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Water-equivalent path length calibration of a prototype proton CT scanner
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Image of FIG. 1.
FIG. 1.

Schematic drawing of the pCT scanner prototype. The detector system consisting of silicon tracker planes and a segmented crystal calorimeter is exposed to a horizontal proton cone beam (not shown) generated by a thin lead foil located downstream of the proton beam line exit window. The phantom is located between the front and rear telescopes and is rotated in discrete angular steps during a pCT scan.

Image of FIG. 2.
FIG. 2.

Derivation of the system matrix of the pCT reconstruction problem using the reconstructed MLP of each proton.

Image of FIG. 3.
FIG. 3.

Example of tracks selected for individual crystal calibration.

Image of FIG. 4.
FIG. 4.

WET calibration set up with two polystyrene blocks. The beam enters from the right in this photograph. The enclosure on the right contains the front tracker, and the larger enclosure on the left contains the rear tracker and calorimeter.

Image of FIG. 5.
FIG. 5.

Histogram of the calorimeter response to a 200 MeV beam with no degrader. The Gaussian fit of the right side of the peak is shown.

Image of FIG. 6.
FIG. 6.

Calibration curve of calorimeter response versus water-equivalent path length for a 200 MeV beam. The curve was fitted with a second-degree polynomial.

Image of FIG. 7.
FIG. 7.

WEPL distribution recorded using the pCT scanner for a 1 cm thick muscle equivalent plate.

Image of FIG. 8.
FIG. 8.

Depth-dose range shift measured using a water phantom for a 1 cm thick muscle equivalent plate.

Image of FIG. 9.
FIG. 9.

Uncertainty of the single-proton WEPL measurement as a function of WEPL, for beam energies of 100 and 200 MeV, respectively.

Image of FIG. 10.
FIG. 10.

Axial reconstructed slice of the water phantom scanned with the pCT scanner prototype. The WEPL values for the reconstruction were derived using the calibration procedure described in this paper.

Image of FIG. 11.
FIG. 11.

Profile across the central band of the axial slice of the water phantom shown in Fig. 10. A central dip artifact can be seen at x = 8 cm and a larger ring artifact between 5 and 11 cm is noticeable. The 0.5 cm thick acrylic walls are seen as a slight rise at the edges of the profile.

Image of FIG. 12.
FIG. 12.

Histogram of RSP values for the water phantom excluding the central artifact and acrylic walls.


Generic image for table

Comparison of RSP measurements obtained using the pCT scanner and using a water phantom depth-dose range shift measurement.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Water-equivalent path length calibration of a prototype proton CT scanner