High-spatial and high-temporal resolution dynamic contrast-enhanced perfusion imaging of the liver with time-resolved three-dimensional radial MRI.

PURPOSE: Detection, characterization, and monitoring the treatment of hepatocellular carcinomas (HCC) in patients with cirrhosis is challenging because of their variable and rapid arterial enhancement. Multiphase dynamic contrast-enhanced MRI is used clinically for HCC assessment; however, the method suffers from limited temporal resolution and difficulty in coordinating imaging and breath-hold timing within a narrow temporal window of interest. In this article, a volumetric, high-spatial resolution, and high-temporal resolution dynamic contrast-enhanced liver imaging method for improved detection and characterization of HCC is demonstrated. METHODS: A time-resolved three-dimensional radial acquisition with iterative sensitivity-encoding reconstruction images the entire abdomen and thorax with high spatial and temporal resolution, using real-time three-dimensional fluoroscopy to match the breath hold to contrast arrival. The sequence was tested on 17 subjects, including eight patients with HCC or other hypervascular focal lesions. RESULTS: This technique was successful in acquiring volumetric imaging of the entire liver with 2.1-mm isotropic spatial and true 4-s temporal resolution. CONCLUSION: This technique may be suitable for detecting, characterizing, and monitoring the treatment of HCC. It also holds significant potential for perfusion modeling, which may provide a noninvasive means to rapidly determine the efficacy of chemotherapeutic agents in these tumors over the entire liver volume.

Quantitative hepatic perfusion modeling using DCE-MRI with sequential breathholds.

PURPOSE: To develop and demonstrate the feasibility of a new formulation for quantitative perfusion modeling in the liver using interrupted DCE-MRI data acquired during multiple sequential breathholds. MATERIALS AND METHODS: A new mathematical formulation to estimate quantitative perfusion parameters using interrupted data was developed. Using this method, we investigated whether a second degree-of-freedom in the tissue residue function (TRF) improves quality-of-fit criteria when applied to a dual-input single-compartment perfusion model. We subsequently estimated hepatic perfusion parameters using DCE-MRI data from 12 healthy volunteers and 9 cirrhotic patients with a history of hepatocellular carcinoma (HCC); and examined the utility of these estimates in differentiating between healthy liver, cirrhotic liver, and HCC. RESULTS: Quality-of-fit criteria in all groups were improved using a Weibull TRF (2 degrees-of-freedom) versus an exponential TRF (1 degree-of-freedom), indicating nearer concordance of source DCE-MRI data with the Weibull model. Using the Weibull TRF, arterial fraction was greater in cirrhotic versus normal liver (39 ± 23% versus 15 ± 14%, P = 0.07). Mean transit time (20.6 ± 4.1 s versus 9.8 ± 3.5 s, P = 0.01) and arterial fraction (39 ± 23% versus 73 ± 14%, P = 0.04) were both significantly different between cirrhotic liver and HCC, while differences in total perfusion approached significance. CONCLUSION: This work demonstrates the feasibility of estimating hepatic perfusion parameters using interrupted data acquired during sequential breathholds.

Non-contrast enhanced 3D SSFP MRA of the renal allograft vasculature: a comparison between radial linear combination and Cartesian inflow-weighted acquisitions.

Renal transplant patients often require imaging to ensure appropriate graft placement, to assess integrity of transplant vessel anastomosis and to evaluate for stenosis that can be a cause of graft failure. Because there is risk for nephrogenic systemic fibrosis in the setting of renal insufficiency, the use of non-contrast MRA in these patients is helpful. In this study, the ability of two non-contrast MRA methods - 3D radial linear combination balanced SSFP (VIPR-SSFP) and inflow-weighted Cartesian SSFP (IFIR) - to visualize the transplant renal vessels is compared. Twenty-one renal transplant patients were scanned using the VIPR-SSFP and IFIR sequences. Diagnostic efficacy of the sequences was scored using a four point Likert scale according to the following criteria: overall image quality, fat suppression, and arterial/venous visualization quality. Average scores for each criterion were compared using the Wilcoxon signed-rank test. In addition to significantly improved venous visualization, the VIPR-SSFP sequence provided significantly improved fat suppression quality (p<0.03) compared to IFIR. VIPR-SSFP also identified several pathologies such as renal arterial pseudoaneurysm that were not visible on the IFIR images. However, IFIR afforded superior quality of arterial visualization (p<0.005). These two methods of non-contrast MR imaging each have significant strengths and are complementary to each other in evaluating the vasculature of renal allografts.