Abstract
ObjectivesTo assess the image quality of 3 different ultralow-dose CT protocols on pulmonary nodule depiction in a ventilated ex vivo-system.Materials and methodsFour porcine lungs were inflated inside a dedicated chest phantom and prepared with n = 195 artificial nodules (0.5–1 mL). The artificial chest wall was filled with water to simulate the absorption of a human chest. Images were acquired with a 2x192-row detector CT using low-dose (reference protocol with a tube voltage of 120 kV) and 3 different ULD protocols (respective effective doses: 1mSv and 0.1mSv). A different tube voltage was used for each ULD protocol: 70kV, 100kV with tin filter (100kV_Sn) and 150kV with tin filter (150kV_Sn). Nodule delineation was assessed by two observers (scores 1–5, 1 = unsure, 5 = high confidence).ResultsThe diameter of the 195 detected artificial nodules ranged from 0.9–21.5 mm (mean 7.84 mm ± 5.31). The best ULD scores were achieved using 100kV_Sn and 70 kV ULD protocols (4.14 and 4.06 respectively). Both protocols were not significantly different (p = 0.244).The mean score of 3.78 in ULD 150kV_Sn was significantly lower compared to the 100kV_Sn ULD protocol (p = 0.008).ConclusionThe results of this experiment, conducted in a realistic setting show the feasibility of ultralow-dose CT for the detection of pulmonary nodules.
Highlights
Lung cancer is the leading cause of cancer deaths in men, and the second leading cause of cancer deaths in women after breast cancer [1, 2]
The analysis conducted within a large multicenter trial (National Lung Screening Trial [3, 4]) showed a 20% reduction in mortality rate of a high risk population undergoing annual lung cancer screening with low dose computed tomography (LDCT)
Due to repetitive CT examinations, patients, who receive an annual LDCT from the age of 50–75 years showed an additional risk of 1.8% for lung cancer development [5]
Summary
Lung cancer is the leading cause of cancer deaths in men, and the second leading cause of cancer deaths in women after breast cancer [1, 2]. The analysis conducted within a large multicenter trial (National Lung Screening Trial [3, 4]) showed a 20% reduction in mortality rate of a high risk population undergoing annual lung cancer screening with low dose computed tomography (LDCT). Due to repetitive CT (computed tomography) examinations, patients, who receive an annual LDCT (effective dose of 5.2 mGy or approximately 1 mSv) from the age of 50–75 years showed an additional risk of 1.8% (95% CI 0.5–5.5) for lung cancer development [5]. Various strategies have been developed for lowering the radiation dose of CT without influencing the signal-to-noise-ratio, including lowering the tube voltage and/or the tube current, noise reduction filters, iterative reconstruction selective in-plane shielding or automated exposure control [6,7,8,9,10]
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