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CT head-scan dosimetry in an anthropomorphic phantom and associated measurement of ACR accreditation-phantom imaging metrics under clinically representative scan conditions
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10.1118/1.4815964
/content/aapm/journal/medphys/40/8/10.1118/1.4815964
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/40/8/10.1118/1.4815964

Figures

Image of FIG. 1.
FIG. 1.

(a) Anthropomorphic head phantom, where the brace indicates the position of the two adjacent slices [numbers 20 and 21 (Ref. )] at the height of the bridge of the nose, which we used for the dose measurements. Two OSLDs were placed on the surface of the head at the location of the eye lenses. (b) The particular dosimeter locations inside the phantom: Nos. 1–8 mark the OSLDs in the brain, near its base, Nos. 9 and 10 mark the two OSLDs near the optic nerves, and Nos. 11 and 12 mark the OSLDs in the eye globes.

Image of FIG. 2.
FIG. 2.

Reconstructed images of (a) the first module of the ACR accreditation phantom containing the high contrast cylinders and (b) the second module of the ACR accreditation phantom containing the low contrast cylinders. Due to the very narrow windowing level with which the low-contrast module is shown, the outer ring of the phantom is not visible so that it looks smaller than the first module.

Image of FIG. 3.
FIG. 3.

MTF for the standard (a) and bone (b) reconstruction for the three different scanners. Solid line: GE Discovery CT750 HD; dashed line: Siemens Definition; and dotted line: Philips Brilliance 64.

Image of FIG. 4.
FIG. 4.

NPS for the standard (a) and bone (b) reconstruction for the three different scanners. Solid line: GE Discovery CT750 HD; dashed line: Siemens Definition; and dotted line: Philips Brilliance 64.

Image of FIG. 5.
FIG. 5.

High-contrast CNR for the standard (a) and bone (b) reconstruction for the GE Discovery CT750 HD, Siemens Definition, and Philips Brilliance 64 scanners for the four high-contrast materials in the ACR phantom. Error bars represent ±1 standard deviation. Note that the “bone” kernel algorithm can vary significantly between the scanners affecting CNR results.

Image of FIG. 6.
FIG. 6.

MTF evaluated from the wire in a GE performance phantom versus the bead in the ACR CT accreditation phantom for the (a) standard and (b) bone reconstruction of the GE Discovery CT750 HD scanner with operating conditions delineated in Table I and preceding text.

Image of FIG. 7.
FIG. 7.

High-contrast CNR for the standard (a) and bone (b) reconstruction of images of the GE Discovery CT750 HD scanner acquired with TCM and 50% ASIR, 50% FPB (black bars) compared to the manually set current of 540 mA and 0% ASIR, 100% FBP (gray bars). Error bars represent ±1 standard deviation.

Tables

Generic image for table
TABLE I.

Clinically representative head-scan parameters used in our study. In the first part of the study, for all scanners we used manually set constant tube currents with 100% FBP reconstruction of images; in the second part of the study for the GE scanner, we used z-axis TCM associated with 50%–50% FBP-ASIR image reconstruction. CTDI entries are the values displayed on the scanner consoles following scanning.

Generic image for table
TABLE II.

Average values (mGy) of anthropomorphic-phantom dose measurements, routine head exam.

Generic image for table
TABLE III.

Low-contrast CNR for the standard and bone reconstruction of the three scanners. CNR values in parentheses represent one standard deviation.

Generic image for table
TABLE IV.

Average values (mGy) of anthropomorphic-phantom dose measurements, routine head exam for the GE Discovery CT750 HD, TCM versus manually fixed tube current.

Generic image for table
TABLE V.

Low-contrast CNR for the standard and bone reconstruction of images of the GE Discovery CT750 HD scanner.

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/content/aapm/journal/medphys/40/8/10.1118/1.4815964
2013-07-24
2014-04-18
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: CT head-scan dosimetry in an anthropomorphic phantom and associated measurement of ACR accreditation-phantom imaging metrics under clinically representative scan conditions
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/40/8/10.1118/1.4815964
10.1118/1.4815964
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