Non-invasive methods for absolute cerebral blood flow measurement using 99mTc-ECD: a study in healthy volunteers

Basal and Acetazolamide Brain Perfusion SPECT in Internal Carotid Artery Stenosis

Internal carotid artery (ICA) stenosis including Moyamoya disease needs revascularization when hemodynamic insufficiency is validated. Vascular reserve impairment was the key to find the indication for endarterectomy/bypass surgery in the atherosclerotic ICA stenosis and to determine the indication, treatment effect, and prognosis in Moyamoya diseases. Vascular reserve was quantitatively assessed by 1-day split-dose I-123 IMP basal/acetazolamide SPECT in Japan or by Tc-99m HMPAO SPECT in other countries using qualitative or semi-quantitative method. We summarized the development of 1-day basal/ acetazolamide brain perfusion SPECT for ICA stenosis, both quantitative and qualitative methods, and their methodological issues regarding (1) acquisition protocol; (2) qualitative assessment, either visual or deep learning-based; (3) clinical use for atherosclerotic ICA steno-occlusive diseases and mostly Moyamoya diseases; and (4) their impact on the choice of treatment options. Trials to use CT perfusion or perfusion MRI using contrast materials or arterial spin labeling were briefly discussed in their endeavor to use basal studies alone to replace acetazolamide-challenge SPECT. Theoretical and practical issues imply that basal perfusion evaluation, no matter how much sophisticated, will not disclose vascular reserve. Acetazolamide rarely causes serious adverse reactions but included fatality, and now, we need to monitor patients closely in acetazolamide-challenge studies.

Evaluation of 99mTC-ECD SPECT/CT brain Imaging with NeuroGam analysis in Moyamoya disease after surgical revascularization

To evaluate the clinical value of NeuroGam software in assessing the brain foci perfusion changes by TC-ECD single photon emission computed tomography/computed tomography (SPECT/CT) brain imaging in patients with Moyamoya Disease (MMD).Seventy-two patients with MMD who underwent superficial temporal artery-middle cerebral artery (STA-MCA) bypass combined with encephalo-duro-myo-synangiosis (EDMS) surgical revascularization were included. Baseline and follow-up TC-ECD SPECT/CT brain scans were performed on all patients at least twice before and after operation. Pre- and post-SPECT dicom images were reoriented into Talairach space using NeuroGam Software package. Additional visual analysis was performed. Differences mean pixel value between pre- and post- operation brain perfusion were assessed with paired t test and McNemar test.Significant differences in the number of hypoperfusion foci were found between visual assessment and NeuroGam aided assessment. More hypoperfusion foci were found by NeuroGam software aided assessment in the frontal, parietal, temporal, occipital lobe, thalamus, basal ganglia and cerebellum before and after surgery (P < .0001). According to NeuroGam software assessment, the perfusion of frontal, parietal, temporal lobe, anterior and middle cerebral regions on the operative side significantly improved before and after surgery (t = -3.734, t = -3.935, t = -5.099, t = -4.006, t = -5.170, all P < .001). However, no significant differences were found in the occipital lobe (t = -1.962, P = .054), thalamus (t = 1.362, P = .177), basal ganglia (t = -2.394, P = .019), and cerebellum (t = 1.383, P = .171) before and after surgery.The NeuroGam software provides a quantitative approach for monitoring surgical effect of MMD in a variable time (3-12 months after surgery). It could discover the perfusion changes that are neglected in conventional visual assessment.

Applying Pulse Spectrum Analysis to Facilitate the Diagnosis of Coronary Artery Disease

Not all patients with angina pectoris have coronary artery stenosis. To facilitate the diagnosis of coronary artery disease (CAD), we sought to identify predictive factors of pulse spectrum analysis, which was developed by Wang and is one technique of modern pulse diagnosis. The patients suffered from chest pain and received cardiac catheterization to confirm the CAD diagnosis and Gensini score were recruited. Their pulse waves of radial artery were recorded. Then, by performing a fast Fourier transform, 10 amplitude values of frequency spectrum harmonics were obtained. Each harmonic amplitude was divided by the sum of all harmonic amplitude values, obtaining the relative percentages of 10 harmonics (C1-C10). Subsequently, multivariate logistic regression was conducted with two models and the areas under the receiver operating characteristic curves (ROC) of these 2 models were compared to see if combining the pulse diagnosis parameters with the risk factor of CAD can increase the prediction rate of CAD diagnosis. The predictive factors of CAD severity were analyzed by multivariate linear regression. A total of 83 participants were included; 63 were diagnosed CAD and 20 without CAD. In the CAD group, C1 was greater and C5 was lower than those of the non-CAD group. The CAD risk factors were put alone in Model 1 to perform the multivariate logistic regression analysis which had a prediction rate of 77.1%; while putting the C1 and C5 harmonics together with the risk factors into Model 2, the prediction rate increased to 80.7%. Finally, the area under ROC of Model 1 and Model 2 was 0.788 and 0.856, respectively. Furthermore, left C1, left C5, gender, and presence of hyperlipidemia were predictors of CAD severity. Therefore, pulse spectrum analysis may be a tool to facilitate CAD diagnosis before receiving cardiac catheterization. The harmonics C1 and C5 were favorable predictive indicators.

Fully automatic input function determination program for simple noninvasive (123)I-IMP microsphere cerebral blood flow quantification method

We recently developed a simple noninvasive (123)I-IMP microsphere (SIMS) method using chest dynamic planar images and brain single photon emission computed tomography. The SIMS method is an automatic analysis method, except for the process of setting the region of interest (ROI) of the input function. If a fully automatic ROI setting algorithm can be developed to determine the input function for the SIMS method, repeatability and reproducibility of the analysis of regional cerebral blood flow (rCBF) of the SIMS method can be guaranteed. The purpose of this study is to develop a fully automatic input function determination program for the SIMS method and to confirm the clinical usefulness of this program. The automatic input function determination program consists of two ROI setting programs for the PA and lung regions, and it is developed using the image phase analysis of a chest RI angiogram. To confirm the clinical usefulness of this program, the rCBF in 34 patients measured using the automatic method were compared with the values obtained through the manual setting method. Input functions by the automatic and manual methods were approximately equal. A good correlation was observed between the rCBF values obtained by the automatic method and those obtained by the manual setting method (r=0.96, p<0.01). Further, the total time taken for the automatic SIMS analysis is 1-2min as compared to 20-30min for the current analysis, and therefore, this technique contributes to the improvement of the throughput of nuclear medical examinations.

Development of a simple non-invasive microsphere quantification method for cerebral blood flow using I-123-IMP

OBJECTIVE

In clinical practice, measurement of the rCBF has mainly been conducted by I-123-N-isopropyl-p-iodoamphetamine ((123)I-IMP) SPECT using the microsphere (MS) method, with continuous arterial blood sampling. While several non-invasive (123)I-IMP quantification methods have been developed, their accuracy has been shown to be lower than that of the MS method. Therefore, a non-invasive quantification method for use in routine clinical practice is being sought. The purpose of this study was to develop a simple non-invasive (123)I-IMP quantification method (SIMS method) with a simple input function-determining protocol based on the MS method.

METHOD

The input function for the SIMS method was determined using the administered dose and the integrated lung washout ratio obtained by analyzing the count-time activity curve of the pulmonary artery and lung on dynamic chest images. The mean CBF (mCBF) and input function measured in 80 patients by the SIMS method was compared with those determined using the MS method.

RESULT

A good correlation was observed between the counts measured by continuous arterial blood sampling in the MS method and the estimated counts by image analysis in the new method (r = 0.94, p < 0.01). Similarly, a good correlation was observed between the mCBF values determined by the MS method and the SIMS method (r = 0.83, p < 0.01).

CONCLUSION

The mCBF values determined by the SIMS method were closely consistent with the values obtained by the MS method. This finding indicates the possibility of use of the SIMS method for routine clinical study.

New Regression Equation for 123I-IMP Non-invasive Cerebral Blood Flow Measurement Using the Graph Plot Method

PURPOSE

A graph plot (GP) method using 123I-N-isopropyl-p-iodoamphetamine (123I-IMP) has been proposed as a simple and non-invasive estimation of quantitative cerebral bloodflow (CBF). A regression equation for the GP method was estimated by the data of resting state. Therefore, the accuracy of CBF values in high flow range may be an underestimated possibility in this method.The aim of this study was to formulate a new regression equation for the GP method by the data of resting state and acetazolamide (ACZ) challenge, and to clarify the accuracy of it.

METHODS

The images of 26 consecutive patients who underwent both 123I-IMP chest radioisotope-angiography (RIA) and single photon emission computed tomography (SPECT) examinations were used to construct the new regression equation. Examinations of the resting state and ACZ challenge were performed in different days. All patients were analyzed by both the GP method and autoradiography (ARG) method which is the conventional examination with the one-point arterial blood sampling. A linear regression equation between the index of the input function was obtained by the GP method and CBF value of ARG. The linear regression equation based on the resting data was compared with the equation based on the resting and ACZ challenge (rest+stress) data.

RESULTS

Goodliner correlation was obtained between the index of the input function obtained by the GP method and CBF value of the ARG method in the rest+stress state (y=2.75x+15.1, r=0.78). In contrast, correlation results between the index of the input function obtained by the GP method and CBF value of the ARG method in the resting state was expressed as y=2.28x+18.4, r=0.54 rCBF values based on the resting data was 20% underestimated in the high flow range compared with values based on the rest+stress data.

CONCLUSION

The new linear regression equation for the GP method is useful for clinical study. Key words: non-invasive cerebral blood flow measurement method, graph plot (GP), autoradiography (ARG), 123I-N-isopropyl-p-iodoamphetamine (123I-IMP).

Pharmacological blood pressure lowering in the older hypertensive patients may lead to cognitive impairment by altering neurovascular coupling

The link between both high and low blood pressure (BP) levels and cognitive impairment in later life has been reported in several studies. The mechanisms for this link are unclear but may be related to abnormalities in brain blood flow control. Our previous work has shown that cerebral autoregulation (CA) is unimpaired in both young and older people with hypertension at rest and that ageing does not appear to impact on the increase in the cerebral blood flow response to increased metabolic demand of neurones and other cells of the nervous system due to heightened activity (Neurovascular Coupling, NVC). Nonetheless, it is plausible that NVC efficiency becomes compromised during mental activity in older people with hypertension and that certain classes of anti-hypertensive agents may exacerbate the situation by reducing both NVC and CA contributing to cognitive decline. Such a link would have a major impact on prescribing patterns for anti-hypertensive medication.

[Determination of the optimal ROI setting position of the input function for the ⁹⁹mTc-ethyl cysteinate dimmer brain uptake ratio method]

Determination of the input function for the (99m)Tc-ethyl cysteinate dimmer brain uptake ratio ((99m)Tc-ECD BUR) method as a non-invasive quantitative measurement of cerebral blood flow measurement is of critical importance in order to improve the accuracy of this method. The input functions were experimentally obtained by setting the regions of interest (ROIs) in the ascending aorta, aortic arch, and descending aorta on the 49 chest RI-angio images. rCBFs by the BUR method with 3 input functions of the 6 cases were compared with those by the (123)I-iodoamphetamine (IMP) continuous arterial blood sampling method in order to determine the best location for the ROI of the input function. The input function of the ascending aorta was higher than those of the aortic arch and the descending aorta. The input functions of the aortic arch and the descending aorta decreased due to the origin of the three branches of the right brachiocephalic artery, left subclavian artery, and left common carotid artery. A good correlation was found in the regional cerebral blood flow (rCBF) values between the (123)I-IMP continuous arterial blood sampling method and the (99m)Tc-ECD BUR method with the input function of the ascending aorta. Therefore, the ascending aorta is the best location for the ROI of the input function for the (99m)Tc-ECD BUR method.

Investigation of blood perfusion and metabolic activity of brain tumours in adults by using 99mTc-methoxyisobutylisonitrile

OBJECTIVES

(i) To examine blood perfusion and metabolic activity of various brain tumours using radionuclide cerebral angiography (RCA) and single-photon emission tomography (SPET) after a single dose of Tc-methoxyisobutylisonitrile (MIBI). (ii) To examine if the inclusion of RCA can improve insight into the relative contribution of tumour perfusion to the uptake of MIBI shown by SPET, and to improve evaluation of tumour biology. (iii) To determine the value and the roles of MIBI in the management of brain tumour patients.

METHODS

Fifty adult patients (38 male, 12 female) with a total of 56 intracranial space-occupying lesions have been included prospectively, 37 of which were newly diagnosed and the remaining with signs of recurrence/rest of earlier resected and irradiated brain tumours. The control group consisted of nine volunteers with no evidence of organic cerebral disease. Scintigraphic examination consisted of a dynamic first-pass study lasting 60 s (3 s/frame) and two SPET studies (60 projections each, 25 s/projection), starting 15 min and 2 h after intravenous injection of MIBI. Regions of interest of the tumour and normal brain tissue were drawn on RCA and both early and delayed SPET slices. The following tumour/brain activity ratios have been calculated: (i) tumour perfusion index (P); (ii) early uptake index (E); (iii) delayed uptake index (D); and(iv) retention index (R). Analogous indices have been calculated from the same examinations performed in controls, reflecting maximal physiologic regional variations of perfusion and uptake in brain tissue.

RESULTS

Mean P of various brain tumours (low-grade gliomas 0.98, anaplastic gliomas 1.14, glioblastoma multiforme 1.20, metastases 1.09, lymphomas 1.08) differ little from each other and do not exceed maximal physiologic regional variations of cerebral perfusion (1.33), with the exception of meningioma (1.87, F=2.83, P=0.015). The receiver operating characteristics curve analysis of P showed that for the cut-off value of 1.45 the sensitivity for distinguishing meningioma from other tumours is 75%, specificity 87%, positive predictive value 33% and negative predictive value 97%. Mean E of malignant brain tumours (8.3, n=31, 23 primary, eight secondary), except anaplastic gliomas (3.5, n=5), differed significantly (P=0.02) from those of benign gliomas (3, n=9) but not from that of meningioma (11.9, n=4). The cut-off value for distinguishing malignant from benign lesions on the basis of E set at 4.8 resulted in sensitivity 67%, specificity 75%, accuracy 70%, positive predictive value 80% and negative predictive value 60%. D and R showed tendency of wash-out of MIBI from meningiomas, but otherwise did not improve the results substantially.

CONCLUSION

Integrated results of RCA and SPET with Tc-MIBI indicate that blood perfusion, blood-tumour barrier permeability and metabolic activity of the tumour are all very important for the resultant uptake shown by SPET. If the perfusion index is less than 1.45, then meningioma can be ruled out. Early SPET is recommendable for distinguishing glioblastoma from low-grade gliomas, as a complement to standard magnetic resonance imaging and/or computed tomography.

Cerebral Blood Flow in Depressed Patients with Systemic Lupus Erythematosus

Objective.

To characterize the neural circuitry involved in depression associated with systemic lupus erythematosus (SLE), we used single photon emission computed tomography (SPECT) to study regional cerebral blood flow (CBF) in patients with SLE.

Methods.

SPECT with 99mTc-ethylcysteinate dimer was performed in 30 depressed women patients with SLE, in 14 women patients with SLE and without history of neuropsychiatric disorders, and in 25 healthy women controls. Magnetic resonance imaging was done for all subjects for diagnostic purposes. Analysis of CBF patterns was performed using statistical parametric mapping. Statistical significance was taken at uncorrected p < 0.001 at cluster level.

Results.

There were no significant differences between depressed and nondepressed patients with SLE for any rheumatologic variable. In comparison to healthy controls, depressed patients with SLE had significantly reduced CBF in bilateral frontal and temporal cortex; global maximum was located in the left precentral gyrus. There were no significant CBF differences between nondepressed patients with SLE and controls. Compared to nondepressed patients with SLE, depressed patients with SLE had significantly lower CBF in 2 clusters that had their local maxima in the right precentral gyrus and in the left superior temporal gyrus. The duration of SLE correlated with decreased perfusion in the left middle and superior frontal gyrus.

Conclusion.

Depressed patients with SLE have CBF reductions in discrete temporal and frontal regions that may account for depressive symptoms.

Cyanide-induced akinetic rigid syndrome: Clinical, MRI, FDG-PET, β-CIT and HMPAO SPECT findings

A 35-year-old female ingested a lethal dose of potassium cyanide in a suicide attempt. She survived following antidote therapy and intensive care. Following artificial coma she presented with an agitative state for several days followed by akinetic mutism, buccofacial and ideomotoric aphasia. Severe rigid-akinetic syndrome, dysarthria, dysphagia and generalized dystonia developed weeks later. MRI revealed lesions in the caudate and lentiform nuclei, precentral cortex, and cerebellum. SPECT by [123-I] 2 beta-carbomethoxy-3-beta-(4-iodophenyl)-Tropan on two occasions revealed progressive loss of dopamine transporter suggestive of nigral neuronal apoptosis. Striatal and frontal hypometabolism and hypoperfusion were found by FDG-PET and HMPAO SPECT.

Changes in Cerebellar Blood Flow After Manipulation of the Cervical Spine Using Technetium 99m–Ethyl Cysteinate Dimer

BACKGROUND

Cervical spine manipulation is one of the many interventions practiced by health professionals to treat musculoskeletal disorders of the cervical spine. Although serious consequences of manipulation have been documented, the incidence is thought to be rare. More frequently, there may be minor transient side effects after manipulation of the cervical spine, such as headache, dizziness, and nausea. One of the hypothesis is that these side effects are caused by ischemia in the areas perfused by the vertebral arteries.

OBJECTIVE

The purpose of this study was to investigate whether manipulation of the cervical spine can influence blood flow in the brain.

METHODS

Single photon emission computed tomography was used to examine changes in regional cerebral blood flow caused by cervical spine manipulation (CSM) performed by a physiotherapist to 15 volunteers, using a 1-day split-dose Technetium 99m-ethyl cysteinate dimer single photon emission computed tomography activation paradigm.

RESULTS

One brain region was identified showing a decreased regional cerebral blood flow after manipulation. This region was situated in the anterior lobe of the left cerebellum (-42, -48, -24).

CONCLUSIONS

These findings suggest that cerebellar hypoperfusion may occur after CSM. This could explain why certain people experience headache, dizziness, or nausea after CSM. Further investigation into patient symptoms in the presence of cerebellar hypoperfusion and the possible link of these findings with other adverse reactions are warranted.

Psychomotor retardation correlates with frontal hypoperfusion and the Modified Stroop Test in patients under 60-years-old with major depression

Frontal hypoperfusion and frontal dysfunction have been reported in patients with major depression. It was also found that frontal hypoperfusion correlated with frontal dysfunction evaluated by neuropsychological tests in depressive patients aged 60 or over. These findings suggested that depression may cause frontal dysfunction and frontal hypoperfusion, and that these pathophysiological changes are manifested as psychomotor retardation. We performed single photon emission computed tomography and Modified Stroop Test on 35 patients with depression aged 25-83 to investigate association of depressive symptoms and psychological tests with cerebral blood perfusion. Additionally, we divided the patients into a younger (less than 60 years old) and an older (60 or over) group to examine the effect of age. Significant correlations were found between frontal perfusion, interference measure on Modified Stroop Test, and psychomotor retardation in all patients. These correlations were also found in the younger group. There was no significant difference on frontal perfusion, interference measure of the Modified Stroop Test, and psychomotor retardation between the two groups. The present findings suggest that frontal hypoperfusion, frontal dysfunction, and psychomotor retardation were associated with one another in not only the old but also the young patients with depression.

Asymmetric regional cerebral blood flow in sedated baboons measured by positron emission tomography (PET)

The analysis of structural brain asymmetry has been a focal point in anthropological theories of human brain evolution and the development of lateralized behaviors. While physiological brain asymmetries have been documented for humans and animals presenting with pathological conditions or under certain activation tasks, published studies on baseline asymmetries in healthy individuals have produced conflicting results. We tested for the presence of cerebral blood flow asymmetries in 7 healthy, sedated baboons using positron emission tomography, a method of in vivo autoradiography. Five of the 7 baboons exhibited hemispheric asymmetries in which left-sided flow was significantly greater than right-sided flow. Furthermore, the degree of asymmetry in 8 of 24 brain regions was found to be significantly correlated with age; older individuals exhibited a higher degree of asymmetry than younger individuals. Cerebral blood flow itself was uncorrelated with age, and differences between males and females were not significant.

Experimental performance assessment of SPM for SPECT neuroactivation studies using a subresolution sandwich phantom design

The validity domain of voxel-based statistical analysis of SPECT neuroactivation studies with statistical parametric mapping (SPM) has been investigated by a limited number of theoretical and simulation studies. In this work, an experimental setup is described with an assessment of its activation detection performance together with the influence of acquisition and processing parameters. A subresolution sandwich phantom was constructed using a printed high-resolution digital Hoffman phantom with a (99m)TcO(4)-ink mixture. Activations of 8, 16, and 24 mm diameter, with an intensity ranging from 5 to 60%, were constructed in the right frontal cortex, anterior and posterior cingulate, and left striatum. Triple-headed SPECT acquisitions were carried out using both fan-beam and parallel beam geometry. The impact of activation characteristics (size, intensity and location), study size, physical degradation factors, and reconstruction technique were studied using SPM99 in a group comparison design with correction for multiple comparisons. For a 15 x 15 design, all 24-mm activations of 5% intensity were detected for the fan-beam data. Decreased focus or study size, lower SPECT resolution, absence of scatter, and attenuation correction resulted in an increase in minimally detectable activation. For a single study referred to 15 control studies, only 24-mm activation foci with a minimal intensity of 10% were detected in the optimal configuration. This approach allows experimental parameter optimization of SPM-based group or single-subject SPECT activation studies compared to normal data, as used in clinical applications. In principle, these findings can be extended to SPECT receptor studies or PET data.