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The physical characteristics of krypton-81m makes it particularly suited for the study of right ventricular function, but its ultrashort half-life (13.3 s) precludes in vitromeasurements of blood pool specific activity needed for count based determination of ventricular volumes.

SummaryRepetitive 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.

By exploiting the ultrashort half-life 191Irmas tracer for left ventricular first-pass angiocardiography and 201T1 as myocardial perfusion agent, direct comparison between myocardial perfusion and regional wall motion was obtained during the same exercise stress test in patients with non-significant coronary artery disease, in patients with recent myocardial infarction, and in patients six weeks after successful percutaneous transluminal coronary angioplasty (PTCA). A good agreement between regional myocardial perfusion and regional wall motion was observed in patients with non-significant coronary artery disease and in most patients with recent myocardial infarction. In contrast, discrepancies occurred at maximal exercise in patients studied six weeks after successful PTCA: only 38 of the patients with no evidence of restenosis and with a completely normal myocardial perfusion scintigraphy had a normal regional wall motion at maximal exercise stress. According to these results, a normal uptake of 201T1 six weeks after PTCA would mean that the circulation has been successfully re-established but without predicting the functional capacities of the myocardial cells which remain altered at least six weeks after the revascularization procedure in about two-thirds of the patients. We conclude that 191Irmin combination with 201T1 offers the opportunity of performing myocardial perfusion and wall motion studies simultaneously both at rest and during exercise.

Increasing interest in bone mass has led to dedicated commercial dual photon absorptiometry (DPA) instruments. We describe a method for the measurement of the mineral content of the lumbar spine using a scintillation camera. The most appropriate source(s) and collimator were investigated. An especially constructed arm placed the sources in the focal point of a converging collimator. Two single-peak sources, 99Tcmand 241Am, were used instead of dual-peak 153Gd source. Phantom studies showed no degradation of the results in water depths of up to 26 cm. Acquiring 10 Mcounts per image over a 300 cm2field, a coefficient of variation (c.v.) of 1.7 was obtained. Reducing the total counts per image to 1 Mcount gave rise to a c.v. of 6.2. Long-term measurements showed a c.v. of 1.1 for density, with a mean value of 0.98 gHa cm−2compared to 0.90 for a commercial DPA instrument. Repeated measurements of the lumbar spine on 10 patients with a 2 week interval showed a c.v. of 5. Comparative measurements were made between the scintillation camera and a commercial DPA instrument on six volunteers. Systematic higher results, similar to those observed with the phantom, were obtained with the scintillation camera. The reproducibility on a phantom and in patients is in the same range as commercial DPA instruments. The low cost related to the use of standard nuclear medicine equipment and to inexpensive radioactive sources represent definite advantages.

The aim of this study was to evaluate the variability of the Patlak-Rutland slope as applied to the renal clearance method. We analysed the 99Tcm-mercaptoacetyltriglycine renograms of 17 non-selected patients (both children and adults, number of kidneys = 34) with a single kidney glomerular filtration rate of 6–73 ml min-11.73 m-2. The acquisition time for the renograms was 20 min with a frame duration of 20 s. First, correction for background activity was introduced using the perirenal area and the size ratio between the kidney and the perirenal area. The Patlak plot was then applied. The first two points were systematically rejected and a series of linear fits calculated from the experimental points, starting from the third point (i.e. 1 min). The final point of the fit never exceeded the time of the peak of the renogram minus one minute (Tmax- 1) and was always less than 5 min. Although simple visual inspection of the slopes would suggest that the experimental points were distributed accurately along a straight line, it appeared that the slope was strongly dependent on the number of points used for the determination of the fit. As a second step, we restricted the number of points for fitting to the time interval between 1 min and 2 min 40 s. This procedure appeared to show that the Patlak methodology is reliable, giving rise to only small variations in slope, depending on the number of points chosen. However, even in this narrow time interval, significant errors can be made, either because of the very early escape of the radionuclide or because of statistical noise (e.g. in renal failure the signal-to-noise ratio is unfavourable). Therefore, it is advisable, when using this methodology, to restrict the fitting procedure to the second minute of the study and to check visually that this fixed time interval gives rise to a slope that is well adapted to the Patlak plot.

Bile duct ligated rats (n=7) have been investigated for 6 months. Two patterns of evolution have been observed: (i) progressive development of cirrhosis and portosystemic shunt (detected by 201Tl per rectal scintigraphy) in three animals, (ii) repermeabilization of the biliary tract in four animals. Despite the small number of animals investigated, the 201Tl per rectal scintigraphy seems to be a good indicator of portosystemic shunt secondary to biliary cirrhosis.

An international project was set up to study the clinical usefulness of intrarenal transit times derived from the renogram by deconvolution. A common data sheet, to collect clinical, biochemical, radiological and isotopic information, was completed by the centres.Five hundred and ninety-one patients were studied and the results analysed. The mean transit time (MTT) in normal kidneys was found to be 3.6±1.1 min. If the MTT is greater than 7.6 min, a kidney is likely to be obstructed. In vesico-ureteric reflux, the transit times are prolonged, but they are normal in infection, hypertension, parenchymal disease and minimally irradiated kidneys. In transplantation, when the kidney is normal, the transit times are shorter than in the natural kidney; in acute rejection, transit times are prolonged.

The aim of this study was to assess the reproducibility of a number of simplified clearance methods using chromium-51 ethylenediamine tetraacetic acid (51Cr-EDTA) and to compare these with the multiple blood sample technique. Twenty-four healthy volunteers were enrolled into the study. The test was performed twice, 1 week apart and under similar physiological conditions. After intravenous injection of the tracer, 13 blood samples were taken between 5 and 240 min. The reference clearance was calculated after adapting a bi-exponential fit on the whole plasma disappearance curve. Simplified methods included the slope intercept method using different combinations of blood samples (2 and 4 h; 2, 3 and 4 h; 1.5, 2, 3 and 4 h; 1.5, 2 and 3 h) and several single clearance methods (Constable 3 h; Groth 3 h; Groth 4 h). The standard deviation of the differences between the first and second measurements were similar for all methods, confirming the comparable reproducibility of these methods.

The aim of this study was to test the reproducibility of the second exponential of the plasma disappearance curve of 51Cr-EDTA and to compare it with the single slope-intercept method. The test was performed twice among 24 young healthy volunteers at an interval of 8 days and under similar physiological conditions. After the intravenous injection of 3.7 MBq of 51Cr-EDTA, four blood samples were taken between 1.5 and 4 h and combinations of two, three or all four of these were used to calculate the slope of the plasma clearance curve. The clearances rates were calculated using these slopes and the corresponding intercepts of the slopes with the y-axis. The standard deviation of the differences between the first and the second measurements was between 8 and 10 for the different clearance estimates, and between 11 and 17 for the different slope estimates, reflecting the wider variability of the slope estimate. Using the first series of measurements, the change of timing for blood sampling introduced a wider variability for the slope estimate than for the clearance estimate.

In recent years,*I-MIBG (*I-metaiodobenzylguanidine), which is transported and stored in the chromaffin cells, has been shown to allow good visualization of neuroblastomas in children. This paper deals with 30*I-MIBG-scans performed in 20 children: 16 with neuroblastoma, 3 with retinoblastoma, and 1 with a malignant paraganglioma. A high detection rate was found for both primary and secondary sites of neuroblastoma.*I-MIBG was generally superior to99mTc-MDP bone scintigraphy in the detection of bone metastases. Our experience illustrates the unique place of*I-MIBG-scintigraphy compared with other imaging techniques: it makes it possible to define the nature of the tumour, particularly in cases with normal catecholamine levels; to establish how extensive the lesions are at the time of diagnosis; and to confirm complete remission. No abnormal*I-MIBG uptake was noted in the 3 cases of retinoblastoma.