Spatial Reproducibility of the Ring and Tandem High-Dose Rate Cervix Applicator

Bahena, Judith Huerta; Martínez, Álvaro; Yan, Di; Mele, Elizabeth; Edmunson, Gregory; Brown, Debbie; Hardy, Maria; Brabbins, D.; Gustafson, Gary

doi:10.1016/s0360-3016(98)00026-1

Cited by 45 publications

(13 citation statements)

References 13 publications

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“…In addition to the systematic and random fluctuations that are inherent to the ring, there can be considerable interfractional ( 14 – 15 ) or intrafractional ( 16 ) variation in the positioning of the applicator. These effects could combine to produce larger dosimetric discrepancies than shown here, particularly if a new plan is not generated for each fraction.…”

Section: Discussionmentioning

confidence: 99%

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Commissioning of Varian ring & tandem HDR applicators: reproducibility and interobserver variability of dwell position offsets

McMahon

Zhuang

Steffey

et al. 2011

J Applied Clin Med Phys

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Studies have shown that source dwells within Varian's HDR CT/MR compatible ring applicators can deviate from intended positions by several millimeters. Quantifying this offset is an important part of commissioning. The aims of this study were to: 1) determine the reproducibility of the offset, 2) study the interobserver variation in the offset's measurement, and 3) quantify the dosimetric impact of the offset. Offsets were measured for four ring applicators: two 30°, one 45°, and one 60°. Dwell positions were measured five times for each ring to determine the reproducibility of source positioning. Experiments were done to compare two separate source wires, as well as different time points within a single source wire's lifecycle. Data were analyzed by three independent observers. To quantify the dosimetric impact of the offset, a treatment plan was generated using BrachyVision. The dose to point A, and the normalD2cc metric for rectum and bladder were calculated with and without the offset. For the 45° and 60° rings, measured offsets were 3.0 mm and 3.6 mm, respectively. The 30° ring showed substantial variation in distal dwell positions (maximum difference between the five experiments of 2.9 mm). Subsequent testing of a replacement ring showed an offset of 2.4 mm that was more reproducible. Offsets varied less than 1 mm between different source wires, and changed less than 1 mm over the course of a source wire's lifecycle. When comparing observers, the average range in a measurement of a dwell position was 0. 5mm (σ = 0.2 mm, max 1.3 mm). The offset resulted in dose variations to point A, bladder, and rectum of less than 1%, 2%, and 5%, respectively. Results indicate that Varian rings can show systematic and random offsets of more than 3 mm. Some can be considered defective and should be replaced. Each applicator should be individually commissioned and reproducibility should be confirmed with multiple tests.PACS number: 87.56.‐v, 87.53.Jw

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Section: Discussionmentioning

confidence: 99%

“…This is potentially larger than reported interfractional angular variation in ring applicator placement. ( 14 ) …”

Section: Discussionmentioning

confidence: 99%

Commissioning of Varian ring & tandem HDR applicators: reproducibility and interobserver variability of dwell position offsets

McMahon

Zhuang

Steffey

et al. 2011

J Applied Clin Med Phys

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“…There is a day-to-day variation in applicator positioning and also variation in organ size and shape. Multiple studies have shown that there are significant day to day positional variations in applicator positions in the same patient, even when the insertions are done under the same settings and by the same physician [11–13]. This variation is neither dependent upon the age of the patient and stage of the disease, nor upon the gap between EBRT and brachytherapy.…”

Section: Discussionmentioning

confidence: 99%

Clinical Investigations A comparison of dose distribution from Manchester-style and Fletcher-style intracavitary brachytherapy applicator systems in cervical cancer

Basu¹,

Basu²,

Chakraborti³

et al. 2012

jcb

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PurposeDuring intracavitary brachytherapy (ICBT) for cervical cancer, the choice of applicator system remains rather arbitrary. However, as the applicator geometry may play an important role in dose distribution, thereby improving the therapeutic ratio, this study was conducted to compare the Manchester-style and Fletcher-style applicator systems.Material and methodsAfter completion of EBRT, 22 patients with cervical cancer (stage IIA-IIIB) underwent intracavitary brachytherapy. Two different types of applicators: Manchester-style and Fletcher-style were used for each patient for alternate insertions. The purpose was to compare the dose distribution obtained when two different applicators were applied to the same patient. CT based computerized treatment planning was done and dose was prescribed to point A. After optimization, height, width and thickness of the 100% isodose curve, as well as the 100% isodose volume were noted. Dose received by the urinary bladder and rectum were noted.ResultsThe 100% isodose volume and its maximum width were significantly greater (P value < 0.0001 in both occasions) when Manchester-style applicator was used. However, the dose received by 0.1 cc, 1.0 cc and 2.0 cc of the urinary bladder were all significantly greater (P value < 0.0001) with the Manchester-style applicator. No significant difference was found in rectal doses.ConclusionsThe larger 100% isodose volume, as well as the greater width achieved with the use of Manchester-style applicator can be helpful in circumstances where the tumour is large in size. However, this must be balanced against the increased dose received by the urinary bladder.

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“…Previous studies have shown that interfractional organ motion in the pelvis may be substantial 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 . Lee et al (15) found average changes in cervix position can be up to 10 mm, 8 mm, and 16 mm in the lateral, superior/inferior, and anterior/posterior directions, respectively.…”

Section: Introductionmentioning

confidence: 98%

A comprehensive evaluation of adaptive daily planning for cervical cancer HDR brachytherapy

Meerschaert

Nalichowski

Burmeister

et al. 2016

J Applied Clin Med Phys

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The purpose of this study was to evaluate adaptive daily planning for cervical cancer patients who underwent high‐dose‐rate intracavitary brachytherapy (HDR‐BT) using comprehensive interfractional organ motion measurements. This study included 22 cervical cancer patients who underwent 5 fractions of HDR‐BT. Regions of interest (ROIs) including high‐risk clinical tumor volume (HR‐CTV) and organs at risk (OARs) were manually contoured on daily CT images. All patients were clinically treated with adaptive daily plans (ADP), which involved ROI delineation and dose optimization at each treatment fraction. Single treatment plans (SP) were retrospectively generated by applying the first treatment fraction's dwell times adjusted for decay and dwell positions of the applicator to subsequent treatment fractions. Various existing similarity metrics were calculated for the ROIs to quantify interfractional organ variations. A novel similarity (JRARM) score was established, which combined both volumetric overlap metrics (DSC, JSC, and RVD) and distance metrics (ASD, MSD, and RMSD). Linear regression was performed to determine a relationship between interfractional organ variations of various similarity metrics and D2cc variations from both plans. Wilcoxon signed‐rank tests were used to assess ADP and SP by comparing EQD2thinmathspaceD2cc(α/β=3) for OARs. For interfractional organ variations, the sigmoid demonstrated the greatest variations based on the JRARM, DSC, and RMSD metrics. Comparisons between paired ROIs showed differences in metrics at each treatment fraction. RVD, MSD, and RMSD were found to be significantly correlated to D2cc variations for bladder and sigmoid. The comparison between plans found ADP provided lower EQD2 D2cc of OARs than SP. Specifically, the sigmoid demonstrated statistically significant dose variations (p=0.015). Substantial interfractional organ motion occurs during HDR‐BT based on comprehensive measurements and may significantly affect D2cc of OARs. Adaptive daily planning provides improved dose sparing for OARs compared to single planning with the extent of sparing being different among OARs.PACS number(s): 87.55.D, 87.55.de, 87.55.kh, 87.57.nj

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Spatial Reproducibility of the Ring and Tandem High-Dose Rate Cervix Applicator

Cited by 45 publications

References 13 publications

Commissioning of Varian ring & tandem HDR applicators: reproducibility and interobserver variability of dwell position offsets

Commissioning of Varian ring & tandem HDR applicators: reproducibility and interobserver variability of dwell position offsets

Clinical Investigations A comparison of dose distribution from Manchester-style and Fletcher-style intracavitary brachytherapy applicator systems in cervical cancer

A comprehensive evaluation of adaptive daily planning for cervical cancer HDR brachytherapy

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