Time to Peak Enhancement Shows Linear Relationship

A recent study was conducted to evaluate the relationship between the times to peak enhancement of the liver, pancreas, and jejunum to that of the aorta during MR imaging. There is a linear relationship between the times to peak enhancement of the liver, pancreas, and jejunum and that of the aorta.

Participants
In this retrospective analysis, 141 patients who had undergone timing bolus transverse imaging of the midabdominal aorta as part of their abdominal MR examination.

Methodology
Indications for MR examination included liver lesions, renal artery stenosis, abdominal pain, pancreatitis, renal lesions, venous thrombosis, and abdominal mass. Medical records were also reviewed to assess for the presence of clinical disease of the liver, pancreas, jejunum, and heart.

Any history of cirrhosis, noncirrhotic liver disease, pancreatitis, pancreatic neoplasm, jejunal disease, and cardiac disease was recorded. MR imaging was performed with a 1.5-Tesla system utilizing a phased array coil.

A transverse T1 spoiled gradient-echo image was centered on the midabdominal aorta and repeated every second from the start of the injection up to 2 minutes.

Results
The times to peak enhancement of the aorta, liver, pancreas, and jejunum had a wide inter-patient variation. The mean times to peak enhancements were approximately:

• aorta, 21 seconds;
• pancreas, 32 seconds;
• jejunum, 37 seconds;
• liver, 57 seconds;
  

Therefore, a longer time to peak enhancement of the aorta can be used to predict a proportionally longer time to peak enhancement of these organs.

There was no difference in mean time to peak hepatic enhancement among patients without liver disease or in patients with noncirrhotic liver disease or cirrhosis.

The inclusion of demographic information (eg, age, sex, and presence of cardiac disease) did not improve the ability to predict the time to peak organ enhancement beyond that which could be predicted using the time to peak enhancement of the aorta alone.

Reviewer’s Comments
These useful results demonstrate that the length of time to peak enhancement of the pancreas, jejunum, and liver increases linearly with that of the aorta. Consequently, if there is a longer time to peak aortic enhancement, one can estimate a proportionally longer time to peak enhancement of these organs.

This can help estimate the scan delay needed in a patient to acquire images of certain organs in a consistent and reproducible manner.

A limitation noted in this study was that the primary focus was on describing the relationship between the times of peak aortic and visceral enhancement. Therefore, the results were not applied to clinical MR examinations to optimize organ parenchymal enhancement.

Author: John C. Sabatino, MD

Reference:
Chu LL, Joe BN, et al. Patient-Specific Time to Peak Abdominal Organ Enhancement Varies With Time to Peak Aortic Enhancement at MR Imaging. Radiology; 2007; 245 (December): 779-787