scholarly journals Analytical setup margin for spinal stereotactic body radiotherapy based on measured errors

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Audrey Copeland ◽  
Addie Barron ◽  
Jonas Fontenot
Keyword(s):  
Spinal Cord ◽  
Volumetric Modulated Arc Therapy ◽  
Surface Displacement ◽  
Target Volume ◽  
Three Dimensions ◽  
Setup Error ◽  
Intrafraction Motion ◽  
Negative Effect ◽  
Prescription Dose ◽  
End To End

Abstract Background No consensus currently exists about the correct margin size to use for spinal SBRT. Margins have been proposed to account for various errors individually, but not with all errors combined to result in a single margin value. The purpose of this work was to determine a setup margin for five-fraction spinal SBRT based on known errors during radiotherapy to achieve at least 90% coverage of the clinical target volume with the prescription dose for at least 90% of patients and not exceed a 30 Gy point dose or 23 Gy to 10% of the spinal cord subvolume. Methods The random and systematic error components of intrafraction motion, residual setup error, and end-to-end system accuracy were measured. The patient’s surface displacement was measured to quantify intrafraction motion, the residual setup error was quantified by re-registering accepted daily cone beam computed tomography setup images, and the displacement between measured and planned dose profiles in a phantom quantified the end-to-end system accuracy. These errors and parameters were used to identify the minimum acceptable margin size. The margin recommendation was validated by assessing dose delivery across 140 simulated patient plans suffering from various random shifts representative of the measured errors. Results The errors were quantified in three dimensions and the analytical margin generated was 2.4 mm. With this margin applied in the superior/inferior direction only, at least 90% of the CTV was covered with the prescription dose for 96% of the 140 patients simulated with minimal negative effect on the spinal cord dose levels. Conclusions The findings of this work support that a 2.4 mm margin applied in the superior/inferior direction can achieve at least 90% coverage of the CTV for at least 90% of dual-arc volumetric modulated arc therapy spinal SBRT patients in the presence of errors when immobilized with vacuum bags.

scholarly journals Paradigmaváltás szükségessége a sugárterápiában

2015 ◽  
Vol 156 (44) ◽  
pp. 1763-1768
Author(s):  
Árpád Mayer ◽  
Csilla Katona ◽  
Róbert Farkas ◽  
Zsuzsa Póti
Keyword(s):  
Spinal Cord ◽  
Radiation Injury ◽  
Volumetric Modulated Arc Therapy ◽  
Target Volume ◽  
Intensity Modulated ◽  
The Past ◽  
Arc Therapy ◽  
Intracranial Metastases ◽  
The Status ◽  
Radiotherapy Treatment

The status and indications of radiotherapy have significantly changed in the past decade because novel techniques, radiobiological research and major advances in informatics have made better local control possible. Using supplemented marking of the target volume with computer tomography based other image-making methods adapted made it possible to define the tumor and intact surrounding tissues more precisely. With novel radiotherapy techniques the dosage of the homogenity and the covering in the target volume can be raised optimally, especially with intensity modulated arc radiotherapy (volumetric modulated arc therapy) without causing radiation injury or damage to intact surrounding tissues. Furthermore, with novel techniques and target volume marking, new indications have appeared in clinical practice and besides sterotactic radiotherapy for intracranial metastases, the extracranial so-called oligometastic conditions can be maintained close to a curative state (or in remission) for many years. Among these, perhaps the most striking is the stereotactic radiotherapy treatment of liver, lung and spinal cord metastases in one or more fractions, for which the indispensable condition is the image or respiratory guided technique. Orv. Hetil., 2015, 156(44), 1763–1768.

scholarly journals Combined effect of dose gradient and rotational error on prescribed dose coverage for single isocenter multiple brain metastases in frameless stereotactic radiotherapy

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Jai-Woong Yoon ◽  
Soah Park ◽  
Kwang-Ho Cheong ◽  
Sei-Kwon Kang ◽  
Tae Jin Han
Keyword(s):  
Stereotactic Radiotherapy ◽  
Volumetric Modulated Arc Therapy ◽  
Target Volume ◽  
Ct Images ◽  
Combined Effect ◽  
Three Dimensions ◽  
Target Coverage ◽  
Rotational Error ◽  
Brain Radiotherapy ◽  
Small Targets

Abstract Background To evaluate the combined effect of rotational error and dose gradient on target dose coverage in frameless stereotactic radiotherapy. Methods Three spherical targets of different diameters (1, 1.5, and 2 cm) were drawn and placed equidistantly on the same axial brain computed tomography (CT) images. To test the different isocenter-target distances, 2.5- and 5-cm configurations were prepared. Volumetric modulated arc therapy plans were created for different dose gradients from the target, in which the dose gradients were modified using the maximum dose inside the target. To simulate the rotational error, CT images and targets were rotated in two ways by 0.5°, 1°, and 2°, in which one rotation was in the axial plane and the other was in three dimensions. The initial optimized plan parameters were copied to the rotated CT sets, and the doses were recalculated. The coverage degradation after rotation was analyzed according to the target dislocation and 12-Gy volume. Results A shallower dose gradient reduced the loss of target coverage under target dislocation, and the effect was clearer for small targets. For example, the coverage of the 1-cm target under 1-mm dislocation increased from 93 to 95% by increasing the Paddick gradient index from 5.0 to 7.9. At the same time, the widely accepted necrosis indicator, the 12-Gy volume, increased from 1.2 to 3.5 cm3, which remained in the tolerable range. From the differential dose volume histogram (DVH) analysis, the shallower dose gradient ensured that the dose-deficient under-covered target volume received a higher dose similar to that in the prescription. Conclusions For frameless stereotactic brain radiotherapy, the gradient, alongside the margin addition, can be adjusted as an ancillary parameter for small targets to increase target coverage or at least limit coverage reduction in conditions with probable positioning error.

scholarly journals Dose-Volume Comparison of IMRT and PSPT Treatment Plans for Early-Stage Glottic Cancer

2020 ◽  
Vol 7 (2) ◽  
pp. 42-50
Author(s):  
Takahiro Kato ◽  
Nobukazu Fuwa ◽  
Masao Murakami
Keyword(s):  
Spinal Cord ◽  
Dose Distribution ◽  
Early Stage ◽  
Organs At Risk ◽  
Cricoid Cartilage ◽  
Thyroid Cartilage ◽  
Target Volume ◽  
Glottic Cancer ◽  
Volume Comparison ◽  
Prescription Dose

Abstract Purpose To clarify the dose distribution characteristics for early-stage glottic cancer by comparing the dose distribution between intensity-modulated radiation therapy (IMRT) and passive scattering proton therapy (PSPT) and to examine the usefulness of PSPT for early-stage glottic cancer. Materials and Methods Computed tomography datasets of 8 patients with T1-2 glottic cancer who had been treated by PSPT were used to create an IMRT plan in Eclipse with 7 fields and a PSPT plan in XiO-M with 2 fields. Organs at risk (OARs) included the carotid arteries, arytenoids, inferior constrictor muscles, strap muscles, thyroid cartilage, cricoid cartilage, and spinal cord. The prescription dose was 66 GyRBE in 33 fractions to the planning target volume (PTV). All plans were optimized such that 95% of the PTV received 90% of the prescription dose considering that the skin was slightly spared. Results The superiority of the PSPT was confirmed in all OARs. In the PSPT, the dose to the contralateral carotid artery and the spinal cord, which is slightly distant from the PTV, was dramatically reduced while maintaining the dose distribution uniformity of the PTV by comparison with IMRT. Conclusion PSPT for early-stage glottic cancer resulted in good target dose homogeneity and significantly spared the OARs as compared with the IMRT. PSPT is expected to be effective in reducing late effects and particularly useful for young people.

scholarly journals Is IMRT or VMAT superior or inferior to 3D conformal therapy in the treatment of lung cancer? A brief literature review

2021 ◽  
pp. 1-5
Author(s):  
Kazi T. Afrin ◽  
Salahuddin Ahmad
Keyword(s):  
Lung Cancer ◽  
Literature Review ◽  
Treatment Time ◽  
Volumetric Modulated Arc Therapy ◽  
Target Volume ◽  
Patient Comfort ◽  
Tumour Control ◽  
Intrafraction Motion ◽  
Conformal Therapy ◽  
3D Crt

Abstract Aim: To identify treatment outcome, dose uniformity, treatment time, toxicity among 3D conformal therapy (3D-CRT), intensity-modulated radiation therapy (IMRT), volumetric-modulated arc therapy (VMAT) for non-small-cell lung cancer (NSCLC) based on literature review. Methods: A literature search was conducted using PubMed/MEDLINE, BMC—part of Springer Nature, Google Scholar and iMEDPub Ltd with the following keywords for filtering: 3D-CRT, IMRT, VMAT, lung cancer, local control and radiobiology. A total of 14 publications were finally selected for the comparison of 3D-CRT, IMRT and VMAT to determine which technique is superior or inferior among these three. Results: Compared to 3D-CRT, IMRT delivers more precise treatment, has better conformal dose coverage to planning target volume (PTV) that covers gross tumour with microscopic extension, respiratory tumour motion and setup margin. 3D-CRT has large number of limitations: low overall survival (OS), large toxicity, secondary malignancies. Conclusions: It is difficult to choose the best technique for treating NSCLC due to patient conditions and technique availability. A high-precision treatment may improve tumour control probability (TCP) and patient’s quality of life. VMAT, whether superior or not, needs more clinical trials to treat NSCLC and requires longer dose optimisation time with the greatest benefit of rapid treatment delivery, improved patient comfort, reduced intrafraction motion and increased patient throughput compared to IMRT and 3D-CRT.

scholarly journals Longitudinal Grouping of Target Volumes for Volumetric-Modulated Arc Therapy of Multiple Brain Metastases

2021 ◽  
Vol 11 ◽  
Author(s):  
Yingjie Xu ◽  
Junjie Miao ◽  
Qingfeng Liu ◽  
Peng Huang ◽  
Pan Ma ◽  
...  
Keyword(s):  
Brain Metastases ◽  
Brain Tissue ◽  
Volumetric Modulated Arc Therapy ◽  
Target Volume ◽  
Normal Brain ◽  
Normal Brain Tissue ◽  
Arc Therapy ◽  
Target Volumes ◽  
Prescription Dose ◽  
Single Isocenter

PurposeTreatment of multiple brain metastases with single-isocenter volumetric modulated arc therapy causes unnecessary exposure to normal brain tissue. In this study, a longitudinal grouping method was developed to reduce such unnecessary exposure.Materials and MethodsThis method has two main aspects: grouping brain lesions longitudinally according to their longitudinal projection positions in beam’s eye view, and rotating the collimator to 90° to make the multiple leaf collimator leaves conform to the targets longitudinally group by group. For 11 patients with multiple (5–30) brain metastases, two single-isocenter volumetric modulated arc therapy plans were generated using a longitudinal grouping strategy (LGS) and the conventional strategy (CVS). The prescription dose was 52 Gy for 13 fractions. Dose normalization to 100% of the prescription dose in 95% of the planning target volume was adopted. For plan quality comparison, Paddick conformity and the gradient index of the planning target volume, and the mean dose, the V100%, V50%, V25%, and V10% volumes of normal brain tissue were calculated.ResultsThere were no significant differences between the LGS and CVS plans in Paddick conformity (p = 0.374) and the gradient index (p = 0.182) of the combined planning target volumes or for V100% (p = 0.266) and V50% (p = 0.155) of the normal brain. However, the V25% and V10% of the normal brain which represented the low-dose region were significantly reduced in the LGS plans (p = 0.004 and p = 0.003, respectively). Consistently, the mean dose of the entire normal brain was 12.04 and 11.17 Gy in the CVS and LGS plans, respectively, a significant reduction in the LGS plans (p = 0.003).ConclusionsThe longitudinal grouping method can decrease unnecessary exposure and reduces the low-dose range in normal brain tissue.

Monte Carlo (MC)-based volumetric modulated arc therapy (VMAT) in locally advanced esophageal cancer with potential for dose escalation.

2014 ◽  
Vol 32 (3_suppl) ◽  
pp. 77-77
Author(s):  
Shaakir Hasan ◽  
Anil Sethi ◽  
Jennifer Breunig ◽  
Gabriel Axelrud ◽  
William Small ◽  
...  
Keyword(s):  
Dose Escalation ◽  
Organs At Risk ◽  
Locally Advanced ◽  
Volumetric Modulated Arc Therapy ◽  
Intensity Modulated Radiotherapy ◽  
Conformal Radiotherapy ◽  
Target Volume ◽  
Target Dose ◽  
Treatment Techniques ◽  
Prescription Dose

77 Background: Previous attempts at dose escalation in esophagus radiotherapy (RT), mostly based on older planning techniques, have not shown improved outcomes. We aimed to investigate the importance of newer, sophisticated dose algorithms and treatment techniques in escalating target dose and reducing dose to organs at risk (OAR). Methods: Treatment plans for 10 patients were retrospectively evaluated using 3D conformal radiotherapy (3DCRT), MC based intensity modulated radiotherapy (IMRT), and VMAT. Prescription dose was 45 Gy to the planning target volume (PTV) in 25 fractions followed by a 5.4 Gy boost in 3 fractions. PTV (mean±s.d. = 681±236 cc) were planned with BrainLab iPlan 4.1 software as IMRT and VMAT. Dose distributions were calculated with both pencil beam (PB) and MC algorithms. Each PTV was normalized to receive at least 95% of 50.4 Gy or 60 Gy dose. OARs were evaluated as per RTOG1010 dose guidelines. Paired t-tests were used for statistical analysis. Results: IMRT vs. 3DCRT PTV 50.4 Gy: IMRT plans decreased heart and lung average Dmean by 4.7 Gy (p = 0.053) and 1.9 Gy (p = 0.001) respectively when compared to 3DCRT. In addition, average values of lung V5, V10, and V30 also reduced by 7.1%, 5.5%, and 3.6% respectively (p < 0.05). There was a 12.1% decrease in heart V40 (p=0.053) and 3.7% reduction in liver V30 (p=0.08). PTV 60Gy: IMRT plans at 60 Gy led to lower OAR doses compared to 3DCRT at 50.4 Gy. MC based IMRT results did not significantly differ from PB, with the exception of lung V5 which was 4.4% higher (p <0.001). VMAT vs. IMRT PTV 50.4 Gy: VMAT based planning, compared to IMRT, lowered V20 (3.4%, p=0.029), V30 (1.6%, p = 0.013), and spinal cord Dmax (5.4 Gy, p = 0.001). However, lung Dmean, V5, and V10 increased by 1.2 Gy, 11.7%, 16.7% respectively (p < 0.001). PTV 60 Gy: With VMAT planning, all OAR dose parameters were within the RTOG 1010 limits, although lung V5 and V10 exceeded acceptable limits by 1.6% and 2.6% respectively. Conclusions: Compared to 3DCRT, target dose escalation with IMRT and VMAT is possible with improved OAR dose sparing, as evaluated with MC algorithms. Increased dose values for V5 and V10 as seen in MC based VMAT plans call for reassessment of RTOG 1010 guidelines.

scholarly journals Adaptive radiotherapy for head and neck cancer reduces the requirement for rescans during treatment due to spinal cord dose

2019 ◽  
Vol 14 (1) ◽  
Author(s):  
Louise Belshaw ◽  
Christina E. Agnew ◽  
Denise M. Irvine ◽  
Keith P. Rooney ◽  
Conor K. McGarry
Keyword(s):  
Spinal Cord ◽  
Head And Neck ◽  
Treatment Plan ◽  
Volumetric Modulated Arc Therapy ◽  
Target Volume ◽  
Adaptive Radiotherapy ◽  
Dose Increase ◽  
Volume Changes ◽  
Dose Volume Histograms ◽  
Dose Volume

Abstract Background Patients treated with radiotherapy for head and neck (H&N) cancer often experience anatomical changes. The potential compromises to Planning Target Volume (PTV) coverage or Organ at Risk (OAR) sparing has prompted the use of adaptive radiotherapy (ART) for these patients. However, implementation of ART is time and resource intensive. This study seeks to define a clinical trigger for H&N re-plans based on spinal cord safety using kV Cone-Beam Computed Tomography (CBCT) verification imaging, in order to best balance clinical benefit with additional workload. Methods Thirty-one H&N patients treated with Volumetric Modulated Arc Therapy (VMAT) who had a rescan CT (rCT) during treatment were included in this study. Contour volume changes between the planning CT (pCT) and rCT were determined. The original treatment plan was calculated on the pCT, CBCT prior to the rCT, pCT deformed to the anatomy of the CBCT (dCT), and rCT (considered the gold standard). The dose to 0.1 cc (D0.1cc) spinal cord was evaluated from the Dose Volume Histograms (DVHs). Results The median dose increase to D0.1cc between the pCT and rCT was 0.7 Gy (inter-quartile range 0.2–1.9 Gy, p < 0.05). No correlation was found between contour volume changes and the spinal cord dose increase. Three patients exhibited an increase of 7.0–7.2 Gy to D0.1cc, resulting in a re-plan; these patients were correctly identified using calculations on the CBCT/dCT. Conclusions An adaptive re-plan can be triggered using spinal cord doses calculated on the CBCT/dCT. Implementing this trigger can reduce patient appointments and radiation dose by eliminating up to 90% of additional un-necessary CT scans, reducing the workload for radiographers, physicists, dosimetrists, and clinicians.

Left-sided breast radiotherapy after conservative surgery: comparison of techniques between volumetric modulated arc therapy, forward-planning intensity-modulated radiotherapy and conventional technique

2016 ◽  
Vol 16 (1) ◽  
pp. 101-108 ◽  
Author(s):  
Upendra Kumar Giri ◽  
Biplab Sarkar ◽  
Kanan Jassal ◽  
Anusheel Munshi ◽  
Tharmar Ganesh ◽  
...  
Keyword(s):  
Volumetric Modulated Arc Therapy ◽  
Intensity Modulated Radiotherapy ◽  
Conservative Surgery ◽  
Target Volume ◽  
Conventional Technique ◽  
Breast Radiotherapy ◽  
Intensity Modulated ◽  
Arc Therapy ◽  
Prescription Dose ◽  
Comparison Of Techniques

AbstractObjectiveThis study was conducted for comparison of techniques between volumetric modulated arc therapy (VMAT), forward-planning intensity-modulated radiotherapy (FIMRT) and conventional technique for left-sided breast radiotherapy after conservative surgery.MethodsIn all, 20 postoperative left breast carcinoma patients were included in this study. In all plans the planning target volume (PTV) was the breast tissue with appropriate margin as per our institutional protocol. The contouring was done on a Monaco Sim (V5.00.02) contouring workstation. All patient were planned using partial arc VMAT in Monaco treatment planning system (TPS) (V5.00.02) and treated on Elekta Synergy linear accelerator. The 3D conformal radiotherapy (3DCRT) and FIMRT planning were done in CMS XIO (V5.00.01.1) TPS. The 3DCRT planning consisted of conventional medial and tangential wedge portals with multileaf collimator field shaping conforming to the target volume. For all the plans generated the following metrics were scored: V105%, V100%, V95%, mean dose (for PTV), V5%, V20%, D2cc and mean dose (for organs at risk).ResultsThe mean PTV volume for 20 patients was 1,074·6±405·1 cc. The highest PTV dose coverage was observed in the 3DCRT technique with 94·1±1·8% of the breast PTV receiving 95% of the prescription dose (V95%). However, it was also observed that this technique resulted in 21·3±10% of the PTV receiving more than 105% of the prescription dose (V105%), which was highest among the three techniques. In contrast, VMAT yielded lowest V95% of 93·0±1·8 and 3·3±5·5% of V105%.ConclusionThis study concluded equivalent result between FIMRT and VMAT. However, VMAT was found to be the choice of radiotherapy technique as it produces lesser dose distribution to heart compared with any other technique.

Dosimetric characteristics of VMAT plans with respect to a different increment of gantry angle size for Ca cervix

2020 ◽  
pp. 1-5
Author(s):  
Munirathinam Natraj ◽  
P. N. Pawaskar ◽  
Arun Chairmadurai
Keyword(s):  
Cervical Cancer ◽  
Volumetric Modulated Arc Therapy ◽  
Target Volume ◽  
Cervical Cancer Patient ◽  
Conformity Index ◽  
Arc Therapy ◽  
Prescription Dose ◽  
The Difference ◽  
Radiotherapy Treatment ◽  
Gantry Angle

Abstract Aim: We have investigated the influence in volumetric-modulated arc therapy (VMAT) plans by a sequence of increment of gantry angle (IGA) in definitive radiotherapy treatment for cervical cancer. The plans are quantitatively analysed in terms of conformity index (CI), heterogeneity index (HI), dose–gradient index (DGI), target coverage (TC) by prescription dose, monitor unit (MU) usage, control points (CPs) and dose to organs. Materials and Methods: In this retrospective study, we selected 27 patients with cervical cancer having aged between 54 and 69. All the patients enrolled in this study were at T3N1M0 stage of cervical cancer. The prescription dose to planning target volume (PTV) was 50 Gy and was administered in 2 Gy/fraction through VMAT technique. VMAT plans were optimised by varying the parameter ‘IGA’ as 10, 20, 30 and 40°. Results: Homogenous dose distribution within PTV and TC by prescription dose was significantly enhanced (p < 0·05) with larger IGA. The difference between volume receiving 15 Gy (V15Gy) in bowel was up to 10% with larger IGA (30 and 40°) and V25Gy in femoral head was up to 3% with smaller IGA (10 and 20°). CPs were enhanced and MU usage was reduced with larger IGA (30 and 40°). IGA 40° had reduced the MU usage than IGA 30° but the CI and DGI were compromised due to large MLC field segments. Conclusion: This study recommends that the larger IGA could yield better results when the number of sectors is even, for a cervical cancer patient. However, more data from more patients need to be obtained and analysed to make this an evidence-based hypothesis.

scholarly journals Dose–volume histogram analysis and clinical evaluation of knowledge-based plans with manual objective constraints for pharyngeal cancer

2020 ◽  
Vol 61 (3) ◽  
pp. 499-505 ◽  
Author(s):  
Takuya Uehara ◽  
Hajime Monzen ◽  
Mikoto Tamura ◽  
Kazuki Ishikawa ◽  
Hiroshi Doi ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Volumetric Modulated Arc Therapy ◽  
Intensity Modulated Radiation Therapy ◽  
Target Volume ◽  
Dose Volume Histogram ◽  
Parotid Glands ◽  
Pharyngeal Cancer ◽  
Knowledge Based ◽  
Dose Volume ◽  
Arc Therapy

Abstract The present study aimed to evaluate whether knowledge-based plans (KBP) from a single optimization could be used clinically, and to compare dose–volume histogram (DVH) parameters and plan quality between KBP with (KBPCONST) and without (KBPORIG) manual objective constraints and clinical manual optimized (CMO) plans for pharyngeal cancer. KBPs were produced from a system trained on clinical plans from 55 patients with pharyngeal cancer who had undergone intensity-modulated radiation therapy or volumetric-modulated arc therapy (VMAT). For another 15 patients, DVH parameters of KBPCONST and KBPORIG from a single optimization were compared with CMO plans with respect to the planning target volume (D98%, D50%, D2%), brainstem maximum dose (Dmax), spinal cord Dmax, parotid gland median and mean dose (Dmed and Dmean), monitor units and modulation complexity score for VMAT. The Dmax of spinal cord and brainstem and the Dmed and Dmean of ipsilateral parotid glands were unacceptably high for KBPORIG, although the KBPCONST DVH parameters met our goal for most patients. KBPCONST and CMO plans produced comparable DVH parameters. The monitor units of KBPCONST were significantly lower than those of the CMO plans (P &lt; 0.001). Dose distribution of the KBPCONST was better than or comparable to that of the CMO plans for 13 (87%) of the 15 patients. In conclusion, KBPORIG was found to be clinically unacceptable, while KBPCONST from a single optimization was comparable or superior to CMO plans for most patients with head and neck cancer.

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