CO2 induced pHi changes in the brain of polar fish: a TauCEST application

Chemical exchange saturation transfer (CEST) from taurine to water (TauCEST) can be used for in vivo mapping of taurine concentrations as well as for measurements of relative changes in intracellular pH (pH_i) at temperatures below 37°C. Therefore, TauCEST offers the opportunity to investigate acid–base regulation and neurological disturbances of ectothermic animals living at low temperatures, and in particular to study the impact of ocean acidification (OA) on neurophysiological changes of fish. Here, we report the first in vivo application of TauCEST imaging. Thus, the study aimed to investigate the TauCEST effect in a broad range of temperatures (1–37°C) and pH (5.5–8.0), motivated by the high taurine concentration measured in the brains of polar fish. The in vitro data show that the TauCEST effect is especially detectable in the low temperature range and strictly monotonic for the relevant pH range (6.8–7.5). To investigate the specificity of TauCEST imaging for the brain of polar cod (Boreogadus saida) at 1.5°C simulations were carried out, indicating a taurine contribution of about 65% to the in vivo expected CEST effect, if experimental parameters are optimized. B. saida was acutely exposed to three different CO₂ concentrations in the sea water (control normocapnia; comparatively moderate hypercapnia OA_m = 3300 μatm; high hypercapnia OA_h = 4900 μatm). TauCEST imaging of the brain showed a significant increase in the TauCEST effect under the different CO₂ concentrations of about 1.5–3% in comparison with control measurements, indicative of changes in pH_i or metabolite concentration. Consecutive recordings of ¹H MR spectra gave no support for a concentration induced change of the in vivo observed TauCEST effect. Thus, the in vivo application of TauCEST offers the possibility of mapping relative changes in pH_i in the brain of polar cod during exposure to CO₂.     

Brain volume perfusion CT performed with 128-detector row CT system in patients with cerebral gliomas: A feasibility study

Objectives  

Validation of the feasibility and efficacy of volume perfusion computed tomography (VPCT) in the preoperative assessment of cerebral gliomas by applying a 128-slice CT covering the entire tumour.     

Genetic analysis of a transposable suppressor gene in Saccharomyces cerevisiae.

We have demonstrated in Saccharomyces cerevisiae the transposition of a gene coding for an efficient ochre (UAA) suppressor from a centromere-linked site on chromosome III to two new sites in the yeast genome. One site is on chromosome VI, very close to, if not allelic with, SUP11, one of eight genes coding for a tyrosine-inserting suppressor. The second site is on chromosome III, unlinked to the centromere and distal to the mating type locus. This site is very close to those mapped for the recessive lethal amber suppressors, SUP-RL1 and SUP61.     

Surgical Outcomes and Predicting Factors of Curative Resection in Patients with Hilar Cholangiocarcinoma: 10-Year Single-Institution Experience

Background

The surgical resection of hilar cholangiocarcinoma is extremely challenging because the tumor is closely related with the complicated hilar structures. We investigated to identify the outcomes for patients who underwent surgical resection and to identify the parameters that influenced radical resection.

Methods

From January 2000 to December 2009, 105 patients underwent surgical resection for hilar cholangiocarcinoma. The clinicopathological parameters and surgical outcomes were retrospectively analyzed.

Results

There were 15 operative mortalities (14.3%). Seventy-four patients underwent curative resection (70.5%). The median overall survival time for R0, R1, and R2 were 58, 28, and 19?months, respectively. Caudate lobectomy (p?=?0.044; odds ratio [OR], 4.386) and perineural invasion (p?=?0.01; OR, 0.062) were correlated with curative resection. Total bilirubin levels of more than 3?g/dl just before the operation (p?=?0.042; hazard ratio [HR], 2.109) and extent of resection (R1 and 2 vs R0; p?=?0.05; HR, 2.309) were selected as significantly negative factors affecting overall survival on the multivariate analysis.

Conclusions

Caudate lobectomy and neurectomy may be thought of as adjustable territories by the surgeon??s efforts to achieve curative resection. R0 resection achieved through those efforts and liver optimization using preoperative biliary drainage may offer the patients a chance of cure.     

Parallel image reconstruction using B-spline approximation (PROBER).

A new reconstruction method for parallel MRI called PROBER is proposed. The method PROBER works in an image domain similar to methods based on Sensitivity Encoding (SENSE). However, unlike SENSE, which first estimates the spatial sensitivity maps, PROBER approximates the reconstruction coefficients directly by B-splines. Also, B-spline coefficients are estimated at once in order to minimize the reconstruction error instead of estimating the reconstruction in each pixel independently (as in SENSE). This makes the method robust to noise in reference images. No presmoothing of reference images is necessary. The number of estimated parameters is reduced, which speeds up the estimation process. PROBER was tested on simulated, phantom, and in vivo data. The results are compared with commercial implementations of the algorithms SENSE and GRAPPA (Generalized Autocalibrating Partially Parallel Acquisitions) in terms of elapsed time and reconstruction quality. The experiments showed that PROBER is faster than GRAPPA and SENSE for images wider than 150x150 pixels for comparable reconstruction quality. With more basis functions, PROBER outperforms both SENSE and GRAPPA in reconstruction quality at the cost of slightly increased computational time.     

Quantification of renal perfusion abnormalities using an intravascular contrast agent (part 2): results in animals and humans with renal artery stenosis.

The interrelation between the morphologic degree of renal artery stenosis and changes in parenchymal perfusion is assessed using an intravascular contrast agent. In seven adult foxhounds, different degrees of renal artery stenosis were created with an inflatable clamp implanted around the renal artery. Dynamic susceptibility-weighted gradient-echo imaging was used to measure signal-time curves in the renal artery and the renal parenchyma during administration of 1.5 mg/kg BW of an intravascular ultrasmall particle iron oxide (USPIO) contrast agent. From the dynamic series, regional renal blood volume (rRBV), regional renal blood flow (rRBF), and mean transit time (MTT) were calculated. The morphologic degree of stenosis was measured in the steady state using a high-resolution 3D contrast-enhanced (CE) MR angiography (MRA) sequence (voxel size = 0.7 x 0.7 x 1 mm(3)). Five patients with renoparenchymal damage due to long-standing renal artery stenosis were evaluated. In the animal stenosis model, cortical perfusion remained unchanged for degrees of renal artery stenosis up to 80%. With degrees of stenoses > 80%, cortical perfusion dropped to 151 +/- 54 ml/100 g of tissue per minute as compared to a baseline of 513 +/- 76 ml/100 g/min. In the patients, a substantial difference in the cortical perfusion of more than 200 +/- 40 ml/100 g/min between the normal and the ischemic kidneys was found. The results show that quantitative renal perfusion measurements in combination with 3D-CE-MRA allow the functional significance of a renal artery stenosis to be determined in a single MR exam. Differentiation between renovascular and renoparenchymal disease thus becomes feasible.     

Comparison of different risk-adjustment models in assessing short-term surgical outcome after transthoracic esophagectomy in patients with esophageal cancer

Background

Different risk-prediction models have been developed, but none is generally accepted in selecting patients for esophagectomy. This study evaluated 5 most frequently used risk-prediction models, including the American Society of Anesthesiologists, Portsmouth-modified Physiological and Operative Severity Score for the enUmeration of Mortality and morbidity (P-POSSUM), and the adjusted version for Oesophagogastric surgery (O-POSSUM), Charlson and the Age adjusted Charlson score to assess postoperative mortality after transthoracic esophagectomy.

Methods

Data were obtained from 278 consecutive esophageal cancer patients between 1991 and 2007. Performance in predicting postoperative mortality (in-hospital and 90-day mortality) were analyzed regarding calibration (Hosmer and Lemeshow goodness-of-fit test) and discrimination (area under the receiver operator curve).

Results

The Hosmer and Lemeshow goodness-of-fit test was applied to each model and showed a significant outcome for only the P-POSSUM score (P = .035). The receiver operator curve indicated discriminatory power for P-POSSUM (.766) and for O-POSSUM (.756), other models did not exceed the minimal surface of .7.

Conclusions

Postoperative mortality after esophagectomy was best predicted by O-POSSUM. However, it still overpredicted postoperative mortality.     

Ultrasound as visual feedback in speech habilitation: Exploring consultative use in rural British Columbia,Canada

Ultrasound has shown promise as a visual feedback tool in speech therapy. Rural clients, however, often have minimal access to new technologies. The purpose of the current study was to evaluate consultative treatment using ultrasound in rural communities. Two speech‐language pathologists (SLPs) trained in ultrasound use provided consultation with ultrasound in rural British Columbia to 13 school‐aged children with residual speech impairments. Local SLPs provided treatment without ultrasound before and after the consultation. Speech samples were transcribed phonetically by independent trained listeners. Eleven children showed greater gains in production of the principal target // after the ultrasound consultation. Four of the seven participants who received more consultation time with ultrasound showed greatest improvement. Individual client factors also affected outcomes. The current study was a quasi‐experimental clinic‐based study. Larger, controlled experimental studies are needed to provide ultimate evaluation of the consultative use of ultrasound in speech therapy.     

Dynamic coil selection for real-time imaging in interventional MRI.

MR-guided intravascular interventions require image update rates of up to 10 images per second, which can be achieved using parallel imaging. However, parallel imaging requires many coil elements, which increases reconstruction times and thus compromises real-time image reconstruction. In this study a dynamic coil selection (DCS) algorithm is presented that selects a subset of receive coils to reduce image reconstruction times. The center-of-sensitivity coordinates and the relative signal intensities are determined for each coil in a prescan. During the intervention m coils are selected for reconstruction using a coil ranking based on the distance to the current slice or catheter position. In a phantom experiment for m = 6, an optimal signal-to-background ratio (SBR) was achieved and foldover artifacts were avoided. In three animal experiments involving catheter manipulation in the aorta and the right heart chamber, the anatomy was successfully visualized at frame rates of about 5 Hz using active catheter tracking.