1887
banner image
No data available.
Please log in to see this content.
You have no subscription access to this content.
No metrics data to plot.
The attempt to load metrics for this article has failed.
The attempt to plot a graph for these metrics has failed.
Technique factors and their relationship to radiation dose in pendant geometry breast CT
Rent:
Rent this article for
USD
10.1118/1.2128126
/content/aapm/journal/medphys/32/12/10.1118/1.2128126
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/32/12/10.1118/1.2128126

Figures

Image of FIG. 1.
FIG. 1.

The first prototype breast CT scanner at our institution, code-named Albion, is pictured. The water-cooled tungsten anode x-ray tube is seen in the foreground, and the flat panel detector system is positioned at the other end of the gantry arm. The system is shown with the patient tabletop removed.

Image of FIG. 2.
FIG. 2.

The HVL is shown as a function of kVp for measured values (circles) and for values computed using a spectral model (line).

Image of FIG. 3.
FIG. 3.

The air kerma output of the Albion breast CT scanner, normalized per unit mAs, is illustrated. The air kerma (in per mAs) was measured at the isocenter of the scanner, at 468 mm from the x-ray source. The measured data were computer fit that resulted in .

Image of FIG. 4.
FIG. 4.

The mean glandular dose, averaged over four mammography systems, is shown as a function of compressed breast thickness and glandular fraction. The dose from two views is plotted. The symbols correspond to different breast compositions: 0% glandular (triangles), 50% glandular (circles), and 100% glandular (squares). The lines show the 3D fit to the data (MGD versus thickness and glandular percent), with .

Image of FIG. 5.
FIG. 5.

Measured dimensional data (circles) from 200 women are shown, with the effective diameter plotted as a function of the compressed breast thickness. Linear regression was used to characterize the relationship, with . A 5 cm compressed breast thickness corresponds to a 14 cm breast diameter.

Image of FIG. 6.
FIG. 6.

The Monte Carlo-determined DgN values for polyenergetic x-ray spectra are shown as a function of kVp (symbols), and the computer fit values are shown as the lines. The upper three datasets correspond to a 10 cm diameter breast, and the lower three sets to an 18 cm breast diameter. The solid symbols correspond to 50% glandular, open circles to 0% glandular, and open squares to 100% glandular.

Image of FIG. 7.
FIG. 7.

The air kerma at the isocenter that delivers the same dose as two-view mammography is illustrated as a function of kVp, for five different breast diameters. These data are for 50% glandular breast composition. The data shown in this plot are provided for 0%, 50%, and 100% glandular breasts in Tables II–IV, respectively.

Image of FIG. 8.
FIG. 8.

The photon fluence required at the isocenter of the breast CT scanner is illustrated. The photon fluence increases dramatically for larger breast diameters, but it is nearly independent of kVp.

Image of FIG. 9.
FIG. 9.

The mAs is shown as a function of kVp, for breast diameters ranging from 10 to 18 cm. The ordinate axis is logarithmic, underscoring the enormous increase in the required mAs at low kVps. This increase is due in part to the reduced efficiency of x-ray output at lower kVps.

Tables

Generic image for table
TABLE I.

Spectral parameters. The breast CT x-ray spectra were modeled in this investigation (and utilized in the Albion scanner) and a number of parameters were determined from each modeled spectrum (or physically measured, in the case of x-ray source output). These parameters, which are specific to the x-ray system on the Albion scanner in our laboratory, are as follows: A=air kerma of x-ray source at the isocenter (mGy/100 mAs), B=exposure of x-ray source at the isocenter (mR/mAs), C=HVL in mm Al, D=average energy (keV) of entrance x-ray beam, E=average energy (keV) of exit x-ray beam, through a 14 cm 50% glandular breast, F=beam hardening factor, G=percent transmission of beam through a 14 cm 50% breast, H=photon fluence per mGy air kerma

Generic image for table
TABLE II.

Air Kerma for 0% glandular/100% adipose breast composition. Air Kerma (mGy) values, calculated at the isocenter of the breast CT scanner, which deliver mean glandular doses equal to two-view mammography, for different kVp and breast diameters.

Generic image for table
TABLE III.

Air kerma for 50% glandular/50% adipose breast composition. Air Kerma (mGy) values, calculated at the isocenter of the breast CT scanner, which deliver mean glandular doses equal to two-view mammography, for different kVp and breast diameters.

Generic image for table
TABLE IV.

Air kerma for 100% glandular/0% adipose breast composition. Air Kerma (mGy) values, calculated at the isocenter of the breast CT scanner, which deliver mean glandular doses equal to two-view mammography, for different kVp and breast diameters.

Generic image for table
TABLE V.

mAs for 0% glandular/100% adipose breast composition. The mAs values for the entire breast CT scan that delivers the same dose as two-view mammography are given in the table. To determine mA, divide the mAs values given below by the total time of the active scan (in seconds).

Generic image for table
TABLE VI.

mAs for 50% glandular/50% adipose breast composition. The mAs values for the entire breast CT scan that delivers the same dose as two-view mammography are given in the table. To determine mA, divide the mAs values given below by the total time of the active scan (in seconds).

Generic image for table
TABLE VII.

mAs for 100% glandular/0% adipose breast composition.The mAs values for the entire breast CT scan that delivers the same dose as two-view mammography are given in the table. To determine mA, divide the mAs values given below by the total time of the active scan (in seconds).

Loading

Article metrics loading...

/content/aapm/journal/medphys/32/12/10.1118/1.2128126
2005-11-22
2014-04-16
Loading

Full text loading...

This is a required field
Please enter a valid email address
752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Technique factors and their relationship to radiation dose in pendant geometry breast CT
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/32/12/10.1118/1.2128126
10.1118/1.2128126
SEARCH_EXPAND_ITEM