A directional 103 Pd brachytherapy device: Dosimetric characterization and practical aspects for clinical use

Brachytherapy. Mar-Apr 2017;16(2):421-432. doi: 10.1016/j.brachy.2016.11.011. Epub 2016 Dec 28.


Purpose: A brachytherapy (BT) device has been developed with shielding to provide directional BT for preferentially irradiating malignancies while sparing healthy tissues. The CivaSheet is a flexible low-dose-rate BT device containing CivaDots with 103Pd shielded by a thin Au disk. This is the first report of a clinical dosimetric characterization of the CivaSheet device.

Methods and materials: Radiation dose distributions near a CivaDot were estimated using the MCNP6 radiation transport code. CivaSheet arrays were also modeled to evaluate the dose superposition principle for treatment planning. The resultant data were commissioned in a treatment planning system (TPS) (VariSeed 9.0), and the accuracy of the dose superposition principle was evaluated for summing individual elements comprising a planar CivaSheet.

Results: The dose-rate constant (0.579 cGy/h/U) was lower than for 103Pd seeds due to Au L-shell x-rays increasing the air-kerma strength. Radial dose function values at 0.1, 0.5, 2, 5, and 10 cm were 1.884, 1.344, 0.558, 0.088, and 0.0046, respectively. The two-dimensional anisotropy function exhibited dramatic reduction between the forward (0°) and rearward (180°) directions by a factor of 276 at r = 0.1 cm, 24 at r = 1 cm, and 5.3 at r = 10 cm. This effect diminished due to increasingly scattered radiation. The largest gradient in the two-dimensional anisotropy function was in contact with the device at 92° due to the Au disk shielding. TPS commissioning and dose superposition accuracies were typically within 2%.

Conclusions: Simulations of the CivaDot yielded comprehensive dosimetry parameters that were entered into a TPS and deemed acceptable for clinical use. Dosimetry measurements of the CivaSheet are also of interest to the BT community.

Keywords: CivaSheet; Dosimetry; Monte Carlo methods.

MeSH terms

  • Anisotropy
  • Brachytherapy / instrumentation*
  • Brachytherapy / methods
  • Computer Simulation
  • Humans
  • Monte Carlo Method
  • Palladium / therapeutic use*
  • Radioisotopes / therapeutic use*
  • Radiometry
  • Radiotherapy Dosage


  • Radioisotopes
  • Palladium