Delayed image of iodine-123 iomazenil as a relative map of benzodiazepine receptor binding: the optimal scan time

Iodine-123-Iomazenil Single-Photon Emission Computed Tomography Revealed Recovery of Neuronal Viability in Association With Improvement of Cognitive Dysfunction After Revascularization in Moyamoya Disease

BACKGROUND AND OBJECTIVES

Recent studies indicate that 123I-iomazenil (123I-IMZ) single-photon emission computed tomography (SPECT) can demonstrate neuronal viability. Although cognitive dysfunction has been recognized as an important issue in adult patients with moyamoya disease (MMD), no standard neuroradiological methods to define such conditions have been established. We examined the relationship between cognitive function and 123I-IMZ SPECT before and after revascularization in patients with MMD.

METHODS

The study participants were 16 adult patients with MMD whose cerebrovascular reactivities were decreased only on the surgical sides of combined revascularization. Cognitive function was examined using the Mini-Mental State Examination (MMSE; cutoff: 27) and the Frontal Assessment Battery (FAB; cutoff: 16) before and at 3 to 6 months after surgery. 123I-iodoamphetamine (123I-IMP) SPECT with acetazolamide challenge and 123I-IMZ SPECT were performed concurrently while evaluating cognitive function. The radioreactivities of 123I-IMZ SPECT in regions with decreased cerebrovascular reactivities on 123I-IMP SPECT were investigated using affected-to-contralateral side asymmetry ratio (IMZ-ACR).

RESULTS

Twelve patients showed normal cognitive function (MMSE: 29.8 ± 0.4, FAB: 18 ± 0) before surgery. No evident laterality of 123I-IMZ uptake was seen (IMZ-ACR: 0.98 ± 0.04). Neither cognitive function nor 123I-IMZ SPECT worsened after surgery (MMSE: 29.8 ± 0.3, FAB: 18 ± 0, IMZ-ACR: 1.00 ± 0.04). By contrast, 4 patients presented cognitive dysfunction (MMSE: 24.3 ± 3.9, FAB: 14.8 ± 2.7) before revascularization. Preoperative imaging of these patients showed decreased 123I-IMZ uptake, and their IMZ-ACRs (0.83 ± 0.08) were significantly lower than those of the normal group. After revascularization, cognitive functions and 123I-IMZ uptake tended to ameliorate (MMSE: 27.5 ± 1.7, FAB: 16.3 ± 2.2, IMZ-ACR: 0.94 ± 0.09).

CONCLUSION

Preoperative cognitive function was associated with 123I-IMZ uptake in adult patients with MMD. After revascularization, cognitive function could be recovered in the viable areas of the brain, which is consistent with 123I-IMZ SPECT findings.

Iodine-123-Iomazenil SPECT Revealed Recovery of Neuronal Viability in Association with Improvement in Symptoms Following Treatment for Obstructive Hydrocephalus due to a Giant Posterior Cerebral Artery Aneurysm

BACKGROUND

Early and late images of ¹²³I-iomazenil (¹²³I-IMZ) single-photon emission computed tomography (SPECT) are considered to show cerebral blood flow and neuronal activity, respectively, and this modality may demonstrate temporal dysfunction of the frontal lobes in obstructive hydrocephalus. In this report, we examined ¹²³I-IMZ SPECT in a patient with chronic obstructive hydrocephalus owing to compression of the aqueduct by a partially thrombosed aneurysm of the left posterior cerebral artery for the first time.

CASE DESCRIPTION

A woman aged 77 years presented with progression of cognitive decline, gait disturbance, and urinary incontinence. She had a medical history of epilepsy and subarachnoid hemorrhage due to a ruptured left posterior cerebral artery aneurysm, treated conservatively when she was age 56 years. Magnetic resonance imaging revealed a mass lesion in the pineal region, which showed a target sign with gadolinium-based contrast agents, causing obstructive hydrocephalus owing to compression of the cerebral aqueduct. A right vertebral angiogram confirmed the presence of a partially thrombosed giant aneurysm at the left posterior cerebral artery. To rule out the involvement of nonconvulsive status epilepticus in her pathology, we performed ¹²³I-IMZ SPECT, and both early and late images demonstrated low uptake in the bilateral frontal cortex. After surgical trapping of the parent artery and resection of the aneurysm, hydrocephalus was relieved, and the symptoms disappeared along with improvement in early and late ¹²³I-IMZ SPECT images.

CONCLUSIONS

The findings in the present case indicate that ¹²³I-IMZ SPECT can detect reversible cerebral blood flow reduction and neuronal viability in the frontal lobes, which may affect the clinical manifestation of obstructive hydrocephalus.

Statistical parametric mapping of interictal 123I-iomazenil SPECT in temporal lobe epilepsy surgery

Brain single photon emission computed tomography (SPECT) for epilepsy is divided into two types (using three radionuclide tracers)-perfusion SPECT (123I-IMP or 99 mTc-ECD), identifying epileptogenic foci by detecting abnormality in regional cerebral blood flow, and 123I-iomazenil SPECT, identifying epileptogenic foci based on distribution of central benzodiazepine receptors. This study aimed to statistically evaluate and compare the SPECT effectiveness for the three tracers. Statistical parametric mapping (SPM) analysis was performed on 30 mesial temporal lobe epilepsy (mTLE) patients. The radionuclide and patient data were categorized as follows: abnormality in the medial temporal lobe on the operated hemisphere (AAA), in the entire temporal lobe on the operated hemisphere (AA), in the dominantly affected temporal lobe on the operated hemisphere (A), in bilateral temporal lobes (B), with no abnormalities in bilateral temporal lobes (C), and with abnormality in the temporal lobe on the nonoperated hemisphere (D). For analyses of (AAA), (AA), and (A), examining the hemisphere containing epileptogenic foci, IMP-SPECT was significantly superior to ECD-SPECT (P<0.05). For (AAA), indicating localization, IMZ-SPECT was significantly superior to the other two (P<0.05). IMP-SPECT was superior for lateralizing and IMZ-SPECT was useful for localizing epileptogenic foci in mTLE patients though the applicability of the results in extratemporal lobe epilepsy is unknown.

Evaluation of the GABAergic nervous system in autistic brain: (123)I-iomazenil SPECT study

PURPOSE

To evaluate the GABA(A) receptor in the autistic brain, we performed (123)I-IMZ SPECT in patients with ASD. We compared (123)I-IMZ SPECT abnormalities in patients who showed intellectual disturbance or focal epileptic discharge on EEG to those in patients without such findings.

SUBJECTS AND METHODS

The subjects consisted of 24 patients with ASD (mean age, 7.3±3.5 years), including 9 with autistic disorder (mean age, 7.0±3.7 years) and 15 with Asperger's disorder (mean age, 7.5±3.2 years). We used 10 non-symptomatic partial epilepsy patients (mean age, 7.8±3.6 years) without intellectual delay as a control group. For an objective evaluation of the (123)I-IMZ SPECT results, we performed an SEE (Stereotactic Extraction Estimation) analysis to describe the decrease in accumulation in each brain lobule numerically.

RESULTS

In the comparison of the ASD group and the control group, there was a dramatic decrease in the accumulation of (123)I-IMZ in the superior and medial frontal cortex. In the group with intellectual impairment and focal epileptic discharge on EEG, the decrease in accumulation in the superior and medial frontal cortex was greater than that in the group without these findings.

CONCLUSION

The present results suggest that disturbance of the GABAergic nervous system may contribute to the pathophysiology and aggravation of ASD, since the accumulation of (123)I-IMZ was decreased in the superior and medial frontal cortex, which is considered to be associated with inference of the thoughts, feelings, and intentions of others (Theory of Mind).

Iomazenil-single-photon emission computed tomography reveals selective neuronal loss in magnetic resonance-defined mismatch areas

BACKGROUND AND PURPOSE

The mismatch of hypoperfused tissue on perfusion imaging and ischemic tissue on diffusion-weighted imaging is used as a surrogate marker for thrombolytic therapy in the extended time window. Mismatch tissue may recover completely, progress toward infarction, or proceed toward incomplete infarction with selective loss of cortical neurons. We used [(123)I]iomazenil-single-photon emission computed tomography (IMZ-SPECT) to characterize the neuronal integrity of reperfused "tissue at risk of infarction" that appeared morphologically intact on follow-up magnetic resonance imaging (MRI).

METHODS

Twelve patients with acute stroke with striatocapsular (SC) infarctions were examined with multimodal MRI at days 0, 1, and 7; IMZ-SPECT was performed at days 5 to 15. The PI at day 0, fluid-attenuated inversion recovery (FLAIR) image at day 7, and IMZ-SPECT were coregistered and stereotactically normalized. The mismatch volume of interest (VOI) was defined as the initial PI lesion subtracted by the FLAIR lesion at day 7. An asymmetry ratio (AR) was computed by dividing the mean IMZ uptake of the mismatch VOI by the unaffected mirror VOI. The same AR was computed for signal intensity on FLAIR images at day 7. Three patients with cortical infarctions were included for calibration of the AR. In this group, the VOI consisted of the FLAIR lesion at day 7.

RESULTS

All patients with SC infarctions had a large mismatch of initially hypoperfused (112+/-31 mL; mean+/-SD) and finally infarcted tissue (19+/-14 mL). Mean AR of cortical IMZ uptake was 0.85+/-0.01 in cortical infarctions and 0.95+/-0.03 in SC infarctions; thereby AR showed a continuous distribution from clearly reduced (0.89) to normal (1.01) in SC infarctions. Mean AR for FLAIR signal intensity was 1.84+/-0.14 for cortical infarctions and normal (1.01+0.03) for SC infarctions.

CONCLUSIONS

IMZ-SPECT detected a selective loss of cortical neurons in patients with SC infarctions in transient hypoperfused tissue, which was morphologically intact on MRI.

Quantitative analysis of benzodiazepine receptor in temporal lobe epilepsy: [(125)I]iomazenil autoradiographic study of surgically resected specimens

PURPOSE

To evaluate the changes of the inhibitory neurotransmitter receptor system related to epileptogenesis by measuring central benzodiazepine receptors (BZDRs) in surgically resected specimens of temporal lobe epilepsy by using [(125)I]iomazenil autoradiography.

METHODS

Surgically resected specimens were obtained from 66 temporal lobe epilepsy patients [51 with mesial temporal lobe epilepsy (MTLE) and 15 with non-MTLE] receiving no BZDs and seven MTLE patients receiving BZDs. BZDR densities in brain sections were measured by using [(125)I]iomazenil autoradiography. Cell densities were measured from cresyl violet-stained sections.

RESULTS

Compared with non-MTLE patients, non-BZD-treated MTLE patients showed remarkable reduction of BZDR density in the pyramidal cell region of cornu ammonis (CA) 1, CA3, and CA4, and a smaller but significant reduction in CA2 and the molecular and granule cell layers of dentate gyrus (mDG). In the MTLE group, the BZDR density in the mDG correlated with that in lateral cortex. Significant correlations between BZDR density and cell density were found in all hippocampal regions. A significant difference in BZDR density/cell-density ratio was observed in CA1 region between MTLE and non-MTLE. BZD-treated patients tended to have lower BZDR densities than did non-BZD-treated patients, although the differences did not reach significance. In all MTLE cases, [(123)I]iomazenil singlephoton emission computed tomography (SPECT) showed decreased BZDR binding in MTL.

CONCLUSIONS

In MTLE, BZDR densities decreased parallel to reduction in cell density in most hippocampal subfields, but BZDR density appeared to decrease in excess of neuron loss in CA1. [(125)I]iomazenil SPECT might be useful for detecting in vivo changes of BZDR density.

Atrophy of the corpus callosum associated with a decrease in cortical benzodiazepine receptor in large cerebral arterial occlusive diseases

OBJECTIVES

It remains controversial whether selective neuronal ischaemic change develops in patients with occlusion of the large cerebral arteries. Previous studies have shown atrophy of the corpus callosum with reduced cortical oxygen metabolism in large cerebral arterial occlusive diseases, which might be indirect evidence of loss of the neurons in cortical layer 3. Recent studies of patients with ischaemic cerebrovascular diseases have demonstrated reduced central benzodiazepine receptor (BZR) binding in the normal appearing cortical areas, which might be more direct evidence of changes of the neurons. Although pathophysiology of the decreased BZR is unclear, a decrease in the cortical BZR binding with neuronal loss would cause atrophy of the corpus callosum. The purpose of this study was to determine whether atrophy of the corpus callosum is associated with a decrease in cortical BZR binding in large cerebral arterial occlusive diseases.

METHODS

Seven patients with occlusive diseases of the middle cerebral or internal carotid artery and only minor subcortical infarctions were studied. Single photon emission tomographic images of (123)I labelled iomazenil (IMZ) obtained 180 minutes after injection were analysed for BZR binding. The midsagittal corpus callosum area/skull area ratio (on T1 weighted magnetic resonance images) was compared with the cerebral IMZ uptake/cerebellar IMZ uptake ratio.

RESULTS

Compared with 23 age and sex matched control subjects, the patients had significantly decreased callosal area/skull area ratio. The degree of corpus callosum atrophy was significantly and strongly (rho=0.99, p<0.02) correlated with that of the decreases in the mean cerebral cortical IMZ uptake ratio.

CONCLUSION

Corpus callosum atrophy may occur in association with a decrease in cortical BZR binding in large cerebral arterial occlusive diseases. Corpus callosum atrophy with decreased cortical BZR binding might reflect cortical neuronal damage in large cerebral arterial occlusive diseases.

Kinetic modeling of benzodiazepine receptor binding with PET and high specific activity [(11)C]Iomazenil in healthy human subjects

Quantitation of the PET benzodiazepine receptor antagonist, [(11)C]Iomazenil, using low specific activity radioligand was recently described. The purpose of this study was to quantitate benzodiazepine receptor binding in human subjects using PET and high specific activity [(11)C]Iomazenil. Six healthy human subjects underwent PET imaging following a bolus injection of high specific activity (>100 Ci/mmol) [(11)C]iomazenil. Arterial samples were collected at multiple time points after injection for measurement of unmetabolized total and nonprotein-bound parent compound in plasma. Time activity curves of radioligand concentration in brain and plasma were analyzed using two and three compartment model. Kinetic rate constants of transfer of radioligand between plasma, nonspecifically bound brain tissue, and specifically bound brain tissue compartments were fitted to the model. Values for fitted kinetic rate constants were used in the calculation of measures of benzodiazepine receptor binding, including binding potential (the ratio of receptor density to affinity), and product of BP and the fraction of free nonprotein-bound parent compound (V(3)'). Use of the three compartment model improved the goodness of fit in comparison to the two compartment model. Values for kinetic rate constants and measures of benzodiazepine receptor binding, including BP and V(3)', were similar to results obtained with the SPECT radioligand [(123)I]iomazenil, and a prior report with low specific activity [(11)C]Iomazenil. Kinetic modeling using the three compartment model with PET and high specific activity [(11)C]Iomazenil provides a reliable measure of benzodiazepine receptor binding. Synapse 35:68-77, 2000. Published 2000 Wiley-Liss, Inc.

What do brain imaging studies tell us about anxiety disorders?

In-vivo neuroimaging allows the investigation of brain circuits involved in the experience of anxiety and of receptor changes associated with anxiety disorders. This review focuses on studies by research groups who have compared brain activation maps in different forms of anxiety and on binding studies of the benzodiazepine-GABA(A) receptor. Activation studies have revealed the involvement of many brain areas depending on the condition and the paradigm. However, the orbitofrontal cortex/anterior insula and the anterior cingulate are implicated in all the studies and may represent the nodal point between somatic and cognitive symptoms of any form of anxiety. Most studies of binding at the benzodiazepine-GABA(A) receptor are not interpretable because of substantial methodological problems, however, regional and/or global reductions are the most consistent finding in panic disorder.

[123I]Iomazenil SPECT benzodiazepine receptor imaging in schizophrenia

Deficient inhibitory neurotransmission of gamma-aminobutyric acid (GABA) has been implicated in the pathophysiology of schizophrenia based on postmortem studies. However, in vivo studies have shown predominantly negative or conflicting results. The goal of this study was to better characterize possible changes of the regional GABA(A)-benzodiazepine receptor distribution volume (BZR V3-p) in schizophrenia in vivo, using a larger sample size than previous studies. Single photon emission computed tomography (SPECT) with [123I]iomazenil was used with a constant infusion paradigm to measure the BZR V3-p under sustained radiotracer equilibrium conditions. Twenty-five patients with schizophrenia and 24 matched healthy control subjects were studied. Positive and Negative Syndrome Scale (PANSS) ratings were done in all subjects. Statistical parametric mapping (SPM) 96 was used to compare patients and control subjects as well as to study the relationship between SPECT results and composite PANSS scores based on two factorial models: the pentagonal model (positive, negative, dysphoric mood, activation, and autistic preoccupation factors) and the taxometric model (disorganized dimension). On the basis of 'absolute' values of V3-p with no normalization for total brain uptake, the schizophrenic patients showed no significant differences in BZR levels compared to the healthy control subjects. With a global normalization procedure, which is more sensitive to relative regional differences in activity, BZR V3-p was significantly decreased in the patients in the left precentral gyrus (BA 6). The relative BZR V3-p showed a significant positive correlation with duration of illness in the superior occipital gyri (BA 19). No significant correlations were observed between either absolute or relative BZR V3-p and either age or any of the composite PANSS scores based on any of the two factorial models in either patients or control subjects. No significant differences were observed between cigarette smoking vs. non-smoking patients, nor between the patients on atypical antipsychotics vs. on typical antipsychotics vs. not on any antipsychotics. In general, no significant differences in BZR V3-p were observed between patients and control subjects, except for a decrease in relative BZR V3-p in the left precentral gyrus. Grey matter atrophy is unlikely to be the cause for this decrease. However, we could not exclude that possibility. The positive correlation with duration of illness might reflect the relative preservation of neurons expressing BZR in the superior occipital gyri as compared to other cortical brain regions in schizophrenia.

Preserved benzodiazepine receptors in Alzheimer's disease measured with C-11 flumazenil PET and I-123 iomazenil SPECT in comparison with CBF

This study evaluates the regional cerebral blood flow (CBF) with H2(15)O-PET and the distribution of central benzodiazepine receptor (BZR) with C-11 flumazenil (FMZ) by PET and I-123 iomazenil (IMZ) by SPECT in Alzheimer's disease (AD). In AD, whereas the CBF was diminished in the frontal, temporal, parietal, and occipital cortex, the distribution volume of FMZ and delayed activity of IMZ were relatively preserved in these cortices, suggesting that the BZR reduction, reflecting neuronal loss, is less prominent than the CBF suppression. The mini-mental state examination score (MMS) was weakly correlated with the CBF in the parietal cortex but not with BZR. It is speculated that the neuronal density reflected by BZR is less impaired than the neuronal function assessed with blood flow in the association cortex of AD. High correlation was found between the uptake of FMZ and the delayed activity of IMZ. The delayed image of IMZ-SPECT is clinically useful to evaluate the preservation of neuronal density in the affected temoporoparietal association cortex in AD.

Decreased density of GABA-A receptors in the left sensorimotor cortex in akinetic catatonia: investigation of in vivo benzodiazepine receptor binding

OBJECTIVES

Catatonia is a psychomotor syndrome with concomittant akinesia and anxiety which both respond almost immediately to benzodiazepines such as lorazepam. The benzodiazepine receptor distribution was therefore investigated in akinetic catatonia with single photon emission tomography (SPECT) using iodine-123-iomazenil ((123) I Iomazenil).

METHODS

Ten akinetic catatonic patients, 10 psychiatric controls (similar age, sex, medication, and underlying psychiatric diagnosis but without catatonic syndrome), and 20 healthy controls were investigated with SPECT 2 hours after injection of (123) I Iomazenil. To exclude potential effects of cerebral perfusion (r-CBF) r-CBF was additionally investigated with Tc-99mECD SPECT.

RESULTS

Catatonic patients showed significantly lower iomazenil binding and altered right-left relations in the left sensorimotor cortex compared with psychiatric (p<0.001) and healthy (p<0.001) controls. In addition, there was significantly lower r-CBF in the right lower prefrontal and parietal cortex in catatonia whereas in the left sensorimotor cortex no differences in r-CBF between groups were found. Catatonic motor and affective symptoms showed significant correlations (p<0.05) with benzodiazepine binding in the left sensorimotor cortex as well as with right parietal r-CBF.

CONCLUSIONS

Reduced iomazenil binding suggests decreased density of GABA-A receptors in the left sensorimotor cortex in akinetic catatonia. In addition to reduced GABA-A receptor density in the left sensorimotor cortex the parietal cortex seems to be involved in pathophysiology of catatonic symptoms. It is concluded that, considering results from correlation analyses, both emotional and motor symptoms in catatonia seem to be closely related to left sensorimotor and right parietal alterations.

Viable tissue in an area of severely reduced perfusion demonstrated with I-123 iomazenil brain SPECT imaging of benzodiazepine receptors

A 70-year-old woman who experienced transient left hemiparesis had 90% stenosis of the right internal carotid artery. CT revealed small low-density areas in the subcortical frontal area. Baseline cerebral blood flow was reduced, and vasoreactivity was poor in the right frontoparietal area according to I-123 IMP brain SPECT with acetazolamide. The distribution of I-123 iomazenil was normal on the delayed SPECT image but reduced in the early SPECT image, mimicking baseline cerebral blood flow. The distribution of I-123 iomazenil SPECT on the delayed image reflected the normal binding potential of the benzodiazepine receptor and thus identified viable tissue in an area of severely reduced perfusion. These findings were confirmed by positron emission tomography.

Benzodiazepine receptor imaging with iomazenil SPECT in aphasic patients with cerebral infarction

To investigate the relationship between prognosis of aphasia and neuronal damage in the cerebral cortex, we evaluated the distribution of central-type benzodiazepine receptor (BZR) binding in post-stroke aphasics with [123I]iomazenil and SPECT. We performed iomazenil SPECT in six aphasic patients (aged from 45 to 75 years; all right-handed) with unilateral left cerebral infarction. Three patients showed signs of Broca's aphasia and the other three Wernicke's aphasia. Cerebral blood flow (CBF) imaging was performed with [123I]iodoamphetamine (IMP). The regions of interest (ROIs) on both images were set in the cerebral cortex, cerebellar cortex and language-relevant area in both hemispheres. Three patients were classified in the mild prognosis group and the other three in the moderate prognosis group. The left language-relevant area was more closely concerned with the difference in aphasic symptoms than the right one in both BZR and CBF distribution, but the ipsilateral to the contralateral ratio (I/C ratio) in the language-relevant areas in the BZR distribution was significantly lower in the moderate prognosis group than in the mild prognosis group, although no difference was seen for these values between the two groups in the CBF distribution. These results suggest that BZR imaging, which makes possible an increase in neuronal cell viability in the cerebral cortex, is useful not only for clarifying the aphasic symptoms but also for evaluating the prognosis of aphasia in patients with cerebral infarction.

Reduced levels of GABA-benzodiazepine receptor in alcohol dependency in the absence of grey matter atrophy

BACKGROUND

We tested the hypothesis that reduced levels of the GABA-benzodiazepine receptor occur in alcohol dependency using single photon emission tomography (SPET) and the specific GABA-benzodiazepine ligand, 123I-iomazenil.

METHOD

Neurologically and cognitively unimpaired abstinent alcohol-dependent (n = 12) and non-alcohol-dependent male subject (n = 14) underwent a 123I-iomazenil SPET scan. SPET and magnetic resonance images were co-registered and voxel-based statistical tests performed. Subjects' clinical and alcohol history were obtained with standard questionnaires. The relationships between clinical and alcohol variables and the regional level of GABA-benzodiazepine receptors were investigated using multiple regression analysis.

RESULTS

Abstinent alcohol-dependent subjects had decreased levels of GABA-benzodiazepine receptor compared with non-alcohol-dependent subjects within the frontal, parietal and temporal cortices, including regions in which grey matter atrophy was absent.

CONCLUSIONS

Alcohol dependency is associated with reduced GABA-benzodiazepine receptor levels in the absence of grey matter atrophy in some cortical regions, such as within the parietal lobe. Regional variability of reduction in GABA-benzodiazepine receptors demonstrates that alcohol does not have a global, toxic effect on the brain.

I-123 iomazenil SPECT in patients with mental disorders

The purpose of this study is visual evaluation of the distribution of I-123 iomazenil in the brains of patients with various types of mental disorder and to examine whether chronic administration of a clinical dose of benzodiazepine (BZ) affects the binding of I-123 iomazenil to BZ receptors (BZR). The subjects were 10 patients with mental disorders (3 males and 7 females) with a mean age of 26.8 yrs (range 19-39 yrs). Four of 10 patients were administered BZ for over 3 months and the other six were free of BZ for over one month. The SPECT images were obtained at 5-25 min (early) and 170-190 min (delayed), after the bolus i.v. injection of 167 MBq of I-123 iomazenil, with a triple-head gamma camera. The images were visually evaluated and the washout ratios of each region were calculated. In visual analysis, abnormalities were recognized in 5 patients on the delaye SPECT. The abnormalities were recognized more frequently in the superior frontal lobe. The washout ratio was higher in the BZ (+) patient group than in the BZ (-) patient group. I-123 iomazenil is useful, because the SPECT image with I-123 iomazenil reflects the distribution of BZR on the brain and provides the different information from that obtained with perfusion SPECT, X-ray CT or MRI. The rapid washout of I-123 iomazenil from the brains of BZ (+) patients suggests that chronic administration of a clinical dose of BZ affects the binding of I-123 iomazenil to BZR.