A portable secondary dose monitoring system using scintillating fibers for proton therapy of prostate cancer: A Geant4 Monte Carlo simulation study

Biniam Tesfamicael, Paul Gueye, Stephen Avery, Donald Lyons, Mahadevappa Mahesh


Purpose: The main purpose of this study was to monitor the secondary dose distribution originating from a water phantom during proton therapy of prostate cancer using scintillating fibers.

Methods: The Geant4 Monte Carlo toolkit version 9.6.p02 was used to simulate a proton therapy of prostate cancer. Two cases were studied. In the first case, 8 × 8 = 64 equally spaced fibers inside three 4 × 4 × 2.54 cm3 Delrin® blocks were used to monitor the emission of secondary particles in the transverse (left and right) and distal regions relative to the beam direction. In the second case, a scintillating block with a thickness of 2.54 cm and equal vertical and longitudinal dimensions as the water phantom was used. Geometrical cuts were implemented to extract the energy deposited in each fiber and inside the scintillating block.

Results: The transverse dose distributions from the detected secondary particles in both cases are symmetric and agree to within <3.6%. The energy deposited gradually increases as one moves from the peripheral row of fibers towards the center of the block (aligned with the center of the prostate) by a factor of approximately 5. The energy deposited was also observed to decrease as one goes from the frontal to distal region of the block. The ratio of the energy deposited in the prostate to the energy deposited in the middle two rows of fibers showed a linear relationship with a slope of (-3.55±2.26) × 10-5 MeV per treatment Gy delivered. The distal detectors recorded a negligible amount of energy deposited due to higher attenuation of the secondary particles by the water in that direction.

Conclusion: With a good calibration and with the ability to define a good correlation between the radiation flux recorded by the external fibers and the dose delivered to the prostate, such fibers can be used for real time dose verification to the target. The system was also observed to respond to the series of Bragg Peaks used to generate the Spread Out Bragg Peak inside the water phantom. Such Bragg Peaks were detected by the fibers. The energy deposited inside the lateral blocks were also observed to decrease as one goes away from the beam nozzle due to increased attenuation.


Proton Therapy, Prostate Cancer, Scintillating Fibers, Geant4, Hadrontherapy, Secondary Dose

Full Text:



Wilson RR. Radiological use of fast protons. Radiology.1946;47:487-91.

Miller DW. A review of proton beam radiation therapy. Med Phys. 1995;22:1943-54.

Hill-Kayser CE, Both S, Tochner Z. Proton Therapy: Ever Shifting Sands and the Opportunities and Obligations within. Front Oncol. 2011;1:24.

Fontenot JD, Lee AK, Newhauser WD. Risk of secondary malignant neoplasms from proton therapy and intensity-modulated x-ray therapy for early-stage prostate cancer. Int J Radiat OncolBiol Phys. 2009;74:616-22.

Levin WP, Kooy H, Loeffler JS, DeLaney TF.Proton beam therapy.Br J Cancer. 2005;93:849-54.

Newhauser WD, Giebeler A, Zhu R, et al. Uncertainty in dose per monitor unit estimates for passively scattered proton therapy: The role of compensator and patient scatter in prostate cases. Jour Proton Ther. 2015;1:116.

Rana S, Pokharel S, Zheng Y, et al. Treatment planning study comparing proton therapy, RapidArc and IMRT for a synchronous bilateral lung cancer case. Int J Cancer Ther Oncol. 2014; 2:020216.

Slater JD. Clinical applications of proton radiation treatment at Loma Linda University: review of a fifteen-year experience. Technol Cancer Res Treat. 2006;5:81-9.

Perez-Andujar A, Newhauser WD, Deluca PM. Neutron Production from beam modifying devices in a modern double scattering proton therapy beam delivery system. Phys Med Biol. 2009; 54:993-1008.

Zheng Y, Newhauser W, Klein E, Low D. Monte Carlo simulation of the neutron spectral fluence and dose equivalent for use in shielding a proton therapy vault.Phys Med Biol. 2009; 54:6943-57.

Agosteo S, Birattari C, Caravaggio M, et al. Secondary neutron and photon dose in proton therapy. RadiotherOncol.1998;48:293-305.

Binns PJ, Hough JH. Secondary dose exposures during 200 mev proton therapy. Radiat Prot Dosimetry. 1997;70:441-4.

Polf JC, Newhauser WD. Calculations of neutron dose equivalent exposures from range-modulated proton therapy beams. Phys Med Biol. 2005;50:3859-73.

Yan X, Titt U, Koehler AM, Newhauser WD. Measurement of neutron dose equivalent to proton therapy patients outside of the proton radiation field. NuclInstrum Methods Phys Res. 2002;476:429-34.

Schneider U, Agosteo S, Pedroni E, Besserer J. Secondary neutron dose during proton therapy using spot scanning. Int J Radiat Oncol Biol Phys. 2002;53:244-51.

Murray L, Henry A, Hoskin P, et al. Second primary cancers after radiation for prostate cancer: a review of data from planning studies. Radiat Oncol. 2013;8:172.

Brenner DJ, Hall EJ. Secondary neutrons in clinical proton radiotherapy: a charged issue. Radiother Oncol. 2008;86:165-170.

Stefano A, Allison J, AmakoK, et al. Geant4 – A simulation toolkit. Nucl Instrum Methods Phys Res. 2003; 506:250-303.

Allison J, Amako K, Araujo H, et al. Geant4 developments and applications. IEEE Trans Nucl Sci. 2006; 53:270-8.

Tesfamicael BY, Avery S, Gueye P, et al. Scintillating fiber based in-vivo dose monitoring system to the rectum in proton therapy of prostate cancer: A Geant4 Monte Carlo simulation. Int J Cancer Ther Oncol. 2014; 2:02024.

Cirrone GAP, Cuttone G, Di Rosa F, et al. Validation of geant4 physics models for the simulation of the proton Bragg Peak. Proc. IEEE Nucl Sci Simp. 2006;6:788-92.

Cirrone GAP, Cuttone G, Di Rosa F, et al. The geant4 toolkit capability in the hadron therapy field: simulation of a transport beam line. Nucl Phys B - Proc Suppl. 2006;150:54-7.

Cirrone GAP, Cuttone G, Guatelli S, et al. Implementation of a new Monte Carlo-GEANT4 simulation tool for the development of a proton therapy beam line and verification of the related dose distributions. IEEE Trans Nucl Sci. 2005;52:262-5.

Cirrone GAP, Cuttone G,MazzagliaSE, et al. Hadrontherapy: a geant4 based tool for proton/ion therapy studies. IEEE Trans Nucl Sci.2011;2:207-12.

Cirrone GAP, Cuttone G, Di Rosa F, et al. Monte Carlo based implementation of an energy modulation system for proton therapy. IEEE Nucl Sci Simp. 2004;4:2133-7.

Available from https://root.cern.ch/drupal/[Accessed on 1/21/2015]

Wroe A, Rosenfeld A, Schulte R. Out-of-field dose equivalents delivered by proton therapy of prostate cancer. Med Phys.2007;34:3449-56.

DOI: http://dx.doi.org/10.14319/ijcto.41.15

Creative Commons License
This work is licensed under a Creative Commons Attribution 3.0 License.


International Journal of Cancer Therapy and Oncology (ISSN 2330-4049)

© International Journal of Cancer Therapy and Oncology (IJCTO)

To make sure that you can receive messages from us, please add the 'ijcto.org' domain to your e-mail 'safe list'. If you do not receive e-mail in your 'inbox', check your 'bulk mail' or 'junk mail' folders.


Number of visits since October, 2013