A Prospective Observational Study of Diagnostic Reliability of Semiquantitative and Quantitative High b-Value Diffusion-Weighted MRI in Distinguishing between Benign and Malignant Lung Lesions at 3 Tesla

Abstract

Aim The aim of this study was to evaluate the usefulness of high b-value diffusion-weighted imaging (DWI) to differentiate benign and malignant lung lesions in 3 Tesla magnetic resonance imaging (MRI). Materials and Methods Thirty-one patients with lung lesions underwent a high b-value (b= 1000 s/mm ² ) DW MRI in 3 Tesla. Thirty lesions were biopsied, followed by histopathological analysis, and one was serially followed up for 2 years. Statistical analysis was done to calculate the sensitivity, specificity, and accuracy of different DWI parameters in distinguishing benign and malignant lesions. Receiver operating characteristic (ROC) curves were used to determine the cutoff values of different parameters. Results The qualitative assessment of signal intensity on DWI based on a 5-point rank scale had a mean score of 2.71 ± 0.75 for benign and 3. 75 ± 0.60 for malignant lesions. With a cutoff of 3.5, the sensitivity, specificity, and accuracy were 75, 86, and 77.6%, respectively. The mean ADC _min (minimum apparent diffusion coefficient) value of benign and malignant lesions was 1. 49 ± 0.38 × 10-3 mm ² /s and 1.11 ± 0.20 ×10-3 mm ² /s, respectively. ROC curve analysis showed a cutoff value of 1.03 × 10-3 mm ² /s; the sensitivity, specificity, and accuracy were 87.5, 71.4, and 83.3%, respectively. For lesion to spinal cord ratio and lesion to spinal cord ADC ratio with a cutoff value of 1.08 and 1.38, the sensitivity, specificity, and accuracy were 83.3 and 87.5%, 71.4 and 71.4%, and 80.6 and 83.8%, respectively. The exponential ADC showed a low accuracy rate. Conclusion The semiquantitative and quantitative parameters of high b-value DW 3 Tesla MRI can differentiate benign from malignant lesions with high accuracy and make it a reliable nonionizing modality for characterizing lung lesions.

Keywords: diffusion-weighted imaging; lung neoplasm; magnetic resonance imaging.

Fig. 1

The magnetic resonance imaging of a 51-year-old male patient who presented with a cough showing a single T2 hyperintense lesion ( A ) with an irregular margin located in the apical segment of the right upper lobe. The lesion showing diffusion restriction with a high lesion to spinal cord ratio value ( B ), lower minimum exponential apparent diffusion coefficient, and low lesion to spinal cord apparent diffusion coefficient ratio values( C ). The measurement of the exponential apparent diffusion coefficient value ( D ) is shown. The histopathological diagnosis of the biopsy specimen was adenocarcinoma.

Fig. 2

The magnetic resonance imaging of a 38-year-old male smoker who presented with cough and weight loss showing a single T2 hyperintense lesion ( A ) with a lobulated margin in the apical segment of the left upper lobe. The lesion showing diffusion restriction with a high lesion to spinal cord ratio value ( B ), lower minimum apparent diffusion coefficient (ADC), and low lesion to spinal cord ADC ratio values ( C ). The measurement of the exponential ADC value ( D ) is shown. Associated features of mediastinal invasion and left pleural effusion are also seen. The histopathological diagnosis was small cell carcinoma.

Fig. 3

The magnetic resonance imaging of a 51-year-old male with a cough not responding to medical treatment showing a solitary T2 hyperintense wedge-shaped lesion ( A ) with a smooth margin and internal cavitation in the right middle lobe. The lesion showing no significant diffusion restriction with a lower lesion to spinal cord ratio ( B ), higher minimum apparent diffusion coefficient (ADC), and higher lesion to spinal cord ADC ratio values ( C ). The measurement of the exponential ADC value ( D ) is shown. The histopathological diagnosis was granuloma, a benign lesion.

Fig. 4

The magnetic resonance imaging of a 65-year-old female with primary gastrointestinal malignancy showing a single peripheral T2 hyperintense ( A ) lesion with a lobulated margin in the right lower lobe. The lesion showing diffusion restriction with a high lesion to spinal cord ratio value ( B ). The exponential apparent diffusion coefficient (ADC) ( C ) map is also depicted. The low minimum ADC, and low lesion to spinal cord ADC ratio values ( D ) are noted. The histopathological diagnosis was a metastasis from a gastrointestinal tract primary.

Fig. 5

Receiver operating characteristic (ROC) curve for 5-point rank scale on diffusion-weighted imaging (DWI) to differentiate benign and malignant lesions showing an area under the curve (AUC) as 0. 842 (95% confidence interval [CI], 0. 666–1.000). The AUC for minimum apparent diffusion coefficient (ADC) is 0.860 (95% CI, 0. 691–1.000). The AUC for lesion to spinal cord ratio (LSR) on DWI to differentiate benign and malignant lesions is 0. 810 (95% CI, 0. 584–1. 000). The AUC for lesion to spinal cord ADC ratio (LSAR) to differentiate benign and malignant lesions is 0. 774 (95% CI, 0. 520–1. 000).