A single sample method for evaluating 51chromium-ethylene diaminic tetraacetic acid clearance in normal and hyperthyroid cats.

BACKGROUND: Chronic kidney failure is frequently seen in middle-aged and elderly cats. 51Chromium-ethylene diaminic tetraacetic acid (51Cr-EDTA) clearance and single blood sample (SBS) method are used in several species to estimate the glomerular filtration rate (GFR). HYPOTHESIS: The hypothesis of this study was that 51Cr-EDTA clearance could be determined using an SBS method in normal and hyperthyroid cats. ANIMALS: Forty-six cats were included in this study, with an average age of 9.5 years. Of these cats, 27 had hyperthyroidism; 19 were healthy. METHODS: After IV injection of 51Cr-EDTA (average dose: 4.25 MBq), 7 blood samples were obtained between 5 and 240 minutes. Reference clearance was calculated in mL/min and mL/min/kg body weight, using a 2-compartment model. Optimal time for clearance measurement with SBS was then determined by systematically comparing each individual plasma concentration to the reference multisample clearance. RESULTS: The average reference plasma clearance of 51Cr-EDTA for all cats was 14.9 mL/min (3.7 mL/min/kg). The clearance in hyperthyroid cats averaged 16.4 mL/min (4.3 mL/min/kg) and in normal cats averaged 10.3 mL/min (2.4 mL/min/kg). The optimal time for the SBS was 48 minutes after injection of tracer 51Cr-EDTA (R2= 0.9414), giving the following converting equation: clearance = (0.0066 x DV48 minutes) - 0.9277 (in mL/min). CONCLUSIONS AND CLINICAL IMPORTANCE: In this study, the single sample 51Cr-EDTA clearance method was used to estimate the global GFR in cats. The method identified differences in clearance between normal and hyperthyroid cats. The optimal time for an SBS was 48 minutes.

Revisiting normal (51)Cr-ethylenediaminetetraacetic acid clearance values in children.

PURPOSE: Normal (51)Cr-ethylenediaminetetraacetic acid (EDTA) clearance values as a function of age were published a number of years ago. These values were based on data from children with a normal left to right ratio and a normal appearance on DMSA scintigraphy, despite the presence of an acute renal infection. At that time, the authors were unaware that hyperfiltration is a common phenomenon in patients with acute renal infection and that their normal values could have been significantly overestimated. The present work therefore aimed to re-appraise these normal values. METHODS: In a first step, in order to verify the previous results, the same type of population was selected, namely patients with present or past urinary tract infection but normal images and a normal left to right ratio on DMSA scintigraphy. In a second step, the selection was based on patients who had had no recent urinary tract infection. In both series, a single blood sample method was used for the evaluation of (51)Cr-EDTA clearance. RESULTS: In the first group of patients, the results obtained were almost identical to those previously published. In the second group of patients, the results were significantly lower: after 2 years of age, the mean GFR value was 104 ml/min/1.73 m(2) (10th and 90th percentiles 81 and 135 ml/min/1.73 m(2), respectively), compared with 117 ml/min/1.73 m(2) in the first group. CONCLUSION: The data of the second group are probably more representative of the true normal GFR values and can be applied to the entire paediatric population.

Estimation of glomerular filtration rate in infants and in children using a single-plasma sample method.

This work was undertaken to look for distribution volume-plasma clearance converting equations(s) that can be used to estimate glomerular filtration rate (GFR) in children. GFR calculated using the two-blood sample slope-intercept method was used for comparison. It was shown that the 2-hr distribution volume and the two-blood sample clearance were closely related. For all the age groups, the coefficient of correlation between these two parameters was high (range: 0.95 to 0.99) and the s.e.e. was low (range 0.76-3.86 ml/min). It was also shown that a linear equation (GFR = 2,602 V120-0,273) could be used to convert the two hour distribution volume into an accurate estimate of two-blood sample GFR whatever the age of the patient. The use of the single-sample technique for measuring GFR in children is therefore recommendable.

Relative 99mTc-MAG3 renal uptake: reproducibility and accuracy.

UNLABELLED: The aim of this study was to estimate the reproducibility and accuracy of 99mTc-mercaptoacetyltriglycine (MAG3) relative percentage uptake. METHODS: Reproducibility was evaluated on healthy volunteers who were submitted twice to a 99mTc-MAG3 renographic study, which used different uptake algorithms, different background corrections and different time intervals. Accuracy was evaluated in a group of patients with symmetrical or asymmetrical relative renal function, who underwent both 99mTc-dimercaptosuccinic acid (DMSA) and 99mTc-MAG3 studies, using the DMSA relative percentage uptake as a reference. RESULTS AND CONCLUSION: The methods that combined the best reproducibility and accuracy for estimating 99mTc-MAG3 left-to-right uptake ratio were the integral method, with subrenal or perirenal background correction, and the Patlak-Rutland plot. The use of the integral method without background correction introduced a systematic bias, whereas the slope method resulted in high variability. Therefore these methods cannot be recommended.

Feasibility of estimating glomerular filtration rate in children using single-sample adult technique.

UNLABELLED: This work was undertaken to verify whether a single-sample adult technique, when applied using body surface-corrected plasma concentration, can be used in place of specific pediatric method to estimate 51Cr-EDTA renal clearance in children. METHODS: In a series of 90 children (aged 0.1 to 15 yr). 51Cr-EDTA renal clearance was calculated using for different approaches. The first approach used specific pediatric single-sample methods; three techniques were chosen and they all used 120-min plasma concentration. The second approach used the same three specific pediatric methods, but they were applied using 120-min plasma concentration prescaled for 1.73 m2 body surface area. The third approach used single-sample methods designed for adults; three methods were again chosen. They all used 240-min plasma concentration. The fourth approach used the same adults algorithms, but they were applied using 240-min plasma concentration prescaled for 1.73 m2 body surface area. RESULTS: Clearances calculated using the three specific pediatric methods were all closely cross-correlated regardless of whether or not the plasma concentration was prescaled. The use of classical adult methods produced in some cases obviously erroneous clearance values. Improvements were observed when the same adult methods were applied using prescaled plasma concentration. Nonetheless, the clearance values obtained only fairly correlated with those obtained using specific pediatric methods. CONCLUSION: The single-sample adult technique using plasma concentration prescaled for 1.73 m2 body surface area cannot be used in place of a specific pediatric single-sample method to estimate 51Cr-EDTA renal clearance in children.

Gastroesophageal scintiscanning in children.

Four patients' positions were tested in search of increased sensitivity of gastroesophageal scintiscanning for the detection of reflux in children: supine, prone, left lateral, and 30 degrees right posterior oblique. The sensitivity was highest when the child was placed in supine position. A 60-min recording period increased the sensitivity of the technique, and is thus preferred to a shorter recording time.

Effect of background correction on separate technetium-99m-DTPA renal clearance.

The estimation of the background constitutes the main difficulty in the accurate determination of the separate renal clearance, using the 99mTc-DTPA complex and the gamma camera. This is due to the low extraction rate of DTPA, giving an unfavorable signal-to-noise ratio, and to the fact that no background area can accurately represent both interstitial and vascular components of the renal curve. Several algorithms have been proposed in the literature for solving the problem of background but their effect on the calculated clearance value has not been sufficiently assessed. In this paper, it has been possible, using a theoretical approach, to predict the respective influence of the different algorithms on the renal clearance. These results were confirmed on the basis of clinical data obtained from 53 renal studies. It was shown that a double background correction, using successively the area ratio method followed by a linear fit method, is probably the most precise method and is less dependent on the choice of the background area.

Radionuclide quantitation of left-to right cardiac shunts using deconvolution analysis: concise communication.

Quantitative radionuclide angiocardiography (QRAC) was performed with and without deconvolution analysis (DA) in 87 children with various heart disorders. QRAC shunt quantitation was possible without DA in 70% of the cases and with DA in 95%. Among 21 patients with prolonged bolus injections, quantitation of the shunt was possible in 52% of the cases without DA an in all cases with DA. Correlation between oximetry and QRAC with DA was better than between oximetry and QRAC without DA. It is concluded that QRAC with DA is a more reliable, noninvasive means for detection and quantitation of left-to-right cardiac shunts than QRAC without DA.

Overall and single-kidney clearance in children with urinary tract infection and damaged kidneys.

UNLABELLED: The overall and single-kidney clearance in children with acute urinary tract infection was investigated retrospectively using the combination of the relative 99mTc-dimercaptosuccinic acid (DMSA) uptake and the 51Cr-ethylenediaminetetraacetic acid clearance. METHODS: There were 180 patients with both normal kidneys, 56 with clear unilateral abnormalities on DMSA scintigraphy and 11 with two abnormal kidneys. Half of the patients were younger than 2 y, and because of the progressive maturation of the renal function, they were not considered in the analysis of the absolute overall and single-kidney clearance; nevertheless, they were included in the analysis of the relative DMSA percentage uptake. RESULTS: When only one kidney was affected on DMSA scintigraphy, the clearance of the affected kidney was lower than on the normal side and often abnormally low. In these unilaterally affected kidneys, contralateral compensation mechanisms tended to occur, resulting in preservation of overall clearance. This compensation was probably not present only on the contralateral side. On the abnormal side, the clearance was normal in about half of the cases, probably because of intrarenal compensation occurring in regions not damaged by the infection. In addition to these compensation mechanisms, hyperfiltration was probably present in many cases of acute urinary tract infection with intact or unilaterally damaged kidneys.

Overall accuracy of technetium-99m-MAG3 clearance measurements obtained with a gamma camera heart curve.

UNLABELLED: The aim of the present study was to evaluate the accuracy of 99mTc-MAG3 clearance measurements using a precordial gamma camera curve calibrated by a single plasma sample. METHODS: Technetium-99m-MAG3 was administered to ten young normal volunteers. A 60-min gamma camera acquisition was performed. Five different segments of the gamma camera curve were determined: 3 min to 20 min, 3 min to 30 min, 3 min to 40 min, 3 min to 50 min and 3 min to 60 min. A biexponential function was fitted on each of these five different segments, which were thereafter calibrated using eight different blood samples. These blood samples were successively used for calibration at 5, 10, 15, 20, 30, 40, 50 and 60 min. The single injection, multiple plasma sample method was used as reference. RESULTS: Camera clearances varied markedly based on the length of the precordial curve and on the time of the calibration sample. Different regression equations were obtained for each duration of the camera curve, and for each blood sample timing. Correlation coefficients were > 0.95 in most cases recording period of at least 50 min, however, was necessary to obtain a s.e.e. better than those obtained using a single blood sample method without gamma camera curve. CONCLUSION: The 99mTc-MAG3 clearance determination using a gamma camera heart curve calibrated with a single blood sample does not necessarily improve the accuracy of the one blood sample method.

Renal technetium-99m-DMSA SPECT in normal volunteers.

UNLABELLED: Dimercaptosuccinic acid (DMSA) renal scintigraphy today is considered a sensitive and useful technique for the detection of cortical abnormalities. Recent studies have suggested that lesion detection can be improved by SPECT imaging. This study investigated normal kidneys using different SPECT modalities. METHODS: Ten young, healthy volunteers with normal clinical history and normal renal ultrasound underwent planar and SPECT DMSA imaging 2 to 4 hr after intravenous injection of 99mTc-DMSA (185 MBq). Analysis of SPECT data was focused on the homogeneity of cortical uptake (comparison of upper and lower pole activity) as well as on the presence or absence of focal cortical defects. RESULTS: No abnormality could be observed on the planar images. SPECT revealed, in seven kidneys (five left and two right), the presence of a hypoactive upper pole. This was visually observed on the coronal slices with up to 35% difference between upper and lower pole. Moreover, three focal cortical defects were visualized on the coronal slices as well as on three-dimensional surface shade displays. CONCLUSION: These normal patterns should be recognized when evaluating a patient with possible renal involvement.

Detection of bilateral and symmetrical anomalies in technetium-99m-HMPAO brain SPECT studies.

The detection of bilateral and symmetrical regional cerebral blood flow (rCBF) abnormalities requires knowledge of the antero-posterior rCBF distribution in normal subjects of all age groups. These data are very difficult to obtain in children for ethical reasons and in older subjects because of the necessity of recruiting a large number of healthy volunteers from each age group. Therefore, to obtain normal values of antero-posterior rCBF distribution, we have retrospectively selected a group of patients with a low probability of having cerebral lesions, whose 99mTc-HMPAO brain SPECT studies were analyzed semiquantitatively. Cerebellum/mean cerebral cortex index when compared to young adults was higher in the neonatal period, slightly lower between 2 mo and 15 yr, and more or less identical after 15 yr. Cortico/occipital indexes exhibit considerable changes during the first year of life due to important differences in maturation timing of cerebral cortical areas. After 1 yr, all cerebral cortical areas approximately displayed a parallel evolution. A slight increase in fronto/occipital and temporo/occipital indexes was, however, still observed during childhood, while in elderly subjects there was a trend towards a decrease in all cortico/occipital indexes (particularly in prefrontal and motor areas). Changes that occurred after 1 yr were, however, usually smaller than interindividual variation. Despite the large range of "normal" values, the antero-posterior analysis could be useful in various neurologic disorders, because it allows detection of symmetrical rCBF anomalies undiagnosed by the right-left analysis.

Normative data for lumbar spine bone mineral content in children: influence of age, height, weight, and pubertal stage.

In 136 normal growing children between the ages of 1 and 18 yr, bone mineral content (BMC) at the level of the lumbar spine (L2-L4) was determined with a commercial dual-photon absorptiometer. BMC was calculated as BML (BMC per unit length) and BMD (BMC per unit surface). The mean lumbar spine BML of the studied children (2.53 +/- 0.86 gHA/cm) was significantly lower than the spinal mineral content of adults (4.26 +/- 0.57 gHA/cm). No sex difference existed in lumbar spine BMC. BML as well as BMD were highly dependent on age, body height, and body weight. During the prepubertal years, BML and BMD increased in a fairly rectilinear pattern. During puberty, BMC increased more rapidly: 40% for BMD and 77% for BML. For the entire group, the increase in BMC with age, height, and weight was best predicted by an exponential regression line analysis.

Evaluation of the accuracy of steady-state krypton-81m method for calculating right ventricular ejection fraction.

The accuracy of a steady-state 81mKr method for calculating the right ventricular ejection fraction (RVEF) has been examined in this study. Causes of errors using this method and their effects on the calculated RVEF were evaluated. The results suggested that mixing in the right ventricle during continuous infusion of 81mKr was homogenous, allowing for the calculation of ejection fraction using the count rate ratio. Lung activity was quite important and could not be neglected in computing RVEF, but the use of [99mTc]MAA lung perfusion scanning seemed to allow a correct subtraction of this background activity. The delineation of right ventricular regions of interest (ROIs) was complicated by the translation movements of the right ventricle during heart contraction. These ROIs should be drawn carefully on the count density distribution images and data shown by parametric images; such as first and second harmonic phase, amplitude images, and composite stroke volume image should be considered. Furthermore, this study demonstrates the superiority of the 81mKr technique compared with 99mTc methods for computing RVEF. In conclusion, even if the true accuracy of the 81mKr method for calculating RVEF cannot be proven due to the lack of reference methods, strong, suggestive evidence that the technique should be accurate is shown here.

Interobserver reproducibility in reporting on 99mTc-DMSA scintigraphy for detection of late renal sequelae.

UNLABELLED: This study was designed to evaluate the interobserver variability in reporting on 99mTc-dimercaptosuccinic acid (DMSA) scanning performed 6 mo after an acute episode of pyelonephritis for the detection of late renal sequelae. METHODS: Forty-six children were selected, who had early and late DMSA studies for evaluation of acute pyelonephritic lesions as well as sequelae. Three observers reported independently and separately on the early and late DMSA scans and, in a second step, on the late scan in the presence of the early scan. Interobserver reproducibility was evaluated for the early DMSA scan, the late DMSA scan alone, and the late DMSA scan with the early scan for comparison. RESULTS: Complete agreement between the three observers was reached in 75%, 78%, and 77% for the early DMSA scan, the late DMSA scan alone, and the late DMSA scan with the early scan for comparison, respectively. CONCLUSION: Interobserver reproducibility was high and was comparable for both early and late DMSA scintigraphy.

Regional brain blood flow in congenital dysphasia: studies with technetium-99m HM-PAO SPECT.

Congenital dysphasia is a developmental speech disorder not explained by deafness, phonation disorder, mental retardation, neurologic lesion, or psychiatric disease. The existence of brain lesions has often been postulated but conventional investigations fail to demonstrate any cerebral abnormality. By means of [99mTc]hexamethyl-propyleneamine oxime (HM-PAO) brain single photon emission computed tomography (SPECT) we have studied 14 children suffering from congenital dysphasia. The brain computed tomographic scan was normal in all cases. In two patients with expression impairment the SPECT study demonstrated a hypoperfusion in the inferior frontal convolution of the left hemisphere, involving the Broca's area. In nine of 12 patients with global dysphasia (deficits in both comprehension and expression), SPECT study showed two hypoperfused areas: an abnormality in the left temporoparietal region and a hypoactivity in the upper and middle areas of the right frontal lobe. These results suggest that congenital dysphasia could be due, like acquired aphasia, to specific impairment of the language cerebral areas and that brain SPECT studies with [99mTc]HM-PAO could be useful for a better comprehension of the physiopathology of these disorders.

Functional imaging of brain maturation in humans using iodine-123 iodoamphetamine and SPECT.

The application of regional cerebral blood flow (rCBF) study by means of lipophilic radiotracers and single photon emission computed (SPECT) devices in very young infants is hampered by the considerable changes of rCBF pattern as a result of the cerebral maturation process. In an attempt to determine the normal evolution of [123I]IMP SPECT pattern as a function of age, we retrospectively selected the studies of 30 babies with normal clinical examination, EEG and CT or ultrasound scans at time of SPECT. There was a marked predominance of the thalamic perfusion over cortical areas until the end of the second month. The distribution of regional cortical activity followed a strict sequence. The perfusion of both parietal and occipital areas was well-visualized around the 40th week of gestational age and thereafter rapidly rose, always, however, with a slight predominance of the parietal activity. At the opposite, frontal activity which remained scarcely recognizable up to the second month tremendously rose to present the adult-like pattern at the beginning of the second year. The rCBF changes described above are well in agreement with the behavioral evolution occurring during prime infancy.

Prediction of cerebral palsy in high-risk neonates: a technetium-99m-HMPAO SPECT study.

In infants who have experienced prenatal or perinatal injury, it is often difficult, on the basis of clinical examination and conventional investigations (electroencephalogram, cranial ultrasound scan), to diagnose those with brain damage and to predict the type and the severity of subsequent neurological handicaps. We investigated the predictive value of 99mTc-HMPAO brain SPECT performed in the first weeks of life in high-risk neonates. Right-left asymmetries in tracer uptake had no predictive value, regardless of their localization or severity. On the other hand, a change in antero-posterior rCBF distribution was found in 7/10 of neonates with adverse outcome (death, major neurological sequelae) and in none of the 78 neonates with no major motor neurological sequelae. Compared to conventional investigations, 99mTc-HMPAO brain SPECT did not provide additional predictive information when neurological examination, electroencephalogram and cranial ultrasonography were all normal or all abnormal. Conversely, in the 30 patients with anomalies on one or two of the above investigations, SPECT showed an abnormal antero-posterior pattern in 4/6 neonates with major neurological sequelae and no change in the antero-posterior rCBF distribution in the 24 infants who developed normally. In conclusion, our results suggest that 99mTc-HMPAO brain SPECT, when performed in the first weeks of life, can be useful in high-risk neonates to predict occurrence of major neurological handicaps. Because of the relative invasive character of HMPAO scan in neonates and the overall accuracy of the noninvasive tests, radionuclide examination should not be performed in every high-risk neonate. According to our results, 99mTc-HMPAO brain SPECT might be indicated in those children where noncongruent results were obtained with conventional studies.

Critical evaluation of lung scintigraphy in cystic fibrosis: study of 113 patients.

A long-term study has been performed on 285 lung perfusion scintigrams obtained from 113 patients with cystic fibrosis. Transverse and longitudinal comparisons with clinical and radiological scores, as well as retrospective analysis of the deceased patients, were the methods used in order to evaluate the importance of the scintigraphic images. It appears that lung scintigraphy is the best index of the regional lung impairment, and contributes, as does a chest radiograph, to the early detection of lung lesions, the two methods being complementary. The survival rate of CF patients reached 0.80 at 9 yr when initial scintigraphy was normal or only moderately impaired, but fell to 0.18 when severe lesions were seen on the first scintigrams.

Report of the Radionuclides in Nephrourology Committee on renal clearance.

The need for simple and accurate methods to measure renal function is self-evident. This need increases as techniques for intervention become available. The demand for evaluation of individual kidney function has increased with its role in the diagnosis and follow-up of unilateral renal disease and in decision making for conservative or surgical treatment based on residual renal function. The role of nuclear medicine in this area has been inhibited by confusion about conflicting methodologies. This report is meant to provide guidance to those centers that would like to initiate clearance procedures but have difficulty in choosing appropriate methodology.