Repeatability and optimal b value in diffusion weighted imaging of non-small-cell lung cancer: a preliminary study

Abstract

Objective To examine the non-small-cell lung cancer (NSCLC) lesions with diffusion weighted imaging (DWI) with different diffusion sensitivity coefficients (b values) , determine on the optimal b value, and to evaluate the repeatability of different b value scans. Methods Thirty-two patients with NSCLC underwent DWI of chest using a single shot echo-planar imaging sequence (EPI-SE) with different b values (500 s/mm2, 700 s/mm2, 900 s/mm2) . Each b-value was scanned twice. The apparent diffusion coefficient (ADC) values of lung cancer lesions were measured. The DWI image and ADC image quality in each group were analyzed. The effects of different b values on imaging and ADC value were compared to explore the stability and repeatability of DWI. Results As the b values increased from 500 s/mm2 to 900 s/mm2, the signal noise ratio (SNR) and contrast noise ratio (CNR) of the lesions decreased gradually, and the ADC values decreased gradually. There was no statistically significant difference in SNR and CNR between b values of 500 s/mm2 and 700 s/mm2. When the b value was 700 s/mm2, the ADC value showed higher stability, less fluctuation range, less difference of ADC mean values between the two scans, and good scanning repeatability. Conclusion When b value is 700 s/mm2, the SNR and CNR of the lung cancer DWI images are high, and the stability and repeatability of the ADC values are good, which may provide more accurate information about the lesions. Key words: Carcinoma, non-small-cell lung; Magnetic resonance imaging; Diffusion weighted imaging