Clinical cardiovascular magnetic resonance imaging

Measurement of pancreatic volume by abdominal MRI: a validation study

Objective

To develop abdominal magnetic resonance imaging (MRI) protocol to measure pancreatic volume in humans and to validate it in large animals.

Materials and Methods

We performed abdominal MRI in eight mini-pigs using a clinical 3T MRI system. We used consecutive parallel abdominal slices, covering the entire pancreas to calculate pancreatic volume. Following MRI, animals were sacrificed, the pancreas was removed, and the volume of the pancreas was measured by water displacement. We used the same MRI protocol to measure pancreatic volume in 21 humans. To assess reproducibility of in vivo measurement we repeated MRI pancreas volume evaluation within 24 hours in additional five humans.

Results

In mini-pigs the measurements of pancreatic volume by MRI and by water displacement were almost identical (R² = 0.9867; p<0.0001). In humans the average pancreas volume was 72.7+/−4.5 ml, range from 35.0 to 105.5 ml. This result is in strong agreement with results of previous large postmortem and computed tomography (CT) studies. Repeated measurements of pancreatic volume in humans were highly reproducible. Pancreatic volume measured in vivo was negatively correlated with age, body fat mass, pancreatic TG levels, and visceral fat mass.

Conclusions

These initial results are highly encouraging and our protocol for pancreatic volume estimation in vivo may prove useful in obesity research to follow in vivo changes of pancreatic volume and structure during time course of obesity and type 2 diabetes development.

Role of magnetic resonance contrast agents in cardiac imaging

Improvements in magnetic resonance imaging (MRI) technology allow adequate spatial and temporal resolution to capture cardiac anatomy and contractile function in exceptional detail and with little risk. However, tissue characterization of the pathophysiologic state of the myocardium may require special indicators or MR contrast agents. These must be tailored for detection by the MRI process, but available agents are effective at low dose and provide a wide range of indicator properties (e.g., myocardial extracellular space, blood pool, capillary permeability and membrane transport). Each agent has a dynamic washin and washout time-intensity curve that may reflect myocardial perfusion or consequences of ischemia. The combined use of MRI and MR contrast agents may provide a single diagnostic examination that fully and quantitatively assesses all indexes of cardiac performance. Such information would be both global and regional, and would be well tolerated by patients. The cost, value and cost-effectiveness of such studies remain speculative.