Impact of Gradient Nonlinearity on the Accuracy of NMR Field Camera Readouts

Field monitoring using NMR field cameras typically use the gradients for calculating the positions of the field probes. However this is under the assumption that the gradients are linear which is certainly not the case. The effect of evaluated gradient imperfections on the estimation of the probes was investigated. Furthermore, the effect of the position error on monitoring higher order spherical harmonics was also investigated. A CT scan of the field camera setup was used to correct for errors in the calculations of the probe position

Perfusion measurements of the calf in patients with peripheral arterial occlusive disease before and after percutaneous transluminal angioplasty using Mr arterial spin labeling

Purpose To evaluate muscle perfusion in patients with peripheral arterial occlusive disease (PAOD) before and after percutaneous transluminal angioplasty (PTA) of the limb by means of MR arterial spin labeling (ASL) perfusion measurements during reactive hyperemia. Materials and Methods Ten patients with symptomatic PAOD affecting the iliac or femoral vessels were investigated before and after PTA. A pseudo-continuous arterial spin labeling (PCASL) MR technique was applied. Perfusion was measured in soleus and tibialis anterior muscle during reactive hyperemia. Key parameters such as mean perfusion value (Phyp), time-to-peak (TTP) and duration of hyperemia (Thyp) describing the perfusion signal curve were examined. Results Between baseline and post-PTA, Phyp increased in both muscle groups. At the same time, TTP and Thyp decreased in both muscle groups. At the same time the clinically assessed ankle brachial index (ABI) increased from 0.56thinsp;plusmn;thinsp;0.10 to 0.83thinsp;plusmn;thinsp;0.15. The impaired pain-free walking distance improved in all patients. Conclusion PCASL MRI can detect changes of the key perfusion parameters Phyp, TTP, and Thyp after successful PTA of the calf muscles during reactive hyperemia and seems to be a promising tool for monitoring of interventional treatments

Acquired arteriovenous fistula of a finger.

Arteriovenous fistulae are defined as congenital or acquired abnormal direct communications between an artery and a vein leading to abnormal blood circulation. This report describes an unusual manifestation of an acquired peripheral arteriovenous fistula with a high shunt volume of 410 ml/min following a fracture of the 5th finger