EQUIVALENT UNIFORM DOSE SENSITIVITY TO CHANGES IN ABSORBED DOSE DISTRIBUTION

2013 ◽  
Vol 06 (01) ◽  
pp. 1250069
Author(s):  
FRANCISCO CUTANDA-HENRÍQUEZ ◽  
SILVIA VARGAS-CASTRILLÓN
Keyword(s):  
Treatment Planning ◽  
Dose Distribution ◽  
Absorbed Dose ◽  
Target Volume ◽  
Simple Expression ◽  
External Beam Radiation ◽  
Equivalent Uniform Dose ◽  
Beam Radiation ◽  
Dose Volume Histograms ◽  
Small Change

Treatment planning in external beam radiation therapy (EBRT) utilizes dose volume histograms (DVHs) as optimization and evaluation tools. They present the fraction of planning target volume (PTV) receiving more than a given absorbed dose, against the absorbed dose values, and a number of radiobiological indices can be computed with their help. Equivalent uniform dose (EUD) is the absorbed dose that, uniformly imparted, would yield the same biological effect on a tumor as the dose distribution described by the DVH. Uncertainty and missing information can affect the dose distribution, therefore DVHs can be modeled as samples from a set of possible outcomes. This work studies the sensitivity of the EUD index when a small change in absorbed dose distribution takes place. EUD is treated as a functional on the set of DVHs. Defining a Lévy distance on this set and using a suitable expansion of the functional, a very simple expression for a bound on the variation of EUD when the dose distribution changes is found. This bound is easily interpreted in terms of standard treatment planning practice.

scholarly journals RADT-30. COPLANAR AND NON-COPLANAR VMAT ARC SETTING FOR GLIOBLASTOMA MULTIFORME – DOSIMETRIC AND RADIOBIOLOGICAL COMPARISONS

2020 ◽  
Vol 22 (Supplement_2) ◽  
pp. ii188-ii188
Author(s):  
Vanessa Moldoveanu ◽  
Mihai Dumitrache ◽  
Xenia Bacinschi ◽  
Luiza Serbanescu ◽  
Rodica Anghel
Keyword(s):  
Glioblastoma Multiforme ◽  
Organs At Risk ◽  
Absorbed Dose ◽  
Target Volume ◽  
Tumor Control ◽  
Normal Brain ◽  
Tumor Control Probability ◽  
Equivalent Uniform Dose ◽  
Dose Volume Histograms ◽  
Arc Setting

Abstract OBJECTIVES To evaluate three different arc arrangements in glioblastoma multiforme (GBM) treatment planning. METHODS Eighteen GBM patients were replanned by using one full arc (1FA), two full coplanar arcs (2FA), and three full non- coplanar arcs (3FA). Dose-volume histograms (DVHs) were used to calculate conformity (CI), homogeneity (HI) and gradient indices (GI), the dose received by 5% (D5%) and 95% (D95%) of the planning target volume (PTV) and maximum (Dmax) and minimum (Dmin) absorbed dose for organs at risk (OARs), including normal brain (brain excluding PTV). General equivalent uniform dose (gEUD) for both PTV and OARs and EUD based tumor control probability (TCP) and normal tissue control probability (NTCP) were calculated as radiobiological parameters. Monitor units (MUs) were also computed and compared. RESULTS All three plans resulted in similar conformity, while 2FA resulted in a better homogeneity than 1FA (0.06vs. 0.07, p=0.007). 2FA vs. 1FA dose analysis for PTV revealed a lower D5% (61.28 vs. 61.37 Gy, p=0.014), a higher D95% (58.7 vs. 58.47 Gy, p=0.008) and a higher TCP (37.73 vs.37.38%, p=0.008). The utilization of 3FA did not significantly change the outcome of PTV but managed to decrease GI in comparison to both 1FA and 2FA (4.11 vs. 5.19 and 5.49, p< 0.05). Regarding NB, 1FA scored a higher Dmax than 2FA (62.32 vs. 61.98 Gy, p=0.005), while 3FA scored a higher Dmin than 1FA and 2FA (2.52 vs. 1.08 and 1.10 Gy, p< 0.05). No difference in NB NTCP was noted between techniques. Furthermore, 3FA yielded more MUs when compared to coplanar patters (566.74 vs. 486.78, p= 0.015 for 1FA and 495.98, p=0.019 for 2FA). CONCLUSION Although all three approaches resulted in clinical admissible outcome, the utilization of complex non-coplanar arrangement resulted in a stepper dose fall off but did not improve PTV results and increased machine MUs.

Evaluation of set-up errors and estimation of set-up margin during external beam radiation therapy of prostate cancer using electronic portal imaging device (EPID)

2021 ◽  
pp. 1-8
Author(s):  
Daryoush Khoramian ◽  
Soroush Sistani ◽  
Bagher Farhood
Keyword(s):  
Prostate Cancer ◽  
Radiation Therapy ◽  
Target Volume ◽  
External Beam Radiation ◽  
Beam Radiation ◽  
Cancer Radiotherapy ◽  
Imaging Device ◽  
Portal Images ◽  
Set Up ◽  
Prostate Cancer Radiotherapy

Abstract Aim: In radiation therapy, accurate dose distribution in target volume requires accurate treatment setup. The set-up errors are unwanted and inherent in the treatment process. By achieving these errors, a set-up margin (SM) of clinical target volume (CTV) to planning target volume (PTV) can be determined. In the current study, systematic and random set-up errors that occurred during prostate cancer radiotherapy were measured by an electronic portal imaging device (EPID). The obtained values were used to propose the optimum CTV-to-PTV margin in prostate cancer radiotherapy. Materials and methods: A total of 21 patients with prostate cancer treated with external beam radiation therapy (EBRT) participated in this study. A total of 280 portal images were acquired during 12 months. Gross, population systematic (Σ) and random (σ) errors were obtained based on the portal images in Anterior–Posterior (AP), Medio-Lateral (ML) and Superior–Inferior (SI) directions. The SM of CTV to PTV were then calculated and compared by using the formulas presented by the International Commission on Radiation Units and Measurements (ICRU) 62, Stroom and Heijmen and Van Herk et al. Results: The findings showed that the population systematic errors during prostate cancer radiotherapy in AP, ML and SI directions were 1·40, 1·95 and 1·94 mm, respectively. The population random errors in AP, ML and SI directions were 2·09, 1·85 and 2·29 mm, respectively. The SM of CTV to PTV calculated in accordance with the formula of ICRU 62 in AP, ML and SI directions were 2·51, 2·68 and 3·00 mm, respectively. And according to Stroom and Heijmen, formula were 4·23, 5·19 and 5·48 mm, respectively. And Van Herk et al. formula were 4·96, 6·17 and 6·45 mm, respectively. Findings: The SM of CTV to PTV in all directions, based on the formulas of ICRU 62, Stroom and Heijmen and van Herk et al., were equal to 2·73, 4·98 and 5·86 mm, respectively; these values were obtained by averaging the margins in all directions.

Safety and feasibility of rhenium-186 nanoliposome (186RNL) in recurrent glioma: The ReSPECT phase 1 trial.

2021 ◽  
Vol 39 (15_suppl) ◽  
pp. 2061-2061
Author(s):  
Andrew J. Brenner ◽  
Ande Bao ◽  
William Phillips ◽  
Gregory Stein ◽  
Vibhudutta Awasthi ◽  
...  
Keyword(s):  
Dose Escalation ◽  
Tumor Volume ◽  
Phase 1 ◽  
Absorbed Dose ◽  
External Beam Radiation ◽  
Whole Body ◽  
Recurrent Glioma ◽  
Normal Brain ◽  
Beam Radiation ◽  
The Mean

2061 Background: While external beam radiation therapy (EBRT) remains a central component of the management of primary brain tumors, it is limited by tolerance of the surrounding normal brain tissue. Rhenium-186 NanoLiposome (186RNL) permits the delivery of beta-emitting radiation of high specific activity with excellent retention in the tumor. We report the results of the phase 1 study in recurrent glioma. Methods: A Phase 1 dose-escalation study of 186RNL in recurrent glioma utilizing a standard 3+3 design was undertaken to determine the maximum tolerated dose of 186RNL. 186RNL is administered by convection enhanced delivery (CED). Infusion is followed under whole body planar imaging and SPECT/CT. Repeat SPECT/CT imaging is performed immediately following, and at 1, 3, 5, and 8 days after 186RNL infusion to obtain dosimetry and distribution. Subjects were followed until disease progression by RANO criteria. Results: Eighteen subjects were treated across 6 cohorts. The mean tumor volume was 9.4 mL (range 1.1 – 23.4). The infused dose ranged from 1.0 mCi to 22.3 mCi and the volume of infusate ranged from 0.66 mL to 8.80 mL. From 1 – 4 CED catheters were used. The maximum catheter flow rate was 15 µl/min. The mean absorbed dose to the tumor volume was 239 Gy (CI 141 – 337; range 9 - 593), to normal brain was 0.72 Gy (CI 0.34 – 1.09; range 0.005 – 2.73), and to total body was 0.07 Gy (CI 0.04 – 0.10; range 0.001 – 0.23). The mean absorbed dose to the tumor volume when the percent tumor volume in the treatment volume was 75% or greater (n = 10) was 392 Gy (CI 306 – 478; range 143 – 593). Scalp discomfort and tenderness related to the surgical procedure did occur in 3 subjects. The therapy has been well tolerated, no dose-limiting toxicity has been observed, and no treatment-related serious adverse events have occurred despite markedly higher absorbed doses typically delivered by EBRT in patients with prior treatment. Responses have been observed supporting the clinical activity. Final results from the dose escalation will be presented. Conclusions: 186RNL administered by CED to patients with recurrent glioma results in a much higher absorbed dose of radiation to the tumor compared to EBRT without significant toxicity. The recommended Phase 2 dose is 22.3 mCi in 8.8 mL of infusate. Clinical trial information: NCT01906385. [Table: see text]

Utilising virtual bolus in superficial planning target volume dose optimisation (TomoTherapy): a phantom study

2019 ◽  
Vol 19 (1) ◽  
pp. 65-70
Author(s):  
Gim Chee Ooi ◽  
Iskandar Shahrim Bin Mustafa
Keyword(s):  
Treatment Planning ◽  
Planning Target Volume ◽  
Treatment Plan ◽  
Target Volume ◽  
The Body ◽  
Phantom Study ◽  
Planning System ◽  
Treatment Planning System ◽  
Dose Volume Histograms ◽  
Photon Fluence

AbstractAim:This is a phantom study to evaluate the dosimetry effects of using virtual bolus (VB) in TomoTherapy Treatment Planning System (TPS) optimisation for superficial planning target volume (PTV) that extends to the body surface. Without VB, the inverse-planning TPS will continuously boost the photon fluence at the surface of the superficial PTV due to lack of build-up region. VB is used during TPS optimisation only and will not be present in actual treatment delivery.Materials and methods:In this study, a dummy planning target was contoured on a cylindrical phantom which extends to the phantom surface, and VB of various combinations of thickness and density was used in treatment planning optimisation with TomoTherapy TPS. The plans were then delivered with the treatment modality TomoTherapy. Radiochromic films (Gafchromic EBT3) were calibrated and used for dose profiles measurements. TomoTherapy Planned-Adaptive software was used to analyse the delivered Dose-Volume Histograms (DVHs).Results:The use of 2 mm VB was not providing adequate build-up area and was unable to reduce the hot spots during treatment planning and actual delivery. The use of 4 mm VB was able to negate the photon fluence boosting effect by the TPS, and the actual delivery showed relatively small deviations from the treatment plan. The use of 6 mm VB caused significant dose overestimation by the TPS in the superficial regions resulting in insufficient dose coverage delivered.Findings:VB with the combination of 4 mm thickness and 1·0 g/cc density provides the most robust solution for the TomoTherapy TPS optimisation of superficial PTV.

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