scholarly journals Dosimetric impact of organ at risk daily variation during prostate stereotactic ablative radiotherapy

2020 ◽  
Vol 93 (1108) ◽  
pp. 20190789 ◽  
Author(s):  
Lynsey Devlin ◽  
David Dodds ◽  
Azmat Sadozye ◽  
Philip McLoone ◽  
Nicholas MacLeod ◽  
...  
Keyword(s):  
At Risk ◽  
Organs At Risk ◽  
Cone Beam Ct ◽  
Volumetric Modulated Arc Therapy ◽  
Interquartile Range ◽  
Stereotactic Ablative Radiotherapy ◽  
Geometric Uncertainties ◽  
Rectal Volume ◽  
Significant Difference ◽  
Dosimetric Analysis

Objective: Prostate stereotactic ablative radiotherapy (SABR) delivers large doses using a fast dose rate. This amplifies the effect geometric uncertainties have on normal tissue dose. The aim of this study was to determine whether the treatment dose–volume histogram (DVH) agrees with the planned dose to organs at risk (OAR). Methods: 41 low–intermediate risk prostate cancer patients were treated with SABR using a linac based technique. Dose prescribed was 35 Gy in five fractions delivered on alternate days, planned using volumetric modulated arc therapy (VMAT) with 10X flattening filter free (FFF). On treatment, prostate was matched to fiducial markers on cone beam CT (CBCT). OAR were retrospectively delineated on 205 pre-treatment CBCT images. Daily CBCT contours were overlaid on the planning CT for dosimetric analysis. Verification plan used to evaluate the daily DVH for each structure. The daily doses received by OAR were recorded using the D%. Results: The median rectum and bladder volumes at planning were 67.1 cm3 (interquartile range 56.4–78.2) and 164.4 cm3 (interquartile range 120.3–213.4) respectively. There was no statistically significant difference in median rectal volume at each of the five treatment scans compared to the planning scan (p = 0.99). This was also the case for median bladder volume (p = 0.79). The median dose received by rectum and bladder at each fraction was higher than planned, at the majority of dose levels. For rectum the increase ranged from 0.78–1.64Gy and for bladder 0.14–1.07Gy. The percentage of patients failing for rectum D35% < 18 Gy (p = 0.016), D10% < 28 Gy (p = 0.004), D5% < 32 Gy (p = 0.0001), D1% < 35 Gy (p = 0.0001) and bladder D1% < 35 Gy (p = 0.001) at treatment were all statistically significant. Conclusion: In this cohort of prostate SABR patients, we estimate the OAR treatment DVH was higher than planned. This was due to rectal and bladder organ variation. Advances in knowledge: OAR variation in prostate SABR using a FFF technique, may cause the treatment DVH to be higher than planned.

scholarly journals The Potential Role of Intensity-Modulated Proton Therapy in Hepatic Carcinoma in Mitigating the Risk of Dose De-Escalation

2020 ◽  
Vol 19 ◽  
pp. 153303382098041
Author(s):  
Luca Cozzi ◽  
Tiziana Comito ◽  
Mauro Loi ◽  
Antonella Fogliata ◽  
Ciro Franzese ◽  
...  
Keyword(s):  
At Risk ◽  
Proton Therapy ◽  
Organs At Risk ◽  
Volumetric Modulated Arc Therapy ◽  
Intensity Modulated Proton Therapy ◽  
Intensity Modulated ◽  
Number Of Patients ◽  
Target Volumes ◽  
Dosimetric Analysis

Purpose: To investigate the role of intensity-modulated proton therapy (IMPT) for hepatocellular carcinoma (HCC) patients to be treated with stereotactic body radiation therapy (SBRT) in a risk-adapted dose prescription regimen. Methods: A cohort of 30 patients was retrospectively selected as “at-risk” of dose de-escalation due to the proximity of the target volumes to dose-limiting healthy structures. IMPT plans were compared to volumetric modulated arc therapy (VMAT) RapidArc (RA) plans. The maximum dose prescription foreseen was 75 Gy in 3 fractions. The dosimetric analysis was performed on several quantitative metrics on the target volumes and organs at risk to identify the relative improvement of IMPT over VMAT and to determine if IMPT could mitigate the need of dose reduction and quantify the consequent potential patient accrual rate for protons. Results: IMPT and VMAT plans resulted in equivalent target dose distributions: both could ensure the required coverage for CTV and PTV. Systematic and significant improvements were observed with IMPT for all organs at risk and metrics. An average gain of 9.0 ± 11.6, 8.5 ± 7.7, 5.9 ± 7.1, 4.2 ± 6.4, 8.9 ± 7.1, 6.7 ± 7.5 Gy was found in the near-to-maximum doses for the ribs, chest wall, heart, duodenum, stomach and bowel bag respectively. Twenty patients violated one or more binding constraints with RA, while only 2 with IMPT. For all these patients, some dose de-intensification would have been required to respect the constraints. For photons, the maximum allowed dose ranged from 15.0 to 20.63 Gy per fraction while for the 2 proton cases it would have been 18.75 or 20.63 Gy. Conclusion: The results of this in-silico planning study suggests that IMPT might result in advantages compared to photon-based VMAT for HCC patients to be treated with ablative SBRT. In particular, the dosimetric characteristics of protons may avoid the need for dose de-escalation in a risk-adapted prescription regimen for those patients with lesions located in proximity of dose-limiting healthy structures. Depending on the selection thresholds, the number of patients eligible for treatment at the full dose can be significantly increased with protons.

43: Predictors of Toxicity in a Randomized Study of Hypofractionated Versus Conventional Radiotherapy for Glioblastoma: Dosimetric Analysis of Organs at Risk

2021 ◽  
Vol 163 ◽  
pp. S21
Author(s):  
Fan Yang ◽  
Deepak Dinakaran ◽  
Amr A. Heikal ◽  
Sunita Ghosh ◽  
Shima Yaghoobpour Tari ◽  
...  
Keyword(s):  
At Risk ◽  
Organs At Risk ◽  
Randomized Study ◽  
Conventional Radiotherapy ◽  
Dosimetric Analysis

scholarly journals Transition from conformal to advanced radiotherapy techniques in treatment planning of gynecological cancer patients

2021 ◽  
pp. 77-77
Author(s):  
Borislava Petrovic ◽  
Olivera Ivanov ◽  
Milana Marjanovic ◽  
Jelena Licina ◽  
Ivan Gencel ◽  
...  
Keyword(s):  
At Risk ◽  
Cancer Patients ◽  
Maximum Dose ◽  
Organs At Risk ◽  
Gynecological Cancer ◽  
Conformal Radiation Therapy ◽  
Significant Difference ◽  
Treatment Plans ◽  
Radiation Induced ◽  
Risk Treatment

Background/ Aim. Transition from standard to highly conformal radiation therapy techniques, requires implementation of complex advanced dosimetry. The aim of the work was comparison of dosimetric parameters of 3DCRT and VMAT plan, as well as complications after treatment in relation to dosimetric parameters at gynecological cancer patients. Methods. Forty-nine gynecological cancer patients were included in the study. All patients were planned for 3D CRT, but due to unacceptable doses to organs at risk, treatment plans for IMRT or VMAT were generated for 21 patients. The patients were prescribed 50.4 Gy/28 fractions (4) and 45 Gy/25 fractions (45 patients). The coverage of PTV and doses to organs at risk were recorded. PTV margins were evaluated for both techniques according to the Van Herk formula. Results. ICRU 83 criteria were fulfilled in all 3DCRT /VMAT/IMRT plans providing optimal coverage of PTV. Doses to OARS: in average, the V45Gy in small bowel in IMRT/VMAT plans was four times smaller than the same of 3DCRT plans. The V45Gy of small bowels was in average 49.4cm3 in IMRT/VMAT plans, while in 3DCRT plans it was 211.6 cm3. In case of femoral head, significant reduction in V30Gy (10.8 % vs. 33.1%) and mean dose in case of IMRT/VMAT plans was recorded (30.4 Gy in 3DCRT vs 23.6 Gy). Rectum was planned with significantly lower dose in terms of V30Gy (79.5% vs 95.2%) in IMRT/VMAT plans. Bladder was better spared in VMAT plans in terms of V40Gy (51% vs. 91%), but maximum dose was higher in VMAT plans than in 3DCRT (50.1 Gy to 48.1 Gy in average). For all OARs there is statistically significant difference registered at p>0.05. Toxicities recorded in VMAT and 3DCRT patients include mainly radiation induced cystitis and enteritis. Patients treated with 3DCRT generally have longer recovery time. Homogeneity index was 0.11 for VMAT plans and 0.09 for 3DCRT plans. Conclusions. Analysis of dosimetric parameters revealed significant differences in normal tissue doses for same 3DCRT and VMAT patient, which confirmed necessity for implementation of advanced techniques for as many patients as possible.

scholarly journals A Comparative Study of Auto-contouring Softwares in Delineation of Organs at Risk in Lung Cancer and Rectal Cancer

2021 ◽  
Author(s):  
weijun chen ◽  
Cheng Wang ◽  
Wenming Zhan ◽  
Yongshi Jia ◽  
Fangfang Ruan ◽  
...  
Keyword(s):  
Lung Cancer ◽  
At Risk ◽  
Rectal Cancer ◽  
Organs At Risk ◽  
Similarity Index ◽  
Slight Modification ◽  
Ct Images ◽  
Target Area ◽  
Ct Image ◽  
Significant Difference

Abstract Background:Radiotherapy requires the target area and the organs at risk to be contoured on the CT image of the patient. During the process of organs-at-Risk (OAR) of the chest and abdomen, the doctor needs to contour at each CT image. The delineations of large and varied shapes are time-consuming and laborious.This study aims to evaluate the results of two automatic contouring software on OAR definition of CT images of lung cancer and rectal cancer patients. Methods: The CT images of 15 patients with rectal cancer and 15 patients with lung cancer were selected separately, and the organs at risk were outlined by the same experienced doctor as references, and then the same datasets were automatically contoured based on AiContour®© (Manufactured by Linking MED, China) and Raystation®© (Manufactured by Raysearch, Sweden) respectively. Overlap index (OI), Dice similarity index (DSC) and Volume difference (DV) were evaluated based on the auto-contours, and independent-sample t-test analysis is applied to the results. Results: The results of AiContour®© on OI and DSC were better than that of Raystation®© with statistical difference. There was no significant difference in DV between the results of two software. Conclusions: With AiContour®©, auto-contouring results of most organs in the chest and abdomen are good, and with slight modification, it can meet the clinical requirements for planning. With Raystation®©, auto-contouring results in most OAR is not as good as AiContour®©, and only the auto-contouring results of some organs can be used clinically after modification.

scholarly journals Can volumetric modulated arc radiation therapy reduce organ at risk dose in stage 4 sinonasal tumors in dogs treated with boost irradiation?

PLoS ONE ◽  
2021 ◽  
Vol 16 (10) ◽  
pp. e0259112
Author(s):  
Valeria Meier ◽  
Felicitas Czichon ◽  
Linda Walsh ◽  
Carla Rohrer Bley
Keyword(s):  
At Risk ◽  
Radiation Therapy ◽  
Degrees Of Freedom ◽  
Organs At Risk ◽  
Volumetric Modulated Arc Therapy ◽  
Intensity Modulated Radiation Therapy ◽  
Target Volume ◽  
Normal Tissue Complication Probability ◽  
Lacrimal Glands ◽  
Stage 4

Intensity modulated radiation therapy (IMRT) introduced marked changes to cancer treatment in animals by reducing dose to organs at risk (OAR). As the next technological step, volumetric modulated arc therapy (VMAT) has advantages (increased degrees-of-freedom, faster delivery) compared to fixed-field IMRT. Our objective was to investigate a possible advantage of VMAT over IMRT in terms of lower OAR doses in advanced-disease sinonasal tumors in dogs treated with simultaneously-integrated boost radiotherapy. A retrospective, analytical, observational study design was applied using 10 pre-existing computed tomography datasets on dogs with stage 4 sinonasal tumors. Each dataset was planned with both, 5-field IMRT and 2 arc VMAT with 10x4.83 Gy to the gross tumor volume and 10x4.2 Gy to the planning target volume. Adequate target dose coverage and normal tissue complication probability of brain ≤5% was required. Dose constraints aspired to were D60 <15 Gy for eyes, D2 <35.4 Gy for corneae, and Dmean <20 Gy for lacrimal glands. OAR dose was statistically significantly higher in IMRT plans than in VMAT plans. Median eye D60% was 18.5 Gy (interquartile range (IQR) 17.5) versus 16.1 Gy (IQR 7.4) (p = 0.007), median lacrimal gland dose 21.8 Gy (IQR 20.5) versus 18.6 Gy (IQR 7.0) (p = 0.013), and median cornea D2% 45.5 Gy (IQR 6.8) versus 39.9 Gy (IQR 10.0) (p<0.005) for IMRT versus VMAT plans, respectively. Constraints were met in 21/40 eyes, 7/40 corneae, and 24/40 lacrimal glands. Median delivery time was significantly longer for IMRT plans than for VMAT plans (p<0.01). Based on these results, VMAT plans were found to be superior in sparing doses to eyes, lacrimal glands, corneae. However, not all ocular OAR constraints could be met while ensuring adequate dose coverage and restricting brain toxicity risk for both planning techniques.

Evaluation of plan optimisers in prostate VMAT using the dose distribution index

2019 ◽  
Vol 18 (4) ◽  
pp. 323-328 ◽  
Author(s):  
James C. L. Chow ◽  
Runqing Jiang ◽  
Lu Xu
Keyword(s):  
At Risk ◽  
Dose Distribution ◽  
Organs At Risk ◽  
Volumetric Modulated Arc Therapy ◽  
Target Volume ◽  
Weighting Factor ◽  
Target Coverage ◽  
Dose Volume Histograms ◽  
Dose Volume ◽  
Distribution Index

AbstractPurpose:Dose distribution index (DDI) is a treatment planning evaluation parameter, reflecting dosimetric information of target coverage that can help to spare organs at risk (OARs) and remaining volume at risk (RVR). The index has been used to evaluate and compare prostate volumetric modulated arc therapy (VMAT) plans using two different plan optimisers, namely photon optimisation (PO) and its predecessor, progressive resolution optimisation (PRO).Materials and methods:Twenty prostate VMAT treatment plans were created using the PO and PRO in this retrospective study. The 6 MV photon beams and a dose prescription of 78 Gy/39 fractions were used in plans with the same dose–volume criteria for plan optimisation. Dose–volume histograms (DVHs) of the planning target volume (PTV), as well as of OARs such as the rectum, bladder, left and right femur were determined in each plan. DDIs were calculated and compared for plans created by the PO and PRO based on DVHs of the PTV and all OARs.Results:The mean DDI values were 0·784 and 0·810 for prostate VMAT plans created by the PO and PRO, respectively. It was found that the DDI of the PRO plan was about 3·3% larger than the PO plan, which means that the dose distribution of the target coverage and sparing of OARs in the PRO plan was slightly better. Changing the weighting factors in different OARs would vary the DDI value by ∼7%. However, for plan comparison based on the same set of dose–volume criteria, the effect of weighting factor can be neglected because they were the same in the PO and PRO.Conclusions:Based on the very similar DDI values calculated from the PO and PRO plans, with the DDI value in the PRO plan slightly larger than that of the PO, it may be concluded that the PRO can create a prostate VMAT plan with slightly better dose distribution regarding the target coverage and sparing of OARs. Moreover, we found that the DDI is a simple and comprehensive dose–volume parameter for plan evaluation considering the target, OARs and RVR.

scholarly journals Stereotactic ablative radiotherapy for ultra-central lung tumors: prioritize target coverage or organs at risk?

2018 ◽  
Vol 13 (1) ◽  
Author(s):  
Donna H. Murrell ◽  
Joanna M. Laba ◽  
Abigail Erickson ◽  
Barbara Millman ◽  
David A. Palma ◽  
...  
Keyword(s):  
At Risk ◽  
Organs At Risk ◽  
Lung Tumors ◽  
Stereotactic Ablative Radiotherapy ◽  
Target Coverage
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