Proton spectroscopic imaging (Dixon method) of the liver: clinical utility

The contribution of proton spectroscopic (PS) imaging to magnetic resonance (MR) imaging of the liver was assessed at 0.5 T in 55 patients with known or suspected hepatic malignancy. PS images were compared subjectively with T1- and T2-weighted spin-echo (SE) images for hepatic lesion detection and conspicuity. For hepatic metastases (n = 27), PS images were equal to T1-weighted images in lesion detection in 17 patients but showed fewer lesions in five patients and false-negative results in two. When compared with T2-weighted images, PS images depicted more lesions in six patients, an equal number of lesions in 18, and fewer lesions in two. Hepatomas (n = 8) were detected with each sequence in all patients. Hepatomas were often more conspicuous on PS images than on T2-weighted images; they were of equal conspicuity on PS and T1-weighted images in most cases. Whereas fatty infiltration (n = 16) appeared on PS images as areas of low signal intensity similar to that of paraspinal muscle, it produced no detectable abnormality on either T1- or T2-weighted images. PS imaging is inferior to T1-weighted SE imaging in the detection of hepatic metastases. The major role of PS imaging at intermediate field strength is to differentiate focal fatty infiltration from hepatic metastases.     

Glenoid labrum: preliminary work with use of radial-sequence MR imaging

The authors describe a magnetic resonance imaging method for examination of the glenoid labrum of the shoulder joint that utilizes a radial fast-imaging sequence. Seven shoulders were examined: a total of five in three healthy asymptomatic volunteers, one in a symptomatic patient not suspected of having a lesion of the glenoid labrum, and one in a patient with recurrent shoulder dislocation and surgical proof of an extensive tear of the labrum. The preliminary results suggest that this technique may advantageously demonstrate pathologic changes in the glenoid labrum and may contribute to the evaluation of the unstable and painful shoulder.     

Aspirin in coronary artery surgery: 1-year results of the Aspirin and Tranexamic Acid for Coronary Artery Surgery trial

Background

Aspirin may reduce the risk of vascular graft thrombosis after cardiovascular surgery. We previously reported the 30-day results of a trial evaluating aspirin use before coronary artery surgery. Here we report the 1-year outcomes evaluating late thrombotic events and disability-free survival.

Conditioning the Cortical Silent Period with Paired Transcranial Magnetic Stimulation

BackgroundA single supra-threshold pulse of transcranial magnetic stimulation (TMS) over human motor cortex elicits multiple descending volleys (I-waves) that generate a motor evoked potential (MEP) followed by a period of electromyographic silence in the tonically contracted target muscle (silent period; SP). A sub-threshold conditioning stimulus (CS) delivered at inter-pulse intervals (IPIs) of 1-5 ms after a supra-threshold test stimulus (TS) conditions I-waves elicited by TS and can increase MEP amplitude (short-interval intracortical facilitation; SICF), however its effect on the SP remains unknown.ObjectiveWe investigated whether it is possible to modulate the SP resulting from a TS by delivering a sub-threshold CS 1–5 ms later.MethodsPaired-pulse TMS was delivered while subjects performed slight contraction of the first dorsal interosseous muscle. SICF and SP duration were measured at each IPI and compared to amplitude-matched MEPs evoked by single-pulse TMS.ResultsPaired stimulation at IPI 2–5 ms prolonged the SP by 21 ± 3% (P < 0.001) but had no effect on MEP amplitude. At shorter IPIs the CS increased MEP amplitude (by 170 ± 31%), but the SP was not prolonged when compared to an amplitude-matched single-pulse stimulus.ConclusionThe SP can be modified by a CS applied during the early phase of its genesis. We suggest that this is in keeping with an early GABA_A contribution to the SP, and it is possible that this new conditioning paradigm may offer another means for probing the excitability of cortical inhibitory networks in human motor cortex.     

Inverse Correlation Between Resting Motor Threshold and Corticomotor Excitability After Static Magnetic Stimulation of Human Motor Cortex

BackgroundHigh-strength static magnetic field stimulation (SMS) results in a period of reduced corticomotor excitability that may be mediated through a decrease in membrane excitability.ObjectiveAs resting motor threshold (RMT) is thought to reflect membrane excitability, we hypothesized that SMS may increase RMT and that there would be an inverse relationship between RMT and motor-evoked potential (MEP) amplitude.MethodsTen healthy subjects (aged 20–29; 4 females) participated in a double-blinded crossover design comparing MEP amplitude and RMT before and after a 15-min period of SMS or sham stimulation over primary motor cortex (M1).ResultsMEP amplitude was initially significantly reduced post-SMS (～20%), and returned to baseline by 6 min post-intervention. MEP amplitude and RMT were inversely correlated (r² = 0.924; P = 0.001). Sham stimulation had no effect on MEP amplitude (P = 0.969) or RMT (P = 0.549).ConclusionAfter SMS, corticomotor excitability is transiently reduced in association with a correlated modulation of RMT. SMS after effects may be mediated in part by a reduction in membrane excitability, suggesting a possible role for non-synaptic (intrinsic) plasticity mechanisms.     

Caudal-posteroanterior view in coronary arteriography

Posteroanterior (PA) and caudally angulated PA views were obtained in 20 patients undergoing routine coronary arteriography. Although the left main coronary artery (LMCA) was seen well on both views in all patients, the PA-caudal view improved depiction of the LMCA bifurcation in 15 (75%). In addition, the PA-caudal view markedly improved depiction of the circumflex artery, affording optimal depiction of this artery and its branches in 78%-89% of patients. Neither the PA nor the PA-caudal view allowed adequate depiction of the left anterior descending artery. Thus, the PA-caudal view should supplant the PA view in routine coronary arteriography.