| Abstract [eng] |
Collimator is a major component of the gamma camera. The quality of obtained images depends on collimator. The most common material for collimators is lead. Due to the high price, commercial application of other materials, like tungsten, tantalum or gold is limited. Following the recommendations of the European Commission directive 2011/65/EU, application of toxic lead in electronic devices including medical devices was limited. Due to this there is a need to find new alternative materials that are characterized by good X-ray absorption characteristics and may replace toxic lead. In this work, we present a new liquid phase material which has good X-ray absorption properties and could be used as a filler for a new type of collimator construction. Five different concentrations of silicotungstic acid solution (15 %, 30 %, 45 %, 60 %, 79.69% (a saturated solution)) have been produced to investigate their x-ray absorption properties. Calculated lead equivalent was 0.164 mmPb, 0.185 mmPb, 0.251 mmPb, 0.362 mmPb, 0.576 mmPb, respectively. It was found that the most suitable solution for the collimator filler was 45 % concentrated silicotungstic acid. Two different experimental collimator constructions have been produced: one with integrated single tube and another one with different diameter tubes. Constructions were irradiated to 1 Gy in X-ray therapy unit. Dose distribution under collimator construction was recorded in GafChromic film. It was found that the reduction of the tube diameter causes decrease of dose. The average dose under collimator was 0.03 Gy. Spatial resolution of tubes having different diameters was also calculated and it was found that they varied from 5.93 cm to 1.78 cm. |
