title: In Regard to Habl et al.
authors: Provision Center for Proton Therapy, Knoxville, Tennessee.
authors: Marcio
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authors: Northwestern Medicine Chicago Proton Center, Chicago, Illinois.
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authors: Han-Chih Chang
authors: Department of Radiation Oncology, Washington University School of Medicine, St Louis, Missouri.
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authors: Procure Proton Center, Somerset, New Jersey.
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authors: Mayo Clinic, Rochester, Minnesota.
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authors: Mayo Clinic, Rochester, Minnesota.
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