Technetium-99m-tetrofosmin uptake in brain tumors by SPECT: comparison with thallium-201 imaging.

UNLABELLED: Thallium-201 is clinically used for the assessment of primary and recurrent brain tumors. The biologic properties of 201Tl that allow it to accumulate within the tumor cells render 201Tl useful in evaluating tumor malignancy, but its physical characteristics and nonroutine availability limits its use in some institutions, as compared to 99mTc-labeled compounds. The aim of this study was to assess the feasibility of using 99mTc-tetrofosmin for imaging brain tumors and to compare its uptake with that of 201Tl. METHODS: Twenty-six patients with 27 intracranial masses were studied with SPECT. In the first group of seven patients (Group A), the timing for optimal acquisition of the 99mTc-tetrofosmin scan was assessed. In the second group of 19 patients (Group B), two sequential 201Tl (74-148 MBq intravenous) and 99mTc-tetrofosmin (740-925 MBq intravenous) studies were performed 20 min after tracer injection and compared. RESULTS: In Group A, no significant difference in the tumor-to-background (T/B) ratio among the 20-, 40- and 120-min postinjection studies was observed. In Group B, the quality of reconstructed images with 99mTc-tetrofosmin, judged visually, was superior to that of 201Tl in 47% of all studies and was comparable in the remaining 53%. A significant relationship between 201Tl and 99mTc-tetrofosmin T/B ratio (r = 0.75, p < 0.01) was found. The T/B ratio of 99mTc-tetrofosmin was significantly higher than that of 201Tl (23.3 +/- 21.5 compared to 6.1 +/- 2.9, p < 0.005). CONCLUSION: Technetium-99m-tetrofosmin is a suitable radiotracer for the imaging of intracranial lesions with SPECT. Moreover, a better definition of tumor margins and a higher contrast between neoplastic and normal brain tissue can be achieved.

Reduced cortical distribution volume of iodine-123 iomazenil in Alzheimer's disease as a measure of loss of synapses.

Iodine-123 labelled iomazenil (IMZ) is a specific tracer for the GABAA receptor, the dominant inhibitory synapse of the brain. The cerebral distribution volume (Vd) of IMZ may be taken as a quantitative measure of these synapses in Alzheimer's disease (AD), where synaptic loss tends indiscriminately to affect all cortical neurons, albeit more so in some areas than in others. In this pilot study we measured Vd in six patients with probable AD and in five age-matched controls using a brain-dedicated single-photon emission tomography scanner allowing all cortical levels to be sampled simultaneously. Reduced values were found in all regions except in the occipital (visual) cortex. In particular, temporal and parietal cortex Vd was significantly (P<0.02) reduced: temporal Vd averaged 69 ml/ml in normals and 51 ml/ml in AD, and parietal Vd averaged 71 ml/ml in normals and 48 ml/ml in AD. These results accord well with emission tomographic studies of blood flow or labelled glucose. This supports the idea that while only measuring a subpopulation of synapses, the IMZ method reflects synaptic loss and hence functional loss in AD. The method constitutes an in vivo version of synaptic quantitation that in histopathological studies has been shown to correlate closely with the mental deterioration in AD.

[Tetrofosmin: a new compound labeled with 99mTc for the study of myocardial perfusion. Correlations with coronary anatomy in patients with suspected ischemic cardiopathy]. / La tetrofosmina: un nuovo composto marcato con 99mTc per lo studio della perfusione miocardica. Correlazioni con l'anatomia coronarica nei pazienti con sospetta cardiopatia ischemica.

The aim of this study was to investigate the accuracy of quantitative one-day exercise-rest 99mTc tetrofosmin tomography in the identification of patients with suspected coronary artery disease (CAD) and in the detection of single stenosed coronary vessels. Sixty-one patients with suspected CAD and submitted to coronary angiography were examined. All patients were given 2 i.v. injections of 99mTc tetrofosmin, one at peak exercise (370 MBq) and the other (1110 MBq) at rest 3 hours after exercise (images 15-30 min after injection for both studies). All patients with CAD (> or = 50% luminal stenosis) (n = 50) had abnormal 99mTc tetrofosmin tomogram (100% sensitivity). Only one patient without CAD had abnormal 99mTc tetrofosmin tomogram (91% specificity). Overall sensitivity, specificity, and diagnostic accuracy in the detection of single stenosed vessels were 77%, 93% and 85%, respectively. No significant differences among single vascular areas were observed. Sensitivity and diagnostic accuracy in the identification of single stenosed coronary vessels were significantly higher (p < 0.05) in the patients with single-vessel disease (n = 21) than in those with multivessel disease (n = 29). Sensitivity, specificity and diagnostic accuracy in detecting single diseased vessels were similar in the patients without (n = 26) and in those with previous myocardial infarction (n = 35). The results of this study demonstrate that quantitative one-day exercise-rest 99mTc tetrofosmin SPECT imaging is a suitable and accurate technique to identify patients with suspected CAD and to detect single stenosed coronary vessels.

Evaluation of brain perfusion with high resolution single photon emission tomography in the diagnosis of brain death.

Nuclear Medicine studies performed with tomographic acquisition and tracers such as Technetium-99m hexamethyl-propyleneamine oxime (99mTc-HMPAO) are able to assess cerebral blood flow. A case is reported of a patient with a large intracranial tumor, of possible pituitary origin, with a clinical and electroencephalographic suspicion of brain death. The patient had endocrinous-metabolic impairments for a history of impotence, since 18 months, and diabetes insipidus with a urine output of 350 ml/hr in the first 24 hours from the clinical suspicion of brain death. Due to the endocrinous-metabolic impairments, according to Italian law, it was necessary to confirm the diagnosis of brain death by performing a study able to assess cerebral blood flow. A single Photon Emission Tomography (SPET) scan was performed after the intravenous administration of 99mTc-HMPAO using a high resolution, brain dedicated device. No tracer uptake was evident in cerebral, cerebellar and brain stem structures. The cerebral blood flow study by SPET confirmed the diagnosis of brain death and made the organ transplant possible in a short period of time. High resolution SPET studies are useful to confirm the diagnosis of brain death when there are factors that can influence clinical and electroencephalographic signs, reducing time to authorise the organ explant.