A comparison of HDR near source dosimetry using a treatment planning system, Monte Carlo simulation, and radiochromic film

Amoush, A.; Luckstead, M; Lamba, Michael; Elson, Howard R.; Kassing, W

doi:10.1016/j.meddos.2012.10.006

Cited by 5 publications

(4 citation statements)

References 17 publications

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“…The radiochromic film has replaced its predecessor, the radiographic film, as the film of choice for clinical radiology/radiotherapy applications since it eliminates the need for post‐processing and exhibits a wider dynamic range (up to hundreds of Gy). Therapeutic applications of radiochromic films include the patient‐specific Quality Assurance (QA), 1–4 linac commissioning, 5 brachytherapy QA, 6–10 treatment planning system (TPS) dose validation, 11 and so forth. The major advantage of radiochromic film over other dosimeters in brachytherapy applications is its high spatial resolution, customizability into any shape, and 2D measurement capability.…”

Section: Introductionmentioning

confidence: 99%

Evaluating dosimetric accuracy of the 6 MV calibration on EBT3 film in the use of Ir‐192 high dose rate brachytherapy

Huang

Gaballa

Chang

2022

J Applied Clin Med Phys

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To evaluate the dosimetric accuracy of EBT3 film calibrated with a 6 MV beam for high dose rate brachytherapy and propose a novel method for direct film calibration with an Ir-192 source. Methods: The 6 MV calibration was performed in water on a linear accelerator (linac). The Ir-192 calibration was accomplished by irradiating the film wrapped around a cylinder applicator with an Ir-192 source. All films were scanned 1-day post-irradiation to acquire calibration curves for all three (red, blue, and green) channels. The Ir-192 calibration films were also used for single-dose comparison. Moreover, an independent test film under a H.A.M. applicator was irradiated and the 2D dose distribution was obtained separately for each calibration using the red channel data. Gamma analysis and point-by-point profile comparison were performed to evaluate the performance of both calibrations. The uncertainty budget for each calibration system was analyzed. Results: The red channel had the best performance for both calibration systems in the single-dose comparison. We found a significant 4.89% difference from the reference for doses <250 cGy using the 6 MV calibration, while the difference was only 0.87% for doses >600 cGy. Gamma analysis of the 2D dose distribution showed the Ir-192 calibration had a higher passing rate of 91.9% for the 1 mm/2% criterion, compared to 83.5% for the 6 MV calibration. Most failing points were in the low-dose region (<200 cGy). The point-by-point profile comparison reported a discrepancy of 2%-3.6% between the Ir-192 and 6 MV calibrations in this low-dose region. The linac-and Ir-192-based dosimetry systems had an uncertainty of 4.1% (k = 2) and 5.66% (k = 2), respectively. Conclusions: Direct calibration of EBT3 films with an Ir-192 source is feasible and reliable, while the dosimetric accuracy of 6 MV calibration depends on the dose range. The Ir-192 calibration should be used when the measurement dose range is below 250 cGy.

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Section: Introductionmentioning

confidence: 99%

Evaluating dosimetric accuracy of the 6 MV calibration on EBT3 film in the use of Ir‐192 high dose rate brachytherapy

Huang

Gaballa

Chang

2022

J Applied Clin Med Phys

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“…Scenarios where dose evaluation occurs very close to a source are subject to great uncertainties due to extrapolation of TG43 data in short distances and uncertainties in the source model [19]. Other groups have observed large discrepancies of > 20% between MBDCAs and TG43based treatment planning systems near 192 Ir source [18,24]. For GYN perineal template interstitial HDR-BT cases, the vaginal mucosa often contains many interstitial needles, and proximity of sources to vaginal dose calculation points are likely subject to high uncertainties.…”

Section: Discussionmentioning

confidence: 99%

Assessment of dose to vaginal mucosa for gynecologic template interstitial high-dose-rate brachytherapy using Monte Carlo simulation

Van Elburg,

Meyer,

Martell

et al. 2023

jcb

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Purpose: This study investigated reliable vaginal mucosa dose-volume histogram (DVH) metrics in gynecologic template interstitial high-dose-rate brachytherapy (HDR-BT) for the purpose of standardized dose reporting.Material and methods: Gynecologic template (Syed/Neblett) interstitial HDR-BT patients treated from September 2016 to November 2022 at the study institute were included in the cohort. Each patient implant included a vaginal mucosa contour defined by a 5 mm expansion from vaginal cylinder, then another volume with clinical target volume subtracted. DVH metrics were investigated between D 0.1cc to D 4cc . Clinical plans were re-calculated using Monte Carlo (MC) simulations both in heterogeneous material and in water.Results: The patient cohort included 61 patients with clinical plans using conventional homogeneous dose calculation (TG43). Heterogeneous vs. water MC dose differences were between -1.1% and -1.4% for all metrics investigated. DVH metrics D 1cc and smaller resulted in > 5% discrepancies between TG43 and MC dose (to water) calculation due to the proximity of source positions in/nearby the vaginal mucosa. Reliability improved when DVH metric volume was larger (D 2cc and D 4cc ). Both D 2cc and D 4cc presented very high linear correlation between TG43 and MC reported doses for the vagina, and average ± standard deviation dose difference was 4.6 ±2.9% and -3.0 ±1.9%, respectively. Dose differences decreased when the clinical target volume was removed: -1.5 ±3.5% and -0.8 ±2.1% for D 2cc and D 4cc , respectively.Conclusions: For perineal template gynecologic HDR-BT procedures, the 2 cc volume is the smallest representative volume that reliably reports vaginal dose and at minimum should be reported to establish dose and outcome evaluation.

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“…Skin treatments are characterized by the absence of radiation intersource attenuation and of full scatter conditions, but even if there are studies supporting the use of TG-43 in medical practice [ 33 , 34 , 35 ], deviations between prescribed and actually delivered doses may be clinically relevant.…”

Section: Introductionmentioning

confidence: 99%

Use of Thermoluminescence Dosimetry for QA in High-Dose-Rate Skin Surface Brachytherapy with Custom-Flap Applicator

Manna

Pugliese

Buonanno

et al. 2023

Sensors

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Surface brachytherapy (BT) lacks standard quality assurance (QA) protocols. Commercially available treatment planning systems (TPSs) are based on a dose calculation formalism that assumes the patient is made of water, resulting in potential deviations between planned and delivered doses. Here, a method for treatment plan verification for skin surface BT is reported. Chips of thermoluminescent dosimeters (TLDs) were used for dose point measurements. High-dose-rate treatments were simulated and delivered through a custom-flap applicator provided with four fixed catheters to guide the Iridium-192 (Ir-192) source by way of a remote afterloading system. A flat water-equivalent phantom was used to simulate patient skin. Elekta TPS Oncentra Brachy was used for planning. TLDs were calibrated to Ir-192 through an indirect method of linear interpolation between calibration factors (CFs) measured for 250 kV X-rays, Cesium-137, and Cobalt-60. Subsequently, plans were designed and delivered to test the reproducibility of the irradiation set-up and to make comparisons between planned and delivered dose. The obtained CF for Ir-192 was (4.96 ± 0.25) μC/Gy. Deviations between measured and TPS calculated doses for multi-catheter treatment configuration ranged from −8.4% to 13.3% with an average of 0.6%. TLDs could be included in clinical practice for QA in skin BT with a customized flap applicator.

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A comparison of HDR near source dosimetry using a treatment planning system, Monte Carlo simulation, and radiochromic film

Cited by 5 publications

References 17 publications

Evaluating dosimetric accuracy of the 6 MV calibration on EBT3 film in the use of Ir‐192 high dose rate brachytherapy

Evaluating dosimetric accuracy of the 6 MV calibration on EBT3 film in the use of Ir‐192 high dose rate brachytherapy

Assessment of dose to vaginal mucosa for gynecologic template interstitial high-dose-rate brachytherapy using Monte Carlo simulation

Use of Thermoluminescence Dosimetry for QA in High-Dose-Rate Skin Surface Brachytherapy with Custom-Flap Applicator

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