Monday Case of the Day Physics Tianliang Gu, Ph.D. Lino Grillo (RT) Baylor University Medical Center, Dallas, TX History: The patient came with the contrast injection catheter set about 20 cm distal to the median cubital vein (usually the injection vein). Scan parameters on 3T MRI: TR/TE (1320/30ms); flip angle: 30. 15 ml contrast was injected in 3 seconds. 6 phases were acquired before contrast injection. The most likely reason: A. Improper scan parameters. B. Susceptibility artifacts. C. Incorrect injection starting time. D. Diluted contrast bolus. a b Figure 1: Left (a) is the poor quality MR perfusion relative blood volume (rCBV) map. (b) is the rCBV map at the same location acquired when the patient was recalled.

Diagnosis and Discussions Correct answer: D). As shown in Figure 2 (a), the arterial input function (AIF) was wide. Fitting errors were large using the GE perfusion software. The contrast arrival time was not affected by the distal catheter location. However the contrast was diluted before it traveled to the median cubital vein. When the patient was recalled for a second study, the contrast was inject through the median cubital vein. Contrast arrival, signal drop and recovery were well defined in Figure 2(b). The fitting errors were small. Correct rCBV maps were generated as shown in Figure 1(b). a b Figure 2: Left (a) is the arterial input function (AIF) from the diluted bolus. Right (b) is the AIF for the contrast injected at the right location. Green lines are mean signal intensity inside the region of interest. Red lines are the fitted plots generated by the GE perfusion software.