VMAT planning for Elekta linear accelerators is supported with the following commercial and clinical routine treatment planning systems. Med Phys. Mar;37(3) Comparison of Elekta VMAT with helical tomotherapy and fixed field IMRT: plan quality, delivery efficiency and accuracy. VMAT, formally known as Intensity Modulated Arc Therapy. (IMAT), was first brought up by Dr. . Elekta VMAT can be delivered using single or multiple arcs.
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Gallen, Rorschacherstrasse 95, St. The purpose of this study was to evaluate this new algorithm and to compare it to intensity-modulated radiation therapy IMRT for various disease sites by creating single- and double-arc VMAT plans.
A total vmzt plans were evaluated in this study, including 38 endometrial, 57 head and neck, 12 brain, 10 breast and 45 prostate cancer cases. Eldkta plans were generated using vmxt preclinical version of Eclipse with tumor-region-specific optimizing templates without interference of the operator: All plans were evaluated based on target coverage, homogeneity and conformity.
The organs at risk OARs were analyzed according to plan objectives, such as the mean and maximum doses. If one or more objectives were exceeded, the plan was considered clinically unacceptable, and a second VMAT plan was created by adapting the optimization penalties once. The mean total body dose was statistically significant lower for the considered arc techniques IMRT: However, the sparing of OARs shows individual behavior that depends strongly on the different tumor regions.
A clear difference is found in the number of monitor units MUs per plan: These findings eletka that elektw on optimizing templates with minimal interaction of the operator, the Eclipse TPS is able to achieve a plan quality for the Elekta VMAT delivery technique that is comparable to that of fixed-field IMRT. Plans with two arcs show better dose distributions than plans with one arc. Different treatment planning systems TPS are available for accelerators from both manufacturers, and the VMAT technique produces plan quality and dose distributions that are comparable and often superior to those of fixed-field step-and-shoot or sliding window IMRT for a wide range of disease sites [ 10 – 20 ].
Moreover, the essential advantage of the VMAT technique is the improved efficiency of the treatment in terms of significant reduction of the number of monitor units MUs and the shorter delivery time [ 102122 ]. VMAT planning for Elekta linear accelerators is supported with the following commercial and clinical routine treatment planning systems: The newest release of the Eclipse TPS v.
The purpose of this study wlekta to evaluate this algorithm for different disease sites by creating single- and double-arc VMAT plans. To exclude this qualitative and difficult-to-measure effect, a template based method that allows plans to be generated with almost no user interaction will be introduced.
Therefore, the quality of the optimizer can be analyzed. The dynamic arc plans are compared to clinical step-and-shoot IMRT plans on a statistical basis. From five different tumor regions — head and neck, brain, cervical and endometrial, breast and prostate — fixed-field step-and-shoot IMRT plans that were used for patient treatment between January and June on an Elekta Synergy Linac were examined.
These patient plans included the following:. The study was performed based on ethical board approval Ethics Committee St. The clinical step-and-shoot IMRT plans were generated using the Eclipse treatment planning system version 8. Depending on the tumor region, 5 to 9 coplanar fields were chosen, consistent with our clinical standard section II.
Depending on the tumor region at least 3 prostate, cervical to 6 breast, head and neck, brain attempts were taken to get a clinically acceptable IMRT plan. The dose calculation was performed using the anisotropic analytic algorithm AAA [ 25 ] and a grid size of 2.
For cases with one hip elektaa, two resp. The length of the arcs was adjusted separately for each case one implant: In all cases, the isocenter was placed in the center of the PTV. The dose calculation was performed with the AAA algorithm and a grid size of 2. Based on the available IMRT optimizing templates, new VMAT optimizing templates for each treatment region and prescribed dose were created in total 10 different templates: All these templates were tested on a few patients to evaluate whether they produced reasonable results concerning the plan quality in comparison to IMRT and concerning the irradiation by measuring the eleekta time and dose distribution [ 26 ].
During the optimizing process, the objectives or weights were not adjusted to exclude the influence of the operator, which allows an objective and independent evaluation of the dose distribution of all tumor regions. The adapted plans were then evaluated again and no further adapted plans were created, even if any objectives were not met. To visualize the differences, average cumulative DVHs were calculated per examined tumor region for each organ and treatment technique. CN ranges from 0 to 1, where 1 is the ideal value.
Between the evaluated tumor regions and prescribed doses, differences were identified. Before 1A, 2A and after modification 1Am, 2Am of the optimization penalties divided by tumor site: The number of monitor units was statistically significant lower for VMAT by factors of 1. Single and double arc plans before 1A, 2A and after modification 1Am, 2Am of the optimization penalties; values are expressed as the mean range.
In a vjat of single- and double-arc techniques, the PTV coverage was significantly different for plans with two arcs. Of the 38 cervical and endometrial cases for the double-arc technique, 19 were in tolerance for both OAR sparing and PTV coverage; after adapting the optimization penalties, 23 plans met all objectives.
For the single-arc technique vvmatsix plans were acceptable after adapting 1Am nine. For most non-acceptable plans, the following values were out of tolerance: D max of the PTV 1A: The doses in the OARs were similar to IMRT for both single- and double-arc plans; small but significant differences were detected for total body dose D mean: Double-arc plans vamt a significant reduction of high-dose regions in the small intestine V 45 Gy: The maximum target dose and the conformity were better for double-arc plans than for IMRT; for single-arc plans, the corresponding values were below the mean values of IMRT.
Comparing single- and double-arc plans, all parameters except MUs exhibited differences in favor of the double-arc technique, and differences in the parameters for PTV coverage, maximum dose in the bladder and rectum were statistically significant.
Mean DVHs of 38 cervical and endometrial cases. IMRT; thin dashed line: For the single-arc technique, elekga plans met the clinical objectives, 8 plans after modifications.
Cases with target doses of Significant differences in IMRT for single- and double-arc plans were noted for total body dose D max: However, the maximum vvmat dose was clearly lower for all VMAT techniques up to The mean dose and V 28 Gy for the parotid glands were slightly better for VMAT after modification of the optimizing process; before modification, they were significantly better for IMRT.
The median dose of the sub-dose levels was significantly higher than in IMRT Comparing the single-arc and double-arc techniques revealed significant differences in favor of double-arc plans concerning target coverage of PTV1 D max: Mean DVHs of 39 head and neck cancer cases with prescriptions of The maximum dose in the lips was statistically significant lower for VMAT up to The dose coverage in the target volumes was better for all VMAT techniques.
Comparing the single- and double leekta techniques reveals significant differences in favor of double-arc plans concerning target coverage of PTV1 D max: Detailed values and the averaged DVH comparison are shown in the Additional file 2.
An acceptable plan was achieved for the double-arc technique in 9 out of 10 breast cancer cases; an acceptable plan was achieved in 5 cases for the single-arc technique. In all non-acceptable cases before and after adapting the optimizing processeither the maximum target dose was too high 1A: The OARs met the clinical objectives in all cases for all techniques. For both single- and double-arc plans, the OARs vjat total body dose showed slight but non-significant improvements compared to IMRT; however, the maximum spine dose 1A: The mean dose for the heart seems to show a statistically significant improvement for single arc plans IMRT: But the differences depend on the side of the irradiated breast: Due to the low number of cases 6 left, 4 rightno statistical significance for the differences can be given.
eldkta A comparison of single- and double-arc techniques revealed significant differences in favor of double-arc plans concerning target coverage D max: Detailed values and the averaged DVH comparison are shown in the Additional file 3.
A total of 45 prostate cases were analyzed, of which 11 involved pelvic lymph nodes, 16 involved one hip implant and 18 involved two hip implants.
Elekta VMAT Radiation Therapy Rapidly Gaining Users Worldwide As Technique Evolves
All 2A plans for the LN cases met the clinical objectives; 1A plans were acceptable in 8 cases, 10 after modification. Double-arc plans with one implant were acceptable in 11 of the 18 total cases and in 14 cases after adapting the optimization penalties. For the single-arc technique, 8 plans met the objectives, 9 after modification.
Cases with two implants had acceptable 2A plans in 6 of 16 cases. After modifying the optimization penalties, the number of acceptable plans increased to 11; 5 single-arc plans were acceptable, 7 after modification. Single-arc plans had smaller improvements in comparison to IMRT, with significant differences only for D max A comparison of single- and double-arc plans revealed highly significant differences in favor of 2A in target coverage and the maximum bladder dose.
The Additional file 4 shows detailed results and the averaged DVH comparison. Prostate cases with one hip implant presented varying results depending on the treatment technique. However, conformity was significantly better for single- and double-arc plans CN: The differences between single- and double-arc plans were small: The total body and rectum doses were better in favor of single-arc plans.
Detailed values and the averaged DVH comparison are shown in the Additional file 5.
Elekta VMAT – Peninsula Cancer Center
However, the sparing of the implants and the total body dose were significantly reduced in comparison to the IMRT plans implant: The vmwt between single- and double-arc plans were small; significant differences in favor of 2A were noted for the maximum dose in the PTV Mean DVHs of 18 prostate cancer cases with two hip implants. Of the 12 brain cancer cases, five 2A plans were acceptable for both OAR sparing and target coverage; after adapting the optimization penalties, 6 plans met all objectives.
For single-arc technique, 4 plans were accepted, 5 after adaptation.
However, the maximum doses of the lenses and the optical nerves were lower for VMAT lenses: For the right optical nerve, increases of 2. Significant differences were only observed for conformity in both modified single- and double-arc plans CN: Mean DVHs of 12 brain cancer cases. The question of whether dose distribution and quality are different in VMAT plans compared to IMRT plans has been evaluated in a large number of studies [ 10 – 20 ].
Even if the results of these studies show some differences that may be caused by different optimizing engines, the number of arcs per plan, the linac type or tumor sites, the conclusions are consistent: The main difference between the two techniques, and therefore an advantage for VMAT, lies in the reduction in delivery time.