“…The AXB algorithm calculated doses more accurately than AAA for the air cavity region, which agrees with previous studies [19]. The accuracy of the Cyberknife-calculated dose distributions via the Monte-Carlo algorithm has been verified in a separate study [7]. Fig.…”
Section: Resultssupporting
confidence: 87%
“…For metrics where statistically significant differences were identified, VMAT-AXB and VMAT-AAA plans were either slightly better on selected metrics (i.e., maximum PTV dose, mean thyroid gland dose, maximum contralateral arytenoid dose, and MU), or slightly worse (i.e., R50) than the Cyberknife plans. In contrast, a previous study found worse OAR sparing by LINAC-based coplanar IMRT plans than Cyberknife plans [7], likely due to the beam arrangement. In our study, the good LINAC plan quality indicates that using VMAT can evenly distribute the beams to achieve better target coverage, and using non-coplanar geometry can further spare OARs.…”
Section: Discussionmentioning
confidence: 65%
“…Thus, SBRT presents a possible solution to the challenges of improving laryngeal cancer treatment with radiation therapy. Our institution recently performed a phase I study of larynx SBRT using the Cyberknife system (Accuray, Sunnyvale, CA) [7, 8]. The study evaluated the feasibility of using SBRT to treat only the involved site of disease plus a 3 mm margin by large-dose, highly-focal radiation fields.…”
IntroductionStereotactic body radiation therapy (SBRT) was found effective in treating laryngeal cancer with only five treatment fractions by a recent clinical trial (NCT01984502, ClinicalTrials.gov). Nevertheless, this trial used the Cyberknife system, which is not widely accessible enough to benefit all patients affected by laryngeal cancer. Our study investigates the feasibility of larynx SBRT treatment planning on a conventional gantry-based LINAC and compares its plan quality with that from the Cyberknife.Materials & methodsTen larynx SBRT cases were originally treated by Cyberknife using fixed cones in our institution, with plans created and optimized using the Monte-Carlo algorithm in the MultiPlan treatment planning system. These cases were retrospectively planned in the Eclipse planning system for a LINAC with the same prescription dose. We used volumetric modulated arc therapy (VMAT) for larynx SBRT planning in Eclipse and incorporated non-coplanar arcs to approach the Cyberknife’s large solid angle delivery space. We used both anisotropic analytical algorithm (AAA) and Acuros XB (AXB) algorithm for dose calculation and compared their accuracy by measurements on an in-house larynx phantom. We compared the LINAC VMAT plans (VMAT-AAA and VMAT-AXB) with the original Cyberknife plans using dosimetric endpoints such as the conformity index, gradient indices (R50, R20), OAR maximum/mean doses, and the monitor units.ResultsPhantom measurement showed that both the AAA and the AXB algorithms provided adequate dose calculation accuracy (94.7% gamma pass rate on 2%/2 mm criteria for AAA vs. 97.3% for AXB), though AXB provided better accuracy in the air cavity. The LINAC-based VMAT plans achieved similar dosimetric endpoints as the Cyberknife planning, and all plans met the larynx SBRT dosimetric constraints. Cyberknife plans achieved an average conformity index of 1.13, compared to 1.20 of VMAT-AXB and 1.19 of VMAT-AAA. The VMAT plans spared the thyroid gland better with average Dmean of 2.4 Gy (VMAT-AXB) and 2.7 Gy (VMAT-AAA), as compared to 4.3 Gy for Cyberknife plans. The VMAT-AAA plans had a slightly lower contralateral arytenoid Dmax (average: 15.2 Gy) than Cyberknife plans (average: 17.9 Gy) with statistical significance, while the contralateral arytenoid Dmax was similar between VMAT-AXB and Cyberknife plans with no statistically significant difference. Cyberknife plans offered slightly better R50 (average: 5.0) than VMAT-AXB (5.9) and VMAT-AAA (5.7) plans. The VMAT plans substantially reduced the plan MUs to less than 1/3 of the Cyberknife plans, and the differences were statistically significant. The other metrics were similar between VMAT and Cyberknife plans with no statistically significant differences.ConclusionsGantry-based LINACs can achieve similar plan quality to Cyberknife systems. Treatment outcome with both methods remains to be investigated.
“…The AXB algorithm calculated doses more accurately than AAA for the air cavity region, which agrees with previous studies [19]. The accuracy of the Cyberknife-calculated dose distributions via the Monte-Carlo algorithm has been verified in a separate study [7]. Fig.…”
Section: Resultssupporting
confidence: 87%
“…For metrics where statistically significant differences were identified, VMAT-AXB and VMAT-AAA plans were either slightly better on selected metrics (i.e., maximum PTV dose, mean thyroid gland dose, maximum contralateral arytenoid dose, and MU), or slightly worse (i.e., R50) than the Cyberknife plans. In contrast, a previous study found worse OAR sparing by LINAC-based coplanar IMRT plans than Cyberknife plans [7], likely due to the beam arrangement. In our study, the good LINAC plan quality indicates that using VMAT can evenly distribute the beams to achieve better target coverage, and using non-coplanar geometry can further spare OARs.…”
Section: Discussionmentioning
confidence: 65%
“…Thus, SBRT presents a possible solution to the challenges of improving laryngeal cancer treatment with radiation therapy. Our institution recently performed a phase I study of larynx SBRT using the Cyberknife system (Accuray, Sunnyvale, CA) [7, 8]. The study evaluated the feasibility of using SBRT to treat only the involved site of disease plus a 3 mm margin by large-dose, highly-focal radiation fields.…”
IntroductionStereotactic body radiation therapy (SBRT) was found effective in treating laryngeal cancer with only five treatment fractions by a recent clinical trial (NCT01984502, ClinicalTrials.gov). Nevertheless, this trial used the Cyberknife system, which is not widely accessible enough to benefit all patients affected by laryngeal cancer. Our study investigates the feasibility of larynx SBRT treatment planning on a conventional gantry-based LINAC and compares its plan quality with that from the Cyberknife.Materials & methodsTen larynx SBRT cases were originally treated by Cyberknife using fixed cones in our institution, with plans created and optimized using the Monte-Carlo algorithm in the MultiPlan treatment planning system. These cases were retrospectively planned in the Eclipse planning system for a LINAC with the same prescription dose. We used volumetric modulated arc therapy (VMAT) for larynx SBRT planning in Eclipse and incorporated non-coplanar arcs to approach the Cyberknife’s large solid angle delivery space. We used both anisotropic analytical algorithm (AAA) and Acuros XB (AXB) algorithm for dose calculation and compared their accuracy by measurements on an in-house larynx phantom. We compared the LINAC VMAT plans (VMAT-AAA and VMAT-AXB) with the original Cyberknife plans using dosimetric endpoints such as the conformity index, gradient indices (R50, R20), OAR maximum/mean doses, and the monitor units.ResultsPhantom measurement showed that both the AAA and the AXB algorithms provided adequate dose calculation accuracy (94.7% gamma pass rate on 2%/2 mm criteria for AAA vs. 97.3% for AXB), though AXB provided better accuracy in the air cavity. The LINAC-based VMAT plans achieved similar dosimetric endpoints as the Cyberknife planning, and all plans met the larynx SBRT dosimetric constraints. Cyberknife plans achieved an average conformity index of 1.13, compared to 1.20 of VMAT-AXB and 1.19 of VMAT-AAA. The VMAT plans spared the thyroid gland better with average Dmean of 2.4 Gy (VMAT-AXB) and 2.7 Gy (VMAT-AAA), as compared to 4.3 Gy for Cyberknife plans. The VMAT-AAA plans had a slightly lower contralateral arytenoid Dmax (average: 15.2 Gy) than Cyberknife plans (average: 17.9 Gy) with statistical significance, while the contralateral arytenoid Dmax was similar between VMAT-AXB and Cyberknife plans with no statistically significant difference. Cyberknife plans offered slightly better R50 (average: 5.0) than VMAT-AXB (5.9) and VMAT-AAA (5.7) plans. The VMAT plans substantially reduced the plan MUs to less than 1/3 of the Cyberknife plans, and the differences were statistically significant. The other metrics were similar between VMAT and Cyberknife plans with no statistically significant differences.ConclusionsGantry-based LINACs can achieve similar plan quality to Cyberknife systems. Treatment outcome with both methods remains to be investigated.
“…Results of both studies were comparable. Ding et al compared hemilarynx IMRT plans with SBRT; considerable reduction in contralateral arytenoid, ipsilateral and contralateral carotid, spinal cord, and thyroid gland doses was noted with SBRT plans with Cyberknife platform (37). In their clinical trial, only patients with high volume disease developed serious complications (16).…”
Purpose and Objective: To evaluate the disease-free survival, overall survival, dosimetric, and voice handicap index (VHI) results of T1a glottic invasive squamous cell carcinoma (SCC) patients who underwent hypofractionated single vocal cord irradiation (HSVCI). Materials and Methods: The data of 18 patients with stage T1a glottic SCC were collected prospectively and analyzed retrospectively between July 2016 and July 2019. Patients were immobilized using a custom-fitted thermoplastic face and shoulder mask in hyperextension position. The CT scan was performed with 1-mm-thick slices. A planned target volume (PTV) margin of 3 mm was given to clinical target volume (CTV) in all directions, and 13 organs at risk were identified. Patients were prescribed a total of 5760-5808 cGy in 15-16 fractions. Patients had daily cone-beam computed tomography (CBCT), and the treatment was carried out with the physician. VHI test was applied to patients before and at the end of radiotherapy (RT) and 1, 2, 3, 4, and 6 months after the completion of RT. Results: Local control and overall survival rate is 100% for a median of 18 months (6-44 months) of follow-up. A patient was diagnosed with 2nd primary lung cancer and active treatment still continues. All patients completed the treatment within the scheduled time. Grade 1-2 dysphagia and dermatitis occurred in all patients, and no grade 3 and above side effects were observed. The mean values of VHI were 37.
“…Thus, a suitable phantom for these validation measurements on the MR‐Linac needs to be visible on both MRI and CT and will ideally also faithfully represent the treatment geometry. Thus far, anthropomorphic larynx phantoms developed for dose verification have typically been composed of wax and are only CT‐visible 15,6 . However, the use of 3D printing technology has now enabled the rapid generation of patient‐specific phantoms 16,17 using medical images to delineate anatomical structures to be printed, 18 with the flexibility for custom designing the remaining phantom for additional features such as MR‐visibility.…”
Purpose
Internal motion of the larynx can cause normal tissue toxicity and/or tumor underdosage during radiotherapy. MR‐guided radiation therapy (MRgRT) provides improved soft‐tissue contrast for patient setup and real‐time gating of radiation based on cine imaging of tumor motion, potentially making it an advantageous modality for laryngeal treatments. However, there are potential concerns regarding the small target size, proximity to heterogeneous tissue interfaces in the airway that may cause dosimetric errors in the presence of the magnetic field, and uncertainty about the ability of MR‐linear accelerator (MR‐Linac) systems to visualize and track laryngeal motion. To date, there have been no reports of the use of MRgRT for laryngeal treatments.
Methods
A healthy volunteer was imaged on a ViewRay MRIdian MR‐Linac. Organs‐at‐risk and a laryngeal pseudo target were contoured and used to generate a stereotactic body radiotherapy plan. A custom phantom was created using 3D‐printing based on structures delineated on the volunteer images to construct an enclosure containing the target and airway anatomy, with a gap for radiochromic film, and filled with gelatin . The treatment plan was mapped onto the phantom and delivered dose assessed on radiochromic film with global normalization and a 10% dose threshold. A cine MR of the volunteer was acquired to assess the magnitude of larynx motion with speaking and swallowing, and system's ability to gate radiation.
Results
A clinically acceptable laryngeal treatment plan and larynx phantom that was MR and computed tomography‐visible were successfully created. The delivered dose had good agreement with the treatment plan with a gamma passing rate of 96.5% (3%/2 mm). The MR‐Linac was able to visualize, track, and gate larynx motion.
Conclusions
The MRgRT workflow for laryngeal treatments was assessed and performed in preparation for clinical implementation on the MR‐Linac, demonstrating that it is feasible to treat laryngeal cancer patients on the MR‐Linac.
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