title: Delayed contrast agent kinetics in ischemic skeletal muscle.
abstract: OBJECTIVE
  To detect skeletal muscle ischemia with first-pass gadolinium (Gd) kinetics after exercise.
  
  
  METHODS
  Eleven subjects with intermittent claudication performed a symptom-limited bilateral plantar flexion exercise in the magnet. Regional ROIs were placed bilaterally in the gastrocnemius and soleus muscles, and a signal intensity (SI) time-curve analysis was performed. Induced ischemia was validated prior to the MRI with the systolic ankle-arm blood pressure index (AAI) measured after a symptom-limited treadmill exercise.
  
  
  RESULTS
  Exercise induced ischemic pain in 16 of 22 legs with a significantly reduced AAI (0.31 +/- 0.15). The time to contrast arrival (TCA) was delayed in symptomatic ischemic legs vs. asymptomatic legs (16.3 +/- 6.9 seconds vs. 11.1 +/- 2.7 seconds, P < 0.05). The maximum SI during recovery was higher in the soleus muscle than in the gastrocnemius muscle in ischemic legs (1.55 +/- 0.1 vs. 1.44 +/- 0.1, P < 0.05). Symptomatic regions had a less steep upslope than asymptomatic regions (43 +/- 15 vs. 63 +/- 14, P < 0.001), with a graded upslope response to ischemia. However, a normal upslope was found in 10 of 29 ischemic regions, and some of the regions showed delayed contrast arrival, suggesting a pseudonormal upslope in ischemic regions.
  
  
  CONCLUSIONS
  Exercise-induced ischemia was detected with the use of an SI time-curve analysis. However, disregarding the arterial input function and distribution volume of the tracer may lead to misinterpretation of some ischemic regions.
authors.affiliation: Department of Clinical Physiology, Karolinska Institute, Stockholm Söder Hospital, Stockholm, Sweden.
authors.forename: Anders T
authors.initials: AT
authors.lastname: Nygren
authors.forename: Dan
authors.initials: D
authors.lastname: Greitz
mesh_terms: D000367:Age Factors; D000368:Aged; D000704:Analysis of Variance; D015331:Cohort Studies; D003287:Contrast Media / Q000493:pharmacokinetics; D005080:Exercise Test; D005260:Female; D005682:Gadolinium / Q000493:pharmacokinetics*; D006801:Humans; D007383:Intermittent Claudication / Q000175:diagnosis* / Q000453:epidemiology; D007511:Ischemia / Q000175:diagnosis*; D007866:Leg; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000098:blood supply*; D011336:Probability; D012307:Risk Factors; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D012737:Sex Factors; D013997:Time Factors
chemical_list: D003287:Contrast Media; D005682:Gadolinium