Magnetic resonance imaging (MRI) has evolved into a robust, comprehensive modality for evaluating both structural and functional characteristics of the liver in diffuse and focal hepatic diseases. Advances in coil technology, gradient performance, motion-compensated acquisition techniques, and optimized pulse sequences have significantly enhanced image quality and lesion detectability on hepatic MRI.

Diffusion-weighted imaging (DWI) has become an important adjunct in body MRI. By exploiting differences in the diffusivity of water molecules within tissues, DWI provides contrast information that reflects tissue cellularity and microstructural integrity. The derived apparent diffusion coefficient (ADC) value offers a quantitative parameter that complements morphological assessment.

Although DWI was originally established in neuroimaging, its use in the liver has expanded rapidly. Current evidence suggests that DWI is valuable for lesion detection, differentiation between benign and malignant focal liver lesions, disease staging, treatment response assessment, and post-therapy surveillance.

However, overlap between ADC values of some benign and malignant lesions necessitates interpretation in conjunction with conventional MRI sequences. At the same time, diffusion-weighted MRI offers important advantages over contrast-enhanced modalities, especially by avoiding radiation exposure and iodinated or gadolinium-based contrast administration.

The present study was undertaken to:

1. Evaluate the role of non-contrast MRI with DWI in detecting and characterizing focal liver lesions.
2. Assess the diagnostic performance of ADC values in differentiating benign and malignant lesions.
3. Propose a clinically useful ADC cut-off value and compare findings with prior published studies.

Study Design and Setting

This prospective observational study was conducted in the Departments of Radiodiagnosis at Gandhi Medical College and Hamidia Hospital, Bhopal, M.P. India. Seventy patients with suspected focal liver lesions were evaluated between October 2023 to September 2024.

Patient selection

Inclusion Criteria

• Patients with strong clinical suspicion of focal liver lesions.
• Patients with focal lesions detected on ultrasonography.
• Patients with equivocal findings on contrast-enhanced CT.

Exclusion Criteria

• Lesions extending into the liver from adjacent organs.
• Traumatic liver injury.
• Patients unable to perform breath-hold.
• Contraindications to MRI (pacemakers, cochlear implants, metallic implants).

Instrumentation

MRI examinations were carried out on a 1.5-Tesla system with a high-field superconducting cylindrical magnet. Liver imaging was performed using a dedicated 8-channel, high-resolution QD body array coil.

Study Protocol

For each subject, clinical history, presenting complaints, physical examination findings, biochemical parameters, and baseline imaging (chest radiography and abdominal ultrasonography) were recorded in a structured proforma. Before MRI acquisition, all participants were screened for contraindications and ensured to be free of metallic objects.

Patients were positioned supine on the gantry table with both arms elevated above the head. Breath-holding instructions were explained prior to image acquisition. Subjects were asked to suspend respiration on command and resume breathing when reinstructed. In patients unable to sustain breath-holding due to dyspnoea, shallow breathing was permitted.

Pulse Sequences and Image Analysis

Diffusion-weighted datasets were processed using an automated workstation application to generate voxel-based apparent diffusion coefficient (ADC) maps. Quantitative ADC measurements were obtained by manually placing regions of interest (ROIs) on the ADC maps.

All MRI scans were reviewed and findings were documented in the study proforma. The liver was evaluated on T1-weighted, T2-weighted, and diffusion-weighted sequences, and ADC values were derived from the corresponding maps. In cases with multiple focal lesions, the largest or most representative lesion was analyzed. When morphologically different lesions were present in the same patient, one representative lesion from each category was included.

Lesion Evaluation Criteria

For each focal liver lesion, the following parameters were assessed:

• Number of lesions
• Hepatic segmental location
• Size and morphological configuration
• Presence of septations or internal nodularity
• Wall thickness and margin sharpness
• Signal homogeneity or heterogeneity
• Appearance on DWI and corresponding ADC maps
• Mean ADC value obtained using circular ROIs ≥10 mm in diameter (mm²/sec)
• Additional characteristic imaging features

Follow-Up and Final Diagnosis

Follow-up evaluation was performed using one or more of the following: biopsy, aspiration cytology, surgical correlation, serial ultrasonography to assess lesion stability, or supplementary investigations such as contrast-enhanced CT or nuclear scintigraphy. Final diagnoses were established using combined clinical, imaging, and pathological information. These outcomes were correlated with DWI characteristics and mean ADC values and were subsequently tabulated for analysis.

Statistical Analysis

Data were analyzed using SPSS v22. Sensitivity, specificity, PPV, NPV, and accuracy were calculated. Mean ADC values were compared using appropriate statistical tests. A p-value < 0.05 was considered significant.

Diffusion-weighted imaging (DWI) plays an emerging role for the assessment of focal and diffuse liver diseases. This growing interest is due to that fact that DWI is a non IIIIIIIIIIcontrast technique with inherent high contrast resolution, with promising results for detection and characterization of focal liver lesions. Recent advances in diffusion image quality have also added interest to this technique in the abdomen.

The liver was viewed in T1W, T2W and DWI sequences with calculation of ADC values using the ADC maps and any abnormality was identified. When multiple lesions are noted the most representative lesion or the largest of the lesions was taken into consideration. When different types of lesions were identified in the same person representative lesions of each type was considered. The following characteristics of the lesions were noted. A cut off ADC value of 1.4 x 10-3 mm2/s is considered for differentiating benign from malignant lesions.

Focal liver lesions (FLL’s) are encountered on a daily basis in general radiology practice. Usually lesions can be accurately characterised on unenhanced ultrasound. If not, many patients proceed to computed tomography (CT) or magnetic resonance imaging (MRI) with the main aim to determine benign from malignant conditions. Focal liver lesions are usually detected incidentally during abdominal ultrasound. The injection of microbubble ultrasound contrast agents improves the characterization of focal liver lesions that are indeterminate on conventional ultrasound. The use of CEUS is recommended in official guidelines and suggested as a second diagnostic step after ultrasound detection of indeterminate focal liver lesions to immediately establish the diagnosis, especially for benign liver lesions, such as hemangiomas, avoiding further and more expensive examinations.^[1]

Fawkes A et al studied contrast enhanced ultrasound v’s contrast enhanced MRI/CT in the characterisation of focal liver lesions using an evidence based approach. CEUS involves the use of microbubble contrast agents (e.g SonoVue) and specialized imaging. Evidence suggests CEUS has a high sensitivity and specificity in the characterisation of focal liver lesions. Provides accurate diagnostic information comparable to CECT and CEMRI.

The purpose of this study by Semelka RC et al was to compare dual-phase spiral computed tomography (CT) and magnetic resonance imaging (MRI) using dynamic gadolinium enhancement for liver lesion detection and characterization. Patients underwent dual-phase spiral CT and MRI for the evaluation of focal liver disease within a 1-month period. Spiral CT and MR images were interpreted prospectively, in a blinded fashion by separate, individual, experienced investigators, to determine lesion detection and characterization. More lesions were characterized on MR images in 41% patients. In patients with a discrepancy between MR and CT findings, the MR images added information considered significant to patient management in all cases. MRI was moderately superior to dual-phase spiral CT for lesion detection, and was markedly superior for lesion characterization, with these differences having clinical significance.

Various authors have elaborated the role of magnetic resonance diffusion imaging in differentiation of malignant and benign hepatic focal lesions. Li J et al studied clinical study of diffusion-weighted imaging in the diagnosis of liver focal lesion. Their aim was to determine whether the DW-MRI can be used for qualitative and quantitative liver cancer analysis, where an automated method will be proposed for improving the accuracy of liver segmentation in DW-MRI to increase the ability of diagnosis of disease. Their result from the liver DW-MRI image is quantitatively and qualitatively analyzed. Experimental results show that DW-MRI has a great advantage in the diagnosis, the DWI images of benign lesion group was lower than that of malignant lesion, thus DW-MRI is segmented by graph-cut algorithm can provide important additional information regarding differential diagnosis of specific liver cancer to some extent.

Koike N et al did similar study on the role of diffusion-weighted magnetic resonance imaging in the differential diagnosis of focal hepatic lesions. Visualization of lesions, relative contrast ratio (RCR), and apparent diffusion coefficient (ADC) were compared between benign and malignant lesions on DWI. Superparamagnetic iron oxide (SPIO) was administered to 59 patients, and RCR was compared pre- and post-administration. RCR between malignant lesions and surrounding hepatic tissues significantly improved after SPIO administration, but RCRs in benign lesions were not improved. It was concluded that DWI is a simple and sensitive method for screening focal hepatic lesions and is useful for differential diagnosis.

Chiu FY et al assessed whether administration of gadolinium-based contrast material significantly affects DWI and ADC values at the focal hepatic lesions. The statistical significance of differences between precontrast and postcontrast administration was determined by use of a paired t test. They concluded that there was no significant difference before and after administration of contrast agent in the SNR or CNR of DWI. This indicates the feasibility of postcontrast DWI as a substitute for an unsuccessful precontrast-enhanced study in clinical practice.

Jeon SK et al also investigated added value of MRI to preoperative staging MDCT for evaluation of focal liver lesions (FLLs) in potentially resectable pancreatic ductal adenocarcinomas (PDACs).Size of hepatic lesions was measured and detection rate of hepatic metastasis unsuspected by MDCT and diagnostic yield of MRI for FLLs were assessed. In potentially resectable PDACs, addition of MRI with DWI can provide significantly better diagnostic performance in characterization of focal liver lesions, especially for small-sized (≤ 1 cm) MDCT-indeterminate or suspicious metastasis lesions, aiding in determination of appropriate operation candidates.

The purpose of this review by Galea N et al is to describe the current clinical roles of DWI for the detection and characterization of focal liver lesions, and to review pitfalls, limitations, and future directions of DWI for assessment of focal liver disease. Whereas Sandrasegaran K et determined if focal liver masses could be differentiated as benign or malignant on the basis of diffusion-weighted imaging (DWI). DWI was performed with b values of 0, 50, and 400 s/mm2. Of 104, 76 patients had lesions larger than 2 cm diameter, radiologic or pathologic characterization of the lesion, and diagnostic quality DWI. The apparent diffusion coefficient (ADC) of the largest liver lesion was measured. The liver masses were diagnosed on histology or had characteristic computed tomography/MRI findings and follow up of more than 6 months. The ADC of cysts and hemangiomas were significantly higher than that of other lesions (P = .0003, t-test). There was no significant difference between ADC values of solid, benign liver lesions (FNH, adenoma) and malignant lesions (HCC, metastases) (P =.62). To conclude, solid liver lesions have a lower ADC than cysts and hemangiomas. However, there is no significant difference in ADC between solid benign and malignant lesions. DWI appears to have only minimal additional value over currently used MRI sequences in characterizing liver masses

Parikh T et al retrospectively compare diffusion-weighted (DW) magnetic resonance (MR) imaging with standard breath-hold T2-weighted MR imaging for focal liver lesion (FLL) detection and characterization, by using consensus evaluation and other findings as the reference standard. Reference standard for diagnosis was obtained from consensus review by the two observers of DW, T2-weighted, and dynamic contrast material–enhanced images, pathologic data, and follow-up imaging results. Apparent diffusion coefficient (ADC) was measured for FLLs identified at consensus review.They concluded that DW MR imaging was better than standard breath-hold T2-weighted imaging for FLL detection and was equal to breath-hold T2-weighted imaging for FLL characterization.

Thus, the sensitivity of non-contrast MRI with DWI and ADC values was very high and more than both USG and contrast enhanced Multiphasic CT. The specificity of MRI was comparable to that of CE- Multiphasic CT in diagnosing malignant focal liver lesions. A cut off ADC value of 1.4 x 10-3 mm2/s was found to be a superior, noninvasive tool for differentiating malignant from benign lesions without the risk of radiation, contrast media and invasiveness. Hence, MRI with DWI in particular is a very valuable noninvasive tool for the identification and characterization of focal liver lesions.

Consent

Written consent was obtained from the relatives of patients after explaining them the nature and purpose of the study. They were assured that confidentiality would be strictly maintained. The option to withdraw from the study was always open.

1. Lencioni R, Cioni D, Bartolozzi C. Focal liver lesions. Detection, characterization, ablation/R. Lencioni, D. Cioni, C. Bartolozzi.–2005.–284 p. 2005.
2. Marrero JA, Ahn J, Reddy RK, Practice Parameters Committee of the American College of Gastroenterology. ACG clinical guideline: the diagnosis and management of focal liver lesions. Official journal of the American College of Gastroenterology| ACG. 2014 Sep 1;109(9):1328-47.
3. D'Onofrio M, Crosara S, De Robertis R, Canestrini S, Mucelli RP. Contrast-enhanced ultrasound of focal liver lesions. American journal of roentgenology. 2015 Jul;205(1):W56-66.
4. Fawkes A, Malone DE. Contrast enhanced ultrasound V’s contrast enhanced MRI/CT in the characterisation of focal liver lesions using an evidence based approach. European Congress of Radiology-ECR 2015.
5. van Leeuwen MS, Noordzij J, Feldberg MA, Hennipman AH, Doornewaard H. Focal liver lesions: characterization with triphasic spiral CT. Radiology. 1996 Nov;201(2):327-36.
6. Matos AP, Velloni F, Ramalho M, AlObaidy M, Rajapaksha A, Semelka RC. Focal liver lesions: Practical magnetic resonance imaging approach. World journal of hepatology. 2015 Aug 8;7(16):1987.
7. Semelka RC, Martin DR, Balci C, Lance T. Focal liver lesions: comparison of dual‐phase CT and multisequence multiplanar MR imaging including dynamic gadolinium enhancement. Journal of Magnetic Resonance Imaging: An Official Journal of the International Society for Magnetic Resonance in Medicine. 2001 Mar;13(3):397-401.
8. Kumaraswamy S, Kaur A, Kaur N, Walia HM, Bains R, Abraham J. Role of Magnetic Resonance Diffusion Imaging in Differentiation of Malignant and Benign Hepatic Focal Lesions.
9. Li J, Yang Y. Clinical study of diffusion-weighted imaging in the diagnosis of liver focal lesion. Journal of Medical Systems. 2019 Mar;43(3):1-7.
10. Koike N, Cho A, Nasu K, Seto K, Nagaya S, Ohshima Y, Ohkohchi N. Role of diffusion-weighted magnetic resonance imaging in the differential diagnosis of focal hepatic lesions. World journal of gastroenterology: WJG. 2009 Dec 12;15(46):5805.
11. Chiu FY, Jao JC, Chen CY, Liu GC, Jaw TS, Chiou YY, Hsu FO, Hsu JS. Effect of intravenous gadolinium-DTPA on diffusion-weighted magnetic resonance images for evaluation of focal hepatic lesions. Journal of computer assisted tomography. 2005 Mar 1;29(2):176-80.
12. Jeon SK, Lee JM, Joo I, Lee DH, Ahn SJ, Woo H, Lee MS, Jang JY, Han JK. Magnetic resonance with diffusion-weighted imaging improves assessment of focal liver lesions in patients with potentially resectable pancreatic cancer on CT. European radiology. 2018 Aug;28(8):3484-93.
13. Galea N, Cantisani V, Taouli B. Liver lesion detection and characterization: role of diffusion‐weighted imaging. Journal of magnetic resonance imaging. 2013 Jun;37(6):1260-76.
14. Sandrasegaran K, Akisik FM, Lin C, Tahir B, Rajan J, Aisen AM. The value of diffusion-weighted imaging in characterizing focal liver masses. Academic radiology. 2009 Oct 1;16(10):1208-14.
15. Parikh T, Drew SJ, Lee VS, Wong S, Hecht EM, Babb JS, Taouli B. Focal liver lesion detection and characterization with diffusion-weighted MR imaging: comparison with standard breath-hold T2-weighted imaging. Radiology. 2008 Mar;246(3):812-22.