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Patient dose and image quality from mega-voltage cone beam computed tomography imaging
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10.1118/1.2428407
/content/aapm/journal/medphys/34/2/10.1118/1.2428407
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/34/2/10.1118/1.2428407

Figures

Image of FIG. 1.
FIG. 1.

The cylindrical acrylic phantoms measurement setup. A small volume chamber was placed at the isocenter as well as below the surface at the 0°, 90°, 180°, and 270° positions.

Image of FIG. 2.
FIG. 2.

The TLD measurement setup in a Rando phantom: (a) pelvic region and (b) head and neck region. Each TLD is located from its closest neighbor. The circles mark the TLD locations. The beam arc rotates from 270° to 110°.

Image of FIG. 3.
FIG. 3.

Schematic of (a) the contrast section of the image quality phantom, containing four sets of inserts of different electron density with respect to water: air and materials with density of 1.09, 1.17, and 1.48, respectively; (b) the spatial resolution section of the image quality phantom, containing 11 groups of bars whose spacings correspond to different resolutions.

Image of FIG. 4.
FIG. 4.

Dose delivered at the isocenter by the 8, 10 and protocols in the pelvic phantom, and by the 5, 8 and protocols in the head and neck phantom. Data were fitted with a linear function that included the origin at 0.

Image of FIG. 5.
FIG. 5.

Isodose lines in the pelvic and the head and neck Rando phantoms for the and protocols, respectively; (a,d) superior to the isocenter plane, (b,e) isocenter plane, (c,f) inferior to the isocenter plane. The position of the isocenter axis is located at the crossing of the dark horizontal and vertical lines.

Image of FIG. 6.
FIG. 6.

The reconstructed image of a slice in the low contrast section of the image quality phantom by a CT scanner (kV-CT, top left) and MV-CBCT system for seven different MU protocols (3, 5, 8, 10, 12, 15, and ) identified by their calculated isocenter dose.

Image of FIG. 7.
FIG. 7.

Contrast to noise ratio (CNR) measured for seven different MU protocols (3, 5, 8, 10, 12, 15, and ) as a function of the dose delivered at the insert location. Each curve is identified by the electron density of the material relative to the background. The CNR varies as the square root of the dose.

Image of FIG. 8.
FIG. 8.

Transverse slice of a head and neck patient imaged with (a) kV-CT, (b) MV-CBCT protocol, (c) MV-CBCT protocol. The lower dose is sufficient to show the bony structures on the MV-CBCT image. Soft tissue boundaries are more visible with the higher dose.

Tables

Generic image for table
TABLE I.

Dose delivered to the acrylic phantoms measured using a small volume ion chamber, along with the XiO treatment planning system (TPS) calculations.

Generic image for table
TABLE II.

TLD dose measurements in the pelvic Rando phantom for the protocol, along with the XiO treatment planning system calculations. The measured dose value is the average of the three TLD measurements in the same horizontal plane.

Generic image for table
TABLE III.

TLD dose measurements in the nasopharynx of the Rando phantom for the protocol, along with the XiO treatment planning system calculations. The measured dose value is the average of the three TLD measurements in the same horizontal plane.

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/content/aapm/journal/medphys/34/2/10.1118/1.2428407
2007-01-17
2014-04-24
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Patient dose and image quality from mega-voltage cone beam computed tomography imaging
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/34/2/10.1118/1.2428407
10.1118/1.2428407
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