The Variability of Applicator Position among High Dose Rate Intracavitary Brachytherapy Applications in Cervical Cancer Patients Treated with Ring &amp; Tandem Applicators

Ebruli, Cuneyt; Demiral, Ays ̧e Nur; Çetingöz, Rıza; Eyiler, Ferhat; Kinay, Münir

doi:10.1177/030089160709300505

Cited by 10 publications

(12 citation statements)

References 14 publications

(12 reference statements)

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“…Additionally, the moving of the patient from imaging to the procedure room may affect the position of the applicator. 17 For our study, to decrease this variability, we minimized applicator movement by using interior vaginal packing as well as a rigid external immobilization device that was secured to the distal aspect of the applicator and fixed to a rigid treatment board. However, vaginal packing has the potential to displace the distal portion of the rectum during brachytherapy and decrease the dose received by the rectum.…”

Section: Discussionmentioning

confidence: 99%

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The Impact of Maximum Rectal Distention and Tandem Angle on Rectal Dose Delivered in 3D Planned Gynecologic High Dose–Rate Brachytherapy

Lim

Durbin‐Johnson²,

Valicenti

et al. 2013

International Journal of Gynecological Cancer

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Objective Computed tomography (CT)-based treatment planning for cervical cancer has allowed investigation into the volumetric radiation dose delivered to the rectum. The goal of intracavitary brachytherapy is to maximize the tumor dose while decreasing the dose to normal tissue like the rectum. We investigated the effects of tandem angle and maximum rectal distention on rectal dose delivered in HDR brachytherapy for locally advanced cervical cancer. Methods and Materials Between July 2007 and January 2010, 97 brachytherapy treatment planning CT scans from the first and last implant of 51 patients with locally advanced cervical cancer were reviewed. The rectum was manually contoured from the ischial tuberosity to the bottom of the sacroiliac joint. The maximum rectal distention was determined by measuring the largest anterior-posterior diameter of the rectum superior to the tandem ring and inferior to the end of the applicator. A volumetric measurement of the maximum and mean rectal dose, dose to 2cc (D2cc), dose to 1cc (D1cc) of the rectum was calculated. The tandem angle and the ICRU rectal point were recorded, and a dose volume histogram was referenced. Results The mean maximum rectal distention was 3.01cm. The mean D1cc, D2cc, mean rectal dose, maximum rectal dose, and ICRU rectal dose were 3.03 Gy, 2.78 Gy, 4.19 cGy, 1.40 cGy, and 2.99 Gy per treatment, respectively. In a multivariate analysis controlling for surface area, tandem angle, and body mass index (BMI), there was a significant increase in D2cc with increasing rectal distention (P=.016). There were no significant findings when observing the effects of tandem angle on D2cc. Conclusion Rectal distention significantly impacts D2cc delivered in HDR brachytherapy. In contrast, tandem angle does not. Concerted efforts to decrease rectal distention should be considered during treatment planning and delivery.

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Section: Discussionmentioning

confidence: 99%

“…A significant source of variation also stems from changes in the position of the applicator during brachytherapy. 17 Controlling for all these variables remains difficult, as they are not as easily measured.…”

Section: Discussionmentioning

confidence: 99%

The Impact of Maximum Rectal Distention and Tandem Angle on Rectal Dose Delivered in 3D Planned Gynecologic High Dose–Rate Brachytherapy

Lim

Durbin‐Johnson²,

Valicenti

et al. 2013

International Journal of Gynecological Cancer

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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%

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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“…However, 26 or in other applicator geometry such as ring and tandem for one anatomical position i.e., supine only. [30][31] Rotational shift associated with change in applicator angle was reported by Hoskins et al 32 and is about 20 0 . The higher degree of rotation reported in their study may be due to single line source used for vaginal cuff brachytherapy.…”

Section: Discussionmentioning

confidence: 82%

“…In case of brachytherapy there are studies on the use of template based standard plans versus individualized plans and pre-prepared treatment plans for curved structures such as esophagus. 28 There are few studies which evaluated variability of position of ring and tandem applicators [29][30] in ICBT in cancer cervix patients. Vaginal cuff irradiation is well studied with change in applicator angle 32 and patients position.…”

Section: Discussionmentioning

confidence: 99%

Dose variation due to change in planned position for patients with carcinoma of the cervix undergoing high-dose-rate brachytherapy- 2D dose analysis

Talluri

Yarrama

Ahamed

et al. 2015

Int J Cancer Ther Oncol

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The Variability of Applicator Position among High Dose Rate Intracavitary Brachytherapy Applications in Cervical Cancer Patients Treated with Ring & Tandem Applicators

Abstract: In order to extract definitive conclusions about factors that affect positional reproducibility of ring and tandem applicators, studies are needed that include larger numbers of patients.

Cited by 10 publications

References 14 publications

The Impact of Maximum Rectal Distention and Tandem Angle on Rectal Dose Delivered in 3D Planned Gynecologic High Dose–Rate Brachytherapy

The Impact of Maximum Rectal Distention and Tandem Angle on Rectal Dose Delivered in 3D Planned Gynecologic High Dose–Rate Brachytherapy

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

Dose variation due to change in planned position for patients with carcinoma of the cervix undergoing high-dose-rate brachytherapy- 2D dose analysis

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