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Magnetic resonance (MR; synonymous with NMR = nuclear magnetic resonance) is a universal physical technique best known for non-invasive detection and anatomical mapping of water protons (H). MR-spectroscopy (MRS) records protons from tissue chemicals other than water, intrinsic phosphorus containing metabolites, sodium, potassium, carbon, nitrogen, and fluorine. MRS is therefore an imaging technique with the potential to record human and animal biochemistry in vivo. As a result of wide availability of MRI equipment in research laboratories and hospitals, MRS is a serious competitor with PET to define normal body composition and its perturbation by pharmacological and pathological events. This article describes practical aspects of in vivo MRS with particular emphasis on the brain, where novel metabolites have been described. A survey of these new aspects of neurochemistry emphasize their practical utility as neuronal and axonal markers, measures of energy status, membrane constituents, and osmolytes, as well as some xenobiotics, such as alcohol. The concept of multinuclear in vivo MRS is illustrated by diagnosis and therapeutic monitoring of several human brain disorders. Although these methods are currently most frequently encountered in human studies, as well as with transgenic and knockout mouse models, MRS adds a new dimension to anatomic and histopathologic descriptions.
Anat Rec 2001 04
PMID:Magnetic resonance spectroscopy of the human brain. 1132 70

Cetacean (dolphin, whale, and porpoise) brains are among the least studied mammalian brains because of the formidable challenge of collecting and histologically preparing such relatively rare and large specimens. Magnetic resonance imaging offers a means of observing the internal structure of the brain when traditional histological procedures are not practical. Furthermore, internal structures can be analyzed in their precise anatomic positions, which is difficult to accomplish after the spatial distortions often accompanying histological processing. In this study, images of the brain of an adult bottlenose dolphin, Tursiops truncatus, were scanned in the coronal plane at 148 antero-posterior levels. From these scans a computer-generated three-dimensional model was constructed using the programs VoxelView and VoxelMath (Vital Images, Inc.). This model, wherein details of internal and external morphology are represented in three-dimensional space, was then resectioned in orthogonal planes to produce corresponding series of virtual sections in the horizontal and sagittal planes. Sections in all three planes display the sizes and positions of major neuroanatomical features such as the arrangement of cortical lobes and subcortical structures such as the inferior and superior colliculi, and demonstrate the utility of MRI for neuroanatomical investigations of dolphin brains.
Anat Rec 2001 12 01
PMID:Anatomy and three-dimensional reconstructions of the brain of a bottlenose dolphin (Tursiops truncatus) from magnetic resonance images. 1174 95

Transient patterns of regional, laminar, modular, neuronal, and functional organization are essential features of the developing cerebral cortex in preterm infants. Analysis of cytological, histological, histochemical, functional, and behavioral parameters revealed that transient cerebral patterns develop and change rapidly between 24 weeks post ovulation (W) and birth. The major afferent fibers (thalamocortical, basal forebrain, and corticocortical) grow through the transient "waiting" subplate zone (SP) compartment and accumulate below the cortical plate (CP) between 22 and 26 W. These afferent fibers gradually penetrate the CP after 26 W. The prolonged process of dissolution of the SP can be explained by prolonged growth and maturation of associative connections in the human cerebral cortex. The neurons and circuitry elements of the transient layers are the substrate for transient functional and behavioral patterns. The predominance of deep synapses and deep dendritic maturation underlies the immaturity and different polarity of the cortical electrical response in the preterm infant. The significant changes in the transient SP, together with profound changes in the transient architecture of the neocortical plate, parallel the changes observed in recent MRI studies. The role of the SP in the formation of cortical connections and functions is an important factor in considering the pathogenesis of cognitive deficits after brain lesions in the preterm infant.
Anat Rec 2002 May 01
PMID:Correlation between the sequential ingrowth of afferents and transient patterns of cortical lamination in preterm infants. 1198 86

This article presents the first series of MRI-based anatomically labeled sectioned images of the brain of the killer whale (Orcinus orca). Magnetic resonance images of the brain of an adult killer whale were acquired in the coronal and axial planes. The gross morphology of the killer whale brain is comparable in some respects to that of other odontocete brains, including the unusual spatial arrangement of midbrain structures. There are also intriguing differences. Cerebral hemispheres appear extremely convoluted and, in contrast to smaller cetacean species, the killer whale brain possesses an exceptional degree of cortical elaboration in the insular cortex, temporal operculum, and the cortical limbic lobe. The functional and evolutionary implications of these features are discussed.
Anat Rec A Discov Mol Cell Evol Biol 2004 Dec
PMID:Neuroanatomy of the killer whale (Orcinus orca) from magnetic resonance images. 1548 54

This study measured the effect of using anatomical cross-sections to enhance the interpretation of radiological images. It examined the effectiveness of using magnetic resonance (MR or MRI) images presented side-by-side with their corresponding cross-sectional images, as compared to using only the MR images. Student aptitude to identify anatomical structures in the radiological images was measured. The study also assessed student preferences toward the two presentation formats. Thirty-four freshmen medical students (17 females and 17 males) and a female graduate student enrolled in a clinical anatomy, embryology, and imaging course volunteered to participate in the study. A posttest-only control group design was used and the collected data were analyzed by a t-test. A survey was developed to collect student perceptions of the two presentation formats. There was no significant difference between using MR images with cross-section images and using MR images alone in the students' immediate recall of anatomical information presented in radiological images. However, the students showed strong preferences for the presentation of MR images with cross-section images and indicated that it would help them interpret radiological information.
Anat Rec B New Anat 2005 Mar
PMID:Effectiveness of using cross-sections in the recognition of anatomical structures in radiological images. 1576 32

In the follow-up of differentiated thyroid carcinoma (DTC), after total thyroidectomy and Iodine-131 therapy, thyroglobulin (Tg) levels and Iodine-131 total body have particular importance. The Tg level becomes a specific and very sensitive marker of DTC recurrence: it is usually evaluated after eradication of thyroid residual tissue (by thyroidectomy and radiometabolic therapy), in presence of high level of TSH (>35 microU/ml) obtained with the suspension of therapy or after rec-TSH administration and in absence of anti-Tg antibodies. Usually, to solve diagnostic problems in patients with negative total body Iodine-131 and high levels of thyroglobulin, we consider one or more of the following investigations, on the basis of prognostic factors: radiological examinations (neck US, skeletal X-ray, CT chest and abdomen, MRI) and scintigraphy (bone scintigraphy, Tc-MIBI or Tl-201 scintigraphy, octreoscan, PET/CT). The use of PET is well known in patients in whom carcinoma metastases are strongly suspected and who are unable of concentrating Iodine-131. In order to increase the PET sensitivity, scintigraphy is performed with high TSH levels obtained through a rec-TSH injection on the 1st and 2nd day, PET/CT scan and blood withdrawal (for Tg level evaluation) on the 3rd day. Considering the hypothesis of a recurrence with lesion size below the resolution power of the diagnostic equipment (5 mm), if PET/CT results are negative, the patients are strictly followed-up and Tg is monitored every 4-6 months. An alternative hypothesis might be not to consider the negative-PET patients as sick persons, but to attribute high Tg levels to illegitimate transcription of mRNA for Tg by the non-thyroid cells or to ectopic thyroid tissue (e.g. intrathymus). Positive PET/CT patients are evaluated for a possible surgical removal of the lesions or alternative appropriate therapies.
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PMID:[Diagnostic modalities in patients affected by differentiated thyroid carcinoma with high thyroglobulin levels and total body Iodium-131 negative: PET/CT use after recTSH]. 1576 25

The position of the lunate sulcus in fossil endocasts (when it can be determined) may serve as a potential marker of cognitive development in extinct hominid species. While the lunate sulcus is reliably present in the brains of great apes and forms the anterolateral boundary of the primary visual cortex, in humans its presentation is much more variable, and even if present, it does not correspond to a functional region. Grafton Elliot Smith, who named the lunate sulcus, claimed that it was homologous in humans and the great apes. Using high-resolution MRI, we assessed the presence/absence and course of the lunate sulcus in 110 adult subjects. We found that in the vast majority of cases, lunate sulci identified on the surface of the occipital lobe are actually composed of smaller sulcal segments that converge into an apparently continuous composite lunate sulcus. We found only 3 examples in 220 hemispheres (1.4%) of continuous lunate sulci that resembled ape lunates in form (albeit in a more posterior position). Composite lunate sulci were found in 32.7% of left hemispheres and 26.4% of right hemispheres. These results, combined with those from histological and functional imaging studies, indicate that human and ape lunate sulci are not homologous structures. We suggest that the extent of functional reorganization of the occipital region during hominid evolution has been underestimated, and that changes in this region were not just passively shaped by expansion of parietal association cortex.
Anat Rec A Discov Mol Cell Evol Biol 2006 Aug
PMID:Looking for the lunate sulcus: a magnetic resonance imaging study in modern humans. 1683 37

Trabeculae form the internal bony mesh work and provide strength to the bone; interconnectivity, overall density, and trabecular thickness are important measures of the integrity of the internal architecture. Such strength is achieved only gradually during ontogeny, whereby an increase in trabecular thickness precedes an increase in mineralization. Loss of bone mass later in life may be compensated for by thickening of the remaining trabeculae. These facts, and the role of trabeculae in mineral homeostasis, highlight the importance of investigating trabecular thickness within and between species. While nondestructive imaging techniques (i.e., muCT and MRI) are becoming increasingly popular, quantification of trabecular thickness using nondestructive techniques has proved difficult owing to limitations imposed by scanning parameters, uniform thresholding, and partial volume averaging. Here we present a computer application, which aims to overcome these problems. Validation is carried out against a phantom and against trabecular thickness measured in corresponding histological sections. Good agreement was found between these measurements. Furthermore, when trabecular thickness is recorded for modern human fetal ilia, a trend toward trabecular thickness increase is found and is in line with reports of ontogenetic morphometric changes using histological sections. However, there are discrepancies. These may in part be due to partial volume effects of obliquely oriented structures. More crucial, however, are problems inherent in histological sections, e.g., shrinkage and distortion, especially where differences in mineralization are concerned; this may affect biological interpretations.
Anat Rec A Discov Mol Cell Evol Biol 2006 Sep
PMID:Automated method to measure trabecular thickness from microcomputed tomographic scans and its application. 1689 70

MRI-based study of (3)He gas diffusion in lungs may provide important information on lung microstructure. Lung acinar airways can be described in terms of cylinders covered with alveolar sleeve [Haefeli-Bleuer, Weibel, Anat. Rec. 220 (1988) 401]. For relatively short diffusion times (on the order of a few ms) this geometry allows description of the (3)He diffusion attenuated MR signal in lungs in terms of two diffusion coefficients-longitudinal (D(L)) and transverse (D(T)) with respect to the individual acinar airway axis [Yablonskiy et al., PNAS 99 (2002) 3111]. In this paper, empirical relationships between D(L) and D(T) and the geometrical parameters of airways and alveoli are found by means of computer Monte Carlo simulations. The effects of non-Gaussian signal behavior (dependence of D(L) and D(T) on b-value) are also taken into account. The results obtained are quantitatively valid in the physiologically important range of airway parameters characteristic of healthy lungs and lungs with mild emphysema. In lungs with advanced emphysema, the results provide only "apparent" characteristics but still could potentially be used to evaluate emphysema progression. This creates a basis for in vivo lung morphometry-evaluation of the geometrical parameters of acinar airways from hyperpolarized (3)He diffusion MRI, despite the airways being too small to be resolved by direct imaging. These results also predict a rather substantial dependence of (3)He ADC on the experimentally-controllable diffusion time, Delta. If Delta is decreased from 3 ms to 1 ms, the ADC in normal human lungs may increase by almost 50%. This effect should be taken into account when comparing experimental data obtained with different pulse sequences.
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PMID:In vivo lung morphometry with hyperpolarized 3He diffusion MRI: theoretical background. 1803 13

Our aim was to determine the time course of any changes in muscle volume and shape in the lower limbs following immobilization. A healthy young woman (29 years) had suffered a fracture of the fifth metatarsal of the right foot. MRI scanning of her right thigh and calf muscles had been performed 1 month before the injury (Pre) during a scan initially planned as a teaching tool, 2 days following a 4-week immobilization period (Post), and after a 2-month recovery period (Post+2). The results show muscle volume decrements in the triceps surae (TS), quadriceps (Quad), and hamstring (Ham) of 21.9%, 24.1%, and 6.5%, respectively, between the Pre and Post measurements. At Post+2, the Quad and TS muscle volumes were still 5.2% and 9.5% lower, compared with the Pre data. The Ham muscle volume, however, was 2.7% greater than at the Pre phase. Following recovery, the increase in individual TS muscles volume was limited to both proximal and medial (with respect to the knee joint) segments of the muscles. These results indicate very substantial and rapid losses in muscle volumes, both proximally and distally to the immobilization site. The results also show that recovery is far from complete up to 2 months post cast removal. The results have implications for the requirements for rehabilitation for orthopedic patients.
Anat Rec (Hoboken) 2008 Dec
PMID:Effect of foot and ankle immobilization on leg and thigh muscles' volume and morphology: a case study using magnetic resonance imaging. 1895 3


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