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Objectives: I-123 ioflupane (FP-CIT) single-photon emission computed tomography is a recognized tool in the diagnosis of Parkinsonian syndromes. In practice, data interpretation relies on visual and semiquantitative analyses. Good interobserver reproducibility is a prerequisite before claiming the robustness of a technique. This study aimed at evaluating interobserver reproducibility of this approach. Methods: Thirty nuclear medicine physicians participated in the study. Data included FP-CIT images and semiquantitative measurements of 12 cases, covering a wide spectrum of scintigraphic patterns and for which a 'true' clinical diagnosis based on long-term follow-up was available. Interobserver agreement was defined, for each case, as the highest percentage reached among the three proposed answers with complete agreement arbitrarily set at 80% or more. Variability in an individual observer's sensitivity to assess data as normal, equivocal or abnormal was scored using a three-point scale. Results: Response rate was 99.7%. Among the three possible answers, 'normal' accounted for 41.2% of the total, 'abnormal' for 49.8% and 'equivocal' for 8.1%. The mean interobserver agreement was 76% (range: 37-100%), with complete agreement being reached only in five cases. The interpretation proposed by most observers accorded to clinical diagnosis in 75% of the cases. Abnormalities of the central nervous system were encountered in all the cases with disagreement between the observer's interpretation and clinical diagnoses. An important variability in the observers sensitivity was seen. Conclusion: In the particular setting of this preliminary study evaluating the reproducibility of FP-CIT single-photon emission computed tomography interpretation in a group of nuclear medicine physicians with various experiences, interobserver agreement was suboptimal. Collegial discussion and standardized interpretation criteria could contribute to an improved reproducibility. © 2010 Wolters Kluwer Health

Objective To evaluate the interobserver reproducibility in reporting on technetium-99m (Tc-99m) dimercaptosuccinic acid (DMSA) scan in children. Methods Sixty Tc-99m-DMSA scans, issued from three centres, were distributed by e-mail to nuclear medicine physicians from the five continents interested in paediatric nuclear medicine. Observers had to choose, for each kidney, among four answers: normal, abnormal, equivocal or poor quality. An additional question was the location of the lesion if any: upper part, mid part, lower part. The responses had to be returned by e-mail. Results Sixty-one observers, with an experience of approximately five or more Tc-99m-DMSA/month, contributed to the study. Median agreement was 93%. The agreement was less than 80% in 29 kidneys (24%) but only in 13% (16 kidneys) was there disagreement between normality and abnormality, the remaining cases being related to 'equivocal' responses. Disagreement was mainly related to the following patterns: (i) normal variants: pear-shaped kidney, hypoactive poles contrasting with important parenchymal mass, triangular kidney, unusual shape of the columns of Bertin; (ii) congenital abnormalities: hydronephrosis, normal duplex kidney; (iii) small defects. Conclusion Interobserver reproducibility can be considered as good among a wide number of observers from the five continents. Disagreement among observers could be reduced by taking the normal variants into account.

To verify the applicability of a recently described resolution-independent method for the semi-quantification of 123I-FP-CIT scans.Visual interpretation, 'conventional' and resolution-independent semi-quantification was performed on 60 123I-FP-CIT scans. Using ROC analysis, the results were compared to the final clinical diagnosis after a follow-up of at least 18 months. Sensitivity and specificity values were calculated and a cut-off value of the specific binding, which differentiated between normal and abnormal scans with high sensitivity and specificity, was given.Application of the resolution-independent method to a new set of 123I-FP-CIT SPECT data yielded a cut-off value of the specific striatal binding of 55 ml. Corresponding values of sensitivity and specificity were 95% and 72%, respectively. Further, based on the values of the area under the ROC curve and the 95% confidence interval of different semi-quantitative methods, the resolution-independent semi-quantification agreed best with the final clinical diagnosis.We found a similar value of the specific 123I-FP-CIT binding as the one previously described in the literature, which proved the validity of the resolution-independent method. Further, this method, among other 'conventional' semi-quantitative methods, agreed best with the final clinical diagnosis. For this reason we recommend its use to aid in the diagnostic process.

BACKGROUND: The slope-intercept method is widely used for the determination of the plasma clearance of Cr-EDTA. When three or more plasma samples are used, the goodness-of-fit (r) can be used as a measure of consistency of the samples. This parameter can not be used, however, if only two samples are available. PURPOSE: To evaluate whether the single-sample technique (SBS) can be used to check the consistency of the slope-intercept method using two blood samples (2BS) in children. METHODS: Simulated computer models of a mono-exponential curve were created in order to represent three children aged 3, 6 and 10 years, each with a large range of clearances values and three distribution volumes, respectively 20%, 25% and 30% of body weight. Errors were then introduced in the injected dose (errors from -50% to +50%) and on the 120 or 240 min blood sample (errors from -50% to +50%). The effects of these errors on the clearance measurement using 2BS and SBS methods were calculated and compared. RESULTS: The errors on the injected dose, the 120 min and 240 min plasma samples introduced errors in the same direction and with the same magnitude on both the SBS and 2BS clearance values. For that reason, the comparison between the SBS methods and the 2BS techniques has a low sensitivity in detecting an eventual error. Striking differences between the SBS method and the 2BS technique were only observed when considerable errors on the injected dose or plasma samples were introduced, particularly in case of a reduced clearance. The comparison between the SBS clearances calculated using the 120 min sample to that obtained using the 240 min samples is slightly more sensitive. However, this approach is also slightly less specific. A difference of more than 10 ml·min·1.73 m can be observed in the absence of an error. CONCLUSIONS: The use of the SBS for checking the consistency of the 2BS constitutes an insensitive approach to detect an eventual error in the injected dose or in the plasma samples. Obvious different results obtained by SBS and 2BS or between the SBS calculated using the 120 min and the 240 min samples suggest the presence of an error, but comparable results do not exclude erroneous measurement. Moreover, a difference of more than 10 ml·min·1.73 m can be observed in the absence of an error in the injected dose or in the plasma samples. © 2007 Lippincott Williams & Wilkins, Inc.

Renal transit estimation using renography has been employed for decades. A variety of methods have been developed, ranging from simple quantitative to more sophisticated techniques. In this review, the methods are discussed in perspective of their advantages and drawbacks. Finally, the most robust methods for estimation of renal transit are proposed.

Background Human planning is a complex mental process that may be evaluated by the 'Tower of London' (TOL) task, which includes setting up and maintaining multiple subgoals at the same time. Although positron emission tomography and functional magnetic resonance imaging have provided reliable data on the recruitment of a neural network engaged in planning tasks, the experimental settings of these studies cannot be applied in clinical conditions. Hence, this study reports on the TOL task under classical neuropsychological test conditions using single photon emission computed tomography (SPECT) activation in 10 healthy subjects. Methods Participants first performed a control task and then an activation task, i.e., the TOL planning task In the planning task, subjects were required to change, in the minimum number of moves possible, an initial arrangement of beads to match a goal arrangement. Subjects solved a set of eight TOL problems of increasing difficulty. A control task was designed such that it eliminates planning abilities, which is the process of interest. Planning times and accuracy were measured as performance parameters and functional imaging data were analysed with statistical parametric mapping (SPM99) to determine significant voxel-wise activations between the planning task and the control task. Results Both overall and for each difficulty level, measures of accuracy were within the normal range. Similar results were found for the overall thinking time and thinking times of each difficulty level. That is, performance of the healthy subjects during the TOL task replicated the typical pattern of results found with appropriate control samples in the literature. Also, activation of the right prefrontal cortex was consistent with other functional imaging results, thereby validating the use of the TOL task in a SPECT activation paradigm. Conclusions Based on the present study it may be concluded that the close resemblance of the test conditions of the SPECT activation procedure with those of the TOL task in the investigation room constitutes a major advantage for future application of the SPECT activation procedure in clinical conditions.

The split renal function, obtained using Technetium 99m mercaptoacetyltriglycine renography, is currently considered as a robust, accurate and reproducible parameter, provided that it is calculated at a time when no escape of the tracer from the kidney has occurred. The question arises as to whether the simultaneous administration of furosemide with the tracer (F0 test) might accelerate the escape of the tracer, resulting in an underestimation of the split renal function. From a large database, we selected 36 clinically stable children in whom both F0 and F+20 (administration of furosemide 20 min after the tracer) diuretic renography had been performed. In all cases, the F+20 test preceded the F0 test. The mean interval between the two tests was 17 months. The split renal function was calculated on the basis of the 1-2 min background-corrected renal activity using the integral method, slope method and Rutland-Patlak plot. In order to evaluate the effect on the split renal function of an early escape of the tracer, the patients were analysed according to the T(max) value of the renogram for both the F0 and F+20 tests. For the F+20 test, all T(max) values were more than 3 min. For the F0 test, the T(max) value was more than 3 min in 53 kidneys and less than 3 min in 19 kidneys (unilateral in all 19 patients). For the F0 test, for the kidneys with a T(max) value of less than 3 min, there was a tendency to underestimate the split renal function, taking as reference the split renal function observed in the F+20 test. This observation, however, was only statistically significant for the slope method (P=0.03). There was a tendency for lower values with the Rutland-Patlak plot (P=0.07), but, for the integral method, no difference was observed (P=0.5). In conclusion, the simultaneous administration of furosemide with the tracer induces an early acceleration of renal transit. This should be taken into account when calculating the split renal function, for example by favouring the integral method.

The feasibility of deconvolution depends on many factors, but the technique cannot provide accurate results if the maximal transit time (MaxTT) is longer than the duration of the acquisition. This study evaluated whether, on the basis of a 20 min renogram, it is possible to predict in which cases the MaxTT will exceed 20 min. Renograms of various shapes were simulated by convolution of a plasma disappearance curve and various created retention functions with a mean transit time (MTT) ranging from 3 to 23 min. The values of MaxTT were then derived from the created curves and compared to three parameters of transit measured on the renograms: the time to reach the maximum of the curve (T-max), the output efficiency at 20 min (OE20), and the normalized residual activity at 20 min (NORA(20))). The proportion of retention functions (n = 390) with MaxTT > 20 min increased with increasing (e.g. 9% for 6 less than or equal to T-max

Introduction Plasma clearance rate of 51 Cr-EDTA estimated by using one blood sample is commonly used for the calculation of glomerular filtration rate. Aim To estimate the error on single-sample clearance determination induced by errors in sampling time and activity measurement, and to compare it with the error observed on the clearance determination obtained using the slope-intercept method. Methods Forty-five adult patients were chosen from a data base of 51 Cr-EDTA plasma clearance values determined by using two blood samples taken around 2 and 4 h. Patients were selected in such a way as to include clearances from 30 ml.min -1 to 155 ml.min -1 , with steps of 3 ml.min -1 . Based on the slope and the intercept of the slope with the y-axis, the plasma concentration at exactly 2 and 4 h was determined. Normally distributed random errors were then introduced in the sampling time (SD of 0, 1 and 2 min) as well as in the activity measurement (SD of 0,1, 2 and 5%). Then, clearance was calculated using two single-sample methods (i.e. the algorithms of Groth and Tauxe), and the slope-intercept method, which requires two blood samples. For each setting, the simulation was repeated 200 times. The effects on clearance of a random error on the time sampling and/or the activity measurement were then evaluated. Results The error on single-sample clearance induced by a 2 min error in sampling time associated with a 5% error in activity measurement was negligible. For all clearance levels, the SD of the error on the calculated clearance was less than 3.8 ml min-1. Whatever algorithm was chosen, the errors on the single-sample clearance were systematically lower than those observed with the slope-intercept method, for the whole clearance range. Conclusion Errors in sampling time and in activity measurement induced only a very small error on the single-sample EDTA clearance, which is systematically lower compared to that observed on the slope-intercept method using two blood samples.

Output efficiency (OE) has been proposed as an objective tool for the estimation of renal emptying. The aim of this paper was to evaluate some factors that may affect the value of this parameter obtained by a 99Tcm MAG3 renogram. In 22 patients, the effect of different types of renal background correction was calculated. In 10 patients, simultaneous gamma camera renography and multiple blood sampling allowed the error of using a heart curve instead of a plasma curve to be evaluated. Finally, an evaluation was carried out on the effect of neglecting the change of plasma activity between the end of the furosemide acquisition and the post-micturition view obtained after repositioning of the patient on the gamma camera: 142 patients who had had multiple blood sampling were retrospectively selected for that purpose. It has been shown that all these factors may significantly affect the value of OE, particularly in cases with poor renal drainage. Unless standardization of the procedure is introduced for some of these factors, the cut-off levels for good, fair and poor drainage may vary between centres.

Single blood sample methods are widely used for the estimation of the glomerular filtration rate, but the methods recommended for adults are not the same as those for children. The question arises, therefore, as to which method should be used in an adolescent or young adult The aim of this study was to compare the performance of two methods, a specific paediatric converting equation and an adult algorithm, in a group of adolescent and young adult patients. From a large database of 51Cr-ethylenediaminetetraacetic acid (51Cr-EDTA) renal clearance determinations using the two blood sample method, 598 patients, aged 1 week to 90 years, were selected. The results of the 51Cr-EDTA slope intercept clearance of the two blood sample method were used as reference. Using the paediatric algorithm, no bias was observed until the age of 40 years. Then, an increasing positive bias occurred. The standard deviation of the difference was generally less than 4 ml/min until the age of 25 years and increased gradually to reach 7 ml/min at the age of 80 years. Using the Christensen and Groth adult algorithm, the best results were observed in patients older than 50 years. With the exception of children aged less than 5 years, no systematic bias was observed. The standard deviation, however, increased gradually and reached a value of around 8 ml/min in young children. For individuals aged 15-25 years, the mean of the difference between the paediatric algorithm and the slope intercept method was -1.1 ml/min, with a standard deviation of the difference of 3.3 ml/min. For the adult algorithm, the mean of the difference was 0.3 ml/ min, with a standard deviation of the difference of 7.7 ml/ min. It can be concluded that, for individuals aged 15-25 years, both methods performed correctly. In this series, the paediatric method gave better results than the adult algorithm, and its use is therefore recommended. © 2004 Lippincott Williams & Wilkins.

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.

To determine the optimal timing for imaging brain tumours and other brain lesions with 18F-labelled fluoromethylcholine (18F-FCho) PET.Dynamic PET imaging with 18F-FCho (acquisition time of 28 min) was performed in 24 patients with space-occupying lesions in the brain. On the coregistered PET and MRI, lesion-to-normal tissue uptake ratios (LNRs) were calculated. Time-activity curves (TACs) were generated on the basis of the LNRs. Changes in LNR over time were calculated on the basis of the linear part of the TAC (last 22 min of the acquisition).TACs for 18F-FCho in gliomas of different grading showed that, after a rapid uptake phase, the mean increase in LNR was 1.07 ± 0.93 for glioblastomas, -0.52 ± 1.56 for anaplastic astrocytomas, 0.04 ± 0.13 for grade 2 oligoastrocytomas and 0.37 in a case of a pilocytic astrocytoma. The average increase in LNR was 0.46 for a brain metastasis, 0.41 ± 0.69 for radiation-induced mass lesions and 1.07 for a tumefactive demyelinating lesion. In contrast, TACs for 18F-FCho in meningiomas showed that, after a rapid uptake phase, the average change in LNR was -5.25 ± 4.19 for typical meningiomas and -3.04 in a case of a mixed angiomatous and clear cell meningioma.On the basis of the TACs, PET imaging with 18F-FCho starting within minutes after the administration of the tracer is preferred for the detection of brain tumours and other brain lesions. If discrimination between meningioma and other brain tumours is of concern, both 'early' and 'late' PET imaging could be helpful.

Acquisitions of 360 degrees are usually performed for bone single photon emission computed tomography (SPECT). However, the spine is a peripheral and median structure, it therefore seemed interesting to compare the 360 degrees and the posterior 180 degrees SPECT images. In a phantom study and in 25 adult patients, the 360 degrees SPECT images were compared with the posterior 180 degrees images obtained during the same acquisition: the posterior 180 degrees images are at least equivalent to the 360 degrees images. With a reduction in the examination time, SPECT could become easier to perform, especially in patients suffering from back pain.

Until recently, renogram, performed in children with pelvi-ureteric junction stenosis detected antenatally, has not been able to predict the probability of function improvement after surgery or the risk of function deterioration in case of conservative attitude. Recently, Schlotmann et al. have suggested that cortical transit might have this predictive role. The aim of this study, focused on those kidneys with severely impaired cortical transit, was to verify this statement.All renograms performed in children during a 3-year period (n=729) were retrospectively reviewed and 19 pediatric patients were selected based on an antenatally detected unilateral pelvi-ureteric junction syndrome, the existence of at least two renograms during the follow-up and a severe cortical transit impairment, visually defined. Twenty-six pairs of data could be analyzed and allowed comparing preoperative and postoperative differential renal function (DRF), and the DRF changes during the conservative management.Among the 16 patients who underwent pyeloplasty, 10 showed a significant DRF improvement. Among the 10 patients with conservative follow-up, four showed a significant DRF deterioration.Severely impaired cortical transit seems to be a valuable marker of those patients who could benefit from a pyeloplasty, either because of the high probability of postoperative DRF improvement, or because of DRF deterioration in case of an conservative approach. However, a normal cortical transit, as defined in this study, does not exclude the risk of DRF deterioration. Alternatively, the design of this study does not allow excluding the fact that DRF might improve after pyeloplasty despite a normal cortical transit.

PURPOSE The aim of the study was to find out whether in [F]fluoro-2-deoxy-D-glucose positron emission tomography (F-18 FDG-PET) performed in children in our department, the number of counts were sufficiently high to guarantee optimal image quality. METHODS Phantom data with negative and positive lesions were acquired with an increasing count density and the relationship between image quality and counts per voxel was analyzed. On PET images obtained in 28 children aged 4-17 years and using a standard administered activity of 6.5 MBq/kg with a minimum of 74 MBq, the maximum counts per voxel in 10 regions of interest were noted and compared with those obtained on phantoms. RESULTS Phantom data showed clearly the effect of higher count on image quality. Moreover, when high counts were available, reconstruction could be done using 2 mm voxel size, which improved the quality of the images further. In children, the counts per voxel in all the regions of interest, with the exception of the brain, were at a level of suboptimal image quality. CONCLUSION By following the official guidelines, the counts per voxel observed in children with our gadolinium oxyorthosilicate-PET system were lower than the minimal required to produce optimal quality images. More efficient PET systems or higher F-18 FDG dose or increasing the acquisition time or combination of these factors are needed to improve the image quality and lesion detection.

Contrast venography, the accepted gold standard for the diagnosis of venous thrombosis of the leg, is a painful and invasive procedure with late side effects. There is controversy in literature reports about the sensitivity of 99Tcm-macroaggregated albumin (MAA) phlebography: indeed, using 99Tcm-MAA, poor results are obtained when one has to detect calf vein thrombosis. As with other isotopic procedures requiring a pedal injection of the tracer, the use of an injectable solution of 81Krm is a nonspecific method, based upon the abnormality in flow in the deep venous system which results from a deep venous thrombosis. However, when compared with 99Tcm-MAA, 81Krm offers theoretical advantages for phlebographic studies of the lower limbs. In this work 24 patients were studied both with contrast phlebography and with 81Krm. Although 81Krm provided images of high quality, there was a lack of sensitivity below the knee, where false negative results were observed. This could be explained by the fact that the radionuclide venographic procedures usually visualize only one or, in some cases, two of the three deep veins of the calf. Moreover, accurate differentiation between superficial and deep veins in the calf often appears difficult, even using a tourniquet.

Patients often ask for the results after a radioisotope procedure, which can make nuclear medicine physicians feel uncomfortable. In Belgium, nuclear medicine physicians are not supposed to disclose results directly to patients, but to send them to the referring physician. We undertook this work to determine the official rules and practical attitudes in other countries. An introductory letter and a questionnaire were sent to 103 eminent nuclear medicine specialists from 37 countries. Seventy responses (32 countries) were received. Official rules seemed to exist in only seven countries. Most of the respondents indicated that their attitude depended on the clinical situation and the results of the test. Many respondents emphasized that, while in some situations the results should be communicated directly to patients in order to initiate treatment rapidly, in other situations, such as cancer, the referring physician was better suited to disclose the results. The advantages and drawbacks of different attitudes are discussed. Practically and universally applicable rules are difficult to establish, but choosing one solution remains preferable to no standardized attitude at all. An official body, including the medical community, representatives of the population and legal experts, should define an official rule which should be widely communicated, stressing its advantages and drawbacks. In practice, all nuclear medicine physicians would have to do would be to stick to the rule.

Rheumatoid arthritis (RA) is an inflammatory disease affecting mainly the joints. In addition, signs of systemic disease are likely to be present although they are not always clinically evident. Oesophageal motility dysfunction, present in 75% of progressive systemic sclerosis patients, was also reported in various other connective tissue diseases. The present study involved 32 rheumatic patients devoid of any gastrointestinal complaints or diseases: 16 RA, nine Raynaud's syndrome and seven mild osteoarthritis as controls. Oesophageal transit was assessed by using 81Krm radionuclide scan, a sensitive and non-invasive technique. Diffusing lung capacity for carbon monoxide (DLCO) was performed as evidence of subclinical systemic involvement. Abnormal oesophageal transit was observed in 5/16 RA (31%). Two of them were subsequently discarded due to the presence of asymptomatic goiter and asymptomatic gastrointestinal reflux leaving 3/14 RA for analysis. They all had extra-articular features (EAF) (pericarditis, nodules) and two of them had diminished DLCO. Two with Raynaud's syndrome had abnormal oesophageal transit but none of the controls had abnormal oesophageal transit. Upper gastrointestinal dysfunction after exclusion of symptomatic patients appears thus to be not very frequent in RA, even when a sensitive technique is used. Radionuclide transit scanning of the oesophagus is not a more useful method than others in detecting early EAF in RA.

By exploiting the ultrashort half-life 191Irm as tracer for left ventricular first-pass angiocardiography and 201Tl 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 201Tl six weeks after PTCA would mean that the circulation has been successfully reestablished 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 191Irm in combination with 201Tl offers the opportunity of performing myocardial perfusion and wall motion studies simultaneously both at rest and during exercise.

First pass radionuclide angiocardiography (FPRNA) has gained increasing interest because of the development of new 99Tcm-labelled perfusion agents and of new 191Os/191Irm generator systems. The aim of the study was to evaluate the performance capacities of a small field of view single crystal digital gamma camera for 99Tcm and 191Irm at high count rates. The camera dead time for 99Tcm (window 30%) was well corrected up to 300 kcps in fast acquisition mode using the relative decrease of a small shielded reference source. Using the decaying activity method for 191Irm the non-linearity response of the gamma camera was corrected by an 191Os reference soruce up to 210 kcps at 70 keV, 75 kcps at 129 keV and 320 kcps including both peaks. Saturation count rates were respectively 270 kcps, 150 kcps and 420 kcps and high count rate resolution (FWHM) 9.0, 7.3 and 10.3 mm. Since the accuracy of first pass measurements is more sensitive to count rate than to spatial resolution the 50-150 keV window was chosen for clinical studies. In data obtained from 32 ECG gated FPRNA patient studies, the whole field of view count rate during the left ventricular phase ranged from 100 to 250 kcps with 80 to 120 mCi (2960-4400 MBq) of 191Irm and 100 to 180 kcps with 20 to 25 mCi (750-925 MBq) of 99Tcm red blood cells permitting for both tracers accurate non-linearity correction.

This study was performed to investigate the interobserver reproducibility of the interpretation of Tc-labelled white blood cell scans combined or not with other nuclear medicine procedures.Twenty nuclear medicine physicians working in Belgium received clinical data and scintigraphic images from 10 patients suspected of suffering from various infectious diseases. They had to choose, for each patient, one answer among 'high probability', 'intermediate probability' and 'low probability' of infection. In a first step the level of agreement, defined as the highest percentage obtained among the three proposed answers, was calculated for each case; complete agreement was arbitrarily defined when 80% or more of the observers gave the same answer. In a second step, a numerical score was given for each answer and for each observer. The scores were defined as 0 for the 'low probability' answer, 1 for the 'intermediate probability' and 2 for the 'high probability' answer. The scores of each observer were summed up allowing obtaining of a cumulated score for each observer; observers were thereafter classified as a function of their own cumulated score.An agreement of 80% or more was observed only in three patients. The cumulated scores of the observers were between 4 and 16, demonstrating that some observers were more sensitive than others.Interobserver reproducibility in the interpretation of the white blood cell scan was poor; several factors could explain these results, the most frequent being both the poor specificity of the labelled white blood cell scan and different concepts in interpreting combined nuclear medicine procedures in several situations. As observers received the anonymized overall results, this study may have a favourable impact on continuing education in medical imaging.

BACKGROUND: Mean transit time (MTT) within a kidney is given by the integral of the renal activity on a well-corrected renogram between time zero and time t divided by the integral of the plasma activity between zero and t, providing that t is close to infinity. However, as the data acquisition of a renogram is finite, the MTT calculated using this approach might result in the underestimation of the true MTT. To evaluate the degree of this underestimation we conducted a simulation study. METHODS: One thousand renograms were created by convoluting various plasma curves obtained from patients with different renal clearance levels with simulated retentions curves having different shapes and mean transit times. RESULTS: For a 20 min renogram, the calculated MTT started to underestimate the MTT when the MTT was higher than 6 min. The longer the MTT, the greater was the underestimation. Up to a MTT value of 6 min, the error on the MTT estimation is negligible. CONCLUSION: As normal cortical transit is less than 2 min, this approach is used for patients to calculate pixel-to-pixel cortical mean transit time and to create a MTT parametric image without deconvolution. © 2008 Lippincott Williams & Wilkins, Inc.

Background Automatic and semi-automatic algorithms to calculate ejection fraction (EF) from planar radionuclide ventriculography (PRV) have been used for many years in nuclear medicine. Validation of these algorithms is scarce and often performed on outdated versions of the software. Nevertheless, clinical trials where PRV is being used as the 'gold standard' for EF are numerous. Because of the importance attributed to the EF calculated by these programs, the accuracy of the resulting EF was assessed with a dynamic left ventricular physical phantom. Methods A dynamic left ventricular phantom was used to simulate 21 combinations of various ejection fractions (7-66%) and end diastolic volumes (27-290 ml). For each combination, a planar radionuclide ventriculograph was acquired, converted to an interfile format and transferred into processing stations with 10 different contemporaneously available commercial algorithms. The gold standard was the 'real' EF of the phantom, derived from the exact volume of the ventricle in end diastolic and end systolic position. Correlation and Bland-Altman analysis was performed between the real EF and the calculated EF. Results The correlation for all data was excellent (r=0.98), the mean difference was very acceptable (0.98%). Nevertheless, Bland-Altman analysis showed a significant trend in the difference between real and calculated EF, with a growing underestimation for higher ranges of EF, due to an overestimation of background in larger volumes compared to smaller ones. Conclusion The determination of EF from PRV, calculated with commercially available algorithms, correlates closely to the real EF of a dynamic left ventricular phantom. This phantom can be used in the development and validation of algorithms for PRV studies, in software audits and in quality assurance procedures.

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.

Objective: To quantify the influence of overall renal function on normalized residual activity (NORA) and to evaluate the modifying factors. Methods: A computer simulation model generated renograms by convolution of plasma disappearance curves with artificially created retention functions. From a database, 1099mTc-MAG3 plasma curves were selected, corresponding to renal clearances ranging from 33 to 405 ml·min -1. The retention functions had three properties: (1) until the minimal transit time (MinTT), no output and a linear increase in transit time after MinTT; (2) a ratio of MinTT to mean transit time (MTT) equal to 0.3 or 0.8; and (3) a MTT between 3 and 60 min, increasing in steps of 1 min. The model generated 1160 renograms and for each of them the NORA was calculated at 20, 40 and 60 min. For each value of MTT, the coefficient of variation (CV) of the NORA was calculated at 20, 40 and 60 min. Results: For the same retention function, different clearances resulted in different values of NORA. The degree of variability of NORA depended on several factors, including the time of measurement, the MTT and the MinTT to MTT ratio. For clearances between 100 and 400 ml·min-1, the CV of the NORA ranged from 15% to 30%, whilst for clearances below 100 ml·min-1, the CV of the NORA ranged from 22% to 67%. Little influence of the MinTT to MTT ratio was observed. Conclusion: NORA is influenced by overall renal function. The influence is limited for 99mTc mercaptoacetyltriglycine (99mTc-MAG 3) renal clearances over 100 ml·min-1, whilst for clearances less than 100 ml·min-1, the NORA is influenced much more. © 2004 Lippincott Williams & Wilkins.

The aim of this work was to compare the quality of renal drainage obtained with two well-described procedures of diuretic renography (F+20 and F0 tests). We selected 36 clinically stable children, aged 10 days to 17 years, with unilateral (25) or bilateral (11) hydronephrosis, in whom both F+20 and F0 tests were successively performed. In all cases, a late image (PM) was acquired after micturition and after changing the position of the patient. The following parameters were calculated: the time to the maximum of the basic renogram (Tmax); and the normalized residual activity (NORA) and output efficiency (OE) at the end of the 20 min renogram, at the end of the furosemide test (35 min) and on the PM image. In F+20, the renal drainage was better on the PM image than at the end of the diuretic renogram, whereas, in F0, the renal drainage was better on the PM image than at the end of the 20 min diuretic renogram. When comparing F0 and F+20, both OE and NORA parameters revealed slightly better drainage at the end of the 20 min F0 renogram than at the end of the 35 min F+20 diuretic renogram. The drainage obtained on the late post-voiding image was comparable for both F0 and F+20 tests. In conclusion, the quality of drainage obtained during the F+20 and F0 procedures can easily be compared using both OE and NORA. A very similar quality of drainage was reached for both procedures when considering only the PM image. This PM view remains mandatory irrespective of the timing of the furosemide injection and despite the use of tracers with a high extraction rate.

The aim of this study was to assess the influence of the physiological changes of gastric emptying on the simplified 14 C-urea breath test. Thirty patients performed the test in fasting conditions. Patients were orally administered 0.074 mega Bq of 14 C-urea, mixed with 0.0185 mega Bq of 99m Tc-S colloids in 25 ml water. A breath sample was taken before and 10 min after intake of the tracers and followed by a 2 min planar anterior scintigraphic image of the abdomen to measure gastric activity. Gastric emptying was estimated by dividing the residual gastric activity at 10 min by the total activity in the abdomen. The procedure was performed twice for each patient after a 24 h interval. The repeatability of both the gastric emptying test and the urea breath test was assessed by the method described by Bland and Altman. The coefficient of repeatability of the urea breath test was 1.18 for a confidence interval of 95%. The coefficient of repeatability of gastric emptying was 27.4. There was no significant correlation (r= 0.08) between the plot of the individual modifications of urea breath test and residual gastric activity in two successive tests. It is concluded that the physiological changes of gastric emptying do not influence the results obtained by the simplified, single-sample 14 C-urea breath test.

Dual photon absorptiometers (DPA) are currently being replaced by dual energy X-ray absorptiometers (DXA) for measurements of bone mineral density (BMD). In order to evaluate how to use the previously obtained BMD results by DPA (BMDo) in the follow-up of patients, the following study was performed. Ninety-five women who had had BMDo during the last 12 months were selected. L2-L4 BMD was measured twice on the same day using both DPA (BMDp) and by DXA (BMDx). BMDp was highly correlated to BMDx (R = 0.95; P < 0.001) but a wide variation of the ratio BMDp:BMDx was observed which ranged between 0.65 and 1.09 (mean 0.90, S.D. 0.05). There was no significant relationship between the ratio BDMp:BMDx and age or height but there was a significant relationship between this ratio and the weight of the patient (R = 0.31; P < 0.001). The results also indicated that the correlation between DXA and DPA was lower than that observed between the two DPA measurements (R = 0.98; P < 0.001) which, moreover, were not performed on the same day. These observations contrast with the relatively high precision of both instruments and have to be attributed to relative inaccuracy of one or probably both techniques.

Mono-compartmental analysis based on 2- and 4-h blood samples (BS) of 51Cr-EDTA (EDTA, ethylenediaminetetraacetic acid) is commonly used for the calculation of the glomerular filtration rate (GFR). The purposes of this study were to estimate the magnitude of error in clearance induced by errors in the time of sampling and activity measurement; to estimate the impact of changing the interval between the BS; and to assess the influence of a higher number of BS in reducing the error. A model of mono-exponential curves based on a finite number of BS was created. Normally distributed random errors were introduced in the time of sampling and activity measurement. In a first step, three different time intervals were used; in a second step, seven different numbers of BS were used, all taken between 120 and 240 min. For each setting, the random errors were successively introduced 200 times and the coefficients of variation (CV) of the calculated clearances were determined. Variable errors in clearance were induced by errors in the time of sampling and activity measurement. In general, the observed errors were higher for high and low clearance, with lower errors for moderately reduced clearances. The errors in indicating the time of sampling played an important role for high clearance, whereas the errors in activity measurements led to important errors for low clearance. Prolonging the interval from 1 to 2 h resulted generally in an important decrease in error, except in the range 60-100 ml x min(-1). Prolonging the interval from 2 to 3 h resulted in only a small additional decrease in error, except for very low clearance. Errors in indicating the time of sampling and in activity measurements induce errors in clearance determination. These errors cannot be significantly reduced by simply increasing the number of BS or by prolonging the interval between the samples. It is probably better, in most cases, to keep using the 2-4-h method and to take extreme care when indicating the time of sampling and when measuring the activity, instead of increasing the number of samples or lengthening the procedure.

99Tcm-DMSA planar images of 49 randomly selected patients (10 adults, 39 children) were sent to 15 physicians at various centres in Belgium. They were asked to calculate, using their own routine program, the relative uptake (expressed as a percentage) of each kidney. The data were sent on disks formatted so that they could be read by all participants, using their own computer systems. For each scan, the inter-observer variability was expressed using the maximum difference and the standard deviation of left renal uptake. Left renal uptake measured by the 15 observers in the 49 patients was 29.0-72.0% (mean +/- s = 49.8 +/- 6.4%). The maximum differences in left renal uptake ranged between 1.7% and 12.0% (4.5 +/- 2.6%); however, the maximum difference did not exceed 8% in about 90% of the patients. The standard deviations of the individual left renal uptake were between 0.6 and 3.9 (1.3 +/- 0.8). The standard deviations were significantly higher in adults (mean standard deviation = 2.05) than in children (mean standard deviation = 1.12) (P < 0.001); this was probably related to the high background observed in three adults with severe renal impairment. Indeed there was a significant correlation (P < 0.001) between the standard deviation and both the signal-to-noise ratio and the degree of asymmetry between the right and left kidneys. The differences between right and left kidney uptake were systematically lower for some observers, suggesting an influence of the calculation programs.

It has been suggested that the slope of the second exponential of the plasma disappearance curve may be used to monitor changes in renal function instead of plasma clearance calculated using the slope-intercept method. The purpose of this study was to evaluate the magnitude of error in the slope induced by errors in sampling time and in activity measurement, and to compare it with the error observed in clearance. A model of mono-exponential curves based on two blood samples, taken at 120 and 240 min, was created. Normally distributed random errors were introduced into the sampling times and activity measurements. For each setting, the random errors were successively introduced 200 times and the coefficients of variation of the calculated slopes and clearances were determined. Variable errors in slope and clearance were induced by errors in sampling time and activity measurement. In general, the observed errors in the slope were high in the case of low slope values, decreasing progressively for increasing slope values. The errors in clearance followed a different pattern: highest errors were observed in the case of very low clearance, decreasing progressively for higher clearance values and attaining the minimal value at a lambda around 0.006 min-1, which corresponds to clearance of about 90 ml.min-1. The magnitude of the errors then started to increase again for higher clearance. For a large range of clearance values, the errors in the slope were higher than the errors in clearance. The only exceptions were cases with very high clearance rates. In conclusion, clearance calculation using the slope-intercept method should be preferred to that using the slope alone for monitoring changes in renal function.

The aim of this study was to evaluate a simple parameter describing renal output, namely NORA (normalized residual activity). We first compared, in a simulated model, different parameters of transit to an ideal standard; we then compared, in a clinical study, NORA and output efficiency. 123I-hippurate, 99Tcm-DTPA and 99Tcm-MAG3 plasma curves, each with two levels of renal clearance, were convoluted by means of different types of simulated retention functions, with different mean transit times. On the reconstructed renograms, several parameters reflecting renal transit were determined and compared with mean transit time. In a second step, in 33 patients, we compared output efficiency and NORA (i.e. the residual renal activity), normalized by the renal activity at 2 min. These two parameters were calculated at the end of the renogram, at the end of the frusemide test and after the micturition phase. In the simulated model, both output efficiency and NORA were only slightly influenced by the level of overall renal function. In the clinical study, a good correlation was found between output efficiency and NORA, whatever part of the study considered (renogram, frusemide test, post-voiding image). NORA is a simple and reliable parameter that allows quantification of renal output; it is almost independent of the level of renal function and can be used whatever the timing of the frusemide injection.

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 99 Tc m -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 -1 1.73 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 (T max - 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.

From a database of 133 patients (98 children and 35 adults) who underwent multiple blood sampling for 99Tcm-mercaptoacetyltriglycine (MAG3) clearance, we determined simplified algorithms allowing the estimation of clearance. A one-compartment model with two blood samples was applied. The best choices for the adult population were the 12 and 90 min blood samples, giving a standard error of the estimate (S.E.E.) of less than 10 ml min-1 1.73 m-2; for the children, the 10 and 80 min blood samples gave a S.E.E. of 20 ml min-1 1.73 m-2; for both the adults and the children, the 10 and 70 min blood samples gave the best results with, however, a S.E.E. of 19 ml min-1 1.73 m-2. The use of such a combined algorithm will therefore result in a degradation of the results in adults, suggesting that a separate algorithm for each group is preferable. We compared the accuracy of the two blood sample method to the one blood sample method based on previously published algorithms for children and adults, respectively. The S.E.E. was significantly lower, in adults as well as in children, using the empirical two blood sample method. This two blood sample method seems potentially useful for routine practice in adult patients. The advantages of using such a method in children is balanced by the practical problems inherent in the need to take a second blood sample during the first 10 min, at a time when the plasma activity is rapidly decreasing.

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.