A dedicated automated injection system for dynamic contrast‐enhanced MRI experiments in mice

Purpose:

To develop a reproducible small‐animal dynamic contrast‐enhanced (DCE) MRI set‐up for mice through which volumes <100 μL can be accurately and safely injected and to test this set‐up by means of DCE measurements in resting muscle and tumor tissue.

Materials and Methods:

The contrast agent (CA) injection system comprised 2 MR‐compatible syringe pumps placed 50 cm from the 7T magnet bore where the fringe field is approximately 40 mT. Microbore tubing and T‐connector, close to the injection site, minimized dead volume (<10 μL). For DCE‐MRI measurements in 8 CB‐17 SCID mice with 1500–2500 mm³ large orthotopic neuroblastoma, a bolus of 10‐fold‐diluted Gd‐DTPA CA solution (0.1 mmol/kg) was delivered (5 μL/s), followed by a 50‐μL saline flush. Retro‐orbital injections were given instead of tail vein injections, because the peripheral vasculature was reduced because of large tumor burden.

Results:

The CA injection was successful in 19 of 24 experiments. Optical assessment showed minimal dispersion of ink‐colored CA bolus. Mean (±SD) pharmacokinetic parameters retrieved from DCE‐MRI examinations in resting muscle (K^trans = 0.038 ± 0.025 min^?1, k_ep = 0.66 ± 0.48 min^?1, v_e = 0.060 ± 0.014, v_p = 0.033 ± 0.021) and tumor (K^trans = 0.082 ± 0.071 min^?1, k_ep = 0.82 ± 0.80 min^?1, v_e = 0.121 ± 0.075, v_p = 0.093 ± 0.051) agreed with those reported previously.

Conclusion:

We successfully designed and implemented a DCE‐MRI set‐up system with short injection lines and low dead volume. The system can be used at any field strength with the syringe pumps placed at a sufficiently low fringe field (<40 mT). J. Magn. Reson. Imaging 2013;37:746–751. © 2012 Wiley Periodicals, Inc.

     

Time course of 23Na signal intensity after myocardial infarction in humans.

Experimental studies demonstrated persistently increased 23Na content in nonviable myocardium post-myocardial infarction (MI). We hypothesized that nonviable myocardium in humans would show elevated 23Na content at all stages of infarct development, and therefore could be imaged with 23Na MRI. Ten patients were examined on days 4, 14, and 90 after infarction, and five of these patients participated in a 12-month follow-up. Double angulated short-axis cardiac 23Na images were obtained with the use of a 23Na surface coil and an ECG-triggered, 3D gradient-echo sequence. 1H T2-weighted imaging (N = 9) was performed on days 4, 14, and 90. Wall motion was assessed by cine MRI, and the infarct size was determined by late enhancement on day 90. The 23Na signal intensity (SI) of infarcted myocardium was expressed as the percentage increase over 23Na SI of noninfarcted myocardium. All of the patients showed an area of elevated SI on 23Na and 1H T2-weighted images that correlated with wall motion abnormalities and late enhancement. 23Na SI was highest on day 4. It then decreased until day 90, but remained elevated (39% +/- 18%, 31% +/- 17%, 28% +/- 13% on days 4, 14, and 90, respectively, P = 0.001). No further decrease was found 1 year after infarction (25% +/- 7%, P = 0.89 vs. day 90). 1H T2-weighted SI decreased between days 4 and 14, but on day 90 only six of nine patients had a residual elevated SI. Thus, 23Na SI is elevated in nonviable infarction at all time points following MI, and 23Na MRI may become a suitable technique for imaging nonviable myocardium in humans.     

Speech synthesis using damped sinusoids.

A speech synthesizer was developed that operates by summing exponentially damped sinusoids at frequencies and amplitudes corresponding to peaks derived from the spectrum envelope of the speech signal. The spectrum analysis begins with the calculation of a smoothed Fourier spectrum. A masking threshold is then computed for each frame as the running average of spectral amplitudes over an 800-Hz window. In a rough simulation of lateral suppression, the running average is then subtracted from the smoothed spectrum (with negative spectral values set to zero), producing a masked spectrum. The signal is resynthesized by summing exponentially damped sinusoids at frequencies corresponding to peaks in the masked spectra. If a periodicity measure indicates that a given analysis frame is voiced, the damped sinusoids are pulsed at a rate corresponding to the measured fundamental period. For unvoiced speech, the damped sinusoids are pulsed on and off at random intervals. A perceptual evaluation of speech produced by the damped sinewave synthesizer showed excellent sentence intelligibility, excellent intelligibility for vowels in /hVd/ syllables, and fair intelligibility for consonants in CV nonsense syllables.     

Cough induced rib fracture, rupture of the diaphragm and abdominal herniation

Cough can be associated with many complications. In this article, we present a 59 year old male patient with a very rare combination of a cough related stress fracture of the ninth rib, a traumatic rupture of the diaphragm, and an abdominal wall herniation. The hernia was repaired through surgical treatment without bowel resection, the diaphragm and the internal and oblique abdominal muscle were adapted, and the abdomen was reinforced with a prolene net.     

Improved renal perfusion measurement with a dual navigator‐gated Q2TIPS fair technique

A dual navigator‐gated, flow‐sensitive alternating inversion recovery (FAIR) true fast imaging with steady precession (True‐FISP) sequence has been developed for accurate quantification of renal perfusion. FAIR methods typically overestimate renal perfusion when respiratory motion causes the inversion slice to move away from the imaging slice, which then incorporates unlabeled spins from static tissue. To overcome this issue, the dual navigator scheme was introduced to track inversion and imaging slices, and thus to ensure the same position for both slices. Accuracy was further improved by a well‐defined bolus length, which was achieved by a modification version of Q2TIPS (quantitative imaging of perfusion using a single subtraction, second version with interleaved thin‐slice TI₁ periodic saturation): a series of saturation pulses was applied to both sides of the imaging slice at a certain time after the inversion. The dual navigator‐gated technique was tested in eight volunteers. The measured renal cortex perfusion rates were between 191 and 378 mL/100 g/min in the renal cortex with a mean of 376 mL/100 g/min. The proposed technique may prove most beneficial for noncontrast‐based renal perfusion quantification in young children and patients who may have difficulty holding their breath for prolonged periods or are sedated/anesthetized. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.     

Sepsis induced changes of adipokines and cytokines - septic patients compared to morbidly obese patients

Background  

Hyperglycemia and insulin resistance frequently occur in critically ill and in morbidly obese (MO) patients. Both conditions are associated with altered serum levels of cytokines and adipokines. In addition, obesity related alterations in adipokine expression contribute to insulin resistance in metabolic syndrome. In this study we examined the serum adipocytokine profile in critically ill patients, MO patients, and healthy blood donors.     

Kombinationsbehandlung mit Perampanel

Perampanel was recently approved in Germany for add-on treatment of patients with focal epileptic seizures from the age of 12 years. The approval resulted from three randomized placebo controlled trials and patients who had been treated during these trials could enter an open long-term follow-up study and continue taking perampanel. Very occasionally patients treated in such studies become seizure-free for a longer period of time. This article reports on a 20-year-old female patient who gained freedom from seizures with 12 mg perampanel per day in combination with a baseline antiepileptic drug treatment consisting of levetiracetam and lacosamide. Baseline seizure frequency had previously been around 25 dyscognitive focal seizures per month. Freedom from seizures has now been maintained for 2 years.     

Effects of extracellular ATP on bovine lung endothelial and epithelial cell monolayer morphologies, apoptoses, and permeabilities

Pneumonia in cattle is an important disease both economically and in terms of animal welfare. Recent evidence in other species has shown ATP to be an important modulator of inflammation in the lung, where it is released by activated alveolar macrophages and damaged lung cells. Whether ATP serves a similar process during infection in the bovine lung is unknown. In the present study, we examined the effects of ATP treatment on the morphology, apoptosis, and permeability of bovine pulmonary epithelial (BPE) cells and bovine pulmonary microvascular endothelial cells (BPMEC). Monolayers of BPE cells underwent striking morphological changes when exposed to ATP that included separation of the cells. Neither BPE cells nor BPMEC exhibited increased apoptosis in response to ATP. BPE cell and BPMEC monolayers displayed virtually identical increases in permeability when exposed to ATP, with a 50% change occurring within the first hour of exposure. Both cell types contained mRNA for the P2X₇ receptor, a known receptor for ATP. In BPE cells, but not BPMEC, the change in permeability in response to ATP was reversed by the addition of a P2X₇ receptor antagonist. If similar permeability changes occur in vivo, they could be a factor in vascular leakage into lung airspaces during pneumonia.