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In this article, a novel method for measuring the volume of the urinary bladder non-invasively is presented that relies on the principles dictated by Electrical Impedance Tomography (EIT). The electronic prototype responsible for injecting innocuous electrical currents to the lower abdominal region and measuring the developed voltage levels is fully described, as well as the computational models for resolution of the so-called Forward and Inverse Problems in Imaging. The simultaneous multi-tone injection of current provided by a high performance Field Programmable Gate Array (FPGA), combined with impedance estimation by the Discrete Fourier Transform (DFT) constitutes a novelty in Urodynamics with potential to monitor continuously the intravesical volume of patients in a much faster and comfortable way than traditional transurethral catheterization methods. The resolution of the Inverse Problem is performed by the Gauss-Newton method with Laplacian regularization, allowing to obtain a sectional representation of the volume of urine encompassed by the bladder and surrounding body tissues. Experimentation has been carried out with synthetic phantoms and human subjects with results showing a good correlation between the levels of abdominal admittivity acquired by the EIT system and the volume of ingested water.

Implantable devices represent the future of remote medical monitoring and administration of both chemical and physical therapies to the patients. Although some of these devices are already in the market, the security mechanisms deployed inside them to withstand deliberate external influence are still decades away from the robust digital data security schemes employed in modern distributed networks these days. Medical data theft, spoofing, and disclosure pose serious threats that can ultimately lead to individual and social stigmas or even death. In this article, we present a small-form and batteryless implantable device with acquisition channels for biopotential (30-dB gain and 16-Hz bandwidth), arterial pulse oximetry, and temperature (0.12°C accuracy) recordings, suitable for cardiovascular, neuronal, and endocrine parameters assessment. The proposed device is powered by the near-field communication (NFC) interface with an external mobile phone, with a power consumption of 0.9 mW and achieving the full operation for distances close to 1 cm under the skin. In situ encryption of the acquired physiological signals is performed by a lightweight and short-term symmetric-key distribution scheme with data stream hopping, in order to ensure secure data transference over the air between the patient and trusted entities only, complemented by data storage, processing, and recovery through a medical blockchain type of network that involves the main stakeholders inside a medical community.

Ultrasounds (US) are one of the most used imaging techniques in medicine for assessing the physiological and pathological state of soft tissue. Apart from therapeutic applications, most of the interaction of the acoustic beams with tissues occur passively and without substantial modification to the physiology of the latter. However, US can also be used to remotely power implantable devices with sensing capabilities. In this study, we propose small-form devices interfaced with functionalized electrochemical electrodes for the detection of pH and lactate levels, powered by ultrasounds and data transmission through a Frequency Shift Keying (FSK) modulation technique. A custom-made piezoelectric transducer is responsible for converting the acoustic waves into electrical voltage at the device with operational levels as low as 0.5 V (power consumption of 10 μW) obtained from implantation distances of 50 mm inside tissue. This conjugated with the high sensitivity of the developed electrochemical sensors allows to detect and transmit local parameter variations below 0.1 pH (4.2 mV) and 1 mM lactate (70 nA). Potential applications include real-time access to intrabody tissue monitoring post-operatively, with the view of assessing proper soft tissue healing or infection detection by bacteria, as well as tissue cancer screening in structures such as the human breast.

Infection by the parasite of malaria is a serious healthcare problem for populations residing primarily in tropical and subtropical countries. Early detection of the disease is essential to reduce both the mortality rate and spreading of the disease in the infected areas. Current methods for malaria diagnosis still rely on microscopic analysis of blood smears, which is a time-consuming and expensive process, in addition of requiring trained examiners to perform the analysis. In this paper, we introduce a novel fast screening tool for malaria based on a portable blood impedance analyzer. The simultaneous multi-tone injection of current and voltage detection of the device allow reducing the screening time (order of seconds) while enhancing the differences in impedance signal registered among frequencies to increase parasitemia level discrimination. We went further to demonstrate the possibility of directly applying the device on blood samples collected from volunteers to distinguish between infected and non-infected samples. Minimum parasitemia level discriminated was 0.0078% (or, equivalently 390 parasites/μl), which closely approaches the international standard set to 200 parasites/μl. Finally, we also show the frequency dependency of ring-synchronized and unsynchronized blood samples, which can constitute the basis for development of a point-of-care and laboratory-free method to distinguish different stages of malaria infection in economic stagnated communities.

Skin cancer is a medical condition that is becoming more common in many countries as a result of excessive exposure of individuals to sunlight. The ultraviolet range of the electromagnetic radiation is responsible for 90% of the cases involving the development of melanomas. Additional factors like the skin tone and texture can increase the risk of radiation exposure when the water content retained by the skin starts to drop dramatically. In this paper we present a small, batteryless wearable device that combines the computation of sunlight exposure with the measurement of the impedance of the skin and temperature, at any time of the day and independently of the location of the person wearing the sensor. Results have shown a good performance in tracking the ultraviolet index and the variation of impedance for different levels of skin hydration.

Ultrasounds are a proven medical tool to assess some biological processes, including breast cancer screening, fetal development and blood perfusion. However, ultrasounds also have the potential to deliver power and telemetry capabilities to deeply implant devices, surpassing some of the challenges faced by coils or antennas operating inside the human body. In this paper, we present a small-form implantable device activated by ultrasounds that can perform in situ tissue impedance imaging. The goal is to provide a diagnosis tool to evaluate soft tissue healing after surgery, by searching for areas of bacterial infection as the normal conductivity of tissue will be impaired, a phenomena undetected by standard imaging methods. The benefits that can come from this technology are the reduction of the morbidity rate associated with wound infections and recovery time for patients in hospital. The results obtained by the device have already shown a good performance in tracking conductivity perturbations in two-dimensional domains as part of the experimental setup devised for impedance measurements.

Wearable technology has become ubiquitous in recent years due to the miniaturization of circuit electronics and advances in smart materials that can conform to the requirements posed by the human body, behaviour and experience. Sensors of this type are found attached almost to every body segment, capable of delivering signals even in harsh activity scenarios. The reliability and relevance of the physiological data retrieved by wearables have yet to surpass the conventional technologies in the healthcare system today. In this paper we present a small device incorporated inside an headphone set that continuously monitors the ECG, impedance and acceleration of the head. As opposed to most biometric sensors, ECG measurement relies on non-optical methods by capturing the electrical potential around the ear in both sides of the head, whereas impedance monitoring involves AC stimulation instead of DC, the latter commonly involved in skin galvanic response estimation. Signal processing of impedance parameters is performed in situ using a fast variant of the Discrete Fourier Transform in order to save computational resources and power expenditure from a microcontroller equipped with Bluetooth Low Energy. Applications that can benefit from this device include cardiovascular and stress level assessment of individuals for whom an hearable is a requirement for work or leisure.

Ultrasound imaging is a proven diagnostic tool to assess a myriad of physiological and pathological conditions in patients. Throughout the years, ultrasounds have been used as a passive recording modality where the backscattered echo arising from the interaction of the sound waves with the acoustic properties of the biological tissues helps to identify them. Apart from a wide range of therapeutic applications, the acoustic beam has not yet been explored to actuate within the biological environment in an active way. In this paper we present an implantable electronic device to be actuated remotely by ultrasounds with capabilities for measuring several physiological parameters of tissues: pH, temperature, electrolyte concentration and biopotentials. The small factory form device (with no attached batteries) harvests energy from the incoming ultrasound waves and uses it to power the embedded electronics. It operates from voltage levels as low as 0.8 V and consuming a total current of 60 μA (or an average power consumption of 84 μW) in the active mode when deployed at a distance of 3 cm from the active source of ultrasounds in vitro, excited by a sinusoid at 400 kHz with power density of 20 mWcm-2. The sensor can be actuated by a specifically-designed readout device (as detailed in this paper) or using the traditional medical probes for ultrasound imaging. The actual device can present an alternative to surpass the limitations of inductive and RF-powered sensors implanted in soft tissues.

Presents an introductory editorial on the special issue for this issue of the publication which examines the fields of biomedical and health informatics.

Background— Depot medroxyprogesterone acetate (DMPA) inhibits proliferation of ovarian follicles, resulting in anovulation and a decrease in circulating estrogen; the latter action is potentially disadvantageous to cardiovascular health. We therefore investigated the vascular effects of long-term contraceptive DMPA in young women. Methods and Results— Endothelium-dependent (hyperemia-induced flow-mediated dilatation [FMD]) and -independent (glyceryl trinitrate [GTN]) changes in brachial artery area were measured using cardiovascular magnetic resonance in 13 amenorrheic DMPA users (>1 year use; mean age 29±4 years) and in 10 controls (mean age 30±4 years, P =0.25) with regular menstrual cycles after validation of the technique. FMD and GTN responses were measured just before repeat MPA injection and 48 hours later (n=12) in DMPA users and during menstruation and midcycle (n=9) in controls. Serum-estradiol levels (S-estradiol) were measured at both visits. FMD was reduced in DMPA users compared with controls during menstruation (1.1% versus 8.0%, respectively P P P =0.23). Estradiol levels were significantly correlated to FMD ( r =0.43, P Conclusions— Endothelium-dependent arterial function measured by cardiovascular magnetic resonance is impaired in chronic users of DMPA, and hypoestrogenism may be the mechanism of action. DMPA might adversely affect cardiovascular health, and in particular its use in women with cardiovascular disease should be additionally evaluated.

This paper presents an automatic method of correcting non-uniform RF coil response for the classification of body composition using MR imaging. By linear mosaic modelling, the smoothly but non-linearly varying bias field, which modulates tissue intensities within the image, was corrected. The overlapping between adjacent mosaics ensured consistent segmentation of body fat content and the effectiveness of the technique was validated by both phantom and in vivo experiments. Ten whole body composition data sets, each with 39 trans-axial slices, were acquired. Automatic segmentation results using the proposed technique were compared with those from manual delineations. The automatic segmentation method was found to be highly accurate and the mean percentage error between the two methods was less than 1.5%.

Magnetic resonance (MR) perfusion FLASH imaging has been used for assessing coronary artery disease (CAD). Echo-planar MR techniques have advantages in speed and in making MR perfusion imaging results more clinically accessible through parametric maps, but have not been previously assessed. We implemented a spin-echo, echo-planar MR technique and applied it at rest and during adenosine stress in 26 patients with CAD and abnormal thallium single-photon-emission computed tomography (SPECT), and analyzed the results by using a newly developed parametric map analysis of time to peak, peak intensity, and slope of contrast washin. The results were compared with the results of conventional visual analysis of the perfusion cine series. For detecting abnormal coronary territories, MR and SPECT were comparable for sensitivity, specificity, and accuracy (thallium, 70%, 78%, and 73%; MR, 79% 83%, and 80%; P = NS). There was good agreement between thallium and MR during stress (kappa = 0.49), but defects were larger by MR (2.4 vs. 3.1 segments for slope; P < 0.01). Additional segments were detected at rest by MR (58 for slope vs. 25 for thallium), which correlated with areas that became abnormal with stress in the thallium (sensitivity, 100%; specificity, 63%). The parametric maps were easier and faster to interpret than review of the original first-pass series of images (chi2 = 10.8; P < 0.04). The diagnostic performance of echo-planar perfusion MR and SPECT was similar, and combining the results with parametric mapping was useful for interpretation and considerably improved data display for clinical interpretation. MR, however, was faster and yielded images of higher resolution with no radiation burden. In multislice mode, these new MR techniques may have clinical value.

In this phase I clinical study, the new ultrasmall superparamagnetic iron oxide contrast agent, NC100150 Injection (Nycomed AS, Oslo, Norway, a part of Nycomed Amersham), was assessed for first-pass magnetic resonance myocardial perfusion studies and its ability to produce equilibrium signal changes, as a possible indicator of myocardial blood volume. Data were acquired in 18 healthy male volunteers at 0.5 T and 1.5 T. At both field strengths, first-pass studies using T1-weighted sequences were acquired. Long TE spin-echo echoplanar imaging (EPI) was used at 0.5 T and short TE fast low-angle shot (FLASH) imaging at 1.5 T. With both sequences, T1 effects dominated the images for low doses, and time intensity curves potentially suitable for perfusion analysis were generated. At higher doses, T2 and T2* effects were observed. At 1.5 T, these predominantly affected the blood pool signal; however, at 0.5 T the myocardial signal was also involved, reflecting the relative T2 and T2* sensitivity of the spin-echo EPI sequence as a result of the long TE and long readout window, respectively. Equilibrium changes were assessed at both field strengths using T1-weighted FLASH sequences and in addition at 1.5 T using T2*-weighted gradient-echo EPI. With the T1-weighted images at both field strengths, signal changes were observed in all subjects; however, no dose-response relationship could be shown. With the T2*-weighted EPI there was significantly lower signal (P < 0.05) with the 3 and 4 mg/kg doses than with the 2 mg/kg dose. In conclusion, NC100150 Injection is useful for first-pass myocardial perfusion using T1-weighted sequences; however, low doses in combination with short TE sequences are required to minimize sensitivity to T2* effects. Equilibrium signal changes can also be induced in the myocardium. More work is required to optimize the imaging sequences and dose of NC100150 Injection for first-pass studies and also to determine whether the equilibrium signal changes can be used to measure myocardial blood volume changes in ischemic heart disease.

In this Phase I clinical study, a novel ultrasmall superparamagnetic iron oxide contrast agent, NC100150 Injection (Nycomed Imaging, Oslo, Norway, a part of Nycomed Amersham), was used in two-dimensional magnetic resonance coronary angiography (MRCA). Safety and imaging data were acquired from 18 healthy male volunteers at both 0.5 and 1.5 T, before and after the administration of NC100150 Injection. Through-plane and in-plane images of the right coronary artery were analyzed. The postcontrast imaging sequences used prepulses and a high flip angle, to introduce T1 weighting. At 1.5 T (TE 2.6 msec), the through-plane coronary artery signal-to-noise ratio (SNR) (P = 0.04), coronary artery-to-fat signal difference-to-noise ratio (SDNR) (P = 0.001), coronary artery-to-myocardium SDNR (P < 0.001), and coronary artery delineation (P < 0.001) were improved by the administration of NC100150 Injection. For in-plane imaging, coronary artery delineation improved, but there were no significant changes in the SNR and SDNR. At 0.5 T, with the longer TE (6.7 msec) imaging sequence used, there was a reduction in the SNR (P = 0.01), the fat SDNR (through-plane P = 0.02; in-plane P = 0.25), and the coronary artery diameter (P < 0.01 in both imaging planes). There was a trend toward improvement in the myocardial SDNR and coronary artery delineation. In conclusion, NC100150 Injection was given safely to 18 healthy subjects, with no major adverse reactions. Coronary artery delineation was improved in both imaging planes at 1.5 T, with a trend toward improvement at 0.5 T. At 1.5 T, with a short TE imaging sequence, the marked T1 shortening effects of NC100150 Injection were dominant, leading to an improvement in the quantitative parameters for the through-plane images. At 0.5 T, with a longer TE imaging sequence, the T2* effects of the contrast agent played a role in reducing the quantitative image parameters. With further optimization of imaging sequences, to take advantage of the long-lived intravascular T1 shortening effect of NC100150 Injection, further improvements in MRCA will be possible. J. Magn. Reson. Imaging 1999; 9:220–227. © 1999 Wiley-Liss, Inc.

Coronary angiography techniques have been implemented on a 0.5-Tesla scanner with a view to performing coronary artery imaging. Slice-followed, segmented k-space FLASH sequences and interleaved-spiral sequences have been employed with acquisitions under real-time navigator echo control with patient feed back, enabling poor signal-to-noise levels to be overcome by averaging data acquired over multiple, variable-length, reproducible breath holds. Good-quality, millimetre-resolution coronary images were obtained in ten normal subjects with both techniques. The mean percent of data segments or interleaves acquired with the navigator echo within the 5-mm diaphragm acceptance window was 57% [standard deviation (S.D.), 11%; range, 38–85%], and the average image-acquisition times were 123 ± 22 sec and 71 ± 14 sec for segmented FLASH and interleaved-spiral imaging, respectively. In addition to shorter acquisition times, the interleaved-spiral sequence has superior temporal resolution, allowing the acquisition of limited, multislice data sets. However, the sequence is particularly sensitive to the off-resonance effects of residual epicardial fat surrounding the artery and to field nonuniformities, both of which lead to image blurring and, unlike segmented FLASH acquisitions (which are very robust), the spiral data sets generally require postprocessing. Magn Reson Med 41:392–399, 1999. © 1999 Wiley-Liss, Inc.

This paper describes a locally focused magnetic resonance (MR) imaging method for three-dimensional (3D) zonal echoplanar coronary angiography using volume-selective radiofrequency (RF) excitation. Spatially variable resolution was used for delineating coronary arteries and reducing the effect of residual signals caused by the imperfect excitation profile of the RF pulse. The use of variable resolution enabled the derivation of basis functions having different spatial characteristics pertaining to regional object details, and a significantly smaller number of phase-encoded signal measurements was needed for image reconstruction. Based on the relative significance of each required phase-encoding step, real-time phase-encode reordering was used to minimize the effect of respiratory motion during coronary imaging. To eliminate Nyquist ghosting in oblique echoplanar imaging, the echoplanar data acquired during forward and reverse echoes were reconstructed separately and then averaged with spatial registration for improving the signal-to-noise ratio. The technique was evaluated with phantom experiments and right coronary artery images of 11 asymptomatic volunteers using a 0.5 T MR system. A marked improvement in image quality has been achieved despite a 30% reduction in imaging time.

Respiration causes continuous change in cardiac position, which leads to image degradation. Phase-encode reordering methods are often used to reduce these artifacts. An improved method for suppressing motion artifacts by reordering the acquisition of k space has been developed that is less sensitive to change of breathing patterns and bulk movement. We describe the theory behind the new approach and compare its results with those of existing methods by use of a phantom with simulated and actual acquired breathing patterns. The comparison was also made in vivo; cardiac scans were performed in 15 subjects with image planes that are known to be particularly susceptible to respiratory artifact. A significant improvement in image quality was achieved compared with conventional nonreordered and existing reordering methods.

The objective was to investigate how the blood flows in the thoracic aorta, with special emphasis on flow reversal and flow into the coronary arteries. Three-directional MR velocity mapping was used to map multidirectional flow velocities in the aorta in 14 normal subjects and 14 patients with coronary artery disease. Dynamic flow vector maps and through-plane velocity maps were used. The flow reversed in all subjects in the upper ascending aorta and usually also in the distal aortic arch. Retrograde flow became antegrade again at various levels in the ascending aorta and in the coronary sinuses. Seven flow characteristics were investigated that, lumped together, were significantly different (P = .0005) in normal subjects compared with patients and in normal subjects 70 years of age and older compared with those younger than 70 years of age.

Abnormal diastolic left ventricular function is an early marker for myocardial disease and may be impaired even when global systolic function is normal. Subendocardial function is affected early in ischaemic heart disease and by altering left ventricular long axis motion, may contribute to abnormal transmitral pressure gradients. Regional myocardial long axis velocity in diastole measured by magnetic resonance was compared with left ventricular filling measured by Doppler echocardiography in 25 patients with coronary artery disease. Fifteen patients also underwent magnetic resonance assessment at the time of onset of early diastolic blood flow. The onset of diastolic long axis velocity preceded flow across the mitral valve by a mean of 46 ms. Mean long axis myocardial velocity correlated with peak early filling velocity (E) (r = 0.73, P < 0.001), early deceleration (r = -0.73, P < 0.001), and the early to late filling ratio (E/A) ratio (r = 0.6, P < 0.01). Maximum myocardial long axis velocity also correlated with peak early filling velocity (r = 0.56, P < 0.01), early deceleration rate (r = 0.63, P < 0.001), and the E/A ratio (r = 0.53, P < 0.01). The variability of long axis velocity around the ventricle correlated inversely with peak early filling, (r = -0.7, P < 0.001), early deceleration (r = -0.56, P < 0.01), and the E/A ratio (r = -0.48, P < 0.02). Peak atrial filling velocity did not correlate with any measure of long axis myocardial velocity. We conclude that early diastolic long axis myocardial velocity has a significant effect on left ventricular filling.

A motion-registered spatiotemporal phase-unwrapping method for extending the dynamic range of cine magnetic resonance phase velocity measurements is presented. The interframe cardiac movement is estimated from the magnitude image derived from the velocity encoded raw data, which ensures that the phase signal is unwrapped in the temporal direction with reference to pixels belonging to the same anatomic flow region. An extra step of spatial phase correction is then used to further eliminate any residual errors. The combination of spatial and temporal information for phase unwrapping provides a robust way of extending the dynamic range of cine velocity data in the presence of large phase aliasing errors.

Diastolic function is an important element of overall left ventricular function. The pattern of flow across the mitral valve is commonly used as a measure of diastolic ventricular function. Magnetic resonance (MR) velocity mapping of blood flow across the mitral valve was compared with Doppler echocardiography. Nineteen patients with known coronary artery disease (mean age, 62 years; 11 with previous myocardial infarction) were studied. The mean value of peak early filling velocity (+/- standard deviation) was 60.1 cm/sec +/- 14.3 with the MR method and 59.4 cm/sec +/- 13.7 with echocardiography (P = .732). The mean difference between the two measurements (95% confidence interval) was -0.8 cm/sec (-5.2 cm/sec, +2.2 cm/sec). The mean value of early deceleration was 4.3 m/sec2 +/- 1.5 with the MR method and 4.0 m/sec2 +/- 1.5 with echocardiography (P = .073). The mean difference was -0.4 cm/sec2 (-0.92 cm/sec2, +0.05 cm/sec2). The mean value of peak atriosystolic velocity was 51 cm/sec +/- 14.6 with the MR method and 62 cm/sec +/- 17.2 with echocardiography (P = .002). The mean difference was -11 cm/sec (-18.1 cm/sec, -3.45 cm/sec). Peak atrial filling was consistently lower with the MR method than with echocardiography. Time-averaged measurements of ventricular filling with MR velocity mapping are an accurate measure of early diastolic filling but underestimate the velocity of atriosystolic filling.

We used magnetic resonance imaging with cine velocity vector mapping to study blood flow patterns in the thoracic aorta of patients with aortic aneurysms. Spin-echo images of the thoracic aorta were acquired in orthogonal and oblique planes. Cine phase-shift velocity maps were then acquired in selected aortic planes, with velocity encoded in two orthogonal directions. The two-directional velocity data were processed to generate flow vector maps depicting flow distribution in the chosen plane. Diameter ratios between the aortic valves and aneurysmal ascending aortas were reduced, causing blood to enter as a relatively narrow stream with lateral vortical, recirculating flow. In atherosclerotic aneurysms, there was abnormal angulation between the left ventricular outflow tract and ascending aorta, causing the stream to attach to the anterior aortic wall, with recirculating flow posteriorly. In Marfan patients, the primary stream was central with vortices on either side. In patients with coarctation, the main stream attached to the posterior wall of the descending aorta, with recirculation anteriorly. Magnetic resonance imaging with cine velocity mapping allows comprehensive assessment of aortic anatomy and blood flow patterns. Sequential studies at early stages may provide new information about the natural history of aortic aneurysms.

Functional evaluation of the cardiovascular system using rapid imaging (spiral echo planar), chemical shift, and velocity mapping is capable of making the diagnosis in congenital and acquired cardiovascular disease which, between them, cause the largest number of deaths of any disease in the western world and massive morbidity and suffering. Furthermore, for the first time in the history of medicine, there is the opportunity to apply preventive measures to eardicate the epidemic of preventable arterial disease. There needs to be a change of emphasis and a switching of resources to apply to the most common diseases rather than to those which are most easily studied. There also needs to be proper training in cardiovascular MR, not so much for imagers as for cardiologists and experts in vascular disease.

OBJECTIVE We describe a noninvasive method for visualization of flow and demonstrate its application in a flow phantom and in the great vessels of healthy volunteers and patients with aortic and pulmonary arterial disease. The technique uses multidirectional MR velocity mapping acquired in selected planes. Maps of orthogonal velocity components were then processed into a graphic form immediately recognizable as flow. MATERIALS AND METHODS Cine MR velocity maps of orthogonal velocity components in selected planes were acquired in a flow phantom, 10 healthy volunteers, and 13 patients with dilated great vessels. Velocities were presented by multiple computer-generated streaks whose orientation, length, and movement corresponded to velocity vectors in the chosen plane. RESULTS The velocity vector maps allowed visualization of complex patterns of primary and secondary flow in the thoracic aorta and pulmonary arteries. The technique revealed coherent, helical forward blood movements in the normal thoracic aorta during midsystole and a reverse flow during early diastole. Abnormal flow patterns with secondary vortices were seen in patients with dilated arteries. CONCLUSION The potential of MR velocity vector mapping for in vitro and in vivo visualization of flow patterns is demonstrated. Although this study was limited to two-directional flow in a single anatomical plane, the method provides information that might advance our understanding of the human vascular system in health and disease. Further developments to reduce the acquisition time and the handling and presenting of three-directional velocity data are required to enhance the capability of this method.

The pattern of left ventricular long-axis motion during early diastole was assessed with magnetic resonance (MR) velocity mapping in 31 healthy volunteers. Regional long-axis velocity varied with time and position around the ventricle. During systole, the base descended toward the apex. The greatest magnitude of long-axis velocity occurred during early diastole. The lateral wall had the highest velocity (140 mm/sec +/- 40 [mean +/- standard deviation]); the anterior and inferior walls had lower velocities (96 mm/sec +/- 27 and 92 mm/sec +/- 34, respectively). The inferoseptal area consistently had the lowest velocities (87 mm/sec +/- 40). Absolute values of peak early-diastolic velocity declined with age (r = -.64, P.001). Peak early-diastolic velocity was not dependent on heart rate (r = .014, P = .94). Regional variations in left ventricular wall motion were seen. MR velocity mapping is a useful technique for assessing regional left ventricular long-axis heart function.

Aortic atherosclerosis and coronary artery disease (CAD) are closely linked. Early detection of aortic atherosclerosis with the adoption of appropriate preventive measures may therefore help to reduce mortality and morbidity related to CAD. Arterial remodeling, by which the wall adapts to physiological or pathological insults by a change in vessel size, is being increasingly recognized as an important aspect of atherosclerosis. In this prospective longitudinal study we used cardiovascular magnetic resonance (CMR) to detect aortic plaque and to study aortic wall remodeling in asymptomatic subjects.We recruited 175 healthy volunteers (49 years, 110 men) and documented their cardiovascular risk profile. Each subject underwent echocardiogram (ECG)-gated T1-weighted spin-echo imaging of the infrarenal abdominal aorta at baseline and after 2 years.Of the 175 subjects who volunteered at baseline, CMR was successful in 174 (99%), with one (0.6%) failure due to claustrophobia. At 2 years, follow-up scanning was performed in 169 subjects (97%). Infrarenal aortic plaque was identified at baseline in nine (5.2%) subjects. This was reconfirmed in all nine (100%) cases at 2-year follow-up. No new cases of infrarenal plaque were identified at follow-up. The signal characteristics of the plaque on the subtracted images of the Dixon method indicate that all plaques were fibrous. In the nine subjects with infrarenal plaque, the total plaque burden increased as assessed by the total wall volume (561 to 677 mm3, p = 0.0063). The total vessel volume also increased (1737 to 1835 mm3, p = 0.031) but there was no change in the total luminal volume (1175 to 1157 mm3, p = 0.29).Cardiovascular magnetic resonance detects subclinical aortic atherosclerosis, can follow plaque burden over time, and confirms the presence of Glagov remodeling with preservation of the lumen despite progression of plaque. Cardiovascular magnetic resonance is well suited for the longitudinal follow-up of the general population with atherosclerosis, may help in the understanding of the natural history of atherosclerosis, and in particular may help determine factors to retard disease progression at an early stage.

The measurement of limb blood flow at rest and during reactive hyperaemia has potential as a marker of vascular health and endothelial function because it is the stimulus that causes flow-mediated dilatation, commonly measured as brachial arterial reactivity. Because the flow increases are short lived, they represent a significant challenge for measurement by cardiovascular magnetic resonance. In this study we used a real time, single shot zonal echo-planar imaging method (ZEPI) to study reactive hyperaemia in the femoral artery of five healthy volunteers. Flow velocity was measured every 78 msec. Changes in peak forward flow velocity during systole (580 vs. 390 mm/sec, p

Aiming for robust high-resolution free respiration coronary artery imaging, localized tracking volume selective 3D-EPI at spatial resolution 1.25 x 1.25 x 3 mm and temporal resolution 65 ms was evaluated in 14 normal subjects. Subject-specific motion tracking factors were measured between diaphragm navigator and coronary artery in S-I and A-P directions. Imaging was repeated with and without tracking, accepting 128 cardiac cycles over a 20-mm range from free breathing. Reference images with minimal respiratory motion (5-mm range) used LED-guided multiple breathholds. Depending on accurate motion measurement, coronary arteries were imaged with tracking, in a 20-mm range of free breathing, with increased scan efficiency but without significant loss of image quality compared to multiple breathhold imaging.

This is the first study of the intravascular iron oxide particle contrast agent, NC100150 Injection (Nycomed Imaging AS, Oslo, Norway, a part of Nycomed Amersham) in magnetic resonance imaging of the human heart. Eighteen healthy male volunteers were studied at both 0.5 and 1.5 T before and after the administration of NC100150 Injection. Transaxial spin-echo images were acquired at both field strengths, conventional gradient-echo cine images at 0.5 T, and breathhold Turbo-FLASH cine images at 1.5 T. Optimized cine imaging sequences were used postcontrast, with a high flip angle of 60-70 degrees. In the spin-echo images there was a significant reduction in the blood pool flow artifact at the level of the right atrium (0.5 T, 57%, p < 0.01; 1.5 T, 41%, p = 0.01) and the left ventricle (LV) (0.5 T, 45%, p = 0.01; 1.5 T, 45%, p < 0.01). In the conventional gradient-echo cines at 0.5 T, there was a significant increase in the LV blood pool and myocardial signal difference-to-noise ratio (SDNR) in the diastolic (56%, p = 0.01) and systolic (141%, p < 0.001) frames. There was also a significant increase in the signal intensity (SI) gradient at the LV blood pool-myocardial border in the diastolic and systolic frames (both p < 0.001). At higher doses of NC100150 Injection (3 and 4 mg/kg), a rim of signal void around the LV blood pool was observed, perfectly defining the LV blood pool-myocardial border. In the Turbo-FLASH breathhold cines at 1.5 T, there was a significant increase in the LV blood pool-myocardial SDNR in the diastolic (221%, p < 0.001) and systolic (916%, p < 0.001) frames. Again, there was also a significant increase in the SI gradient at the LV blood pool-myocardial border in the diastolic and systolic frames (both p = 0.003). In conclusion, NC100150 Injection was given safely to 18 healthy subjects. Image quality and LV blood pool-myocardial definition were improved after the administration of NC100150 Injection. These improvements enable better spin-echo anatomical definition, better definition of myocardial wall motion, and should improve the capability of automated edge detection algorithms.

This paper addresses the use of reduced FOV (field-of-view) imaging with spatially variable resolution for 3-D MR coronary angiography. Details involved in using the technique for reducing imaging time and facilitating the management of respiratory motion are discussed. The technique was evaluated with phantom experiments and right coronary artery images of 11 asymptomatic volunteers using a 0.5 T MR system.

Using an adapted two-dimensional spatially selective RF excitation scheme, a novel yet practical three-dimensional (3D) zonal echo-planar imaging technique for MR coronary angiography has been developed. The robustness of the technique compared with the two-dimensional (2D) segmented fast low angle shot (FLASH) method was evaluated using the right coronary artery images of 16 asymptomatic volunteers with a 0.5-T mobile scanner. Each 3D acquisition required multiple breath-holds, and real-time navigator echoes were used to ensure consistent breath-holding. Advantages of the technique include an improved signal-to-noise ratio, clearer depiction of tortuous coronary vessels due to decreased partial volume effects, and reduced motion blurring by the use of a short echo-planar readout.

Magnetic resonance imaging (MRI) with navigating techniques based on consecutive breath-holds demand a level of respiratory control that is often beyond the capability of patients with lung disease. The objectives of this investigation were to develop and evaluate a navigating technique for lung MRI that does not rely on patient cooperation. Navigating techniques were implemented at 0.5 T using conventional imaging techniques of short echo-time and imaging during normal breathing in the diastolic phase of the cardiac cycle. A column of spins, orthogonal to the diaphragm, was excited both immediately before and after the imaging segment. These signals were processed in real time to provide the position of the lung-diaphragm interface. An imaging segment was considered correctly acquired only when the interface position was within the acceptance window both before and after the acquisition of the segment. A distribution of lung-diaphragm interface positions obtained during normal respiration was employed to define the acceptance window. In the case of multislice techniques, the position of the lung-diaphragm interface immediately before the imaging segment was also employed to decide which phase-encoding step to acquire next, therefore reducing the apparent frequency of the respiratory motion. A distribution of interface positions, updated in real time, served as a reference for the allocation of phase-encoding steps according to diaphragm position. The lung images obtained represent a significant advance in image quality, improving further the ability of MR to detect and monitor pulmonary disease. Motion artifacts were reduced, and images reliably demonstrated smaller vessels, which are not normally visible without navigation.

The reproducibility of MR imaging for the measurement of aortic compliance was studied in 47 healthy volunteers. Long and short term reproducibility and intraobserver variability were tested. The method was modified to improve image quality and short term reproducibility and intraobserver variability retested. For comparison, spin echo imaging was compared with cine gradient echo imaging. Initial long term reproducibility showed a mean difference (+/-SE) of 3% (+/- 7%) with 95% confidence interval (CI) for limits of agreement of +/- 69%. Short term reproducibility (7% +/- 6%, 95% CI +/- 46%) and intraobserver variability (1% +/- 2%, 95% CI +/- 31%) were better. After modification of the technique and optimization of image quality, both short term reproducibility and intraobserver variability improved (0% +/- 3%, 95% CI +/- 17% and 5% +/- 2%, 95% CI +/- 16% respectively). Aortic compliance can be measured using spin echo MR imaging with good reproducibility provided care is taken to obtain good quality images with high spatial resolution.

Magnetic resonance imaging with multidirectional cine velocity mapping was used to study relationships between aortic blood flow patterns and the geometry of thoracic aortic aneurysms and grafts. Ten patients with 13 thoracic aortic aneurysms, single or multiple, or grafts (4) participated in the study. The causes of disease were atherosclerosis (4), Marfan's syndrome (2), trauma (1), and unknown (1), and there were two dissections. Spin-echo imaging and cine velocity mapping in 10 mm thick slices with vertical and horizontal velocity encoding were done. Maps of the two velocity components were processed into multiple computer-generated streaks whose orientation and length corresponded to velocity vectors in the chosen plane. The dynamic arrow maps were compared with previously reported aortic arrow maps from normal subjects. The forward flow occupied the entire lumen in the normal aorta in systole and small vortices were only present in the sinuses of Valsalva. Atherosclerotic aneurysms in the ascending aorta were located at the anterior right and had oblique, eccentric jet flows that created a large secondary vortex in the aneurysm. Patients with Marfan's syndrome had a central jet and two large vortices, one on each side. All other aneurysms, dissections, and grafts had irregular flows and vortices not seen in normal subjects. Magnetic resonance imaging with multidirectional velocity mapping is a powerful noninvasive tool to assess morphologic features and disturbed blood flow in aortic aneurysms and grafts. Recognizably altered flow patterns were found to be associated with altered vessel geometry. The significance of this requires further investigation. (J THORAC CARDIOVASC SURG 1995;110: 704-14)