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The MRI-based formula has great potential for detecting portal hypertension. As a non-invasive measurement, it may be clinically accepted for the replacement of invasive modalities after further refinement.

AIM:To explore the diffusion gradient b-factor that optimizes both apparent diffusion coefficient (ADC) measurement and contrast-to-noise (CNR) fo r a s s e s s i n g t u m o r re s p o n s e t o t ra n s a r t e r i a l chemoembolization (TACE) in a rabbit model. METHODS: Twelve New Zealand white rabbits bearing VX2 tumors in the liver were treated with TACE. Diffusion-weighted imaging (DWI) with various b values was performed using the same protocol before and 3 d after treatment with TACE. ADC values and CNR of each tumor pre-and post-treatment with different b factors were analyzed. Correlation between ADC values and extent of necrosis in histological specimens was analyzed by a Pearson's correlation test. RESULTS:The quality of diffusion-weighted images diminished as the b value increased. A substantial decrease in the mean lesion-to-liver CNR was observed on both pre-and post-treatment DW images, the largest difference in CNR pre-and post-treatment was manifested at a b value of 1000 s/mm 2 (P = 0.036 ). The effect of therapy on diffusion early after treatment was shown by a significant increase in ADCs (P = 0.007), especially with large b factors (≥ 600 s/mm 2

Abstract. Targeted delivery is a highly desirable strategy for diagnostic imaging due to enhanced efficacy and reduced dosage/toxicity. The need to develop target-specific magnetic resonance imaging (MRI) contrast agents to aid in disease characterization is highly essential. In this study, a specific contrast agent, Gd-DTPA-poly-L-lysine (PL-Gd-DTPA)-folate, was synthesized and evaluated for its efficacy as a targeted agent for the imaging of tumors that overexpress the folate receptor. Folic acid was conjugated to PL-Gd-DTPA via the ε-amino groups. The receptor binding properties of folate-PL-Gd-DTPA were studied in cultured tumor cells that overexpressed the folate receptor. The tumor-selecting properties of folate-PL-Gd-DTPA were then evaluated in BALB/c mice bearing subcutaneously implanted folate receptor-positive tumors. Tissue MR signal intensities were measured at six different time-points. In the in vitro study, the folate-PL-Gd-DTPA was able to bind to these cells, which overexpressed the folate receptor, as with free folic acid. Excellent tumor selectivity was also shown in the animal model; after the success of injection of folate-PL-Gd-DTPA, a maximum intensity increase of 125.4% was observed from pre-injection compared to post-injection images of the tumor at the 48 h time-point. The liver enhancement was non-specific and the muscle signal intensity at any time-point after injection showed no statistical difference with that observed before injection. Folate-PL-Gd-DTPA is a promising, novel receptorspecific MRI contrast agent with potential applications in the imaging of human folate receptor-positive tumors.