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Dosimetric evaluation of an ipsilateral intensity modulated radiotherapy beam arrangement for parotid malignancies.

Yirmibesoglu E, Fried DV, Kostich M, Rosenman J, Shockley W, Weissler M, Zanation A, Chera B - Radiol Oncol (2013)

Bottom Line: Dose, volume statistics for the planning target volumes (PTVs) and planning risk volumes (PRVs) were compared for the four treatment techniques.Wedge pair plans inadequately covered the deep aspect of the PTV.The mean doses to the brainstem, spinal cord, ipsilateral temporal lobe, cerrebellum and ipsilateral cochlea were similar among the four techniques.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiation Oncology, Kocaeli University Faculty of Medicine, Kocaeli, Turkey ; Department of Radiation Oncology, University of North Carolina Hospitals, Chapel Hill, NC, USA.

ABSTRACT

Background: We conducted a dosimetric comparison of an ipsilateral beam arrangement for intensity modulated radiotherapy (IMRT) with off-axis beams.

Patients and methods: Six patients who received post-operative radiotherapy (RT) for parotid malignancies were used in this dosimetric study. Four treatment plans were created for each CT data set (24 plans): 1) ipsilateral 4-field off-axis IMRT (4fld-OA), 2) conventional wedge pair (WP), 3) 7 field co-planar IMRT (7fld), and 4) ipsilateral co-planar 4-field quartet IMRT (4fld-CP). Dose, volume statistics for the planning target volumes (PTVs) and planning risk volumes (PRVs) were compared for the four treatment techniques.

Results: Wedge pair plans inadequately covered the deep aspect of the PTV. The 7-field IMRT plans delivered the largest low dose volumes to normal tissues. Mean dose to the contralateral parotid was highest for 7 field IMRT. Mean dose to the contralateral submandibular gland was highest for 7 field IMRT and WP. 7 field IMRT plans had the highest dose to the oral cavity. The mean doses to the brainstem, spinal cord, ipsilateral temporal lobe, cerrebellum and ipsilateral cochlea were similar among the four techniques.

Conclusions: For postoperative treatment of the parotid bed, 4-field ipsilateral IMRT techniques provided excellent coverage while maximally sparing the contralateral parotid gland and submandibular gland.

No MeSH data available.


Related in: MedlinePlus

Three-dimensional representation of the orientation of the 4 beams used in the 4-field off-axis IMRT plans for a target on the right side of a patient. A45R-45I = 45 degree right anterior oblique beam with a 45 degree inferior Table kick; A45R-45S = 45 degree right anterior oblique beam with a 45 degree superior Table kick; P45R-45I = 45 degree right posterior oblique beam with a 45 degree inferior Table kick; P45R-45S =45 degree right posterior oblique beam with a 45 degree superior Table kick.
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f1-rado-47-04-411: Three-dimensional representation of the orientation of the 4 beams used in the 4-field off-axis IMRT plans for a target on the right side of a patient. A45R-45I = 45 degree right anterior oblique beam with a 45 degree inferior Table kick; A45R-45S = 45 degree right anterior oblique beam with a 45 degree superior Table kick; P45R-45I = 45 degree right posterior oblique beam with a 45 degree inferior Table kick; P45R-45S =45 degree right posterior oblique beam with a 45 degree superior Table kick.

Mentions: For the 7-field co-planar IMRT seven equally spaced beams (approximately every 52°) were isocentrically centered on the PTV. The field and table angles for the 4-field off axis IMRT plan were: A45R-45I, A45R-45S, P45R-45I, P45R-45S (right side) and A45L-45S, A45L-45I, P45L-45S, P45L-45I (left side) (Figure 1). For example A45R-45I translates into a 45 degree right anterior oblique beam with a 45 degree inferior tablekick. These beam angles were selected to exclude the eye, shoulder, and contralateral parotid and submandibular glands from the beams. Depending on a patient’s anatomy the beam angles may require minor adjustments to exclude the eye and shoulder. Another 4-field coplanar IMRT plan was created for comparison purposes according to the 4-field class solution published by Nutting et al. The 4-field coplanar IMRT plan consisted of paired ipsilateral co-planar anterior andposterior oblique beams with the following angles: 15, 45, 145, and 170° form the anterior plane.3


Dosimetric evaluation of an ipsilateral intensity modulated radiotherapy beam arrangement for parotid malignancies.

Yirmibesoglu E, Fried DV, Kostich M, Rosenman J, Shockley W, Weissler M, Zanation A, Chera B - Radiol Oncol (2013)

Three-dimensional representation of the orientation of the 4 beams used in the 4-field off-axis IMRT plans for a target on the right side of a patient. A45R-45I = 45 degree right anterior oblique beam with a 45 degree inferior Table kick; A45R-45S = 45 degree right anterior oblique beam with a 45 degree superior Table kick; P45R-45I = 45 degree right posterior oblique beam with a 45 degree inferior Table kick; P45R-45S =45 degree right posterior oblique beam with a 45 degree superior Table kick.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC3814288&req=5

f1-rado-47-04-411: Three-dimensional representation of the orientation of the 4 beams used in the 4-field off-axis IMRT plans for a target on the right side of a patient. A45R-45I = 45 degree right anterior oblique beam with a 45 degree inferior Table kick; A45R-45S = 45 degree right anterior oblique beam with a 45 degree superior Table kick; P45R-45I = 45 degree right posterior oblique beam with a 45 degree inferior Table kick; P45R-45S =45 degree right posterior oblique beam with a 45 degree superior Table kick.
Mentions: For the 7-field co-planar IMRT seven equally spaced beams (approximately every 52°) were isocentrically centered on the PTV. The field and table angles for the 4-field off axis IMRT plan were: A45R-45I, A45R-45S, P45R-45I, P45R-45S (right side) and A45L-45S, A45L-45I, P45L-45S, P45L-45I (left side) (Figure 1). For example A45R-45I translates into a 45 degree right anterior oblique beam with a 45 degree inferior tablekick. These beam angles were selected to exclude the eye, shoulder, and contralateral parotid and submandibular glands from the beams. Depending on a patient’s anatomy the beam angles may require minor adjustments to exclude the eye and shoulder. Another 4-field coplanar IMRT plan was created for comparison purposes according to the 4-field class solution published by Nutting et al. The 4-field coplanar IMRT plan consisted of paired ipsilateral co-planar anterior andposterior oblique beams with the following angles: 15, 45, 145, and 170° form the anterior plane.3

Bottom Line: Dose, volume statistics for the planning target volumes (PTVs) and planning risk volumes (PRVs) were compared for the four treatment techniques.Wedge pair plans inadequately covered the deep aspect of the PTV.The mean doses to the brainstem, spinal cord, ipsilateral temporal lobe, cerrebellum and ipsilateral cochlea were similar among the four techniques.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiation Oncology, Kocaeli University Faculty of Medicine, Kocaeli, Turkey ; Department of Radiation Oncology, University of North Carolina Hospitals, Chapel Hill, NC, USA.

ABSTRACT

Background: We conducted a dosimetric comparison of an ipsilateral beam arrangement for intensity modulated radiotherapy (IMRT) with off-axis beams.

Patients and methods: Six patients who received post-operative radiotherapy (RT) for parotid malignancies were used in this dosimetric study. Four treatment plans were created for each CT data set (24 plans): 1) ipsilateral 4-field off-axis IMRT (4fld-OA), 2) conventional wedge pair (WP), 3) 7 field co-planar IMRT (7fld), and 4) ipsilateral co-planar 4-field quartet IMRT (4fld-CP). Dose, volume statistics for the planning target volumes (PTVs) and planning risk volumes (PRVs) were compared for the four treatment techniques.

Results: Wedge pair plans inadequately covered the deep aspect of the PTV. The 7-field IMRT plans delivered the largest low dose volumes to normal tissues. Mean dose to the contralateral parotid was highest for 7 field IMRT. Mean dose to the contralateral submandibular gland was highest for 7 field IMRT and WP. 7 field IMRT plans had the highest dose to the oral cavity. The mean doses to the brainstem, spinal cord, ipsilateral temporal lobe, cerrebellum and ipsilateral cochlea were similar among the four techniques.

Conclusions: For postoperative treatment of the parotid bed, 4-field ipsilateral IMRT techniques provided excellent coverage while maximally sparing the contralateral parotid gland and submandibular gland.

No MeSH data available.


Related in: MedlinePlus