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Assessing of a Radiation Therapy Session's Duration at the Stage of Pre-Radiation Preparation
M.N. Piatkevich, E.V. Titovich
N.N. Alexandrov National Cancer Centre of Belarus, Lesnoy 223040, Minsk District, Belarus
Received 30.11.2021
Accepted for publication 02.02.2022
Abstract
The treatment planning process includes a review of the radiation treatment plan which leads to a decision on the patient's treatment technique. The scope of this study was to create a mathematical model for calculating of a radiation therapy session duration during the pre-radiation planning stage.
For dosimetric planning of radiation treatment the authors provided a formula and an algorithm for determining of a patient's irradiation session duration. Radiation therapy session parameters such as radiation technique, number of monitor units, characteristics of radiotherapy equipment, number of radiation fields, radiation field parameters (angles of rotation of the radiotherapy coach, collimator, gantry), presence/absence of dose-modulating devices, dose rate, and duration of patient position verification procedures have all been taken into account during the development of software. The developed application explains how to define typical timing characteristics for various items as well as how to select a template from a built-in drop-down menu. If the dosimetric plan does not match for one of the templates, the program provides a space for defining of all parameters manually.
The anticipated deviations of the true indicators from the expected indicators of the duration of the radiation therapy session were assessed. A total of 300 cases have been completely measured, with 100 cases studied for each irradiation technique (IMRT, VMAT, 3D). The maximum detection confidence value for the 3DCRT irradiation technique is 2.3 %, while the deviation for the IMRT and VMAT irradiation techniques is less than 1 %. The magnitude and degree of the deviation of the measured value from the expected one for a variety of characteristics and features have been revealed to depend on the actions of the personnel.
The program developed allows medical physicists to analyze the timing parameters of the specified dosimetric planning methodologies directly on the treatment planning workstation. Evaluation of the duration of a radiation therapy session during the treatment planning stage, selection of various radiation treatment modalities, and consideration of the characteristics of the radiation session in each clinical case are available for analysis and further justified action.
Keywords: treatment session, linear accelerator, radiation therapy, timing. DOI: 10.21122/2220-9506-2022-13-1-68-73
Адрес для переписки:
Петкевич М.Н.
РНПЦ онкологии и медицинской радиологии имени Н.Н. Александрова,
агрогородок Лесной 223040, Минский район, Беларусь e-mail: maxpetkevichn@gmail.com
Address for correspondence:
Piatkevich M.N.
N.N. Alexandrov National Cancer Centre of Belarus, Lesnoy 223040, Minsk District, Belarus e-mail: maxpetkevichn@gmail.com
Для цитирования:
M.N. Piatkevich, E.V. Titovich.
Assessing of a Radiation Therapy Session's Duration
at the Stage of Pre-Radiation Preparation.
Приборы и методы измерений.
2022. - Т. 13, № 1. - С. 68-73.
DOI: 10.21122/2220-9506-2022-13-1-68-73
For citation:
M.N. Piatkevich, E.V. Titovich.
Assessing of a Radiation Therapy Session's Duration
at the Stage of Pre-Radiation Preparation.
Devices and Methods of Measurements.
2022, vol. 13, no. 1, pp. 68-73.
DOI: 10.21122/2220-9506-2022-13-1-68-73
Оценка продолжительности сеанса лучевой терапии на этапе предлучевой подготовки
М.Н. Петкевич, Е.В. Титович
РНПЦ онкологии и медицинской радиологии имени Н.Н. Александрова, агрогородок Лесной 223040, Минский район, Беларусь
Поступила 30.11.2021 Принята к печати 02.02.2022
Анализ плана лучевого лечения является неотъемлемой частью процесса предлучевой подготовки, в результате которого принимается решение о методике лечения пациента. Целью данной работы являлась разработка математической модели определения продолжительности сеанса лучевой терапии на этапе предлучевой подготовки.
Авторами предложены формула и алгоритм расчёта продолжительности сеанса облучения пациента на этапе дозиметрического планирования лучевого лечения. Разработано программное обеспечение расчёта продолжительности сеанса облучения, учитывающее значения всех параметров сеанса лучевой терапии: методику облучения, количество мониторных единиц, характеристики радиотерапевтического оборудования, количество радиационных полей, параметры полей облучения (углы поворота радиотерапевтического стола, коллиматора, штатива аппарата), наличие/ отсутствие дозомодулирующих устройств, мощность дозы, продолжительность верификации положения пациента. В программе предусмотрена установка стандартных параметров плана облучения для различных локализаций и методик путём выбора конкретного шаблона из выпадающего списка. В случае, если дозиметрический план не соответствует ни одному из шаблонов, в программе предусмотрен ввод параметров плана вручную.
Произведена оценка отклонений, рассчитываемых разработанной программой значений продолжительности сеанса лучевой терапии от истинных значений. Измерения проведены для 300 случаев: исследованы по 100 случаев для каждой методики облучения (IMRT, VMAT, 3D). Максимальное выявленное отклонение рассчитанного значения от истинного составило 2,3 % для методики облучения 3DCRT, для методик облучения IMRT и VMAT отклонение составило менее 1 %. Выявлено, что с увеличением количества процедур, напрямую связанных с действиями персонала, увеличивается и величина отклонения рассчитанного значения с измеренным.
Разработанное программное обеспечение позволяет оценивать временные параметры выбранных подходов дозиметрического планирования на рабочем месте медицинского физика. Оценка длительности сеанса лучевой терапии на этапе предлучевой подготовки способствует выбору оптимальной методики лучевого лечения с учётом индивидуальных параметров сеанса облучения в каждом конкретном клиническом случае.
Ключевые слова: сеанс облучения, линейный ускоритель, лучевая терапия, временные характеристики.
DOI: 10.21122/2220-9506-2022-13-1-68-73
Адрес для переписки:
Петкевич М.Н.
РНПЦ онкологии и медицинской радиологии имени Н.Н. Александрова,
агрогородок Лесной 223040, Минский район, Беларусь e-mail: maxpetkevichn@gmail.com
Для цитирования: For citation:
M.N. Piatkevich, E.V. Titovich. M.N. Piatkevich, E.V. Titovich.
Assessing of a Radiation Therapy Session's Duration Assessing of a Radiation Therapy Session's Duration
at the Stage of Pre-Radiation Preparation. at the Stage of Pre-Radiation Preparation.
Приборы и методы измерений. Devices and Methods of Measurements.
2022. - Т. 13, № 1. - С. 68-73. 2022, vol. 13, no. 1, pp. 68-73.
DOI: 10.21122/2220-9506-2022-13-1-68-73 DOI: 10.21122/2220-9506-2022-13-1-68-73
Address for correspondence:
Piatkevich M.N.
N.N. Alexandrov National Cancer Centre of Belarus, Lesnoy 223040, Minsk District, Belarus e-mail: maxpetkevichn@gmail.com
Introduction
Modern radiation therapy is not complete without the use of high-performance computing facilities [1, 2]. Thanks to the development of computer technology, modern dosimetric planning systems make it possible to model structures within an anatomical object, radiation targets and dose distributions, and to estimate their dose. Over the past decade, computer planning systems have been repeatedly improved by introducing of new components into their structure which make it possible to use a significant amount of input data at the stage of pre-radiation preparation of a patient in the generation of an irradiation plan [3]. Analysis of the radiation treatment plan is an integral part of the pre-radiation preparation process, on the basis of which a decision is made including of the patient's treatment method [4-7]. It is important to assess the parameters influencing the quality of the dosimetry plan since the safety and effectiveness of the medical care provided to the patient depends on it [8-9]. Nowadays the process of determining of a radiation therapy session duration at the stage of pre-radiation preparation is difficult [10]. The authors did not identify methods and approaches to determine of a radiation therapy session duration at the stage of evaluating of a radiation treatment plan, published in printed publications. It should be noted that the possibility of assessing of a radiation therapy session duration at the stage of pre-radiation preparation will make it possible to choose the optimal radiation therapy technique taking into account the individual parameters of the radiation session in each specific clinical case.
In this regard, the purpose of this work is to develop a mathematical model for determining of a radiation therapy session duration at the stage of pre-radiation preparation.
Mathematical model of irradiation session
In [11] the authors established the time characteristics of the radiation session components, which have a dominant influence on its duration and proposed an algorithm that allows determining the duration of radiation treatment of cancer patients depending on the use of different radiation therapy techniques and tumor localizations. In [12] the authors established the numerical values of dominant components of radiation therapy session for each of the most used in clinical practice of the Department
of Radiation Therapy of N.N. Alexandrov National Cancer Centre of Belarus.
Based on the results obtained in [11] and [12], the components of a radiation therapy session that directly influence its duration are: laying the patient and centering in the position prescribed for irradiation, setting the required mechanical parameters of the gas pedal under visual control from the procedure room, setting/removing wedge filters, time spent on the process of preparation for irradiation generation, verification of the patient position, initializing the gas pedal with irradiation parameters, relevant.
Let us introduce the notation of time parameters for each of the procedures, which will be taken into account when determining the total time of the radiation therapy session:
Tses - radiation therapy time; tpl - laying the patient and centering in the prescribed position for the irradiation;
tset - setting the necessary mechanical parameters of the gas pedal under visual control from the procedure room;
tfi - installation/removal of wedge filters; tturn - turning on the irradiation; tver - patient position verification; tinit - initialization of the gas pedal with irradiation parameters relevant to the second and subsequent treatment fields;
ttbl - rotation of the therapeutic table; tgan - rotation of the tripod; tcoll - rotation of the collimator; tirr f - time of irradiation of one irradiation field; tirr - time of irradiation of the patient; tfin - patient out of the treatment room. To describe a mathematical model of a radiation therapy session, the authors proposed the following formula (1):
(1)
Tses = tpl + tset + tßi + tturn + tver + tinit _ 1 + +4rr _ f 1 + tfil _ 2 + tturn _ 2 + tinit _ 2 + +ttbl _ 2 + tgan _ 2 + l-coll _ 2 + tirr _ f 2 + — + +tfil _ n + tturn _ n + tinit _ n + hbl _ n + +tgan _ n + -coII _ n + tirr _ fn + tfin •
Using the proposed formula, it is possible to estimate the radiation therapy session time at the stage of dosimetric treatment planning.
Software
To estimate the duration of the irradiation session in accordance with the chosen approach of dosimetric planning at a medical physicist's workplace, a computer program was developed, the mathematical algorithm of which is based on the proposed formula (1). Figure 1 shows the interface of the program for calculating the duration of the irradiation session according to the three-dimensional conformai irradiation technique (3D CRT).
The program algorithm is shown in Figure 2.
Calculation of the duration of the irradiation session at » «
Fields
Templates Machine PiclH 1
3D prostate T | Trilogy ix j w\ Couch Rotation [deg] Collimator Rotation [deg] 0
0 Enter parameters manually 0
Number of fields 2 Gantry Rotation [di MU ig] 0 185
Technique 0 3D □ IMRT □ VMAT □ Wedge Field 2
Dose Rate 300 MU/min Couch Rotation [de ■g] 0
0 Patient position verification Collimator Rotation [deg] Gantry Rotation [deg] 90 180
calculation 8 min 11 sec MU □ Wedge 191 M
Figure 1 - Interface of the computer program for calcula ting the duration of an illumination session
NO
Number of fields (N)
\ r
Creation of N irradiation fields in the
"Fields " menu
\ t
Select of irradiation technique
t
Selecting a template
\ /
Loading template parameters
\ r
Entering MU for all fields
Entering parameters for N fields:
- Couch Rotation, deg
- Collimator Rotation, deg
- Gantry Rotation, deg -MU
- Wedge
Entering parameters for N fields:
- Couch Rotation, deg
- Collimator Rotation, deg
- Gantry Rotation, deg -MU
Entering parameters for N fields:
- Couch Rotation, deg
- Collimator Rotation, deg
- Gantry Rotation (Start and Stop Angle), deg
-MU
Figure 2 - Program algorithm
The computer program provides for setting standard parameters of the irradiation plan for different localizations and techniques by selecting a specific template from the drop-down list. After selecting a particular template, the parameters of the radiation treatment plan are automatically loaded, and then the number of monitor units for each radiation field must be entered. If the dosimetric plan does not correspond to any of the templates, the program provides the possibility to enter the plan parameters manually. In this case it is necessary to enter the required number of radiation fields in the area "Number of fields" and select the irradiation technique (3D, IMRT or VMAT), then enter the parameters of each field in the corresponding cell: table rotation angle, collima-tor rotation angle, tripod rotation angle, number of monitor units (MU) and presence of wedge-shaped filter if it is provided by the patient's radiotherapy plan. Then you select the model of the radiation therapy unit in the "Machine" menu, and then the necessary parameters of the selected unit are automatically loaded. Then in the "Dose Rate" area the dose
rate is specified. In case of implementing a radiation treatment plan with patient position verification the checkbox "Patient position verification" is set. After setting all parameters of the radiation treatment plan, the duration of the radiation session "Calculate" is calculated, the result of the calculation is displayed in the corresponding cell.
Research results
The authors analyzed the data obtained by applying the developed software to determine the duration of the radiation session. The analysis was carried out by comparing the data obtained using the developed computer program with the true data measured in real time during the radiation therapy session. Measurements were made for 300 cases: 100 cases for each irradiation technique (IMRT, VMAT, 3D) were studied. Figure 3 shows a graph showing the effect of the duration of the radiation session on the deviation of the calculated values from the true values.
Figure 3 - Influence of irradiation session duration on the deviation of calculated values from true values for 3DCRT, IMRT and VMAT irradiation techniques
The maximum detected deviation of the calculated value from the true value was 2.3 % for the 3DCRT irradiation technique; for the IMRT and VMAT irradiation techniques the deviation was less than 1 %. The average deviation was 1.3 % for the 3DCRT technique and 0.4 % for IMRT and VMAT. It was found that with an increase in the number of procedures directly related to the actions of the personnel, the deviation of the calculated value from the measured one also increases. This is due to the
different physical characteristics of the person involved in the implementation of the radiation therapy session.
Conclusion
The authors have proposed a formula for calculating the time of an irradiation session of patients at the stage of dosimetric planning of radiation treatment. Using this formula makes it possible to take
into account the time spent on procedures that make up a radiation therapy session, and thus minimize the probability of an error in the planned dose delivery related to the mobility of internal organs and biological processes of the irradiated biological object. Application of the approach focused on reducing the time cost of the radiation therapy session will also increase the throughput of radiotherapy equipment and in some cases reduce its wear and tear.
An algorithm for calculating the duration of a radiotherapy session is proposed. Software is developed which allows to estimate the time parameters of the selected dosimetric planning approaches at the medical physicist's workplace.
Deviations of the calculated values of radiation therapy session duration by means of the developed program from the actual values were evaluated. The maximum deviation of the calculated value from the true value is 2.3 % for 3DCRT technique, for IMRT and VMAT techniques the deviation was less than 1 %. The average deviation for the 3DCRT technique was 1.3 %, and for the IMRT and VMAT techniques was 0.4 %.
References
1. Chernayev A.P., Lykova E.N., Popodko A.I. Me-decynskoe oborudovanie v sovremennoi luchevoi terapii [Medical equipment in modern radiation therapy]. Moscow, OOP fizicheskogo fakulteta MGU, 2019, 101 p.
2. Selecting Megavoltage Treatment Technologies in External Beam Radiotherapy. International Atomic Energy Agency, ISSN 2074-7667, 2022, no. 17, 43 p.
3. Khan F.M. The physics of radiation therapy, 4th ed. Philadelphia, Lippincott Williams & Wilkins, 2010, 531 p.
4. Trufanov G.E. Luchevaay terapia. Tom 2 [Radiation therapy, part 2]. Moscow, GEOTAR-Media, 2010, 192 p.
5. Fotina I.E. Osnovy luchevoi terapii. Distantsion-naya radioterapiya [Fundamentals of Radiation Therapy. External beam therapy]. Tomsk, Izdatelstvo Tomskogo politekhnicheskogo universiteta, 2010, 104 p.
6. Tepper Joel E., Foote Robert L., Michals-ki Jeff M. [Clinical radiation oncology. Fifth edition]. Elsevier Philadelphia, PA, 2021, 1586 p.
7. Ovchinikov V.A., Uglyanitsa K.N., Volkov V.N. Sovremennye metody luchevogo lecheniya onkolo-gicheskikh bolnykh [Modern radiation treatment methods for cancer patients]. Zhurnal GrSMU [Journal of Grodno State Medical University], 2010, no. 1, pp. 93-97 (in Russian).
8. Xia Ping, Godley Andrew (eds.) Strategies for radiation therapy treatment planning. Demos Medical Publishing, 2019, 319 p.
9. Khan F.M., Gibbons J.P. Khan's the physics of radiation therapy, 5th ed. Philadelphia, Wolters Kluwer, 2014, 584 p.
10. Lykova E.N. Uzarova K.A. Vvedenie v plani-rovanie luchevoi terapii puchkami tormoznykh foto-nov [Introduction to Beam Radiation Therapy Planning bremsstrahlung photons]. Moscow, OOP fizicheskogo fakulteta MGU, 2019, 108 p.
11. Titovich E.V., Patsiapalau P.A., Piatkevich M.N., Kiselev M.G. [The algorithm for determining timing of radiotherapy session components for different methods of oncology patients irradiation at the stage of radiotherapy planning]. Pribory i metody izmerenii [Devices and Methods of Measurements], 2017, vol. 8, no. 1, pp. 73-80 (in Russian).
DOI: 10.21122/2220-9506-2017-8-1-73-80
12. Titovich E.V, Piatkevich M.N., Makarava N.I. [Methodology of defining of the radiation therapy components for various methods of patients' treatingusing medical linear accelerators and gamma-therapeutic devices]. Pribory i metody izmerenii [Devices and Methods of Measurements], 2020, vol. 11, no. 4, pp. 289-287.
DOI: 10.21122/2220-9506-2020-11-4-289-287
