54 Part I Chapter 2 Quality control and improvement Gamma camera quality control A strict quality control programme should be routinely performed [50], according to the rules of each country, as stated in the Council Directive 2013/59/EURATOM. Quality control of the radiopharmaceutical The radioactive concentration should be determined by measuring the activity of the vial in a calibrated ionization chamber. Labelling efficiency should be >95%. Manufacturer’s instructions for assessment of radiochemical purity (e.g. by thin-layer chromatography) and local laws have to be followed. General safety procedures Infection control, and patient education concerns The injection must comply with local applicable guidelines and recommendations. The needle used for tracer injection must be collected in a needle container. Vials, syringes, injection needles, and gloves used for injection are stored in lead shielded containers until safe radioactive levels are attained (see 3. Radiation protection). Side effects or incidents should be reported according to applicable law. Radiation safety 1. Physiological distribution of 99mTc-phosphonates Phosphonates concentrate in the mineral part of bone, nearly two thirds in hydroxyapatite crystals and one third in calcium phosphate. Two major factors control the accumulation of phosphonates in bone, namely blood flow and extraction efficiency, which in turn depends on capillary permeability, acid-base balance, parathyroid hormone levels, etc. The peak of activity through the kidneys is reached after approximately 20 minutes. 2. Radiation dosimetry The organ which receives the largest radiation is bone (see table of adsorbed doses, ICRP no. 80, 1998) [56]. The estimated adsorbed radiation dose to various organs in healthy subjects following administration of 99mTc-labelled phosphates and phosphonates is given in table 6. It is assumed that 50% of the injected activity (IA) is absorbed by the skeleton with an uptake half-life of 15 minutes, 15% IA retains in the skeleton with a clearance half-life of 2 hours and the remaining 35% IA shows a clearance half-life of 3 days. In children the bone uptake concentrates in the