scholarly journals EP-1923: Integration of microscopic spread and geometric uncertainties into a single target volume expansion

2018 ◽  
Vol 127 ◽  
pp. S1045-S1046
Author(s):  
E. Sterpin ◽  
K. Haustermans ◽  
M. Lambrecht ◽  
X. Geets ◽  
T. Mackie ◽  
...  
Keyword(s):  
Volume Expansion ◽  
Target Volume ◽  
Geometric Uncertainties ◽  
Single Target

scholarly journals Impact of Geometric Uncertainties on Dose Distribution During Intensity Modulated Radiotherapy of Head-and-neck Cancer: The Need for a Planning Target Volume and A Planning Organ-at-Risk Volume

2006 ◽  
Vol 13 (3) ◽  
pp. 108-115 ◽  
Author(s):  
O. Ballivy ◽  
W. Parker ◽  
T. Vuong ◽  
G. Shenouda ◽  
H. Patrocinio
Keyword(s):  
Spinal Cord ◽  
At Risk ◽  
Neck Cancer ◽  
Intensity Modulated Radiotherapy ◽  
Target Volume ◽  
Ct Scans ◽  
Target Coverage ◽  
Geometric Uncertainties ◽  
Intensity Modulated ◽  
Organ At Risk

We assessed the effect of geometric uncertainties on target coverage and on dose to the organs at risk (OARS) during intensity-modulated radiotherapy (IMRT) for head-and-neck cancer, and we estimated the required margins for the planning target volume (PTV) and the planning organ-at-risk volume (PRV). For eight headand- neck cancer patients, we generated IMRT plans with localization uncertainty margins of 0 mm, 2.5 mm, and 5.0 mm. The beam intensities were then applied on repeat computed tomography (CT) scans obtained weekly during treatment, and dose distributions were recalculated. The dose–volume histogram analysis for the repeat CT scans showed that target coverage was adequate (V100 ≥ 95%) for only 12.5% of the gross tumour volumes, 54.3% of the upper-neck clinical target volumes (CTVS), and 27.4% of the lower-neck CTVS when no margins were added for PTV. The use of 2.5-mm and 5.0-mm margins significantly improved target coverage, but the mean dose to the contralateral parotid increased from 25.9 Gy to 29.2 Gy. Maximum dose to the spinal cord was above limit in 57.7%, 34.6%, and 15.4% of cases when 0-mm, 2.5-mm, and 5.0-mm margins (respectively) were used for PRV. Significant deviations from the prescribed dose can occur during IMRT treatment delivery for headand- neck cancer. The use of 2.5-mm to 5.0-mm margins for PTV and PRV greatly reduces the risk of underdosing targets and of overdosing the spinal cord.

Comparison of geometric uncertainties between alpha cradle and thermoplastic ray cast immobilisation in abdominopelvic radiotherapy: a prospective study

2011 ◽  
Vol 11 (4) ◽  
pp. 239-248 ◽  
Author(s):  
Saikat Das ◽  
Subhashini John ◽  
Paul Ravindran ◽  
Rajesh Isiah ◽  
Rajesh B ◽  
...  
Keyword(s):  
Random Error ◽  
Systematic Errors ◽  
Target Volume ◽  
Reference Image ◽  
Ratio Test ◽  
Setup Error ◽  
Random Errors ◽  
Geometric Uncertainties ◽  
The Difference ◽  
Portal Images

AbstractContext: Setup error significantly affects the accuracy of treatment and outcome in high precision radiotherapy.Aims: To determine total, systematic, random error and clinical target volume (CTV) to planning target volume (PTV) margin with alpha cradle (VL) and ray cast (RC) immobilisation in abdominopelvic region.Methods and material: Setup error was compared by using digitally reconstructed radiograph (DRR) as reference image with electronic portal image (EPI) taken during the treatment. Statistical analysis used: The total errors in mediolateral (ML), craniocaudal (CC) and anteroposterior (AP) directions were compared by t-test. For systematic and random errors variance ratio test (F-statistics) was used. Margins were calculated using International Commission of Radiation Units (ICRU), Stroom’s and van Herk’s formula.Results: A total number of 306 portal images were analysed with 144 images in RC group and 162 images in VL group. For VL, in ML, CC, AP directions systematic errors were, in cm, (0.45, 0.29, 0.41), random errors (0.48, 0.32, 0.58), CTV to PTV margins (1.24, 0.80, 1.25), respectively. For RC, systematic errors were (0.25, 0.37, 0.80), random error (0.46, 0.80, 0.33), CTV to PTV margins (0.82, 1.30, 1.08), respectively. The difference of random error in CC and AP directions were statistically significant.Conclusions: Geometric errors and CTV to PTV margins are different in different directions. For abdomen and pelvis in VL immobilisation, the margin ranged from 8 mm to 12.4 mm and for RC it was 8.2 mm to 13 mm. Therefore, a margin of 10 mm with online correction would be adequate.

Evaluation of Breast Target Volume Expansion using Deep Inspiratory Breath Hold

2009 ◽  
Vol 75 (3) ◽  
pp. S122-S123
Author(s):  
A.F. McIntosh ◽  
A. Shoushtari ◽  
S. Benedict ◽  
P.W. Read ◽  
K. Wijesooriya
Keyword(s):  
Volume Expansion ◽  
Target Volume ◽  
Breath Hold

scholarly journals Comparison of radiation dose spillage from the Gamma Knife Perfexion with that from volumetric modulated arc radiosurgery during treatment of multiple brain metastases in a single fraction

2014 ◽  
Vol 121 (Suppl_2) ◽  
pp. 51-59 ◽  
Author(s):  
Daniel McDonald ◽  
John Schuler ◽  
Istvan Takacs ◽  
Jean Peng ◽  
Joseph Jenrette ◽  
...  
Keyword(s):  
Volume Expansion ◽  
Tumor Volume ◽  
Target Volume ◽  
Quality Metrics ◽  
Normal Brain ◽  
Gradient Index ◽  
Prescription Dose ◽  
Gamma Knife Perfexion ◽  
Prescription Isodose ◽  
Brain Tissues

ObjectThe objective of this study was to examine radiation dose distributions created by 2 competing radiosurgery modalities for treating multiple brain metastases: single-isocenter volumetric modulated arc radiosurgery (VMAS) and Gamma Knife Perfexion (GKP). In addition, the effectiveness of multiple radiosurgery quality metrics was evaluated and compared between these advanced treatment modalities.MethodsSeven anonymized MRI data sets, each showing 2–5 metastases, were used to create plans on each system. The GammaPlan (version 10.1) program was used for planning of GKP. A neurosurgeon contoured the volumes to be treated, and no planning target volume expansion was used. A prescription dose coverage of ≥ 99% was achieved for each tumor volume. The Philips Pinnacle (version 9.2) program was used for planning of VMAS, using the SmartArc optimization algorithm for delivery on a Varian iX linear accelerator. Contours were transferred from GammaPlan, and again no planning target volume expansion was used. Between 2 and 5 arcs with table angles of 90°–270° were used. Again, a V100% of ≥ 99% was achieved for each tumor volume. After planning, the MRI scans, tumor volumes, and dose information from each plan were exported according to the Digital Imaging and Communications in Medicine standard to the VelocityAI program for analysis. Brain dose-volume histograms (DVHs) for normal brain tissues were generated, and the volume of these tissues receiving 20%–90% of the prescription dose was tabulated. Finally, the prescription isodose to tumor volume ratio (PITV; Shaw et al., 1993), conformity index (CI; Paddick, 2000), gradient index (GI, Paddick and Lippitz, 2006), and conformity/gradient index (CGI, Wagner et al. 2003) were calculated for each plan. Both the PITV and CI have ideal values of 1, while the GI and CGI have ideal values of lowest and highest achievable, respectively.ResultsThe DVHs consistently showed that with VMAS a higher amount of normal brain tissues received each dose level than with GKP. These increases were largest for lower isodose levels, with the volumes of normal brain that received 20%–50% and 60%–90% of the prescription dose showing average increases of 403% and 227%, respectively. Prescription isodose conformality showed only minor differences between the 2 modalities. Radiosurgery quality metrics including measures of the dose gradient (GI and CGI) indicated that the GKP plan was superior in each case, with respective average GI and CGI values of 3.04 and 57.75 for GKP and of 10.22 and 10.85 for VMAS. Metrics evaluating prescription isodose conformality alone differed only slightly between the modalities. Average respective PITV and CI values were 2.13 and 0.53 for GKP and 2.27 and 0.51 for VMAS.ConclusionsStereotactic radiosurgery plans for the treatment of multiple metastases with VMAS delivered significantly more dose to the normal brain tissues than plans for GKP. Radiosurgery quality metrics including a measure of the dose gradient are better suited to providing contrast between modern radiosurgery treatment platforms.

scholarly journals Reducing radiotherapy target volume expansion for patients with HPV-associated oropharyngeal cancer

Oral Oncology ◽  
2019 ◽  
Vol 92 ◽  
pp. 52-56 ◽  
Author(s):  
Adam R. Burr ◽  
Paul M. Harari ◽  
Huaising C. Ko ◽  
Justine Y. Bruce ◽  
Randall J. Kimple ◽  
...  
Keyword(s):  
Oropharyngeal Cancer ◽  
Volume Expansion ◽  
Target Volume

scholarly journals Random and systematic set-up errors in three-dimensional conformal radiotherapy – impact on planning target volume margins: the experience of the Radiation Oncology Centre of Sassari

2013 ◽  
Vol 13 (2) ◽  
pp. 166-179
Author(s):  
Matteo Tamponi ◽  
Angela Poggiu ◽  
Maria F. Dedola ◽  
Rossella Madeddu ◽  
Antonella Carnevale ◽  
...  
Keyword(s):  
Planning Target Volume ◽  
Three Dimensional ◽  
Conformal Radiotherapy ◽  
Target Volume ◽  
Patient Specific ◽  
Geometric Uncertainties ◽  
Three Dimensional Conformal Radiotherapy ◽  
Set Up ◽  
Oncology Centre ◽  
The Impact

AbstractPurposeGeometric uncertainties limit the accuracy of three-dimensional conformal radiotherapy treatments. This study aims to evaluate typical random and systematic set-up errors and analyse the impact of no action level (NAL) correction protocol on systematic set-up errors and clinical target volume (CTV)–planning target volume (PTV) margins.Materials and methodsA total 668 pairs of orthogonal electronic portal images were compared with digitally reconstructed radiographs from computed tomography planning scans for 100 patients consecutively treated during 2011. Patients were divided into groups depending on the treated anatomical region. Patient-specific and population random and systematic set-up errors were calculated. Impact of application of NAL correction protocol on systematic set-up errors and CTV–PTV expansions were evaluated.ResultsPopulation set-up errors resulted from about 1 mm in head and neck to 2–3 mm in prostate, rectum, lung, breast and gynaecological districts. Patient-specific systematic set-up errors were higher for breast and gynaecological districts and application of NAL correction protocol gave significant reductions, even higher than 30%. Calculated CTV–PTV margins ranged from 10 mm on left–right direction for prostate to 20 mm on superior–inferior direction for lung.ConclusionsSet-up errors resulted reasonably controlled and application of NAL correction protocol could further improve the level of accuracy. However, the NAL application alone did not seem to add any substantial benefit on CTV–PTV total margins without the adoption of corrective strategies to reduce other important uncertainties limiting accuracy of three-dimensional conformal radiotherapy.

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