Microstructure and mechanics of human resistance arteries.

Vascular diseases such as diabetes and hypertension cause changes to the vasculature that can lead to vessel stiffening and the loss of vasoactivity. The microstructural bases of these changes are not presently fully understood. We present a new methodology for stain-free visualization, at a microscopic scale, of the morphology of the main passive components of the walls of unfixed resistance arteries and their response to changes in transmural pressure. Human resistance arteries were dissected from subcutaneous fat biopsies, mounted on a perfusion myograph, and imaged at varying transmural pressures using a multimodal nonlinear microscope. High-resolution three-dimensional images of elastic fibers, collagen, and cell nuclei were constructed. The honeycomb structure of the elastic fibers comprising the internal elastic layer became visible at a transmural pressure of 30 mmHg. The adventitia, comprising wavy collagen fibers punctuated by straight elastic fibers, thinned under pressure as the collagen network straightened and pulled taut. Quantitative measurements of fiber orientation were made as a function of pressure. A multilayer analytical model was used to calculate the stiffness and stress in each layer. The adventitia was calculated to be up to 10 times as stiff as the media and experienced up to 8 times the stress, depending on lumen diameter. This work reveals that pressure-induced reorganization of fibrous proteins gives rise to very high local strain fields and highlights the unique mechanical roles of both fibrous networks. It thereby provides a basis for understanding the micromechanical significance of structural changes that occur with age and disease.

Contrast-enhanced Reformatted MR Images for Preoperative Assessment of the Bridging Veins of the Skull Base.

Magnetic resonance (MR) venography and computed tomographic (CT) venography are suited for displaying the convexity veins that drain the medial and lateral surfaces of the brain hemispheres. However, such is not the case for the bridging veins of the skull base. Technical factors prevent contrast material-enhanced MR or CT images obtained in standard axial, coronal, and sagittal planes from fully displaying the curved pathways of these clinically important venous structures. This limitation can be overcome by using a reconstruction technique that depicts these venous structures and their interconnections. Curved and multiplanar reformatted images that distill the important venous features often require knowledgeable manipulation of source images by an operator who is familiar with numerous venous variants and their surgical implications. The normal anatomy of the draining veins is detailed-anatomy that radiologists must master before they can show the surgeon the important venous anatomy that is often missing at standard imaging; this information will foster better communication between radiologists and their surgical colleagues. As a practical matter, the skull base veins are arbitrarily subdivided into those that are at greatest risk with the pterional approach and the subtemporal approach, respectively. These approaches can be expanded to define connections between the superficial venous system and the other valveless venous networks that drain the deep portions of the cerebral hemisphere, the scalp, face, muscles of the neck, diploë of the skull, and meninges. As radiologists gain experience, their image interpretations should mature beyond simple analysis of the primary hemodynamic changes induced by intraoperative sacrifice or injury.

Glial tumors in brodmann area 6: spread pattern and relationships to motor areas.

The posterior frontal lobe of the brain houses Brodmann area 4, which is the primary motor cortex, and Brodmann area 6, which consists of the supplementary motor area on the medial portion of the hemisphere and the premotor cortex on the lateral portion. In this area, safe resection is dependent on accurate localization of the motor cortex and the central sulcus, which can usually be achieved by using thin-section imaging and confirmed by using other techniques. The most reliable anatomic landmarks are the "hand knob" area and the marginal ramus of the cingulate sulcus. Postoperatively, motor deficits can occur not only because of injury to primary motor cortex but also because of injury to the supplementary motor area. Unlike motor cortex injury, the supplementary motor area syndrome is transient, if it occurs at all. On the lateral hemisphere, motor and language deficits can also occur because of premotor cortex injury, but a dense motor deficit would indicate subcortical injury to the corticospinal tract. The close relationship of the subcortical motor fibers and premotor cortex is illustrated. In contrast to the more constant landmarks of the central sulcus and marginal ramus, which aid in preoperative localization, the variable interruptions in the precentral and cingulate sulci of the posterior frontal lobe seem to provide "cortical bridges" for spread of infiltrating gliomas.

Deformable anatomic templates embed knowledge into brain images: part 2. Validation using functional magnetic resonance imaging of the motor hand.

OBJECTIVE: This study evaluated the concordance between the Deformable Anatomic Template (DAT)-identified origin of motor hand fibers and localization of the motor cortex of the hand by functional magnetic resonance imaging (fMRI). METHODS: Preoperative fMRI during hand motor tasks was performed on 36 hemispheres in 26 patients with gliomas in or near eloquent areas. Reformatted volume-rendered surface images were labeled with the DAT's hand motor fibers and fMRI data. Five reviewers assessed the data for concordance. RESULTS: Available fMRI data were diagnostically usable in 92% (33/36 analyzed hemispheres), with DAT anatomic accuracy in the remaining cases. The DAT prediction and fMRI findings were concordant in all 9 normal hemispheres and in 20 (83%) of 24 glioma-bearing hemispheres. The 4 discordant cases resulted from substantial mass effect by large frontal tumors. CONCLUSIONS: This study validated DAT's anatomic atlas and alignment process for the expected position of the motor cortex of the hand.

Deformable anatomic templates embed knowledge into patient's brain images: Part 1. Construction and display.

OBJECTIVE: This paper describes the methods used to create annotated deformable anatomic templates (DATs) and display them in a patient's axial 2-dimensional and reformatted volume brain images. METHODS: A senior neuroradiologist annotated and manually segmented 1185 color-coded structures on axial magnetic resonance images of a normal template brain using domain knowledge from multiple medical specialties. Besides the visible structures, detailed pathways for vision, speech, cognition, and movement were charted. This was done by systematically joining visible anatomic anchor points and selecting the best fit based on comparisons with cadaver dissections and the constraints defined on the companion 2-dimensional images. RESULTS: The DAT is commercially available for use on a picture archiving and communication system or as a standalone workstation. CONCLUSIONS: The DAT can quickly embed extensive, clinically useful functional neuroanatomic knowledge into the patient's brain images. Besides labeling visible structures, DAT displays clinically important, previously uncharted subdivisions of the fiber tracts.

Smoking and periodontal disease: discrimination of antibody responses to pathogenic and commensal oral bacteria.

Smoking is an independent risk factor for the initiation, extent and severity of periodontal disease. This study examined the ability of the host immune system to discriminate commensal oral bacteria from pathogens at mucosal surfaces, i.e. oral cavity. Serum immunoglobulin (Ig)G antibody reactive with three pathogenic and five commensal oral bacteria in 301 current smokers (age range 21-66 years) were examined by enzyme-linked immunosorbent assay. Clinical features of periodontal health were used as measures of periodontitis. Antibody to the pathogens and salivary cotinine levels were related positively to disease severity; however, the antibody levels were best described by the clinical disease unrelated to the amount of smoking. The data showed a greater immune response to pathogens than commensals that was related specifically to disease extent, and most noted in black males. Significant correlations in individual patient responses to the pathogens and commensals were lost with an increasing extent of periodontitis and serum antibody to the pathogens. Antibody to Porphyromonas gingivalis was particularly distinct with respect to the discriminatory nature of the immune responses in recognizing the pathogens. Antibody responses to selected pathogenic and commensal oral microorganisms differed among racial groups and genders. The antibody response to the pathogens was related to disease severity. The level of antibody to the pathogens, and in particular P. gingivalis, was correlated with disease severity in black and male subsets of patients. The amount of smoking did not appear to impact directly serum antibody levels to these oral bacteria.

Healthy lifestyle factors associated with reduced cardiometabolic risk.

Minimal data are available regarding the cumulative effects of healthy lifestyle behaviours on cardiometabolic risk. The objective of the present study was to examine a combination of healthy lifestyle behaviours associated with cardiometabolic risk reduction. The analysis was based on a cross-sectional study of 1454 participants from the population-based Lipid Research Clinic's Princeton Follow-up Study. The healthy lifestyle factors included fruit and vegetable intake ≥ 5 servings/d, meat intake ≤ 2 servings/d, never smoking, consuming 2-6 alcoholic drinks/week, television (TV) viewing time ≤ 2 h/d and moderate to vigorous physical activity ≥ 4 h/week. The combination of healthy lifestyle behaviours was strongly and negatively associated with the presence of cardiometabolic risk, as well as with a composite cardiometabolic risk score after adjustment for race, age, generation and sex. With each additional healthy lifestyle factor, cardiometabolic risk decreased by 31 % (OR 0·69; 95 % CI 0·61, 0·78). A higher healthy lifestyle score was associated with a lower prevalence of cardiometabolic risk (P for trend < 0·001). Compared with individuals having 0-1 healthy lifestyle behaviours, those with 5 or 6 healthy lifestyle behaviours had a 70 % lower prevalence of cardiometabolic risk (OR 0·30; 95 % CI 0·13, 0·67). Healthy lifestyle behaviours including sufficient fruit and vegetable intake, less meat intake, less TV viewing time, abstinence from smoking, modest alcohol intake and regular exercise are associated with reduced cardiometabolic risk.

Arterial anatomy of the pancreas. Part 3: segmented computed tomography-angiography mapping of perineural invasion.

This is the third in a series of medical graphics articles featuring the arterial anatomy of the pancreas as depicted on segmented computed tomography-angiography. These segmented computed tomography-angiography displays serve as a road map of the routes of tumor spread by ductal adenocarcinoma of the pancreas because perineural tumor invasion parallels the pancreatic arteries.

Arterial anatomy of the pancreas: part 2. Axial.

This is the second in a 3-part series of medical graphics articles featuring the arterial anatomy of the pancreas as depicted on computed tomography images. Tumor encasement of the peripancreatic arteries is a hallmark of ductal adenocarcinoma.

Arterial anatomy of the pancreas: part 1. Coronal.

This is the first in a series of 3 medical graphics articles featuring the arterial anatomy of the pancreas as depicted on computed tomography images. This arterial anatomy is important in clinical practice because it represents a road map of the routes of tumor spread by ductal adenocarcinoma of the pancreas.

MRI venous architecture of insula.

PURPOSE: The purpose of this paper is to describe the venous anatomy of the insula using conventional MR brain imaging and confocal reconstructions in cases with glioma induced venous dilatation (venous gliography). METHODS: Routine clinical MRI brain scans that included thin cut (1.5-2 mm) post contrast T1 weighted imaging were retrospectively reviewed to assess the insular venous anatomy in 19 cases (11 males and 8 females) with insular gliomas. Reconstruction techniques (Anatom-e and Osirix) were used to improve understanding of the venous anatomy. RESULTS: We identified the following insular and peri-insular veins on MRI: the superficial middle cerebral vein (SMCV), peri-insular sulcus vein, vein of the anterior limiting sulcus, the precentral, central, and posterior sulcus veins of the insula, the communicating veins and deep MCV. CONCLUSIONS: We concluded that venous anatomy of insula is complicated and is often overlooked by radiologists on MR brain imaging. Use of confocal imaging in different planes helped us to identify the superficial and deep middle cerebral veins and their relationship to the insula. The understanding of the insular venous architecture is also useful to distinguish these vessels from insular arteries. This knowledge may be helpful for presurgical planning prior to insular glioma resection.

MRI venous architecture of the thalamus.

PURPOSE: Our purpose is to describe the thalamic veins using a novel approach named venous gliography in cases with primary or secondary gliomas of the thalamus. Venous gliography is defined by authors as a method to visualize veins on MRI Brain T1-weighted post contrast scans containing gliomas which have induced regional venous congestion. METHODS: Routine clinical MR Imaging studies were reviewed to assess the presence of thalamic veins in 29 glioma cases. In addition, confocal reconstruction techniques (Anatom-e and Osirix) were used in cases that had thin sections (1.0-1.5mm) post contrast T1 weighted sequences. Multiplanar MIP and confocal volume rendered images were generated to evaluate the thalamic veins in those cases. RESULTS: Using venous gliography and confocal reconstruction techniques, two patterns in the venous architecture of the thalamus were documented. First, the branching pattern created by the tributaries of the internal cerebral vein, namely the superior thalamic vein and the anterior thalamic vein, which together formed the superior group of thalamic veins. Second, the pattern created by the un-branched vertically oriented veins, namely the inferior thalamic veins and the posterior thalamic veins, which joined the basal vein of Rosenthal and constituted the inferior group of thalamic veins. CONCLUSIONS: Venous gliography combined with the use of confocal reconstruction techniques provided a novel approach to display the thalamic veins that are usually not seen. The understanding of the venous architecture is mandated by the recent research where veins have taken on an important role in the perivenular spread of gliomas.

Maximizing the harvest of contrast enhancing lesions in multiple sclerosis.

Transient contrast enhancing lesions can be seen with CT in patients with MS, particularly during acute exacerbations. Conventional 40 gm iodine enhancement technique followed by immediate postinfusion scanning was compared with high dose (80 gm iodine) enhancement technique followed by a 1-hour delayed CT scan; delayed high dose technique (DHD) in nine exacerbations. New lesions, totaling 36 in all, were observed in each case with the DHD technique. With time, the borders expanded in 98% of lesions, thus confirming in vivo that a defective blood-brain barrier (BBB) underlies this phenomenon.

The influence of age and relative weight on the presentation of familial combined hyperlipidemia in childhood.

BACKGROUND: Familial combined hyperlipidemia (FCHL) has been described as the leading cause of familial hyperlipidemia. FCHL is dominantly inherited, occurs in at least 1% of the population, and is responsible for about 10% of premature coronary artery disease (CAD). OBJECTIVE: Because FCHL in childhood is not well characterized, we evaluated the interrelationships among age, percentage of ideal body weight (%IBW) and plasma lipoprotein levels in FCHL children (age 2-18 years), exploring the possibility that obesity and age may influence the presentation of FCHL in childhood. METHODS: One hundred and eighty-nine children with FCHL were studied. Significant correlations within this group were further evaluated by examining a subset of 36 FCHL children, each of whom had an unaffected sibling who could serve as a control for comparison. RESULTS: When the full group was divided into those with TG levels > 90% and those with TG levels < 90%, the correlation with %IBW was stronger in the former (r = 0.45, P < 0.005) as compared with the latter (r = 0.25, P = 0.05). Within the subset of 36 FCHL children and their 36 unaffected siblings (controls), age and sex distributions were similar. Percentage IBW (mean +/- S.D.) (117.3 +/- 29.1 for FCHL and 111.2 +/- 19.4 for controls) was similar and in the overweight range. FCHL children had significantly higher levels of total cholesterol (TC), low density lipoprotein cholesterol (LDL-C), apolipoprotein B (apo B) and triglyceride (TG) levels compared with controls (P < 0.0005 for all comparisons). Of several significant correlations observed in the full group (n = 189), only the correlations of %IBW with plasma TG levels (r = 0.45, P = 0.006), and of age with plasma TG levels (r = 0.48, P = 0.003) persisted with a similar degree of magnitude in the subset of 36 FCHL children. No correlation was significant in the controls. By Fisher's Z-test, the correlation between %IBW and TG in the FCHL children was significantly different from controls. CONCLUSIONS: These results suggest that TG levels in FCHL children, but not in their unaffected siblings, and sensitive to the presence of obesity, implying an interaction between obesity and the underlying condition, in addition, the association between age and TG level in FCHL children suggests a gradual expression of the hyperlipidermia (i.e. TG) during childhood.

Familial cavernous angiomas: natural history and genetic study over a 5-year period.

In a kindred of 122 individuals we found 5 individuals with cerebral vascular malformation, 3 representing typical cavernous angiomas. The condition was inherited as an autosomal dominant trait with variable expressivity. Forty-three relatives were examined prospectively by cranial computed tomography (CCT) and lesions were found in 15; 7 were followed prospectively with CCT scans for 5 years. Angiography in 5 of these cases failed to demonstrate the lesion. In 3 patients with previously normal CCT scans a change in blood volume or membrane permeability allowed visualization of the lesion on contrast scans. In 2 individuals, both parents of affected children, a normal CCT scan was found. This emphasizes the limitations of CCT in detecting this disorder. Biochemical and red blood cell immunological genetic linkage studies were done in 36 persons. No linkage was found with any of the markers. The natural history of this disorder, characterized by marked clinical and radiographic variation in site of lesion, and the timing and severity of intracranial hemorrhage, make it a useful model for investigating contributing factors and consequences of intracranial hemorrhage in general. For at-risk and affected patients early and sequential CCTs are necessary. Familial cavernous angioma should be included in the differential diagnosis of all young persons presenting with cerebrovascular impairment, seizures, intracranial calcifications or hemorrhage.

Pharmacokinetics of low- and high-dose intravenous diatrizoate contrast media administration.

The pharmacokinetics of diatrizoate contrast media were determined following low- (0.7 g I/kg) and high- (1.5 g I/kg) dose intravenous administration. The higher dose of contrast media produced plasma concentrations of iodine which remained approximately twice as high as conventional doses for one hour following infusion. This finding may explain the improved CT images obtained after infusion of higher doses of iodine contrast media. There was no significant long-term change in plasma osmolality noted in venous blood after either dose.

A technique for preparation, removal, and storage of cadaver spine specimens for CT evaluation.

A technique for alleviating artifacts in excision of cadaver spines for computed tomographic (CT) study is described. It maintains distension of the thecal sac by filling the spinal subarachnoid space with gelatin containing iodinated contrast media. The excision, handling, and storage procedures described prevent all but minute amounts of air from entering the specimen and producing artifacts which can degrade the CT images. The frozen specimen can be sectioned with a band saw in any plane and correlated with the CT images. This technique allows CT-anatomic correlation of not only bony and extrathecal soft tissues of the spine, but also the intrathecal neural elements.

Temporal changes in the oxidation state in in vitro blood.

The rates at which the paramagnetic compounds deoxyhemoglobin (Hb) and methemoglobin (MHb) form in vivo within an area of hemorrhage are unknown. The present experiment establishes the baseline concentrations and rates of change in paramagnetic hemoglobin concentrations, as well as the pH in normal heparinized and clotted human blood maintained in vitro at 37 degrees C under anaerobic conditions over 30 hours. There was a moderate increase in Hb concentration in normal heparinized blood (average increase was 15.5%, rate = 0.50%/hour) and a slight increase in MHb concentration in the heparinized blood and clots (average increase was 1.4%, rate = 0.044%/hour). A second experiment was done to verify the activity of the RBC systems responsible for maintaining the hemoglobin molecule in the reduced state. Conversion of MHb to Hb in these samples proceeded at a rate of 5.6%/hour. In a third experiment, blood from 11 normal subjects maintained at 4 degrees C 25 degrees C was analyzed for MHb concentration over the course of 28 days. The level of MHb formation remained in the range of normal for at least 11 days in all subjects. The authors conclude that at basal conditions created in vitro, the blood levels of both Hb and MHb remain at relatively low levels. Therefore, if the accumulation of Hb and/or MHb occurs in acute in vivo hematomas it must be driven by intrinsic tissue factors.

Neuroimaging contrast agents in ophthalmology.

Magnetic resonance (MR) imaging and computed tomography (CT) are routinely performed with the use of contrast materials in the diagnosis of neuro-ophthalmologic disease. Iodinated agents are commonly used in CT scanning and femoral contrast arteriography, and gadolinium is used in MR imaging. While contrast materials contribute greatly to diagnostic accuracy, they may also be responsible for adverse effects, ranging in severity from mild discomfort to death. The most frequent and severe side effects are associated with ionic iodinated contrast agents, while the rate of adverse reactions is less with use of nonionic iodinated contrast agents. Side effects and adverse reactions to gadolinium are uncommon, but they do occur. In neuro-ophthalmologic diagnosis, MR imaging is generally preferred over CT scanning, partly because of its greater ability to delineate soft tissue intracranial structures, but also because of the relative safety of gadolinium as a contrast agent. Properties of contrast agents are discussed in the context of specific imaging techniques and tissues investigated. Types and severity of adverse effects as well as risk factors for incurring such effects are summarized.

A sellar misadventure--imaging considerations.

This report describes a patient with a headache and a bitemporal hemianopsia immediately following endoscopic ethmoid and sphenoid sinus surgery. Computed tomographic imaging revealed tension pneumocephalus caused by surgical interruption of the boundaries between the sinus(es) and the anterior cranial cavity. The delineation of the central chiasmal injury required follow-up magnetic resonance imaging.