Toronto, ON M5T 1P5, Canada
- Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, ON M5S 3G8, Canada
- Correspondence:
| | - Andrea Shessel
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON M5G 2M9, Canada; (A.S.); (C.C.-R.); (E.T.); (O.S.); (W.L.); (A.B.); (J.L.); (L.D.); (A.H.)
| | - Cathy Carpino-Rocca
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON M5G 2M9, Canada; (A.S.); (C.C.-R.); (E.T.); (O.S.); (W.L.); (A.B.); (J.L.); (L.D.); (A.H.)
| | - Edward Taylor
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON M5G 2M9, Canada; (A.S.); (C.C.-R.); (E.T.); (O.S.); (W.L.); (A.B.); (J.L.); (L.D.); (A.H.)
- Department of Radiation Oncology, University of Toronto, Toronto, ON M5T 1P5, Canada
| | - Oleksii Semeniuk
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON M5G 2M9, Canada; (A.S.); (C.C.-R.); (E.T.); (O.S.); (W.L.); (A.B.); (J.L.); (L.D.); (A.H.)
| | - Winnie Li
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON M5G 2M9, Canada; (A.S.); (C.C.-R.); (E.T.); (O.S.); (W.L.); (A.B.); (J.L.); (L.D.); (A.H.)
| | - Aisling Barry
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON M5G 2M9, Canada; (A.S.); (C.C.-R.); (E.T.); (O.S.); (W.L.); (A.B.); (J.L.); (L.D.); (A.H.)
- Department of Radiation Oncology, University of Toronto, Toronto, ON M5T 1P5, Canada
| | - Jelena Lukovic
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON M5G 2M9, Canada; (A.S.); (C.C.-R.); (E.T.); (O.S.); (W.L.); (A.B.); (J.L.); (L.D.); (A.H.)
- Department of Radiation Oncology, University of Toronto, Toronto, ON M5T 1P5, Canada
| | - Laura Dawson
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON M5G 2M9, Canada; (A.S.); (C.C.-R.); (E.T.); (O.S.); (W.L.); (A.B.); (J.L.); (L.D.); (A.H.)
- Department of Radiation Oncology, University of Toronto, Toronto, ON M5T 1P5, Canada
| | - Ali Hosni
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON M5G 2M9, Canada; (A.S.); (C.C.-R.); (E.T.); (O.S.); (W.L.); (A.B.); (J.L.); (L.D.); (A.H.)
- Department of Radiation Oncology, University of Toronto, Toronto, ON M5T 1P5, Canada
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