Purpose or Case Report: This study will normalize contrast enhancement curves for three GBCAs in fMRU and use it to assess for differences in renal enhancement characteristics of different GBCAs used in pediatric fMRU.
Methods & Materials: This is a retrospective IRB-approved, HIPAA-compliant study. From all fMRU studies performed at two pediatric institutions between 2007 and 2017, we selected those renal units with normal morphologic features and normal function parameters. Then, the kidneys were grouped according to the contrast agent used at our institutions during the study period (i.e.: gadopentetic acid - Magnevist®; gadoterate meglumine - Dotarem®; and gadobutrol - Gadavist®). Basic demographic information (e.g.; age, sex) was extracted from their electronic medical records.
Results: Out of a total of 2014 renal units, 447 morphologically and functionally normal kidneys were included in the final sample. The median ages for each group was 7.7 years for gadoterate meglumine, 8.9 years for gadobutrol, and 7.3 years for gadopentetic acid. Of the 447 kidneys, 329 (73.6%) were imaged with gadopentetic acid, 65 (14.5%) with gadobutrol and 53 (11.9%) were imaged with gadoterate meglumine.
The 2 min enhancement ratio to baseline of the kidneys, with baseline considered the 1 sec time point, with gadoterate meglumine is 19.6, with gadobutrol is 19.9, and with gadopentetic acid is 17.3.
The percentage change in decreased enhancement within the kidneys after 6 minutes compared to 2 minutes for gadoterate meglumine is 16.1%, 9.2% for gadobutrol, and 18.9% for gadopentetic acid.
Gadoterate meglumine and gadobutrol had similar enhancement ratios to baseline, and gadoterate meglumine had a faster washout compared to gadobutrol.
Time to peak (TTP) was determined, 156 sec for gadoterate meglumine, 168 sec for gadobutrol , and 152 sec for gadopentetic acid.
In the aorta, gadoterate meglumine demonstrated the highest ratio between the minimum and maximum normalized enhancement compared to the other two GBCAs.
Conclusions: We found that the use of a macrocyclic non-ionic agent results in a delayed time to peak and slower washout than both the linear and macrocyclic ionic agents; while the ionic agents behaved similarly in terms of enhancement and transit time. Because basic parameters of fMRU including calyceal and renal transit time as well as the duration of image acquisition for analysis were first determined with an ionic linear agent, the switch to a non-ionic GBCA warrants a re-evaluation of normal ranges for such parameters.