Uptake of SPECT radiopharmaceuticals in neocortical brain cultures

The uptake, retention and uptake antagonism of 201Tl-DDC, 201Tl-Cl, 123I-IMP, 99mTc-HMPAO and 99mTc-O4- were compared in rat neocortex cultures. 201Tl-DDC and 123I-IMP revealed the highest uptake of radioactivity in the cultures. 99mTc-HMPAO and 123I-IMP showed the highest retention of radioactivity within the tissue in washout experiments. Blocking of bioelectric activity by tetrodotoxin did not significantly affect the uptake of the radiopharmaceuticals (RPHA). Inhibition of Na-K-ATPase by ouabain inhibited the uptake of 201Tl-Cl (77%) and 201Tl-DDC (27%). Imipramine showed a significantly stronger inhibitory effect on 123I-IMP uptake in comparison with the effect on other RPHA. 99mTc-O4- was not concentrated within the cultured tissue. Under the in vitro conditions used in this study, the various RPHA were characterised by distinct differences in their interaction with cortical brain tissue.     

Intra-arterial infusion of N-isopropyl-p[123I]iodoamphetamine for assessing effective blood supply to pulmonary and hepatic neoplasms

The biodistribution and pharmacokinetics of intra-arterially administered N-isopropyl-p[¹²³I] iodoamphetamine (¹²³I-IMP) were prospectively evaluated in 38 patients with histologically proven pulmonary or hepatic tumors. Intra-arterially infused¹²³I-IMP was distributed initially in peripheral tissues in which the blood supply was maintained. Its concentration in malignant neoplasms was demonstrated to be higher than in normal tissues. In pulmonary cancer, the tumor uptake of the administered dose without a tissue attenuation correction (% uptake) of¹²³I-IMP at 1–2 min after injection was 14.7 ± 5.7% (s.d.). The tumor to normal tissue ratio was 2.1 ± 0.7 in hepatocellular carcinoma and 1.4 ± 0.7 in metastatic tumors. The biodistribution of¹²³I-IMP was also compared to that of^99mTc-macroaggregated albumin (^99mTc-MAA) in 9 cases of hepatic cancer. The distribution of¹²³I-IMP resembled that of^99mTc-MAA in 5 cases and was different in 4 cases.¹²³I-IMP was more concentrated in the tumor than^99mTc-MAA. Intra-arterial infusion scintigraphy with¹²³I-IMP seems to provide information on effective blood supply to neoplasms which are targeted in interventional radiology.     

Technetium-99m diethyldithiocarbamate (DDC): Comparison with thallium-201 DDC as an agent for brain imaging

Technetium-99m diethyldithiocarbamate (^99mTc-DDC) was prepared by reduction of [^99mTc]pertechnetate with formamidine sulfinic acid in the presence of DDC at alkaline pH, both from extemporaneous solutions and in a kit formulation. The properties of ^99mTc-DDC were compared in vitro and in vivo with those of ²⁰¹Tl-DDC, an agent used for cerebral perfusion imaging (CPI). ^99mTc-DDC is a lipophilic complex but its oil/water partition coefficient is lower than that of ²⁰¹Tl-DDC. ^99mTc-DDC also shows greater binding to plasma proteins. Studies in rabbits show that ^99mTc-DDC enters the brain but is not retained to the same extent as ²⁰¹Tl-DDC. This lack of retention may be because ^99mTc-DDC does not decompose rapidly in lipid media as ²⁰¹Tl-DDC does. These results suggest that ^99mTc-DDC in its present formulation is not suitable for CPI with SPECT.     

“Luxury perfusion” with99mTc-HMPAO and123I-IMP SPECT imaging during the subacute phase of stroke

To compare the merits of¹²³I-isopropyl-iodoam-phetamine (¹²³I-IMP) and^99mTc-HMPAO in showing abnormal brain uptake distribution during cerebral ischemia, we studied ten patients during the subacute phase of their stroke, a period where metabolism and blood flow are frequently uncoupled. SPECT imaging was performed using both radiopharmaceuticals in the 10 patients from 48 h to 4 weeks after onset of symptoms. Two patients out of the 10 had similar defects with¹²³I-IMP and^99mTc-HMPAO SPECT, the location of the defects corresponding to the area of infarction observed on CT. Six patients had normal^99mTc-HMPAO SPECT and abnormal¹²³I-IMP SPECT with defects in the area of infarction shown by CT. The remaining 2 patients had hyperactive abnormalities on^99mTc-HMPAO in areas corresponding to defects on the¹²³I-IMP images. Two of the patients with SPECT mismatches were studied again more than 1 month after onset. On reexamination,^99mTc-HMPAO SPECT which was previously normal or hyperactive became hypoactive with a focal area of decreased activity corresponding to the defect on¹²³I-IMP. Crossed cerebellar diaschisis was found in 7 patients with^99mTc-HMPAO and was absent for both¹²³I-IMP and^99mTc-HMPAO in 3. We suggest that SPECT with⁹⁹mTc-HMPAO could show transient hyperemia not demonstrated by¹²³I-IMP whereas in some cases cerebral infarction would be more difficult to demonstrate with^99mTc-HMPAO than with¹²³I-IMP. SPECT with both tracers is recommended to follow the evolution of strokes in terms of regional cerebral blood flow and tissue metabolism.     

Myocardial uptake of thallium-201 diethyldithiocarbamate (201TI-DDC) in cultured heart cells and in humans

We assessed the feasibility of SPECT imaging with ²⁰¹Tl-diethyldithiocarbamate (²⁰¹Tl-DDC), a new cerebral blood flow tracer with little redistribution, expecting to observe less extensive redistribution than with ²⁰¹Tl-chloride. Myocardial sections were obtained in three patients presenting with documented coronary artery disease and injected at peak exercise with 100 MBq ²⁰¹Tl-DDC. In two patients there was a clear redistribution phenomenon at four h after injection. In cultured myocardial cells of newborn rats, the uptake and washout of ²⁰¹Tl-chloride and ²⁰¹Tl-DDC were compared. The ²⁰¹Tl-DDC uptake was lower than ²⁰¹Tl-chloride (transmembrane gradients were respectively 89±10 and 4.1±0.2, mean±sem, n=14, P<0.001). After 2 h washout in a Tl free medium, the retention of ²⁰¹Tl-chloride in the cells was 4% vs 19% for ²⁰¹Tl-DDC. It is concluded that although myocardial imaging is feasible with ²⁰¹Tl-DDC, this agent redistributes significantly with time.     

99mTc-NC100668, a new tracer for imaging venous thromboemboli: pre-clinical biodistribution and incorporation into plasma clots in vivo and in vitro

Purpose

^99mTc-NC100668 is a new radiotracer being developed to aid the diagnosis of thromboembolism. The structure of NC100668 is similar to a region of human α₂-antiplasmin, which is a substrate for factor XIIIa (FXIIIa). The purpose of this study was to confirm the uptake of ^99mTc-NC100668 into forming plasma clot and to establish the biodistribution of ^99mTc-NC100668 in Wistar rats.

Methods

The in vitro plasma clot uptake of ^99mTc-NC100668 and other compounds with known affinities to FXIIIa was measured using a plasma clot assay. The biodistribution and blood clot uptake of radioactivity of ^99mTc-NC100668 in normal Wistar rats and those bearing experimentally induced deep vein thrombi were investigated.

Results

The in vitro uptake of ^99mTc-NC100668 was greater than that for [¹⁴C]dansyl cadaverine, a known substrate of FXIIIa in the plasma clot assay. The biodistribution of ^99mTc-NC100668 in male and female Wistar rats up to 24 h p.i. showed that radioactivity was rapidly excreted, predominantly into the urine, with very little background tissue retention. In vivo the uptake and retention of ^99mTc-NC100668 into the blood clot was greater than could be accounted for by non-specific accumulation of the radiotracer within the blood clot.

Conclusion

^99mTc-NC100668 was retained by plasma clots in vitro and blood clots in vivo. No significant tissue retention which could interfere with the ability to image thrombi in vivo was observed. This evidence suggests that ^99mTc-NC100668 might be useful in the detection of thromboembolism.     

Report of a nationwide survey on actual administered radioactivities of radiopharmaceuticals for diagnostic reference levels in Japan

Objective

The optimization of medical exposure is one of the major issues regarding radiation protection in the world, and The International Committee of Radiological Protection and the International Atomic Energy Agency recommend establishing diagnostic reference levels (DRLs) as tools for dose optimization. Therefore, the development of DRLs based on the latest survey has been required for nuclear medicine-related societies and organizations. This prompted us to conduct a nationwide survey on the actual administered radioactivity to adults for the purpose of developing DRLs in nuclear medicine.

Methods

A nationwide survey was conducted from November 25, 2014 to January 16, 2015. The questionnaire was sent to all of the 1249 nuclear medicine facilities in Japan, and the responses were collected on a website using an answered form.

Results

Responses were obtained from 516 facilities, for a response rate of 41 %. 75th percentile of ^99mTc-MDP and ^99mTc-HMDP: bone scintigraphy, ^99mTc-HM-PAO, ^99mTc-ECD and ¹²³I-IMP: cerebral blood flow scintigraphy, ^99mTc-Tetrofosmin, ^99mTc-MIBI and ²⁰¹Tl-Cl; myocardial perfusion scintigraphy and ¹⁸F-FDG: oncology PET (in-house-produced or delivery) in representative diagnostic nuclear medicine scans were 932, 937, 763, 775, 200, 831, 818, 180, 235 and 252, respectively. More than 90 % of the facilities were within the range of 50 % from the median of these survey results in representative diagnostic nuclear medicine facilities in Japan. Responses of the administered radioactivities recommended by the package insert, texts and guidelines such as 740 MBq (^99mTc-MDP and ^99mTc-HMDP: bone scintigraphy), 740 MBq (^99mTc-ECD and ^99mTc-HM-PAO: cerebral blood flow scintigraphy) and 740 MBq (^99mTc-Tetrofosmin and ^99mTc-MIBI: myocardial perfusion scintigraphy), etc. were numerous. The administered activity of many radiopharmaceuticals of bone scintigraphy (^99mTc-MDP and ^99mTc-HMDP), cerebral blood flow scintigraphy (^99mTc-HM-PAO) and myocardial perfusion scintigraphy (^99mTc-Tetrofosmin and ^99mTc-MIBI), etc. were within the range of the EU DRLs and almost none of the administered radioactivity in Japan exceeded the upper limit of SNMMI standard administered radioactivity.

Conclusions

This survey indicated that the administered radioactivity in diagnostic nuclear medicine in Japan had been in the convergence zone and nuclear medicine facilities in Japan show a strong tendency to adhere to the texts and guidelines. Furthermore, the administered radioactivities in Japan were within the range of variation of the EU and the SNMMI administered radioactivities.

     

Paradoxical technetium-thallium subtraction scan in a case of parathyroid adenoma

A technetium-thallium (^99mTcO₄-²⁰¹Tl) subtraction scan was performed in a patient with clinical and biological evidence of hyperparathyroidism. The ²⁰¹Tl image indicated a normal thyroid gland. The ^99mTcO₄ image revealed a left inferior thyroidal extension with an intense and transient focus corresponding to an ultrasonographic nodule. The transient character of the focus was not explicable in terms of vascular kinetics. A supplementary scintigram using ¹²³I confirmed the presence of an inferior extension of the thyroid, but no increased uptake was found. A nodule weighing 250 mg containing a parathyroid adenoma surrounded by normal thyroidal tissue was excised at the focus site. Biological serum levels returned to normal after the operation. It is concluded that the analysis of ^99mTcO₄ dynamic data could improve the accuracy of parathyroid subtraction scintigraphy.     

Effects of cigarette smoking on iodine 123 N-isopropyl-p-iodoamphetamine clearance from the lung

Iodine 123 N-isopropyl p-iodoamphetamine (¹²³I-IMP), originally developed as a brain scanning agent, is also taken up by the lung. To evaluate the effects of cigarette smoking on the kinetics of IMP in the lung, we studied ¹²³I-IMP clearance from the lung in 18 volunteers (8 non-smokers and 10 smokers). After the injection of 111 MBq of ¹²³I-IMP into the medial cubital vein, the time-activity curve for 60 min and the regional activity using 1 frame per minute and a 64 × 64 matrix were obtained. The ¹²³I-IMP clearance curve was described as follows: C (t) = A ₁e^–k ₁ t+ A ₂e^–k ₂ t (A1, A ₂: intercepts, and k ₁, k ₂: slopes of the exponential components). ¹²³I-IMP clearance was delayed in smokers, and k ₂ was smaller in smokers. Also, a correlation between k ₁, k ₂, and the number of cigarettes smoked per day was found (r = –0.65, r = –0.74, respectively, P<0.01). In conclusion, this study suggests that the delayed clearance and retention of ¹²³I-IMP in the lung indicate lung metabolic disorders due to cigarette smoking.Offprint requests to: K. Kato     

Prolonged lung retention of 123I-IMP in pulmonary disease

The accumulation of venously injected ¹²³I-IMP in the lung was studied. Between 30 and 50 min after the injection of the 1.5 mCi ¹²³I-IMP, the concentration of ¹²³I-IMP in the broncho-alveolar lavage fluid were much higher than in the blood. It was considered that ¹²³I-IMP was transported into the alveolar spaces and was absorbed by the alveolar cells. The half time (T _1/2) of the ¹²³I-IMP release from the lung between 10 and 25 min immediately after the injection was calculated. In normal subjects the T _1/2 ranged between 25 and 44 min and was prolonged in subjects with pulmonary fibrosis, sarcoidosis, and allergic alveolitis. It was considered that the retention of ¹²³I-IMP was related not only to the endothelial cells, but also to the alveolar cells. It was considered that the analysis of the lung release of ¹²³I-IMP forms a new lung dysfunction index.     

Targeting murine heart and brain: visualisation conditions for multi-pinhole SPECT with <Superscript>99m</Superscript>Tc- and <Superscript>123</Superscript>I-labelled probes

Purpose  The study serves to optimise conditions for multi-pinhole SPECT small animal imaging of ¹²³I- and ^99mTc-labelled radiopharmaceuticals with different distributions in murine heart and brain and to investigate detection and dose range thresholds for verification of differences in tracer uptake. Methods  A Triad 88/Trionix system with three 6-pinhole collimators was used for investigation of dose requirements for imaging of the dopamine D₂ receptor ligand [¹²³I]IBZM and the cerebral perfusion tracer [^99mTc]HMPAO (1.2–0.4 MBq/g body weight) in healthy mice. The fatty acid [¹²³I]IPPA (0.94 ± 0.05 MBq/g body weight) and the perfusion tracer [^99mTc]sestamibi (3.8 ± 0.45 MBq/g body weight) were applied to cardiomyopathic mice overexpressing the prostaglandin EP₃ receptor. Results  In vivo imaging and in vitro data revealed 45 kBq total cerebral uptake and 201 kBq cardiac uptake as thresholds for visualisation of striatal [¹²³I]IBZM and of cardiac [^99mTc]sestamibi using 100 and 150 s acquisition time, respectively. Alterations of maximal cerebral uptake of [¹²³I]IBZM by >20% (116 kBq) were verified with the prerequisite of 50% striatal of total uptake. The labelling with [^99mTc]sestamibi revealed a 30% lower uptake in cardiomyopathic hearts compared to wild types. [¹²³I]IPPA uptake could be visualised at activity doses of 0.8 MBq/g body weight. Conclusion  Multi-pinhole SPECT enables detection of alterations of the cerebral uptake of ¹²³I- and ^99mTc-labelled tracers in an appropriate dose range in murine models targeting physiological processes in brain and heart. The thresholds of detection for differences in the tracer uptake determined under the conditions of our experiments well reflect distinctions in molar activity and uptake characteristics of the tracers. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Comparison of uptake of99mTc-MIBI,99mTc-tetrofosmin and99mTc-012 into human breast cancer cell lines

Technetium-99m hexakis-2-methoxyisobutylisonitrile (MIBI),^99mTc-tetrofosmin and^99mTc-Q12 were all introduced for myocardial imaging but found additional applications as they are taken up by different tumours, enabling imaging of these lesions in patients. The aim of this study was to compare the uptake characteristics of these compounds in vitro in the human adenocarcinoma breast cell lines MCF-7 and ZR-75. It was shown that^99mTc-MIBI had the highest cellular uptake (15.9%±0.5% dose/mg protein after 60 min in MCF-7, and 14.2%±0.4% dose/mg protein in ZR-75), followed by^99mTc-tetrofosmin (6.8%±0.6% dose/mg protein in MCF-7, and 8.2%±0.2% dose/mg protein in ZR-75) and^99mTc-Q12 (3,2%±0. I% dose/mg protein in MCF-7, and 3.5%±0.3% dose/mg protein in ZR-75 cells). For all three compounds tenfold differences in specific activity did not influence total cell-associated radioactivity. Uptake of^99mTc-MIBI and^99mTc-tetrofosmin was obviously lower at 4° C than at 37° C, whereas^99mTc-Q12 uptake showed only slight temperature dependence. When uptake was compared in cells grown to different cell densities (1 mg/ml cellular protein versus 0.3 mg/ml), no differences in uptake were detected when uptake was corrected for the amount of cellular protein present in the dishes. Furthermore, for all compounds it was shown that cellular radioactivity decreased rapidly after washing. Apart from the differences in cellular uptake of the three compounds after 60 min, no differences in residual cellular radioactivity after washing were found between the different compounds when expressed as a percentage of their 60-min uptake, suggesting that the efflux process of the radiolabelled compounds was similar. The differences in cell-associated activity after 60 min were thus presumably caused by differences in uptake. It was concluded that of the Tc-labelled compounds tested,^99mTc-MIBI had the highest cellular retention in both human breast tumour cell lines. However, for imaging in vivo not only radioactivity in the target organ is important, but also the ratio of radioactivity in the target versus that in the background. Therefore, further studies in vivo need to be performed to investigate which compound is the optimal imaging agent     

Extensive soft-tissue involvement of dermatomyositis detected by whole-body scintigraphy with99mTc-MDP and201Tl-chloride

The authors present a case of extensive soft-tissue radioactivity visualized on both^99mTc-MDP and²⁰¹Tl-chloride scintigrams in a patient with dermatomyositis and colon cancer. Incidentally, diffuse and intense uptake of^99mTc-MDP was observed in the shoulder girdles, anterior chest wall, psoas muscles, both proximal thighs and right lower limb, corresponding to the sites of symptomatic muscles, even though skin lesions were limited and no calcification was detected on radiographs. Moreover,²⁰¹Tl-chloride was also intensely accumulated in nearly the same sites as the symptomatic muscles as shown on the^99mTc-MDP bone scintigrams. Whole-body scintigraphy with^99mTc-MDP and²⁰¹Tl-chloride is a useful tool to detect occult muscle lesions with dystrophic calcification and hyperemia in dermatomyositis.     

Altered kinetics of 123I-IMP in irradiated rabbit lungs.

Radiation-induced alteration of intrapulmonary kinetics of 123I-IMP was investigated in 11 rabbits receiving a 50 Gy dose of radiation to one lung. In all 13 examinations of these rabbits, 3-17 weeks following radiation, the delayed images of 123I-IMP lung scintigrams showed abnormal accumulation in the irradiated lungs. The time-activity curves of the irradiated lung following injection of 123I-IMP had shallower downslopes of both the initial fast phase and the following slow phase than those of the non-irradiated lung. Finally the radioactivity of the irradiated lung exceeded that of the normal lung. The altered intrapulmonary kinetics of 123I-IMP in the irradiated lung was clearly confirmed. 99Tcm-MAA lung perfusion scintigrams showed reduced uptake in the irradiated lungs; the uptake decreased with time following radiation. Pulmonary arterial perfusion was considered to influence the distribution and kinetics of 123I-IMP, however, those of 123I-IMP did not reflect only the pulmonary arterial perfusion observed by 99Tcm-MAA scintigrams. Chest radiography and histological studies revealed a relatively slight change or injury of the irradiated lung in these rabbits. These results indicate that this agent could be useful in detecting and assessing early lung injury induced by radiation, and will give us pathological information in addition to lung perfusion in the peripheral area where the large 99Tcm-MAA molecule cannot reach.     

Extraction and retention of technetium-99m Q12, technetium-99m sestamibi, and thallium-201 in isolated rat heart during coronary acidemia

Technetium-99m Q12 and ^99mTc-sestamibi are cationic lipophilic myocardial perfusion imaging tracers. Because myocardium in areas of ischemia becomes acidotic, experiments were designed to differentiate the effects of myocardial perfusate pH on radiotracer extraction and retention independent of substrate availability. We hypothesized that ^99mTc-Q12 and ^99mTc-sestamibi single-pass uptake and retention would be unaffected by a modest reduction in coronary perfusate pH. Isolated rat hearts were perfused at constant flow with Krebs-Henseleit buffer enriched with bovine red blood cells (20%). The indicator dilution method was used to measure the maximum extraction (E _max) and net extraction (E _net) of thallium-201 and ^99mTc-Q12 (n = 8) or ²⁰¹Tl and ^99mTc sestamibi (n = 7) during baseline perfusion (pH = 7.4), during acidemic (pH = 6.7) perfusion, and during a restitution period with normal perfusate (pH = 7.4). ²⁰¹Tl E _max (0.71±0.03) was greater than either ^99mTc-Q12 or ^99mTc-sestamibi E _max (0.27±0.02 and 0.26±0.01 respectively, P<0.0001). Acidemia significantly reduced ²⁰¹Tl E _max (0.65±0.03, P<0.02) but not ^99mTc-Q12 or ^99mTc-sestamibi E _max (0.25±0.02 and 0.24±0.02 respectively). During control perfusion E _net of ²⁰¹Tl was greater than that of ^99mTc-Q12 at 3 and 5 min and greater than that of ^99mTc-sestamibi at 3 min. ^99mTc-Q12 E _net was less than ^99mTc-sestamibi E _net at 3, 5, and 10 min. Acidemia decreased ²⁰¹Tl and ^99mTc-sestamibi E _net at 3, 5, and 10 min but had no effect on ^99mTc-Q12 E _net. It is concluded that E _max of ^99mTc-Q12 is less than that of ²⁰¹Tl but is not different from that of ^99mTc-sestamibi. E _net of ^99mTc-Q12 is less than that of ^99mTc-sestamibi. Received 20 May and in revised form 4 August 1997     

Assessment of myocardial perfusion and viability with technetium-99m methoxyisobutylisonitrile and thallium-201 rest redistribution in chronic coronary artery disease

We compare thallium-201 rest redistribution and fluorine-18 fluorodeoxyglucose ([¹⁸F]FDG) for the assessment of myocardial viability within technetium-99m methoxyisobutylisonitrile (MIBI) perfusion defects in 27 patients with chronic stable coronary artery disease. The following studies were performed: (1) stress^99mTc-MIBI, (2) rest^99mTc-MIBI, (3)²⁰¹T1 rest-redistribution single-photon emission tomography, (4) [¹⁸F]FDG positron emission tomography. The left ventricle was devided into 11 segments on matched tomographic images. The segment with the highest activity at stress was taken as the reference (activity=100%). Perfusion defects at^99mTc-MIBI rest were classified as severe (activity<50%), moderate (activity 50%–60%) or mild (activity 60%–85%). Uptakes of [¹⁸F]FDG and rest-redistributed²⁰¹Tl were recognized as significant if they exceeded 50% of that in the reference segment. Among the 33 segments with severe^99mTc-MIBI rest perfusion defects, 21 had significant [¹⁸F]FDG and 10 significant rest-redistributed²⁰¹Tl uptake. As regards the 37 segments with moderate defects, [¹⁸F]FDG was present in 29 and²⁰¹Tl in 31, while of the 134 segments with mild defects, 128 showed [¹⁸F]FDG uptake, and 131,²⁰¹Tl uptake. In conclusion, there is an inverse relationship between the severity of^99mTc-MIBI perfusion defects and the uptake of rest-redistributed²⁰¹Tl and [¹⁸F]FDG. Both tracers are adequate markers of viability in mild and moderate defects; in severe defects²⁰¹Tl might underestimate the presence of viability as assessed by [¹⁸F]FDG.     

Tumour-like thallium-201 accumulation in brain infarcts,an unexpected finding on single-photon emission tomography

Thallium-201 brain single-photon emission tomography (²⁰¹Tl-SPET) is widely used to detect viable tumour tissue with increased metabolic activity. When reperfusion takes place early in cerebrovascular lesions of embolic origin, the presence of tissue areas with increased regional blood flow and preserved metabolic activity can also be assumed. In the present study our purpose was to investigate whether or not foci of ²⁰¹Tl accumulation occur in reperfused areas with sustained morphological integrity indicated by computed tomography (CT) scans not showing hypodensity in the acute or subacute period.In 16 stroke patients with possible cortical embolic infarction, dual ²⁰¹Tl and technetium-99m hexamethylpropylene amine oxime (^99mTc-HMPAO) SPET was performed in both the acute and the subacute period. ^99mTc-HMPAO SPET was performed to detect reperfusion. Follow-up CT scans from the same period were also available. In five cases ^99mTc-HMPAO SPET ruled out reperfusion and ²⁰¹Tl SPET was also negative. In four cases ^99mTc-HMPAO studies indicated reperfusion early in the acute phase (24–72 h), and comparative CT, without showing hypodensity in the acute or subacute period, also favoured the possibility of sustained metabolic activity. In these cases ²⁰¹Tl SPET was negative in both the acute and the subacute period. In seven cases CT already showed necrosis in ^99mTc-HMPAO hypoperfused areas in the acute period, with negative results on corresponding ²⁰¹Tl SPET. Later reperfusion occurred in the subacute period (8–14 days) as indicated by ^99mTc-HMPAO SPET, at which time an unexpected focal accumulation of ²⁰¹Tl was detected. We cannot give any explanation for the findings, but further studies might clarify the matter and improve our knowledge of the precise mechanism of ²⁰¹Tl uptake under different conditions. Until then the phenomenon should be borne in mind as a possible pitfall when assessing tissue viability.     

Non-matched images with 123I-IMP and 99mTc-bicisate single-photon emission tomography in the demonstration of focal hyperaemia during the subacute phase of an ischaemic stroke

Focal hyperaemia is a fairly common phenomenon in the subacute phase of an ischaemic stroke. This has rarely been reported with iodine-123 iodoamphetamine (IMP) and has never been identified using technetium-99m bicisate (^99mTc-ECD). In this report, we present the case of a patient suffering from a left cerebral posterior stroke. ¹²³I-IMP single-photon emission tomography (SPET) images showed a large area of significantly increased IMP activity located in the left occipital region whereas ^99mTc-bicisate SPET displayed hypoactivity in the same area. Correspondence to: F. Tamgac     

The value of gallium-67 and thallium-201 whole-body and single-photon emission tomography images in dialysis-related β2-microglobulin amyloid

The aim of this study was to investigate the value of gallium-67 and thallium-201 whole-body and single-photon emission tomography (SPET) images in long-term dialysis patients in whom dialysis-related β₂-microglobulin amyloid (β₂-MA) was clinically suspected. Twenty-three patients who had received dialysis for at least 10 years were included in the study. A technetium-99m methylene diphosphonate (MDP) whole-body scan was performed in all of the patients. If there was any MDP accumulation in the articular and/or peri-articular region, ⁶⁷Ga and ²⁰¹Tl whole-body and SPET images were then acquired. If any ⁶⁷Ga and/or ²⁰¹Tl uptake was observed, a CT-guided biopsy was done. In those patients who had articular and/or peri-articular uptake of ^99mTc MDP, ⁶⁷Ga and/or ²⁰¹Tl and who were pathologically proven to have β₂-MA, ^99mTc MDP, ⁶⁷Ga and ²⁰¹Tl whole-body scans and SPET were carried out again, both 3 months and 1 year after initiation of treatment. This served to evaluate the therapeutic effect and allowed comparison with the clinical findings. Of the 23 patients, eight had abnormal ^99mTc MDP uptake. Among these eight, six had intense ^99mTc MDP, ⁶⁷Ga and ²⁰¹Tl uptake in the articular and peri-articular regions before medication. Three months after the start of treatment, there were very marked decreases in uptake on both the ⁶⁷Ga and ²⁰¹Tl scans but less obvious changes in uptake of ^99mTc-MDP. In comparison with the other clinical manifestations such as limitation in range of motion, the more the painful disability improved, the less was the uptake on both ⁶⁷Ga and ²⁰¹Tl scans. There were virtually no differences in uptake pattern between the three scans of each radiopharmaceutical obtained for each patient in both 3 months and 1 year after initial of treatment. It is concluded that ^99mTc-MDP whole-body bone scan can both detect active and pre-existing inactive deposits of β₂-MA. ⁶⁷Ga and ²⁰¹Tl scans are helpful to differentiate active from inactive deposits of β₂-MA and to evaluate the therapeutic effect on these patients. SPET images are usually needed to distinguish articular and peri-articular lesions from bone lesions. Received 19 May and in revised form 9 August 1999     

123I-IMP accumulation in the lung with bronchial asthma--early uptake and delayed washout

123I-IMP is taken up by the pulmonary capillary endothelial cells during the first pass through the lung, and is slowly released from them. To look up the factors which influence on the prolonged 123I-IMP retention in the diseased lung, we examined the correlation between the 123I-IMP uptake during the first pass and the 123I-IMP retention. Patients with bronchial asthma had no abnormal finding in the chest X-ray photograph. However 123I-IMP release from their lungs was delayed. Some patients show a tendency that 123I-IMP uptake during the first pass was uneven, which suggested the change in amine uptake function of endothelial cells. However their correlation coefficients between the uptake during the first pass and the prolonged retention were very small. It was considered that the prolonged 123I-IMP retention in the diseased lung was not explained only by the change in uptake function of pulmonary capillary endothelial cell.