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Investigating the accuracy of microstereotactic-body-radiotherapy utilizing anatomically accurate 3D printed rodent-morphic dosimeters.

Publication ,  Journal Article
Bache, ST; Juang, T; Belley, MD; Koontz, BF; Adamovics, J; Yoshizumi, TT; Kirsch, DG; Oldham, M
Published in: Med Phys
February 2015

PURPOSE: Sophisticated small animal irradiators, incorporating cone-beam-CT image-guidance, have recently been developed which enable exploration of the efficacy of advanced radiation treatments in the preclinical setting. Microstereotactic-body-radiation-therapy (microSBRT) is one technique of interest, utilizing field sizes in the range of 1-15 mm. Verification of the accuracy of microSBRT treatment delivery is challenging due to the lack of available methods to comprehensively measure dose distributions in representative phantoms with sufficiently high spatial resolution and in 3 dimensions (3D). This work introduces a potential solution in the form of anatomically accurate rodent-morphic 3D dosimeters compatible with ultrahigh resolution (0.3 mm(3)) optical computed tomography (optical-CT) dose read-out. METHODS: Rodent-morphic dosimeters were produced by 3D-printing molds of rodent anatomy directly from contours defined on x-ray CT data sets of rats and mice, and using these molds to create tissue-equivalent radiochromic 3D dosimeters from Presage. Anatomically accurate spines were incorporated into some dosimeters, by first 3D printing the spine mold, then forming a high-Z bone equivalent spine insert. This spine insert was then set inside the tissue equivalent body mold. The high-Z spinal insert enabled representative cone-beam CT IGRT targeting. On irradiation, a linear radiochromic change in optical-density occurs in the dosimeter, which is proportional to absorbed dose, and was read out using optical-CT in high-resolution (0.5 mm isotropic voxels). Optical-CT data were converted to absolute dose in two ways: (i) using a calibration curve derived from other Presage dosimeters from the same batch, and (ii) by independent measurement of calibrated dose at a point using a novel detector comprised of a yttrium oxide based nanocrystalline scintillator, with a submillimeter active length. A microSBRT spinal treatment was delivered consisting of a 180° continuous arc at 225 kVp with a 20 × 10 mm field size. Dose response was evaluated using both the Presage/optical-CT 3D dosimetry system described above, and independent verification in select planes using EBT2 radiochromic film placed inside rodent-morphic dosimeters that had been sectioned in half. RESULTS: Rodent-morphic 3D dosimeters were successfully produced from Presage radiochromic material by utilizing 3D printed molds of rat CT contours. The dosimeters were found to be compatible with optical-CT dose readout in high-resolution 3D (0.5 mm isotropic voxels) with minimal artifacts or noise. Cone-beam CT image guidance was possible with these dosimeters due to sufficient contrast between high-Z spinal inserts and tissue equivalent Presage material (CNR ∼10 on CBCT images). Dose at isocenter measured with optical-CT was found to agree with nanoscintillator measurement to within 2.8%. Maximum dose in line profiles taken through Presage and film dose slices agreed within 3%, with FWHM measurements through each profile found to agree within 2%. CONCLUSIONS: This work demonstrates the feasibility of using 3D printing technology to make anatomically accurate Presage rodent-morphic dosimeters incorporating spinal-mimicking inserts. High quality optical-CT 3D dosimetry is feasible on these dosimeters, despite the irregular surfaces and implanted inserts. The ability to measure dose distributions in anatomically accurate phantoms represents a powerful useful additional verification tool for preclinical microSBRT.

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Published In

Med Phys

DOI

EISSN

2473-4209

Publication Date

February 2015

Volume

42

Issue

2

Start / End Page

846 / 855

Location

United States

Related Subject Headings

  • Surgery, Computer-Assisted
  • Rats
  • Radiotherapy Planning, Computer-Assisted
  • Radiotherapy Dosage
  • Radiosurgery
  • Radiometry
  • Printing, Three-Dimensional
  • Phantoms, Imaging
  • Nuclear Medicine & Medical Imaging
  • Nanotechnology
 

Citation

APA
Chicago
ICMJE
MLA
NLM
Bache, S. T., Juang, T., Belley, M. D., Koontz, B. F., Adamovics, J., Yoshizumi, T. T., … Oldham, M. (2015). Investigating the accuracy of microstereotactic-body-radiotherapy utilizing anatomically accurate 3D printed rodent-morphic dosimeters. Med Phys, 42(2), 846–855. https://doi.org/10.1118/1.4905489
Bache, Steven T., Titania Juang, Matthew D. Belley, Bridget F. Koontz, John Adamovics, Terry T. Yoshizumi, David G. Kirsch, and Mark Oldham. “Investigating the accuracy of microstereotactic-body-radiotherapy utilizing anatomically accurate 3D printed rodent-morphic dosimeters.Med Phys 42, no. 2 (February 2015): 846–55. https://doi.org/10.1118/1.4905489.
Bache ST, Juang T, Belley MD, Koontz BF, Adamovics J, Yoshizumi TT, et al. Investigating the accuracy of microstereotactic-body-radiotherapy utilizing anatomically accurate 3D printed rodent-morphic dosimeters. Med Phys. 2015 Feb;42(2):846–55.
Bache, Steven T., et al. “Investigating the accuracy of microstereotactic-body-radiotherapy utilizing anatomically accurate 3D printed rodent-morphic dosimeters.Med Phys, vol. 42, no. 2, Feb. 2015, pp. 846–55. Pubmed, doi:10.1118/1.4905489.
Bache ST, Juang T, Belley MD, Koontz BF, Adamovics J, Yoshizumi TT, Kirsch DG, Oldham M. Investigating the accuracy of microstereotactic-body-radiotherapy utilizing anatomically accurate 3D printed rodent-morphic dosimeters. Med Phys. 2015 Feb;42(2):846–855.

Published In

Med Phys

DOI

EISSN

2473-4209

Publication Date

February 2015

Volume

42

Issue

2

Start / End Page

846 / 855

Location

United States

Related Subject Headings

  • Surgery, Computer-Assisted
  • Rats
  • Radiotherapy Planning, Computer-Assisted
  • Radiotherapy Dosage
  • Radiosurgery
  • Radiometry
  • Printing, Three-Dimensional
  • Phantoms, Imaging
  • Nuclear Medicine & Medical Imaging
  • Nanotechnology