Temperature dependence of the(π,0)anomaly in the excitation spectrum of the 2D quantum Heisenberg antiferromagnet

It is well established that in the low-temperature limit, the two-dimensional quantum Heisenberg antiferromagnet on a square lattice (2DQHAFSL) exhibits an anomaly in its spectrum at short-wavelengths on the zone-boundary. In the vicinity of thepoint the pole in the one-magnon response exhibits a downward dispersion, is heavily damped and attenuated, giving way to an isotropic continuum of excitations extending to high energies. The origin of the anomaly and the presence of the continuum are of current theoretical interest, with suggestions focused around the idea that the latter evidences the existence of spinons in a two-dimensional system. Here we present the results of neutron inelastic scattering experiments and Quantum Monte Carlo calculations on the metallo-organic compound Cu(DCOO)D2O (CFTD), an excellent physical realisation of the 2DQHAFSL, designed to investigate how the anomaly atevolves up to finite temperatures. Our data reveal that on warming the anomaly survives the loss of long-range, three-dimensional order, and that it is thus a robust feature of the two-dimensional system. With further increase of temperature the zone-boundary response gradually softens and broadens, washing out theanomaly. This is confirmed by a comparison of our data with the results of finite-temperature Quantum Monte Carlo simulations where the two are found to be in good accord. In the vicinity of the antiferromagnetic zone centre, there was no significant softening of the magnetic excitations over the range of temperatures investigated.

TP1-11 MS-STAT2: a phase 3 trial of high dose simvastatin in secondary progressive multiple sclerosis

Objectives

Disease modifying treatment for secondary progressive multiple sclerosis (SPMS) represents a major unmet need. We outline here the rationale for the MS-STAT2 trial – a phase 3 study of simvastatin in decreasing clinical progression in SPMS. MS-STAT2 will be a landmark study not only for patients with SPMS, but also for the area of drug repurposing and academically led clinical trials as a whole.

Design

Multicentre, double blind, parallel group randomised placebo-controlled trial. It follows the positive outcome from the phase 2 MS-STAT1 trial, which demonstrated a 43% reduction in the annualised rate of brain atrophy compared to placebo.1

Subjects

1180 patients with SPMS with an expanded disability status scale (EDSS) score of 4.0–6.5. Patients need to show evidence of disease progression over the preceding 2 years.

Methods

Subject will be recruited at 28 sites across the UK, and randomised to simvastatin 80 mg or matched placebo and assessed every 6 months over the 3 year trial.

Results

The primary outcome measure is time to 6 month confirmed disability progression, based on change in Expanded Disability Status Scale (EDSS) scores compared to baseline. Secondary outcomes include assessments of cognition, walking, upper limb function and vision. Sub-studies will include advanced imaging outcomes, ocular coherence tomography and fluid biomarkers.

Conclusions

MS-STAT2 is set to be a pivotal trial for SPMS. Recruitment has now commenced and further sites are welcome.

Reference

Chataway J, et al. MS-STAT. Lancet2014;383:2213–21.

A Type 1 Diabetes Genetic Risk Score Predicts Progression of Islet Autoimmunity and Development of Type 1 Diabetes in Individuals at Risk

OBJECTIVE

We tested the ability of a type 1 diabetes (T1D) genetic risk score (GRS) to predict progression of islet autoimmunity and T1D in at-risk individuals.

RESEARCH DESIGN AND METHODS

We studied the 1,244 TrialNet Pathway to Prevention study participants (T1D patients' relatives without diabetes and with one or more positive autoantibodies) who were genotyped with Illumina ImmunoChip (median [range] age at initial autoantibody determination 11.1 years [1.2-51.8], 48% male, 80.5% non-Hispanic white, median follow-up 5.4 years). Of 291 participants with a single positive autoantibody at screening, 157 converted to multiple autoantibody positivity and 55 developed diabetes. Of 953 participants with multiple positive autoantibodies at screening, 419 developed diabetes. We calculated the T1D GRS from 30 T1D-associated single nucleotide polymorphisms. We used multivariable Cox regression models, time-dependent receiver operating characteristic curves, and area under the curve (AUC) measures to evaluate prognostic utility of T1D GRS, age, sex, Diabetes Prevention Trial-Type 1 (DPT-1) Risk Score, positive autoantibody number or type, HLA DR3/DR4-DQ8 status, and race/ethnicity. We used recursive partitioning analyses to identify cut points in continuous variables.

RESULTS

Higher T1D GRS significantly increased the rate of progression to T1D adjusting for DPT-1 Risk Score, age, number of positive autoantibodies, sex, and ethnicity (hazard ratio [HR] 1.29 for a 0.05 increase, 95% CI 1.06-1.6; P = 0.011). Progression to T1D was best predicted by a combined model with GRS, number of positive autoantibodies, DPT-1 Risk Score, and age (7-year time-integrated AUC = 0.79, 5-year AUC = 0.73). Higher GRS was significantly associated with increased progression rate from single to multiple positive autoantibodies after adjusting for age, autoantibody type, ethnicity, and sex (HR 2.27 for GRS >0.295, 95% CI 1.47-3.51; P = 0.0002).

CONCLUSIONS

The T1D GRS independently predicts progression to T1D and improves prediction along T1D stages in autoantibody-positive relatives.

Reversal of apixaban anticoagulation by four-factor prothrombin complex concentrates in healthy subjects: a randomized three-period crossover study

Essentials Prothrombin complex concentrates (PCCs) may reverse the effect of factor Xa (FXa) inhibitors. We conducted an open-label, randomized, placebo-controlled, three-period crossover study in 15 subjects. Both PCCs rapidly reversed apixaban-mediated decreases in mean endogenous thrombin potential. Four-factor PCC administration had no effect on apixaban pharmacokinetics or anti-FXa activity.

SUMMARY

Background Currently, there is no approved reversal agent for direct activated factor Xa (FXa) inhibitors; however, several agents are under investigation, including prothrombin complex concentrates (PCCs). Objective This open-label, randomized, placebo-controlled, three-period crossover study assessed the effect of two four-factor PCCs on apixaban pharmacodynamics and pharmacokinetics in 15 healthy subjects. Methods Subjects received apixaban 10 mg twice daily for 3 days. On day 4, 3 h after apixaban, subjects received a 30-min infusion of 50 IU kg-1 Cofact, Beriplex P/N (Beriplex), or saline. Change in endogenous thrombin potential (ETP), measured with a thrombin generation assay (TGA), was the primary endpoint. Secondary endpoints included changes in other TGA parameters, prothrombin time (PT), International Normalized Ratio (INR), activated partial thromboplastin time, anti-FXa activity, apixaban pharmacokinetics, and safety. Results Apixaban-related changes in ETP and several other pharmacodynamic measures occurred following apixaban administration. Both PCCs reversed apixaban's effect on ETP; the differences in adjusted mean change from pre-PCC baseline to end of infusion were 425 nm min (95% confidence interval [CI] 219.8-630.7 nm min; P < 0.001) for Cofact, and 91 nm min (95% CI - 31.3 to 212.4 nm min; P > 0.05) for Beriplex. Both PCCs returned ETP to pre-apixaban baseline levels 4 h after PCC infusion, versus 45 h for placebo. For both PCCs, mean ETP peaked 21 h after PCC initiation, and then slowly decreased over the following 48 h. Both PCCs reversed apixaban's effect on TGA peak height, PT, and INR. Apixaban pharmacokinetic and anti-FXa profiles were consistent across treatments. Conclusions Cofact and Beriplex reversed apixaban's steady-state effects on several coagulation assessments.

Population Pharmacokinetics, Pharmacodynamics, and Exploratory Exposure-Response Analyses of Apixaban in Subjects Treated for Venous Thromboembolism

Apixaban is approved for treatment of venous thromboembolism (VTE) and prevention of recurrence. Population pharmacokinetics, pharmacokinetics-pharmacodynamics (anti-FXa activity), and exposure-response (binary bleeding and thromboembolic endpoints) of apixaban in VTE treatment subjects were characterized using data from phase I-III studies. Apixaban pharmacokinetics were adequately characterized by a two-compartment model with first-order absorption and elimination. Age, sex, and Asian race had less than 25% impact on exposure, while subjects with severe renal impairment were predicted to have 56% higher exposure than the reference subject (60-year-old non-Asian male weighing 85 kg with creatinine clearance of 100 mL/min). The relationship between apixaban concentration and anti-FXa activity was described by a linear model with a slope estimate of 0.0159 IU/ng. The number of subjects with either a bleeding or thromboembolic event was small, and no statistically significant relationship between apixaban exposure and clinical endpoints could be discerned with a logistic regression analysis.

Tulbaghia violacea Harv. plant extract affects cell wall synthesis in Aspergillus flavus

AIMS

This study investigates the effect that aqueous extracts of Tulbaghia violacea Harv. harbouring plant saponins, phenolics and tannins have on Aspergillus flavus β-(1,3) glucan and chitin synthesis.

METHODS AND RESULTS

Aspergillus flavus was treated with various subinhibitory concentrations of an aqueous T. violacea plant extract and the β-(1,3) glucan and chitin content was determined together with glucan synthase and chitin synthase production respectively.

CONCLUSIONS

The aqueous extract caused a significant decline (P < 0·05) in β-glucan production in A. flavus in a dose-dependent manner when compared to the untreated sample. Further investigations showed a decrease in β-glucan synthase production as the concentration of the plant extract was increased. A significant reduction in total chitin content corresponding to a decrease in chitin synthase production in the presence of the plant extract was also found.

SIGNIFICANCE AND IMPACT OF THE STUDY

The broad spectrum activity and the efficacy of aqueous T. violacea plant extract on both β-glucan and chitin synthesis may limit the potential of the fungus developing resistance towards it and therefore the extract is an ideal candidate for use as a potential antifungal agent.

The accuracy of interpretation of emergency abdominal CT in adult patients who present with non-traumatic abdominal pain: results of a UK national audit

AIM

To evaluate major/minor discrepancy rates for provisional (initial) and addendum (supplementary senior review) emergency computed tomography (CT) reports in patients presenting with non-traumatic abdominal pain.

MATERIALS AND METHODS

Ethical approval for this type of study is not required in the UK. All radiology departments with an approved lead for audit registered with the Royal College of Radiologists were invited to participate in this retrospective audit. The first 50 consecutive patients (25 surgical, 25 non-surgical) who underwent emergency abdominal CT for non-traumatic abdominal pain in 2013 were included. Statistical analyses were performed to identify organisational and report/patient-related variables that might be associated with major discrepancy.

RESULTS

One hundred and nine (58%) of 188 departments supplied data to the study with a total of 4,931 patients (2,568 surgical, 2,363 non-surgical). The audit standard for provisional report major discrepancy was achieved for registrars (target <10%, achieved 4.6%), for on-site consultants (target <5%, achieved 3.1%) and consultant addendum (target <5%, achieved 2.9%). Off-site reporters failed to meet the standard target (<5%, achieved 8.7% overall and 12.7% in surgical patients). The standard for patients coming to harm was not met in the surgical group (target <1%, achieved 1.5%) and was narrowly missed overall (target <1%, achieved 1%).

CONCLUSION

This study should be used to provide impetus to improve aspects of out-of-hours CT reporting. Clear benefits of CT interpretation/review by on-site and more senior (consultant) radiologists have been demonstrated.

Model-based exposure-response analysis of apixaban to quantify bleeding risk in special populations of subjects undergoing orthopedic surgery

Population pharmacokinetic (PK) and exposure-response analyses of apixaban were performed using data from phase I-III studies to predict bleeding risks for patients receiving apixaban 2.5 mg b.i.d. after total knee or hip replacement (TKR, THR) surgery (N = 5,510). Renal function, age, gender, and body weight impacted apixaban exposure. Bleeding risk increased as a function of exposure. Predicted bleeding frequencies for TKR and THR populations at risk for high apixaban exposure (female, age > 75 years, calculated creatinine clearance (cCrCL) < 30 ml/min, body weight < 50 kg) (6.85 and 10.3%, respectively) were comparable to the reference population (male/female, age 65-75 years, cCrCL ≥ 80 ml/min, body weight 65-85 kg) (6.18 and 9.32%, respectively). A 100% increase in apixaban exposure is expected to raise bleeding frequencies to 7.25% (TKR) and 10.9% (THR), whereas a 200% increase would raise them to 8.49 and 12.7%. Coexistence of combined patient risk factors or doubling of exposure is not likely to result in a substantial, clinically relevant increase in bleeding risk with 2.5 mg b.i.d. apixaban.

Multispinon continua at zero and finite temperature in a near-ideal Heisenberg chain

The space-and time-dependent response of many-body quantum systems is the most informative aspect of their emergent behavior. The dynamical structure factor, experimentally measurable using neutron scattering, can map this response in wave vector and energy with great detail, allowing theories to be quantitatively tested to high accuracy. Here, we present a comparison between neutron scattering measurements on the one-dimensional spin-1/2 Heisenberg antiferromagnet KCuF3, and recent state-of-the-art theoretical methods based on integrability and density matrix renormalization group simulations. The unprecedented quantitative agreement shows that precise descriptions of strongly correlated states at all distance, time, and temperature scales are now possible, and highlights the need to apply these novel techniques to other problems in low-dimensional magnetism.

Neutron diffraction study of the non-Fermi liquid compound CeNiGa₂: magnetic behaviour as a function of pressure and temperature

The magnetic symmetry and structure of the non-Fermi liquid heavy fermion compound CeNiGa2 has been determined by neutron powder diffraction. The orthorhombic CeNiGa2 compound orders antiferromagnetically below 4.4(2) K at ambient pressure with a magnetic moment magnitude of μCe = 0.80(4) μB for moments aligned along the c-axis. The magnetic (Shubnikov) space group is C2cm'm'm. The nature of the magnetic order of CeNiGa2 is further elucidated by neutron diffraction at elevated pressures up to 4.5 kbar, allowing for the confirmation of a critical pressure PC of about 4.2(2) kbar above which the magnetic moment ordering is suppressed.

Staging cancer of the uterus: a national audit of MRI accuracy

AIM

To report the results of a nationwide audit of the accuracy of magnetic resonance imaging (MRI) staging in uterine body cancer when staging myometrial invasion, cervical extension, and lymph node spread.

MATERIALS AND METHODS

All UK radiology departments were invited to participate using a web-based tool for submitting anonymized data for a 12 month period. MRI staging was compared with histopathological staging using target accuracies of 85, 86, and 70% respectively.

RESULTS

Of the departments performing MRI staging of endometrial cancer, 37/87 departments contributed. Targets for MRI staging were achieved for two of the three standards nationally with diagnostic accuracy for depth of myometrial invasion, 82%; for cervical extension, 90%; and for pelvic nodal involvement, 94%; the latter two being well above the targets. However, only 13/37 (35%) of individual centres met the target for assessing depth of myometrial invasion, 31/36 (86%) for cervical extension and 31/34 (91%) for pelvic nodal involvement. Statistical analysis demonstrated no significant difference for the use of intravenous contrast medium, but did show some evidence of increasing accuracy in assessment of depth of myometrial invasion with increasing caseload.

CONCLUSION

Overall performance in the UK was good, with only the target for assessment of depth of myometrial invasion not being met. Inter-departmental variation was seen. One factor that may improve performance in assessment of myometrial invasion is a higher caseload. No other clear factor to improve performance were identified.

Memory complaints and increased rates of brain atrophy: risk factors for mild cognitive impairment and Alzheimer's disease

AIM

To determine rates of cerebral atrophy in individuals with symptoms of memory loss but no objective cognitive impairment (SNCI) and their association with future cognitive decline.

METHODS

Thirty-two SNCI subjects, 16 with mild cognitive impairment (MCI) and 27 control subjects had clinical assessment and magnetic resonance imaging at baseline and 1 year later. Rates of whole brain atrophy (WBA), hippocampal atrophy (HA) and ventricular enlargement (VE) were measured. Our outcome was clinical diagnosis at 2 years after entry into the study.

RESULTS

The MCI group had greater rates of WBA, HA and VE than both controls and SNCI subjects. As a group SNCI subjects did not have significantly greater rates of atrophy than the controls. However, SNCI subjects who progressed to MCI or dementia had increased rates of atrophy compared with those who remained stable.

DISCUSSION

Individuals with memory complaints but no objective memory deficits, who progress to MCI or dementia, have increased rates of cerebral atrophy.

Direct observation of paramagnons in palladium

We report an inelastic neutron scattering study of the spin fluctuations in the nearly ferromagnetic element palladium. Dispersive over-damped collective magnetic excitations or "paramagnons" are observed up to 128 meV. We analyze our results in terms of a Moriya-Lonzarich-type spin-fluctuation model and estimate the contribution of the spin fluctuations to the low-temperature heat capacity. In spite of the paramagnon excitations being relatively strong, their relaxation rates are large. This leads to a small contribution to the low-temperature electronic specific heat.

Onset and progression of pathologic atrophy in Huntington disease: a longitudinal MR imaging study

BACKGROUND AND PURPOSE

Longitudinal MR imaging measures provide an opportunity to track progression in HD before the emergence of clinical symptoms. This may prove useful in assessing disease-modifying treatments. We investigated how caudate and global volumes change as HD progresses from premanifest to early disease.

MATERIALS AND METHODS

Forty HD gene-positive individuals and 19 controls underwent serial volumetric MR imaging (baseline, 12 and 27 months; 2 or 3 scans per person). At baseline, 3 patients with HD were premanifest but developed overt motor features during the study, and 37 had early HD. All had dates of motor onset recorded. Caudates, lateral ventricles, and TIVs were measured using semiautomated procedures. Linear mixed models were used to investigate differences between HD and controls in relation to motor onset, controlling for TIV, sex, and age.

RESULTS

Extrapolating backwards in time, we found that differences in caudate and ventricular volumes between patients with HD and controls were evident 14 and 5 years, respectively, before motor onset (P < .05). At onset, caudate volume was 2.58 mL smaller than that in controls (P < .0001); ventricular volume was 9.27 mL larger (P < .0001). HD caudate atrophy rates were linear, showed low variability between subjects, and were approximately 10-fold higher than those in controls (P < .001). HD ventricular enlargement rates were variable between subjects, were approximately 4-fold higher than those in controls at onset (P < .001), and accelerated with disease duration (P = .02).

CONCLUSIONS

We provide evidence of acceleration of global atrophy in HD with disproportionate caudate involvement. Both caudate and global measures may be of use as early markers of HD pathology.

Acceleration of cortical thinning in familial Alzheimer's disease

BACKGROUND

MRI in presymptomatic autosomal dominant Alzheimer's disease mutation carriers (MC) provides an opportunity to detect changes that pre-date symptoms or clinical diagnosis. We used automated cortical thickness (CTh) measurement to compare the grey matter of such a group with cognitively normal controls.

METHODS

9 presymptomatic mutation carriers (4 PSEN1, 5 APP) and 25 healthy, age and sex-matched controls underwent longitudinal volumetric MRI brain imaging. CTh measurement was performed across the whole brain using a validated, automated technique. Four regions of interest (ROI) (entorhinal cortex (ERC), parahippocampal gyrus (PHG), posterior cingulate cortex and precuneus) and two control regions (paracentral and pericalcarine) were selected on the basis of imaging data in existing Alzheimer's disease (AD) literature. Linear mixed models were used to describe normal ageing in controls and the extent to which mean CTh in cases differed from controls according to time since clinical diagnosis, adjusting for normal ageing.

RESULTS

An accelerating decline in CTh was observed across all ROI in the MC group. No such decline was demonstrated in the control regions for the MC group. Relative to controls, and adjusting for normal ageing, there was evidence (p=0.05, one-sided test) of lower CTh in the posterior cingulate up to 1.8 years prior to diagnosis and in the precuneus up to 4.1 years prior to diagnosis in the MC group.

DISCUSSION

Automated CTh analysis is a relatively practical, rapid and effective technique for assessing subtle structural change in AD. There is evidence that cortical thickness is reduced in mutation carriers a number of years prior to clinical diagnosis.

Emergence of coherent magnetic excitations in the high temperature underdoped La2-xSrxCuO4 superconductor at low temperatures

We use inelastic neutron scattering to measure the magnetic excitations in underdoped La2-xSrxCuO4 (x=0.085, T_{c}=22 K) for large energy (5<E<200 meV) and temperature (5<T<300 K) ranges. At low T, the response is highly structured in E and q, with peaks in the local susceptibility at 15 and 50 meV and a four-peaked structure in q for E approximately 185 meV. Raising T from 30 K greater, similarT_{c} to 300 K causes the structure in chi;{''}(q,omega) present for E<70 meV to disappear. It is replaced with a strongly damped response. We attribute this change to the disappearance of the pseudogap with increasing temperature.

The synthesis and anticancer activity of selected diketopiperazines

Six selected diketopiperazines, cyclo(Gly-Val), cyclo(Gly-D-Val), cyclo(Gly-Leu), cyclo(Gly-Ile), cyclo(Phe-Cys) and cyclo(Tyr-Cys), were synthesized via various synthetic routes. Their potential to inhibit cancer cell growth in HT-29, HeLa and MCF-7 cells was determined. Cyclo(Tyr-Cys) caused the greatest inhibition in cervical carcinoma cells with near equivalent activity against HT-29 and MCF-7 cells. The other cyclic dipeptides tested were effective in the inhibition of colon, cervical and breast carcinoma cells, respectively, but the percentage inhibition was lower than for cyclo(Tyr-Cys).

Tracing coalbed natural gas-coproduced water using stable isotopes of carbon

Recovery of hydrocarbons commonly is associated with coproduction of water. This water may be put to beneficial use or may be reinjected into subsurface aquifers. In either case, it would be helpful to establish a fingerprint for that coproduced water so that it may be tracked following discharge on the surface or reintroduction to geologic reservoirs. This study explores the potential of using delta(13)C of dissolved inorganic carbon (DIC) of coalbed natural gas (CBNG)-coproduced water as a fingerprint of its origin and to trace its fate once it is disposed on the surface. Our initial results for water samples coproduced with CBNG from the Powder River Basin show that this water has strongly positive delta(13)C(DIC) (12 per thousand to 22 per thousand) that is readily distinguished from the negative delta(13)C of most surface and ground water (-8 per thousand to -11 per thousand). Furthermore, the DIC concentrations in coproduced water samples are also high (more than 100 mg C/L) compared to the 20 to 50 mg C/L in ambient surface and ground water of the region. The distinctively high delta(13)C and DIC concentrations allow us to identify surface and ground water that have incorporated CBNG-coproduced water. Accordingly, we suggest that the delta(13)C(DIC) and DIC concentrations of water can be used for long-term monitoring of infiltration of CBNG-coproduced water into ground water and streams. Our results also show that the delta(13)C(DIC) of CBNG-coproduced water from two different coal zones are distinct leading to the possibility of using delta(13)C(DIC) to distinguish water produced from different coal zones.

Mesoscopic Phase Coherence in a Quantum Spin Fluid

Mesoscopic quantum phase coherence is important because it improves the prospects for handling quantum degrees of freedom in technology. Here we show that the development of such coherence can be monitored using magnetic neutron scattering from a one-dimensional spin chain of an oxide of nickel (Y2BaNiO5), a quantum spin fluid in which no classical static magnetic order is present. In the cleanest samples, the quantum coherence length is 20 nanometers, which is almost an order of magnitude larger than the classical antiferromagnetic correlation length of 3 nanometers. We also demonstrate that the coherence length can be modified by static and thermally activated defects in a quantitatively predictable manner.

Combined coronary artery bypass grafting and phaeochromocytoma excision

We report two patients who had successful combined coronary artery bypass grafting and excision of phaeochromocytoma. These cases represent the first reports of combined coronary artery bypass grafting and laparoscopic adrenalectomy for phaeochromocytoma and of combined coronary artery bypass grafting and excision of extra-adrenal phaeochromocytoma. With careful peri- and intra-operative management, especially in regard to haemostasis, combined operations for coronary artery disease and phaeochromocytoma are both feasible and safe.

Disappearance of antiferromagnetic spin excitations in overdoped La2-xSrxCuO4

Magnetic excitations for energies up to approximately 100 meV are studied for overdoped La(2-x)Sr(x)CuO(4) with x=0.25 and 0.30, using time-of-flight neutron spectroscopy. Comparison of spectra integrated over the width of an antiferromagnetic Brillouin zone demonstrates that the magnetic scattering at intermediate energies, 20 <or= omega <or= 100 meV, progressively decreases with overdoping. This strongly suggests that the magnetism is not related to Fermi surface nesting, but rather is associated with a decreasing volume fraction of (probably fluctuating) antiferromagnetic bubbles.

Magnetization transfer ratio in Alzheimer disease: comparison with volumetric measurements

BACKGROUND AND PURPOSE

Alzheimer disease (AD) is accompanied by macroscopic atrophy on volumetric MR imaging. A few studies have also demonstrated reduction in magnetization transfer ratio (MTR), suggesting microstructural changes in remaining brain tissue. This study assessed the value of measuring MTR in addition to volumetric MR in differentiating patients with AD from control subjects.

MATERIALS AND METHODS

Volumetric T1-weighted images and 3D MTR maps were obtained from 18 patients with AD and 18 age-matched control subjects. Whole-brain (WB) and total hippocampal (Hc) volumes were measured using semiautomated techniques and adjusted for total intracranial volume. Mean MTR was obtained for WB and in the Hc region. Histogram analysis was performed for WB MTR. Among patients, associations between volumetric and MTR parameters and the Mini-Mental State Examination (MMSE) were explored.

RESULTS

Patients with AD had significantly reduced WB volume (P<.0001) and mean WB MTR (P=.002) and Hc volume (P<.0001) and Hc mean MTR (P<.0001) compared with control subjects. Histogram analysis of WB MTR revealed significant reduction in the 25th percentile point in patients with AD (P=.03). Both WB volume and mean MTR were independently associated with case-control status after adjusting for the other using linear regression models. However, measuring Hc mean MTR added no statistically significant discriminatory value over and above Hc volume measurement alone. Of all MR imaging parameters, only WB volume was significantly correlated with MMSE (r=0.47, P=.048).

CONCLUSIONS

This study demonstrates the independent reduction of WB volume and mean MTR in AD. This suggests that the 2 parameters reflect complementary aspects of the AD pathologic lesion at macrostructural and microstructural levels.