A new local multiscale Fourier analysis for medical imaging

The Stockwell transform (ST), recently developed for geophysics, combines features of the Fourier, Gabor and wavelet transforms; it reveals frequency variation over time or space. This valuable information is obtained by Fourier analysis of a small segment of a signal at a time. Localization of the Fourier spectrum is achieved by filtering the signal with frequency-dependent Gaussian scaling windows. This multi-scale time-frequency analysis provides information about which frequencies occur and more importantly when they occur. Furthermore, the Stockwell domain can be directly inferred from the Fourier domain and vice versa. These features make the ST a potentially effective tool to visualize, analyze, and process medical imaging data. The ST has proven useful in noise reduction and tissue texture analysis. Herein, we focus on the theory and effectiveness of the ST for medical imaging. Its effectiveness and comparison with other linear time-frequency transforms, such as the Gabor and wavelet transforms, are discussed and demonstrated using functional magnetic resonance imaging data.

Is an information booklet for patients leaving hospital helpful and useful?

OBJECTIVE

To determine whether a booklet given to patients being discharged from hospital giving details of their admission and treatment increased their knowledge and recall when reviewed in outpatient clinics.

DESIGN

Patients alternately allocated to receive a booklet or to serve as controls. Assessment by a questionnaire at first attendance at outpatient clinic after discharge. Data were collected over nine months.

SETTING

One general medical and cardiological ward in a large teaching hospital and associated outpatient clinics.

PATIENTS

One hundred and thirty one patients discharged taking at least one drug and scheduled to return to clinic within 12 weeks. Patients stratified by age and by the number of weeks between discharge and outpatient appointment.

INTERVENTION

A booklet was given to 65 patients at discharge from the ward; 66 patients served as controls.

MAIN RESULTS

Of the patients who received the booklet, 56 (86%) knew the names of their drugs, 62 (95%) the frequency of the dose, and 55 (85%) the reasons for taking each drug. The numbers in the control group were 31 (47%), 38 (58%), and 28 (42%) respectively. These differences were highly significant (p less than 0.001). Twenty six (40%) who received the booklet brought all their drugs to clinic compared with 12 (18%) control patients. Appreciably more of the first group of patients than control patients knew the reason they had been in hospital, and more of the first group indicated that they would take the correct action when their prescribed drugs ran out. Most general practitioners thought that the booklet was a good idea, that it was helpful, and that it was better than the existing interim discharge letter.

CONCLUSIONS

Giving patients an information booklet at discharge from hospital appreciably increased the accuracy and thoroughness of their recall of important medical details concerning their illness and its treatment. The booklet was shown to be feasible, helpful in the outpatient clinic, and preferred by most general practitioners.

A semi-automatic technique for measurement of arterial wall from black blood MRI

Black blood magnetic resonance imaging (MRI) has become a popular technique for imaging the artery wall in vivo. Its noninvasiveness and high resolution make it ideal for studying the progression of early atherosclerosis in normal volunteers or asymptomatic patients with mild disease. However, the operator variability inherent in the manual measurement of vessel wall area from MR images hinders the reliable detection of relatively small changes in the artery wall over time. In this paper we present a semi-automatic method for segmenting the inner and outer boundary of the artery wall, and evaluate its operator variability using analysis of variance (ANOVA). In our approach, a discrete dynamic contour is approximately initialized by an operator, deformed to the inner boundary, dilated, and then deformed to the outer boundary. A group of four operators performed repeated measurements on 12 images from normal human subjects using both our semiautomatic technique and a manual approach. Results from the ANOVA indicate that the inter-operator standard error of measurement (SEM) of total wall area decreased from 3.254 mm2 (manual) to 1.293 mm2 (semi-automatic), and the intra-operator SEM decreased from 3.005 mm2 to 0.958 mm2. Operator reliability coefficients increased from less than 69% to more than 91% (inter-operator) and 95% (intra-operator). The minimum detectable change in wall area improved from more than 8.32 mm2 (intra-operator, manual) to less than 3.59 mm2 (inter-operator, semi-automatic), suggesting that it is better to have multiple operators measure wall area with our semi-automatic technique than to have a single operator make repeated measurements manually. Similar improvements in wall thickness and lumen radius measurements were also recorded. Since the semi-automatic technique has effectively ruled out the effect of the operator on these measurements, it may be possible to use such techniques to expand prospective studies of atherogenesis to multiple centers so as to increase access to real patient data without sacrificing reliability.

Fitting of the beat pattern observed in NMR free-induction decay signals of concentrated carbohydrate-water solutions

A series of mathematical functions has been used to fit the proton free-induction decays (FIDs) of concentrated carbohydrate-water samples. For the solid protons, these functions included a sinc function, as well as the Fourier transforms of single and multiple Pake functions multiplied by a Gaussian broadening. The NMR signal from the mobile protons is described by an exponential function. It is found that in most cases the sinc function gives a satisfactory result and provides valuable information about the second moment M(2) and the ratio of solid to mobile protons (f(s) / f(m)). A good indication for using the sinc function is the presence of a beat in the FID. For high temperatures this approach breaks down, and a biexponential fit is more appropriate. If a clear dipolar splitting is observable in the NMR spectra, the Pake function (or a multiple Pake fit) should be used. In this case information about M(2) and f(s) / f(m) can also be obtained.

Aortic size and aortic calcification. A necropsy Study

Measurements of aortic length and circumference in 336 post-mortem specimens confirm earlier, neglected observations on the progressive increase in aortic size which occurs with advancing years. The increase is not related to atherosclerosis , or to hypertension and seems to be part of a true ageing process. The value of measurement of aortic size in body age determination merits exploration by forensic pathologists. Aortic calcification is found in raised and complicated atherosclerotic plaques and its prevalence and severity closely follows the accepted pattern of plaque severity, occurring earlier and more severely in men, in the abdominal aorta and in patients with overt vascular disease in other territories such as patients with cardiac infarcts. No association was found between the amount of calcification and the presence of hypertension, diabetes or neoplasia.

Changes in blood lipids and blood pressure during adolescence

A total of 625 adolescents from three general practices participated in a cross-sectional study of cardiovascular disease risk factors. The girls had higher serum total and high density lipoprotein (HDL) cholesterol concentrations than the boys, while the boys had higher serum triglyceride concentrations. Smoking (equally prevalent in both sexes) was associated with lower HDL cholesterol concentrations, particularly in boys, while in girls use of oral contraceptives was associated with higher total cholesterol and lower HDL cholesterol concentrations showed striking associations with age, height, and sexual maturation in boys, but not in girls. Triglyceride concentrations were associated with age in boys. Systolic blood pressure and serum urate concentrations were higher in boys and rose steeply with age, but no age association was seen for urate concentrations or systolic blood pressure in girls or for diastolic pressures in either sex. Girls, however, had higher diastolic pressures. There was a strong association between urate concentration and the other cardiovascular disease risk factors, especially HDL cholesterol. Adolescence is associated with considerable changes in cardiovascular disease risk factors, and there are striking sex differences in these changes.

Blood pressure-lowering effect of the sodium glucose co-transporter-2 inhibitor ertugliflozin, assessed via ambulatory blood pressure monitoring in patients with type 2 diabetes and hypertension

This study compared the blood pressure-lowering effect of ertugliflozin (1, 5, 25 mg), hydrochlorothiazide (HCTZ; 12.5 mg) and placebo in 194 patients with type 2 diabetes mellitus and hypertension for 4 weeks using ambulatory blood pressure monitoring. Endpoints (change from baseline to week 4) were: 24-h mean systolic blood pressure (SBP; primary); daytime, night-time, seated predose SBP, 24-h, daytime, night-time, seated predose diastolic blood pressure, 24-h urinary glucose excretion and fasting plasma glucose (FPG; secondary). Safety and tolerability were monitored. Significant decreases in placebo-corrected 24-h mean SBP (-3.0 to -4.0 mmHg) were recorded for all doses of ertugliflozin (for HCTZ, this was -3.2 mmHg). Daytime, but not night-time SBP was consistently reduced. Ertugliflozin produced dose-dependent significant decreases in FPG and increases in urinary glucose excretion. No notable changes in plasma renin activity or urinary aldosterone were seen. The most common adverse events were urinary tract infection, genital fungal infection, upper respiratory tract infection and musculoskeletal pain.

Sodium channel slow inactivation as a therapeutic target for myotonia congenita

OBJECTIVE

Patients with myotonia congenita have muscle hyperexcitability due to loss-of-function mutations in the chloride channel in skeletal muscle, which causes spontaneous firing of muscle action potentials (myotonia), producing muscle stiffness. In patients, muscle stiffness lessens with exercise, a change known as the warmup phenomenon. Our goal was to identify the mechanism underlying warmup and to use this information to guide development of novel therapy.

METHODS

To determine the mechanism underlying warmup, we used a recently discovered drug to eliminate muscle contraction, thus allowing prolonged intracellular recording from individual muscle fibers during induction of warmup in a mouse model of myotonia congenita.

RESULTS

Changes in action potentials suggested slow inactivation of sodium channels as an important contributor to warmup. These data suggested that enhancing slow inactivation of sodium channels might offer effective therapy for myotonia. Lacosamide and ranolazine enhance slow inactivation of sodium channels and are approved by the US Food and Drug Administration for other uses in patients. We compared the efficacy of both drugs to mexiletine, a sodium channel blocker currently used to treat myotonia. In vitro studies suggested that both lacosamide and ranolazine were superior to mexiletine. However, in vivo studies in a mouse model of myotonia congenita suggested that side effects could limit the efficacy of lacosamide. Ranolazine produced fewer side effects and was as effective as mexiletine at a dose that produced none of mexiletine's hypoexcitability side effects.

INTERPRETATION

We conclude that ranolazine has excellent therapeutic potential for treatment of patients with myotonia congenita.

Early reporting of myocardial infarction: impact of an experiment in patient education

Many deaths from myocardial infarction occur before medical help is sought. A campaign was mounted in Nottingham ("Nottingham Heartwatch") to encourage early reporting. A total of 13 828 men and women aged 40 and over registered with three general practices were asked to telephone a hospital-based number if they developed chest pain lasting for more than 10 minutes. Patients from study practices reported chest pain earlier after our invitation than they had before and also earlier than patients from control practices. While accepting the advice to call early some patients from the study practices ignored our special number and telephoned their general practitioner. The calls received on the Heartwatch line yielded a lower percentage of definite and probable infarcts than the calls received by the patients' own doctors. The way in which the characteristics of the study practices might have influenced this difference is discussed since it has considerable implications for larger-scale attempts to bring patients with suspected myocardial infarction under medical care at the earliest opportunity.

Acetaminophen hepatotoxicity in vivo is not accompanied by oxidant stress

Hepatotoxic doses of acetaminophen in Fischer 344 rats did not increase biliary efflux of oxidized glutathione. Pretreatment of the animals with bis(2-chloroethyl)-N-nitrosourea inhibited hepatic glutathione reductase by 73 percent but did not potentiate the hepatotoxicity of acetaminophen and did not produce an increase in biliary efflux of oxidized glutathione in response to acetaminophen. Hepatic protein thiol content was not depleted by acetaminophen. A proposed role for oxidant stress mechanisms mediated either by reactive oxygen species or by the direct oxidant action of a reactive metabolite in acetaminophen-induced hepatotoxicity is unsubstantiated and unlikely.

MRI-Based Texture Analysis to Differentiate Sinonasal Squamous Cell Carcinoma from Inverted Papilloma

BACKGROUND AND PURPOSE

Because sinonasal inverted papilloma can harbor squamous cell carcinoma, differentiating these tumors is relevant. The objectives of this study were to determine whether MR imaging-based texture analysis can accurately classify cases of noncoexistent squamous cell carcinoma and inverted papilloma and to compare this classification performance with neuroradiologists' review.

MATERIALS AND METHODS

Adult patients who had inverted papilloma or squamous cell carcinoma resected were eligible (coexistent inverted papilloma and squamous cell carcinoma were excluded). Inclusion required tumor size of >1.5 cm and preoperative MR imaging with axial T1, axial T2, and axial T1 postcontrast sequences. Five well-established texture analysis algorithms were applied to an ROI from the largest tumor cross-section. For a training dataset, machine-learning algorithms were used to identify the most accurate model, and performance was also evaluated in a validation dataset. On the basis of 3 separate blinded reviews of the ROI, isolated tumor, and entire images, 2 neuroradiologists predicted tumor type in consensus.

RESULTS

The inverted papilloma (n = 24) and squamous cell carcinoma (n = 22) cohorts were matched for age and sex, while squamous cell carcinoma tumor volume was larger (P = .001). The best classification model achieved similar accuracies for training (17 squamous cell carcinomas, 16 inverted papillomas) and validation (7 squamous cell carcinomas, 6 inverted papillomas) datasets of 90.9% and 84.6%, respectively (P = .537). For the combined training and validation cohorts, the machine-learning accuracy (89.1%) was better than that of the neuroradiologists' ROI review (56.5%, P = .0004) but not significantly different from the neuroradiologists' review of the tumors (73.9%, P = .060) or entire images (87.0%, P = .748).

CONCLUSIONS

MR imaging-based texture analysis has the potential to differentiate squamous cell carcinoma from inverted papilloma and may, in the future, provide incremental information to the neuroradiologist.

In vivo measurements of multi-component T2 relaxation behaviour in guinea pig brain

Multi-echo Carr-Purcell-Meiboom-Gill (CPMG) imaging sequences were implemented on 1.5 T and 4.0 T imaging systems to test their ability to measure in vivo multi-component T2 relaxation behavior in normal guinea pig brain. The known dependence of accurate T2 measurements on the signal-to-noise ratio (SNR) was explored in vivo by comparing T2 decay data obtained using three methods to increase SNR (improved RF coil design, signal averaging and increased magnetic field strength). Good agreement between T2 values of nickel-doped agarose phantoms was found between imaging and spectroscopic methods. T2 values were determined for gray matter (GM) and white matter (WM) locations from images of guinea pig brain in vivo. T2 measurements of GM were found to be monoexponential at both field strengths. The mean T2 times for GM were 71 ms at 1.5 T, and 53 ms at 4.0T. The highest average SNR was achieved using an improved RF coil at 4.0T. In this case, two peaks were extracted in WM, a "short" T2 peak at approximately 6 ms, and a "medium" T2 peak at approximately 48 ms. T2 values in GM and the major component of WM were significantly decreased at 4.0T compared to 1.5 T. The improved SNR attained with this optimized imaging protocol at 4.0T has allowed for the first time extraction of the myelin-sensitive T2 component of WM in animal brain in vivo.

Renin-aldosterone profiling in hypertension

Renin-aldosterone profiling was used to classify patients with hypertension: 243 patients with essential hypertension were classified by renin-urinary sodium indexing; 107 were reclassified by response to administration of furosemide and intravenous saline; 45 were further classified by response to a low-sodium diet. Arbitrary "normal ranges" were determined in 89, 32, and 38 volunteers, respectively. Patients with low-renin apparently do not have "high-volume" hypertension. Rather, they show a primary renal abnormality in renin secretion and become relatively deficient in angiotensin II and aldosterone when they are subjected to diuresis. They can maintain aldosterone secretion under normal conditions because their adrenal aldosterone receptor is supersensitive to angiotensin II. No evidence of abnormal sympathetic neural activity was found among the renin subgroups. Renin-aldosterone profiling in current clinical practice seems useful mainly in the detection of patients with curable forms of secondary hypertension. Aldosterone/renin ratios may be particularly helpful in diagnosis when obtained after a patient has undergone expansion or contraction of his extracellular fluid volume.

Definition of the rheological glass transition temperature in association with the concept of iso-free-volume

Small deformation dynamic oscillation was used to develop an index of physical significance for the rationalisation of the mechanical properties of high co-solute/biopolymer systems during vitrification. The index is based on the combined framework of Williams-Landel-Ferry equation with the free volume theory and is called the 'rheological glass transition temperature, T(g)' thus differentiating it from the empirical calorimetric T(g) used in thermal analysis. The rheological T(g) is located at the conjunction of two distinct molecular processes, namely: free-volume effects in the glass transition region and the predictions of the reaction-rate theory in the glassy state. The method of reduced variables was used to shift the mechanical spectra of shear moduli to composite curves. The temperature dependence of shift factors for all materials was identical provided that they were normalised at suitably different reference temperatures, which reflect iso-free-volume states. The treatment makes free volume the overriding parameter governing the mechanical relaxation times during vitrification of high co-solute/biopolymer systems regardless of physicochemical characteristics. We believe that potential applications resulting from this fundamental work are numerous for the food and pharmaceutical industries.

Neonatal platelet reactivity and serum thromboxane B2 production in whole blood: the effect of maternal low dose aspirin

OBJECTIVES

Concern has been expressed about possible neonatal side effects after the use of maternal anti-platelet agents in pregnancy, particularly low dose aspirin treatment. We have studied neonatal platelet behaviour using whole blood techniques, and assessed the neonatal effect of the maternal ingestion of 60 mg aspirin daily.

DESIGN

Cross sectional and randomised, double-blind, placebo-controlled.

SETTING

University hospital.

SUBJECTS

1. Eight normal women, studied before conception, and their infants. 2. Twenty-four infants whose mothers had been randomised to receive either 60 mg aspirin daily, or placebo, in double-blind fashion.

METHODS

The Clay Adams Ultra Flo 100 whole blood single platelet counter was employed to measure platelet aggregation in response to various agonists. The platelet release reaction was also measured in whole blood, and serum thromboxane B2 (TxB2) production was measured by radio-immunoassay. Umbilical cord blood samples were obtained at delivery.

RESULTS

1. Neonatal platelet aggregation induced by adrenaline, ADP and platelet activating factor was reduced in comparison with their mothers (P < 0.01), whereas the neonatal platelet release reaction was reduced when stimulated by collagen and U46619 (a thromboxane mimetic) (P < 0.01). Serum TxB2 production was similar in mothers and babies. 2. Neonatal platelet aggregation, release reaction and serum TxB2 production were not significantly reduced in infants exposed to maternal aspirin in comparison with those neonates exposed to maternal placebo. This is in contrast to the effect on maternal platelets.

CONCLUSIONS

Although only a small number of patients were studied, we interpret this as a relative sparing of neonatal platelet reactivity due to the presystemic action of low dose aspirin.

Biochemical changes after hepatic injury from toxic doses of acetaminophen or furosemide

The effects of hepatotoxic doses of acetaminophen and furosemide on the function and composition of hepatic endoplasmic reticulum were compared from 3 to 24 h after administration. Acetaminophen caused a significant decrease in microsomal protein concentration as early as 3 h after its administration, but furosemide did not affect the microsomal protein concentration until 24 h after the dose. Both acetaminophen and furosemide decreased the concentrations of cytochrome P-450 and cytochrome b5 in microsomes, and the activity of microsomal ethylmorphine N-demethylase and aniline hydroxylase. Glucose-6-phosphatase and UDP-glucuronyl transferase were not significantly affected by acetaminophen or furosemide administration, and neither diene conjugation nor hepatic triglycerides were increased. Incorporation of 3H-L-leucine into liver proteins was decreased by 50% after the administration of either acetaminophen or furosemide.

Isothermal and non-isothermal crystallization in amorphous sucrose and lactose at low moisture contents

Differential scanning calorimetry has been used in isothermal and non-isothermal modes to provide information on the crystallization of sucrose and lactose at low water contents. Using approaches previously applied to polymer crystallization an attempt has been made to combine the isothermal and non-isothermal data into a single curve. This is achieved by the use of appropriate shift factors in the time and temperature domains. This was successful for sucrose but not for lactose. It was suggested that this was because lactose crystallizes into multiple forms whereas sucrose crystallizes in a single form.