TY - JOUR
T1 - Dosimetric feasibility of the hybrid Magnetic Resonance Imaging (MRI)-linac System (MRL) for brain metastases
T2 - The impact of the magnetic field
AU - Tseng, Chia-Lin
AU - Eppinga, Wietse
AU - Seravalli, Enrica
AU - Hackett, Sara
AU - Brand, Eric
AU - Ruschin, Mark
AU - Lee, Young K
AU - Atenafu, Eshetu G
AU - Sahgal, Arjun
N1 - Funding Information:
Dr. Arjun Sahgal has received honorarium for previous educational seminars from Medtronic Kyphoplasty division, Elekta AB, and Varian Medical Systems. He has received research grants from Elekta AB. He has served in consulting/advisory role with Varian Medical Systems and Hoffmann-La Roche Limited; otherwise there are no conflicts of interest to disclose.
Publisher Copyright:
© 2017 Elsevier B.V.
PY - 2017/11
Y1 - 2017/11
N2 - Background and purpose We aimed to investigate the suitability of treating patients with single brain metastases using stereotactic radiosurgery (SRS) with the MRL and to characterize the dosimetric impact at tissue-air interfaces resulting primarily from the electron return effect (ERE). Material and methods 24 patients treated for intact single brain metastases were analyzed. Three radiotherapy plans with the same prescribed dose were generated for each case: (1) noncoplanar volumetric modulated arc therapy (VMAT), (2) coplanar step-and-shoot intensity modulated radiotherapy (IMRT) on the MRL in the absence (MRLB=0), and (3) in the presence of the transverse magnetic field (MRLB=1.5). The plans were evaluated using cumulative dose–volume histograms and by calculation of Paddick conformity index (CI), V100%, V12Gy minus gross tumor volume (V12Gy – GTV), and V2Gy. At tissue-air boundaries, the dosimetric impact of the magnetic field was quantified using a 5 mm rim of tissue. Results All plans met the target coverage and organs-at-risk planning objectives. Differences between all investigated dosimetric parameters significantly favored the VMAT plans as compared to the MRLB=0 and MRLB=1.5 plans, except for V2Gy. The mean V12Gy – GTV and V2Gy marginally favored the MRLB=0 plans compared to the MRLB=1.5 plans (mean difference: 0.45 cm
3, p = 0.0019 and 16.46 cm
3, p < 0.0001, respectively). The presence of the magnetic field resulted in a statistically significant but small increase in mean dose and D
2cc in the skin (0.08 Gy, p < 0.0001 and 0.6 Gy, p < 0.0001, respectively) and around air cavities (0.07 Gy, p = 0.0092 and 0.3 Gy, p = 0.0004, respectively). Conclusions It is feasible to generate stereotactic radiation plans that satisfy clinical requirements using the MRL in the setting of single brain metastases. The dosimetric impact of the magnetic field including the ERE at tissue-air boundaries is minor and does not negatively impact target conformity or dose gradient.
AB - Background and purpose We aimed to investigate the suitability of treating patients with single brain metastases using stereotactic radiosurgery (SRS) with the MRL and to characterize the dosimetric impact at tissue-air interfaces resulting primarily from the electron return effect (ERE). Material and methods 24 patients treated for intact single brain metastases were analyzed. Three radiotherapy plans with the same prescribed dose were generated for each case: (1) noncoplanar volumetric modulated arc therapy (VMAT), (2) coplanar step-and-shoot intensity modulated radiotherapy (IMRT) on the MRL in the absence (MRLB=0), and (3) in the presence of the transverse magnetic field (MRLB=1.5). The plans were evaluated using cumulative dose–volume histograms and by calculation of Paddick conformity index (CI), V100%, V12Gy minus gross tumor volume (V12Gy – GTV), and V2Gy. At tissue-air boundaries, the dosimetric impact of the magnetic field was quantified using a 5 mm rim of tissue. Results All plans met the target coverage and organs-at-risk planning objectives. Differences between all investigated dosimetric parameters significantly favored the VMAT plans as compared to the MRLB=0 and MRLB=1.5 plans, except for V2Gy. The mean V12Gy – GTV and V2Gy marginally favored the MRLB=0 plans compared to the MRLB=1.5 plans (mean difference: 0.45 cm
3, p = 0.0019 and 16.46 cm
3, p < 0.0001, respectively). The presence of the magnetic field resulted in a statistically significant but small increase in mean dose and D
2cc in the skin (0.08 Gy, p < 0.0001 and 0.6 Gy, p < 0.0001, respectively) and around air cavities (0.07 Gy, p = 0.0092 and 0.3 Gy, p = 0.0004, respectively). Conclusions It is feasible to generate stereotactic radiation plans that satisfy clinical requirements using the MRL in the setting of single brain metastases. The dosimetric impact of the magnetic field including the ERE at tissue-air boundaries is minor and does not negatively impact target conformity or dose gradient.
KW - Brain metastasis
KW - Electron return effect
KW - MR-linac
KW - Stereotactic radiosurgery
UR - http://www.scopus.com/inward/record.url?scp=85032205738&partnerID=8YFLogxK
U2 - 10.1016/j.radonc.2017.09.036
DO - 10.1016/j.radonc.2017.09.036
M3 - Article
C2 - 29079310
SN - 0167-8140
VL - 125
SP - 273
EP - 279
JO - Radiotherapy & Oncology
JF - Radiotherapy & Oncology
IS - 2
ER -