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Milgrom SA, van Luijk P, Pino R, Ronckers CM, Kremer LC, Gidley PW, Grosshans DR, Laskar S, Okcu MF, Constine LS, Paulino AC. Salivary and Dental Complications in Childhood Cancer Survivors Treated With Radiation Therapy to the Head and Neck: A PENTEC Comprehensive Review. Int J Radiat Oncol Biol Phys 2024; 119:467-481. [PMID: 34074567 DOI: 10.1016/j.ijrobp.2021.04.023] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Revised: 03/14/2021] [Accepted: 04/21/2021] [Indexed: 12/24/2022]
Abstract
PURPOSE Radiation therapy (RT) to the head and neck (H&N) region is critical in the management of various pediatric malignancies; however, it may result in late toxicity. This comprehensive review from the Pediatric Normal Tissue Effects in the Clinic (PENTEC) initiative focused on salivary dysfunction and dental abnormalities in survivors who received RT to the H&N region as children. MATERIALS & METHODS This systematic review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) method. RESULTS Of the 2,164 articles identified through a literature search, 40 were included in a qualitative synthesis and 3 were included in a quantitative synthesis. The dose-toxicity data regarding salivary function demonstrate that a mean parotid dose of 35 to 40 Gy is associated with a risk of acute and chronic grade ≥2 xerostomia of approximately 32% and 13% to 32%, respectively, in patients treated with chemo-radiation therapy. This risk increases with parotid dose; however, rates of xerostomia after lower dose exposure have not been reported. Dental developmental abnormalities are common after RT to the oral cavity. Risk factors include higher radiation dose to the developing teeth and younger age at RT. CONCLUSIONS This PENTEC task force considers adoption of salivary gland dose constraints from the adult experience to be a reasonable strategy until more data specific to children become available; thus, we recommend limiting the parotid mean dose to ≤26 Gy. The minimum toxic dose for dental developmental abnormalities is unknown, suggesting that the dose to the teeth should be kept as low as possible particularly in younger patients, with special effort to keep doses <20 Gy in patients <4 years old.
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Affiliation(s)
- Sarah A Milgrom
- Department of Radiation Oncology, University of Colorado, Aurora, Colorado
| | - Peter van Luijk
- Department of Radiation Oncology, University Medical Center Groningen, University of Groningen, Groningen, Netherlands
| | - Ramiro Pino
- Department of Radiation Oncology, Houston Methodist Hospital, Houston, Texas
| | - Cecile M Ronckers
- Princess Máxima Centrum for Pediatric Oncology, Utrecht, Netherlands; Institute of Biostatistics and Registry Research, Brandenburg Medical School-Theodor Fontane, Neuruppin, Germany
| | - Leontien C Kremer
- Institute of Biostatistics and Registry Research, Brandenburg Medical School-Theodor Fontane, Neuruppin, Germany; UMC Amsterdam, Location AMC, Department of Pediatrics, Amsterdam, Netherlands
| | - Paul W Gidley
- Department of Head and Neck Surgery, MD Anderson Cancer Center, Houston, Texas
| | - David R Grosshans
- Department of Radiation Oncology, MD Anderson Cancer Center, Houston, Texas
| | - Siddhartha Laskar
- Department of Radiation Oncgqtology, Tata Memorial Hospital, Mumbai, India
| | - M Fatih Okcu
- Department of Pediatrics, Baylor College of Medicine, Houston, Texas
| | - Louis S Constine
- Department of Radiation Oncology, University of Rochester, Rochester, New York
| | - Arnold C Paulino
- Department of Radiation Oncology, MD Anderson Cancer Center, Houston, Texas.
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Foster-Thomas E, Aznar M, Brennan B, O’Malley L. Proton beam therapy and dentofacial development in paediatric cancer patients: A scoping review. Int J Part Ther 2024; 12:100107. [PMID: 38952615 PMCID: PMC11215291 DOI: 10.1016/j.ijpt.2024.100107] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2024] [Revised: 05/24/2024] [Accepted: 05/29/2024] [Indexed: 07/03/2024] Open
Abstract
Purpose It is known that radiation to dentofacial structures during childhood can lead to developmental disturbances. However, this appears to be a relatively subordinated research subject. For this reason, this review aims to establish the current evidence base on the effect of PBT on dentofacial development in paediatric patients treated for cancer in the head and neck region. Materials and methods A comprehensive search was undertaken to identify both published and unpublished studies or reports. A single reviewer completed initial screening of abstracts; 2 independent reviewers completed secondary screening and data extraction. A narrative synthesis was then conducted. Results 82 records were screened in total, resulting in 11 included articles. These articles varied in terms of study design and reporting quality. Owing to both poor study reporting and limited patient numbers, it is not possible to determine the effect of cancer diagnosis, chronological age at treatment, radiation dose or treatment modality on the incidence of facial deformation or dental development anomalies. Conclusion Disturbances in dentofacial development are an under-reported toxicity in paediatric cancer survivors treated with PBT to the head and neck. There is a need for more research on dentofacial toxicity reporting, focused on the impact of treatment age, radiation dose, concurrent therapies, and the subsequent impact on quality of life.
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Affiliation(s)
- Emma Foster-Thomas
- NIHR Doctoral Fellow in Restorative Dentistry, Manchester University NHS Foundation Trust, UK
| | - Marianne Aznar
- Adaptive Radiotherapy, University of Manchester, Division of Clinical Cancer Science, School of Medical Sciences, UK
| | - Bernadette Brennan
- Consultant Paediatric Oncologist, Royal Manchester Children’s Hospital, UK
| | - Lucy O’Malley
- Health Services Research, School of Medical Sciences, The University of Manchester, UK
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Davey A, Pan S, Bryce-Atkinson A, Mandeville H, Janssens GO, Kelly SM, Hol M, Tang V, Davies LSC, SIOP-Europe Radiation Oncology Working Group, Aznar M. The need for consensus on delineation and dose constraints of dentofacial structures in paediatric radiotherapy: Outcomes of a SIOP Europe survey. Clin Transl Radiat Oncol 2023; 43:100681. [PMID: 37790584 PMCID: PMC10543782 DOI: 10.1016/j.ctro.2023.100681] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2023] [Accepted: 09/21/2023] [Indexed: 10/05/2023] Open
Abstract
Background and purpose Children receiving radiotherapy for head-and-neck tumours often experience severe dentofacial side effects. Despite this, recommendations for contouring and dose constraints to dentofacial structures are lacking in clinical practice. We report on a survey aiming to understand current practice in contouring and dose assessment to dentofacial structures. Methods A digital survey was distributed to European Society for Paediatric Oncology members of the Radiation Oncology Working Group, and member-affiliated centres in Europe, Australia, and New Zealand. The questions focused on clinical practice and aimed to establish areas for future development. Results Results from 52 paediatric radiotherapy centres across 27 countries are reported. Only 29/52 centres routinely delineated some dentofacial structures, with the most common being the mandible (25 centres), temporo-mandibular joint (22), dentition (13), orbit (10) and maxillary bone (eight). For most bones contoured, an 'As Low As Reasonably Achievable' dose objective was implemented. Only four centres reported age-adapted dose constraints.The largest barrier to clinical implementation of dose constraints was firstly, the lack of contouring guidance (49/52, 94%) and secondly, that delineation is time-consuming (33/52, 63%). Most respondents who routinely contour dentofacial structures (25/27, 90%) agreed a contouring atlas would aid delineation. Conclusion Routine delineation of dentofacial structures is infrequent in paediatric radiotherapy. Based on survey findings, we aim to 1) define a consensus-contouring atlas for dentofacial structures, 2) develop auto-contouring solutions for dentofacial structures to aid clinical implementation, and 3) carry out treatment planning studies to investigate the importance of delineation of these structures for planning optimisation.
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Affiliation(s)
- Angela Davey
- Division of Cancer Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK
| | - Shermaine Pan
- Department of Proton Therapy, The Christie NHS Foundation Trust, Manchester, UK
| | - Abigail Bryce-Atkinson
- Division of Cancer Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK
| | | | - Geert O. Janssens
- Princess Maxima Center for Paediatric Oncology, Utrecht, The Netherlands
- Department of Radiation Oncology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Sarah M. Kelly
- European Society for Paediatric Oncology (SIOP Europe), Clos Chapelle-aux-Champs 30, Brussels, Belgium
- The European Organisation for Research and Treatment of Cancer (EORTC) Headquarters, Avenue E. Mounier 83, Brussels, Belgium
- Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium
| | - Marinka Hol
- Princess Maxima Center for Paediatric Oncology, Utrecht, The Netherlands
- Department of Otorhinolaryngology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Vivian Tang
- Paediatric Radiology, Royal Manchester Children’s Hospital, Manchester, UK
| | | | | | - Marianne Aznar
- Division of Cancer Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK
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Foster-Thomas E, Aznar M, Indelicato D, Pan S, Hwang E, Sitch P, Horner K, Smith E, Gaito S. Late Dental Toxicities After Proton Chemoradiation for Rhabdomyosarcoma: A Pediatric Case Report. Int J Part Ther 2022; 9:50-57. [PMID: 36721482 PMCID: PMC9875822 DOI: 10.14338/ijpt-22-00011.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Accepted: 07/26/2022] [Indexed: 11/17/2022] Open
Abstract
Purpose Radiation therapy is an independent risk factor for adverse sequelae to the oral cavity and dentition in childhood cancer survivors. However, dental toxicities after radiation therapy often are underreported and there are minimal published data on disturbances in tooth development after proton beam therapy (PBT). We present the long-term clinical and radiographic dental findings 8 years after treatment completion for a patient treated with PBT and chemotherapy for rhabdomyosarcoma. Materials and Methods Clinical follow-up data of patients treated with PBT within the Proton Overseas Programme (POP) is stored in a National Database and curated by a dedicated outcomes unit at the Christie NHS PBT center. This case report was identified from the extraction and analysis of data for pediatric head and neck cancer patients in this database for a service evaluation project. Results The permanent dentition in this patient aged 3.5 years at the time of treatment was severely affected with abnormal dental development first observed 3.5 years after treatment completion. PBT delivered mean doses of 30 Gy(RBE = 1.1) to the maxilla and 25.9 Gy(RBE = 1.1) to the mandible. Conclusion Significant dental development abnormalities occurred in this pediatric patient, despite doses in areas being lower than the proposed thresholds in the literature. Improved descriptions of dental toxicities and routine contouring of the maxilla and mandible are needed to correlate dosimetric data. The dose to teeth should be kept as low as reasonably possible in younger patients until the dose thresholds for dental toxicities are known.
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Affiliation(s)
- Emma Foster-Thomas
- Restorative Dentistry, University Dental Hospital of Manchester, Manchester University NHS Foundation Trust, Manchester, UK
| | - Marianne Aznar
- Adaptive Radiotherapy, University of Manchester Division of Clinical Cancer Science, School of Medical Sciences, Manchester, UK
| | - Daniel Indelicato
- Department of Radiation Oncology, University of Florida Health Proton Therapy Institute, Jacksonville, FL, USA
| | - Shermaine Pan
- Clinical Oncology, The Christie NHS Foundation Trust, Manchester, UK
| | - Eunji Hwang
- Department of Radiation Oncology, Crown Princess Mary Cancer Centre, Westmead Hospital, Westmead, Australia
| | - Peter Sitch
- Christie Medical Physics and Engineering, The Christie NHS Foundation Trust, Manchester, UK
| | - Keith Horner
- Dental and Maxillofacial Radiology, University Dental Hospital of Manchester, Manchester University NHS Foundation Trust, Manchester, UK
| | - Ed Smith
- Clinical Oncology, The Christie NHS Foundation Trust, Manchester, UK
| | - Simona Gaito
- The Christie Proton Clinical Outcomes Unit/The University of Manchester Division of Clinical Cancer Science, School of Medical Sciences, Manchester, UK
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Laissue JA, Barré S, Bartzsch S, Blattmann H, Bouchet AM, Djonov VG, Haberthür D, Hlushchuk R, Kaser-Hotz B, Laissue PP, LeDuc G, Reding SO, Serduc R. Tolerance of Normal Rabbit Facial Bones and Teeth to Synchrotron X-Ray Microbeam Irradiation. Radiat Res 2021; 197:233-241. [PMID: 34755190 DOI: 10.1667/rade-21-00032.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Accepted: 09/30/2021] [Indexed: 11/03/2022]
Abstract
Microbeam radiation therapy, an alternative radiosurgical treatment under preclinical investigation, aims to safely treat muzzle tumors in pet animals. This will require data on the largely unknown radiation toxicity of microbeam arrays for bones and teeth. To this end, the muzzle of six young adult New Zealand rabbits was irradiated by a lateral array of microplanar beamlets with peak entrance doses of 200, 330 or 500 Gy. The muzzles were examined 431 days postirradiation by computed microtomographic imaging (micro-CT) ex vivo, and extensive histopathology. The boundaries of the radiation field were identified histologically by microbeam tracks in cartilage and other tissues. There was no radionecrosis of facial bones in any rabbit. Conversely, normal incisor teeth exposed to peak entrance doses of 330 Gy or 500 Gy developed marked caries-like damage, whereas the incisors of the two rabbits exposed to 200 Gy remained unscathed. A single, unidirectional array of microbeams with a peak entrance dose ≤200 Gy (valley dose14 Gy) did not damage normal bone, teeth and soft tissues of the muzzle of normal rabbits longer than one year after irradiation. Because of that, Microbeam radiation therapy of muzzle tumors in pet animals is unlikely to cause sizeable damage to normal teeth, bone and soft tissues, if a single array as used here delivers a limited entrance dose of 200 Gy and a valley dose of ≤14 Gy.
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Affiliation(s)
- Jean Albert Laissue
- Institute of Anatomy, University of Bern, Baltzerstrasse 2, CH -3012 Bern, Switzerland
| | - Sébastien Barré
- Institute of Anatomy, University of Bern, Baltzerstrasse 2, CH -3012 Bern, Switzerland
| | - Stefan Bartzsch
- Department of Radiation Oncology, Klinikum rechts der Isar - TU Munich, Germany
| | - Hans Blattmann
- Niederwiesstrasse 13C, CH-5417 Untersiggenthal, Switzerland
| | - Audrey M Bouchet
- INSERM UA8, "Radiations : Défense, Santé, Environnement," 69008 Lyon, France
| | | | - David Haberthür
- Institute of Anatomy, University of Bern, Baltzerstrasse 2, CH -3012 Bern, Switzerland
| | - Ruslan Hlushchuk
- Institute of Anatomy, University of Bern, Baltzerstrasse 2, CH -3012 Bern, Switzerland
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Gomes-Silva W, Morais-Faria K, Rivera C, Najas GF, Marta GN, da Conceição Vasconcelos KGM, de Andrade Carvalho H, de Castro G, Brandão TB, Epstein JB, Santos-Silva AR. Impact of radiation on tooth loss in patients with head and neck cancer: a retrospective dosimetric-based study. Oral Surg Oral Med Oral Pathol Oral Radiol 2021; 132:409-417. [PMID: 34366269 DOI: 10.1016/j.oooo.2021.06.021] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2020] [Revised: 06/14/2021] [Accepted: 06/30/2021] [Indexed: 11/17/2022]
Abstract
OBJECTIVE To characterize the dental adverse events after head and neck radiation therapy (HNRT) and to investigate the impact of regional radiation dose upon tooth loss outcomes. STUDY DESIGN A retrospective dosimetric-based analysis was conducted to assess dental events affecting post-HNRT extracted teeth and the impact of 3 different radiation doses (<30 Gy, 30-60 Gy, and >60 Gy) upon tooth loss. In addition, post-HNRT extractions outcomes and mean parotid glands dosimetry and salivary changes were analyzed. RESULTS Sixty-six patients who underwent HNRT were included in the analysis. Radiation caries was the most frequent (67.8%) post-HNRT dental adverse event, and maxillary molars ipsilateral to the tumor were lost earlier compared with the others (P < .001). The odds ratio for post-HNRT tooth extraction risk was approximately 3-fold higher for teeth exposed to >60 Gy (confidence interval, 1.56-5.35; P < .001), followed by an increased risk of delayed healing and osteoradionecrosis (ORN) in sites receiving doses above 50 Gy. CONCLUSIONS Radiation caries was the major cause of dental extractions after HNRT, and the dosimetric analysis suggested that a high dose of radiation may negatively impact the dentition of survivors of head and neck cancer, increasing the risk of tooth loss and ORN.
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Affiliation(s)
- Wagner Gomes-Silva
- Dental Oncology Service, Instituto do Câncer do Estado de São Paulo (ICESP), Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil; Oral Diagnosis Department, Piracicaba Dental School, University of Campinas (UNICAMP), Piracicaba, São Paulo, Brazil.
| | - Karina Morais-Faria
- Dental Oncology Service, Instituto do Câncer do Estado de São Paulo (ICESP), Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil; Oral Diagnosis Department, Piracicaba Dental School, University of Campinas (UNICAMP), Piracicaba, São Paulo, Brazil
| | - César Rivera
- Oral Diagnosis Department, Piracicaba Dental School, University of Campinas (UNICAMP), Piracicaba, São Paulo, Brazil
| | - Gabriel Faria Najas
- Division of Radiation Oncology, Department of Radiology and Oncology, Instituto do Câncer do Estado de São Paulo, Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil
| | - Gustavo Nader Marta
- Division of Radiation Oncology, Department of Radiology and Oncology, Instituto do Câncer do Estado de São Paulo, Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil
| | | | - Heloisa de Andrade Carvalho
- Department of Radiation and Oncology, Instituto de Radiologia do Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo (HC-FMUSP), São Paulo, Brazil
| | - Gilberto de Castro
- Division of Clinical Oncology, Department of Radiology and Oncology, Instituto do Câncer do Estado de São Paulo, Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil
| | - Thaís Bianca Brandão
- Dental Oncology Service, Instituto do Câncer do Estado de São Paulo (ICESP), Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil; Oral Diagnosis Department, Piracicaba Dental School, University of Campinas (UNICAMP), Piracicaba, São Paulo, Brazil
| | - Joel B Epstein
- Samuel Oschin Comprehensive Cancer Instititute, Cedars-Sinai Medical Center, Los Angeles, CA, USA; City of Hope Comprehensive Cancer Center, Duarte, CA, USA
| | - Alan Roger Santos-Silva
- Oral Diagnosis Department, Piracicaba Dental School, University of Campinas (UNICAMP), Piracicaba, São Paulo, Brazil
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Marangoni-Lopes L, Rovai-Pavan G, Steiner-Oliveira C, Nobre-dos-Santos M. Susceptibility of gamma-irradiated primary teeth to a cariogenic challenge: an in vitro study. Eur Arch Paediatr Dent 2020; 21:667-672. [DOI: 10.1007/s40368-019-00503-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2019] [Accepted: 12/04/2019] [Indexed: 10/25/2022]
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Fang P, Batra S, Hollander AB, Lin A, Hill-Kayser CE, Levin LM, Mupparapu M, Thompson RF. Development and evaluation of a standardized method and atlas for contouring primary and permanent dentition. Dentomaxillofac Radiol 2015; 44:20150034. [PMID: 25812046 DOI: 10.1259/dmfr.20150034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
OBJECTIVES Radiation toxicity of the dentition may present significant treatment-related morbidity in the paediatric head and neck cancer population. However, clear dose-effect relationships remain undetermined and must be predicated upon accurate structure delineation and dosimetry at the individual tooth level. Radiation oncologists generally have limited familiarity or experience with relevant dental anatomy. METHODS We therefore developed a detailed CT atlas of permanent and primary dentition. After studying this atlas, five radiation oncology clinicians delineated all teeth for each of eight different cases (selected for breadth of dental maturity and anatomical variability). They were asked to record confidence in their contours on a per-tooth basis as well as the duration of time required per case. Contour accuracy and interclinician variability were assessed by Hausdorff distance and Dice similarity coefficient. All analyses were performed using R v. 3.1.1 and the RadOnc v. 1.0.9 package. RESULTS Participating clinicians delineated teeth with varying degrees of completeness and accuracy, stratified primarily by the age of the subject. On a per-tooth basis, delineation of permanent dentition was feasible for incisors, canines, premolars and first molars among all subjects, even at the youngest ages. However, delineation of second and third molars was less consistent, commensurate with approximate timing of tooth development. Within each tooth contour, uncertainty was the greatest at the level of the dental roots. CONCLUSIONS Delineation of individual teeth is feasible and serves as a necessary precursor for dental dose assessment and avoidance. Among the paediatric radiation oncology community in particular, this atlas may serve as a useful tool and reference.
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Affiliation(s)
- P Fang
- 1 Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA, USA
| | - S Batra
- 1 Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA, USA
| | - A B Hollander
- 1 Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA, USA
| | - A Lin
- 1 Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA, USA
| | - C E Hill-Kayser
- 1 Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA, USA
| | - L M Levin
- 2 Department of Oral and Maxillofacial Surgery, University of Pennsylvania, Philadelphia, PA, USA
| | - M Mupparapu
- 3 Department of Oral and Maxillofacial Radiology, University of Pennsylvania, Philadelphia, PA, USA
| | - R F Thompson
- 1 Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA, USA
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Chin AL, Lin A, Anamalayil S, Teo BKK. Feasibility and limitations of bulk density assignment in MRI for head and neck IMRT treatment planning. J Appl Clin Med Phys 2014; 15:4851. [PMID: 25207571 PMCID: PMC5711084 DOI: 10.1120/jacmp.v15i5.4851] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2013] [Revised: 05/08/2014] [Accepted: 04/30/2014] [Indexed: 12/04/2022] Open
Abstract
Head and neck cancers centered at the base of skull are better visualized on MRI than on CT. The purpose of this investigation was to investigate the accuracy of bulk density assignment in head and neck intensity‐modulated radiation therapy (IMRT) treatment plan optimization. Our study investigates dose calculation differences between density‐assigned MRI and CT, and identifies potential limitations related to dental implants and MRI geometrical distortion in the framework of MRI‐only‐based treatment planning. Bulk density assignment was performed and applied onto MRI to generate three MRI image sets with increasing levels of heterogeneity for seven patients: 1) MRIW: all water‐equivalent; 2) MRIW + B: included bone with density of 1.53 g/cm3; and 3) MRIW + B + A: included bone and air. Using identical planning and optimization parameters, MRI‐based IMRT plans were generated and compared to corresponding, forward‐calculated, CT‐based plans on the basis of target coverage, isodose distributions, and dose‐volume histograms (DVHs). Phantom studies were performed to assess the magnitude and spatial dependence of MRI geometrical distortion. MRIW‐based dose calculations overestimated target coverage by 16.1%. Segmentation of bone reduced differences to within 2% of the coverage area on the CT‐based plan. Further segmentation of air improved conformity near air–tissue interfaces. Dental artifacts caused substantial target coverage overestimation even on MRIW + B + A. Geometrical distortion was less than 1 mm in an imaging volume 20 × 20 × 20 cm3 around scanner isocenter, but up to 4 mm at 17 cm lateral to isocenter. Bulk density assignment in the framework of MRI‐only IMRT head and neck treatment planning is a feasible method with certain limitations. Bone and teeth account for the majority of density heterogeneity effects. While soft tissue is well visualized on MRI compared to CT, dental implants may not be visible on MRI and must be identified by other means and assigned appropriate density for accurate dose calculation. Far off‐center geometrical distortion of the body contour near the shoulder region is a potential source of dose calculation inaccuracy. PACS numbers: 87.61.‐c, 87.55.‐D
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