Absolute blood contrast concentration and blood signal saturation on myocardial perfusion MRI: estimation from CT data.

PURPOSE: To determine the optimal contrast injection rate and absolute blood gadolinium concentration for optimal first-pass imaging. MATERIALS AND METHODS: The concentration of contrast medium in left ventricle (LV) was estimated from dynamic computed tomography (CT) by administering iodinated contrast medium of volume (0.2 mL/kg) equivalent to 0.1 mmol/kg of gadolinium injection in 50 subjects. A blood sample study was performed to determine the relationship between blood signal and gadolinium concentration on perfusion MRI. RESULTS: The mean peak gadolinium concentration in LV increased as the injection rate increased from 1 mL/sec (3.7 +/- 1.2 mM), to 4 mL/sec (6.9 +/- 2.7 mM) (P < 0.01). However, no significant improvement was found with an increase in the injection rate from 4 mL/sec to 5 mL/sec (6.8 +/- 1.5 mM, P = 0.86). In a blood sample study the linear relationship between blood signal and gadolinium concentration was maintained in the range of < or =0.67 mM (r = 0.992), which corresponds to a peak blood concentration following a 0.01 mmol/kg gadolinium injection. CONCLUSION: The optimal contrast injection rate for myocardial perfusion magnetic resonance imaging (MRI) appears to be 4 mL/sec. Saturation of arterial input signal is inevitable if the dose of gadolinium contrast medium exceeds 0.01 mmol/kg. These findings are essential for accurate quantification of myocardial blood flow from perfusion MRI.

Multimodality therapy using brachytherapy for caval tumor of hepatocellular carcinoma.

BACKGROUND/AIMS: Hepatocellular carcinoma (HCC) invading the inferior vena cava will expose patients to a risk of sudden death. Effective therapeutic approaches have not been established for caval tumor. This pilot study was conducted to evaluate the feasibility, safety, and clinical efficacy of multimodality therapy using endovascular brachytherapy with iridium-192 for caval tumor. METHODOLOGY: Six consecutive patients underwent endovascular high-dose-rate brachytherapy. An iridium-192 source was placed adjacent to the caval tumor through a vascular sheath introduced via the femoral vein. The total dose of brachytherapy ranged from 10 to 14Gy (5-7Gy per fraction). Hepatic arterial infusion chemotherapy was used in combination in all patients and external-beam radiotherapy was performed in 5 patients. RESULTS: Endovascular brachytherapy was technically successful in all patients. There were no complications related to brachytherapy. The median period of follow-up was 14.5 months (range, 3-29 months). Complete response and partial response were achieved in 2 (33%) and 4 (67%) patients, respectively. The 1- and 2-year survival rates were 50% and 17%, respectively, with a median survival of 14 months. CONCLUSIONS: Multimodality therapy using endovascular brachytherapy was a feasible, safe, and effective treatment for patients with advanced HCC invading the inferior vena cava.