Skip to main content

A delta-scatter Monte Carlo model of a rotating parallel-hole collimator for131i brain tumor imaging

Publication ,  Journal Article
Tenney, CR; Bowsher, JE; Jaszczak, RJ
Published in: IEEE Nuclear Science Symposium Conference Record
December 1, 2004

We investigate the collimator response and sensitivity of a lead rotating parallel-hole collimator (RPHC), 6.4 cm thick, with 1.45 nun hexagonal holes and 2.0 mm septa, designed to image 131I emissions (364.5 keV, 82%). The collimator is rotated to each of three positions during imaging to to give data for three independent, offset hole arrays, filling the septal shadows in each array with data from the other two arrays. Collimator response can be incorporated into the reconstruction algorithm to improve image quality. Simple geometric calculations of collimator response do not account for Compton scatter. For 131I, the effects of downscatter into the photopeak from high-energy emissions (637 keV, 6.5%, and 723 keV, 1.7%) are not obvious. A Monte Carlo model incorporating delta scattering is used to investigate downscatter and primary transmission. For initial studies, a perfectly absorbing detector is used. The RPHC is modelled as plate a 6.4 cm thick, with photon path lengths chosen randomly using the attenuation coefficient of lead. For interaction points determined to be in holes, photons are allowed to continue unimpeded (delta scatter). This increases the number of path lengths generated, but greatly decreases the number of boundary intersection calculations. Point sources are modelled from 2.5 cm to 25 cm from the collimator both on and off of hole axes. At short distances, photons are seen through one hole or a small number of holes. As distance increases, changes in the response and sensitivity are clearly seen. Downscatter presents little problem, constituting less than 10% of the detected counts except when the point source is close to the collimator, and between holes, i.e., in the septal shadows. Data for these areas will be filled in as the collimator is moved to other rotational positions. © 2004 IEEE.

Duke Scholars

Published In

IEEE Nuclear Science Symposium Conference Record

ISSN

1095-7863

Publication Date

December 1, 2004

Volume

5

Start / End Page

3084 / 3088
 

Citation

APA
Chicago
ICMJE
MLA
NLM
Tenney, C. R., Bowsher, J. E., & Jaszczak, R. J. (2004). A delta-scatter Monte Carlo model of a rotating parallel-hole collimator for131i brain tumor imaging. IEEE Nuclear Science Symposium Conference Record, 5, 3084–3088.
Tenney, C. R., J. E. Bowsher, and R. J. Jaszczak. “A delta-scatter Monte Carlo model of a rotating parallel-hole collimator for131i brain tumor imaging.” IEEE Nuclear Science Symposium Conference Record 5 (December 1, 2004): 3084–88.
Tenney CR, Bowsher JE, Jaszczak RJ. A delta-scatter Monte Carlo model of a rotating parallel-hole collimator for131i brain tumor imaging. IEEE Nuclear Science Symposium Conference Record. 2004 Dec 1;5:3084–8.
Tenney, C. R., et al. “A delta-scatter Monte Carlo model of a rotating parallel-hole collimator for131i brain tumor imaging.” IEEE Nuclear Science Symposium Conference Record, vol. 5, Dec. 2004, pp. 3084–88.
Tenney CR, Bowsher JE, Jaszczak RJ. A delta-scatter Monte Carlo model of a rotating parallel-hole collimator for131i brain tumor imaging. IEEE Nuclear Science Symposium Conference Record. 2004 Dec 1;5:3084–3088.

Published In

IEEE Nuclear Science Symposium Conference Record

ISSN

1095-7863

Publication Date

December 1, 2004

Volume

5

Start / End Page

3084 / 3088