Background: The necessity for early detection of pulmonary nodules to reduce the lung cancer burden needs a modality using the principle “as low a radiation dose as can reasonably be achieved” (ALARA) at the same time with acceptable image quality. Low–dose computed tomography (LDCT) with radiation dose equivalent to chest X–ray is an excellent tool in the early diagnosis as well as follow–up of pulmonary nodules.

Objective: To determine the sensitivity of the low–dose helical multidetector computed tomography (MDCT) in the detection and evaluation of pulmonary nodules in comparison with standard–dose helical MDCT and to correlate the imaging findings of the pulmonary nodules assessed by the low–dose helical MDCT with helical MDCT guided fine needle aspiration cytology.

Materials and Methods: This is a single–center cross–sectional analytical study, conducted over a period of two years on 53 adult patients, at Department of Radiodiagnosis in collaboration with Department of Respiratory Medicine and Department of Pathology in a medical institute at Imphal. All patients were subjected to both standard–dose and low–dose helical MDCT with the same CT machine and images were compared in terms of number of nodules, nodule size, and density.Final diagnosis was done by cytological examination by helical MDCT guided FNAC of the pulmonary nodules wherever possible.Radiation issues in terms of dose–length product and effective radiation dose were also compared between low–dose and standard–dose CT.

Results: Sensitivity of the low–dose helical MDCT against standard–dose helical MDCT in detecting < 5 mm sized nodules was 86.67% and 100% for ≥ 5 mm sized nodules. Overall sensitivity of LDCT in detecting pulmonary nodules was 99.44% as against SDCT with coefficient of determination (R²) for number of nodules detected per patient measuring 99.7%.Sensitivity of low–dose CT as against standard–dose CT in detecting both benign and indeterminate calcified nodules was 100% and for non–calcified, solid and sub–solid nodules were 98.26% and 100% respectively. Mean effective radiation dose was significantly lower in low–dose helical MDCT in comparison to standard–dose helical MDCT (p value = 0.000) in both male and female patients and total study population with 75.33% reduction in the effective radiation dose.

Conclusion: Low–dose helical MDCT can reliably be used in the evaluation as well as follow–up of pulmonary nodules with reduced radiation dose.