Development of a dynamic phantom and investigation of mobile target imaging and irradiation in preclinical small animal research.
OBJECTIVE
Progress made in preclinical radiotherapy makes respiratory gating reachable. Nevertheless, technical means are still needed, as well as accurate investigations of the effect of motion on small animal treatment plans.


METHODS
An animal-scaled dynamic phantom (0.3-11.1-mm motion peak-to-peak amplitude, 30-120 cycles per minute) was developed and characterized. It was used to evaluate respiratory monitoring and high resolution imaging (μPET/CT scans). The width and position variations of a fluorine-18 solution were measured for various motions and gating configurations. The phantom was finally used to measure the impact of motion on dose distribution for vertical irradiation using 2.5- and 5-mm collimations.


RESULTS
Phantom motions accurately reproduced original waveforms with good rate and amplitude linearity (R2= 1 and R2= 0.9995, respectively). µPET/CT acquisitions showed an increase of 92% of the target size caused by a 4.9-mm sine motion and reduced to <12% by gating. Target motion measurements showed consistency better than 18% between modalities. Irradiations showed that motions >0.8 and 1.1 mm (for the 2.5- and 5-mm collimations, respectively) significantly impact dose homogeneity in the target.


CONCLUSIONS
The phantom allowed studying motion in small animal imaging and irradiation. It showed the important impact of motions >2 mm and provided accurate data to improve the management of mobile tumour irradiation. The implementation of gated irradiation, associated with motion-compensated imaging, is currently under progress. Advances in knowledge: Small animal irradiation gating is not yet used in preclinical studies. As few solutions are under development, tools and accurate studies are highly needed.
1 Grand Accélérateur National d'Ions Lourds (GANIL), CEA/DRF-CNRS/IN2P3, Boulevard Henri Becquerel, 14076 Caen, France.|2 Advanced Resource Centre for Hadrontherapy in Europe (ARCHADE) Program, Caen, France.
Anne-Marie
AM
Frelin-Labalme
3 CEA, DRF, I2BM, LDM-TEP, GIP Cyceron, Boulevard Henri Becquerel, 14074 Caen, France.
Vincent
V
Beaudouin
D000818:Animals; D051379:Mice; D009068:Movement; D019047:Phantoms, Imaging; D000072078:Positron Emission Tomography Computed Tomography; D011879:Radiotherapy Dosage; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012119:Respiration