Limits...
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.


Semi-logarithmic plot of normal brain isodose volumes with  and  of targets for the four SRS modalities ( Gamma Knife Perfexion,  CyberKnife,  Novalis,  flattening filter free Truebeam)
© Copyright Policy - OpenAccess
Related In: Results  -  Collection


getmorefigures.php?uid=PMC4215114&req=5

Fig5: Semi-logarithmic plot of normal brain isodose volumes with and of targets for the four SRS modalities ( Gamma Knife Perfexion, CyberKnife, Novalis, flattening filter free Truebeam)

Mentions: The dependence of varying isodose volumes (i.e., from 20-Gy prescription isodose volume to 4-Gy isodose volume) with increasing number of targets for each SRS modality is plotted in Figs. 5 ( vs. ) and 6 ( vs. ). Note the logarithmic y-axis for all the plots and nonlinear dependence in the isodose volumes with increasing number of targets similar to what was observed in our previous study [5]. Among the four SRS modalities, Gamma Knife PFX yielded the lowest 4-Gy isodose volumes while Truebeam FFF yielded the highest 4-Gy isodose volumes for treatment plans, and CyberKnife yielded the highest 4-Gy isodose volume for treatment plans. The difference in the 4-Gy isodose volumes between the average of these two modalities, and Gamma Knife PFX is in the range of 200–300 %. Although the differences among the four modalities at higher isodose volumes such as the 12-Gy isodose volumes were narrower, Gamma Knife PFX still resulted in the lowest 12-Gy isodose volumes among all the modalities.Fig. 5


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)

Semi-logarithmic plot of normal brain isodose volumes with  and  of targets for the four SRS modalities ( Gamma Knife Perfexion,  CyberKnife,  Novalis,  flattening filter free Truebeam)
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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

Fig5: Semi-logarithmic plot of normal brain isodose volumes with and of targets for the four SRS modalities ( Gamma Knife Perfexion, CyberKnife, Novalis, flattening filter free Truebeam)
Mentions: The dependence of varying isodose volumes (i.e., from 20-Gy prescription isodose volume to 4-Gy isodose volume) with increasing number of targets for each SRS modality is plotted in Figs. 5 ( vs. ) and 6 ( vs. ). Note the logarithmic y-axis for all the plots and nonlinear dependence in the isodose volumes with increasing number of targets similar to what was observed in our previous study [5]. Among the four SRS modalities, Gamma Knife PFX yielded the lowest 4-Gy isodose volumes while Truebeam FFF yielded the highest 4-Gy isodose volumes for treatment plans, and CyberKnife yielded the highest 4-Gy isodose volume for treatment plans. The difference in the 4-Gy isodose volumes between the average of these two modalities, and Gamma Knife PFX is in the range of 200–300 %. Although the differences among the four modalities at higher isodose volumes such as the 12-Gy isodose volumes were narrower, Gamma Knife PFX still resulted in the lowest 12-Gy isodose volumes among all the modalities.Fig. 5

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.