Automated algorithm for calculation of setup corrections and planning target volume margins for offline image‐guided radiotherapy protocols

There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.

Abstract

Purpose

Each radiotherapy center should have a site‐specific planning target volume (PTV) margins and image‐guided (IG) radiotherapy (IGRT) correction protocols to compensate for the geometric errors that can occur during treatment. This study developed an automated algorithm for the calculation and evaluation of these parameters from cone beam computed tomography (CBCT)‐based IG‐intensity modulated radiotherapy (IG‐IMRT) treatment.

Methods and materials

A MATLAB algorithm was developed to extract the setup errors in three translational directions ( x, y, and z) from the data logged by the CBCT system during treatment delivery. The algorithm also calculates the resulted population setup error and PTV margin based on the van Herk margin recipe and subsequently estimates their respective values for no action level (NAL) and extended no action level (eNAL) offline correction protocols. The algorithm was tested on 25 head and neck cancer (HNC) patients treated using IG‐IMRT.

Results

The algorithms calculated that the HNC patients require a PTV margin of 3.1, 2.7, and 3.2 mm in the x‐, y‐, and z‐direction, respectively, without IGRT. The margin can be reduced to 2.0, 2.2, and 3.0 mm in the x‐, y‐, and z‐direction, respectively, with NAL and 1.6, 1.7, and 2.2 mm in the x‐, y‐, and z‐direction, respectively, with eNAL protocol. The results obtained were verified to be the same with the margins calculated using an Excel spreadsheet. The algorithm calculates the weekly offline setup error correction values automatically and reduces the risk of input data error observed in the spreadsheet.

Conclusions

In conclusion, the algorithm provides an automated method for optimization and reduction of PTV margin using logged setup errors from CBCT‐based IGRT.

Related collections

Most cited references 45

Record: found
Abstract: found
Article: not found

Errors and margins in radiotherapy.

Marcel van Herk (2004)

Clinical radiotherapy procedures aim at high accuracy. However, there are many error sources that act during treatment preparation and execution that limit the accuracy. As a consequence, a safety margin is required to ensure that the planned dose is actually delivered to the target for (almost) all patients. Before treatment planning, a planning computed tomography scan is made. In particular, motion of skin with respect to the internal anatomy limits the reproducibility of this step, introducing a systematic setup error. The second important error source is organ motion. The tumor is imaged in an arbitrary position, leading to a systematic organ motion error. The image may also be distorted because of the interference of the scanning process and organ motion. A further systematic error introduced during treatment planning is caused by the delineation process. During treatment, the most important errors are setup error and organ motion leading to day-to-day variations. There are many ways to define the margins required for these errors. In this article, an overview is given of errors in radiotherapy and margin recipes, based on physical and biological considerations. Respiration motion is treated separately.

0 comments Cited 286 times – based on 0 reviews      Review now

Bookmark

Record: found
Abstract: found
Article: not found

The probability of correct target dosage: dose-population histograms for deriving treatment margins in radiotherapy.

M van Herk, P Remeijer, C. Rasch … (2000)

To provide an analytical description of the effect of random and systematic geometrical deviations on the target dose in radiotherapy and to derive margin rules. The cumulative dose distribution delivered to the clinical target volume (CTV) is expressed analytically. Geometrical deviations are separated into treatment execution (random) and treatment preparation (systematic) variations. The analysis relates each possible preparation (systematic) error to the dose distribution over the CTV and allows computation of the probability distribution of, for instance, the minimum dose delivered to the CTV. The probability distributions of the cumulative dose over a population of patients are called dose-population histograms in short. Large execution (random) variations lead to CTV underdosage for a large number of patients, while the same level of preparation (systematic) errors leads to a much larger underdosage for some of the patients. A single point on the histogram gives a simple "margin recipe." For example, to ensure a minimum dose to the CTV of 95% for 90% of the patients, a margin between CTV and planning target volume (PTV) is required of 2.5 times the total standard deviation (SD) of preparation (systematic) errors (Sigma) plus 1.64 times the total SD of execution (random) errors (sigma') combined with the penumbra width, minus 1.64 times the SD describing the penumbra width (sigma(p)). For a sigma(p) of 3.2 mm, this recipe can be simplified to 2.5 Sigma + 0.7 sigma'. Because this margin excludes rotational errors and shape deviations, it must be considered as a lower limit for safe radiotherapy. Dose-population histograms provide insight into the effects of geometrical deviations on a population of patients. Using a dose-probability based approach, simple algorithms for choosing margins were derived.

0 comments Cited 234 times – based on 0 reviews      Review now

Bookmark

Record: found
Abstract: found
Article: not found

Quantification of volumetric and geometric changes occurring during fractionated radiotherapy for head-and-neck cancer using an integrated CT/linear accelerator system.

Clifford K S Chao, Jennifer C O'Daniel, Katherine L. Tucker … (2004)

Many patients receiving fractionated radiotherapy (RT) for head-and-neck cancer have marked anatomic changes during their course of treatment, including shrinking of the primary tumor or nodal masses, resolving postoperative changes/edema, and changes in overall body habitus/weight loss. We conducted a pilot study to quantify the magnitude of these anatomic changes with systematic CT imaging. Fourteen assessable patients were enrolled in this pilot study. Eligible patients had to have a pathologic diagnosis of head-and-neck cancer, be treated with definitive external beam RT, and had have gross primary and/or cervical nodal disease measuring at least 4 cm in maximal diameter. All patients were treated using a new commercial integrated CT-linear accelerator system (EXaCT) that allows CT imaging at the daily RT sessions while the patient remains immobilized in the treatment position. CT scans were acquired three times weekly during the entire course of RT, and both gross tumor volumes (GTVs: primary tumor and involved lymph nodes) and normal tissues (parotid glands, spinal canal, mandible, and external contour) were manually contoured on every axial slice. Volumetric and positional changes relative to a central bony reference (the center of mass of the C2 vertebral body) were determined for each structure. Gross tumor volumes decreased throughout the course of fractionated RT, at a median rate of 0.2 cm(3) per treatment day (range, 0.01-1.95 cm(3)/d). In terms of the percentage of the initial volume, the GTVs decreased at a median rate of 1.8%/treatment day (range, 0.2-3.1%/d). On the last day of treatment, this corresponded to a median total relative loss of 69.5% of the initial GTV (range, 9.9-91.9%). In addition, the center of the mass of shrinking tumors changed position with time, indicating that GTV loss was frequently asymmetric. At treatment completion, the median center of the mass displacement (after corrections for daily setup variation) was 3.3 mm (range, 0-17.3 mm). Parotid glands also decreased in volume (median, 0.19 cm(3)/d range, 0.04-0.84 cm(3)/d), and generally shifted medially (median, 3.1 mm; range, 0-9.9 mm) with time. This medial displacement of the parotid glands correlated highly with the weight loss that occurred during treatment. Measurable anatomic changes occurred throughout fractionated external beam RT for head-and-neck cancers. These changes in the external contour, shape, and location of the target and critical structures appeared to be significant during the second half of treatment (after 3-4 weeks of treatment) and could have potential dosimetric impact when highly conformal treatment techniques are used. These data may, therefore, be useful in the development of an adaptive RT scheme (periodic adjustment of the conformal treatment plan) that takes into account such treatment-related anatomic changes. In theory, such a strategy would maximize the therapeutic ratio of RT.

0 comments Cited 147 times – based on 0 reviews      Review now

Bookmark

All references

Author and article information

Contributors

Hafiz Mohd Zin:

ORCID: https://orcid.org/0000-0002-5679-7210

hafiz.zin@physics.org

Journal

Journal ID (nlm-ta): J Appl Clin Med Phys

Journal ID (iso-abbrev): J Appl Clin Med Phys

Journal ID (doi): 10.1002/(ISSN)1526-9914

Journal ID (publisher-id): ACM2

Title: Journal of Applied Clinical Medical Physics

Publisher: John Wiley and Sons Inc. (Hoboken )

ISSN (Electronic): 1526-9914

Publication date (Electronic): 09 June 2021

Publication date Collection: July 2021

Volume: 22

Issue: 7 ( doiID: 10.1002/acm2.v22.7 )

Pages: 137-146

Affiliations

[ ¹ ] Advanced Medical and Dental Institute (AMDI) Universiti Sains Malaysia Kepala Batas 13200 Malaysia

[ ² ] Department of Medical Radiography, Faculty of Allied Health Sciences, College of Medical Sciences University of Maiduguri Maiduguri Nigeria

Author notes

[*] [* ] Author to whom correspondence should be addressed. Hafiz Mohd Zin

E‐mail: hafiz.zin@ 123456physics.org

Author information

Auwal Abubakar https://orcid.org/0000-0002-4859-2928

Hafiz Mohd Zin https://orcid.org/0000-0002-5679-7210

Article

Publisher ID: ACM213291

DOI: 10.1002/acm2.13291

PMC ID: 8292705

PubMed ID: 34109736

SO-VID: d0ab1162-d447-468d-a3c0-be9b05ddf696

License:

This is an open access article under the terms of the http://creativecommons.org/licenses/by/4.0/ License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

History

Date revision received : 28 April 2021

Date received : 31 January 2021

Date accepted : 04 May 2021

Page count

Figures: 6, Tables: 0, Pages: 10, Words: 5905

Funding

Funded by: Universiti Sains Malaysia (University of Science, Malaysia) , doi 10.13039/501100004595;

Award ID: 304.CIPPT.6316519

Funded by: Nigeria Ministry of Education

Custom metadata

source-schema-version-number 2.0

cover-date July 2021

details-of-publishers-convertor Converter:WILEY_ML3GV2_TO_JATSPMC version:6.0.4 mode:remove_FC converted:21.07.2021

Keywords: automation,cbct,igrt offline correction protocol,ptv margin,setup error

Data availability:

Keywords: automation, cbct, igrt offline correction protocol, ptv margin, setup error

Automated algorithm for calculation of setup corrections and planning target volume margins for offline image‐guided radiotherapy protocols

Read this article at

Abstract

Purpose

Methods and materials

Results

Conclusions

Related collections

International Journal of Applied Technology in Medical Sciences

Most cited references 45

Errors and margins in radiotherapy.

The probability of correct target dosage: dose-population histograms for deriving treatment margins in radiotherapy.

Quantification of volumetric and geometric changes occurring during fractionated radiotherapy for head-and-neck cancer using an integrated CT/linear accelerator system.

Author and article information

Contributors

Journal

Affiliations

Author notes

Author information

Article

History

Page count

Funding

Categories

Custom metadata

Comments

Comment on this article

Similar content 40

Cited by 2

Most referenced authors 384