Comparison of In Vivo and Ex Vivo MRI of the Human Hippocampal Formation in the Same Subjects.

Multiple techniques for quantification of hippocampal subfields from in vivo MRI have been proposed. Linking in vivo MRI to the underlying histology can help validate and improve these techniques. High-resolution ex vivo MRI can provide an intermediate modality to map information between these very different imaging modalities. This article evaluates the ability to match information between in vivo and ex vivo MRI in the same subjects. We perform rigid and deformable registration on 10 pairs of in vivo (3 T, 0.4 × 0.4 × 2.6 mm3) and ex vivo (9.4 T, 0.2 × 0.2 × 0.2 mm3) scans, and describe differences in MRI appearance between these modalities qualitatively and quantitatively. The feasibility of using this dataset to validate in vivo segmentation is evaluated by applying an automatic hippocampal subfield segmentation technique (ASHS) to in vivo scans and comparing SRLM (stratum/radiatum/lacunosum/moleculare) surface to manual tracing on corresponding ex vivo scans (and in 2 cases, histology). Regional increases in thickness are detected in ex vivo scans adjacent to the ventricles and were not related to scanner, resolution differences, or susceptibility artefacts. Satisfactory in vivo/ex vivo registration and subvoxel accuracy of ASHS segmentation of hippocampal SRLM demonstrate the feasibility of using this dataset for validation, and potentially, improvement of in vivo segmentation methods.

Lactate detection in inducible and orthotopic Her2/neu mammary gland tumours in mouse models.

This study compared the steady state concentration of lactate in an inducible Her2/nue transgenic breast cancer mouse model and in tumours from the same Her2/neu model grown orthotopically. In vivo lactate was detected by MRS using the Hadamard encoded selective multiple quantum coherence pulse sequence (HadSelMQC) recently developed by our laboratory. A lower lactate signal was observed in the inducible tumours compared to orthotopic tumours in vivo, while ex vivo analysis of perchloric acid extracts revealed similar amounts of this metabolite in both models. Histological staining of mammary tumour specimens showed a much higher level of fat tissue in inducible tumours compared to the orthotopic model. Phantom studies with [3-(13) C] lactate indicated that a lipid environment could significantly reduce the T2 of lactate and impede its detection. The transgenic inducible model for breast cancer not only better recapitulated the biological aspects of the human disease but also provided additional characteristics related to in vivo detection of lactate that are not available in orthotopic or xenograft models. This study suggests that the level of lactate measured by the HadSelMQC pulse sequence may be underestimated in human patients in the presence of high lipid levels that are typically encountered in the breast.

Apparent diffusion coefficient reveals gray and white matter disease, and T2 mapping detects white matter disease in the brain in feline alpha-mannosidosis.

BACKGROUND AND PURPOSE: Methods to locate and identify brain pathology are critical for monitoring disease progression and for evaluating the efficacy of therapeutic intervention. The purpose of this study was to detect cell swelling, abnormal myelin, and astrogliosis in the feline model of the lysosomal storage disease alpha-mannosidosis (AMD) by using diffusion and T2 mapping. MATERIALS AND METHODS: Average apparent diffusion coefficient (ADC(av)) and T2 were measured by imaging the brains of five 16-week-old cats with feline AMD on a 4.7T magnet. ADC(av) and T2 data from affected cats were compared with data from age-matched normal cats. Brains were collected from both affected and normal cats following imaging, and histology was compared with quantitative imaging data. RESULTS: Gray matter from AMD cats demonstrated a 13%-15% decrease in ADC(av) compared with that in normal cats. White matter from AMD cats exhibited an 11%-16% decrease in ADC(av) and a 5%-12% increase in T2 values compared with those in normal control cats. Histologic evidence of neuronal and glial swelling, abnormal myelin, and astrogliosis was consistent with changes in ADC(av) and T2. CONCLUSION: ADC(av) and T2 data can be used to quantify differences in the gray and white matter in the feline AMD brain and may serve as surrogate markers of neuronal swelling, abnormal myelin, and astrogliosis associated with this disease. These studies may be helpful in assessing the efficacy of experimental therapies for central nervous system disease associated with lysosomal storage diseases.

T1-weighted cine FLASH is superior to IR imaging of post-infarction myocardial viability at 4.7T.

PURPOSE: Data are unavailable for rational selection of pulse sequences to assess postinfarction myocardial viability in rodents at high field strength. We implemented a widely used clinical inversion recovery (IR) sequence at 4.7T and compared the results to a heavily T1-weighted cine FLASH sequence (T1-CF) for assessment of infarction size. MATERIALS AND METHODS: Eleven infarcted rats were examined within 24 h of infarction after injection of Gadophrin-3 contrast agent. Images were acquired using both pulse sequences and a standard cine (SC) sequence. Estimates of infarct size were compared to TTC. Global LV function was compared between the T1-CF and SC sequences. RESULTS: SNR, relative SNR, and CNR for the infarcted and normal myocardium were significantly greater for the IR sequence. Infarction size was overestimated by both sequences, but correlated highly and showed very close agreement with TTC. Global function revealed no significant differences between T1-CF and SC. CONCLUSION: Both IR and T1-CF produced reliable results for assessment of infarction size at 4.7T. While the IR sequence delivers better overall SNR and CNR, the T1-CF allows concomitant assessment of global cardiac function with a much shorter acquisition time.

In vivo and ex vivo MRI detection of localized and disseminated neural stem cell grafts in the mouse brain.

The application of stem cells as delivery vehicles opens up the opportunity for targeting therapeutic proteins to the damaged or degenerating central nervous system. Neural stem cell (NSC) lines have been shown to engraft, differentiate and correct certain central nervous system diseases. The present study was performed to test the ability of magnetic resonance imaging (MRI) in detecting transplanted NSCs under conditions of limited migration in the normal adult mouse brain versus widespread migration when the cells are transplanted neonatally. The C17.2 NSC line was labeled in vitro with superparamagnetic iron oxide (SPIO) particles and the labeled cells were implanted intracranially. Serial in vivo gradient echo MR imaging was performed using a 4.7 T horizontal bore magnet. High resolution ex vivo images of the isolated brains were performed at 9.4 T, and the presence of iron was correlated with Prussian blue staining in histological sections. Adult animals injected with SPIO-labeled stem cells exhibited hypointense regions near the injection site that were observed up to 32 days after injection. In neonatally transplanted animals, MR signal intensity from transplanted NSCs was not apparent in in vivo imaging but ex vivo MR images revealed small hypointense regions throughout the brain including the olfactory bulbs, cortex and the cerebellum, reflecting the wide distribution of the engrafted cells. These regions were correlated with Prussian blue staining, which confirmed the presence of SPIO particles inside the engrafted cells. We have shown that MRI is capable of differentiating localized and widespread engraftment of C17.2 stem cells in the central nervous system.

[Comparison of homogenous strain-analysis with wall thickening for the MR tomographic assessment of regional myocardial function]. / Homogene Strain-Analyse im Vergleich zur Wanddickenzunahme für die MR-tomographische Beurteilung der regionalen Myokardfunktion.

PURPOSE: To compare strain analysis and wall thickening (WT) analysis in differentiating the infarcted, adjacent, and remote zones in a rat model of myocardial infarction (MI). MATERIAL AND METHODS: Three normal (NL) and ten rats subjected to myocardial infarction were imaged on a 4.7T scanner. Gradient-echo and SPAMM-tagged cine images were acquired at three short axis levels of the left ventricle (LV). A homogenous strain analysis (principal strains lambda1 and lambda2, displacement D, angle beta) and a WT-analysis (mm- and %-thickening) were performed in all slices demonstrating MI. Regional function was compared between infarcted rats (infarcted, adjacent and remote zone) and corresponding regions in the NL rats. Additional segmental analysis was performed in the NL rats for the anterior, lateral, inferior and septal wall. RESULTS: In the NL rats, lambda (1) (greatest radial thickening) was greatest in the lateral and anterior wall. WT-analysis showed a pattern of function similar to lambda1, however, regional differences using WT-analysis were not significant. lambda (2) (greatest circumferential shortening) was most negative in the anterior wall. D was greatest in the lateral and inferior wall. The angle beta was radially directed in all segments. In the infarcted rats, both strain and WT-analyses revealed significant impairment in function in the infarcted and adjacent zones as compared to NL (p < 0.001). However, only the strain analysis (lambda1, lambda2, p < 0.001) detected significant remote myocardial dysfunction. Myocardial function differed significantly between the infarcted and adjacent and between the infarcted and remote regions. Strain analysis (lambda2, D, beta, p < 0.001) also identified significant functional differences between the adjacent and remote zones, however, no statistically significant differences were found using WT-analysis. CONCLUSION: Strain analysis is superior to WT-analysis in detecting regional functional variations in NL rats and in discriminating function in the infarcted, adjacent and remote zones post MI.

Quantitative assessment of regional myocardial function in a rat model of myocardial infarction using tagged MRI.

We characterized global and regional left ventricular (LV) function during post myocardium infarction (MI) remodeling in rats, which has been incompletely described by previous MRI studies. To assess regional wall motion, four groups of infarcted animals corresponding to 1-2, 3-4, 6-8 and 9-12 weeks post-MI respectively were imaged using a fast gradient echo sequence with a 2D spatial modulation of magnetization (SPAMM) tagging preparation. An additional group was serially imaged (1-2 and 6-7 weeks post-MI) to assess the global function. Regional and global functional parameters of infarcted rats were compared to non-infarcted normal rats. Compared to normal rats, a decrease in ejection fraction (70 +/-7 vs. 40 +/- 8%, p<0.05) was observed in rats with MI. Maximal and minimal principal stretches (lambda1, lambda2) and strains (E1, E2), principal angle (beta) and displacement varied regionally in normal rats but deviated significantly from the normal values in rats with MI particularly in the infarcted and adjacent zones. Not only was strain magnitude reduced segmentally post-MI, but strain direction became more circumferentially oriented, particularly in rats with larger infarctions. We report the first regional myocardial strain values in normal and infarcted rats. These results parallel findings in humans, and provide a unique tool to examine regional mechanical influences on the remodeling process.

Real-time detection of 13C NMR labeling kinetics in perfused EMT6 mouse mammary tumor cells and betaHC9 mouse insulinomas.

A method was developed for obtaining high signal-to-noise 13C NMR spectra of intracellular compounds in metabolically active cultured cells. The method allows TCA cycle labeling kinetics to be determined in real time without significant oxygen transport limitations. Cells were immobilized on the surface of nonporous microcarriers that were either uncoated or coated with polypeptides and used in a 12-cm3 packed bed. The methods were tested with two EMT6 mouse mammary tumor cell lines, one strongly adherent and the other moderately adherent, and a weakly adherent mouse insulinoma line (betaHC9). For both EMT6 lines, NTP and oxygen consumption measurements indicated that the number of cells in the spectrometer ranged from 6 x 10(8) to 1 x 10(9). During infusion of [1-13C]glucose, labeling in C-4 glutamate (indicative of flux into the first half of the TCA cycle) could be detected with 15-min resolution. However, labeling for C-3 and C-2 glutamate (indicative of complete TCA cycle activity) was fivefold lower and difficult to quantify. To increase TCA cycle labeling, cells were infused with medium containing [1,6-13C2]glucose. A 2.5-fold increase was observed in C-4 glutamate labeling and C-3 and C-2 glutamate labeling could be monitored with 30-min resolution. Citrate synthase activity was indirectly detected in real time, as [3,4-13C2]glutamate was formed from [2-13C]oxaloacetate and [2-13C]acetate (of acetyl-CoA). Cell mass levels observed with betaHC9 cells were somewhat lower. However, the 13C S/N was sufficient to allow real-time monitoring of the response of intracellular metabolite labeling to a step change in glucose and a combined glutamine/serum pulse.

Prolonged general anesthesia in MR studies of rats.

RATIONALE AND OBJECTIVES: Magnetic resonance (MR) imaging of laboratory animals may require general anesthesia to minimize body movements over many hours. The anesthetization technique should allow physiologic parameters to remain as close to normal as possible, permit fast recovery, allow safe, repeated use, and avoid attachment of ferrous metal components to the animal. The purpose of this study was to evaluate an anesthetization technique that was developed to meet each of these qualifications. MATERIALS AND METHODS: In 15 rats (280-483-g body weight), general anesthesia was induced (with intramuscular ketamine hydrochloride, xylazine hydrochloride, acepromazine maleate, and atropine), a tail vein catheter was inserted, and preimaging surgical procedures were performed. A face mask was applied, the animal was positioned in a dorsal recumbent position on an acrylic board, and an isothermal heating pad was placed on the ventral aspect of the abdominal wall. The rat, on the board, was then inserted into a trough that contained a custom-built, linearly polarized birdcage head coil and placed in the bore of a 4.7-T horizontal-bore magnet. The face mask was connected to a non-rebreathing gaseous anesthetic system, and anesthesia was maintained with 1.5-2.0 L/min oxygen and 0.25%-1.50% isoflurane. Oxygen saturation, heart rate, and rectal temperature were continuously monitored. RESULTS: The duration of intramuscular anesthesia was 110 minutes +/- 12, and the duration of gaseous anesthesia was 106 minutes +/- 43. The monitoring equipment permitted display of vital signs. CONCLUSION: The method appeared safe, was easy to perform, maintained a stable physiologic state for the parameters monitored, and could be used for repeated anesthesia in the same animal.

Enhancement of hyperglycemia-induced acidification of human melanoma xenografts with inhibitors of respiration and ion transport.

RATIONALE AND OBJECTIVES: The authors performed this study to evaluate the selective acidification of a human melanoma xenograft in mice with severe combined immunodeficiency with the induction of hyperglycemia (mean blood glucose level +/- standard error of the mean, 26 mmol/L +/- 1) and the intraperitoneal administration of metaiodobenzylguanidine (MIBG, 30 mg/kg), alpha-cyano-4-hydroxycinnamate (CNCn, 300 mg/kg), lonidamine (100 mg/kg), cariporide (HOE642, 160 mg/kg), or 4.4'-diisothiocyanatostilbene-2, 2'-disulfonic acid (DIDS, 50 mg/kg). MATERIALS AND METHODS: The intra- and extracellular pH levels of tumor were estimated from the chemical shifts of inorganic phosphate and 3-aminopropylphosphonate, respectively, with phosphorus-31 nuclear magnetic resonance (MR) spectroscopy. The relative level of steady-state lactate was monitored with hydrogen-1 MR spectroscopy. RESULTS: In small tumors (< or = 8.0 mm), hyperglycemia decreased the intra- and extracellular pH levels by less than 0.2. The combination of hyperglycemia and MIBG decreased the intra- and extracellular pH levels by approximately 0.4 and 0.6, respectively, and lowered the beta-nucleoside triphosphate (NTP)/inorganic phosphate (Pi) ratio of tumor and liver by about 60% and 25%, respectively. The combination of hyperglycemia, MIBG, and CNCn produced a transient decrease in the intracellular pH of about 0.6. The combination of hyperglycemia and lonidamine produced a sustained (>3 hours) 0.8-unit decrease in intracellular pH and an 83% and 100% decrease in PCr/P1 and beta-NTP/P1 ratios, respectively. The combination of hyperglycemia. MIBG, cariporide, and DIDS produced a gradual decrease in intra- and extracellular pH by 1.1 and 1.0, respectively. The relative level of steady-state lactate concentration in tumors increased 10% with hyperglycemia alone, about 20% with MIBG plus hyperglycemia, and increased more than twofold when hyperglycemia was combined with MIBG and CNCn administration. CONCLUSION: These preliminary data suggest that hyperglycemia and combinations of respiratory and ion transport inhibitors can be used to selectively acidify tumors and, thereby, sensitize them to hyperthermnia or other pH-sensitive therapeutic modalities.

Efficient design of pulses with trapezoidal magnitude and linear phase response profiles.

A variation of the Shinnar-Le Roux (SLR) method of pulse envelope design that allows for control of the phase of the frequency response profile has been developed. The method makes use of the fact that a knowledge of one of the SLR polynomials in combination with a root inversion pattern for the other polynomial is sufficient to fully define the second polynomial. Optimization of the first polynomial, when cast in this form, remains nonlinear. However, it was demonstrated that the relationship between the SLR polynomials and the frequency response profile may be used to generate an initial guess for the SLR polynomials that is sufficiently accurate to allow for the application of linear optimization techniques in most cases. In practice several pulse envelopes having different root inversion patterns are investigated for each target profile. The resulting collection of pulses allows the user to trade off pulse power for profile accuracy. The proposed technique was used to design a large number of amplitude modulated excitation pulses having trapezoidal magnitude and linear phase frequency response profiles. A few examples of the resulting pulses and their response profiles are presented.

Postoperative pain in children.

An audit project was designed to assess and improve the provision of postoperative analgesia in a children's hospital. Pain assessment for all children and analgesia standards for our institution were introduced prior to data collection. Data were collected on consecutive samples of 316 and 325 children undergoing surgery as inpatients during 10-week periods. Change was initiated between the two periods in response to our findings; our action plan involved education, changes to documentation, the widespread use of diclofenac in children over 2 years of age and recommendations for the prescription of analgesia. The initial prescription of analgesia increased from 95% to 98% (p = 0.019), administration of analgesia to children experiencing bad or severe pain increased from 57% to 71% (p = 0.032) and the number of children experiencing severe pain reduced from 17% to 11% (p = 0.050). Application of audit, by a clinical nurse specialist, enabled us to achieve and demonstrate improvements in the prescription, administration and effectiveness of postoperative analgesia.

A controlled trial of general practitioners' attitudes to patients with schizophrenia.

OBJECTIVE: To examine general practitioners' attitudes to patients with schizophrenia. DESIGN: A random sample of primary care physicians were alternately sent a case vignette of a patient with or without schizophrenia, in an otherwise identical clinical abstract, and asked to indicate their level of agreement with fifteen statements based on it. SUBJECTS AND SETTING: A one-in-five sample of general practitioners who were identified from the Primary Care Services Register of Lothian Health Board. RESULTS: The median score for each statement was compared by the two-tailed Wilcoxon rank sum test. Doctors responding to the vignette of the patient with schizophrenia were significantly less willing to have the patient on their practice list, more likely to refer them to a specialist and more likely to think that they would be violent; whereas they did not think that they would take up any more time than the other patient. These impressions were no different between those who had or had not received work training in psychiatry. CONCLUSIONS: This controlled trial of primary care physicians' attitudes towards patients with schizophrenia amounts to an empirical demonstration of medical discrimination against the sufferers of this and potentially of other long term psychiatric disorders. Psychiatrists and general practitioners should share care in the management of schizophrenia and try to overcome the prejudices against such patients in an attempt to improve their overall clinical care.

Pulses with fixed magnitude and variable phase response profiles.

The Shinnar-Le Roux (SLR) method of pulse envelope design provides for the generation of nearly arbitrary magnitude response profiles with such great efficiency that the pulse envelopes may often be calculated at the time of sequence initiation. A significant limitation of the method is that it provides only limited control of the phase of the response profile. In the current manuscript it is demonstrated that the phase of the response profile can be modulated without affecting the magnitude profile by replacement of some of the roots of the SLR polynomials with one over their complex conjugate. This method allows interactive tailoring of the phase profile to the user's needs. Although the method does not allow for the optimization of arbitrary phase profiles, a variety of pulses, which are of general utility, have been generated. Some of these pulses and their response profiles are presented.