Diamorphine analgesia after caesarean section. Comparison of intramuscular and epidural administration of four dose regimens

In a randomised double-blind study, the efficacy, duration of action and side effects of five diamorphine analgesia regimens following Caesarean section are described. The time to next analgesia was shorter in the 5 mg intramuscular group (3.53 hours) than in any of the four epidural groups: 5 mg (5.7 hours, p = 0.007), 2.5 mg (4.76 hours, p = 0.103), 5 mg with adrenaline 1/200,000 (7.2 hours, p = 0.001) and 2.5 mg with adrenaline 1/200,000 (6.05 hours, p = 0.007). Multiple regression analysis showed that the addition of adrenaline significantly increased the duration of action of epidural diamorphine (p less than 0.05). The 5 mg dose with adrenaline showed no advantage when compared with 2.5 mg with adrenaline (p = 0.16). No serious side effects were reported in any group.

Spoiling of transverse magnetization in steady-state sequences

A detailed analysis is presented of a method to eliminate transverse magnetization prior to each rf excitation in pulse sequences with TR less than T2. It is shown that artifact-free images with high T1 contrast can be obtained only if a phase shift that is incremented during each TR interval is applied to the transverse magnetization. Computer simulations are used to show that when this phase increment is 117 degrees, the steady-state transverse magnetization prior to each rf pulse is nulled over a wide range of T1, T2, and rf tip angles, resulting in optimal T1 contrast. Such nulling of steady-state transverse magnetization cannot be obtained by using large gradient pulses, or gradients of random or linearly incremented amplitude. Images of phantoms and human subjects confirm the theoretical predictions.

Gradient moment nulling for steady-state free precession MR imaging of cerebrospinal fluid

Steady-state free precession (SSFP) pulse sequences can produce magnetic resonance (MR) images rapidly, in which cerebrospinal fluid (CSF) is several times more intense than the other tissues. However, motion in the presence of magnetic field gradients reduces the intensity of CSF drastically, unless the time integral of the gradient waveform between each radio-frequency (rf) pulse vanishes. The consequences of motion on SSFP are explored here in detail theoretically and experimentally. The principle of gradient moment nulling is applied with the objective of giving CSF in SSFP images uniformly high intensity everywhere, in spite of motion. Theoretical analysis of the phase of the transverse magnetization from a group of isochromats, with a trajectory described by a Taylor series, reveals how motion along each direction disrupts SSFP and also causes ghost artifacts. Images of CSF in the cervical spine are found to have less extensive flow voids and weaker ghosts from pulsation if the first moment calculated from the rf pulse to the center of the gradient echo vanishes for both the frequency encoding and slice selection gradient waveforms. However, first-order moment nulling of the phase encoding gradient waveform is unnecessary for SSFP imaging of CSF.

Naming the illness: the power of words

A key part of the doctor-patient encounter is the giving of a name to the patient's illness by the physician. Personal, professional, societal, and bureaucratic factors influence physicians in their choice of a name and the manner in which they present these words to the patient. The effect of the illness name on the individual patient may be determined not only by individual experience and knowledge, but also by social, cultural, and economic factors. Citing examples from medical practice from its origins in ancient Greece to the present day, this paper draws attention to the crucial significance of medical language in doctor-patient communication. A heightened awareness by physicians of communication style is suggested, both in encounters with patients and in the training of medical students and residents.

Ineffectiveness of averaging for reducing motion artifacts in half-Fourier MR imaging

Two data sets for half-Fourier imaging (HFI) can be collected in the same time as one data set for conventional full Fourier imaging (FFI). The hypothesis is that averaging twice as much data in HFI does not make ghost artifacts caused by motion have less signal intensity than in FFI. This hypothesis was tested with images of a human subject by measuring the standard deviation within regions of interest containing ghosts. The control experiment involved measuring the standard deviation on images from the same data reconstructed with FFI. The images were formed after averaging of one to eight data sets from a collection of nine data sets acquired sequentially. Background ghosts or those in other regions of low intensity were less intense on images from HFI after twice as much averaging as in FFI, but this was not the case for ghosts superimposed on anatomic structures. This observation is explained by showing that an image obtained by means of FFI can be expressed in terms of two images obtained by means of HFI applied to the top and bottom halves of the data. The use of HFI to allow twice as much averaging without prolonging data acquisition time is not advantageous for reducing ghost artifacts caused by motion.

Effect of granulocyte-macrophage colony-stimulating factor on the induction of unresponsiveness by lymphoid cells

Skin grafts can be significantly prolonged in ALS-treated mice by the injection of 25 x 10(6) donor bone marrow cells or 50 x 10(6) spleen cells. Lymph node cells and thymocytes are only minimally effective in prolonging grafts. The effect of a hematopoietic growth factor, granulocyte-macrophage colony stimulating factor (GM-CSF) was studied in this model of unresponsiveness. C3H/He lymphoid cell donors were treated with GM-CSF. Either normal or GM-CSF-treated cells were injected into ALS-treated B6AF1 mice grafted with C3H/He skin. GM-CSF treatment significantly augmented the effect of marrow in prolonging graft survival at doses of 1 to 25 x 10(6) cells. In contrast, GM-CSF had no effect on the graft-prolonging effect of spleen cells when 50 x 10(6) cells were given. When the dose of cells was reduced to 25 x 10(6), graft survival in the group given GM-CSF-treated cells was prolonged compared with survival in the group given normal cells. Grafts in the group given GM-CSF-treated lymph node cells were rejected in sensitized fashion. When marrow and spleen are separated on a Percoll gradient, the cell active in promoting graft survival is recovered primarily in the 52.5% fraction. The graft-prolonging effect of the 52.5% marrow fraction was not affected by GM-CSF treatment. In contrast, GM-CSF-treated marrow cells in the 60% fraction significantly prolonged graft survival, while normal marrow cells in this fraction had no effect on graft survival. GM-CSF-treated spleen cells in the 52.5% and 60% fractions significantly decreased graft survival compared with normal cells when given at a dose equal to the number of cells recovered from 50 x 10(6) cells. When the dose of fractionated spleen cells was reduced, GM-CSF-treated spleen cells were more effective than normal cells in prolonging graft survival. These results indicate that GM-CSF activates a cell in marrow that promotes graft survival. This cell is recovered in the 60% Percoll fraction. In contrast, GM-CSF appears to affect two cell populations in spleen, one beneficial and one detrimental to graft survival. The predominant effect depends on the dose of spleen cells that is given.

Characterization of spleen cells capable of inducing unresponsiveness in ALS-treated mice

C3H/He skin allografts are significantly prolonged in ALS-treated B6AF1 mice by the injection of 50 x 10(6) C3H/He spleen cells 1 week postgrafting. To identify and characterize the spleen cell active in promoting graft survival, C3H/He spleen cells were separated on a discontinuous Percoll gradient and the various fractions were assayed for the ability to prolong skin graft survival in ALS-treated B6AF1 mice. In addition, unfractionated spleen and spleen fractions were depleted of specific cell populations before injection to determine the effect of various cell populations on graft prolongation. The active cell was recovered primarily in the 52.5% Percoll fraction. Cells in the 60% fraction also had a graft-prolonging effect, but not as significant as that of the 52.5% fraction. Depletion of Thy 1, Ia and Ig-positive cells from unfractionated spleen or spleen fractions did not decrease the graft-prolonging effect. Both Fc gamma R-positive and Fc gamma R-negative cells prolonged graft survival, but the Fc gamma R- cells were the most effective. In contrast to the effect of spleen cells, lymph node cells and thymocytes are relatively ineffective in prolonging graft survival in ALS-treated mice. When lymph node lymphocytes and thymocytes were separated on a Percoll gradient, the cell population active in prolonging graft survival was recovered primarily in the 52.5% fraction. Treatment of the 52.5% fraction of lymph node lymphocytes or thymocytes with monoclonal antibody to Thy 1 before injection abrogated the graft-prolonging effect. These results indicate that the spleen cell(s) active in prolonging graft survival in ALS-treated mice is a non-T, non-B cell, as it lacks Thy 1, Ia, and Ig surface markers. Both Fc gamma R+ and Fc gamma R- spleen cells are effective in prolonging grafts, but Fc gamma R- cells are the most effective. In contrast, the active cell in lymph node and thymus is Thy 1-positive, indicating that it is a T lymphocyte.

Motion-insensitive, steady-state free precession imaging

Steady-state free precession (SSFP) pulse sequences employing gradient reversal echoes and short repetition time (TR) between successive rf excitation pulses offer high signal-to-noise ratio per unit time. However, SSFP sequences are very sensitive to motion. A new SSFP method is presented which avoids the image artifacts and loss of signal intensity due to motion. The pulse sequence is designed so that the time integral of each of the three gradients is zero over each TR time interval. The signal then consists of numerous echoes which are superimposed. These echoes are isolated by combining the data from N different scans. In each scan a specific phase shift is added during every TR interval. Each of these N isolated echoes produces a motion-insensitive, artifact-free image. Because all the echoes are sampled simultaneously, the signal-to-noise ratio per unit time in this SSFP method is higher than in existing SSFP techniques which sample only one echo at a time. The new method was implemented and used to produce both two- and three-dimensional images of the head and cervical spin of a human patient. In these images the high signal intensity of cerebrospinal fluid is preserved regardless of its motion. Further work is required to evaluate the imaging parameters (TR, TE, rf tip angle) so as to give optimal tissue contrast for the various echoes.

Mechanistic studies of ionizing radiation and oxidative mutagenesis: genetic effects of a single 8-hydroxyguanine (7-hydro-8-oxoguanine) residue inserted at a unique site in a viral genome

T4 RNA ligase was used to construct a deoxypentanucleotide containing a single 8-hydroxyguanine (7-hydro-8-oxoguanine; G8-OH) residue, which is one of the putatively mutagenic DNA adducts produced by oxidants and ionizing radiation. The pentamer d(GCTAG8-OH)p was prepared by the ligation of a chemically synthesized acceptor molecule, d(GCTA), to an adducted donor, 8-hydroxy-2'-deoxyguanosine 5',3'-bisphosphate. The acceptor was efficiently converted to the reaction product (greater than 95%), and the final product yield was 50%. Following 3'-dephosphorylation, the pentamer was characterized by UV spectroscopy, by high-pressure liquid chromatography, and by gas chromatography-mass spectrometry of the nucleosides released by enzymatic hydrolysis. Both d(GCTAG8-OH) and an unmodified control were 5'-phosphorylated by using [gamma -32P]ATP and incorporated covalently by DNA ligase into a five-base gap at a unique NheI restriction site in the otherwise duplex genome of an M13mp19 derivative. The ligation product contained G8-OH at the 3' residue of an in-frame amber codon (5'-TAG-3') (genome position 6276) of the phage lacZ alpha gene. The adduct was part of a nonsense codon in a unique restriction site in order to facilitate the identification and selection of mutants generated by the replication of the modified genome in Escherichia coli. Both control and adducted pentamers ligated into the genome at 50% of the maximum theoretical efficiency, and nearly all (approximately 90%) of the site-specifically adducted products possessed pentanucleotides that were covalently linked at both 5' and 3' termini. The G8-OH lesion in the NheI site inhibited the cleavage of the site by a 200-fold excess of NheI.(ABSTRACT TRUNCATED AT 250 WORDS)

3-D imaging of the CNS

3-D gradient echo techniques, and in particular FLASH, represent a significant advance in MR imaging strategy allowing thin section, high resolution imaging through a large region of interest. Anatomical areas of application include the brain, spine, and extremities, although the majority of work to date has been performed in the brain. Superior T1 contrast and thus sensitivity to the presence of GdDTPA is achieved with 3-D FLASH when compared to 2-D spin echo technique. There is marked arterial and venous enhancement following Gd DTPA administration on 3-D FLASH, a less common finding with 2-D spin echo. Enhancement of the falx and tentorium is also more prominent. From a single data acquisition, requiring less than 11 min of scan time, high resolution reformatted sagittal, coronal, and axial images can obtained in addition to sections in any arbitrary plane. Tissue segmentation techniques can be applied and lesions displayed in three dimensions. These results may lead to the replacement of 2-D spin echo with 3-D FLASH for high resolution T1-weighted MR imaging of the CNS, particularly in the study of mass lesions and structural anomalies. The application of similar T2-weighted gradient echo techniques may follow, however the signal-to-noise ratio which can be achieved remains a potential limitation.

Half-Fourier MR imaging of CNS disease

Three MR imaging techniques were compared in 37 CNS examinations. In each case, postprocessing of a single data set in three different ways was used for comparison. Eleven of the 37 patients had a clinical diagnosis of multiple sclerosis. The primary purpose of this investigation was to evaluate the quality of the half-Fourier imaging technique. With half-Fourier imaging, scan time can be reduced by approximately half without compromising spatial resolution. In T2-weighted examinations at 1.0 T (with present instrumentation), application of the half-Fourier technique leads to a decrease in lesion detectability in patients with multiple sclerosis: this is because there is a reduction in the signal difference-to-noise ratio of 32 +/- 11%. For T2-weighted screening of the CNS on high-field MR systems, with the exception of multiple sclerosis, half-Fourier imaging may offer a suitable compromise by decreasing scan time while preserving spatial resolution. Application of the half-Fourier method to T1-weighted techniques also results in diagnostic-quality images.

Anatomy of the proximal femur as seen with three-dimensional magnetic resonance imaging

Magnetic resonance imaging (MRI) is being applied successfully to the study of the musculoskeletal system with notable recent advances, including the use of three-dimensional imaging techniques. The authors introduce three-dimensional MRI as a technique for examining proximal femoral anatomy and suggest its use as an improvement on current methods for prosthetic hip design. The proximal femurs of 14 cadavers were scanned using a three-dimensional FISP technique and the images were subsequently manipulated on a three-dimensional MRI image-processing workstation to produce rotated surface reconstructions and multiplanar reformatted images. The surface rotations showed that the marrow cavity contours closely follow the contours of the external cortex. Axially reformatted images allowed relative area measurements of the marrow cavity, quantifying the variability between subjects.

Experimental trials with Gd(DO3A)--a nonionic magnetic resonance contrast agent

Gd(DO3A), a member of a new family of nonionic MRI contrast agents, was evaluated in vivo in a rat model. In 10 animals, enhancement of an intracerebral glioma was studied following Gd(DO3A) injection. Correlation with tissue pathology was obtained in all cases. Comparative studies of renal enhancement were performed in 15 animals, utilizing disodium Gd(DTPA)2-, sodium-Gd(DOTA)-, and Gd(DO3A). With the glioma model, Gd(DO3A) administration provided enhancement of tissue with an altered blood brain barrier, thus permitting identification of the bulk of the neoplastic lesion. Comparative studies revealed that enhancement of normal renal medulla was equal or superior with Gd(DO3A).

Artifacts due to residual magnetization in three-dimensional magnetic resonance imaging

An artifact is identified in magnetic resonance images produced by the three-dimensional FLASH technique, which features a short repetition time TR. The artifact is caused by differential spoiling of transverse magnetization by the phase-encoding gradients. The image intensity in different slices becomes altered, especially for short TR and large flip angle, which are conditions for achieving strong T1-weighted contrast. The effectiveness of spoiler gradient and rephasing gradients in suppressing the artifact is evaluated experimentally in images of a uniform phantom. Spoiler gradients that are incremented in amplitude cause even more slices to deviate in intensity, and are therefore less effective than in two-dimensional techniques. Rephasing gradients make the slices uniformly intense, but also enhance the intensity of tissues that have longer T2. The further addition of constant spoiler gradients has reduced this intensity increase by one-half and allowed for an intensity difference between white matter and gray matter comparable to without a rephasing gradient.

Elimination of transverse coherences in FLASH MRI

Fast low-angle shot (FLASH) imaging enables T1-weighted scans to be acquired in a few seconds. However, the diagnostic image quality is severely compromised by the appearance of artifactual bands parallel to the frequency encode direction. We show that the band structure arises from differences in the ability of the phase encode gradient to spoil transverse coherences that build up between successive repetition intervals. A theoretical understanding of the mechanisms involved leads to a comparison between various methods of spoiling the unwanted echoes throughout the whole field of view. Spoiler gradients whose amplitudes change linearly with phase encode step number are treated in detail. The theory predicts that the spoilers will rotate and rescale the band structure and these results are confirmed experimentally. The effect of the spoilers at a given location along the gradient is equivalent to the effect on the entire field of view of an incremented phase shift applied to the radiofrequency pulse. An appropriate rf phase shift scheme should therefore provide ideal spoiling characteristics for FLASH imaging.

Structural characterization of the major adducts obtained after reaction of an ultimate carcinogen aflatoxin B1-dichloride with calf thymus DNA in vitro

The major adduct formed on acid hydrolysis of calf thymus DNA which has been reacted with 8,9-dichloro-8,9-dihydroaflatoxin B1, a chemical model of the ultimate carcinogen 8,9-dihydro-8,9-epoxyaflatoxin B1 (AFB1-epoxide), has been characterized by proton nuclear magnetic resonance and fast atom bombardment mass spectroscopy. This adduct has been identified as an N7-substituted guanine adduct analogous to that formed on reaction of AFB1-8,9-epoxide with DNA in vivo and in vitro, namely trans-8,9-dihydro-8-(7-guanyl)-9-hydroxy AFB1. This 8,9-dichloro-8,9-dihydroaflatoxin B1 adduct in DNA, like its equivalent B1 adduct in DNA, like its equivalent AFB1-epoxide adduct, is prone to quantitative imidazole ring opening of the substituted guanine in mildly alkaline conditions and to substantial depurination under mildly acidic conditions.

Fast imaging and other motion artifact reduction schemes: a pictorial overview

Since 1982, a number of techniques have been introduced for the purpose of reducing motion artifacts in magnetic resonance imaging. These are reviewed with an emphasis on effectiveness and clinical practicality. Physical restraints, data averaging, and gradient moment nulling are widely used at present. Fast imaging techniques, particularly with the advent of saturation pulses (to diminish arterial and venous pulsation artifacts), may be utilized in the future to obtain diagnostic quality abdominal and pelvic images during breath holding.

FLASH: clinical three-dimensional magnetic resonance imaging

Using 3-D FLASH, high resolution, very thin section T1 weighted images of the CNS, spine, and extremities can be obtained. From these single data sets, reformatted images whose resolution is equal to that of the original data set can be constructed in any desired plane. This approach may lead to the replacement of conventional T1 weighted spin echo imaging by 3-D FLASH techniques.

Application of image enhancement techniques to magnetic resonance imaging

Image enhancement techniques are widely available, but their applications are not well defined. The authors encourage radiologists to become familiar with these techniques, to evaluate them, and to incorporate them into specific display protocols.