Abstract
An Advanced Markus chamber on the surface of solid water phantom was used to determine surface dose reduction, with either a lead or air interface, as a function of surface-interface separation (t). The beam quality dependence of dose reduction was investigated using the 50 kV, 100 kV and 150 kV beams of an Xstrahl 150 superficial X-ray unit. For each beam the dose correction factor, DCF(t), namely the ratio of surface dose (t) to surface dose (t = 100 mm), was determined. Monte Carlo simulations of DCF(t) with a lead interface were compared with corresponding measured values. Simulated spectra were calculated at the phantom surface for full backscatter (t = 100 mm) and with either a lead or air interface at 2 mm or 8 mm depth. For each depth and beam quality lead fluorescent radiation at the surface was evident. The variation of DCF(t) for each beam and field size exhibits a minima at t ≈ 5 mm and in the range 1 mm ≤ t ≤ 40 mm surface dose reduction is larger for 100 kV than 150 kV. Monte Carlo simulated DCF(t) are consistent with corresponding measured DCF(t). From simulated spectra L-series fluorescent X-rays (≈ 15 keV) emanating from lead at t = 2 mm are evident for all beams and fluorescent K-series X-rays only occur with 100 kV and 150 kV beams.
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References
Klevenhagen SC (1982) The buildup of backscatter in the energy range 1 mm to 8 mm Al HVT. Phys Med Biol 27:1035–1043
Lanzon P, Sorell G (1993) The effect of lead underlying water on the backscatter of X-rays of beam qualities 0.5-8 mm Al HVT. Phys Med Biol 38:1137–1144
Huq MS, Venkataramanan N, Meli JA (1992) The effect on dose of kilovoltage X-rays backscattered from lead. Int J Radiat Oncol Biol Phys 24:171–175
Das IJ, Chopra KL (1995) Backscatter dose perturbation in kilovoltage photon beams at high atomic number interface. Med Phys 22:767–773
Hill R, Healy B, Holloway L, Baldock C (2007) An investigation of dose changes for therapeutic kilovoltage X-ray beams with underlying lead shielding. Med Phys 34:3045–3053
Healy BJ, Sylvander S, Nitschke KN (2008) Dose reduction from loss of backscatter in superficial X-ray radiation therapy with the Pantak SXT 150 unit. Aust Phys Eng Sci Med 31:49–55
Paix D, Taylor K, Holloway A (1983) Backscatter of diagnostic X-rays from metals (communication). Med Phys 10:112–3
Yu PKN, Butson MJ (2013) Measurement of effects of nasal and facial shields on delivered dose for superficial X-ray treatments. Phys Med Biol 58:N95–N102
Butson JB, Cheung T, Yu PKN (2008) Measurement of dose reductions for superficial a-rays backscattered from bone interfaces Phys. Med Biol 53:N329–N336
Baines J, Zawlodzka S, Markwell T, Chan M (2018) Measured and Monte Carlo simulated surface dose reduction for superficial X-rays incident on tissue with underlying air or bone. MedPhys 45:926–933
Healy BJ, Gibbs A, Murry RL, Prunster JE, Nitschke KN (2005) Output factor measurements for a kilovoltage X-ray therapy unit. Austr Phys Eng Sci Med 28:115–121
Kawrakow I, Rogers DWO (2000) The EGSnrc code system: Monte Carlo simulation of electron and photon transport. NRCC Report PIPRS – 701, Ottawa
Rogers DW, Kawrakow J, Seuntjens BR, Walters B, Mainegra-Hing E (2000) NRC user codes for EGSnrc, NRCC Report No. PIRS-702
Rogers DWO, Faddegon BA, Ding GX, Ma CM, Wei J, Mackie TR (1995) BEAM: a Monte Carlo code to simulate radiotherapy treatment units. Med Phys 22:503–24
Walters B, Kawrakov I, Rogers DWO (2011) DOSXYZnrc users manual NRCC Report PIRS-794revB. NRCC, Ottawa
Ma CM, Rogers DWO (2018) BEAMDP users manual. NRCC Report PIRS-0509(C)revA. NRCC, Ottawa
Mainegra-Hing E, Kawrakow I (2006) Efficient X-ray tube simulations Med Phys 33:2683–2690
Andreo P, Burns DT, Salvat F (2012) On the uncertainties of photon mass energy-absorption coefficients and their ratios for radiation dosimetry. Phys Med Biol 57:2117–2136
Chow JCL, Owrangi AM (2012) Surface dose reduction from bone interface in kilovoltage X-ray therapy: a Monte Carlo study of photon spectra. J App Clin Med Phys 13:215–221
NIST (2019) X-ray mass attenuation coefficients. http://physics.nist.gov/PhysRefData/XrayMassCoef
Eaton JE, Doolan PJ (2013) Review of backscatter measurement in kilovoltage radiotherapy using novel detectors and reduction from lack of underlying scattering material. J Appl Clin Med Phys 14:5–17
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John Baines declares that he has no conflict of interest. Sylwia Zawlodzka declares that she has no conflict of interest. Tim Markwell declares that he has no conflict of interest. Millicent Chan declares that she has no conflict of interest.
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Baines, J., Zawlodzka, S., Markwell, T. et al. The effect of fluorescence on surface dose with superficial X-rays incident on tissue with underlying lead. Australas Phys Eng Sci Med 42, 211–220 (2019). https://doi.org/10.1007/s13246-019-00732-x
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DOI: https://doi.org/10.1007/s13246-019-00732-x