scholarly journals Evidence-based planning target volume (PTV) margin reduction for modern lung stereotactic ablative radiotherapy (SABR) using deformable registration

2021 ◽  
pp. 100750
Author(s):  
Katie Jasper ◽  
Baochang Liu ◽  
Robert Olson ◽  
Quinn Matthews
Keyword(s):  
Planning Target Volume ◽  
Target Volume ◽  
Deformable Registration ◽  
Stereotactic Ablative Radiotherapy ◽  
Evidence Based ◽  
Ptv Margin

scholarly journals Dosimetric effects of adaptive prostate cancer radiotherapy in an MR-linac workflow

2020 ◽  
Vol 15 (1) ◽  
Author(s):  
Annika Mannerberg ◽  
Emilia Persson ◽  
Joakim Jonsson ◽  
Christian Jamtheim Gustafsson ◽  
Adalsteinn Gunnlaugsson ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Planning Target Volume ◽  
Dose Distribution ◽  
Time Frame ◽  
Target Volume ◽  
Anatomical Changes ◽  
Ptv Margin ◽  
Significant Difference ◽  
Adaptive Replanning ◽  
Treatment Plans

Abstract Background The purpose was to evaluate the dosimetric effects in prostate cancer treatment caused by anatomical changes occurring during the time frame of adaptive replanning in a magnetic resonance linear accelerator (MR-linac) workflow. Methods Two MR images (MR1 and MR2) were acquired with 30 min apart for each of the 35 patients enrolled in this study. The clinical target volume (CTV) and organs at risk (OARs) were delineated based on MR1. Using a synthetic CT (sCT), ultra-hypofractionated VMAT treatment plans were created for MR1, with three different planning target volume (PTV) margins of 7 mm, 5 mm and 3 mm. The three treatment plans of MR1, were recalculated onto MR2 using its corresponding sCT. The dose distribution of MR2 represented delivered dose to the patient after 30 min of adaptive replanning, omitting motion correction before beam on. MR2 was registered to MR1, using deformable registration. Using the inverse deformation, the structures of MR1 was deformed to fit MR2 and anatomical changes were quantified. For dose distribution comparison the dose distribution of MR2 was warped to the geometry MR1. Results The mean center of mass vector offset for the CTV was 1.92 mm [0.13 – 9.79 mm]. Bladder volume increase ranged from 12.4 to 133.0% and rectum volume difference varied between −10.9 and 38.8%. Using the conventional 7 mm planning target volume (PTV) margin the dose reduction to the CTV was 1.1%. Corresponding values for 5 mm and 3 mm PTV margin were 2.0% and 4.2% respectively. The dose to the PTV and OARs also decreased from D1 to D2, for all PTV margins evaluated. Statistically significant difference was found for CTV Dmin between D1 and D2 for the 3 mm PTV margin (p < 0.01). Conclusions A target underdosage caused by anatomical changes occurring during the reported time frame for adaptive replanning MR-linac workflows was found. Volume changes in both bladder and rectum caused large prostate displacements. This indicates the importance of thorough position verification before treatment delivery and that the workflow needs to speed up before introducing margin reduction.

scholarly journals Does size matter? Investigating the optimal planning target volume margin for postoperative stereotactic radiosurgery to resected brain metastases

2019 ◽  
Vol 130 (3) ◽  
pp. 797-803 ◽  
Author(s):  
Jaymin Jhaveri ◽  
Mudit Chowdhary ◽  
Xinyan Zhang ◽  
Robert H. Press ◽  
Jeffrey M. Switchenko ◽  
...  
Keyword(s):  
Local Recurrence ◽  
Brain Metastases ◽  
Stereotactic Radiosurgery ◽  
Planning Target Volume ◽  
Group Performance ◽  
Multivariate Analyses ◽  
Target Volume ◽  
Single Fraction ◽  
Ptv Margin ◽  
Size Matter

OBJECTIVEThe optimal margin size in postoperative stereotactic radiosurgery (SRS) for brain metastases is unknown. Herein, the authors investigated the effect of SRS planning target volume (PTV) margin on local recurrence and symptomatic radiation necrosis postoperatively.METHODSRecords of patients who received postoperative LINAC-based SRS for brain metastases between 2006 and 2016 were reviewed and stratified based on PTV margin size (1.0 or > 1.0 mm). Patients were treated using frameless and framed SRS techniques, and both single-fraction and hypofractionated dosing were used based on lesion size. Kaplan-Meier and cumulative incidence models were used to estimate survival and intracranial outcomes, respectively. Multivariate analyses were also performed.RESULTSA total of 133 patients with 139 cavities were identified; 36 patients (27.1%) and 35 lesions (25.2%) were in the 1.0-mm group, and 97 patients (72.9%) and 104 lesions (74.8%) were in the > 1.0–mm group. Patient characteristics were balanced, except the 1.0-mm cohort had a better Eastern Cooperative Group Performance Status (grade 0: 36.1% vs 19.6%), higher mean number of brain metastases (1.75 vs 1.31), lower prescription isodose line (80% vs 95%), and lower median single fraction–equivalent dose (15.0 vs 17.5 Gy) (all p < 0.05). The median survival and follow-up for all patients were 15.6 months and 17.7 months, respectively. No significant difference in local recurrence was noted between the cohorts. An increased 1-year rate of symptomatic radionecrosis was seen in the larger margin group (20.9% vs 6.0%, p = 0.028). On multivariate analyses, margin size > 1.0 mm was associated with an increased risk for symptomatic radionecrosis (HR 3.07, 95% CI 1.13–8.34; p = 0.028), while multifraction SRS emerged as a protective factor for symptomatic radionecrosis (HR 0.13, 95% CI 0.02–0.76; p = 0.023).CONCLUSIONSExpanding the PTV margin beyond 1.0 mm is not associated with improved local recurrence but appears to increase the risk of symptomatic radionecrosis after postoperative SRS.

Planning target volume (PTV) margin practice patterns in adults and paediatrics among the Paediatric Radiation Oncology Society (PROS) members: an international survey

2018 ◽  
Vol 17 (4) ◽  
pp. 368-372
Author(s):  
Mohamed N. ElBeltagi ◽  
Verna Wall ◽  
Laure Marignol
Keyword(s):  
Planning Target Volume ◽  
Radiation Oncology ◽  
Target Volume ◽  
International Survey ◽  
Head Region ◽  
Ptv Margin ◽  
Paediatric Patients ◽  
Comprehensive Survey ◽  
The Difference ◽  
Patterns Of Practice

AbstractAimEvolving data are showing the need of considering smaller planning target volume (PTV) margin in paediatrics compared with adults treated for the same body site. This study proposed to evaluate the current patterns of practice regarding the PTV margin in paediatric patients compared with adult patients through an international survey.Materials and methodsA four-item questionnaire was created to address the PTV margins for paediatrics and adults as part of a comprehensive survey. International Paediatric Radiation Oncology Society (PROS) members were selected to partake and were contacted via email.ResultsIn total, 43 responded to the survey. The majority of the responders have written guidelines for PTV margin while the majority of those who have guidelines do not have separate guidelines for paediatrics. The implemented PTV margin for paediatric patients was in the majority 3–5 mm for the head region and 5–10 mm for the torso region and the difference from the PTV margin implemented in adults was not statistically significant.ConclusionThe majority of responders employ a series of site-specific PTV margin protocols that are applied to both adults and paediatrics, and do not take into consideration patient age or size. These results highlight the need of a separate policy for PTV margin in adults and paediatrics in every institution.

A cone beam CT-based study on fiducial seed migration and planning target volume margin in prostate radiotherapy

2019 ◽  
Vol 19 (4) ◽  
pp. 315-320
Author(s):  
Divya K. Thuruthiyil ◽  
Martin Cawley ◽  
Mohamed Metwaly
Keyword(s):  
Planning Target Volume ◽  
Cone Beam Ct ◽  
Target Volume ◽  
Cone Beam ◽  
Setup Error ◽  
Setup Errors ◽  
Prostate Radiotherapy ◽  
Ptv Margin ◽  
Seed Migration ◽  
Random Components

AbstractAim:This study attempts to investigate fiducial marker (FM) migration and calculate the prostate planning target volume (PTV) margin considering the setup errors after translation corrections alone (T) and translation plus rotational corrections (T+R) and anatomy variation with respect to the corrected fiducial position, analysed on cone beam computed tomography (CBCT) images.Methods and materials:CBCT images from 25 patients are analysed for FM movements, setup error and anatomy variation with respect to the seed match positions. Systematic and random components of setup error and prostate movements are used to calculate the PTV margin for CBCT-based FM localisation in two scenarios, translation corrections only and translation plus rotational correction. MTNW887825 soft tissue gold markers (Civco, Orange City, FL, USA) were used with the department-specific immobilisation system and rectal and bladder filling protocols.Results:The average directional inter-marker distance variation is −0·05 ± 0·90 mm. The systematic setup errors for T+R are 0·40, 0·63 and 0·80 mm in right–left (RL), anterior–posterior (AP) and superior–inferior (SI), respectively. The corresponding values for T only are 0·54, 0·69 and 0·90 mm. The systematic prostate movement from T+R corrected FM positions are 0·65, 1·27 and 1·32 mm in the RL, AP and SI directions.Findings:Minimal FM movements are noted from the study. The PTV margins to incorporate the daily T+R corrected setup error and prostate deformation are found to be 2·5, 4·5 and 5·2 mm in the RL, AP and SI directions, respectively. The corresponding margins for T only corrected scenario are found to be 2·8, 4·8 and 5·7 mm.

scholarly journals Impact of Four-Dimensional Cone-Beam Computed Tomography on Target Localization for Gastric Mucosa-Associated Lymphoid Tissue Lymphoma Radiotherapy: Reducing Planning Target Volume Margin

2020 ◽  
Author(s):  
Yoshinobu Shimohigashi ◽  
Ryo Toya ◽  
Tetsuo Saito ◽  
Yumiko Kono ◽  
Yasuhiro Doi ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Soft Tissue ◽  
Gastric Mucosa ◽  
Planning Target Volume ◽  
Lymphoid Tissue ◽  
Target Volume ◽  
Target Localization ◽  
Cone Beam ◽  
Ptv Margin ◽  
Dimensional Cone

Abstract Background: Radiotherapy of gastric mucosa-associated lymphoid tissue (MALT) lymphoma should be delivered to the whole stomach with optimal planning target volume (PTV) margins that account for variations in stomach volume, respiratory movement, and patient set-up error. In this study, we evaluated whether the use of four-dimensional cone-beam computed tomography (4D-CBCT) reduces the PTV margin.Methods: Eight patients underwent radiotherapy with 15 fractions of gastric MALT lymphoma using 4D-CBCT. Structures with PTV margins of 5–30 mm (5 mm intervals) from the internal target volume of the stomach defined based on the 4D-CT images were generated. For the target localization, we performed matching based on skin marking (skin matching), bone anatomy (bone matching), and stomach anatomy (4D soft-tissue matching) based on registration between planning CT and 4D-CBCT images from 10 phases. For each patient, we calculated the covering ratio (CR) of the stomach with variable PTV margins, based on the 4D-CBCT images, with a total of 150 phases [CR (%) = (number of covering phases / 150 phases) × 100], for three target localization methods. We compared the CR values of the different target localization methods and defined a minimal PTV margin with an average CR of ≥ 95 % for all patients as optimal.Results: The average CR for all patients increased from 17.9 % to 100 %, 19.6 % to 99.8 %, and 33.8 % to 100 %, in the skin, bone, and 4D soft-tissue matchings, respectively, as the PTV margins increased from 5 to 30 mm. The CR obtained by 4D soft-tissue matching was superior to that obtained by skin (P = 0.013) and bone matching (P = 0.008) for a PTV margin of 15 mm. The optimal PTV margins were 20 mm (average CR: 95.2 %), 25 mm (average CR: 99.1 %), and 15 mm (average CR: 98.0 %) for the skin, bone, and 4D soft-tissue matchings, respectively.Conclusions: This study demonstrates that the use of 4D-CBCT reduces the PTV margin when applying 4D soft-tissue matching, compared to skin and bone matchings. Additionally, bone matching does not reduce the PTV margin as compared with traditional skin matching.

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