Gamma cameras calibration for I-131 uptake quantification in hyperthyroidism diseases

Abstract

Optimization and verification of Patient- Specific Treatment planning with unsealed I-131 sources is a desirable goal from medical and radiation protection point of view. To obtain a practical protocol to combine the estimation of the related parameters with patient’s specific treatment dose in hyperthyroidism diseases, four equipments were studied (Iodine Probe, a Philips Forte Camera with pin-hole collimators, a Mediso Nucline with HEGP for planar and SPECT techniques and a Mediso AnySan SPECT/CT). The linear behaviour on diagnostic and therapeutic activity range was verified, showing a linear correlation fitting factor R2 > 0.99. The differences between thyroid uptake determinations in all equipment were less than 6% for therapeutic activities and less than 1.1% in the diagnostic range. The combined protocol to calculate, with only one administration of I131, all the necessary parameters to the treatment dose estimation in 2D or 3D, was established and verified, avoiding wasting time with gamma cameras. Following this protocol the difference between apparent and calculated activities were less than 3%.