Fetal shoulder measurements by fast and ultrafast MRI techniques.

The purpose of this study was to evaluate magnetic resonance imaging (MRI) of fetal shoulder measurements of fetuses with suspected macrosomia. The actual fetal shoulder measurements made immediately after birth were compared with measurements obtained by fast and ultrafast MRI techniques antepartum. Eight singleton diabetic pregnant mothers underwent MRI examination with fast imaging in steady-state precession (TrueFISP) and spin-echo (SE) and gradient-echo (GE) echo-planar (EPI) sequences to show the fetal shoulder width. The actual shoulder width was measured immediately postpartum by a neonatologist. There was a statistically significant correlation between the MRI measurements and the actual shoulder width (P < 0.001 - P < 0.05) for all sequences. TrueFISP (r = 0.98, P < 0.001) was superior to EPI sequences (r = 0.88, P < 0.01 for SE EPI and r = 0.80, P < 0.05 for GE EPI). The images of all three sequences used were free of major motion artifacts. Fast and ultrafast sequences seem to be reliable for fetal shoulder measurements and the TrueFISP was the most accurate sequence compared to SE and GE echo-planar sequences. J. Magn. Reson. Imaging 2001;13:938-942.

MR imaging in pelvic inflammatory disease: comparison with laparoscopy and US.

PURPOSE: To assess the value of magnetic resonance (MR) imaging in the diagnosis of pelvic inflammatory disease (PID) and to compare MR imaging with transvaginal ultrasonography (US) and laparoscopy. MATERIALS AND METHODS: Thirty consecutive patients hospitalized because they were clinically suspected of having PID underwent transvaginal US and T1-weighted spin-echo, T2-weighted turbo spin-echo, and inversion-recovery MR imaging at 1.5 T. All patients underwent laparoscopy after MR imaging. RESULTS: PID was laparoscopically proved in 21 (70%) patients. The MR imaging diagnosis agreed with that obtained with laparoscopy in 20 (95%) of the 21 patients with PID. The imaging findings for PID were as follows: fluid-filled tube, pyosalpinx, tubo-ovarian abscess, or polycystic-like ovaries and free pelvic fluid. Findings at transvaginal US agreed with those at laparoscopy in 17 (81%) of the 21 patients with PID. The sensitivity of MR imaging in the diagnosis of PID was 95%, the specificity was 89%, and the overall accuracy was 93%. For transvaginal US, the corresponding values were 81%, 78%, and 80%. CONCLUSION: MR imaging is more accurate than transvaginal US in the diagnosis of PID and provides information about the differential diagnosis of PID. MR imaging may reduce the need for diagnostic laparoscopy.

Low-field MRI pelvimetry.

The purpose of this study was to evaluate the usefulness of low-field MRI pelvimetry and to correlate the results with X-ray pelvimetry. A total of 19 women underwent low-field MRI pelvimetry. Mediosagittal and transverse planes were used to measure the diameters of the minor pelvic cavity. Correlations between MRI and X-ray pelvimetry were 0.96 for the sagittal inlet, 0.94 for the sagittal outlet, 0.93 for the transverse diameter (diameter transversa, DT) and 0.94 for the bispinous distance (interspinous distance, IS). The repeatability of the measurements was good. For fetuses with cephalic presentation it was also possible to determine the biparietal diameter (BPD). Low-field MRI pelvimetry was well accepted by the patients. The scanning time was less than 6 min, which is comparable with the time of X-ray examination with two planes. Magnetic resonance imaging provides a reliable method to image pelvic structures and soft tissue without ionizing radiation.

Cocaine: effect on spinal projection neurons in the rat.

In the anesthetized rat, systemic cocaine at an analgesic dose (25 mg/kg, IP) had no general influence on spontaneous activity in nociceptive spinoreticular tract neurons or in rostrally projecting low-threshold mechanoreceptive neurons of the spinal dorsal horn. Peripherally evoked activity was moderately (mean: 30%) reduced in 43% (6/14) of the spinoreticular tract neurons, whereas in 50% of them there was no marked change in evoked activity by cocaine. Evoked activity was slightly reduced in 25% (2/8) of the low-threshold mechanoreceptive neurons and not changed in 75% of them. The suppressive effect of a distant conditioning noxious stimulus on responses to spinoreticular tract neurons was enhanced by cocaine in 3/6 of the spinoreticular tract neurons. Primary afferent terminal excitability of A-fibers was slightly increased following cocaine as indicated by the increased amplitude (mean: 24%) of the antidromically evoked compound action potential recorded from the sural nerve. It is concluded that the previously shown marked enhancement of spontaneous activity in the bulborecticular formation is generated supraspinally. Thus, while cocaine-induced analgesia appears to be due primarily to supraspinal mechanisms, the present results suggest that spinal mechanisms are also involved possibly presynaptically.

The effect of medetomidine, an alpha 2-adrenoceptor agonist, in various pain tests.

Medetomidine, a new alpha 2-adrenoceptor agonist produced dose-dependent (30-100 micrograms/kg i.p.) analgesia in the formalin test in rats, and this effect was reversed by atipamezole (1 mg/kg), a new alpha 2-adrenoceptor antagonist. However, medetomidine at the dose of 100 micrograms/kg did not influence tail flick latencies or latencies of the biting response to mechanical pinch stimuli. Moreover, medetomidine produced sedation and a decrease in locomotor activity. In comparison, the non-sedative monoaminergic agent, cocaine (25 mg/kg), produced highly significant analgesic effects in the formalin and mechanical pain tests. The cocaine effect in the formalin test was not reversed by atipamezole (1 mg/kg). It is concluded that the analgesic effect of medetomidine in the formalin test is due to supraspinal mechanisms related to sedation and is mediated by alpha 2-adrenoceptors. The alpha 2-adrenoceptors are not involved in cocaine-induced anagesia.

Effect of subcutaneous formalin treatment on responses to bulboreticular nociceptive neurons in the rat.

The effect of subcutaneous formalin (5%, 0.05 ml) on responses to nociceptive neurons in the medial bulboreticular formation was studied in barbiturate-anesthetized rats. In general, the activity in the studied neurons was not increased following the application of formalin, except for the first few minutes. Concomitantly, no formalin-induced prolonged increase in spontaneous impulse discharge was seen in nociceptive spinal cord neurons with antidromically identified projections to the bulboreticular formation. Also, following formalin application no hypersensitivity was seen in responses of bulboreticular neurons to high-intensity electric stimuli applied to the paw contralateral to the formalin-treated paw. The results suggest that it is not a general property of nociceptive neurons in the medial bulboreticular formation that they are activated in a prolonged fashion by subcutaneous formalin. It is possible that the medial bulboreticular formation is involved in the first rapid phase but not the second prolonged phase of formalin-induced pain.

Mechanical sensibility of the sole of the foot determined with vibratory stimuli of varying frequency.

The mechanoreceptive properties of the sole of the foot were determined by measuring the detection thresholds to vibratory stimuli of 20, 80, and 240 Hz frequency and 300 ms duration. The thresholds were measured at six different sites on the left sole and at toes 1 and 3 with probes of 2 and 8 mm diameter connected to the moving coil of an electromechanical vibrator. The subject sat in an armchair during the experiments, with the left leg supported horizontally by a vacuum cast positioned on a table. Six subjects participated in the experiments. A simple method of limits was used to make the measurements. Lower average thresholds were obtained with higher vibration frequencies, the average thresholds varying between 40-90 microns at 20 Hz and well below 10 microns at 240 Hz. The major decrease in thresholds occurred between 20 and 80 Hz. Interindividual variability in thresholds was large, but the threshold curves obtained from different subjects and from different stimulation points were of the same general shape. The highest thresholds were measured from the toes, but this regional differences in sensibility was obtained only at the higher vibration frequencies. Comparison of the threshold values at the sole with those found with similar stimuli at the thenar eminence and middle fingertip indicates that the mechanoreceptor mechanisms transmitting information about low-frequency vibration in the sole are similar to those in the palmar skin of the hand.

Liminal and supraliminal response characteristics of mechanoreceptive neurons in the cuneate nucleus of cat.

The response characteristics of mechanoreceptive neurons (RA, SA, and PC) innervating the foot pad of cat were determined in the cuneate nucleus. The mechanical stimuli were single sinusoidal pulses of varying frequency (20, 60, 150, and 240 Hz), and vibratory trains of varying frequency (80 and 240 Hz) and duration (50, 100, and 400 ms). Thresholds and stimulus-response functions were determined with single pulses. Absolute thresholds (1 impulse/train), tuning thresholds (1 impulse/cycle), and atonal intervals (the range between absolute and tuning thresholds) were determined with vibratory stimulus trains. When tested with single pulses the thresholds resembled those of primary afferents in all unit populations. The stimulus-response function of PC units but not of all RA units were comparable to those of primary afferents. Noxious conditioning stimulation did not influence the thresholds of cuneate mechanoreceptors in the tested sample (N = 6). Mostly PC units were tested with vibratory trains. Absolute thresholds were not dependent on stimulus duration, which is a consistent finding with peripheral units. In contrast to peripheral units, the tuning thresholds in most PC units were elevated with increasing stimulus duration. The variability in the range of atonal intervals was much larger than in the periphery. Thus, it seems that both the type of the tactile signal and the type of the studied mechanoreceptive neuron are critical parameters in determining whether the response characteristics of neurons in the cuneate and in the periphery are identical or not.

Response variability to repeated mechanical stimulation of the skin in the dorsal column system.

The response variability in the primary afferent fibers and in the post-synaptic neurons of- the cuneatus was determined using repetitive mechanical stimulation of the skin in cat. The response variability was larger in the post-synaptic neurons. Of the two studied mechanoreceptor types, the RA (rapidly adapting) units had significantly more variability at the cuneate level than the PC (Pacinian) units, but at the peripheral level no such difference was found. The results suggest that the PC units transmit signals more securely through the cuneatus than the RA units.