A radionuclide study of regional gastric motility.

The aims of this research were to study some methodological aspects of radionuclide methods for assessing regional gastric motility and to determine the parameters that can be extracted along with their normal values or patterns. During the lag phase, the antral contraction curve showed three different patterns. At the beginning, the antral activity was too low to be analysed. Irregular variation of the count rate was then observed, followed by a more regular contraction. The application of Fourier transformation to the well-defined cyclical count rate variations revealed two areas with high amplitude values but with phase opposition. No peristaltic wave could be identified. After the lag phase, the antral curve showed cyclical variations of count rates with a frequency of about three cycles per minute. Slightly displaced curves but with a much lower amplitude were observed at different parts of the stomach. Several factors were found to influence the antral contraction curve, including the choice of region of interest and time since the last meal. Irregularities in the antral curve, both in terms of frequency and of amplitude, were not unusual in healthy subjects. These should be taken into account when interpreting antral contraction curves. The phase image showed a well-defined peristaltic contraction pattern. Three 360 degrees cycles were usually observed throughout the stomach, suggesting that the time necessary for a peristaltic wave to sweep through from the upper part of the stomach to the antrum is about 1 min. Similar phase images were obtained in all subjects regardless of the amount of time since the meal containing the radioactive tracer, suggesting that gastric peristalsis can easily be assessed and interpreted. The amplitude image showed high amplitude in the antral area and in the greater curvature of the stomach. In the lesser curvature, the amplitude was much lower. Unlike the phase image, however, there was marked variability in the regional amplitude distribution. The value of the regional amplitude distribution for evaluating regional gastric motility is therefore limited.

Estimation of right ventricular ejection fraction by means of 99Tcm-macroaggregates.

A method is described for assessing right ventricular ejection fraction (RVEF) by means of 99Tcm-macroaggregates (MAA). The method consists of performing, in right anterior oblique (RAO) projection, a direct ECG-gated data acquisition over 120 s, as soon as the intravenous administration of the tracer is started. The activity returning to the left heart being negligible, background is limited to the lung activity overlapping the right ventricle. The distribution of lung activity in the gated frames is, however, exactly the same as that in the lung perfusion image, it can therefore be subtracted using static lung scintigraphy acquired directly after the gated study. Considering the count density distributions in the corrected end-diastolic (ED) and end-systolic (ES) frames and the first harmonic phase and amplitude images, ED and ES RV regions of interest (ROIs) are delineated for the calculation of RVEF. It has been shown that using 5 mCi 99Tcm-MAA, the ED count obtained is similar to that usually observed during a 20 mCi 99Tcm first-pass study. Intraobserver variation is acceptable and there is a good correlation between the RVEF calculated by this method and that obtained by means of a steady-state ECG-gated 81Krm technique. As the method presents similar advantages to those offered by 81Krm while using 99Tcm, it constitutes, in our opinion, a good approach for estimating RVEF in routine clinical practice.

Reproducibility of quantitative 99Tcm-MAG 3 measurements in rats.

Repetitive quantitative renal extraction studies of 99Tcm-MAG 3, performed in nine rats, demonstrated excellent reproducibility of successive measurements. These results are better than with 99Tcm-DTPA, due to the higher renal extraction of the 99Tcm-MAG 3. The % of renal uptake 10 min after the injection was not influenced by the elapsed time between the end of the 99Tcm-MAG 3 preparation and its i.v. administration.

Long-term follow-up of separate glomerular filtration rate in partially obstructed kidneys. Experimental study.

An often encountered assumption is that non-relieved renal obstruction will lead soon or late to progressive deterioration of the renal function. The effect of non-relieved partial ureteral obstruction on the separate glomerular filtration rate (SGFR) was studied throughout the whole life of a series of rats, who were submitted at the age of 3 months to partial obstruction of the left ureter. An initial and variable postoperative SGFR decrease was gradually observed, but after this period, SGFR remained stable until the natural death of the animal.

Technetium-99m DMSA imaging and the obstructed kidney.

Although several authors have claimed that the function of an obstructed kidney could be overestimated on Tc-99m DMSA imaging, the clinical importance of such an overestimation has not been well documented. Partial obstruction of one ureter was created in a rat, and a relative Tc-99m DMSA uptake was obtained 4 hours after intravenous injection. By puncture of the isolated obstructed kidney, it was shown that the function of that kidney was overestimated by at least 17%.

A simple data display for qualitative assessment of esophageal transit.

A simple data processing technique for qualitative assessment of esophageal transit is presented and its clinical value is demonstrated.

Oesophageal transit of liquid: effects of single or multiple swallows.

The effects of single and multiple swallowing on oesophageal transit have been evaluated in healthy subjects. It was shown that the transit patterns observed after multiple swallowing were different from that observed after a single swallow. It was concluded that for the detection of oesophageal transit abnormalities, the test should be performed using a single swallowed bolus.

Sensitivity of cortical transit and furosemide response in the diagnosis of renal obstruction. An experimental model.

Several radionuclide parameters are routinely used for the diagnosis of renal obstruction. In order to evaluate the sensitivity of those parameters, an experimental model of partial ureteral obstruction in rats was used. Neither the cortical transit time, nor the response to furosemide could serve to discriminate between obstructive and nonobstructive kidneys. These parameters were, however, more or less related to the degree of impairment of the single kidney glomerular filtration rate and should probably be considered as functional parameters reflecting the grade of the obstructive phenomenon.