Comparison of single-shot echo-planar and line scan protocols for diffusion tensor imaging

RATIONALE AND OBJECTIVES: Both single-shot diffusion-weighted echo-planar imaging (EPI) and line scan diffusion imaging (LSDI) can be used to obtain magnetic resonance diffusion tensor data and to calculate directionally invariant diffusion anisotropy indices, ie, indirect measures of the organization and coherence of white matter fibers in the brain. To date, there has been no comparison of EPI and LSDI. Because EPI is the most commonly used technique for acquiring diffusion tensor data, it is important to understand the limitations and advantages of LSDI relative to EPI. MATERIALS AND METHODS: Five healthy volunteers underwent EPI and LSDI diffusion on a 1.5 Tesla magnet (General Electric Medical Systems, Milwaukee, WI). Four-mm thick coronal sections, covering the entire brain, were obtained. In addition, one subject was tested with both sequences over four sessions. For each image voxel, eigenvectors and eigenvalues of the diffusion tensor were calculated, and fractional anisotropy (FA) was derived. Several regions of interest were delineated, and for each, mean FA and estimated mean standard deviation were calculated and compared. RESULTS: Results showed no significant differences between EPI and LSDI for mean FA for the five subjects. When intersession reproducibility for one subject was evaluated, there was a significant difference between EPI and LSDI in FA for the corpus callosum and the right uncinate fasciculus. Moreover, errors associated with each FA measure were larger for EPI than for LSDI. CONCLUSION: Results indicate that both EPI- and LSDI-derived FA measures are sufficiently robust. However, when higher accuracy is needed, LSDI provides smaller error and smaller inter-subject and inter-session variability than EPI.     

The effects of prolonged ambulation on labor with epidural analgesia

Ambulation during labor is becoming more popular, although its impact on the progress of labor and on pain intensity remains unclear. We wondered whether prolonged ambulation with epidural analgesia had a possible effect on duration of labor and pain. In this prospective, randomized trial, 61 parturients with uncomplicated term pregnancies were allocated to be recumbent (n = 31) or to ambulate (n = 30). Epidural analgesia was provided with intermittent administrations of 0.08% bupivacaine-epinephrine plus 1 microg/mL of sufentanil. Of the 30 women assigned to the ambulatory group, 25 actually walked. Their ambulating time was 64 +/- 34 min (mean +/- SD), i.e., 29% +/- 16% of the first stage. There were no differences between the two groups in the length of labor and in pain visual analog scale scores. However, the ambulatory group received smaller doses of bupivacaine (6.4 +/- 2.2 mg/h versus 8.4 +/- 3.6 mg/h; P = 0.01) and of oxytocin (6.0 +/- 3.7 mUI/min versus 10.2 +/- 8.8 mUI/min; P < 0.05). A greater ability to void was also found in the ambulatory group (P < 0.01). Although the duration of labor and pain relief was unchanged, these findings support that ambulation during labor may be advantageous. IMPLICATIONS: This study compared the duration of labor and pain relief between parturients receiving epidural analgesia who were ambulated or were recumbent. Whereas walking had no impact on either duration of labor or pain relief, it was associated with a reduction in both bupivacaine and oxytocin requirements.     

Lower dose intraventricular T-PA fibrinolysis: case report

BACKGROUND: Recombinant tissue plasminogen activator (rtPA) intraventricular fibrinolysis has been demonstrated to be efficacious in clearing blood from the ventricular system. Preliminary studies indicate it may improve survival. There have also been reports of adverse affects from intraventricular fibrinolysis. Optimal dosing of rtPA has not been established. METHODS: A 40-year-old patient with intraventricular hemorrhage extension secondary to a ruptured aneurysm was treated with a one-time infusion of 1 mg of rtPA through a right ventriculostomy. RESULTS: Computed tomography scans demonstrated excellent resolution of intraventricular blood and improvement in cerebral spinal fluid flow after fibrinolysis. Fibrinolysis was most marked in the third and fourth ventricles. There were no adverse effects noted. CONCLUSIONS: Intraventricular fibrinolysis is effective at a lower dose than previously used. Lower doses may have fewer adverse affects.     

Creatinine levels among Mexican Americans, Puerto Ricans, and Cuban Americans in the Hispanic Health and Nutrition Examination Survey

BACKGROUND: Although Latinos constitute the largest and fastest growing minority group in the United States, little is known about the prevalence of renal disease among different Latino subgroups. METHODS: We used data from the Hispanic Health and Nutrition Examination Survey (HHANES) to compare serum creatinine measurements among Mexican Americans, mainland Puerto Ricans, and Cuban Americans. We compared estimated creatinine clearance across Latino subgroups adjusted for demographic, clinical, and socioeconomic characteristics (including known predictors of chronic kidney disease) using survey logistic regression analysis. RESULTS: Cuban Americans had higher mean serum creatinine levels than the other groups across both gender and age categories. In multivariable analysis, Puerto Ricans [odds ratio (OR) 1.74, 95% confidence interval (CI) 1.16 to 2.60] and Cuban Americans (OR 4.59, CI 2.53 to 8.31) were more likely than the referent category of Mexican Americans to have an estimated creatinine clearance < 60 mL/min/1.73 m2. CONCLUSION: Serum creatinine levels differ substantially among Latino subgroups, suggesting national origin needs to be taken into consideration in studies of renal disease in Latinos. In addition, our findings highlight the need for more contemporary studies directly comparing both incidence rates of end-stage renal disease and measured renal function among Latino subgroups, perhaps leading to subgroup-specific prediction equations.     

The effect of hyperbaric oxygen therapy on composite graft survival

Auricular composite grafts are a useful reconstructive option, particularly for nasal reconstruction. This study evaluates the effect of hyperbaric oxygen (HBO) therapy on auricular composite graft survival in rabbits. Circular chondrocutaneous composite grafts of 0.5, 1, or 2 cm in diameter were resected from the ears of rabbits. The grafts were sutured back into position. Half the rabbits in each group received HBO postoperatively, consisting of 90 minutes at 2.4 atm. Rabbits received 7 treatments in 5 days. Control rabbits did not receive HBO. On day 21 the percentage area of graft survival was calculated from gross and histologic examination. Two-centimeter grafts treated with HBO (n = 8) had a mean graft survival rate of 85.8 +/- 15.7% compared with a survival rate of 51.31 +/- 38.5% for the control group (n = 8; P = 0.0478). There was no such benefit in smaller grafts. HBO could prove clinically useful for larger composite grafts.     

Ileocolic Arteriovenous Fistula with Superior Mesenteric Vein Aneurism: Endovascular Treatment

We report a case of a venous aneurysm secondary to an acquired ileocolic arteriovenous fistula in a 64-year-old woman with recurrent abdominal pain and history of appendectomy. The aneurysm was diagnosed by ultrasound and computed tomography. Angiography showed an arteriovenous fistula between ileocolic branches of the superior mesenteric artery and vein. This vascular abnormality was successfully treated with coil embolization.     

Gadolinium-enhanced CT angiography of the circle of Willis and neck

CT angiography (CTA) of the cervical and intracranial vessels is a rapid, noninvasive, and relatively inexpensive technique for the evaluation of vascular abnormalities. Contraindications to the use of contrast media, however, can preclude use of iodinated agents for CTA. We report the use of gadolinium as contrast agent for CTA of the head and neck in three patients with contraindications to iodinated contrast agents.     

Assessment of cardiac wall motion and ejection fraction with gated PET using N-13 ammonia

BACKGROUND: Cardiac gating is not routinely used in cardiac positron emission tomography (PET). The aim of this study was to determine the feasibility of assessing regional wall motion, ejection fraction (EF), cardiac volumes, and mass with nitrogen-13 ammonia (N-13 ammonia) at the time of PET myocardial perfusion imaging. METHODS: We studied 12 healthy volunteers (mean age, 28 +/- 8 years) and 53 patients with documented coronary artery disease (CAD) (mean age, 59 +/- 11 years). All subjects received a single administration of approximately 600 MBq (16 mCi) of N-13 ammonia intravenously. A 6-minute dynamic scan was performed for quantitative assessment of myocardial perfusion at rest, followed by a separate, 13-minute static scan acquired in the gated mode (8 equal bins). Gated data was imported into the Emory Toolbox. Wall motion was evaluated by dividing the myocardium into 9 anatomic regions graded semiquantitatively. RESULTS: Healthy volunteers had a normal EF (61 +/- 6), end systolic volume (ESV) (37 +/- 15 mL), end diastolic volume (EDV) (89 +/- 25 mL), and cardiac mass (116 +/- 18 g). In contrast, patients with CAD showed reduced EF (32 +/- 13%) and increased ESV (129 +/- 56 mL), EDV (188 +/- 68 mL), and cardiac mass (173 +/- 45 g) (P < 0.001 for each). In patients with CAD, EF measured by gated PET correlated significantly to independent measurements of EF (P < 0.001). CONCLUSIONS: Gating of cardiac perfusion images obtained after administration of N-13 ammonia is feasible and appears to be an accurate means of evaluating regional and global cardiac function. Gating can provide important additional diagnostic and prognostic information.