To avoid these consequences of a constant noise requirement, a noise index technique chart can be used to manually adjust tube current modulation for patient size. Such a technique chart would prescribe different noise index values for different patient sizes, using lower noise indices for small patients and higher noise indices for obese patients. This approach has been recommended by others based on clinical experience.20,24 This approach provides sufficient image quality in pediatric patients and avoids excessive radiation doses in obese patients. In addition, some manufacturers allow the user to set both minimum and maximum tube current values. If appropriately set, these values can prevent either an excessive decrease (in small patients) or increase (in large patients) of the tube current. The noise index technique chart used in our adult abdomen CT practice for a system (GE LightSpeed VCT; GE Healthcare, Milwaukee, WI) that uses a constant noise AEC paradigm is shown in Table 3. The same approach could be adapted to build noise index technique charts for other scanners with AEC using a constant noise paradigm.22
To avoid these consequences of a constant noise requirement, a noise index technique chart can be used to manually adjust tube current modulation for patient size. Such a technique chart would prescribe different noise index values for different patient sizes, using lower noise indices for small patients and higher noise indices for obese patients. This approach has been recommended by others based on clinical experience.20,24 This approach provides sufficient image quality in pediatric patients and avoids excessive radiation doses in obese patients. In addition, some manufacturers allow the user to set both minimum and maximum tube current values. If appropriately set, these values can prevent either an excessive decrease (in small patients) or increase (in large patients) of the tube current. The noise index technique chart used in our adult abdomen CT practice for a system (GE LightSpeed VCT; GE Healthcare, Milwaukee, WI) that uses a constant noise AEC paradigm is shown in Table 3. The same approach could be adapted to build noise index technique charts for other scanners with AEC using a constant noise paradigm.22
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