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Variable dose interplay effects across radiosurgical apparatus in treating multiple brain metastases.

Ma L, Nichol A, Hossain S, Wang B, Petti P, Vellani R, Higby C, Ahmad S, Barani I, Shrieve DC, Larson DA, Sahgal A - Int J Comput Assist Radiol Surg (2014)

Bottom Line: All treatment plans were developed at individual centers, and the results were centrally analyzed.We found that dose-volume constraints were satisfied by each apparatus with some differences noted in certain structures such as the lens.Treatment times were shortest with TrueBeam FFF.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiation Oncology, University of California, San Francisco, 505 Parnassus Avenue, Room L-08, San Francisco, CA , 94143, USA, lijunma@radonc.ucsf.edu.

ABSTRACT

Purpose: Normal brain tissue doses have been shown to be strongly apparatus dependent for multi-target stereotactic radiosurgery. In this study, we investigated whether inter-target dose interplay effects across contemporary radiosurgical treatment platforms are responsible for such an observation.

Methods: For the study, subsets ([Formula: see text] and 12) of a total of 12 targets were planned at six institutions. Treatment platforms included the (1) Gamma Knife Perfexion (PFX), (2) CyberKnife, (3) Novalis linear accelerator equipped with a 3.0-mm multi-leaf collimator (MLC), and the (4) Varian Truebeam flattening-filter-free (FFF) linear accelerator also equipped with a 2.5 mm MLC. Identical dose-volume constraints for the targets and critical structures were applied for each apparatus. All treatment plans were developed at individual centers, and the results were centrally analyzed.

Results: We found that dose-volume constraints were satisfied by each apparatus with some differences noted in certain structures such as the lens. The peripheral normal brain tissue doses were lowest for the PFX and highest for TrueBeam FFF and CyberKnife treatment plans. Comparing the volumes of normal brain receiving 12 Gy, TrueBeam FFF, Novalis, and CyberKnife were 180-290 % higher than PFX. The mean volume of normal brain-per target receiving 4-Gy increased by approximately 3.0 cc per target for TrueBeam, 2.7 cc per target for CyberKnife, 2.0 cc per target for Novalis, and 0.82 cc per target for PFX. The beam-on time was shortest with the TrueBeam FFF (e.g., 6-9 min at a machine output rate of 1,200 MU/min) and longest for the PFX (e.g., 50-150 mins at a machine output rate of 350 cGy/min).

Conclusion: The volumes of normal brain receiving 4 and 12 Gy were higher, and increased more swiftly per target, for Linac-based SRS platforms than for PFX. Treatment times were shortest with TrueBeam FFF.

No MeSH data available.


Comparison of Paddick dose conformity index for treatment plans with , and 12 targets respectively. The four SRS modalities are denoted as: GK Gamma Knife Perfexion, CK CyberKnife, NOV Novalis, FFF flattening filter free Truebeam
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Fig3: Comparison of Paddick dose conformity index for treatment plans with , and 12 targets respectively. The four SRS modalities are denoted as: GK Gamma Knife Perfexion, CK CyberKnife, NOV Novalis, FFF flattening filter free Truebeam

Mentions: All studied SRS modalities satisfied the normal tissue dose constraints. The lens dose constraint was 2 Gy, and the mean lens doses were 0.31 (range 0.13–0.49) Gy for PFX, 0.37 (range 0.2–0.54) Gy for Novalis, 1.35 (range 0.86–1.84) Gy for CyberKnife, and 1.83 (range 1.68–1.98) Gy for TrueBeam FFF. The higher lens doses observed for the Cyberknife and TrueBeam plans were likely a result of inverse planning optimization to a 2 Gy lens dose constraint. Figure 3 shows the results of Paddick conformity indices (PCI) [9] for the four SRS modalities. Note that Truebeam FFF PCI values were either the highest or the second highest for all the treatment plans. Among isocentric linac-based SRS delivery, Truebeam FFF with intensity-modulated arc beams produced consistently superior PCI values compared with CyberKnife and Novalis DCA delivery (which exhibited the lowest PCI values among the studied SRS treatment modalities). Among all the modalities, the central target dose hot spots such as 120 % of the prescibed dose was highest for PFX because of the standard practice of selecting a low isodose value such as 50 % of the maximum dose when prescribing a treatment.Fig. 3


Variable dose interplay effects across radiosurgical apparatus in treating multiple brain metastases.

Ma L, Nichol A, Hossain S, Wang B, Petti P, Vellani R, Higby C, Ahmad S, Barani I, Shrieve DC, Larson DA, Sahgal A - Int J Comput Assist Radiol Surg (2014)

Comparison of Paddick dose conformity index for treatment plans with , and 12 targets respectively. The four SRS modalities are denoted as: GK Gamma Knife Perfexion, CK CyberKnife, NOV Novalis, FFF flattening filter free Truebeam
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4215114&req=5

Fig3: Comparison of Paddick dose conformity index for treatment plans with , and 12 targets respectively. The four SRS modalities are denoted as: GK Gamma Knife Perfexion, CK CyberKnife, NOV Novalis, FFF flattening filter free Truebeam
Mentions: All studied SRS modalities satisfied the normal tissue dose constraints. The lens dose constraint was 2 Gy, and the mean lens doses were 0.31 (range 0.13–0.49) Gy for PFX, 0.37 (range 0.2–0.54) Gy for Novalis, 1.35 (range 0.86–1.84) Gy for CyberKnife, and 1.83 (range 1.68–1.98) Gy for TrueBeam FFF. The higher lens doses observed for the Cyberknife and TrueBeam plans were likely a result of inverse planning optimization to a 2 Gy lens dose constraint. Figure 3 shows the results of Paddick conformity indices (PCI) [9] for the four SRS modalities. Note that Truebeam FFF PCI values were either the highest or the second highest for all the treatment plans. Among isocentric linac-based SRS delivery, Truebeam FFF with intensity-modulated arc beams produced consistently superior PCI values compared with CyberKnife and Novalis DCA delivery (which exhibited the lowest PCI values among the studied SRS treatment modalities). Among all the modalities, the central target dose hot spots such as 120 % of the prescibed dose was highest for PFX because of the standard practice of selecting a low isodose value such as 50 % of the maximum dose when prescribing a treatment.Fig. 3

Bottom Line: All treatment plans were developed at individual centers, and the results were centrally analyzed.We found that dose-volume constraints were satisfied by each apparatus with some differences noted in certain structures such as the lens.Treatment times were shortest with TrueBeam FFF.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiation Oncology, University of California, San Francisco, 505 Parnassus Avenue, Room L-08, San Francisco, CA , 94143, USA, lijunma@radonc.ucsf.edu.

ABSTRACT

Purpose: Normal brain tissue doses have been shown to be strongly apparatus dependent for multi-target stereotactic radiosurgery. In this study, we investigated whether inter-target dose interplay effects across contemporary radiosurgical treatment platforms are responsible for such an observation.

Methods: For the study, subsets ([Formula: see text] and 12) of a total of 12 targets were planned at six institutions. Treatment platforms included the (1) Gamma Knife Perfexion (PFX), (2) CyberKnife, (3) Novalis linear accelerator equipped with a 3.0-mm multi-leaf collimator (MLC), and the (4) Varian Truebeam flattening-filter-free (FFF) linear accelerator also equipped with a 2.5 mm MLC. Identical dose-volume constraints for the targets and critical structures were applied for each apparatus. All treatment plans were developed at individual centers, and the results were centrally analyzed.

Results: We found that dose-volume constraints were satisfied by each apparatus with some differences noted in certain structures such as the lens. The peripheral normal brain tissue doses were lowest for the PFX and highest for TrueBeam FFF and CyberKnife treatment plans. Comparing the volumes of normal brain receiving 12 Gy, TrueBeam FFF, Novalis, and CyberKnife were 180-290 % higher than PFX. The mean volume of normal brain-per target receiving 4-Gy increased by approximately 3.0 cc per target for TrueBeam, 2.7 cc per target for CyberKnife, 2.0 cc per target for Novalis, and 0.82 cc per target for PFX. The beam-on time was shortest with the TrueBeam FFF (e.g., 6-9 min at a machine output rate of 1,200 MU/min) and longest for the PFX (e.g., 50-150 mins at a machine output rate of 350 cGy/min).

Conclusion: The volumes of normal brain receiving 4 and 12 Gy were higher, and increased more swiftly per target, for Linac-based SRS platforms than for PFX. Treatment times were shortest with TrueBeam FFF.

No MeSH data available.