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Impact of MLC properties and IMRT technique in meningioma and head-and-neck treatments.

Kantz S, Söhn M, Troeller A, Reiner M, Weingandt H, Alber M, Belka C, Ganswindt U - Radiat Oncol (2015)

Bottom Line: EUD, Dmean, homogeneity and conformity are improved using the Agility-MLC.MU increase with the use of dMLC and VMAT, while the MU are reduced by using the Agility-MLC.Fastest treatments with the best PTV coverage are found for VMAT plans with Agility-MLC, achieving the same sparing of healthy tissue compared to the other combinations of ssIMRT, dMLC and VMAT with either MLCi2(-/+) or Agility.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiation Oncology, Ludwig-Maximilians-University, Munich, Germany. Steffi.Kantz@med.uni-muenchen.de.

ABSTRACT

Purpose: The impact of multileaf collimator (MLC) design and IMRT technique on plan quality and delivery improvements for head-and-neck and meningioma patients is compared in a planning study.

Material and methods: Ten previously treated patients (5 head-and-neck, 5 meningioma) were re-planned for step-and-shoot IMRT (ssIMRT), sliding window IMRT (dMLC) and VMAT using the MLCi2 without (-) and with (+) interdigitation and the Agility-MLC attached to an Elekta 6MV linac. This results in nine plans per patient. Consistent patient individual optimization parameters are used. Plans are generated using the research tool Hyperion V2.4 (equivalent to Elekta Monaco 3.2) with hard constraints for critical structures and objectives for target structures. For VMAT plans, the improved segment shape optimization is used. Critical structures are evaluated based on QUANTEC criteria. PTV coverage is compared by EUD, Dmean, homogeneity and conformity. Additionally, MU/plan, treatment times and number of segments are evaluated.

Results: As constrained optimization is used, all plans fulfill the hard constraints. Doses to critical structures do not differ more than 1 Gy between the nine generated plans for each patient. Only larynx, parotids and eyes differ up to 1.5 Gy (Dmean or Dmax) or 7% (volume-constraint) due to (1) increased scatter, (2) not avoiding structures when using the full range of gantry rotation and (3) improved leaf sequencing with advanced segment shape optimization for VMAT plans. EUD, Dmean, homogeneity and conformity are improved using the Agility-MLC. However, PTV coverage is more affected by technique. MU increase with the use of dMLC and VMAT, while the MU are reduced by using the Agility-MLC. Fastest treatments are always achieved using Agility-MLC, especially in combination with VMAT.

Conclusion: Fastest treatments with the best PTV coverage are found for VMAT plans with Agility-MLC, achieving the same sparing of healthy tissue compared to the other combinations of ssIMRT, dMLC and VMAT with either MLCi2(-/+) or Agility.

No MeSH data available.


Related in: MedlinePlus

Example of one meningioma case (MG2). a DVH for the PTV of all nine generated plans, (b) homogeneity and conformity indices for the PTV, c) evaluated QUANTEC and clinical criteria for OARs
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Fig3: Example of one meningioma case (MG2). a DVH for the PTV of all nine generated plans, (b) homogeneity and conformity indices for the PTV, c) evaluated QUANTEC and clinical criteria for OARs

Mentions: Figure 3 shows the results for one meningioma patient (MG2 in Tables 2) as an example. Firgure 3c depicts that the evaluated OAR parameter differ only for the bulbs (Dmean, Dmax) and the lenses (Dmax). In contrast, Fig. 3a and b depict the differences of the PTV coverage: homogeneity, conformity and Dmean drop clearly, if ssIMRT is used. Influences of the MLC design are only small and highest in combination with VMAT.Fig. 3


Impact of MLC properties and IMRT technique in meningioma and head-and-neck treatments.

Kantz S, Söhn M, Troeller A, Reiner M, Weingandt H, Alber M, Belka C, Ganswindt U - Radiat Oncol (2015)

Example of one meningioma case (MG2). a DVH for the PTV of all nine generated plans, (b) homogeneity and conformity indices for the PTV, c) evaluated QUANTEC and clinical criteria for OARs
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4556413&req=5

Fig3: Example of one meningioma case (MG2). a DVH for the PTV of all nine generated plans, (b) homogeneity and conformity indices for the PTV, c) evaluated QUANTEC and clinical criteria for OARs
Mentions: Figure 3 shows the results for one meningioma patient (MG2 in Tables 2) as an example. Firgure 3c depicts that the evaluated OAR parameter differ only for the bulbs (Dmean, Dmax) and the lenses (Dmax). In contrast, Fig. 3a and b depict the differences of the PTV coverage: homogeneity, conformity and Dmean drop clearly, if ssIMRT is used. Influences of the MLC design are only small and highest in combination with VMAT.Fig. 3

Bottom Line: EUD, Dmean, homogeneity and conformity are improved using the Agility-MLC.MU increase with the use of dMLC and VMAT, while the MU are reduced by using the Agility-MLC.Fastest treatments with the best PTV coverage are found for VMAT plans with Agility-MLC, achieving the same sparing of healthy tissue compared to the other combinations of ssIMRT, dMLC and VMAT with either MLCi2(-/+) or Agility.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiation Oncology, Ludwig-Maximilians-University, Munich, Germany. Steffi.Kantz@med.uni-muenchen.de.

ABSTRACT

Purpose: The impact of multileaf collimator (MLC) design and IMRT technique on plan quality and delivery improvements for head-and-neck and meningioma patients is compared in a planning study.

Material and methods: Ten previously treated patients (5 head-and-neck, 5 meningioma) were re-planned for step-and-shoot IMRT (ssIMRT), sliding window IMRT (dMLC) and VMAT using the MLCi2 without (-) and with (+) interdigitation and the Agility-MLC attached to an Elekta 6MV linac. This results in nine plans per patient. Consistent patient individual optimization parameters are used. Plans are generated using the research tool Hyperion V2.4 (equivalent to Elekta Monaco 3.2) with hard constraints for critical structures and objectives for target structures. For VMAT plans, the improved segment shape optimization is used. Critical structures are evaluated based on QUANTEC criteria. PTV coverage is compared by EUD, Dmean, homogeneity and conformity. Additionally, MU/plan, treatment times and number of segments are evaluated.

Results: As constrained optimization is used, all plans fulfill the hard constraints. Doses to critical structures do not differ more than 1 Gy between the nine generated plans for each patient. Only larynx, parotids and eyes differ up to 1.5 Gy (Dmean or Dmax) or 7% (volume-constraint) due to (1) increased scatter, (2) not avoiding structures when using the full range of gantry rotation and (3) improved leaf sequencing with advanced segment shape optimization for VMAT plans. EUD, Dmean, homogeneity and conformity are improved using the Agility-MLC. However, PTV coverage is more affected by technique. MU increase with the use of dMLC and VMAT, while the MU are reduced by using the Agility-MLC. Fastest treatments are always achieved using Agility-MLC, especially in combination with VMAT.

Conclusion: Fastest treatments with the best PTV coverage are found for VMAT plans with Agility-MLC, achieving the same sparing of healthy tissue compared to the other combinations of ssIMRT, dMLC and VMAT with either MLCi2(-/+) or Agility.

No MeSH data available.


Related in: MedlinePlus