Metastatic liver tumor: circumferential versus wedge-shaped perilesional enhancement and quantitative image and pathologic correlation

Hepatic tumor response evaluation by MRI

Noninvasive evaluation of hepatic tumor response is necessary to improve the survival rate and quality of life of cancer patients. Among radiologic imaging modalities, MRI plays a significant role in the management of patients with hepatic tumor and is crucial for diagnosis, treatment planning and assessment of response or recurrence, because of its high contrast resolution, lack of ionizing radiation and the possibility of performing functional imaging sequences. This review provides an overview of the MRI findings after various treatments in patients with primary and secondary focal liver malignancies. The imaging methods described focus on the recent trends of using MRI techniques as biomarkers for disease. We also describe the appearance of successful and incomplete response for the various forms of treatment, including transcatheter arterial chemoembolization, ablative therapy, systemic chemotherapy and radiation therapy. Dynamic contrast-enhanced MRI is regarded as an established noninvasive method and potential biomarker for tumor detection, as well as for the characterization of the tumor response. Diffusion-weighted MRI, perfusion-weighted MRI and MRS are also promising functional biomarkers to help select patients for various therapies and to assess the response to treatments. However, further validation and standardization should be performed before their widespread use as imaging biomarkers.

Dynamic evolutionary changes in blood flow measured by MDCT in a hepatic VX2 tumor implant over an extended 28-day growth period: time-density curve analysis

RATIONALE AND OBJECTIVES

The enhancement pattern of malignant tumors has been studied in short-term animal models (7-14 days), but the reported results have been variable and inconsistent. The purpose of this study was to investigate the changing blood flow characteristics of VX2 tumors implanted in rabbit livers with contrast-enhanced multidetector computed tomography (MDCT) to establish a predictable pattern of vascular evolution over an extended 28-day growth period.

MATERIALS AND METHODS

VX2 carcinoma was implanted in livers of 10 male New Zealand White rabbits. Dynamic CT (2/seconds x 60 seconds) was conducted on days 7, 14, 21, and 28 after tumor implantation. Enhancement parameters of time-density curve (TDC), time to start (T0), time to peak (TP), maximum enhancement (DeltaH), slope of enhancement (SLe), and washout (SLw) in tumor center, tumor rim, and normal liver were analyzed. Tumor samples corresponding to CT images of one tumor on days 14 and 21 and seven tumors on day 28 were stained with hematoxylin and eosin and anti-CD31 monoclonal antibody. The relationship between enhancement parameters and histology parameters (thickness of tumor border, extent of blood stasis, and luminar vessel density) was analyzed.

RESULTS

Consistent growth, appearance, and vascular changes occurred in 7 of 10 animals over the 4-week observation period. Peripheral rim-like enhancement was noted in CT images. TDC analysis showed that tumor rim enhancement was pronounced and more rapid than normal liver initially but this difference diminished with tumor progression. The SLe, SLw, and DeltaH decreased from 10.03 +/- 3.25 Hu/second, 0.42 +/- 0.25 Hu/sec, and 58.00 +/- 25.27 Hu on day 7 to 5.86 +/- 2.73 Hu/second, 0.10 +/- 0.13 Hu/second, and 37.78 +/- 8.89 Hu/second on day 28, respectively. TP increased from 12.71 +/- 4.85 seconds on day 7 to 25.57 +/- 7.75 seconds on day 28. No significant changes were noted on the TDC parameters in normal liver. The maximum density difference between tumor rim and normal liver (D(rim-liver)) appeared 10.5 +/- 2.1 seconds after contrast injection. The maximum D(rim-liver) decreased from 54.33 +/- 37.86 Hu on day 7 to 11.16 +/- 13.03 Hu on day 28. On histological analysis, viable tumor cells were found in tumor rim with few luminar vessels. The tumor border showed desmoplastic reaction, vascular dilation and proliferation, inflammatory cell infiltration, and blood stasis. These findings were more obvious on day 28 than those on day 14. TP showed significant positive correlations with the extent of blood stasis in tumor border and adjacent liver and the maximum thickness of the tumor border (r = 0.945 and 0.893 respectively, P < .05).

CONCLUSION

The rabbit VX2 liver tumor is a hypovascular tumor with perilesional enhancement over its lifespan as imaged by MDCT. Consistent changes in the measured vascular parameters correlated with the size/age of the tumor implants. These findings suggest that the accuracy of CT enhancement imaging for VX2 liver tumor detection might be decreased with tumor development.

Pre-, peri-, and posttreatment imaging of liver lesions

This article provides an overview of current treatment approaches in patients with primary or secondary liver diseases. Emphasis is placed on MR imaging prior, during, and after various treatments, including liver resection, systemic chemotherapy, transcatheter arterial chemoembolization, ablative therapies, and liver transplantation. Findings described for MR imaging are directly applicable to findings for CT and potentially contrast-enhanced ultrasound. The authors' description, however, will deal mainly with MR imaging as this is the their preferred approach due to diagnostic accuracy and patient safety, and the findings are most demonstrative on MR imaging.

Magnetic resonance imaging features of focal liver lesions after intervention

The aim of this article is to provide an overview of MRI features of primary and secondary liver lesions after intervention. Emphasis is given to T2- and T1-weighted pre and post intravenous gadolinium chelates appearance of successfully treated lesions and, from residual/recurrent tumors after therapy. In addition, complications after procedures are briefly cited. Liver resection, radiation therapy, systemic chemotherapy, transcatheter arterial chemoembolization, ablative therapies and liver transplantation are the methods discussed in this review. Among these methods, special attention is given to MRI findings after ablative therapies since radiofrequency ablation is commonly performed in our institution.

Liver metastases from unknown primary site: demonstration on MR images

To demonstrate the MR imaging features of liver metastases in patients with the clinical and histologic diagnosis of tumors of unknown primary tumors, a retrospective 7-year study was performed that included a total of 14 consecutive patients (7 men and 7 women; age range, 39-82 years; mean age, 60.6 years) with liver metastases from unknown primary site who had undergone MR imaging. The following lesion features were evaluated: a) number, b) diameter, c) signal intensity on T1 and T(2)-weighted images, and d) pattern of enhancement on immediate, 45 s and 90 s post gadolinium images. Lesions were classified as hypovascular, hypervascular and nearly isovascular relative to liver parenchyma as shown on immediate post gadolinium images. Patients were separated into four major groups, related to the histologic diagnosis of the lesions: (I) poorly differentiated neoplasms; (II) well-differentiated and moderately differentiated adenocarcinoma; (III) squamous cell carcinoma; (IV) combined poorly differentiated carcinoma and poorly differentiated adenocarcinoma. MRI findings were correlated with histologic information obtained by chart review and confirmed by retrospective histopathology review. All patients had the histologic diagnosis of adenocarcinoma: 8 patients belonged to group II (1 patient with the subtype well-differentiated and 7 patients with the subtype moderately differentiated) and 6 patients to group IV. Eleven patients (79%) presented with multiple lesions distributed throughout both hepatic lobes; 3 patients exhibited solitary lesions. All solitary metastases possessed a diameter equal or larger than 5 cm. Patients with multiple metastases demonstrated a wide range of diameter, ranging from less than 1.5 cm to more than 5 cm. Regarding lesion vascularity, 4 of 13 of the patients had hypovascular metastases and 9 of 13 of the patients had hypervascular lesions. One patient demonstrated both types of lesions. Five of six patients with the histopathologic diagnosis of poorly differentiated adenocarcinoma demonstrated hypervascular metastases. Solitary metastases were most often hypovascular (2 of 3); however no correlation with the histologic subtype was possible. Liver metastases from unknown primary site are often multiple and often hypervascular. Poorly differentiated tumors are the most common histologic type. Metastases are not uncommonly hypovascular, and these are often solitary.

MR imaging of hepatic metastases

MR imaging is an excellent diagnostic tool for the detection and characterization of liver metastases. The most characteristic finding is peripheral ring enhancement on immediate postgadolinium images.

Magnetic resonance imaging. Liver-specific contrast agents

MR imaging with new liver-specific contrast agents will probably be the imaging modality used in the future to detect focal liver lesions. The detection of HCC will probably be improved by using specific hepatobiliary agents, but the exact technique remains to be determined. New liver-specific contrast can differentiate some benign lesions from malignant ones and can assist in making a final diagnosis. In certain circumstances, liver-specific contrast agents can be used to evaluate hepatic vessels, the biliary tract, and hepatic function. New applications are also expected.