Inter-observer comparison of target delineation for MRI-assisted cervical cancer brachytherapy: Application of the GYN GEC-ESTRO recommendations

Self Cite

The purpose of this study was to investigate the concurrent effects of tandem length and bladder volume on dose to pelvic organs at risk (OARs) in HDR intracavitary brachytherapy treatment of cervical cancer. Twenty patients with locally advanced cervical cancer were selected for brachytherapy using Rotterdam applicators. The patients were CT scanned twice with empty and full bladder. Two treatment plans were prepared on each of the image sets. Patients were categorized into two groups; those treated with a tandem length of 4 cm or smaller false(T≤4 cmfalse) and those with tandem length larger than 4 cm (T>4 cm). Only one tandem tip angle of 30° was studied. Dose‐volume histograms (DVHs) of OARs were calculated and compared. Bladder dose was significantly affected by both bladder volume and tandem physical length for T≤4 cm. This was reflected on the values obtained for normalD2cm3, normalD1cm3, and normalD0.1cm3 for both empty and full bladder cases. When T>4 cm, no correlation could be established between variations in bladder dose and bladder volume. Rectum dose was generally lower when the bladder was empty and T>4 cm. Dose to sigmoid was increased when T>4 cm; this increase was larger when the bladder was full. Our results suggest that, for tandems longer than 4 cm, keeping the bladder empty may reduce the dose to rectum and sigmoid. This is contrary to cases where a shorter than 4 cm tandem is used in which a full bladder (about 50–120 cm3) tends to result in a lower dose to rectum and sigmoid. Attention should be given to doses to sigmoid with long tandem lengths, as a larger tandem generally results in a larger dose to sigmoid.PACS number(s): 87.53.Jw

Section: Discussionmentioning

confidence: 99%

A comparison of organs at risk doses in GYN intracavitary brachytherapy for different tandem lengths and bladder volumes

Siavashpour

Aghamiri

Jaberi

et al. 2016

Self Cite

“…In‐house image manipulation routines were used to extract only the green channel pixel values of the

4 \times 8 {cm}^{2}

region of interest (ROI) of the RGB scanned image. The film data within 5 mm of each border of the films were ignored (15) . To reduce inherent noise, a 2D median filter of

3 \times 3 pixels

was applied.…”

Section: Methodsmentioning

confidence: 99%

“…DoseLab version 6.40 was used for the analysis. The ROI was manually selected before the comparison such that the regions within 5 mm from the edges of the film were ignored (15) . The shortest distance between the selected ROI and the pedicle screws is approximately 10 mm.…”

Section: Methodsmentioning

confidence: 99%

On the accuracy of dose prediction near metal fixation devices for spine SBRT

Cheng

Bromley

Oborn

et al. 2016

The metallic fixations used in surgical procedures to support the spine mechanically usually consist of high‐density materials. Radiation therapy to palliate spinal cord compression can include prophylactic inclusion of potential tumor around the site of such fixation devices. Determination of the correct density and shape of the spine fixation device has a direct effect on the dose calculation of the radiation field. Even with the application of modern computed tomography (CT), under‐ or overestimation of dose, both immediately next to the device and in the surrounding tissues, can occur due to inaccuracies in the dose prediction algorithm. In this study, two commercially available dose prediction algorithms (Eclipse AAA and ACUROS), EGSnrc Monte Carlo, and GAFchromic film measurements were compared for a clinical spine SBRT case to determine their accuracy. An open six‐field plan and a clinical nine‐field IMRT plan were applied to a phantom containing a metal spine fixation device. Dose difference and gamma analysis were performed in and around the tumor region adjacent to the fixation device. Dose calculation inconsistency was observed in the open field plan. However, in the IMRT plan, the dose perturbation effect was not observed beyond 5 mm. Our results suggest that the dose effect of the metal fixation device to the spinal cord and the tumor volume is not observable, and all dose calculation algorithms evaluated can provide clinically acceptable accuracy in the case of spinal SBRT, with the tolerance of 95% for gamma criteria of 3%/3 mm.PACS number(s): 87.53.bn, 87.53.Ly, 87.55.kd

“…To safely implement 3D image‐based HDR BT for cervical cancer, the European GYN group, Groupe Européen de Curiethérapie (GEC)—European Society for Radiotherapy and Oncology (ESTRO) working group provided several valuable guidelines for 3D image‐based HDR planning. These guidelines focused on target delineation in MRI; 2 , 3 dosimetry, physics tests, and radiation biology; (4) commissioning and applicator reconstruction for plastic applicators; (5) and MRI protocol recommendations for better image acquisition (6) . In addition, the challenges implicit in applicator reconstruction uncertainty were investigated for CT image‐based HDR planning (7) and for 0.3 Tesla (T) open MR scanner planning (8) .…”

Section: Introductionmentioning

confidence: 99%

“…This study presents a detailed explanation of the physics required for the commissioning of 3D image‐based TPS using HDR BT for the treatment of cervical cancer by adapting concepts from the literature 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 15 , 18 , 20 , 21 and focuses mainly on the 3D‐image based HDR BT planning challenges that are not fully addressed in the literature. These include: the applicator library in the TPS, titanium applicator reconstruction accuracy on MRI exclusively used for treatment planning, image manipulation tools in 3D image based TPS, dose calculation algorithm, and dose‐volume histogram (DVH).…”

Section: Introductionmentioning

confidence: 99%

Commissioning of a 3D image‐based treatment planning system for high‐dose‐rate brachytherapy of cervical cancer

Kim

Modrick

Pennington

et al. 2016

The objective of this work is to present commissioning procedures to clinically implement a three‐dimensional (3D), image‐based, treatment‐planning system (TPS) for high‐dose‐rate (HDR) brachytherapy (BT) for gynecological (GYN) cancer. The physical dimensions of the GYN applicators and their values in the virtual applicator library were varied by 0.4 mm of their nominal values. Reconstruction uncertainties of the titanium tandem and ovoids (T&O) were less than 0.4 mm on CT phantom studies and on average between 0.8‐1.0 mm on MRI when compared with X‐rays. In‐house software, HDRCalculator, was developed to check HDR plan parameters such as independently verifying active tandem or cylinder probe length and ovoid or cylinder size, source calibration and treatment date, and differences between average Point A dose and prescription dose. Dose‐volume histograms were validated using another independent TPS. Comprehensive procedures to commission volume optimization algorithms and process in 3D image‐based planning were presented. For the difference between line and volume optimizations, the average absolute differences as a percentage were 1.4% for total reference air KERMA (TRAK) and 1.1% for Point A dose. Volume optimization consistency tests between versions resulted in average absolute differences in 0.2% for TRAK and 0.9 s (0.2%) for total treatment time. The data revealed that the optimizer should run for at least 1 min in order to avoid more than 0.6% dwell time changes. For clinical GYN T&O cases, three different volume optimization techniques (graphical optimization, pure inverse planning, and hybrid inverse optimization) were investigated by comparing them against a conventional Point A technique. End‐to‐end testing was performed using a T&O phantom to ensure no errors or inconsistencies occurred from imaging through to planning and delivery. The proposed commissioning procedures provide a clinically safe implementation technique for 3D image‐based TPS for HDR BT for GYN cancer.PACS number(s): 87.55.D‐