iaea human health series publications - SEDIM

TABLE 14. ACCEPTABLE AND ACHIEVABLE VALUES FOR SDNR USED FOR AEC EVALUATION:1 mm THICK PMMA CONTRAST OBJECT (cont.)GE DS 3.4 5.61 3.0 5.0 2.5 4.1GE Essential 5.2 7.9 4.6 7.0 3.9 6.0Hologic Selenia 1.5 2.6 1.3 2.2 1.0 1.8IMS Giotto 2.9 4.6 2.6 4.0 2.1 3.4Carestream CR (M2 plate) 3.8 5.8 3.3 5.1 2.8 4.4Carestream CR (M3 plate) aPMMA thickness (mm)20 45 70System Acceptable Achievable Acceptable Achievable Acceptable AchievableKonica CRRP-6MRP-7MCP-1M4.63.42.37.15.33.84.12.92.06.24.63.33.52.51.75.44.02.8Planmed Nuance 1.2 2.0 1.6 2.7 2.4 3.9Sectra D40 0.9 1.7 0.8 1.5 0.6 1.2Sectra L30 0.9 1.7 0.8 1.5 0.6 1.2Siemens Novation DR 1.6 2.7 1.4 2.4 1.1 2.0Siemens Inspiration 1.3 2.2 1.1 1.9 0.9 1.6aNo data available.(b)Density control(1) The density control should allow the operator to make adjustments to the mAs as large as 25–100% upwardand 25–50% downward from the ‘0’ or ‘normal’ position.8.4.2.5. Recommendations for corrective action(1) If the performance criteria for SDNR are not met, the medical physicist should determine that theperformance of the detector has not changed, using the methods described in Section 8.5. If the detector isoperating properly, the AEC should be adjusted or the technique chart should be revised, as required. Thetechniques chosen should not result in an exposure time greater than 5.0 s for 70 mm of PMMA, and theexposure time should be less than 2.5 s for a 45 mm PMMA slab. These time limits do not apply to scanningtype systems.(2) If the density control does not provide the appropriate range of control, it should be adjusted.(3) If the exposure time exceeds the maximum acceptable time, the reason for low tube output should beinvestigated.8.4.2.6. Time frame for corrective actionFor Part (a), corrective action should be taken immediately, before any further patients are imaged. ForPart (b), corrective action should be taken at the next regular servicing of the equipment.92