R. E. Coupland

Improvements in snap-shot nuclear magnetic resonance imaging

New variants of the ultra-high-speed echo-planar imaging technique have been used to obtain snap-shot images of adult patients and volunteers at 0.1 T. Modified pulsed-gradient sequences together with non-linear signal sampling and activity screened gradients have greatly improved the image quality obtainable by single-shot methods. A particular variant, modulus blipped echo-planar single-pulse technique (MBEST), although slightly slower than the blipped echo-planar single-pulse technique (BEST), is experimentally more robust and incorporates intrinsic T2 weighting. An account of these improvements together with some experimental results is presented.

Immunohistochemical and biochemical study on the development of the noradrenaline- and adrenaline-storing cells of the adrenal medulla of the rat.

SummaryThe pre- and postnatal development of the adrenal medulla was examined in the rat by immunohistochemistry and by assay of catecholamines. Immunohistochemistry involved the use of antibodies to noradrenaline (NA), adrenaline (A) and the biosynthesizing enzymes dopamine β-hydroxylase (DBH) and phenylethanolamine N-methyltransferase (PNMT). Adrenal glands were obtained from animals from the 16th day of gestation to the 7th postnatal day at daily intervals, and at the 14th postnatal day, and from adult rats. Tissues were fixed in ice-cold, 4% paraformaldehyde, buffered at pH 7.3. Cryostat sections (7 μm) were stained with the indirect immunofluorescence technique. Adrenals from the same developmental stages were assayed for the presence of DA (dopamine), NA and A by ion-pair reversed-phase liquid chromatography with electrochemical detection.In adult adrenals the majority of the medullary cells (approximately 80%) were highly immunoreactive to A and moderately immunoreactive to NA. They also showed immunoreactivity to both DBH and PNMT, i.e., they are synthesizing and storing A. The remaining cell clusters were only stained by antibodies to DBH and NA (NA-synthesizing and -storing cells). These findings correlate well with the relative concentrations of A and NA as determined by assay.Three developmental phases could be distinguished. In the first phase, the 16th and 17th prenatal day, medullary cells were only immunoreactive to DBH and NA, and only very small amounts of A as compared to NA were found. During the second period, from the 18th prenatal day to 2 or 3 days after birth, all medullary cells were immunoreactive to DBH, NA, PNMT and A, and during this phase the adrenaline concentration increased daily and became the predominant amine on the 20th day of gestation. Adrenaline represented 75% of total catecholamine on the 1st to 3rd day after birth. The third phase started at the 2nd or 3rd postnatal day and was characterized by the presence of an increasing number of medullary cells solely immunoreactive to DBH and NA, hence synthesizing and storing NA. The remaining cells were immunoreactive to DBH, NA, PNMT and A. Postnatally, the relative concentration of A continued to rise reaching 79% by the 4th postnatal day. These results indicate that initially the adrenal medullary cells are synthesizing and storing almost exclusively NA. Probably, adrenaline synthesis begins at the 16th–17th day of gestation and the cells are then capable of synthesizing and storing both NA and A (“mixed cell type”) with A synthesis and storage rapidly becoming predominant. Finally, after birth, separate NA-synthesizing and -storing cell types are formed and the so-called A cells stored predominantly (probably >90%) adrenaline with a small proportion of noradrenaline.In the medullary blastema and in the sympathetic ganglia of prenatal animals two cell types, only immunoreactive to DBH and NA, were observed. Presumably, these cells represent developing sympathetic neurons and extra-adrenal chromaffin cells; the latter cell type occasionally invades the adrenal gland. Thus, prospective medullary cells are able to synthesize and store NA before they have made contact with the cortical blastema but A-synthesizing cells are found only within the adrenal gland.Low but significant amounts of DA were found in the adrenal before birth and during the first two postnatal weeks but in the adult animal this accounted for less than 0.1% of total catecholamine.

ECHO PLANAR IMAGING OF THE HUMAN FETUS IN UTERO AT 0.5 T

The snap-shot capability of the echo-planar imaging technique is used to freeze motion effectively in human fetal studies in utero. These first results obtained at 0.5 T demonstrate diagnostic quality images without the need for averaging. Although averaging improves the image signal to noise ratio, it is shown that significant image blurring is produced even when only eight separate images are averaged over a period of a few seconds. Results are presented showing anatomical detail of the internal organs of the fetus. Some pathology is also demonstrated. These results were obtained using the modulus blipped echo-planar single-pulse technique (MBEST). Running at 10 frames/second, the modulus version of the fast low-angle excitation echo-planar technique (FLEET) is used to produce ungated fetal cardiac movies.

RAPID BIOMEDICAL IMAGING BY NMR

Abstract The first biomedical images to be produced by the new high-speed echo-planar imaging technique are presented. Clear anatomical detail is revealed in both human and animal studies performed in vivo. The potential for imaging moving objects and flow is briefly discussed.

Study of internal structure of the human fetus in utero by echo-planar magnetic resonance imaging

The ultrafast echo-planar magnetic resonance imaging technology, developed and built in Nottingham, has been used to produce the first snapshot images of the human fetus in utero. The imager, operating at a proton resonance frequency of 22 MHz, produces transaxial views in 64 or 128 milliseconds. These images comprise either 64 x 128 or 128 x 128 pixels with an in-plane resolution of 3 x 3 mm2. The slice thickness is 10 mm. Fetal scans of up to 32 contiguous slices are produced in a few minutes. These have been used to study the internal structure of the uterus and the fetus in a range of cases with gestations ranging from 26 weeks to term. Echo-planar imaging seems particularly suitable as an imaging modality since its high speed obviates image blurring arising from fetal motion.

Carcinoma of the breast imaged by nuclear magnetic resonance (NMR)

NMR has shown promise as a non-invasive and nonhazardous method of imaging the mobile proton distributtion (mainly water) on a small scale in both animal and human tissues (Mansfield and Maudsley, 1977) and more recently on a much larger whole-body scale (Mansfield, et al., 1978; Damadian et al., 1977). In this paper we report the first localization of a breast cancer by this technique in a simple mastectomy specimen from a 47-year-old woman. Following mastectomy the specimen was rapidly transferred from the City Hospital to the Physics Department and the NMR scan started about 1½ hours following operation. The specimen measured some 15 cm in the long axis, one end of which was the axillary tail; it had a maximum thickness of about 4 cm at the centre tapering off to about 1 cm at the periphery. The surface of the specimen was marked with waterproof ink for identification purposes and placed flat in a plastic container. The slice thickness scanned included the whole of the breast; the images produced corre...

REAL-TIME NUCLEAR MAGNETIC RESONANCE CLINICAL IMAGING IN PAEDIATRICS

Echo-planar imaging (EPI), a distinctive variant of nuclear magnetic resonance, needs only a fraction of a second for an image to be acquired and so is free from movement artifacts caused by respiration or heart beat. Clinical findings in the lungs, heart, and mediastinum of three children with high respiratory and heart rates who were examined by EPI are described.

On the uptake of exogenous catecholamines by adrenal chromaffin cells and nerve endings

SummaryLight-microscopic autoradiography has revealed characteristic labelling patterns in adrenal medullary cells following the intravenous administration of different catecholamines. The uptake patterns for [3H] dopa, [3H] dopamine, [3H] noradrenaline and [3H] adrenaline have been compared. In all cases A cells were more active than NA cells and cells situated in the zone nearest the cortex demonstrated a markedly higher rate of uptake than central cells. It was concluded that adjacent chromaffin cells with very similar morphology may differ as much as 50 fold in their capacities to incorporate exogenous amines. The adrenergic nature of the innervation of the vessels of the adrenal cortex and capsule in the mouse was confirmed.

Ultrastructural features of the mammalian adrenal medulla

The term adrenal medulla can only be applied with semantic verisimility to chromaffin cells aggregated to form a distinct mass within the adrenal glands of mammals. In lower forms the relationship of chromaffin and cortical (interrenal) elements is often less intimate, as in fishes and amphibia, or the chromaffin elements form multiple small islets scattered through-out the adrenal gland (interrenal tissue) in birds or exist as scattered islets or as a continuous envelope of cells associated with adrenal cortical tissue in reptiles (1–5).

On the uptake and storage of 5-hydroxytryptamine, 5-hydroxytryptophan and catecholamines by adrenal chromaffin cells and nerve endings

SummaryLight-microscopic autoradiographs of the adrenal medulla at various intervals after the intravenous injection of [3H] 5-HTP, [3H] 5-HT, [3H] noradrenaline and [3H] adrenaline have been studied. The distribution of silver grains following [3H] 5-HTP uptake was found to be uniform over each of the two main cell populations, adrenaline-storing (A) cells and noradrenaline-storing (NA) cells in the adrenal medulla, but A cells were twice as active as NA cells in incorporating the isotope, a situation very similar to that found after [3H] dopa uptake. 5-HT administration resulted in a pattern resembling the distribution of [3H] noradrenaline uptake, with A cells being 4 or 5 times more active than NA cells and a gradient of activity from the periphery of the medulla inwards. However, the time-course for the loss of radioactivity was not the same for both amines: levels of 5-HT activity were not significantly reduced after one week whereas the degree of [3H] noradrenaline labelling after one week was less than 10% of that at one hour. Thus 5-HT may be bound to sites in the adrenal medulla normally occupied by noradrenaline but it would appear that the release mechanism is different. There was no evidence of 5-HT uptake by adrenal nerve endings.