Higher diet quality in university students is associated with higher academic achievement: a cross-sectional study.

BACKGROUND: Unhealthy diets are typical of university students and the effects may be wider reaching than health. The present study aimed to describe the association between dietary intake and academic achievement in a sample of Australian university students. METHODS: A cross-sectional analysis of data from an online survey of 278 students from the University of Newcastle (UON), Australia [mean (SD) age 26.9 (10.5) years; 70.9% female] was conducted. Dietary intake, in terms of diet quality score [Australian Recommended Food Score (ARFS)], including individual sub-scales, and percentage energy per day from energy-dense nutrient poor (EDNP) foods, including individual sub-groups, was assessed using the validated Australian Eating Survey Food Frequency Questionnaire, and academic achievement was assessed as self-reported grade point average (GPA). The association between GPA and dietary intake was explored using linear regression, with adjustment for socio-demographic and student characteristics. RESULTS: Higher GPA was associated with higher diet quality (ARFS) (ß = 0.02, P = 0.011), higher sub-scale scores for vegetables (ß = 0.03, P = 0.026) and fruit (ß = 0.05, P = 0.029) and with lower percentage energy per day from EDNP foods overall (ß = -0.01, P = 0.047) and also from sweetened drinks (ß = -0.06, P < 0.001). CONCLUSIONS: The results of the present study demonstrate small associations between a healthier dietary intake and higher academic achievement, as well as vice versa. Given that the associations were small, they may not be particularly meaningful. However, this evidence could be used as a motivator for efforts aiming to improve dietary intake among university students.

Effect of hyoscine butylbromide on prostate multiparametric MRI anatomical and functional image quality.

AIM: To evaluate the effect of the spasmolytic agent hyoscine butylbromide (HBB) on the quality of anatomical and functional imaging of the prostate. MATERIALS AND METHODS: One hundred and seventy-three patients were included in this retrospective study. Eighty-seven patients received intravenous HBB prior to scanning (HBB group) and 86 patients did not (non-HBB group). Multiparametric (mp) 3 T magnetic resonance imaging (MRI) was performed using a 32-channel body coil. Two radiologists independently evaluated the image quality of T2-weighted imaging (WI), diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) maps, using a five-point Likert scale. DWI was further assessed for distortion and artefact (four-point Likert scale), and T2WI for the presence of motion artefact or blurring. Dynamic contrast-enhanced (DCE) image quality was assessed by recording the number of corrupt contrast curve data points. RESULTS: T2W image quality in the HBB group was significantly higher than in the non-HBB group (3.63±1.11 versus 2.84±0.899); p<0.001. The HBB group also showed significantly less T2W motion and T2W blur than the non-HBB group (23% and 51.7% versus 53.5% and 83.7%, respectively; p<0.001); however, there was no significant improvement in DWI or ADC image quality, or DWI degree of distortion or artefact. There was a trend towards a lower number of corrupted data points from the contrast curve (2.47±2.44 versus 3.68±2.64), but this did not reach significance (p=0.052). CONCLUSION: Administration of HBB significantly improves the image quality of T2WI images. These results provide evidence for the use of HBB in routine patient preparation prior to prostate mpMRI.

Amniotic fluid volume: Rapid MR-based assessment at 28-32 weeks gestation.

OBJECTIVES: This work evaluates rapid magnetic resonance projection hydrography (PH) based amniotic fluid volume (AFV) estimates against established routine ultrasound single deepest vertical pocket (SDVP) and amniotic fluid index (AFI) measurements, in utero at 28-32 weeks gestation. Manual multi-section planimetry (MSP) based measurement of AFV is used as a proxy reference standard. METHODS: Thirty-five women with a healthy singleton pregnancy (20-41 years) attending routine antenatal ultrasound were recruited. SDVP and AFI were measured using ultrasound, with same day MRI assessing AFV with PH and MSP. The relationships between the respective techniques were assessed using linear regression analysis and Bland-Altman method comparison statistics. RESULTS: When comparing estimated AFV, a highly significant relationship was observed between PH and the reference standard MSP (R(2) = 0.802, p < 0.001). For the US measurements, SDVP measurement related most closely to amniotic fluid volume, (R(2) = 0.470, p < 0.001), with AFI demonstrating a weaker relationship (R(2) = 0.208, p = 0.007). CONCLUSION: This study shows that rapid MRI based PH measurement is a better predictor of AFV, relating more closely to our proxy standard than established US techniques. Although larger validation studies across a range of gestational ages are required this approach could form part of MR fetal assessment, particularly where poly- or oligohydramnios is suspected. KEY POINTS: • MR projection hydrography can be used to estimate amniotic fluid volume. • MR projection hydrography relies on the T2w signal from amniotic fluid. • Amniotic fluid volume (AFV) is more accurately assessed than with ultrasound.

Magnetic resonance elastography: feasibility of liver stiffness measurements in healthy volunteers at 3T.

AIM: To demonstrate the feasibility of obtaining liver stiffness measurements with magnetic resonance elastography (MRE) at 3T in normal healthy volunteers using the same technique that has been successfully applied at 1.5 T. METHODS AND MATERIALS: The study was approved by the local ethics committee and written informed consent was obtained from all volunteers. Eleven volunteers (mean age 35 ± 9 years) with no history of gastrointestinal, hepatobiliary, or cardiovascular disease were recruited. The magnetic resonance imaging (MRI) protocol included a gradient echo-based MRE sequence using a 60 Hz pneumatic excitation. The MRE images were processed using a local frequency estimation inversion algorithm to provide quantitative stiffness maps. Adequate image quality was assessed subjectively by demonstrating the presence of visible propagating waves within the liver parenchyma underlying the driver location. Liver stiffness values were obtained using manually placed regions of interest (ROI) outlining the liver margins on the gradient echo wave images, which were then mapped onto the corresponding stiffness image. The mean stiffness values from two adjacent sections were recorded. RESULTS: Eleven volunteers underwent MRE. The quality of the MRE images was adequate in all the volunteers. The mean liver stiffness for the group was 2.3 ± 0.38 kPa (ranging from 1.7-2.8 kPa). CONCLUSIONS: This preliminary work using MRE at 3T in healthy volunteers demonstrates the feasibility of liver stiffness evaluation at 3T without modification of the approach used at 1.5 T. Adequate image quality and normal MRE values were obtained in all volunteers. The obtained stiffness values were in the range of those reported for healthy volunteers in previous studies at 1.5 T. There was good interobserver reproducibility in the stiffness measurements.

Ultrasmall superparamagnetic iron oxide-enhanced magnetic resonance imaging of abdominal aortic aneurysms--a feasibility study.

OBJECTIVES: Abdominal aortic aneurysms (AAAs), being predominantly atherosclerotic in nature, have underlying inflammatory activity. As it is well established that ultrasmall superparamagnetic iron oxide (USPIO) particles accumulate in the macrophages within atheromatous lesions, USPIO-enhanced magnetic resonance (MR) imaging can be potentially effective in the quantification of the associated inflammatory processes. METHODS: A total of 14 patients underwent USPIO-enhanced MR imaging using a 1.5T-MR system. Quantitative T(2)* and T(2) relaxation time data were acquired before and 36 h after UPSIO infusion at identical AAA locations. The pre- and post-USPIO-infusion relaxation times (T(2)(∗) and T(2)) were quantified and the correlation between pre- and post-USPIO infusion T(2)* and T(2) values was investigated. RESULTS: There was a significant difference between pre- and post-infusion T(2)* and T(2) values (both respective p-values = 0.005). A significant correlation between T(2)* and T(2) values post-USPIO infusion was observed (r = 0.90, p < 0.001), which indicates USPIO uptake by the aortic wall. CONCLUSIONS: Aortic wall inflammation using USPIO-enhanced MR imaging is feasible. Use of quantitative T(2) and T(2)* pulse sequences provides a quantitative method for assessing USPIO uptake by the aortic wall.

Predicting outcome following colorectal cancer surgery using a colorectal biochemical and haematological outcome model (Colorectal BHOM).

AIM: To present a new biochemistry and haematology outcome model which uses a minimum dataset to model outcome following colorectal cancer surgery, a concept previously shown to be feasible with arterial operations. METHOD: Predictive binary logistic regression models (a mortality and morbidity model) were developed for 704 patients who underwent colorectal cancer surgery over a 6-year period in one hospital. The variables measured included 30-day mortality and morbidity. Hosmer-Lemeshow goodness of fit statistics and frequency tables compared the predicted vs the reported number of deaths. Discrimination was quantified using the c-index. RESULTS: There were 573 elective and 131 nonelective interventional cases. The overall mean predicted risk of death was 7.79% (50 patients). The actual number of reported deaths was also 50 patients (χ(2) = 1.331, df = 4, P-value = 0.856; no evidence of lack of fit). For the mortality model, the predictive c-index was = 0.810. The morbidity model had less discriminative power but there was no evidence of lack of fit (χ(2) = 4.198, df = 4, P-value = 0.380, c-index = 0.697). CONCLUSIONS: The Colorectal Biochemistry and Haematology Outcome mortality model suggests good discrimination (c-index > 0.8) and uses only a minimal number of variables. However, it needs to be tested on independent datasets in different geographical locations.

Association between white matter ischaemia and carotid plaque morphology as defined by high-resolution in vivo MRI.

OBJECTIVES AND DESIGN: Both carotid plaque morphology and severity of white matter ischaemia (WMI) have been shown to be independent predictors of stroke risk. This study tests the hypothesis that there is an association between carotid plaque morphology as determined by high-resolution carotid MRI and WMI. MATERIALS AND METHODS: Forty patients (80 arteries) with at least 40% stenosis on screening Doppler ultrasound were recruited and underwent high-resolution axial carotid MRI at 1.5 T. In a blinded manner, plaque characteristics such as lipid core, fibrous cap, intraplaque haemorrhage, lumen area, plaque area, and American Heart Association (AHA) classification were qualitatively and quantitatively evaluated. The severity of WMI was independently quantified using a modified Scheltens score based on standard brain Fluid-Attenuated Inversion Recovery. Linear mixed effect models were used to test if carotid plaque characteristics could independently predict severity of WMI. RESULTS: Hypertension (p=0.005) and previous a history of transient ischaemic attack or stroke (p=0.038) were found to be significant predictors of severity of WMI. After accounting for confounding variables, no significant association was found between the modified Scheltens score and lipid core size (p=0.122), fibrous cap status (p=0.991), intraplaque haemorrhage (p=0.708), plaque area (0.835), lumen area (0.371) or an AHA Type VI complex plaque (p=0.195). CONCLUSIONS: Carotid plaque morphology as defined by MRI does not independently predict severity of WMI.

Temporal dependence of in vivo USPIO-enhanced MRI signal changes in human carotid atheromatous plaques.

INTRODUCTION: Ultrasmall superparamagnetic iron oxide (USPIO)-enhanced MRI has been shown to be a useful modality to image activated macrophages in vivo, which are principally responsible for plaque inflammation. This study determined the optimum imaging time-window to detect maximal signal change post-USPIO infusion using T1-weighted (T1w), T2*-weighted (T2*w) and quantitative T2* (qT2*) imaging. METHODS: Six patients with an asymptomatic carotid stenosis underwent high resolution T1w, T2*w and qT2* MR imaging of their carotid arteries at 1.5 T. Imaging was performed before and at 24, 36, 48, 72 and 96 h after USPIO (Sinerem, Guerbet, France) infusion. Each slice showing atherosclerotic plaque was manually segmented into quadrants and signal changes in each quadrant were fitted to an exponential power function to model the optimum time for post-infusion imaging. RESULTS: The power function determining the mean time to convergence for all patients was 46, 41 and 39 h for the T1w, T2*w and qT2* sequences, respectively. When modelling each patient individually, 90% of the maximum signal intensity change was observed at 36 h for three, four and six patients on T1w, T2*w and qT2*, respectively. The rates of signal change decrease after this period but signal change was still evident up to 96 h. CONCLUSION: This study showed that a suitable imaging window for T1w, T2*w and qT2* signal changes post-USPIO infusion was between 36 and 48 h. Logistically, this would be convenient in bringing patients back for one post-contrast MRI, but validation is required in a larger cohort of patients.

Invasive and non-invasive modalities of imaging carotid stenosis.

Despite recent therapeutic advances, acute ischemic complications of atherosclerosis remain the primary cause of morbidity and mortality in Western countries, with carotid atherosclerotic disease one of the major preventable causes of stroke. As the impact of this disease challenges our healthcare systems, we are becoming aware that factors influencing this disease are more complex than previously realized. In current clinical practice, risk stratification relies primarily on evaluation of the degree of luminal stenosis and patient symptomatology. Adequate investigation and optimal imaging are important factors that affect the quality of a carotid endarterectomy (CEA) service and are fundamental to patient selection. Digital subtraction angiography is still perceived as the most accurate imaging modality for carotid stenosis and historically has been the cornerstone of most of the major CEA trials but concerns regarding potential neurological complications have generated substantial interest in non-invasive modalities, such as contrast-enhanced magnetic resonance angiography. The purpose of this review is to give an overview to the vascular specialist of the current imaging modalities in clinical practice to identify patients with carotid stenosis. Advantages and disadvantages of each technique are outlined. Finally, limitations of assessing luminal stenosis in general are discussed. This article will not cover imaging of carotid atheroma morphology, function and other emerging imaging modalities of assessing plaque risk, which look beyond simple luminal measurements.

Imaging Carotid Atherosclerosis Plaque Ulceration: Comparison of Advanced Imaging Modalities and Recent Developments.

Atherosclerosis remains the leading cause of long-term mortality and morbidity worldwide, despite remarkable advancement in its management. Vulnerable atherosclerotic plaques are principally responsible for thromboembolic events in various arterial territories such as carotid, coronary, and lower limb vessels. Carotid plaque ulceration is one of the key features associated with plaque vulnerability and is considered a notable indicator of previous plaque rupture and possible future cerebrovascular events. Multiple imaging modalities have been used to assess the degree of carotid plaque ulceration for diagnostic and research purposes. Early diagnosis and management of carotid artery disease could prevent further cerebrovascular events. In this review, we highlight the merits and limitations of various imaging techniques for identifying plaque ulceration.

Uterine artery pulsatility and resistivity indices in pregnancy: Comparison of MRI and Doppler US.

OBJECTIVE: The aim of this work was to evaluate whether the uterine arteries (UtA) could be identified and their flow profiles measured during a fetal MRI examination. A comparison was performed against same day sonographic Doppler assessment. METHODS: 35 normal, healthy, singleton pregnancies at 28-32 weeks gestation underwent routine Doppler examination, followed by MRI examination. The resistivity index (RI) and pulsatility index (PI) of the left and right UtA were measured using phase contrast MRI. Bland Altman statistics were used to compare MRI and ultrasound results. RESULTS: Sixty-nine comparable vessels were analysed. Six vessels were excluded due to artefact or technical error. Bland-Altman analysis demonstrated the ultrasound indices were comparable, although systematically lower than the MRI indices; Right UtA RI bias -0.03 (95% limits of agreement (LOA) -0.27 to +0.20), and left UtA RI bias -0.06 (95% LOA -0.26 to +0.14); Right UtA PI bias -0.06 (95% LOA -0.50 to +0.38), Left UtA PI bias -0.11 (95% LOA -0.54 to +0.32). The inter-rater agreement for the MRI derived PI and RI analysis was good. CONCLUSION: This study demonstrates that in the majority of early third trimester pregnancies, the uterine arteries can be identified, and their flow profiles measured using MRI, and that the derived PI and RI values are comparable with Doppler ultrasound values.

Trends in health service use for women in Australia with diabetes.

OBJECTIVE: To describe the health, health service use and use of recommended guidelines for care for women in Australia with diabetes. METHODS: Analysis of survey data 1996-99 from the Australian Longitudinal Study on Women's Health, linked with Medicare data for 1997-2001. Participants were 12,338 mid-age women aged 45-50 years in 1996 (1.9% with diabetes) and 10,421 older women aged 70-75 years at Survey 1 in 1996 (8.1% with diabetes). The outcome measures were number of general practice and specialist visits and use of glycosylated haemoglobin (HbAlc), lipids and microalbuminuria tests. RESULTS: Women with diabetes at Survey 1, and those diagnosed by Survey 2, were more likely to have hypertension, heart disease and eyesight problems, have high rates of polypharmacy (four or more medications: mid age 32%, older 64%) and more consultations with general practitioners and specialists than women without diabetes. During 1997-2001, there was a trend for a greater percentage of women with diabetes to have an HbA1c test at least annually (mid age 44%-52%, older age 46%-58%). Rates of testing microalbuminuria and lipids also increased but were far from conforming to guidelines. Having more frequent consultations with a general practitioner was significantly associated with having all three recommended tests. CONCLUSIONS: There is an increasing use of services by women with diabetes, in part due to an increase in compliance with guidelines for the management of diabetes. IMPLICATIONS: Linked health and administrative data provide a means to monitor health service utilisation, adherence to principles for best practice care and issues of equity in care.

Advances in MRI for the evaluation of carotid atherosclerosis.

Carotid artery atherosclerosis is an important source of mortality and morbidity in the Western world with significant socioeconomic implications. The quest for the early identification of the vulnerable carotid plaque is already in its third decade and traditional measures, such as the sonographic degree of stenosis, are not selective enough to distinguish those who would really benefit from a carotid endarterectomy. MRI of the carotid plaque enables the visualization of plaque composition and specific plaque components that have been linked to a higher risk of subsequent embolic events. Blood suppressed T1 and T2 weighted and proton density-weighted fast spin echo, gradient echo and time-of-flight sequences are typically used to quantify plaque components such as lipid-rich necrotic core, intraplaque haemorrhage, calcification and surface defects including erosion, disruption and ulceration. The purpose of this article is to review the most important recent advances in MRI technology to enable better diagnostic carotid imaging.

Tocainide kinetics in congestive heart failure.

Our subjects were 20 patients with life-threatening or symptomatic ventricular arrhythmias refractory to standard oral antiarrhythmic drugs but responsive to intravenous lidocaine. After evaluation of arrhythmias and treatment with intravenous lidocaine, oral tocainide dosage regimens were based on age, weight, and clinical status. During initial tocainide treatment, six plasma tocainide concentrations were recorded within a single dosing interval in 17 of 20 patients, by which standard kinetic parameters were calculated. Eventual trough steady-state tocainide plasma concentrations were predicted from the derived patient-specific kinetic parameters. Mean daily tocainide dose was 1800 mg (1200 to 2400). Mean daily tocainide doses (milligram per kilogram) did not differ significantly among responders and nonresponders or among patients with or without congestive heart failure. Mean peak and trough plasma concentrations 48 hr after initiation of therapy were 9.8 and 7.5 mcg/ml. Tocainide plasma concentrations did not correlate with responders and nonresponders or identify patients who were developing adverse reactions to tocainide. There were no significant differences in any of the calculated kinetic parameters as a function of response to tocainide or the presence of congestive heart failure, but there was a trend toward smaller volumes of distribution and higher average plasma concentrations at steady state in patients with congestive heart failure. There were no significant kinetic differences among patients with and without congestive heart failure, but a trend toward higher plasma concentrations in patients with congestive heart failure and the small number of patients suggests that further data collection is necessary before dosage recommendations can be made.

Dietary treatment of iron deficiency in women of childbearing age.

BACKGROUND: The Australian Iron Status Advisory Panel advocates dietary intervention as the first treatment option for mild iron deficiency [serum ferritin (SF) = 10-15 microg/L]. However, there appear to be no studies on the efficacy of dietary treatment for iron deficiency. OBJECTIVE: We compared the effects of iron supplementation and of a high-iron diet on serum ferritin (SF) and hemoglobin in iron-deficient women of childbearing age. DESIGN: Forty-four iron-deficient women (SF <15 microg/L or SF = 15-20 microg/L plus serum iron <10 micromol/L and total-iron-binding capacity >68 micromol/L) and 22 iron-replete women (hemoglobin > or =120 g/L and SF >20 microg/L) matched for age and parity categories were enrolled and completed 7-d weighed food records at baseline. The iron-deficient women were randomly allocated to receive iron supplementation (105 mg/d; supplement group) or a high-iron diet (recommended intake of absorbable iron: 2.25 mg/d; diet group) for 12 wk. Hematologic and dietary assessments were repeated at the end of the intervention and again after a 6-mo follow-up. RESULTS: Mean SF in the supplement group increased from 9.0 +/- 3.9 microg/L at baseline to 24.8 +/- 10.0 microg/L after the intervention and remained stable during follow-up (24.2 +/- 9.8 microg/L), whereas the diet group had smaller increases during the intervention (8.9 +/- 3.1 to 11.0 +/- 5.9 microg/L) but continued to improve during follow-up (to 15.2 +/- 9.5 microg/L). Mean hemoglobin tended to improve in both intervention groups, but the change was only significant in the supplement group. CONCLUSIONS: In iron-deficient women of childbearing age, a high-iron diet produced smaller increases in SF than did iron supplementation but resulted in continued improvements in iron status during a 6-mo. follow-up.

The Anti Cancer Council of Victoria FFQ: relative validity of nutrient intakes compared with weighed food records in young to middle-aged women in a study of iron supplementation.

OBJECTIVE: To assess the validity of the Anti Cancer Council of Victoria food frequency questionnaire (ACCVFFQ) relative to seven-day weighed food records (WFRs) in 63 women of child-bearing age. METHOD: 63 women completed WFRs to assess iron intake as part of a study on iron deficiency. These women also completed the ACCVFFQ. Nutrient intakes were computed independently for the WFRs and FFQs. Intakes were compared as group means, by correlation and by quintile classification, adjusting for day-to-day variation in intakes, and for energy intake. Individual differences in results were also examined. RESULTS: The strongest associations between WFR and FFQ results were energy-adjusted, log-transformed and adjusted for day-to-day variability in intake. Correlation coefficients ranged from 0.28 for vitamin A to 0.78 for carbohydrate. Mean intakes from the WFRs and FFQs were within +/- 20% for 21 of 27 nutrients. Poor agreement between FFQs and WFRs for retinol intake was due to the inclusion of liver in two WFRs, an item which is not included in the FFQ. CONCLUSION: The ACCVFFQ performs as well as other FFQs for which validation data are available. The relatively poor measurement of retinol is consistent with other data, and with the limited number of foods in which this nutrient is abundant. IMPLICATIONS: The availability of an optically scannable valid instrument for assessing dietary intake will facilitate epidemiological studies of diet and disease, an area of current research priority.

The effect of minimal exercise on fitness in elderly women after hip surgery.

To determine the effect of minimal exercise on functional fitness following total hip replacement in elderly women, 20 women (13 exercisers, 7 controls) who had undergone unilateral or bilateral hip replacement surgery for primary osteoarthritis were studied. An exercise treadmill test with respiratory gas and blood lactate analyses, and a field test of walking speed on a measured course, were administered before and after a twice weekly exercise programme of three months' duration. Markers of cardiorespiratory fitness, including peak achieved oxygen uptake (VO2) and ventilatory and lactate thresholds were measured. Maximum self-selected walking speed was also measured over a flat course. Peak VO2 increased in the exercise group when compared to baseline (P < 0.05) but did not differ from the control group. The exercise group significantly improved their walking speed by 10.1% compared with non-exercising controls (1.41 vs 1.20 m/sec, P < 0.05), and increased VO2 at lactate threshold. The improvements occurred despite the twice weekly exercise sessions being below the recommended frequency of exercise for improving cardiorespiratory fitness. Minimal exercise in elderly women after hip surgery can substantially improve submaximal exercise capacity, as well as walking speed.

Assessment of ovarian movement on consecutive pelvic MRI examinations in patients with gynaecological malignancies: what is the planning organ-at-risk volume for radiotherapy?

OBJECTIVES: The aims of this study are to assess the extent of ovarian movement on consecutive MRI examinations in patients with gynaecological malignancies and to define potential safety volumes around the ovaries that may avoid ovarian ablation during pelvic irradiation. METHODS: Patients with cervical, vaginal and endometrial cancer who underwent MRI examinations of the pelvis before and during radiotherapy were included in the study. The position of the ovaries was retrospectively determined on two consecutive axial and sagittal T(2) weighted MRI examinations of the pelvis. Ovarian movement was determined in craniocaudal, anteroposterior and mediolateral directions. Safety volumes were calculated by computing elliptical volumes based on the derived 95% and 99% reference intervals. RESULTS: 30 patients with a gynaecological malignancy were included. Both ovaries could be identified on the MRI examinations in all cases. The safety volumes around the ovaries encompassing 95% and 99% of ovarian movement were 11 and 25 cm(3) (95%), and 24 and 54 cm(3) (99%), for the left and right ovary, respectively. CONCLUSION: Adding a safety volume around the ovaries may reduce the high radiation dose to the ovaries. This could potentially avoid ovarian ablation, reducing significant fertility morbidity.

Signal-to-noise ratio increase in carotid atheroma MRI: a comparison of 1.5 and 3 T.

OBJECTIVES: This study reports quantitative comparisons of signal-to-noise ratio (SNR) at 1.5 and 3 T from images of carotid atheroma obtained using a multicontrast, cardiac-gated, blood-suppressed fast spin echo protocol. METHODS: 18 subjects, with carotid atherosclerosis (>30% stenosis) confirmed on ultrasound, were imaged on both 1.5 and 3 T systems using phased-array coils with matched hardware specifications. T(1) weighted (T(1)W), T(2) weighted (T(2)W) and proton density-weighted (PDW) images were acquired with identical scan times. Multiple slices were prescribed to encompass both the carotid bifurcation and the plaque. Image quality was quantified using the SNR and contrast-to-noise ratio (CNR). A phantom experiment was also performed to validate the SNR method and confirm the size of the improvement in SNR. Comparisons of the SNR values from the vessel wall with muscle and plaque/lumen CNR measurements were performed at a patient level. To account for the multiple comparisons a Bonferroni correction was applied. RESULTS: One subject was excluded from the protocol owing to image quality and protocol failure. The mean improvement in SNR in plaque was 1.9, 2.1 and 2.1 in T(1)W, T(2)W and PDW images, respectively. All plaque SNR improvements were statistically significant at the p<0.05 level. The phantom experiment reported an improvement in SNR of 2.4 for PDW images. CONCLUSIONS: Significant gains in SNR can be obtained for carotid atheroma imaging at 3 T compared with 1.5 T. There was also a trend towards increased CNR. However, this was not significant after the application of the Bonferroni correction.

Hypoxia and fetal heart development.

Fetal hearts show a remarkable ability to develop under hypoxic conditions. The metabolic flexibility of fetal hearts allows sustained development under low oxygen conditions. In fact, hypoxia is critical for proper myocardial formation. Particularly, hypoxia inducible factor 1 (HIF-1) and vascular endothelial growth factor play central roles in hypoxia-dependent signaling in fetal heart formation, impacting embryonic outflow track remodeling and coronary vessel growth. Although HIF is not the only gene involved in adaptation to hypoxia, its role places it as a central figure in orchestrating events needed for adaptation to hypoxic stress. Although "normal" hypoxia (lower oxygen tension in the fetus as compared with the adult) is essential in heart formation, further abnormal hypoxia in utero adversely affects cardiogenesis. Prenatal hypoxia alters myocardial structure and causes a decline in cardiac performance. Not only are the effects of hypoxia apparent during the perinatal period, but prolonged hypoxia in utero also causes fetal programming of abnormality in the heart's development. The altered expression pattern of cardioprotective genes such as protein kinase c epsilon, heat shock protein 70, and endothelial nitric oxide synthase, likely predispose the developing heart to increased vulnerability to ischemia and reperfusion injury later in life. The events underlying the long-term changes in gene expression are not clear, but likely involve variation in epigenetic regulation.