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Original ArticleOpen Access
Comparison of Low Dose and Standard Dose MDCT in Detection of Metastatic Pulmonary Nodules
Muangman N 
,
Maitreesorrasan N ,
Totanarungroj K
,
Maitreesorrasan N ,
Totanarungroj K Objective: Compare low dose (50 mA) and standard dose (300 mA) MDCT in detection of metastatic pulmonary nodules inextrathoracic malignant patients in Siriraj hospital.
Material and Method: Prospectively, 58 patients underwent chest CT examinations by 64-slice MDCT in non-enhancedphase with a reduced tube current of 50 mA (low-dose CT (LDCT)), followed by contrast-enhanced phase with a standardtube current of 300 mA (Standard-dose CT (SDCT)). Other parameter such as tube voltage 120 kVp, spiral pitch 0.984, andsection thickness 1.25 mm, were kept constant. Four hundred twenty two nodules found by SDCT and 427 nodules found byLDCT were analyzed.
Results: The sensitivity of LDCT was 94.7% for all nodules, 79% for nodules < 2 mm, 94.2% for nodules 2.1-3 mm, 97%for nodules 3.1-4 mm, and 100% for nodules 4.1-5 mm. Three types of nodules were found and classified as calcific nodule,non-calcific nodule, and ground-glass nodule of which sensitivity for detection in LDCT were 100% (p = 1.000), 95.9%(p = 0.337) and 77% (p = 0.581), respectively. Most common causes of discrepancy in SDCT were unseen nodules and inLDCT were end-on vessel nodules. Majority of discrepant nodules and retrospective nodules were < 3 mm. Effective doseranged from 0.78 mSv.-1.6 mSv in LDCT and 4.22-9.57 mSv in SDCT.
Conclusion: There is no statistical difference in detection of metastatic pulmonary nodules by using low-dose and standarddoseCT images. Low-dose CT images can used to follow-up the treatment responsiveness of the known patient, diagnosedto have pulmonary metastasis.
Keywords: Low dose CT scan, Pulmonary metastasis
Material and Method: Prospectively, 58 patients underwent chest CT examinations by 64-slice MDCT in non-enhancedphase with a reduced tube current of 50 mA (low-dose CT (LDCT)), followed by contrast-enhanced phase with a standardtube current of 300 mA (Standard-dose CT (SDCT)). Other parameter such as tube voltage 120 kVp, spiral pitch 0.984, andsection thickness 1.25 mm, were kept constant. Four hundred twenty two nodules found by SDCT and 427 nodules found byLDCT were analyzed.
Results: The sensitivity of LDCT was 94.7% for all nodules, 79% for nodules < 2 mm, 94.2% for nodules 2.1-3 mm, 97%for nodules 3.1-4 mm, and 100% for nodules 4.1-5 mm. Three types of nodules were found and classified as calcific nodule,non-calcific nodule, and ground-glass nodule of which sensitivity for detection in LDCT were 100% (p = 1.000), 95.9%(p = 0.337) and 77% (p = 0.581), respectively. Most common causes of discrepancy in SDCT were unseen nodules and inLDCT were end-on vessel nodules. Majority of discrepant nodules and retrospective nodules were < 3 mm. Effective doseranged from 0.78 mSv.-1.6 mSv in LDCT and 4.22-9.57 mSv in SDCT.
Conclusion: There is no statistical difference in detection of metastatic pulmonary nodules by using low-dose and standarddoseCT images. Low-dose CT images can used to follow-up the treatment responsiveness of the known patient, diagnosedto have pulmonary metastasis.
Keywords: Low dose CT scan, Pulmonary metastasis
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