Role of diffusion-weighted magnetic resonance imaging in the differential diagnosis of focal hepatic lesions

Abstract

Aim: To evaluate the utility of diffusion-weighted imaging (DWI) in screening and differential diagnosis of benign and malignant focal hepatic lesions.

Methods: Magnetic resonance imaging (MRI) examinations were performed using the Signa Excite Xl Twin Speed 1.5T system (GE Healthcare, Milwaukee, WI, USA). Seventy patients who had undergone MRI of the liver [29 hepatocellular carcinomas (HCC), four cholangiocarcinomas, 34 metastatic liver cancers, 10 hemangiomas, and eight cysts] between April 2004 and August 2008 were retrospectively evaluated. 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.

Results: DWI showed higher contrast between malignant lesions (especially in multiple small metastatic cancers) and surrounding liver parenchyma than did contrast-enhanced computed tomography. ADCs (mean +/- SD x 10(-3) mm(2)/s) were significantly lower (P < 0.05) in malignant lesions (HCC: 1.31 +/- 0.28 and liver metastasis: 1.11 +/- 0.22) and were significantly higher in benign lesions (hemangioma: 1.84 +/- 0.37 and cyst: 2.61 +/- 0.45) than in the surrounding hepatic tissues. RCR between malignant lesions and surrounding hepatic tissues significantly improved after SPIO administration, but RCRs in benign lesions were not improved.

Conclusion: DWI is a simple and sensitive method for screening focal hepatic lesions and is useful for differential diagnosis.

Figure 1

A case of hepatic metastases of colon cancer. A, B: Dynamic computed tomography of the liver in the portal phase showing multiple metastatic lesions, which are indicated as low-density masses (arrows); C, D: Diffusion-weighted imaging (DWI) of the same locations as in (A) and (B), clearly showing metastatic lesions as high signal intensities; E, F: After SPIO administration, the background signal intensity of the liver parenchyma was reduced and the signal intensities of the metastatic lesions were seen more clearly.

Figure 2

Relative contrast ratio (RCR) of focal hepatic lesions visualized by diffusion-weighted imaging (DWI) before and after the administration of superparamagnetic iron oxide (SPIO). Meta: Metastatic liver cancer; HCC: Hepatocellular carcinoma; hemangi: Hepatic hemangioma. ^aP < 0.05, ^bP < 0.01.

Figure 3

A case of hepatic hemangioma. A: Dynamic computed tomography in the portal phase showing a low-density mass with a marginal stain at the S7 lobe (arrow). This is a typical staining pattern for hemangiomas; B: The hemangioma (arrow) expressed high signal intensity on diffusion-weighted imaging; C: The intensity of this signal was reduced after administration of superparamagnetic iron oxide (arrow); D: The hemangioma showed a high apparent diffusion coefficient (ADC) value on the ADC map (arrow).

Figure 4

A case of multiple hepatic metastases of colon cancer with multiple hepatic cysts. A, B: T2-weighted magnetic resonance imaging showing high signal intensities on both metastatic lesions (arrows) and cysts (arrow heads); C, D: Diffusion-weighted imaging after administration of superparamagnetic iron oxide showing high signal intensities on metastatic lesions only (arrows).

Figure 5

Comparison of apparent diffusion coefficient (ADC) between focal hepatic lesions and surrounding hepatic parenchyma. Meta: Metastatic liver cancer; HCC: Hepatocellular carcinoma; CC: Cholangiocarcinoma; Hemangi: Hepatic hemangioma. ^bP < 0.01.

Figure 6

A case of hepatic cysts. A: Dynamic computed tomography in the portal phase showing the hepatic cyst as a low-density lesion (arrow); B: The lesion expressed no signal intensity on diffusion-weighted imaging; C: The lesion showed a high apparent diffusion coefficient (ADC) on the ADC map (arrow).