The dose distribution of low dose rate Cs-137 in intracavitary brachytherapy: comparison of Monte Carlo simulation, treatment planning calculation and polymer gel measurement

Fragoso, M; Love, P. A.; Verhaegen, Frank; Nalder, C; Bidmead, A. Margaret; Leach, MO; Webb, Steve

doi:10.1088/0031-9155/49/24/005

Cited by 25 publications

(20 citation statements)

References 34 publications

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“…30,31 3D dosimetry for these cases was performed using polymer gels, the oxygen sensitivity of which can limit sensitivity at low doses 31 and necessitates use of an airtight container. The airtight container may also limit ability to measure dose near the applicator surface, depending on applicator geometry and container construction.…”

Section: Discussionmentioning

confidence: 99%

Commissioning a CT-compatible LDR tandem and ovoid applicator using Monte Carlo calculation and 3D dosimetry

et al. 2012

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Purpose: To determine the geometric and dose attenuation characteristics of a new commercially available CT-compatible LDR tandem and ovoid (T&O) applicator using Monte Carlo calculation and 3D dosimetry. Methods: For geometric characterization, we quantified physical dimensions and investigated a systematic difference found to exist between nominal ovoid angle and the angle at which the afterloading buckets fall within the ovoid. For dosimetric characterization, we determined source attenuation through asymmetric gold shielding in the buckets using Monte Carlo simulations and 3D dosimetry. Monte Carlo code MCNP5 was used to simulate 1.5 × 10 9 photon histories from a 137 Cs source placed in the bucket to achieve statistical uncertainty of 1% at a 6 cm distance. For 3D dosimetry, the distribution about an unshielded source was first measured to evaluate the system for 137 Cs, after which the distribution was measured about sources placed in each bucket. Cylindrical PRESAGE R dosimeters (9.5 cm diameter, 9.2 cm height) with a central channel bored for source placement were supplied by Heuris Inc. The dosimeters were scanned with the Duke Large field of view Optical CT-Scanner before and after delivering a nominal dose at 1 cm of 5-8 Gy. During irradiation the dosimeter was placed in a water phantom to provide backscatter. Optical CT scan time lasted 15 min during which 720 projections were acquired at 0.5• increments, and a 3D distribution was reconstructed with a (0.05 cm) 3 isotropic voxel size. The distributions about the buckets were used to calculate a 3D distribution of transmission rate through the bucket, which was applied to a clinical CT-based T&O implant plan. Results: The systematic difference in bucket angle relative to the nominal ovoid angle (105 • ) was 3.1• -4.7• . A systematic difference in bucket angle of 1 • , 5• , and 10• caused a 1% ± 0.1%, 1.7% ± 0.4%, and 2.6% ± 0.7% increase in rectal dose, respectively, with smaller effect to dose to Point A, bladder, sigmoid, and bowel. For 3D dosimetry, 90.6% of voxels had a 3D γ -index (criteria = 0.1 cm, 3% local signal) below 1.0 when comparing measured and expected dose about the unshielded source. Dose transmission through the gold shielding at a radial distance of 1 cm was 85.9% ± 0.2%, 83.4% ± 0.7%, and 82.5% ± 2.2% for Monte Carlo, and measurement for left and right buckets, respectively. Dose transmission was lowest at oblique angles from the bucket with a minimum of 56.7% ± 0.8%, 65.6% ± 1.7%, and 57.5% ± 1.6%, respectively. For a clinical T&O plan, attenuation from the buckets leads to a decrease in average Point A dose of ∼3.2% and decrease in D 2cc to bladder, rectum, bowel, and sigmoid of 5%, 18%, 6%, and 12%, respectively. Conclusions: Differences between dummy and afterloading bucket position in the ovoids is minor compared to effects from asymmetric ovoid shielding, for which rectal dose is most affected. 3D dosimetry can fulfill a novel role in verifying Monte Carlo calculations of complex dose distributions as are common about brachy...

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Section: Discussionmentioning

confidence: 99%

Commissioning a CT-compatible LDR tandem and ovoid applicator using Monte Carlo calculation and 3D dosimetry

et al. 2012

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“…10 Different combinations of active and inactive pellets are used for GYN cancer. The Nucletron PLATO treatment planning system (TPS) calculates the dose delivered by the unit at the point of interest.…”

Section: Selectron Ldr Systemmentioning

confidence: 99%

“…The Nucletron PLATO treatment planning system (TPS) calculates the dose delivered by the unit at the point of interest. 10 The TPS determines the dose distribution around different combinations of sources and spacers by assuming each active pellet as a point source, using the superposition dose calculation technique. The Selectron unit consists of spherical Cs-137 pellets composed of 1.5 mm active source core of ceramic, encapsulated in 0.5 mm steel, with a total diameter of 2.5 mm.…”

Section: Selectron Ldr Systemmentioning

confidence: 99%

Dose distribution verification for GYN brachytherapy using EBT Gafchromic film and TG-43 calculation

Gholami

Arfaee

Jaberi

et al. 2016

Reports of Practical Oncology & Radiotherapy

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“…This dose represents the same dwell positions and dwell times as the ovoid portion of the tandem and ovoids assembly. The Nucletron (PLATO v.11.4) treatment planning system (TPS) was utilized for calculation of the dose distribution by this system (5) .…”

Section: Ldr Cs-137 Selectron Remote After-loading Systemmentioning

confidence: 99%

“…The accuracy and functionality of this phantom design has been examined using a well stablished LDR 137 Cs Selectron remote afterloading system, which is distributed by Nucletron (Nucletron BV, Veenendaal, The Netherlands) (5) .…”

Section: Introductionmentioning

confidence: 99%

A novel phantom design for brachytherapy quality assurance

Gholami

Arfaee²,

Jaberi

et al. 2016

IJRR

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Background: One major challenge in brachytherapy is to verify the accuracy of dose distribu ons calculated by the treatment planning system. In this project, a new phantom design has been introduced for quality assurance of dose distribu ons in gynocological (GYN) brachytherapy implants using EBT GafChromic film. Materials and Methods: This phantom has been designed and fabricated from 90 slabs of 18×16×0.2 cm 3 Perspex to accommodate a tandem and ovoids assembly, which is normally used for GYN brachytherapy treatment. In addi on, this phantom design is allowing the use EBT GafChromic films for dosimetric verifica on of GYN implants with Cs-137 Selectron LDR system. With this assembly, GafChromic films were exposed using a plan designed to deliver 2.5 Gy dose to point "A" in Manchester system for tandem and ovoids configura ons and to deliver 1.5 Gy of dose to 0.5 cm distance from the lateral surface of ovoids for using ovoid-pair. The measured dose distribu ons with GafChromic films were compared with the TPS isodose lines both numerically and spa ally. For a quan ta ve analysis of the results, the measured doses values at several points of interest were evaluated with the treatment planning data and values obtained following the TG-43 dose calcula on formalism. Results: The results of these inves ga ons have indicated that the new phantom design enables us to measure differences of greater than ±6% for LDR brachytherapy GYN treatments. Conclusion:The new phantom design could be u lized for the QA procedure of the brachytherapy remote aCer loading systems to confirm the accuracy of dose distribu on in GYN implants.

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The dose distribution of low dose rate Cs-137 in intracavitary brachytherapy: comparison of Monte Carlo simulation, treatment planning calculation and polymer gel measurement

Cited by 25 publications

References 34 publications

Commissioning a CT-compatible LDR tandem and ovoid applicator using Monte Carlo calculation and 3D dosimetry

Commissioning a CT-compatible LDR tandem and ovoid applicator using Monte Carlo calculation and 3D dosimetry

Dose distribution verification for GYN brachytherapy using EBT Gafchromic film and TG-43 calculation

A novel phantom design for brachytherapy quality assurance

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