A quantitative approach to technetium-99m hexamethylpropylene amine oxime

Asymmetries of benzodiazepine receptor binding potential in the inferior medial temporal lobe and cerebellum detected with 123I-iomazenil SPECT in comparison with 99mTc-HMPAO SPECT in patients with partial epilepsy

We examined the relation between regional 123I-iomazenil (IMZ) parameters and cerebral blood flow (CBF) to evaluate the difference between the quantitative parameters of IMZ and the CBF in detecting epileptic abnormality. Seventeen patients with unilateral partial epilepsy were subjected to 99mTc-hexamethylpropylene amine oxime (HMPAO) SPECT, and early and delayed IMZ SPECT. Then we quantitatively obtained the blood-to-brain transfer constants (K1) and binding potentials (BP) for nine regions of interest, and the regional CBF was also by using the simple angiographic method. From our data, significant asymmetries of BP in the inferior medial temporal lobe and cerebellum were shown and may be related to a remote effect such as crossed cerebellar diaschisis. In conclusion, the asymmetry of BP with iomazenil SPECT was demonstrated in patients with unilateral epilepsy that was not detectable by HMPAO SPECT.

Noninvasive quantitative measurements of regional cerebral blood flow using technetium-99m-L,L-ECD SPECT activated with acetazolamide: quantification analysis by equal-volume-split 99mTc-ECD consecutive SPECT method

Resting- and acetazolamide (Acz)-activated-regional cerebral blood flow (rCBF) measurements were performed by consecutive single-photon emission computed tomography (SPECT) studies before and after Acz administration using equal-volume-split technetium-99m-L,L-ethyl cysteinate dimer. Quantitative rCBF images were converted from qualitative axial SPECT images by the application of Patlak plot graphical analysis with radionuclide angiography and Lassen's linearization correction. Total time span required for this study was 53 minutes. The unaffected side of 37 studies with unilateral vascular lesions and 45 studies without apparent vascular lesions showed 132 +/- 17% and 140 +/- 15% increase of mean CBF (mCBF), respectively, under Acz administration. Comparing these values, the Acz-activated rCBF increases of less-affected and affected hemispheres of 23 studies with bilateral vascular lesions (116 +/- 13% and 113 +/- 12%, respectively) was lower with high statistical significance (P < 0.001). For the other 20 cases, physiologic saline was administered instead of Acz. This group showed no changes in mCBF under placebo administration (after placebo/baseline; 100 +/- 6%). Acetazolamide-activated rCBF increase was recognized clearly and easily using quantitative images. This noninvasive method is easy to perform and may be helpful to detect regional abnormalities of hemodynamic reserve in cerebrovascular diseases.

Effect of enalapril maleate on cerebral blood flow in patients with chronic heart failure

The effect of enalapril on cerebral blood flow (CBF) was studied in 11 patients with chronic heart failure (NYHA II or III, dilated cardiomyopathy in 6 and old myocardial infarction in 5). CBF was evaluated by analyzing the Patlak-Plot curve obtained from radionuclide angiography with technetium-99m hexamethylpropylene amine oxime (99mTC-HM-PAO). Cardiac index (CI) and stroke volume (SV) were simultaneously measured by impedance cardiography. These measurements were performed before and at four weeks after daily administration of 5 mg enalapril. The stroke volume, cardiac index, and heart rate were not significantly changed after four weeks of enalapril administration. However, CBF was increased by 6.5% from 36.72 +/- 4.66 to 39.13 +/- 5.65 mL/100g/min (P < 0.05). These results suggest that enalapril increased cerebral blood flow, which was not related to increased cardiac output in congestive heart failure. Patlak-Plot analysis of radionuclide angiography using 99mTC-HM-PAO may be available for quantitative assessment of brain perfusion.

Opsoclonus-myoclonus syndrome with abnormal single photon emission computed tomography imaging

The single photon emission computed tomography (SPECT) findings in 2 patients with opsoclonus-myoclonus syndrome (OMS) who had similar symptoms in the acute stage of the disease are described. In 1 patient with encephalitis, SPECT showed increased blood flow in most of the cerebellum; the highest accumulation of the radiotracer was found in the cerebellar vermis and neighboring structures. These changes disappeared with clinical improvement. In the other patient with chronic OMS, SPECT demonstrated hypoperfusion in most of the cerebellum. Our results suggest that the cerebellum, particularly its middle portion, is involved in the generation of OMS. SPECt is a useful method that enables us to detect in vivo functional impairment in patients with OMS.

Quantitative regional cerebral flow measured by Tc-99M HMPAO SPECT in mood disorder

Depressed (n = 14) and remitted (n = 9) patients with mood disorder, patients with depressive disorder not otherwise specified (NOS; n = 10) and normal subjects (n = 8) underwent non-invasive and quantitative measurement of cerebral blood flow using HMPAO and SPECT in a resting state. The mean and regional cerebral blood flow (CBF) in twelve ROIs were compared among the four groups and correlations between CBF and the depressive symptoms were studies. The CBF was computed using graphical analysis on the SPECT console after a bolus injection of Tc-99m HMPAO and radionuclide angiography. The depressed group had significantly lower mCBF in the bilateral hemisphere and rCBF in all except one of the ROIs than the NOS and normal group. Significant negative correlations were found between the Hamilton scale for depression and rCBF in the bilateral lower frontal cortex after correcting for age in the mood disorder. Parallel analysis using both the quantitative and semiquantitative methods revealed that the former provided more global reduction of CBF in mood disorder. These results indicate that mean and regional CBF measured by this non-invasive method contributes to the objective evaluation of depressive symptoms. Negative correlations between HRSD and rCBF in the frontal regions indicate that frontal hypoactivity is closely related to depressive symptoms.

Simultaneous observation of regional cerebral blood flow and event-related potential during performance of an auditory task

Reduced amplitude of the P300 component has been reported consistently in patients with neurological and psychiatric disorders. It is unclear, however, how such patients' cognitive dysfunction is related to their P300 abnormality. Further basic knowledge regarding neural substrates for P300 generation is required for gaining an understanding of the pathological significance of the P300 amplitude reduction. To determine the brain structures involved in P300 generation, we observed the event-related potential and the regional cerebral blood flow (rCBF) in 10 normal subjects performing an oddball discrimination of pure tones. The rCBF value was assessed quantitatively with the aid of single photon emission computed tomography using technetium-99m hexamethylpropylene amine oxime. During the task performance, significant activation was observed in the posterior superior temporal and inferior parietal regions of the right hemisphere. In addition, positive correlation of the task-related increase in rCBF with the simultaneously recorded P300 amplitude was observed in the right but not the left posterior superior temporal region. These findings indicate that activation of the right non-verbal auditory area might modulate P300 generation during pure-tone discrimination.

Interictal cerebral and cerebellar blood flow in temporal lobe epilepsy as measured by a noninvasive technique using Tc-99m HMPAO

The usefulness of noninvasive regional cerebral blood flow measurements using Tc-99m hexamethylpropylene amine oxime (HMPAO) was evaluated in 45 patients with interictal temporal lobe epilepsy. Seizure frequency did not show any influence on flow values or side-to-side asymmetry. Patients taking phenytoin had a significantly lower mean cerebral blood flow (mean 9.5%) and lower mean cerebellar blood flow (mean 12.9%) than those not taking it. Moreover, phenytoin reduced regional cerebral blood flow in the temporal regions more prominently on the contralateral side of the epileptic focus than on the ipsilateral side. Positive MRI findings of hippocampal sclerosis along with visually detected temporal hypoperfusion on SPECT showed a lower regional cerebral blood flow and greater flow asymmetry than other imaging findings in the temporal region. Results suggest that noninvasive cerebral blood flow measurements using Tc-99m HMPAO may give useful information about interictal cerebral blood flow around an epileptic focus and about the effects of antiepileptic drugs on brain function in temporal lobe epilepsy.

Nasal mucosal thickening simulating a tumor: potential for misdiagnosis in brain perfusion imaging

A 33-year-old, female presenting with dementia was admitted to our institution. Except for slight muscle atrophy noted on both lower extremities there were no other significant physical signs or laboratory findings. Since initial Tc-99m HMPAO SPECT showed hypoperfusion on both temporal, parietal and occipital lobes, follow up study with the same radiotracer was done. Increase in uptake was noted in the left side of the face. There was no abnormality noted on ENT examination. CT scan and MRI showed slight nasal mucosal wall thickening. T1-201 SPECT showed increased uptake in the nasal area. The increase in uptake could be due to nasal mucosal thickening. This could simulate nasal tumor and interfere in determining ROI for brain perfusion studies.

Simplified quantification of regional cerebral blood flow with 99mTc-ECD SPECT and continuous arterial blood sampling

The goal of this study was to develop a simple method for quantification of regional cerebral blood flow (rCBF) with 99mTc-ethyl cysteinate dimer (ECD) SPECT. Following an intravenous constant infusion of ECD for one minute, serial dynamic SPECT imaging was performed for 40 minutes in 6 healthy male volunteers with intermittent arterial blood sampling. PET scan with 15O-water was performed on the same day before the SPECT study for measurement of rCBF. Arterial blood data demonstrated rapid conversion of ECD to the hydrophilic metabolites, and most of the arterial input to the brain was completed within 5 minutes after the injection. Brain activity reached a peak value soon after the cessation of infusion, and was stable thereafter with very little washout. Net extraction of ECD in the brain calculated by arterial input of ECD and rCBF demonstrated a rapid decrease within a few minutes, reaching 42.7% at 5 minutes. The simulation study suggested that the arterial blood activity obtained by continuous drawing for 5 minutes and a single SPECT scan would provide a reasonable estimate of rCBF under the assumption of constant net extraction in the brain.

A quantitative approach to technetium-99m ethyl cysteinate dimer: a comparison with technetium-99m hexamethylpropylene amine oxime

To develop non-invasive regional cerebral blood flow (rCBF) measurements using technetium-99m ethyl cysteinate dimer (99mTc-ECD) and single-photon emission tomography (SPET), the same graphical analysis as was described in our previous reports using technetium-99m hexamethylpropylene amine oxime (99mTc-HMPAO) was applied to time-activity data for the aortic arch and brain hemispheres after intravenous injection of 99mTc-ECD. Hemispherical brain perfusion indices (BPI) for 99mTc-ECD showed a highly significant correlation (n = 22, r = 0.935, P = 0.0001) with those for 99mTc-HMPAO in 11 patients who underwent both tracer studies. Using both linear regression line equations between 99mTc-ECD BPI and 99mTc-HMPAO BPI and between 99mTc-HMPAO BPI and mean cerebral blood flow (CBF) values obtained from a xenon-133 inhalation SPET method in a previous study, 99mTc-ECD BPI was converted to 133Xe CBF values (y = 2.60 chi + 9.8). Then raw SPET images of 99mTc-ECD were converted to rCBF maps using Lassen's correction algorithm. In this algorithm, the correction factor alpha was fixed to 1.5, 2.6 and infinite. In the comparison of rCBF values for 99mTc-ECD SPET with those for 99mTc-HMPAO SPET in 396 regions of interest in the aforementioned 11 patients, the fixed correction factor alpha of 2.6 gave nearly the same rCBF values for 99mTc-ECD (50.1 +/- 16.9 ml/100 g/min, mean +/- SD) as for 99mTc-HMPAO (49.9 +/- 17.3 ml/100 g/min). In conclusion, the same non-invasive method as has been used in 99mTc-HMPAO studies is applicable to a 99mTc-ECD study for the measurement of rCBF without any blood sampling.

Technetium-99m HMPAO SPET in acute supratentorial ischaemic infarction, expressing deficits as millilitre of zero perfusion

A comparative interim analysis was performed of clinical parameters, computed tomographic (CT) scan results and technetium-99m hexamethylpropylene amine oxime single-photon emission tomography (SPET) findings obtained within 12 h of acute supratentorial ischaemic infarction. First, the applicability for SPET semiquantification in this study of the "method of Mountz", simultaneously accounting for extent and degrees of hypoperfusion by expressing deficits as millilitre of zero perfusion, was considered. Next, the relative contributions of perfusion SPET and CT scan in the acute stage of ischaemic infarction were compared in 27 patients (mean age 68.8 years). Finally, the correlation of SPET lesions with clinical parameters at onset was evaluated. The method of Mountz represents a workable, accurate virtual parameter, with the assumption that the contralateral brain region remains uninvolved. Interobserver reproducibility in 12 SPET studies, with lesions varying between 6 and 369 cc, showed a correlation coefficient r of 0.99. In practice, because of inconstant distribution of activities in the brain, the method can only be applied slice by slice and not on the total global volume. While the mean delay since the onset of symptomatology was approximately 7 h for both SPET and CT scan, SPET showed lesions concordant with the clinical neurological findings in 100% and CT scan in only 48%. One could hypothesize that SPET examinations performed later would show larger functional defects, because of the development of additional functional changes secondary to biochemical alterations. However, in this regard no statistically significant differences were found between two subproups, taking the median of delay before SPET examination as cut-off.(ABSTRACT TRUNCATED AT 250 WORDS)

Epilepsy and SPECT

SPECT studies for rCBF imaging in clinical epilepsy are reviewed divided into interictal, ictal and postictal SPECT studies in partial and generalized epilepsies, as compared with the corresponding PET studies, and at times referring to SPECT studies in experimental models of epilepsy. All of the interictal, ictal and postictal SPECT scans in partial epilepsy are useful for the regional determination of epileptic foci, in view of the high appearance rates of focal abnormalities on these SPECT scans and good correlation with epileptic EEG foci. Mechanisms underlying the focal abnormality on interictal SPECT scans (i.e., focal hypoperfusion) image are complicative, and therefore, studies concerning the underlying mechanisms are reviewed with regard to correlations of the SPECT abnormality with the following various clinical factors: focal organic lesions on X-ray CT or MRI scans, frequencies of clinical seizures or interictal seizure discharges on EEGs, background EEG activity, propagation of epileptic activity, antiepileptic drugs, and cognitive functions. Further, new neurochemical SPECT studies using 123I-Iomazenil for benzodiazepine receptor imaging in clinical epilepsy are reviewed and compared with earlier SPECT studies for rCBF imaging with regard to their utility in regional determination of epileptic foci. In addition, the few SPECT or PET studies available on epileptic psychosis are reviewed.

Quantitation of rCBF by 99mTc-hexamethylpropyleneamine oxime single photon emission computed tomography combined with 133Xe CBF

A simple, noninvasive method of measuring CBF that uses single photon emission computed tomography (SPECT) of 99mTc-hexamethylpropyleneamine oxime (99mTc-HMPAO) and whole-brain CBF obtained by 133Xe clearance technique was developed. SPECT data were normalized to the count density of HMPAO uptake in the whole brain and then converted to the absolute units of CBF by multiplying average CBF in the whole brain obtained by 133Xe. Mean CBF values in healthy volunteers (n = 12) were 49 +/- 7 and 30 +/- 5 ml 100 g-1 min-1 for gray matter and white matter, respectively, with a global flow value of 45 +/- 5 ml 100 g-1 min-1. The mean flow value was 19 +/- 7 ml 100 g-1 min-1 for the core of the infarct and 31 +/- 5 ml 100 g-1 min-1 for the contralateral region (n = 13). CBF values were reproducible for all brain regions. The method was convenient to use and suitable for the routine measurement of regional CBF in normal and pathologic states.