Low dose chest CT protocol (50 mAs) as a routine protocol for comprehensive assessment of intrathoracic abnormality

• We planned to confirm the efficiency of low dose CT protocol at 50 mAs as a routine protocol.
• We examined the difference in the diagnostic result between the low dose CT images and standard dose CT image protocol.
• Fundamental chest CT abnormal findings including both lung and soft tissue abnormality were recorded and compared between two protocols.
• The difference in the diagnostic result of a reader from the other two readers is not greater in low dose CT images.
• The result of present study supported the use of routine low dose CT protocol.

PurposeTo determine the diagnostic capability of low-dose CT (50 mAs) in comparison to standard-dose CT (150 mAs).Materials and methodsFifty-nine consecutive patients underwent two non-contrast chest CT scans with different current-time products (50 and 150 mAs at 120 kVp) on a 64-detector row CT scanner. Three board certified chest radiologists independently reviewed 118 series of 2 mm-thick images (2 series for each of 59 patients) in a random order. The readers assessed abnormal findings including emphysema, ground-glass opacity, reticular opacity, micronodules, bronchiectasis, honeycomb, nodules (>5 mm), aortic aneurysm, coronary artery calcification, pericardial and pleural effusion, pleural thickening, mediastinal tumor and lymph node enlargement. Five-point scale from 1 (definitely absent) to 5 (definitely present) was used to record the results. The rates of score agreement between two images were calculated. Deviation of one observer's score from other two observers was compared between low dose CT and standard dose CT.ResultsMean agreement rate of the lung parenchymal findings between low dose CT and standard dose CT images was 0.836 (range, 0.746–0.926). Mean agreement rates for mediastinal and pleural findings were 0.920 (range, 0.735–1.000). There was no statistically significant difference in the deviation of the observers' scores between low-dose CT and standard-dose CT.ConclusionLow dose CT protocol at 50 mAs can produce the screening results consistent with standard dose CT protocol (150 mAs), supporting routine use of low dose chest CT protocol.