Attenuation change of lung nodules according to variation of examination techniques in low dose CT using iterative reconstruction: A phantom study

Purpose: To evaluate attenuation change of lung nodules and diagnostic performance of CT densitometry for detecting calcification according to tube voltage and current setting in low-dose CT using iterative reconstruction (IR). Material and Methods: CT images of an anthropomorphic phantom containing 14 artificial nodules (7-10 mm) with various mean attenuations (82-402 HU on standard dose) were obtained with 64- and 128-detector-row CT scanners using a standard (120kVp/100mA) and various low-dose settings (80, 100, and 120 kVp; 10-100 mAs) with IR. Mean and standard deviation (SD) of nodule attenuation (HU) were compared according to variation of tube voltages and current settings. As a threshold of 200 HU to determine calcified lesion, diagnostic performance of CT densitometry in low dose techniques was compared with those in standard dose CT. Results: Mean attenuation of nodules increased as the tube voltage decreased and SD increased as the tube voltage and current decreased in both CT scanners (p Conclusion: Although mean attenuation and SD of lung nodules changed variably according to combination of tube current and voltages, densitometry could be applicable for detection of calcification in low dose CT using IR techniques except very low tube current techniques.