1. Toward Magnetic Resonance–Only Simulation: Segmentation of Bone in MR for Radiation Therapy Verification of the Head 
Huan Yu, PhD, Curtis Caldwell, PhD, Judith Balogh, MD, Katherine Mah, MSc 
International Journal of Radiation Oncology • Biology • Physics 
Volume 89, Issue 3, Pages (July 2014)
DOI: /j.ijrobp
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2. Fig. 1
Air volumes (red) contoured at 6 levels. (a) Frontal sinus. (b) Ethmoid sinus and nasal cavities, excluding the nasal bone (yellow). (c) Nasal cavity, ethmoid sinus and sphenoid sinus. (d) Mastoid sinus and ear canal. (e) Maxillary sinus, nasal cavity. The maxilla (green) is excluded using turbinate (purple) as a reference. (f) Pharynx.
International Journal of Radiation Oncology • Biology • Physics  , DOI: ( /j.ijrobp )
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3. Fig. 2
Comparison points of the skull in anterior-posterior (AP) and lateral (LAT) digitally reconstructed radiographs (DRRs): superior (gray) in AP DRR, superior (blue) in LAT DRR, the left most (orange), the right most (red), anterior (green), posterior (yellow), the base (sky blue) and zygomatic bone(purple).
International Journal of Radiation Oncology • Biology • Physics  , DOI: ( /j.ijrobp )
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4. Fig. 3
Setting the anterior point: (a) Initially the point (green sphere) was set on the sharp edge of a lateral digitally reconstructed radiograph. (b) The point (green circle) was located in a sagittal slice, and (c) positioned on the intersection of the bone contour and beam axis (d and e). The point was reviewed in transverse and coronal views and adjusted if necessary.
International Journal of Radiation Oncology • Biology • Physics  , DOI: ( /j.ijrobp )
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5. Fig. 4
Comparing “computed tomography–like” magnetic resonance images (ctMRI) to co-registered CT images. (a) Axial ctMR and (b) corresponding CT of a patient. (c) Axial ctMR and (d) corresponding CT of a different patient. Bone contours (red) in all images were obtained using a threshold of 300 HU.
International Journal of Radiation Oncology • Biology • Physics  , DOI: ( /j.ijrobp )
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6. Fig. 5
Comparison of magnetic resonance–based digitally reconstructed radiographs (DRRs) (a, anterior-posterior; c, lateral) and computed tomography–based DRRs (b, anterior posterior; d, lateral).
International Journal of Radiation Oncology • Biology • Physics  , DOI: ( /j.ijrobp )
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