The potential value of a pictorial atlas for aid in the visual diagnosis of 123I FP-CIT SPECT scans.

The aim of our study was to evaluate the value of a pictorial atlas of 123I FP-CIT SPECT images for aid in the visual diagnosis. PATIENTS, MATERIALS, METHODS: Sixty patients, of whom 20 were clinically diagnosed as 'non-parkinsonian' and 40 as having Parkinson's disease or any related disorder, were included in the study. An atlas consisting of 12 123I FP-CIT SPECT images was constructed first. Validity of the atlas was investigated by performing a receiver operating characteristic (ROC) analysis with the clinical diagnosis as the gold standard. The remaining 48 SPECT images were visually assessed twice by 5 observers, first with and secondly without consulting the atlas, or vice versa. The added value of the atlas was investigated by comparing the diagnostic accuracy and the interobserver variability for both methods. RESULTS: ROC analysis performed on the atlas yielded an area under the curve of 1 for a threshold discriminating between clinically non-parkinsonian and parkinsonian patients that was situated between image 4 and 5 of the atlas. For the diagnostic accuracy, we found that the area under the ROC curve was systematically higher if observers had access to the atlas compared to when they had not (Wilcoxon's test, p<0.05). Also, the interobserver variability was significantly lower when observers used the atlas when compared to when they did not (p = 0.05). CONCLUSION: Diagnostic accuracy was significantly higher and interobserver variability significantly lower if observers had access to the atlas compared to when they had not. Hence, having a pictorial atlas available may facilitate the visual assessment of 123I FP-CIT SPECT scans.

Recombinant human thyrotropin administration enhances thyroid uptake of radioactive iodine in hyperthyroid cats.

BACKGROUND: Hyperthyroidism is the most diagnosed endocrine disorder in cats and radioiodine (131I) is the treatment of choice. The dose emission rate and radioactivity in urine, saliva, and on hair and paws are determined by the dose of administered 131I. A dose reduction of therapeutic 131I could possibly be achieved after recombinant human thyrotropin (rhTSH) administration as in humans with nodular goiter. HYPOTHESIS: rhTSH will increase radioiodine uptake in hyperthyroid cats. ANIMALS: Five hyperthyroid cats. METHODS: Twenty-five micrograms rhTSH (day 1) or 2 mL 0.9% sodium chloride (NaCl) (day 9) was injected IV. One hour later, 11.4 +/- 4.1 (mean +/- SD) MBq 123I was injected IV. Radioactive iodine uptake (RAIU) was measured 6, 12, and 24 hours after rhTSH (RAIU-rhTSH) or NaCl (RAIU-blanco) injection. Blood samples for measurement of TT4 were taken before injection of rhTSH or NaCl (TT4(0)) and at the time of imaging. RESULTS: Percentages of RAIU-rhTSH (and RAIU-blanco) at 6, 12, and 24 hours after administration of rhTSH were 34 +/- 18 (31 +/- 21), 46 +/- 20 (38 +/- 18), and 47 +/- 15 (36 +/- 14). There was a statistically significant effect of rhTSH administration on RAIU (P = .043) but not on serum TT4 concentration. Baseline serum TT4(0) concentration influenced RAIU-rhTSH significantly at 6 hours (P = .037). CONCLUSION AND CLINICAL IMPORTANCE: The increased RAIU observed after rhTSH administration in hyperthyroid cats could lead to a lower therapeutic dose of 131I after rhTSH administration in hyperthyroid cats and decreased risk of environmental and owner contamination during and after hospitalization.

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.

Serotonin transporter and dopamine transporter imaging in the canine brain.

The serotonergic and dopaminergic systems are involved in a wide range of emotional and behavioral aspects of animals and humans and are involved in many neuropsychiatric disorders. Selective serotonin (5-HT) reuptake inhibitors (SSRIs) are designed to block the 5-HT transporter (SERT), thereby increasing the available 5-HT in the brain. Functional imaging with specific SERT and dopamine transporter (DAT) ligands contributes to the study of the SSRI-transporter interaction. First, we evaluated the feasibility of a canine model in the study of the SERT and DAT with the radioligands [123I]-beta-CIT and [123I]-FP-CIT as well as single-photon emission computed tomography imaging. Second, we studied the effect of SSRIs (sertraline, citalopram and escitalopram) on the SERT and DAT in two dogs. The position of the canine model in the study of the SERT and DAT is discussed and compared with other animal models.

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.

Influence of methodology on the presence and extent of mismatching between 99mTc-MIBI and 123I-BMIPP in myocardial viability studies.

UNLABELLED: Discordant uptake (mismatching) of 123I-labeled beta-methyl-piodophenyl-pentadecanoic acid (BMIPP) less than 99mTc-labeled methoxyisobutyl isonitrile (MIBI) is a good predictor of myocardial viability. However, methodological factors can influence assessment of the presence of mismatching because of differences in background activity between the tracers. In this study, we investigated the influence of methodological parameters on the mismatching between BMIPP and MIBI in patients with chronic ischemic heart disease. METHODS: Polar maps were created to quantify the extent of mismatched tissue measured in 10 patients with myocardial infarction according to three methods for data processing: no correction, subtraction of background activity measured in the left ventricle cavity and dual-window scatter correction. Mismatching was expressed as a percentage of the surface of the left ventricle globally as well as for each arterial territory using a BMIPP uptake of at least 10% less than MIBI as the threshold. The results of dobutamine stress echocardiography and the evolution of the regional contractility at 6-mo follow-up were used as references. RESULTS: Mean background activity in the ventricle cavity was 9.3% of the maximum activity for MIBI and 21.4% for BMIPP before, and 2.8% and 8.3% after scatter correction. Fourteen arterial vascular territories demonstrated baseline wall-motion abnormalities; 9 territories showed contractile reserve with dobutamine stress echocardiography. Significant mismatching was found in 5 of 14 regions without correction, 9 of 14 after scatter correction and 13 of 14 after background subtraction. Compared with the evolution of resting regional contractility at follow-up, optimal results were found when using the scatter-corrected data. Without correction, mismatching between BMIPP and MIBI was partially disguised because of the higher noise level in the iodine images. On the contrary, subtraction of background measured by means of a single region of interest overestimated the magnitude of mismatching due to the heterogeneous background distribution in the ventricular cavity. CONCLUSION: In quantifying the presence and extent of mismatching between MIBI and BMIPP in chronic ischemic heart disease, significant differences in the detection of viability are noted according to the acquisition and processing methods used. Scatter correction of the acquisition data is the most accurate and reliable method for identifying viable myocardium.

BMIPP imaging to improve the value of sestamibi scintigraphy for predicting functional outcome in severe chronic ischemic left ventricular dysfunction.

UNLABELLED: Mismatching between beta-methyl-p-iodophenyl-pentadecanoic acid (BMIPP) and perfusion accurately predicts functional outcome after acute myocardial infarction. The current investigation was aimed at evaluating the value of this method to predict the evolution of global function according to the applied treatment in patients with chronic ischemic heart disease. METHODS: Twenty patients with infarction and chronic left ventricular dysfunction were studied (median infarction age 12 wk, range 2 wk-15 y). Radionuclide angiography, two-dimensional echocardiography and BMIPP and gated sestamibi scintigraphy were performed with the patient at rest before and >6 mo after treatment (revascularization in 13 patients and conservative therapy in 7 patients). In 7 patients, radionuclide angiography was repeated after 1 y. RESULTS: On a patient basis, mismatching with BMIPP less than sestamibi was noted in 15 patients at baseline. Of these 15 patients, 11 had significant functional improvement at follow-up versus only 1 of the 5 patients with a matched decreased uptake. Hence, the combined sestamibi/BMIPP was 73% positive and 80% negative in predicting functional outcome, with a global accuracy of 75%. On a segmental basis, using an optimal threshold of uptake defined by receiver operating characteristic curve analysis, sestamibi was only 63% accurate in predicting regional outcome. Adding BMIPP improved the accuracy to 80% (P = 0.001). At follow-up, significant mismatching was still noted in 7 patients in the revascularized group and 1 in the medically treated group. The mismatch was associated with a further increase in ejection fraction at 1-y follow-up in only the revascularized group. CONCLUSION: In patients with chronic left ventricular dysfunction after infarction, a mismatching with BMIPP less than sestamibi reliably identifies jeopardized but viable myocardium and predicts functional recovery with an accuracy similar to that reported in the acute and subacute phases of the infarction.

Abnormal BMIPP uptake in chronically dysfunctional myocardial segments: correlation with contractile response to low-dose dobutamine.

UNLABELLED: Discordance between 123I-15-(p-iodophenyl)-3-(R,S)-methyl pentadecanoic acid (BMIPP) and sestamibi uptake has been described as a good predictor of functional recovery in patients with a recent myocardial infarction. The current investigation aimed at evaluating BMIPP as a viability tracer in patients with chronic ischemic left ventricular dysfunction. METHODS: Thirty-one studies were obtained in 25 patients with severe left ventricular dysfunction postinfarction (median infarction age 3.6 mo; range 2 wk-15 yr). All patients underwent dobutamine stress echocardiography and a resting 99mTc-sestamibi/123I-BMIPP SPECT study in a 3-day interval. The relative uptake of the two tracers was compared to the evolution of wall motion during dobutamine infusion in 8 matched myocardial segments. RESULTS: Among the 130 segments with abnormal wall motion at rest, 70 improved under dobutamine. Using sestamibi, a normal uptake was 88% predictive of a positive response to dobutamine, and a decreased uptake of 63% predicted negative stress echocardiography response. In the segments with abnormal sestamibi uptake, adding BMIPP significantly increased the accuracy of scintigraphy to detect residual viability; 28 of 48 segments (58%) with a mismatched pattern demonstrating residual inotropic reserve under dobutamine infusion versus only 5 of 40 segments (13%) with a matched defect. Global agreement between the two approaches was 77%, and positive and negative predictive values for scintigraphy were 72% and 88%, respectively. CONCLUSION: In patients with chronic ischemic left ventricular dysfunction, the combined assessment of metabolism and perfusion with 123I-BMIPP and 99mTc-sestamibi correlates well with the response of wall motion to dobutamine during stress echocardiography and is more sensitive than sestamibi alone for differentiating viable from scar segments.

Clinical usefulness of ultrashort-lived iridium-191m from a carbon-based generator system for the evaluation of the left ventricular function.

Ultrashort-lived 191mIr (4.96 sec; 63-74 and 129 keV photons) is potentially advantageous for first-pass radionuclide angiocardiography, offering the opportunity to perform repeat studies with very low absorbed radiation dose to the patient. Left ventricular (LV) first-pass studies were performed in 72 patients with 191mIr from a new bedside 1.3 Ci (48.1 GBq) 191Os/191mIr generator system using an activated carbon support that offers high 191mIr yields (15-18%) and consistent low 191Os breakthrough (2-4 x 10(-4)%/bolus). Using a single crystal digital gamma camera, uncorrected end-diastolic counts in the left ventricular representative cycle ranged from 10 up to 30 k counts. The reproducibility of repeated LV ejection fraction (LVEF) determination at 2-min intervals in 50 patients was r = 0.97, mean diff. = 2.08 +/- 1.55 EF units. Comparison between 191mIr (80-120 mCi; 2,960-4,400 MBq) and 99mTc (20-25 mCi; 750-925 MBq) LV count rates indicates a 3 wk useful shelf life of this new generator system for cardiac studies. Iridium-191m determined LVEF correlated closely with 99mTc determined LVEF in 32 patients (r = 0.96, mean diff. = 1.87 +/- 1.23 EF units). Parametric images for LV wall motion analysis were comparable with both isotopes. We conclude that rapid, repeat, and reproducible high count rate first-pass left ventricular studies can be obtained with 191mIr from this new 191Os/191mIr generator system using a single crystal digital gamma camera.

Single photon emission computed tomography using perfusion tracers in seizure disorders.

Single photon emission computed tomography (SPECT) using perfusion tracers makes it possible to estimate regional cerebral blood flow (rCBF) and, indirectly, local brain metabolism. It may be possible to detect and follow physiopathological alterations, such as may be seen in seizure disorders. The authors review the principles of and some data on perfusion SPECT in seizure disorders, stress advantages as well as major drawbacks and add their initial experience with Tc-99m hexamethylpropyleneamine oxime (HMPAO) SPECT in febrile convulsions.

Validation of the cerebellum as a reference region for SPECT quantification in patients suffering from dementia of the Alzheimer type.

In longitudinal brain studies of dementia of the Alzheimer type (DAT), the cerebellum is often used as a reference region for single photon emission computed tomography (SPECT) quantification, which assumes no significant regional influence of physiological fluctuations or pathology. With the use of absolute quantification in DAT patients, reproducibility of cerebellar uptake of technetium-99m-d,l-hexamethylpropyleneamine oxime (HMPAO) was tested and compared with the mean absolute cerebellar tracer uptake value in DAT patients and healthy control subjects. In 13 DAT patients SPECT studies were repeated within 2 weeks to assess reproducibility of cerebellar regional brain uptake (rBU). With calibrated point sources as scaling factors, cerebellar activity was expressed as rBU of HMPAO per cm3 brain tissue in percent of the injected lipophilic dose of 740 MBq (20 mCi). Also, mean cerebellar rBU in patients suffering from DAT was calculated and compared with a previously established database obtained in healthy volunteers. Repeated SPECT studies within a 2-week interval in clinically stable patients resulted in a mean rBU increase of 6.8 +/- 10.3% in the second SPECT study as compared with the first. A similar shift was previously reported in healthy volunteers. Mean cortical cerebellar rBU values in DAT patients and in the healthy reference population concurred, after cumulative corrections for body surface and for a mean brain volume of 1350 ml (obtained in healthy control subjects), showing respective mean values of 53.9 +/- 7.4 and of 52.0 +/- 7.3 x 10(-6) of the injected lipophilic dose 740 MBq (20 mCi) of HMPAO per cm3 of brain tissue. A unidirectional shift in mean absolute cerebellar uptake values occurs between repeat SPECT examinations in DAT patients similar to previous findings in a group of healthy volunteers. The origin of this phenomenon remains elusive but deserves further study with regard to SPECT (semi)quantification in DAT patients. Most interestingly, the presented findings suggest that with the use of HMPAO SPECT in DAT patients the cerebellum remains scintigraphically uninvolved.

Quantification of 99Tcm-sestamibi and 123I-BMIPP uptake for predicting functional outcome in chronically ischaemic dysfunctional myocardium.

Little is known about the usefulness of free fatty acid scintigraphy for assessing viability in chronic ischaemic heart disease. To investigate this, we quantified the uptake of 99Tcm-sestamibi and 123I-BMIPP at rest twice within 6 months in 20 patients with chronic ischaemic left ventricular dysfunction and infarction. Four patterns of the relative distribution of both tracers were observed and classified as normal, mismatched, matched and scar. The proportion of the left ventricular surface corresponding to each pattern was expressed as the percentage of the total surface using a polar map. Between the two studies, the patients either underwent revascularization or were treated conservatively. The quantitative results were compared with those of dobutamine stress echocardiography (DSE) in arterial territories with resting contractile dysfunction and correlated with the evolution of regional and global function at follow-up. At baseline, 25 arterial territories were analysed. Using sestamibi, on average one-third of their surface was considered to be normally perfused. No clear association was found between the percent normally perfused surface and the DSE findings. Adding BMIPP and using a value of > 7% of the arterial surface with BMIPP lower than sestamibi (mismatch) as the cut-off for the significance of viability, 14 of 18 mismatched regions were considered viable by DSE, and six of seven with < 7% mismatched surface or matching were not. Fifteen patients were viable, of whom 13 were revascularized (16 territories). At follow-up, global function improved in 11 of the 15 viable patients, all in the revascularized group. Regional improvement was noted in 11 of 16 revascularized territories, and was associated with a significant increase in sestamibi and BMIPP uptake and in the percent normally perfused myocardial surface. In the five patients without significant viability, no functional deterioration or changes in the quantitative parameters were observed during treatment. The results suggest that quantitative analysis of the uptake of sestamibi and BMIPP is a reliable method to objectively assess the presence of myocardial viability in chronic ischaemic heart disease and to predict functional improvement after revascularization.

SPET-generated colour-coded polar maps to quantify 99Tcm-MIBI and 123I-BMIPP uptake in chronically dysfunctional myocardium: comparison with coronary anatomy and wall motion.

The combined use of 123I-BMIPP and 99Tcm-MIBI SPET imaging has been proposed as an alternative to PET for the non-invasive detection of jeopardized myocardium after a myocardial infarction, a mismatch accurately indicating jeopardized but still viable tissue. In this paper, a new quantitative approach is described, expressing the presence and degree of mismatch as the percentage of the left ventricular surface globally as well as for each major epicardial artery by means of clearly identified colour-coded polar maps. With this method, the relative proportion of normal and scar tissue, each characterized by a specific colour, is measured using thresholds of 99Tcm-MIBI uptake of 60% and 30% of the expected mean normal value respectively, whereas the presence and extent of mismatch between 99Tcm-BMIPP and 99Tcm-MIBI are calculated only between these two thresholds, typically corresponding to a reduction in flow associated with a possible but uncertain post-revascularization recovery. Applied to 15 patients with severely impaired left ventricular function after a myocardial infarction, small intra- and inter-observer differences were noted in the assessment of the relative proportion of normal, mismatched and scar tissue. More specifically, analysing the variability in the calculated percent mismatch, good reproducibility was observed, with intra- and inter-observer correlation coefficients of 0.96 and 0.94 respectively, a mean (+/- S.D.) intra-observer difference of 0.25 +/- 2.0% for the left ventricle globally, 1.65 +/- 2.9% for the left anterior descending artery (LAD), -1.56 +/- 3.6% for the left circumflex artery (LCX) and -1.24 +/- 2.8% for the right coronary artery (RCA) territories, and mean inter-observer variability of 0.91 +/- 2.4% for the left ventricle globally, -1.51 +/- 3.0% for the LAD, -0.53 +/- 2.9% for the LCX and -0.34 +/- 3.9% for the RCA territories. Using the second standard deviation of the inter-observer difference as a criterion of significance, a significant mismatch between 99Tcm-BMIPP and 99Tcm-MIBI was noted in 13 arterial territories, corresponding to significant stenoses on coronary angiogram and/or wall motion abnormalities in all cases. These results suggest that this new quantitative method, showing good reproducibility, may constitute a reliable and interesting tool for the non-invasive evaluation of myocardial viability with SPET.

Influence of statistical noise on the determination of the single kidney 99Tcm-DTPA clearance.

Single kidney clearance can be obtained using the 99Tcm-DTPA complex and the scintillation camera. In order to evaluate the influence of statistical noise on the determination of the clearance, several non-noisy curves were constructed, simulating renal, background and precordial curves. Poisson noise was added to these curves and the clearance results were compared to those obtained on the original curves. It was shown that, in so far as a moderate curve smoothing was used, the statistical noise did not interfere considerably with the results of the renal clearance.

Effect of mild mental stress on solid phase gastric emptying in healthy subjects.

Radionuclide gastric emptying studies are performed in clinical routine but the possible influence of the mental state of the patient is never taken into account. We wanted to evaluate the effect of a mild psychological stress on solid phase gastric emptying in healthy young male volunteers. The standard meal consisted of a pancake (500 kJ) without additional liquid. Simultaneous dynamic acquisitions of gastric activity in anterior and posterior projection were taken during 90 min starting from the onset of the meal. Gastric emptying was evaluated three times in basal conditions and once under mental stress. Stress was induced by means of a dichotomous listening test, lasting for 30 min, starting at the end of the meal. The results of rest and stress studies were compared. Mild mental stress has a significant influence on gastric emptying. The lag phase increased from 11 +/- 3 min to 36 +/- 10 min (mean +/- S.D.) (p less than 0.005) and the gastric emptying rate from 79 +/- 13%/hour to 100 +/- 31%/hour (mean +/- S.D.) (not significant). During a stress period gastric emptying as a whole is delayed but this is mainly due to the prolongation of the lag phase. Our data also suggest that during the stress period gastric emptying is interrupted and reactivated once the stress period has ended.

Can we rely on 99Tcm-sestamibi gated tomographic myocardial perfusion imaging to quantify left ventricular function? A comparative study with classical isotopic techniques for the measurement of ejection fraction.

The assessment of left ventricular ejection fraction is an important element in the evaluation of cardiac performance, and one of the most commonly performed tests in nuclear cardiology. The aim of this study was to evaluate the accuracy and reliability of ejection fraction values calculated from ECG-gated myocardial perfusion single photon emission tomography (GSPET) in comparison with standard scintigraphic methods. Eight-frame gated SPET was recorded 60-90 min after the injection of 99Tcm-sestamibi at rest. The ejection fraction was calculated using a semi-automatic edge-detection technique based upon a threshold-searching method and compared with values obtained from first-pass (FPRNA) or equilibrium radionuclide angiography (ERNA) in 60 and 40 patients respectively with a broad range of ejection fraction values. Very good reproducibility was noted, with an inter- and intra-observer variability of -0.2 +/- 3.5% (range -7.6 to 6.9%, r = 0.97) and -0.2 +/- 2.2% (range -5.9 to 3.5%, r = 0.99) respectively. Similarly, a high concordance was found between GSPET and FPRNA and between GSPET and ERNA over the range of ejection fraction values (13 to 77%), the mean (+/-S.D.) difference being 0.8 +/- 3.8% (r = 0.97, P = N.S.) and 0.03 +/- 5.3% (r = 0.94, P = N.S.) respectively. Applying the Bland-Altman plot, no systematic bias of one method related to the other was observed, even at extreme ejection fraction values. Gated myocardial perfusion SPET with a 99Tcm tracer thus offers a unique opportunity to quantify cardiac performance and perfusion simultaneously and non-invasively.

Assessment of vertebral mineral content by means of a single-crystal scintillation camera.

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, 99Tcm and 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 cm2 field, 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-2 compared 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.

Quantification of 99Tcm-HMPAO brain SPET in two series of healthy volunteers using different triple-headed SPET configurations: normal databases and methodological considerations.

We evaluated the methodological issues underlying the assessment of normal confidence intervals, as used in clinically based region-of-interest (ROI) semi-quantification of 99Tcm-HMPAO brain SPET. At two different centres equipped with high-resolution, triple-headed gamma cameras, HMPAO SPET scans were performed on two groups of 24 and 15 healthy volunteers respectively. Together with an operator-defined analysis (ODA), a semi-automated analysis (SAA) was conducted on the normal datasets in one centre. Tests of intra- and inter-observer variability were performed. Repeat scans were performed within 72 h after the first to analyse short-term regional inter-study variations. The overall regional uptake showed significant differences in most regions between both normal datasets. Intra-observer and inter-observer reproducibility were on average within 4% for the ODA, while for the SAA it was less than 1%. Inter-study variations were excellent for both centres, ranging from -4% to +3% for most regions studied. The variability in clinical brain perfusion studies largely depends on the reproducibility of the data analysis technique. A semi-automated approach shows clear advantages over an entirely operator-defined approach. Intra-subject repeat studies show enough stability for use as reliable baseline measurements in the construction of a normal database or to allow activation studies with high sensitivity.

240 degrees: why not?

Single photon emission tomographic imaging of myocardial perfusion with 99Tcm-labelled agents is usually performed with single-detector gamma camera systems and 180 degrees anterior data collection. With multi-detector systems, reconstruction over 180 degrees and 360 degrees has been reported. We used a data set of normal subjects to compare both reconstruction methods. In addition, we tested an alternative approach, reconstructing data from 240 degrees acquisitions, excluding the right posterior views, which provide little myocardial information and which are responsible for a reduced signal-to-noise ratio. On the transverse slices, the known apical distortion with the 180 degrees reconstruction was not noted with the 360 degrees or 240 degrees reconstructions. Using semi-quantitative analysis of apical, mid-ventricular and basal short-axis slices, almost complete overlap was observed between the 240 degrees and 360 degrees circumferential profiles of our 20 normal volunteers, except in the inferior wall where a reduction in activity was noted. However, this finding was less pronounced with the 240 degrees than with the 180 degrees reconstruction. The frequent reduction in activity in the anterior wall was more prominent with the 180 degrees than with the 240 degrees and 360 degrees reconstructions. A 240 degrees acquisition represents a useful compromise between 180 degrees and 360 degrees imaging protocols when a single-detector device is used, allowing more homogeneous tracer distribution and a reduction in the apical distortion without material change of contrast or doubling of the acquisition time.