The role of diffusion-weighted imaging and appparent diffusion coefficint values for determining biopsy region in lung masses

Objective: The purpose of this study was to use magnetic resonance imaging (MRI) and diffusion-weighted imaging (DWI) along with computed tomography (CT) -guided transthorasic biopsy in lung nodules or masses. We aimed to detect the biopsy area with higher tumoral cell density in case of a single lesion; and the lesion with higher malignancy potential in case of multiple lesions. We hereby sought to assess whether using DWI and apparent diffusion coefficient (ADC) map is useful as a guide to CT-guided biopsy procedure. Material and Methods: From March 2103 to October 2014, 100 out of 116 consecutive patients who were referred to Department of Interventional Radiology, Abant Izzet Baysal University for transthorasic biopsy with a suspicion of lung malignancy underwent MRI (T1W,T2W,STIR) and DWI (b=50, b=400, b=800) examinations. For each patient, we formed an ADC map using b=800 images. Before the biopsy procedure, we assessed the MRI and DWI properties of the lesion(s) and biopsy was performed visually according to ADC map, from the most hypointense region of a single lesion or most hypointense lesion of a lesion group. The evaluation of DWI/ADC signal properties and ADC measurement of the lesions were performed retrospectively because they had no practical value before the biopsy procedure. Results: Seventy-two out of 100 patients, who were evaluated with MRI and DWI/ADC, were eligible for inclusion. These patients had 74 lesions of which all were diagnosed histopathologically (100% diagnosis). In this study, the benign lesions tended to be more homogenous whereas the malignant ones appeared to be more heterogenous in MRI and ADC images (p=0.011). In ADC map, the malignant lesions were more hypointense (p=0.001) and showed more diffusion restriction (p=0.002) when compared with the benign ones. However, there was not a statistically significant difference between malignant and benign groups in respect to ADC values (p=0.147). Conclusion: ADC map images might be used in selected patients as a new guide before CT-guided transthorasic biopsy. Determining the hypointense areas in ADC map as biopsy targets may decrease the need for measuring ADC which is time consuming and doubtful in routine daily practise. Keywords: Diffusion magnetic resonance imaging, image-guided biopsy, lung cancer.