Search

OBJECTIVE To evaluate the myocardial ischaemia/viability in patients with acute myocardial infarction (AMI) using the ischaemia-avid agent (99m)Tc-HL91. METHODS Thirty-three AMI patients received 740 MBq (20 mCi) (99m)Tc-HL91, i.v., first and then 148-185 MBq (4-5 mCi) (201)Tl around 3 h later. The patient underwent initial imaging and 24 h late imaging, 10-15 min and 24 h later, respectively, after intravenous injection of (201)Tl. Myocardial segmental radioactive counts of (99m)Tc-HL91 were quantified by the region of interest technique. The segmental radioactive counts/pixel divided by those of the corresponding left ventricular cavities were ratios, which were compared among normal, ischemic/viable and fixed defect myocardium. The correlation analysis between the segmental scores from (201)Tl imaging and the ratios was performed. RESULTS The cross-talk of (99m)Tc into (201)Tl could be neglected in the present study. Out of the 33 AMI patients, the (99m)Tc-HL91 image quality analysis classified seven cases into excellent, accounting for 21%, eight cases into good, for 24%, eight cases into fair, for 24%, and 10 cases into poor, for 31%. The ratios were 1.16 (1.01, 1.35) ((median (25th to 75th percentile)), 1.15, 0.20 and 1.01 (0.86, 1.30), respectively, in normal, ischaemic/viable and fixed defect myocardium. Significant differences (chi2=17.2069, P=0.0002) were found in the ratios. The ratios of the ischaemic/viable myocardial segments were significantly higher than those of the fixed defect segments. Unexpectedly, the normal myocardial segments took up (99m)Tc-HL91, too, even slightly higher than the ischaemic/viable myocardial segments. CONCLUSIONS Myocardial uptake of (99m)Tc-HL91 is perfusion-dependent as well as ischaemia dependent. (99m)Tc-HL91 hypoxia imaging alone is not sufficient to identify ischaemic/viable myocardium. Dual-isotope imaging with (201)Tl and (99m)Tc-HL91 can characterize the myocardium into normal, ischaemic/viable and necrotic (scarred) myocardium.

Aim 9 9 m Tc-HL91 is a new hypoxia agent and can identify acutely ischaemic viable myocardium in a canine model using a standard gamma camera. The purpose of the study was to determine whether this tracer could be used todetect regional ischaemia in chronic ischaemic myocardium in a swine model. Method Using a porcine model of chronic myocardial ischaemia, five mini-pigs with proximal left anterior descending artery (LAD) stenoses were studied. Injection of 462.5 MBq (12.5mCi) 9 9 m Tc-HL91 was followed by imaging over 2 h. Coronary angiography and dipyridamole stress-re-injection 2 0 1 Tl single photon emission computed tomography (SPECT) were performed within 1 day of each other. Results None of the five pigs demonstrated positive hot 9 9 m Tc-HL91 uptake throughout the 2h imaging, whereas four of the five animals showed significant myocardial ischaemia on 2 0 1 Tl SPECT. The region of interest analysis of LAD/left circumflex artery count ratios at 1 and 2 h demonstrated similar 9 9 m Tc-HL91 uptake and retention in chronic ischaemic as well as non-ischaemic myocardium. Conclusion 9 9 m Tc-HL91 is inferior to 2 0 1 Tl in scintigraphic detection of chronic myocardial ischaemia.

The purpose of this retrospective study was to assess regional cerebral blood flow in patients after carbon monoxide intoxication by using brain single photon emission computed tomography and statistical parametric mapping. Eight patients with delayed neuropsychiatric sequelae and ten patients with no neuropsychiatric symptoms after carbon monoxide intoxication were studied with brain single photon emission tomography imaging with 99mTc-hexamethyl-propyleneamine oxime. Forty-four control subjects were also studied. We used the adjusted regional cerebral blood flow images in relative flow distribution (normalization of global cerebral blood flow for each subject to 50 ml x 100 g(-1) x min(-1) with proportional scaling) to compare these groups with statistical parametric mapping. Using this technique, significantly decreased regional cerebral blood flow was noted extensively in the bilateral frontal lobes as well as the bilateral insula and a part of the right temporal lobe in the patients with delayed neuropsychiatric sequelae as compared with normal volunteers (P< 0.005). In the patients with no neuropsychiatric symptoms, significantly decreased regional blood flow in the bilateral frontal lobes particularly on the left side was detected. There was a significantly decreased regional cerebral blood flow in the right frontal lobe and insula in the patients with delayed neuropsychiatric sequelae as compared to those with no neuropsychiatric sequelae. It is concluded that statistical parametric mapping is a useful technique for highlighting differences in regional cerebral blood flow in patients following carbon monoxide intoxication as compared with normal volunteers. The selectively reduced blood flow noted in this investigation supports the contention that the decrease following carbon monoxide intoxication may be prolonged and further worsen in the frontal lobe. In addition, the present study may help to clarify the characteristics of the pathophysiological alteration underlying delayed neuropsychiatric sequelae.

This phase I pilot study reports on (1) the safety and feasibility of 99Tc(m)-HL91, an amine oxime core radioligand that has shown oxygen dependent binding, and imaging; and (2) its usefulness for the visualization of local tumour recurrence of a biopsy proven squamous cell carcinoma of the head and neck (SCCHN) as compared to spiral computed tomogaphy (CT) and biopsy. Nine men (mean age 33 years, range 34-74 years) were prospectively included. For safety measurements, vital signs were recorded and serum chemical analysis carried out, with a complete blood cell count and urine analysis, and an ECG was performed prior to injection of 99Tc(m)-HL91 and repeated during the investigation. Single photon emission computed tomography (SPECT) scans of the head and neck, and of a standard, were performed at 2 h and 4 h post-injection of 740 MBq 99Tc(m)-HL91. Tumour-to-normal tissue background (T/N) ratios and percentage uptake were measured for all 99Tc(m)-HL91 scans. Spiral CT scans were obtained using a Somaton 4+ Siemens scanner within 1 week from the 99Tc(m)-HL91 scans. Based on CT and the 99Tc(m)-HL91 scan findings guided biopsies were performed. No adverse or subjective side effects were noticed. Vital signs, ECG findings, clinical laboratory, blood and urine assays remained stable in all patients. Spiral CT suggested local recurrence in 5/9 patients accompanied by nodal involvement in three, all of which proved positive on biopsy. 99Tc(m)-HL91 scintigraphy was false positive in one patient and true positive (TP) in 3/5 local recurrences and two out of three sites of lymph node involvement depicted by spiral CT. The mean T/N ratios at 2 h and 4 h in TPs were 1.28 (range 1.1-1.66) and 1.40 (range 1.0-1.6), respectively. The corresponding absolute percentages of 99Tc(m)-HL91 lesional uptake at 2 h and 4 h were mu = 0.05% (SD = 0.03%) and mu = 0.048% (SD = 0.035%). The findings suggest 99Tc(m)-HL91 is a safe radioligand and that metabolic binding in a large fraction but not all of local SCCHN recurrences may be expected. The inference that tumour 99Tc(m)-HL91 avidity could be a non-invasive measure of tumour hypoxia deserves however independent confirmation with needle oximetry.

Past analysis of dysbaric-induced cerebral perfusion defects, demonstrated by 99 Tc m -hexamethylpropylene amine oxime ( 99 Tc m -HMPAO) single photon emission tomography in divers using quantitative and /or univariate techniques, has resulted in considerable controversy regarding the significance of these lesions compared to those seen in control subjects, correlations with clinical findings and the role of 99 Tc m -HMPAO as a prognostic indicator in decompression sickness. We tried to address these problems by using a multivariate approach to a voxel-by-voxel analysis, involving the use of principal components, to determine ranges of normality in 50 reference controls. In subsequent images, abnormality was defined as 10 spatially connected voxels at an appropriate significance level of three standard deviations. The images of 50 divers with clinically diagnosed 'bends' were compared with those of a further 40 normal population controls with no previous history of loss of consciousness, head injury or dysbarism. The results showed that 19 of 50 divers with 'bends' and 3 of 40 population controls had significant perfusion defects, representing a significant difference between divers with dysbarism and population controls at the level P < 0.002. It is concluded that dysbarism causes significant cerebral cortical perfusion defects in affected divers both in 'silent' and symptomatic (clinically correlated) areas.

We studied 20 patients aged 46-69 years (mean 57 years) undergoing long-term haemodialysis (HD) and 20 age- and sex-matched controls with single photon emission tomography (SPET) and 99Tcm-hexamethyl-propyleneamine-oxime to look for regional abnormalities in cerebral blood flow (CBF) and their relation to cognitive dysfunction. Global hemispheric tracer uptake relative to the cerebellum was similar in both groups, but regional over cerebellar activity was significantly reduced in the frontal cortex (85.9 +/- 5.1 vs 90.4 +/- 5.3; P = 0.01) and thalamus (99.2 +/- 8.8 vs 104.9 +/- 8.4; P = 0.05) of the HD patients. Normalization to whole-brain activity also showed the frontal cortex to be hypoactive in the HD patients, while tracer uptake was increased occipitally. These regional differences were not explained by the presence of atrophy or cerebrovascular damage seen on brain magnetic resonance imaging. The HD patients scored significantly worse on cognitive tests such as the Mini Mental State Examination (23 +/- 4 vs 28 +/- 1; P < 0.001) and Mattis Dementia Rating Scale (114 +/- 24 vs 143 +/- 1; P < 0.001). Regional activity ratios did not correlate with cognitive test scores, however. Our results indicate a disturbed pattern of CBF in HD patients, although regional SPET abnormalities did not correspond to the severity of cognitive dysfunction.

Twenty-eight paediatric patients suffering from chronic sequelae of traumatic brain injury (TBI) were examined by EEG, radionuclide imaging with 99Tcm-hexamethylpropyleneamine oxime (99Tcm-HMPAO), computed tomography (CT) and, when available, magnetic resonance imaging (MRI), the results of which were evaluated retrospectively. Our findings indicate that neuro-SPET (single photon emission tomography) with 99Tcm-HMPAO is more sensitive than morphological or electrophysiological tests in detecting functional lesions. In our group, 15 of 32 CT scans were normal, compared with 3 of 35 SPET studies. SPET identified approximately 2.5 times more lesions than CT (86 vs 34). SPET was found to be particularly sensitive in detecting organic abnormalities in the basal ganglia and cerebellar regions, with a 3.6:1 detection rate in the basal ganglia and a 5:1 detection rate in the cerebellum compared with CT. In conclusion, neuro-SPET appears to be very useful when evaluating paediatric post-TBI patients in whom other modalities are not successful.

Individual responses of cerebral blood flow to acetazolamide are highly variable. We hypothesized that this may be due to interactions with cardiovascular diseases and medication. Therefore, we measured the haemodynamic effects of acetazolamide in patients with various cardiovascular disorders and evaluated whether these had any correlation with calculated cerebral perfusion reserve. Ten male patients aged 58 +/- 9 years (mean +/- S.D.) were studied with first-pass radionuclide ventriculography and echocardiography before and 20 min after the administration of 1 g acetazolamide. Systolic blood pressure fell from 133 +/- 21 to 128 +/- 19 mmHg (P0.05) and the cardiac output to total blood volume ratio increased from 0.85 +/- 0.18 to 0.92 +/- 0.11 (P = 0.05), indicating a 14% reduction in peripheral vascular resistance. In a further study, 15 patients aged 60 +/- 7 years (22 studies) were studied simultaneously with a nuclear stethoscope and 99Tc(m)-hexamethylpropyleneamine oxime single photon emission tomography before and after acetazolamide administration. The cardiac output ratio increased from 0.81 +/- 0.17 to 0.89 +/- 0.17 (P0.05) and showed a significant inverse correlation with calculated cerebral perfusion reserve. In conclusion, acetazolamide increases the cardiac output ratio and reduces systolic blood pressure, indicating reduced peripheral vascular resistance in patients with various cardiovascular diseases and medication. The increase in the cardiac output ratio is inversely related with calculated cerebral perfusion reserve. This helps to explain the high individual variability in calculated cerebral perfusion reserve.

99Tcm-hexamethylpropyleneamine oxime (99Tcm-HMPAO) is presently recognized as an effective radiopharmaceutical for in vitro white blood cell (WBC) labelling in addition to its widespread utility in cerebral blood flow imaging. While performing clinical studies in patients with a wide range of inflammatory diseases, the effect of the ligand and stannous ion quantity on the labelling efficiency (LE) of WBC was examined. A mean LE of 64 +/- 7% (n = 29) was achieved when the whole HMPAO kit was used for labelling. The LEs were 78 +/- 5% (n = 43), 83 +/- 3% (n = 37) and 85 +/- 5% (n = 18) when one-half, one-third and one-fifth of the lyophilized kit was used, respectively. This is in agreement with the reports of Sampson et al. and Lang et al., suggesting that the optimal formulation of the 99Tcm-HMPAO is a faction of the whole kit. Accordingly, fractionation of a freshly prepared 99Tcm-HMPAO kit into five parts for a high-efficiency WBC labelling is proposed, encouraging the more widespread use of 99Tcm-HMPAO in WBC labelling.

Brain 99Tcm-HMPAO single photon emission tomography (SPET) and 1H-MRS (proton magnetic resonance spectroscopy) were used to determine correlations between alterations in regional cerebral blood flow (rCBF) and changes in neuronal metabolites in 21 patients (28 examinations) with ischaemic cerebral infarction examined in different phases. rCBF was determined semi-quantitatively using Lassen's linearization algorithm. SPET provided evidence of the hypoperfused site of necrosis within a few hours after the acute event and alterations in rCBF were detected in both the infarcted and diaschistic areas at all stages. 1H-MRS was used to monitor the concentration of the following metabolites: N-acetyl-aspartate (NAA), creatine and phosphocreatine (CR + PCr), compounds containing choline (Cho) and lactate (Lac). A significant correlation was found between reduction in rCBF and a fall in NAA and Cr + PCr in both the acute and chronic phases, but not during "luxury perfusion' in the subacute phase. The presence of LAC in the infarcted area up to 9 months post-ictus was totally unexpected. Simultaneous SPET and 1H-MRS thus provides additional information regarding the physiopathogenesis of cerebral ictus by clarifying the relation between alterations in rCBF and biochemical neuronal changes. We believe that NAA and Cr + PCr concentrations are the best expression of agreement between flow and metabolism in infarcted areas, particularly with regard to hypoperfused areas not clearly detectable by magnetic resonance imaging in the early post-ictus stage.

An attempt was made to use 99 Tc m -d,l-cyclobutylpropylene amine oxime ( 99 Tc m -d,l-CBPAO) to label leukocytes. The radiochemical purity of 99 Tc m -d,I-CBPAO, labelling efficiency of leukocytes, cell viability of labelled leukocytes and stability of 99 Tc m -d,l-CBPAO-labelled leukocytes were calculated. In comparison with the commercial cell-labelling agent 99 Tc m -d,l-hexamethylpropylene amine oxime ( 99 Tc m -d,l-HMPAO), (1) the radiochemical purity of 99 Tc m -d,l-CBPAO was higher than that of 99 Tc m -d,l-HMPAO immediately after and 1, 2, 4, 6, 8 and 24 h after 99 Tc m labelling; (2) the labelling efficiency of 99 Tc m -d,l-CBPAO-labelled leukocytes was lower than that of 99 Tc m -d,l-HMPAO; (3) the viability of labelled white blood cells was high for both agents; and (4) the stability of 99 Tc m -d,l-CBPAO-labelled leukocytes was better than that of 99 Tc m -d,l-HMPAO after 1, 2, 4, 6, 8 and 24 h. In conclusion, although the labelling efficiency of 99 Tc m -d,l-CBPAO is lower, it is more stable than 99 Tc m -d,l-HMPAO and provides greater stability of 99 Tc m -d,l-CBPAO-labelled leukocytes. Therefore, 99 Tc m -d,l-CBPAO has the potential to replace 99 Tc m -d,l-HMPAO as a commercial leukocyte-labelling agent.

A considerable segment of the population of South Africa has a disease spectrum similar to those of the industrialized countries. However, a much larger proportion of its inhabitants comes from historically disadvantaged communities and is plagued by diseases typical of the developing world. Infectious diseases head the list as a cause of mortality in certain age groups. We have studied 108 patients presenting with a wide array of infections. Fifty-eight patients were examined with 67 Ga-citrate and with 99 Tc m -HMPAO-labelled leukocytes, 40 with leukocytes alone and 10 who had a high pre-test probability of tuberculosis with 67 Ga only. The sensitivity and specificity of 99 Tc m -labelled leukocyte scintigraphy in the 58 patients who had both studies were 89 and 84%, respectively, while the corresponding values for 67 Ga scintigraphy were 81 and 74%, respectively. The overall sensitivity and specificity for 99 Tc m -labelled leukocytes for detecting inflammatory sites in all 98 cases were 92 and 89%, respectively. Although labelled leukocytes were the better of the two agents for the early diagnosis of infections with a high probability of neutrophil infiltration, 67 Ga remains an excellent alternative. It is the first choice in patients in whom tuberculosis or a neoplastic process is suspected as a cause of fever. It is also safer to use in areas where labelling of leukocytes is inadvisable because of inadequate sterility or where the risk is high of infecting other patients or staff with HIV.

This review critically evaluates the current role of single photon emission tomography (SPET) imaging in the clinical management of patients with dementia. The classification of the dementias is discussed and the clinical and pathological features of the various dementing illnesses are described. Typical appearances on cerebral blood flow imaging are presented for each of the conditions, together with the findings on D 2 dopaminergic receptor and muscarinic receptor imaging where this is relevant. The review concludes with a section on the clinical value of SPET imaging in dementia. SPET imaging can make a valuable contribution to the accurate clinical differentiation of dementia, providing findings are interpreted in the light of neurological evaluation and structural imaging. The possible future role of SPET imaging in the prediction and evaluation of response to future therapeutic agents is discussed

Ten patients were studied prospectively afer severe closed head injury to determine the relationship between long-term clinical outcome and abnormalities detected by single photon emission tomography (99Tcm-HMPAO SPET), CT and MRI obtained within 60 days of injury. The ability of SPET to detect abnormalities not visualized by CT or MRI after cerebral trauma by the results of this study. Changes detected by SPET [global cerebral blood flow (gCBF) and number of regional cerebral blood flow (rCBF) deficits] soon after trauma were shown to be more closely correlated with long-term outcome than changes detected by MRI or CT. Templates were used to classify lesions by site and a multivariate analysis was undertaken to establish the importance of defect position in predicting clinical outcome. The results suggest that lesions in the temporal lobes, frontal lobes and basal ganglia are related to poor prognosis, and that SPET yields more useful prognostic data than the other methods.

The clinical experience with the Toshiba GCA-9300A single photon emission tomography (SPET) system is discussed along with typical acquisition protocols for various SPET studies. The system was used to perform SPET studies in normals and in a variety of brain and body disorders. Its three Anger-type gamma cameras forming a triangular aperture offer a substantial increase in sensitivity compared to a single rotating gamma camera. This has allowed the routine use of lead fanbeam super high-resolution collimators (SHR FB) for 99Tcm-hexamethylpropyleneamine oxime (HMPAO) brain SPET studies and high-resolution parallel-hole collimators (HR PH) for cardiac and other body studies. The resulting improvement in spatial resolution coupled with the ease of patient positioning and the greater patient throughput compared to a conventional tomographic gamma camera, will enhance the role of brain and body SPET for both routine and research purposes.

Thirty-seven children (11 girls, 26 boys; aged 2.8 +/- 2.2 years) with Kawasaki disease (KD) were included in the study. The biventricular functions were evaluated by equilibrium multigated blood pooling ventriculography (EMBPV) and the severity of carditis was decided by Tc-hexamethylpropyleneamine oxime (HMPAO) labelled white blood cell (WBC) heart scans (Tc-WBC). The results showed that 43% (16/37) of the KD cases with the severe carditis by Tc-WBC had the worst left ventricular ejection fraction (LVEF) (55.4 +/- 15.6%) and right ventricular ejection fraction (RVEF) (43.7 +/- 12.2%) by EMBPV; 24% (9/37) of the cases with the mild carditis had the best LVEF (63.5% +/- 8.2%) and RVEF (53.7% +/- 11.2%); the remaining 32% (12/37) had moderately severe carditis and biventricular function (LVEF: 58.2 +/- 17.2% and RVEF: 46.9 +/- 19.5%). Because Tc-WBC cannot only detect the severity of carditis but also predict impairment of ventricular function accurately, the choice of Tc-WBC should be preferable for KD-a common inflammatory cardiovascular disease in children.

This study assesses the sensitivity of the baboon model under anaesthesia to determine by single photon emission computed tomography (SPECT) and 99Tcm-hexamethylpropyleneamine oxime (HMPAO) dose responses from drugs (acetazolamide) with known regional cerebral blood flow (rCBF) effects on humans. Three dosages of acetazolamide were chosen: 250, 500 and 750 mg. The effects of these were studied by conventional SPECT 5 min after intravenous (i.v.) administration and compared to previous studies of rCBF with the baboons under anaesthesia only. An additional study concerned the effect of 500 mg acetazolamide at 15 min after administration. Haemodynamic parameters and blood gases were also monitored. No statistically significant regional effects were noted (P > 0.05). The largest increase in CBF (39%) was observed from 500 mg acetazolamide after 5 min. This was statistically significantly different from control values only at a 10% level of confidence; then followed a 27% increase above control values after 750 mg (5 min). At 15 min 500 mg yielded values lower by 10% than the high dose. No effects were observed from 250 mg acetazolamide; only pO2 showed changes which largely confirm the CBF findings. The model did not give significant results at a 5% level of confidence but large fluctuations were observed, also in the haemodynamic and blood gas values. At a 10% level a significant dose response was confirmed for acetazolamide.

The aim of this study was to compare 99Tcm-teboroxime and 201T1 myocardial studies with particular regard to the classification of perfusion defects as reversible or fixed. Twenty patients with a history of previous myocardial infarction and suspected effort ischaemia underwent exercise 201T1 scintigraphy with early (4 h) redistribution and reinjection scans, exercise and rest 99Tcm-teboroxime imaging and coronary angiography. Using a qualitative scoring of static planar images, the perfusion defects were classified as reversible or fixed. 201T1 and 99Tcm-teboroxime gave comparable results in the evaluation of the individual vessels (sensitivity 65%, specificity 80% and 85%, respectively). The stress-redistribution 201T1 sequence classified 45 defects as reversible and 28 as fixed, the stress-rest 99Tcm-teboroxime studies classified 47 as reversible and 26 as fixed (NS). The stress-reinjection 201T1 images, however, characterized 64 defects as reversible and nine as fixed (P < 0.005 versus 201T1 redistribution, P < 0.0005 versus 99Tcm-teboroxime rest). In conclusion, this study shows that rest 99Tcm-teboroxime and 201T1 redistribution give comparable results but that significantly more defects are classified as fixed by 99Tcm-teboroxime than by 201T1 if reinjection of the latter tracer is performed.

The sensitivity and specificity of 99Tcm-hexamethylpropyleneamine oxime (HMPAO) single-headed single photon emission computed tomography (SPECT) in dementia were evaluated in elderly patients with a mean age of 84 years suffering from dementia (n = 59) and compared to an age- and sex-matched control group with normal cognitive function (n = 14). The demented patients were classified as suffering from primary degenerative dementia (PDD, n = 51) based on DSM-III-R criteria. Moreover, PDD patients were divided into three subgroups of severity of cognitive impairment, according to their Folstein score. Multi-infarct dementia (MID, n = 8) was diagnosed based on clinical features, computed tomographic findings and Hachinski ischaemic score. Images were assessed qualitatively by visual interpretation of shades of colour in cortical regions. A SPECT defect confined to the frontal, parietal, temporal or (parieto) occipital lobe was defined as one lesion. The mean number of SPECT lesions was 1.4 (range 0-4) in the control group, 2.4 (range 0-8) in the PDD group and 2.9 (range 2-5) in the MID group and showed a significant difference (P < 0.02) between groups. To obtain an acceptable level of specificity of 64.3%, a cut-off value of three lesions had to be chosen. In the PDD group, sensitivity was then 25% for the mildly, 43.8% for the moderately and 46.7% for the severely affected PDD subgroup. In the MID group sensitivity was then 75%. Interestingly, in this elderly patient population the location of lesions was homogenously distributed in all groups, including the control group.

Myocardial imaging with 99Tcm-hexamethylpropylene amineoxime (HMPAO)-labelled white blood cells (Tc-WBC) was used to detect carditis and differentiate rheumatic fever (RF) and inactive rheumatic heart disease (IRHD). Ten cases of RF and 15 cases of IRHD were studied, and the results revealed 60% (6/10) of the cases of RF with carditis, but none of the cases (0/15) of IRHD with carditis. There was significant difference (P less than 0.05, by Fisher's test) between RF and IRHD. In our preliminary conclusion, Tc-WBC heart scanning may be a noninvasive method for evaluating the existence of carditis in cases of RHD and in the differentiation of RF and IRHD.

When preparing 99Tcm-exametazime, it is important to use sodium 99Tcm-pertechnetate that is less than 2 h old. The addition of sodium iodide (NaI) to 99Tcm-pertechnetate is known to extend this time to 6 h. This paper describes a technique for implementing this in routine practice. Sterile kits consisting of 440 micrograms NaI and 1.0 ml sodium chloride injection in a vial with a nitrogen atmosphere were prepared and stored at room temperature, 4 degrees C and -22 degrees C. Titrimetric analysis of iodide showed that under each storage condition, kits were stable for 8 weeks. To determine the effectiveness of the kits, the radiochemical purity (RCP) of 99Tcm-exametazime was measured by high-performance liquid chromatography (HPLC). The validity of this technique was determined by simultaneous analysis with the conventional thin-layer/paper chromatography (TLC/PC) technique on 24 occasions, over a range of RCP (94.5-54.6%). Radiochemical purities measured by HPLC and TLC/PC were 81.2 +/- 10.2 and 81.5 +/- 10.5%, respectively, and did not differ significantly (P greater than 0.30). The correlation between the techniques was high (r = 0.98). 99Tcm-exametazime was prepared using 1 h-old 99Tcm-pertechnetate, 6 h-old 99Tcm-pertechnetate and 6 h-old 99Tcm-pertechnetate dispensed in a NaI kit. At the recommended expiry time for this radiopharmaceutical, i.e. 30 min after preparation, RCPs were found to be 88.4 +/- 2.4, 80.9 +/- 2.0 and 89.3 +/- 3.0%, respectively (n = 5 for each technique).(ABSTRACT TRUNCATED AT 250 WORDS)

The aim of this study is to determine whether white blood cell imaging in inflammatory conditions is due to a blood pool effect as a result of an increased vascularity and vascular permeability, or whether cellular migration is the major contributing factor. It will be shown that white cell uptake is a specific phenomenon in the rheumatoid knee joint and not just a blood pool effect.

To evaluate the usefulness of 99Tcm-hexamethylpropyleneamine oxime (HMPAO) single photon emission computed tomography (SPECT) in suspected dementia we studied 160 consecutively imaged elderly patients from our hospital's memory disorder clinic. The diagnosis was based on clinical data, laboratory tests, neuropsychological examination, computed tomography (CT) and EEG. The patients were divided into six diagnostic categories: Alzheimer's disease (AD), multi-infarct dementia (MID), frontal lobe-type dementia (FTD), vascular encephalopathy not fulfilling the criteria of dementia, specific organic conditions, and psychiatric disorders. SPECT images were assessed without knowing the clinical diagnosis, and divided into AD pattern, FTD pattern, MID pattern, abnormal but unclassifiable, and normal. Twenty-three of 36 patients with clinical AD, 25/33 patients with clinical MID, and 2/5 patients with clinical TFD had compatible SPECT patterns. SPECT distinguished AD from MID in the majority (80%) of cases. In patients with depression or anxiety SPECT was abnormal in 16/21 cases, suggesting that SPECT may give early clues to the presence of an underlying organic disease in such elderly patients. Thus, SPECT with 99Tcm-HMPAO seems to be useful in the diagnosis of suspected dementia.

Background Favourable effects of cytotoxic chemotherapy for tumours are characterized by the reduced accumulation of radiotracers such as 9 9 m Tc sestamibi (MIBI). Anti-angiogenic therapy is primarily cytostatic; consequently, its influence on tracer accumulation may differ from that of cytotoxic treatments. Methods Anti-angiogenic therapy employing 2-methoxy-estradiol was administered in mice bearing subcutaneous xenografts of LS180 colon cancer cells. The effects of chemotherapy with 5-fluorouracil were examined as a cytotoxic counterpart. Treatments were conducted for 4 days from day 8. Distribution of 9 9 m Tc-MIBI and 9 9 m Tc-HL91, a hypoxic marker, was observed on days 8 and 12. Oxygen tension (Po 2 ) in tumours was measured by a microelectrode. Cellular uptake of tracers was examined in vitro in normoxic and hypoxic conditions. Results 9 9 m Tc-MIBI accumulation decreased with increasing tumour weight when no treatment was conducted. Tumour growth was suppressed by anti-angiogenic therapy and chemotherapy. 9 9 m Tc-MIBI accumulation in tumours decreased after chemotherapy as compared to pre-therapeutic values, whereas accumulation of 9 9 m Tc-HL91 increased. In contrast, accumulation of tracers did not significantly change after anti-angiogenic therapy as compared to that observed pre-therapeutically. Tumour Po 2 decreased with increasing tumour volume when no treatment was conducted. Chemotherapy reduced Po 2 in tumours. Po 2 in tumours treated with anti-angiogenic therapy was as high as that observed before treatment. 2-Methoxyestradiol or 5-fluorouracil did not significantly affect tracer accumulation in cells under both normoxic and hypoxic conditions in vitro. Conclusion These findings indicate that scintigraphic assessment of therapeutic efficacy of anti-angiogenic therapy should be performed from a perspective distinct from that of cytotoxic treatment.

The appearance of the gallbladder in images of patients undergoing 99 Tc m -hexamethylpropylene amine oxime ( 99 Tc m -HMPAO) autologous white cell scans (AWCSs) was compared before and after the introduction of fasting in the white cell scan protocol in our department. Before February 1995, when fasting was not required as a condition of the test, gallbladders were identified in 10 and 13% of 128 patients at 1 and 3 h, respectively. After February 1995, when fasting was imposed for the duration of the AWCS procedure, gallbladders were identified in 44 and 58% of 139 patients undergoing an AWCS at 1 and 3 h, respectively (P < 0.01). While further studies are required to show that fasting affects the false-positive rate, the results suggest that the degradation products of 99 Tc m -HMPAO may be retained in the biliary system longer during fasting. Fasting should therefore be included in the protocol for an AWCS, particularly in the evaluation of inflammatory bowel disease (IBD) when 99 Tc m -HMPAO is the cell label used.

A prospective trial was performed to assess the accuracy of 99 Tc m -methoxyisobutyl isonitrile ( 99 Tc m -MIBI) scintimammography and X-ray mammography in 18 patients (mean age 58 years, range 46-79 years) with suspected recurrent breast cancer in the breast and/or loco-regional tissues. All patients had been diagnosed to have breast cancer 1-23 years before scintimammography. Two patients had undergone mastectomy, so that a total of 34 breasts were studied with X-ray mammography and with prone-lateral and anterior scintimammography. Any abnormalities on X-ray mammograms and scintimammograms were noted, as was any additional local or nodal uptake of 99 Tc m -MIBI. The nature of any lesion seen with either modality, or in which there was a clinical suspicion of recurrence, was confirmed by cytological or histological examination of tissue samples. There were nine breasts with recurrent cancer in eight patients. X-ray mammography identified six of these cancers. 99 Tc m -MIBI scintimammography identified eight of nine recurrent breast cancers (the one cancer not seen was positive on X-ray mammography). In the 26 breasts without cancer, two were reported as having changes consistent with cancer and one was reported equivocal. There were three false-positive and one equivocal scintimammograms. The accuracy of 99 Tc m -MIBI scintimammography within the breast (85%) was similar to X-ray mammography (82%). Axillary lymph node recurrence occurred in five patients, four of whom were positive with 99 Tc m -MIBI. An additional patient had focal uptake of 99 Tc m -MIBI at the site of recurrent cancer on the anterior chest wall. In conclusion, 99 Tc m -MIBI scintimammography may provide useful complementary information in patients with suspected recurrence of cancer in the breast or loco-regional tissues.

The diagnosis of central nervous system (CNS) involvement appears to be a major problem in systemic lupus erythematosus (SLE), especially when the clinical signs are non-specific or neuroimaging is unremarkable. Two SLE patients with mild neuropsychiatric manifestations were studied with magnetic resonance imaging (MRI), single photon emission tomography (SPET) and localized proton magnetic resonance spectroscopy (H-1 MRS). MRI was normal in both patients. SPET revealed areas of hypoperfusion in both patients. H-1 MRS demonstrated metabolic abnormalities in the regions corresponding to the hypoperfused areas. A correlation between H-1 MRS and SPET was noted: patients with mild neuropsychiatric SLE may have disturbances evident on SPET and H-1 MRS in the presence of normal anatomy on MRI, suggesting that CNS involvement in SLE has very strong physiological and neurometabolic components in individual patients.

The method described by Weisner et al. for stabilizing 99Tcm-hexamethylpropylene amine oxime ( 99 Tc m -HMPAO) with cobalt chloride hexahydrate solution is the most promising developed to date. The aim of our work was to study the behaviour of cobalt during the labelling of leukocytes with 9 9 Tc m -HMPAO stabilized in vitro using this method. Three parallel labellings were carried out using six blood samples taken from polycythaemic patients. The first set of labellings was performed using 99 Tc m -HMPAO, the second set using 99 Tc m -HMPAO stabilized with cobalt chloride hexahydrate solution 'spiked' with 57 Co-chloride, and the third set using 57 Co-chloride solution alone. Measurements of radioactivity content were made on the leukocyte pellets after washing at five time points post-labelling (t = 0, 30 min, 1 h, 2 h and 4h). The data show that leukocytes do not retain cobalt during labelling with stabilized 99 Tc m -HMPAO. Studies carried out in parallel demonstrated that the presence of cobalt in the cell-labelling medium had no effect on cell viability.

The aim of this study was to evaluate 99 Tc m -labelled phenylene imine phenol ( 99 Tc m -Ph(IP) 2 ) as a leukocyte label. The 99 Tc m complex exhibits a neutral lipophilic character. The radiochemical purity of the 99 Tc m -Ph(IP) 2 was high both soon after labelling (94.5 ± 1.2%, n = 7) and at 24 h (89.7 ± 1.0%, n = 7). In a comparative study, the labelling efficiency of 99 Tc m -Ph(IP) 2 and 99 Tc m -hexamethylpropylene amine oxime ( 99 Tc m -HMPAO) labelled leukocytes was 47.1 ± 3.5% (n = 7) and 58.5 ± 7.0% (n = 7) respectively. The viability of labelled leukocytes was greater than 90% for both 99 Tc m complexes. The elution ratios of labelled leukocytes with 99 Tc m -Ph(IP) 2 at 1, 4 and 24 h were 10.1 ± 3.5%, 17.2 ± 2.7% and 23.0 ± 2.4% (n = 7) respectively, while those with 99 Tc m -HMPAO were 10.8 ± 1.2%, 18.3 ± 2.0% and 37.0 ± 3.7% (n = 7) respectively. In conclusion, 99 Tc m -Ph(IP) 2 , with good stability and significant leukocyte labelling efficiency, is a potential leukocyte label.

We assessed cerebral blood flow in 78 diabetic patients (40 Type 1 and 38 Type 2) with no previous history of central nervous system disease using 99 Tc m -hexamethylpropylene amine oxime ( 99 Tc m -HMPAO) single photon emission tomography (SPET) and found areas of severe hypoperfusion in 36% of them. All cerebral anatomical regions showed abnormalities related to hypoperfusion, but they were most frequently seen in the fronto-temporal region, followed by the occipital and parietal regions. 99 Tc m -HMPAO SPET has been shown to be able to detect subclinical alterations in blood flow in diabetics, a finding that may account for the high prevalence of cerebrovascular disease seen in these patients. This technique could, therefore, play an important role in future preventative strategies.

Four methods of calculating the activity of 99Tcm-hexamethylpropyleneamine oxime to be administered in cerebral blood flow investigations of children were evaluated in patient studies. Three of the methods were based on the size of the child. We also constructed a theoretical dosage model based on physiological data and attenuation effects. The aim of the study was to find a dosage calculation method that gave the same image quality for children of all ages as well as for adults. The results showed that the dosage method based on body weight is the only one of the four methods that does not exhibit an age-dependent variation in image quality and therefore this method is recommended.

Luxury perfusion is a well-known phenomenon that can mask ischaemic lesions in patients with cerebral infarction, thus making diagnosis difficult. In this study, we evaluated the incidence of luxury perfusion over a 3-week period following a stroke episode. The usefulness of crossed cerebellar diaschisis (CCD) as a complementary feature in the diagnosis of cerebral infarction was also evaluated using 99 Tc m -hexame-thylpropyleneamine oxime ( 99 Tc m -HMPAO) brain single photon emission tomography (SPET). Twelve patients diagnosed as having a hemispheric ischaemic stroke of the middle cerebral arterial territory were enrolled in the study. Each patient underwent a total of four 99 Tc m -HMPAO brain SPET examinations, 1 day, 1 week, 2 weeks and 3 weeks following the stroke episode. Our results show that the incidence of luxury perfusion was 67% (8/12) after 1 week, 75% (9/12) after 2 weeks and 83% (10/12) after 3 weeks. The incidence of CCD was 33% (4/12) after 1 day, 50% (6/12) after 1 week, 42% (5/12) after 2 weeks and 33% (4/12) after 3 weeks. We conclude that the detection of cerebral infarction is difficult 2 weeks or more after a stroke episode. The interval between the stroke episode and examination must be considered when reading the 99 Tc m -HMPAO image. In addition, CCD may be helpful for the diagnosis of cerebral infarction within the first week after a stroke episode, especially in cases of an unidentified ischaemic region on the 99 Tc m -HMPAO hemispheric image. However, the value of CCD is limited 2 weeks or more following the stroke episode.

The aim of this study was to facilitate the diagnosis of brain death based on semi-quantitative parameters as well as the other scintigraphic signs and symptoms of brain death. Altogether, 72 studies were performed in 54 patients (35 males, 19 females) to evaluate the diagnoses of brain death which were confirmed in 49 cases. Perfusion dynamic acquisition and static imaging were performed after the intravenous injection of 700-900 MBq 99Tcm-hexamethylpropyleneamine oxime (HMPAO). We reviewed the following parameters retrospectively: (1) qualitative visual assessment of the presence or absence of delayed HMPAO deposition in the brain area; (2) qualitative visual assessment of a 'three-pronged fork' of the cerebral arteries during the first-pass study; (3) any evidence of 'hollow skull' during the first-pass study; (4) any evidence of 'hot nose'; (5) blood flow index (i.e. the ratio of the area under the brain time-activity curve vs that under the curve for the carotid arteries); and (6) delayed uptake index (i.e. the ratio of HMPAO deposition in the brain vs that in the facial regions of interest). We were able to demonstrate the validity of individual signs and symptoms and to confirm the highly reliable nature of semi-quantitative scintigraphic parameters.

To investigate the utility of neuroreceptor imaging in ischaemic cerebrovascular disorders, dual-tracer autoradiography using 99 Tc m -hexamethylpropyleneamine oxime (HMPAO) for the evaluation of cerebral blood flow and 125 I-iomazenil for the evaluation of central-type benzodiazepine receptor density was performed in experimental brain ischaemia created by occlusion of the unilateral middle cerebral artery of the rat. In the acute phase of ischaemia, 125 I-iomazenil accumulation showed less of a decrease than 99 Tc m -HMPAO in the cerebral cortex of the lateral convexity and in the lateral segment of the caudate putamen in the lesioned cerebral hemisphere. In the sub-acute phase, both 125 I-iomazenil and 99 Tc m -HMPAO accumulation increased in the lesion compared with the acute phase. A large accumulation of 99 Tc m -HMPAO and 125 I-iomazenil in the lesion was considered to be due to luxury perfusion and penetration of 125 I-iomazenil hydrophilic metabolites from the blood into the brain tissue through the altered blood-brain barrier. In the chronic phase, 125 I-iomazenil accumulation showed a more marked decrease than 99 Tc m -HMPAO in the lesion. Moreover, the ipsilateral thalamus, which is remote from the lesion, revealed decreased 125 I-iomazenil accumulation despite normal 99 Tc m -HMPAO accumulation. Since the central-type benzodiazepine receptors are principally located not on the glial cells but on the neurons, the receptor density may exhibit a change that parallels the neuron density. These results suggest that central-type benzodiazepine receptor imaging is useful for the evaluation of neuronal damage when used in conjunction with brain perfusion imaging in ischaemic cerebrovascular disorders, except in the sub-acute phase.

The potential use of regional cerebral blood flow (rCBF) single photon emission tomography (SPET) imaging with 99Tcm-hexamethylpropyleneamine oxime (HMPAO) in the management of divers who have undergone a form of decompression sickness (DCS) was investigated using texture analysis. We imaged 50 divers, 10 of whom had only experienced DCS which had been categorized as Type 1, 20 of whom had a history of DCS classified as Type 2 and 20 of whom had not suffered an episode of DCS. A number of divers who had experienced Type 2 DCS had also had incidents of Type 1. The reconstructed SPET images were pre-processed and analysed using a first-order texture analysis technique based on a grey level histogram. The results showed that there was a significant textural difference between the divers who had only suffered episodes of DCS Type 1 and the diving controls and a difference between the divers with a history of Type 2 and the diving controls. No differences were found between the two groups of divers who had a history of DCS. This result suggests that DCS produces a detectable change in 99Tcm-HMPAO SPET brain images. However, the segmentation between the groups investigated was not complete and so the usefulness of this approach appears limited in individual cases but may provide useful information about the effects of different diving practices.

In order to synthesize three-dimensional information on relative regional blood flow (rCBF) from the cortical grey matter in 99Tcm-hexamethylpropyleneamine oxime (HMPAO) single photon emission tomographic (SPET) images into a single two-dimensional 'cortical peel' (CP) image, we developed a program that performs cylindrical transformation of SPET data. A sub-routine of this program performs measurements of cortex-to-cerebellum rCBF ratios for 54 cortical regions in the CP image. This program was used to establish a normative database derived from 30 young normal control subjects aged 28.7 +/- 6.9 years. The database was then used to express cortex-to-cerebellum rCBF ratios in four colour-coded ranges of normal standard deviation of the mean rCBF ratio across the cortical regions in the CP image. This CP method was implemented for 30 clinical HMPAO SPET studies in patients (n = 30, aged 71.8 +/- 4.2 years) with suspected dementia as well as several studies in aged healthy subjects (n = 8, aged 67 +/- 9.8 years). In 25/30 (83%) patients, all abnormalities seen on the tomographic display were evident on the corresponding CP image. No aged healthy subjects showed abnormalities on either the tomographic display or the corresponding CP image. An advantage of this technique is that the extent and severity of rCBF abnormalities are readily appreciated in one single image. This technique, in conjunction with the conventional multi-slice tomographic display, was a useful tool in identifying various patterns of rCBF abnormalities in the patients with clinically suspected dementia.

The clearance rate of an inhaled aerosol of a lipophilic complex, 99Tcm-hexamethylpropyleneamine oxime (99Tcm-HMPAO), was compared with that of a hydrophilic complex, 99Tcm-diethylenetriamine pentaacetate (99Tcm-DTPA), in nine normal subjects and in eight patients with idiopathic pulmonary fibrosis (IPF). Data were acquired as follows. The subjects were placed supine with their back against the scintillation camera and breathed aerosol for 2 min; pulmonary radioactivity was then monitored for 30 min. A time-activity curve (TAC) was generated from the region of interest (ROI) over the periphery of each lung field and a computer program was then used to calculate percentage clearance per minute (k) in each lung. The mean (+/- S.E.M.) rate of clearance of 99Tcm-DTPA (k = 1.31 +/- 0.13% min-1) was not significantly different from that of 99Tcm-HMPAO (k = 1.32 +/- 0.27% min-1, P0.025) in the normal subjects. However, 99Tcm-DTPA clearance was 1.91 +/- 0.27% min-1 and 99Tcm-HMPAO clearance 0.78 +/- 0.17% min-1 in eight patients with IPF (P0.001, 99Tcm-DTPA vs 99Tcm-HMPAO). By regression analysis using a multiplicative model, both values correlated fairly [r = -0.71, y = exp (0.08-0.85 ln chi); P0.005], with a change in clearance rate in the opposite direction in all eight patients. The results of our study demonstrate that the pulmonary clearance of 99Tcm-HMPAO is different from that of 99Tcm-DTPA in IPF.

Regional distribution of cerebral blood flow was determined semi-quantitatively with 99Tcm-HMPAO brain SPET under basal conditions in Type 1 (insulin-dependent) diabetic patients of recent onset and longer disease duration, and related to metabolic control and history of hypoglycaemic events. Long-term diabetic patients showed significantly more alterations in regional cerebral blood flow than diabetics of recent onset and healthy controls. Regional hypoperfusion, predominantly localized in the fronto-temporal cortex, was almost exclusively observed in patients with long-term diabetes. The latter finding was related to lower HbA1c levels (i.e. better metabolic control) and to the frequency of impending hypoglycaemia, but not to age of the patient, duration of diabetes or to chronic diabetes complications. The incidence of hypoperfusion was comparable in patient groups with or without a medical history of hypoglycaemic coma. However, regions of hypoperfusion were larger in the patients who had experienced hypoglycaemic coma. It is concluded that regional cerebral hypoperfusion in long-term Type 1 (insulin-dependent) diabetics, as evidenced by HMPAO-SPET can be related to the frequency and degree of hypoglycaemic events and to tight metabolic control, which is however at the expense of an increased risk of recurrent hypoglycaemia.

Prosthetic vascular graft infection is a relatively uncommon complication of peripheral vascular surgery. We retrospectively analysed technetium-99m-d,l-hexamethylpropylene amine oxime (99Tcm-d,l-HMPAO) labelled leukocyte scans of 21 patients with a suspected vascular graft infection. Operative findings, bacteriological cultures, radiological findings or clinical follow-up were used to confirm the diagnosis. We found eight true-positive and six true-negative cases. There were no false-positive scintigraphic diagnoses. The false-negative rate was 33% (n = 7). Our results show a sensitivity of 53%, a specificity of 100% and an accuracy of 66%. The conclusion is that a negative 99Tcm-d,l-HMPAO-labelled leukocyte scan is of limited value in ruling out a vascular graft infection. A combination of computed tomography (CT-scan) and a 99Tcm-d,l-HMPAO-labelled leukocyte scan is probably the most efficient way of diagnosing a vascular graft infection.

Several commercially available 99Tcm radiopharmaceuticals were tested as possible white blood cell labelling agents. Labelling efficiency, labelling stability and white blood cell adherence were measured in vitro. White blood cells were not successfully labelled with mebrofenin, disofenin, gluceptate or dimercaptosuccinic acid but were successfully labelled with exametazime, albumin colloid, sulphur colloid, sestamibi and teboroxime. Exametazime had the highest mean labelling efficiency of 79%. Labelling efficiency was 5-14% with albumin colloid, sulphur colloid, sestamibi and teboroxime. Labelling stability was high (> 95% at 4 h and > 80% at 24 h) for all agents except sestamibi (52% at 4 h and 5% at 24h). Exametazime did not alter white blood cell adherence. Albumin colloid, sestamibi and teboroxime decreased adherence and sulphur colloid increased adherence. Exametazime appears to be the best agent for labelling white blood cells. Teboroxime, however, is a new agent for labelling white blood cells which deserves further investigation.

A new method for the analysis of regional cerebral blood flow (rCBF) studies, the 'Min-Max' method, was compared with the conventional method, the 'Average' method. Regional CBF was examined by single photon emission computed tomography (SPECT) using 99Tcm-hexamethylpropyleneamine oxime (99Tcm-HMPAO). The two methods were used to quantify the rCBF in a population of patients with various dementia disorders, and in healthy controls. Results from a phantom were also used. In the Average method the average counts per pixel (cp-1) within irregular manually drawn regions of interest (ROIs) was registered. In the Min-Max method the minimum cp-1 and maximum cp-1 within rectangular ROIs were registered for white and grey matter, respectively. The relative rCBF (rrCBF) was calculated as the ratio between the regional and cerebellar values. The Min-Max method gave systematically lower values for rrCBF in the white matter, in both clinical studies, and in the phantom, compared to the Average method. No difference was found in the grey matter results. The variability in rrCBF in the phantom study was greater with the Min-Max method than with the Average method, but this effect was counteracted in the clinical studies by a smaller interobserver error. The average regional differences between patients and controls appeared greater with the Min-Max method than with the Average method. The Min-Max method proved to be more simple to execute, involved a smaller observer error, and with respect to ability to distinguish patients with dementia disorders from controls, it appears to function at least as well as the accepted Average method.

The value of hexamethylpropyleneamine oxime (HMPAO) single photon emission computed tomography (SPECT) as a diagnostic test for Alzheimer's disease (AD) was assessed in 44 patients attending a Memory Clinic. A comprehensive physical and psychiatric examination and detailed neuropsychological tests were used to arrive at a clinical diagnosis, in accordance with NINCDS-ADRDA criteria. The mean patient age was 69 (range 59-84) years, and the mean score on the Mini-Mental State Examination (MMSE) was 24 (range 7-30). Of 26 patients with a clinical diagnosis of AD, only 15 demonstrated a scan pattern strongly suggestive of AD. Four scans were normal, four showed evidence of ischaemic change and three were in the category 'other', one of which showed bilateral frontal hypoperfusion, but normal temporoparietal flow. Of the eight patients considered by clinical criteria to be non-demented, no scan showed an AD pattern, but three showed an ischaemic pattern. Both of the patients diagnosed clinically as suffering from multi-infarct dementia showed SPECT scan evidence of ischaemic change. Of the remaining eight patients with other clinical diagnoses only one scan suggested AD. We conclude that the HMPAO SPECT scan appearances which arise from AD in the early stages of the disease do not on their own allow the disease to be accurately diagnosed, but they may be useful if interpreted in conjunction with other imaging techniques.

The aim of this study was to describe the effectiveness of 99Tcm-hexamethylpropyleneamine oxime (99Tcm-HMPAO) brain single photon emission computed tomography (SPECT) in the assessment of the regional cerebral blood flow (rCBF) in amphetamine abusers. Twenty-one amphetamine abusers were included and 99Tcm-HMPAO brain SPECT performed to evaluate rCBF. The drug-using periods ranged from 1 month to several years. The demonstrated neuropsychogenic symptoms and signs of the abusers were from normal presentation to various neurologic complications. The brain SPECT scans were interpreted visually as either normal or abnormal. The degree of abnormality was classified into mild or severe. The results revealed that (a) most SPECT studies in abusers show small defects (95%, 20/21 cases); 71% (15/21) of cases revealed multiple defects over both hemispheres (classified as severe); 24% (5/21) of the cases had focal defects (classified as mild); and only one case (5%, 1/21) demonstrated a normal SPECT finding; (b) the degree of abnormality on SPECT scans was not related to the dose and duration of drug use or the severity of the neuropsychiatric symptoms and signs. In conclusion, 99Tcm-HMPAO brain SPECT is a sensitive but not specific test for neuropsychogenic abnormalities associated with amphetamine abuse.

High-grade astrocytoma represents the most common primary malignant brain tumour in the adult, and is associated with high morbidity and mortality rates. The aim of this study was to investigate the prognostic value of 99Tcm-hexamethylpropyleneamine oxime (HMPAO) brain single photon emission computed tomography (SPECT) in predicting neurological function and tumour therapy response after surgical resection of astrocytoma. The correlation between 99Tcm-HMPAO studies and other noninvasive methods [computed tomography (CT), magnetic resonance imaging (MRI) and 201Tl (SPECT)] was evaluated. The clinical population included 21 patients with previous surgical debulking of astrocytoma. All patients were evaluated with 99Tcm-HMPAO brain SPECT. Seven patients, who suffered progressive clinical deterioration after radiotherapy, underwent dual-isotope SPECT imaging with 201Tl and 99Tcm-HMPAO. Neurological examinations and CT were performed in all patients. Magnetic resonance imaging was performed in seven patients. Prior to radiotherapy and/or chemotherapy, the patients with neurological improvement during the follow-up evaluation commonly showed less intense abnormal 99Tcm-HMPAO uptake than the patients without neurological improvement. In addition, after therapy none of the former patients had increased 99Tcm-HMPAO uptake. Most patients without neurological improvement had evidence of high focal uptake. Computed tomography and MRI usually demonstrated pathological contrast enhancement regardless of the presence or absence of improvement of neurological function. Foci of high 201Tl accumulation were observed on SPECT images in five patients. In four of these patients, the 99Tcm-HMPAO was greater than in normal brain, and in two patients the 99Tcm-HMPAO uptake was lower than in normal brain. One patient with decreased 99Tcm-HMPAO uptake in a medium-sized lesion had a normal 201Tl study. Our hypothesis that 99Tcm-HMPAO SPECT may be useful for providing prognostic information after surgical debulking of astrocytoma seems to be promising. Further studies are needed to document this new important role of 99Tcm-HMPAO SPECT.

A comparative study of neutrophil pharmacokinetics and distribution between normal volunteers and patients with rheumatoid arthritis (RA) is presented. White cell viability was confirmed by prominent localization of activity in the spleen with minimal liver uptake and lack of retention in the lungs in both normal volunteers and RA patients. There were no significant differences between both groups in granulocyte clearance from the lungs and their subsequent distribution in the spleen, bone marrow and liver. The results of this study demonstrate that the behaviour of granulocytes in RA patients is essentially unchanged from that of normal volunteers.

Single photon emission computed tomography (SPECT) with the tracer 99Tcm-hexamethylpropyleneamine oxime (HMPAO) provides images allowing semiquantitative estimation of regional cerebral blood flow (rCBF). Despite its widespread use there is little data on patterns of rCBF obtained using this tracer in normal elderly subjects, although other methods of measurement suggest a fall in cerebral blood flow with age. Furthermore, the detection of interhemispheric asymmetries on HMPAO SPECT is often used to identify areas of pathological abnormality yet there is little data on the prevalence of asymmetries in the normal elderly. An increased prevalence of asymmetries in the elderly may explain the difficulties recently reported in using functional imaging in the diagnosis of Alzheimer's dementia. Patterns of HMPAO uptake were compared in 10 young (mean age 24.9 years; range 21-34 years) and 10 elderly (mean age 74.1 years; range 70-76 years) normal subjects. Percentage interhemispheric asymmetry ratios were calculated and found to be greater in the elderly, particularly for the temporal cortex (young 0.87%, elderly 3.73%, P < 0.001). The proportion of injected HMPAO taken up by the head was 29% higher in the younger age group. Analysis of regional uptake revealed that this trend towards reduced uptake in the elderly was a global phenomenon affecting all brain regions. The increased interhemispheric asymmetries seen in the elderly imply that a higher threshold for interpreting asymmetries as abnormal must be used in the elderly, particularly for the temporal cortex.

Marfan syndrome is a heritable disorder of connective tissue in which the most prominent abnormalities occur in the ocular, cardiovascular and skeletal systems. Although cardiovascular complications are infrequent in patients under 20 years of age, whenever they do occur, they are the major cause of death. Here we report three cases in a Chinese family with clinical evidence of myocarditis associated with Marfan syndrome. The 99Tcm-hexamethylpropyleneamine oxime (HMPAO)-labelled white blood cell and 201Tl single photon emission computed tomographic heart scans show indications of an inflammatory process involving the myocardium. After comparison with the pathology results, the accuracy of these studies is seen to be 100%. We thus introduce these simple methods to evaluate myocardial viability in patients with Marfan syndrome.

Cerebral perfusion deficits detected by injection of 99Tcm-hexamethylpropyleneamine oxime (HMPAO) and single photon emission tomography is said to correlate well with clinical findings in divers with neurological decompression illness. We studied 12 divers. Six had residual cerebral signs (group 1) and six had no residual cerebral symptoms or signs (group 2). Perfusion deficits were as common in group 2 as in group 1. The site of the deficit did not correlate well with either the neurological findings at presentation or the residual clinical signs after treatment. The data suggest that claims that HMPAO scanning correlates with clinical findings and can be used for patients management were incorrect.

The effects of the choice of the reference region in determining the relative regional cerebral blood flow (rCBF) using 99Tcm-hexamethylpropylene amine oxime (HMPAO) single photon emission tomography (SPECT) have been studied in order to establish or exclude it as a cause of inconsistencies in these studies. Relative rCBF was estimated by normalizing the regional count densities to two reference regions, the cerebellum and the whole slice, in 35 patients with Alzheimer's disease (AD), 25 patients with chronic schizophrenia (SCH) and the same number of matched normal volunteers. The statistical significance of the differences in rCBF between patients and their matched normals varied in the two sets of rCBF data. Smaller differences were highly significant while some larger differences were of less significance with whole slice normalization. The results suggest that the choice of reference region is one of the causes resulting in discrepancies in the results from various centres. The need to use a standard reference region is indicated.

99Tcm-teboroxime is a new myocardial perfusion agent with a high first pass extraction and rapid myocardial washout. The usefulness of 99Tcm-teboroxime was evaluated for detection of myocardial ischaemia using a three-headed single photon emission tomography (SPECT) system which allows for rapid data acquisition. The subjects consisted of 14 patients, including seven with ischaemic heart disease, four with cardiomyopathy and three others. After the 99Tcm-teboroxime injection, dynamic data was collected every minute for 15 min with continuous rotation. High-quality SPECT images could be obtained by reconstructing the serial scans from 2 to 8 min. The sensitivity, specificity and accuracy of the 99Tcm-teboroxime study for the detection of the ischaemic region were not significantly different from those of the 201Tl study. Myocardial clearance was slow in the ischaemic lesion and in the myocardium of cardiomyopathy patients, while the coronary angiograms did not show any abnormality. These results therefore indicate that the rapid SPECT imaging and myocardial clearance of 99Tcm-teboroxime obtained with a three-headed SPECT system were useful for the detection of myocardial ischaemia.