Advanced

Ensuring the intended volume is given the intended absorbed dose in radiotherapy: Managing geometric variations and treatment hazards

Holmberg, Ola LU (2004)
Abstract (Swedish)
Popular Abstract in Swedish

Strålbehandling har sedan länge visat sig vara en bra metod för att behandla patienter med cancer. Den nya teknik som har introducerats under de senaste åren har möjliggjort ökade stråldoser till än mer begränsade volymer. Samtidigt innebär detta att ökade krav ställs på att man försäkrar sig om att den volym man bestrålar är den volym som innehåller tumörceller och att inga misstag görs när man förbereder behandlingen.



I denna avhandling undersöks hur man praktiskt skall gå tillväga för att försäkra sig om:



(1) en stor sannolikhet för att tumören befinner sig i strålfältet vid varje behandlingstillfälle



(2) en liten sannolikhet för att man... (More)
Popular Abstract in Swedish

Strålbehandling har sedan länge visat sig vara en bra metod för att behandla patienter med cancer. Den nya teknik som har introducerats under de senaste åren har möjliggjort ökade stråldoser till än mer begränsade volymer. Samtidigt innebär detta att ökade krav ställs på att man försäkrar sig om att den volym man bestrålar är den volym som innehåller tumörceller och att inga misstag görs när man förbereder behandlingen.



I denna avhandling undersöks hur man praktiskt skall gå tillväga för att försäkra sig om:



(1) en stor sannolikhet för att tumören befinner sig i strålfältet vid varje behandlingstillfälle



(2) en liten sannolikhet för att man ska göra något fel då man förbereder behandlingen



Inom strålterapi förekommer ett antal geometriska variationer i tumörposition i förhållande till strålfält. Dessa variationer är en del av terapin och kommer sig av att man behandlar en patient dagligen i flera veckor. Vid varje behandlingstillfälle försöker man positionera patienten med hög noggrannhet för att vara säker på att tumören befinner sig inom strålfältet, men det är alltid en viss variation i positioneringen. Dessutom gör fysiologiska processer som andning och mag- och tarmfunktioner att tumören rör sig. Dessa processer, tillsammans med svårigheten att vara helt säker på vilken som är den korrekta volym som innehåller alla tumörceller, gör att man måste ha vissa marginaler i sitt strålfält. I avhandlingen undersöks geometriska variationer och metoder för att minimera dessa samt återstående marginaler.



I relation till hur man minskar risken för fel vid förberedande av strålbehandling, har förekommande faror kartlagts och kvantifierats. I 3.5% av förberedda behandlingar har fel hittats och åtgärdats innan behandling har påbörjats. Olika metoder som kan kombineras för att få en säker strålbehandling har undersökts. (Less)
Abstract
Methods for ensuring that the intended volume receives the intended absorbed dose in radiotherapy have been investigated. In order to optimise radiation treatment of cancer, geometric variations in the treatment chain need to be controlled. Furthermore, hazards potentially leading to unintended irradiation need to be controlled. While the required methods for optimisation of irradiation are diverse, advances in technology leading to more distinctly defined high dose volumes make the implementation of these methods crucial.



Geometric variations are controlled by (a) knowledge of types and magnitude of variations; (b) minimisation of variations; (c) taking into account remaining variations by creating margins around... (More)
Methods for ensuring that the intended volume receives the intended absorbed dose in radiotherapy have been investigated. In order to optimise radiation treatment of cancer, geometric variations in the treatment chain need to be controlled. Furthermore, hazards potentially leading to unintended irradiation need to be controlled. While the required methods for optimisation of irradiation are diverse, advances in technology leading to more distinctly defined high dose volumes make the implementation of these methods crucial.



Geometric variations are controlled by (a) knowledge of types and magnitude of variations; (b) minimisation of variations; (c) taking into account remaining variations by creating margins around volumes. Set-up variations have been quantified for lung cancer and breast cancer irradiation. Organ motion has also been measured in connection with treatment of lung tumours. While set-up variations are characterised for groups of patients within individual clinics, it is shown that lung tumour motion needs to be measured for the individual patient due to the range of organ positional variation and corresponding impact. Another parameter that has a high impact on the overall accuracy is the delineation variation in the definition of volumes. It is shown that various methods impact on the minimisation of this variation to different degrees. It is also shown that the delineation of clinical target volume (CTV), being different from gross tumour volume (GTV) delineation in that it also can reflect non-biological parameters such as treatment strategy, will call for the recording of CTV delineation strategy in order to capture the required information. Margins should be based on measured values of variations that are combined according to a documented model. A method of enhancing the potential for dose escalation through stratification of margins based on tumour cell density is suggested and analysed.



Hazards in the treatment preparation chain are controlled by (a) identification of hazards in combination with frequency and consequence analysis, leading to (b) a risk estimation and (c) reducing these risks by introducing a multilayered system of preventive measures. Hazards in radiotherapy preparation have been identified together with corresponding frequencies. Mistakes in the calculation and creation of information were found with a frequency of 1-3% of treatment courses, while the corresponding numbers for information transfer was found to be 1-2%. Layers of preventive measures include (1) actions where potential deviations from intended dose and geometry can be found before the first irradiation-fraction of the patient; (2) actions where deviations can be found during or after the treatment course; (3) application of safety-technology; (4) application of safety procedures; and (5) actions where contributing factors such as staffing-levels and structure, training and communication are addressed. A method for monitoring workload in treatment preparation is explored in this context. (Less)
Please use this url to cite or link to this publication:
author
opponent
  • Olsen, Dag Rune, Professor, Det Norske Radiumhospital, Oslo, Norge
organization
publishing date
type
Thesis
publication status
published
subject
keywords
medical instrumentation, tomography, radiology, Clinical physics, safety, risk, hazard, organ motion, set-up, margins, volume definition, radiotherapy, accuracy, Klinisk fysiologi, radiologi, tomografi, medicinsk instrumentering, Radiopharmaceutical technology, Radiofarmaceutisk teknik
pages
168 pages
publisher
Department of Radiation Physics, Lund university
defense location
Diagnostiskt centrums föreläsningssal, plan 2, ingång 44, Universitetssjukhuset MAS, Malmö
defense date
2004-04-28 10:15
ISBN
91-628-6002-X
language
English
LU publication?
yes
id
2b099f43-7523-4bde-b547-2fa8fe77d993 (old id 466920)
date added to LUP
2007-09-07 13:52:02
date last changed
2016-09-19 08:45:03
@phdthesis{2b099f43-7523-4bde-b547-2fa8fe77d993,
  abstract     = {Methods for ensuring that the intended volume receives the intended absorbed dose in radiotherapy have been investigated. In order to optimise radiation treatment of cancer, geometric variations in the treatment chain need to be controlled. Furthermore, hazards potentially leading to unintended irradiation need to be controlled. While the required methods for optimisation of irradiation are diverse, advances in technology leading to more distinctly defined high dose volumes make the implementation of these methods crucial.<br/><br>
<br/><br>
Geometric variations are controlled by (a) knowledge of types and magnitude of variations; (b) minimisation of variations; (c) taking into account remaining variations by creating margins around volumes. Set-up variations have been quantified for lung cancer and breast cancer irradiation. Organ motion has also been measured in connection with treatment of lung tumours. While set-up variations are characterised for groups of patients within individual clinics, it is shown that lung tumour motion needs to be measured for the individual patient due to the range of organ positional variation and corresponding impact. Another parameter that has a high impact on the overall accuracy is the delineation variation in the definition of volumes. It is shown that various methods impact on the minimisation of this variation to different degrees. It is also shown that the delineation of clinical target volume (CTV), being different from gross tumour volume (GTV) delineation in that it also can reflect non-biological parameters such as treatment strategy, will call for the recording of CTV delineation strategy in order to capture the required information. Margins should be based on measured values of variations that are combined according to a documented model. A method of enhancing the potential for dose escalation through stratification of margins based on tumour cell density is suggested and analysed.<br/><br>
<br/><br>
Hazards in the treatment preparation chain are controlled by (a) identification of hazards in combination with frequency and consequence analysis, leading to (b) a risk estimation and (c) reducing these risks by introducing a multilayered system of preventive measures. Hazards in radiotherapy preparation have been identified together with corresponding frequencies. Mistakes in the calculation and creation of information were found with a frequency of 1-3% of treatment courses, while the corresponding numbers for information transfer was found to be 1-2%. Layers of preventive measures include (1) actions where potential deviations from intended dose and geometry can be found before the first irradiation-fraction of the patient; (2) actions where deviations can be found during or after the treatment course; (3) application of safety-technology; (4) application of safety procedures; and (5) actions where contributing factors such as staffing-levels and structure, training and communication are addressed. A method for monitoring workload in treatment preparation is explored in this context.},
  author       = {Holmberg, Ola},
  isbn         = {91-628-6002-X},
  keyword      = {medical instrumentation,tomography,radiology,Clinical physics,safety,risk,hazard,organ motion,set-up,margins,volume definition,radiotherapy,accuracy,Klinisk fysiologi,radiologi,tomografi,medicinsk instrumentering,Radiopharmaceutical technology,Radiofarmaceutisk teknik},
  language     = {eng},
  pages        = {168},
  publisher    = {Department of Radiation Physics, Lund university},
  school       = {Lund University},
  title        = {Ensuring the intended volume is given the intended absorbed dose in radiotherapy: Managing geometric variations and treatment hazards},
  year         = {2004},
}