Validity of the γ-Ray Evaluation with iodoamphetamine for Cerebral Blood Flow Assessment (REICA) method for quantification of cerebral blood flow including acetazolamide challenge test.

OBJECTIVE: The γ-Ray Evaluation with iodoamphetamine for Cerebral Blood Flow Assessment (REICA) is a new method for quantifying cerebral blood flow (CBF) using single-photon emission computed tomography (SPECT) and [123I]N-isopropyl-p-iodoamphetamine (123I-IMP). The present study aimed to validate the REICA method using data including acetazolamide challenge test. METHODS: The REICA and Graph-Plot (GP) methods were used to calculate mean CBF (mCBF) for 92 acquisitions (rest: 57, stress: 35) and cerebrovascular reactivity (CVR) in 33 patients. To obtain stress data, 15 mg/kg of acetazolamide was injected intravenously 10 min before the administration of 123I-IMP, and blood samples were collected under the same conditions as rest data. The reference standard was the Autoradiograph (ARG) method using arterial blood sampling, and the accuracy of the REICA method was analyzed by comparing it with each method. RESULTS: For mCBF, the correlation coefficients (r) were 0.792 for the REICA method and 0.636 for the GP method. For CVR, r values were 0.660 for the REICA method and 0.578 for the GP method. In both acquisitions, the REICA method had a stronger correlation with the ARG method than the GP method. For mCBF, there was a significant difference in the correlation coefficient between the two correlation coefficients (p < 0.01). CONCLUSIONS: The REICA method was more accurate than the GP method in quantifying CBF and closer to the ARG method. The REICA method, which is a noninvasive method of cerebral blood flow quantification using 123I-IMP, has great medical usefulness.

Assessment of cerebrovascular reserve with N-isopropyl-p-[123I]-iodoamphetamine time series analysis in patients with cerebrovascular disease.

ABSTRACT: Using N-isopropyl-p-[123I]-iodoamphetamine(123I-IMP) and single-photon emission computed tomography (SPECT), the relationship between cerebrovascular reserve and the 123I-IMP redistribution phenomenon was investigated.The 50 patients who matched the inclusion criteria were divided into control and ischemia groups, and the redistribution phenomenon was examined on resting images. The delayed images showed higher 123I-IMP accumulation in lesions in the middle cerebral artery(MCA) area and anterior cerebral artery(ACA) area, these watershed areas in the ischemia group than in the control group, confirming that the redistribution phenomenon exists with statistical significance (Wilcoxon test; control group vs ischemic group in the ACA area[P = .002], ACA-MCA watershed area(P = .014), MCA area(P = .025), and MCA-posterior cerebral artery(PCA) watershed area(P = .002). The patients were then divided into 4 types according to the Kuroda grading system, and the difference in the redistribution phenomenon was investigated between type III and the other 3 types.Compared with type I and type II, type III had a significantly lower rate of decrease in the radioisotope (RI) count, verifying the redistribution phenomenon (Student t test: type I vs type III in the ACA area(P = .008), ACA-MCA watershed area(P = .009), MCA area(P < .001), and MCA-PCA watershed area(P = .002); type II vs type III in the ACA area(P = .004), ACA-MCA watershed area(P = .2575), MCA area(P < .001), and MCA-PCA watershed area(P < .001). No significant difference between type III and type IV was observed in any area [(Student t test: type III vs type IV in the ACA area(P = .07), ACA-MCA watershed area(P = .38), MCA area(P = .05), and MCA-PCA watershed area(P = .24)].The redistribution phenomenon is associated with resting cerebral blood flow (CBF), but not necessarily with cerebral vascular reactivity (CVR).

Assessment of SPECT-CT fusion images and semi-quantitative evaluation using SUV in 123I-IMP SPECT in patients with choroidal melanoma.

OBJECTIVES: The aim of this study was to assess the diagnostic ability of N-isopropyl-p-[I-123] iodoamphetamine (IMP) SPECT semi-quantitative evaluation based on the standardized uptake value (SUV) in patients with choroidal melanoma. The secondary aim was to investigate the 6-h IMP SPECT imaging in comparison with 24-h imaging. METHODS: Twenty-five patients (14 males and 11 females, mean age of 59.2-year-old) were analyzed in this retrospective study. Patients underwent 24-h IMP SPECT imaging with a gamma camera after intravenous injection of IMP. Twelve of 25 patients underwent 6-h SPECT imaging in addition to the 24-h imaging. All acquired SPECT images were fused with CT images using an image-analysis software. To assess the utility of semi-quantitative evaluation method, we introduced an image evaluation method using SUVmax comparing with conventional count-based uptake index (UI) evaluation of the lesion. Volumes-of-interest (VOIs) for SUVmax and regions-of-interest (ROIs) for UI were drawn referring to the SPECT-CT fusion image. Then the relationship between the 6- and 24-h images was examined both in SUV and UI evaluation. Furthermore, the relationship between the size category classification (SCC) by UICC/AJCC: 1-4 scales and each semi-quantitative value using SUVmax and UI was also assessed. RESULTS: SUVmax of the tumor was significantly higher than that of the normal side; 2.37 ± 0.88 and 1.77 ± 0.39 (P < 0.05) on 6-h image, 4.17 ± 1.73 and 2.04 ± 0.45 (P < 0.001) on 24-h image, respectively. UI of the tumor was also significantly higher than that of the normal side; 2.24 ± 0.67 and 1.53 ± 0.35 (P < 0.01) on 6-h image, 3.79 ± 1.24 and 1.67 ± 0.44 (P < 0.001) on 24-h image, respectively. There was a strong significant linear relationship in the evaluation with SUVmax between 6- and 24-h on the tumor side (R2 = 0.88, P < 0.0001), compared to that with Tumor-UI (R2 = 0.35, P < 0.05). In addition, SUVmax of the tumor clearly differentiated the SCC of the tumor category 4 from that of category 1, where SUVmax of the tumor for categories 1‒4 were 2.56 ± 0.59, 4.33 ± 1.92, 4.63 ± 1.45, and 5.73 ± 1.69, respectively (P < 0.05, for categories 1 and 4). CONCLUSIONS: The semi-quantitative evaluation by SUV of 123I-IMP SPECT images fused with CT images is useful for detecting choroidal melanoma. Moreover, 6-h imaging with SUV-based evaluation of 123I-IMP SPECT is promising compared to the conventional count-based UI evaluation method. Trial registration This study is registered in UMIN Clinical Trials Registry (UMIN-CTR) as UMIN study ID: UMIN000038174.

Super-early images of brain perfusion SPECT using 123I-IMP for the assessment of hyperperfusion in stroke patients.

OBJECTIVE: With the advancement of reperfusion therapy in stroke patients, assessment of perfusion status after therapy is gaining importance. Hyperperfusion tends to be underestimated by the conventional early imaging of 123I-IMP brain perfusion SPECT. We evaluated the utility of super-early imaging as an adjunct to early imaging for the assessment of postischemic hyperperfusion in stroke patients. METHODS: Sixty-seven patients who underwent 123I-IMP brain perfusion SPECT within 14 days after the onset of cerebral infarction were retrospectively analyzed. Super-early (4-10 min) and early (15-45 min) images were acquired using a dual-headed gamma camera. Postischemic hyperperfusion was visually assessed using the early images alone and then using both the super-early and early images, and the frequency of postischemic hyperperfusion and the confidence level of the judgement were evaluated. For quantitative evaluation of image contrast, the contrast ratios (the count ratios of the hyperperfused to normal areas) were calculated. RESULTS: The frequency of postischemic hyperperfusion was significantly higher using both the super-early and early images (28/67 patients) than using the early images alone (17/67 patients, p < 0.001). In 56 patients in whom judgement regarding the presence or absence of postischemic hyperperfusion was unchanged, the confidence level was increased in 8 patients using both image sets. The addition of the super-early SPECT images was judged to be useful and marginally useful in 14 and 15 patients, respectively. The contrast ratio was significantly higher on the super-early images (1.48 ± 0.25) than on the early images (1.26 ± 0.18, p < 0.001). CONCLUSIONS: The addition of super-early imaging to the conventional early imaging aids assessment of postischemic hyperperfusion by 123I-IMP brain perfusion SPECT and may contribute to management of stroke patients in the era of reperfusion therapy.

Assessment of Hemodynamic Compromise Using Computed Tomography Perfusion in Combination with 123I-IMP Single-Photon Emission Computed Tomography without Acetazolamide Challenge Test.

OBJECTIVES: The acetazolamide challenge test in conjunction with 123I-IMP single-photon emission computed tomography (SPECT) is a known method of assessing cerebrovascular reserve capacity. In this study, we investigated whether CT perfusion in combination with resting state 123I-IMP SPECT could be used instead of the acetazolamide challenge test to evaluate hemodynamic compromise in patients with atherosclerotic occlusive disease. METHODS: Twenty consecutive patients with unilateral internal carotid artery or middle cerebral artery steno-occlusive disease were enrolled. 123I-IMP SPECT was performed with and without the acetazolamide challenge test, and with CT perfusion. Cerebral blood flow (CBF), cerebral blood volume, and mean transit time (MTT) obtained by CT perfusion were compared with CBF and cerebrovascular reactivity (CVR) obtained by 123I-IMP SPECT. RESULTS: The asymmetry ratio of MTT as measured by CT perfusion showed a strong correlation with the CVR to acetazolamide as measured by 123I-IMP SPECT (ρ = -.780, P <.001). Based on the CBF obtained through 123I-IMP SPECT and the MTT obtained through CT perfusion, hemodynamic compromise was detected with high sensitivity (1.000) and specificity (.929), and a cutoff value of 30% was found to be suitable for the asymmetry ratio of MTT. MTT prolongation was significantly improved after revascularization surgery in hemodynamic compromise (P = .028). CONCLUSION: MTT as measured by CT perfusion in combination with CBF as measured by resting state 123I-IMP SPECT may be useful for evaluating hemodynamic compromise as an alternative to the acetazolamide challenge test.

Quantitative assessment of cerebral hemodynamics using single photon emission computed tomography with venous blood sampling.

OBJECTIVE: Quantitative cerebral blood flow (CBF) measured by single photon emission computed tomography (SPECT) with arterial blood sampling is one of the most reliable methods to assess the hemodynamics in individual patients. SPECT with venous blood sampling is less invasive. The present study compared the measurement of CBF using N-isopropyl-p-(iodine-123)-iodoamphetamine SPECT with venous blood sampling and with arterial blood sampling in patients with major cerebral artery occlusive disease. METHODS: Two normal subjects and 14 patients with major cerebral artery occlusive disease underwent SPECT with arterial and venous blood sampling. The microsphere method was used for quantitative SPECT imaging. Whole brain radioactivity was corrected when the detectors rotated in the forward direction (F1-F7). Venous sampling was performed 30min after radiotracer injection. Arterial blood radioactivity was estimated by multiple regression analysis from these parameters. The cerebrovascular reactivity to acetazolamide was also measured. RESULTS: Multiple regression analysis established the following formula:(where Ca10 is the arterial blood radioactivity at 10min, F1-F7 are the whole brain radioactivity in the forward direction, Cv30 is the venous blood radioactivity at 30min). Mean CBF values were 32.2±6.6ml/100g/min for measured arterial radioactivity and 42.2±7.8ml/100g/min for calculated arterial radioactivity based on venous radioactivity. CONCLUSIONS: The present modified method of calculating quantitative CBF from whole brain and venous blood radioactivities correlated well with values determined with arterial blood radioactivity.

Diagnosis of uveal malignant melanoma by a new semiquantitative assessment of N-isopropyl-p-[123I]-iodoamphetamine.

PURPOSE: To semiquantify the uptake of N-isopropyl-p-[(123)I]-iodoamphetamine (I-123 IMP) in patients with uveal malignant melanoma reproducibly and objectively. METHODS: Fifty-two patients were examined. Twenty-nine patients had malignant melanoma (group A), three were clinically diagnosed with metastatic choroidal tumor, and 20 patients were given either histological or clinical diagnoses of either benign pigmented lesion or tumor (group B). Early and delayed I-123 IMP images were obtained and standardized by Neurostat software. Using fusion software, we applied a three-dimensional region of interest (3D-ROI) template to the standardized I-123 IMP, and calculated the retention index and tumor-to-nontumor (T/N) ratio of the delayed phase using the maximum count for each ROI. RESULTS: Sensitivity at the retention index cutoff of 30 was 82.4%, specificity was 85.2%, and accuracy was 83.6%. Sensitivity at the T/N ratio of the delayed phase cutoff of 1.3 was 91.2%, specificity was 77.8%, and accuracy was 85.2%. The positive predictive value of the T/N ratio was better than that of the retention index. The negative predictive value of the retention index was better than that of the T/N ratio. CONCLUSION: This new semiquantitative estimation method is reproducible and objective, especially when the examinations are performed repeatedly for evaluation of both therapy and follow-up.

Measurement of cerebral blood flow by the autoradiographic method with N-isopropyl-4-[I-123] iodoamphetamine: comparison of radiopharmaceuticals marketed by different companies in Japan.

OBJECTIVE: Iodine-123-labeled N-isopropyl-4-iodoamphetamine (IMP) is used as a tracer for the measurement of cerebral blood flow (CBF) by single-photon emission computed tomography (SPECT). Two IMP products, IMP(A) (Nihon Medi-Physics Co., Ltd.) and IMP(B) (FUJIFILM RI Pharma Co., Ltd.), produced by different radiopharmaceutical companies are marketed for clinical use in Japan. Although no significant difference in whole-body distribution between the two products has been reported, a significant difference in the radioactivity of the octanol-extracted fraction in whole blood between the two products has been reported in humans. In this study, CBF values obtained by the autoradiographic (ARG) method obtained from both IMP(A) and IMP(B) were compared in the same human subjects. METHODS: SPECT studies were performed on 6 healthy subjects with the use of both IMP(A) and IMP(B). Standard input functions used in the ARG method were obtained for both IMP(A) and IMP(B) from 5 additional healthy subjects. RESULTS: Significant differences were found between CBF values when SPECT data with IMP(A) was combined with the standard input function for IMP(B) (37.7 +/- 3.7 mL/100 g/min at a mid-scan time of 30 min) and SPECT data with IMP(B) was combined with the standard input function for IMP(A) (50.7 +/- 8.9 mL/100 g/min). Nearly the same CBF values were found when SPECT data with IMP(A) was combined with the standard input function for IMP(A) (43.1 +/- 4.4 mL/100 g/min) and SPECT data with IMP(B) was combined with the standard input function for IMP(B) (44.2 +/- 7.6 mL/100 g/min). CONCLUSIONS: Our results suggest that the appropriate standard input function should be used, according to the IMP product used, in the calculation of CBF by the ARG method.

Simple assessment of cerebral hemodynamics using single-slab 3D time-of-flight MR angiography in patients with cervical internal carotid artery steno-occlusive diseases: comparison with quantitative perfusion single-photon emission CT.

BACKGROUND AND PURPOSE: Visualization of the peripheral arteries on single-slab 3D time-of-flight (TOF) MR angiography (MRA) can reflect blood flow velocity. The velocity in the middle cerebral artery (MCA) may correlate with cerebrovascular reactivity (CVR) to acetazolamide, which can be used to assess hemodynamic impairment. The goal of this study was to compare the signal intensity of the MCA on MRA versus CVR quantified by perfusion single-photon emission CT (SPECT). MATERIALS AND METHODS: The signal intensity of the MCA on single-slab 3D time-of-flight MRA was graded according to the ability to visualize the MCA in 108 cerebral hemispheres of 87 patients with unilateral or bilateral cervical internal carotid artery (ICA) steno-occlusive diseases. SPECT-CVR was also calculated by measuring cerebral blood flow before and after acetazolamide challenge. Ten healthy subjects were studied to obtain control SPECT-CVR values. All subjects provided written informed consent before the study. RESULTS: CVR was significantly lower in cerebral hemispheres with reduced MCA signal intensity than in those with normal intensity (P < .05). When the reduced signal intensity of the MCA on MRA was defined as abnormal, and when a CVR less than the mean--2 SD of healthy subjects was defined as reduced, MRA grading resulted in a 86.2% sensitivity and 69.6% specificity, with 51.0% positive-predictive and 93.2% negative-predictive values to detect reduced CVR. CONCLUSIONS: This simple MRA method can assess hemodynamic impairment with a high negative-predictive value.

Frontal assessment battery and brain perfusion image in Parkinson's disease.

The objective was to compare brain perfusion image using 3-dimensional stereotactic surface projection analysis of N-isopropyl-p-123I iodoamphetamine single photon emission computed tomography between Parkinson's disease patients with a high frontal assessment battery score and those with a low frontal assessment battery score. Thirty nondemented patients with Parkinson's disease were studied. Patients were divided into 2 groups: a high-scoring group whose frontal assessment battery score was 12 or more and a low-scoring group whose frontal assessment battery score was 11 or less. The high-scoring group included 21 patients, and the low-scoring group included 9 patients. They underwent N-isopropyl-p-123I iodoamphetamine single photon emission computed tomography, and we analyzed the data by the 3-dimensional stereotactic surface projection method. Results showed that left inferior parietal lobule and left supramarginal gyrus perfusion of the low-scoring group were significantly decreased compared with the high-scoring group. It is concluded that patients with Parkinson's disease may have frontal lobe dysfunction, but the decreased frontal assessment battery score may be caused not by progressed frontal lobe dysfunction but by parietal lobe dysfunction added to their preexisting frontal lobe impairment.

Assessment of cerebral hemodynamics in childhood moyamoya disease using a quantitative and a semiquantitative IMP-SPECT study.

BACKGROUND: We evaluated the cerebral hemodynamics in childhood moyamoya disease patients before and after surgery to assess both surgical indication and the effect of revascularization using single photon emission computed tomography (SPECT) study with N-isopropyl-p-123I-iodoamphetamine (IMP). We compared results of quantitative and semi-quantitative SPECT studies to determine parameters by the semi-quantitative method to define severe hemodynamic ischemia. METHODS: There were 14 pediatric patients with moyamoya disease who suffered transient ischemic attacks (TIAs) in the anterior circulation. Before and after surgical revascularization by STA-MCA bypass and encephalomyosynangiosis (EMS), quantitative IMP-SPECT studies using the autoradiographic method (IMP-ARG method) were performed. Resting regional cerebral blood flow (rCBF) and regional vascular reserve (rVR) were measured in bilateral cortical territories (ROI) and cerebellum. Semi-quantitative parameters were calculated from the ratio of ROI counts to the dominant cerebellar counts (ROI/Ce ratio) at resting and acetazolamide-activated conditions. RESULTS: Before surgery, the mean resting rCBF and rVR in bilateral ACA and MCA territories were less than 40 ml/100 g/min and less than 10%, respectively, indicating severe hemodynamic ischemia. Except for the ACA territories, both the mean resting rCBF and mean rVR values in the entire cortex increased significantly after surgery (p < 0.05). By semi-quantitative studies, before surgery, the mean resting and acetazolamide-activated ROI/Ce ratios in bilateral ACA and MCA territories were less than 0.90 and 0.80, respectively. The mean resting and acetazolamide-activated ROI/Ce ratios increased significantly in the MCA territory after surgery. Severe hemodynamic ischemia, which categorized by the quantitative thresholds (resting rCBF < 40 ml/100 g/min and rVR < 10%) was diagnosed by the semi-quantitative thresholds (resting ROI/ Ce ratio < 0.90 and acetazolamide-activated ROI/Ce ratio < 0.85), the sensitivity and specificity of which were 87.5% and 90.9%, respectively. CONCLUSIONS: The cerebral hemodynamics in childhood moyamoya disease was improved entirely after surgery. Severe hemodynamic cerebral ischemia was diagnosed by not only quantitative but also semi-quantitative IMP-SPECT studies.

Development of quantitative analysis method for stereotactic brain image: assessment of reduced accumulation in extent and severity using anatomical segmentation.

Through visual assessment by three-dimensional (3D) brain image analysis methods using stereotactic brain coordinates system, such as three-dimensional stereotactic surface projections and statistical parametric mapping, it is difficult to quantitatively assess anatomical information and the range of extent of an abnormal region. In this study, we devised a method to quantitatively assess local abnormal findings by segmenting a brain map according to anatomical structure. Through quantitative local abnormality assessment using this method, we studied the characteristics of distribution of reduced blood flow in cases with dementia of the Alzheimer type (DAT). Using twenty-five cases with DAT (mean age, 68.9 years old), all of whom were diagnosed as probable Alzheimer's disease based on NINCDS-ADRDA, we collected I-123 iodoamphetamine SPECT data. A 3D brain map using the 3D-SSP program was compared with the data of 20 cases in the control group, who age-matched the subject cases. To study local abnormalities on the 3D images, we divided the whole brain into 24 segments based on anatomical classification. We assessed the extent of an abnormal region in each segment (rate of the coordinates with a Z-value that exceeds the threshold value, in all coordinates within a segment), and severity (average Z-value of the coordinates with a Z-value that exceeds the threshold value). This method clarified orientation and expansion of reduced accumulation, through classifying stereotactic brain coordinates according to the anatomical structure. This method was considered useful for quantitatively grasping distribution abnormalities in the brain and changes in abnormality distribution.

[The development of new method for the assessment of perfusion reserve using split dose iodine-123-IMP SPECT: one-day protocol by modified ARG method].

Evaluation of the regional cerebrovascular reactivity (rCVR) to a cerebral vasodilatory stimulus is important in the investigation of patients with ischemic cerebrovascular disease. We devised a simplified one-day protocol technique using [123I]N-isopropyl-p-iodoamphetamine (IMP) autoradiography (ARG) with SPECT. To validate the accuracy of IMP-ARG for quantifying rCVR to acetazolamide, we compared rCVR measured using IMP-ARG with rCVR calculated using IMP split dose method of microsphere model. Twenty patients with chronic steno-occlusive disease in a unilateral major cerebral artery underwent 123I-SPECT. On rCBF SPECT image above 3.5 cm from OM line, large cortical regions of interest (ROI) was bilaterally determined for bilateral middle cerebral artery and anterior cerebral artery. Based on rCBF values in each ROI, rCVR to acetazolamide was calculated. Significant correlation was observed between rCVR values obtained using IMP-ARG and microsphere model IMP methods in the 80 ROIs examined in the 20 patients (r = 0.72; p < 0.001). The result demonstrated that [123I]IMP-ARG split dose method can quantify rCVR non-invasively in a short time.

Qualitative versus quantitative assessment of cerebrovascular reactivity to acetazolamide using iodine-123-N-isopropyl-p-iodoamphetamine SPECT in patients with unilateral major cerebral artery occlusive disease.

BACKGROUND AND PURPOSE: Qualitative measurement of regional cerebrovascular reactivity (rCVR) to acetazolamide with single-photon emission CT (SPECT) has been widely used to determine the severity of hemodynamic impairment. We attempted to validate the accuracy of qualitative assessment by using SPECT to detect reduced rCVR compared with rCVR determined quantitatively in patients with unilateral major cerebral artery occlusion. METHODS: Regional cerebral blood flow was assessed with iodine-123-N-isopropyl-p-iodoamphetamine ((123)I-IMP) at rest and after acetazolamide activation in 133 patients with previously symptomatic, unilateral internal carotid or middle cerebral artery occlusion. Quantitative values were calculated by using the (123)I-IMP autoradiographic method and analyzed for each cerebral hemisphere as the percentage change in rCBF between resting and activation studies (%(Hem)). Qualitative rCVR was determined for the target hemisphere distal to the occlusion as the cerebral-interhemispheric asymmetry index (AI(Hem)) and as an index of flow difference between the target cerebral and ipsilateral cerebellar hemispheres (FI(Hem-Cbl)). Values 2 SDs below the mean in healthy volunteers were defined as decreased. RESULTS: Fair agreement was observed between %(Hem) and both AI(Hem) change (resting vs activation, kappa = 0.409) and FI(Hem-Cbl) change (resting vs activation, kappa = 0.440). When %(Hem) was assumed to represent the true determinant of assessing rCVR, AI(Hem) change and FI(Hem-Cbl) change demonstrated sensitivities of 68% and 78%; specificities, 72% and 76%; positive predictive values, 48% and 56%; false-positive incidences, 28% and 24%; and false-negative incidences, 32% and 22% for detecting patients with reduced rCVR, respectively. CONCLUSION: Subgroups of patients with hemodynamic impairment cannot be accurately defined by using rCVR qualitatively measured with SPECT.

Assessment of cerebral hemodynamics before and after revascularization in patients with occlusive cerebrovascular disease by means of quantitative IMP-SPECT with double-injection protocol.

UNLABELLED: The purpose of this study was to validate a double-injection (DI) method with N-isopropyl-[123I]p-iodoamphetamine (IMP) to measure regional cerebral blood flow (rCBF) twice in a single session of dynamic SPECT and to elucidate a possible role of this method to identify patients with occlusive disease of major cerebral arteries, who might benefit from cerebral revascularization procedures (CR). MATERIALS AND METHODS: Fourteen patients with occlusion or severe stenosis of the internal carotid or middle cerebral artery were studied before and after CR to assess hemodynamic changes after revascularization treatment. We quantitatively measured rCBF before and after acetazolamide (ACZ) challenge along with cerebrovascular reserve capacity (CVR) with two injections of IMP in a single session of dynamic SPECT scans (DI method). The reliability and reproducibility of the DI method were validated by means of a simulation study and in eight patients who were examined without ACZ challenge to measure baseline rCBF twice. RESULTS: The analysis of simulated noisy data with realistic noise levels showed that the errors of the estimates for the first and the second rCBF and for the increase in rCBF were 2.6%, 8.1% and 10.4%, respectively. In the 8 patients examined by the DI method to measure baseline rCBF twice, the mean and the SD of percentage differences between the two consecutive measurements in rCBF were -1.3% and 5.5%, respectively. Eight out of 14 patients with occlusive disease had at least one region with a CVR less than 10%. They showed a significant increase in resting rCBF after CR, not only in the ipsilateral hemisphere (from 26.1 +/- 6.4 to 33.4 +/- 4.7) but also in the contralateral one (from 28.3 +/- 7.0 to 34.7 +/- 4.7) with a recovery of the ipsilateral CVR from 9.3 +/- 17.2 to 41.2 +/- 20.1%. The remaining six patients with good-moderate CVR did not show an increase in rCBF after CR (from 28.0 +/- 2.7 to 28.3 +/- 3.4). The three of them with a moderate CVR (10-25%) before CR showed normalization of CVR after CR. CONCLUSION: Patients with decreased rCBF and reduced CVR benefited from CR in terms of an increase in rCBF and recovery of CVR. The quantitative double-injection IMP-SPECT has the ability to identify those patients who may benefit from CR.

Liver involvement in hereditary haemorrhagic telangiectasia: assessment with 99Tcm-phytate radionuclide angiography and 123I-IMP transrectal portal scintigraphy.

Abnormal hepatic haemodynamics and function in a 43-year-old woman with hereditary haemorrhagic telangiectasia (HHT) were evaluated using 99Tcm-phytate angiography and iodine-123-iodoamphetamine transrectal portal scintigraphy. Radionuclide angiography demonstrated hyperdynamic perfusion of the liver owing to intrahepatic arteriovenous fistulae (AVF), entry of tracer into the systemic circulation through intrahepatic portosystemic shunts and an increase in recirculating blood flow caused by these vascular disorders. Heterogeneous distribution of tracer also suggested the presence of chronic hepatic injury. Transrectal portal scintigraphy showed large portosystemic shunts. Other imaging techniques confirmed the presence of the AVF but failed to identify the portosystemic shunts. Non-invasive radionuclide studies are helpful in the evaluation of hepatic involvement of HHT.

[Assessment of brain cell function using 123I-IMP SPECT of cerebral blood flow and visual evoked potential by photic stimulation in normal and demented elderly subjects].

Cerebral blood flow was quantitatively measured using 123I-IMP SPECT by photic stimulation and visual evoked potential (VEPs) in normal and dementia subjects: 8 with Alzheimer-type dementia, 9 with cerebrovascular dementia and 7 normal elderly subjects were divided into the three groups based on the Clinical Dementia Rating (CDR) grade: Group I (CDR 0), Group II (CDR 0.5-1), Group III (CDR 2-3). The 123I-IMP SPECT measurement was conducted at rest with the eyes closed and also during photic stimulation. VEPs were measured simultaneously. The results reveal prolongation of the P2 latency of the VEPs prolonged in accordance with the increasing severity of the dementia, and quantitative cerebral blood flow was lower in Group II and Group III than in Group I at rest, while during photic stimulation it significantly increased in Group I and II, but showed no change in Group III. The results suggest that quantitative measurement of cerebral blood flow using 123I-IMP SPECT by photic stimulation may enable more detailed assessment of brain cell function.

[Assessment of regional cerebral blood flow in subcortical infarction with aphasia].

We assessed the regional cerebral blood flow (rCBF) in 8 patients with subcortical aphasia and 8 patients with subcortical infarction without aphasia using the N-isopropyl-P-[123I]-iodoamphetamine autoradiography (123I-IMP ARG) method. In this study, we evaluated vermis to left cortex ratio of CBF. In cases of Broca's aphasia (N = 2), CBF was lower in the posterior frontal regions including Broca's area, and more hypoperfused in the posterior frontal and in the posterior temporal regions, including Wernicke's area of total aphasia (N = 2). But, it was not significantly hypoperfused in those regions in the cases of Wernicke's (N = 2) and amnestic aphasia (N = 2). In the subcortical aphasia, global CBF in the left cerebral cortex was lower than that in the right cerebral cortex. However, in the subcortical infarction group without aphasia there was no difference between CBF in the left cerebral cortex and the right cerebral cortex. We conclude that hypoperfusion in the left cerebral cortex was greater than that in the right cerebral cortex and it was probably due to dysfunction of the left cerebral cortex when subcortical infarction occurred with aphasia. Though some types of aphasia were not relative to the dysfunction of the left cerebral cortex.

Effects of scatter and attenuation correction on quantitative assessment of regional cerebral blood flow with SPECT.

UNLABELLED: Appropriate corrections for scatter and attenuation correction are prerequisites for quantitative SPECT studies. However, in most cerebral SPECT studies, uniform attenuation in the head is assumed, and scatter is usually neglected. This study evaluated the effect of attenuation correction and scatter correction on quantitative values and image contrast. METHODS: Studies were performed in six normal volunteers (ages 22-26 yr) following intravenous 123I-IMP administration using a rotating, dual-head gamma camera. A transmission scan was acquired with a 99mTc rod source (74 MBq) placed at the focus of a symmetrical fanbeam collimator. Data were reconstructed using two attenuation coefficient (mu) maps: quantitative mu map from the transmission scan and a uniform mu map generated by edge detection of the reconstructed images. Narrow and broad beam mu values were used with and without scatter correction, respectively. Scatter was corrected with transmission-dependent convolution subtraction and triple-energy window techniques. Quantitative rCBF images were calculated by the previously validated IMP-autoradiographic technique, and they were compared with those obtained by (15)O-water and PET. SPECT and PET images were registered to MRI studies, and rCBF values were compared in 39 ROIs selected on MRI. RESULTS: Clear differences were observed in rCBF images between the measured and constant mu maps in the lower slices due to the airways and in the higher slices due to increased skull attenuation. However, differences were < 5% in all cerebral tissue regions, thus assumption of uniform mu introduces little bias. The scatter correction was found to increase the image contrast significantly, i.e., rCBF increased by 20%-30% in gray matter and decreased in white matter regions by 10%-20% after scatter correction, increasing gray-to-white ratio to be close to that of PET measurement. The rCBF values from the two scatter correction were not significantly different, but the triple-energy window technique suffered from increased noise. After scatter correction, rCBF values were in good agreement with those measured by PET. CONCLUSION: This study shows little loss in accuracy results from assuming uniform mu map. However, scatter correction is required for the quantitative rCBF values and gray-to-white ratios to approach those of PET.

Hemodynamic aspect of cerebral watershed infarction: assessment of perfusion reserve using iodine-123-iodoamphetamine SPECT.

UNLABELLED: The mechanism whereby watershed (WS) infarcts develop remains controversial, although a hemodynamic cause is usually assumed. The aim of this study was to investigate the relationship between the site of WS infarcts and the hemodynamic status of the cerebral circulation. METHODS: From among 96 consecutive patients with angiographically confirmed unilateral major cerebral artery obstruction (occlusion or > 70% stenosis), we investigated 29 patients with supratentorial WS infarcts on magnetic resonance imaging. The regional cerebral blood flow and perfusion reserve were quantified using the split-dose [123I]iodoamphetamine SPECT method, coupled with intravenous injection of 1 g of acetazolamide. Seven patients had a cortical WS infarct between the superficial branches of the anterior and middle cerebral arteries (MCAs) or between the middle and posterior cerebral arteries (Group C), and 22 had a deep WS infarct between the superficial branches and deep penetrating arteries of the MCA (Group D). Moreover, the patients in Group D were classified into two subgroups, i.e., Type A (n = 12), with lesions lying in the centrum semiovale above the level of the lateral ventricles, and Type B (n = 10), with lesions lying in the corona radiata adjacent to the lateral ventricles. RESULTS: Comparison of the Type of WS infarct with the clinical course of onset showed that sudden onset was more frequent in Group C than in Group D (p < 0.05). The perfusion reserve in the affected MCA territory in Group D (20.1% +/- 15.6%) was significantly lower than that in Group C (43.8% +/- 10.8%; p < 0.01) and that in 20 hemispheres (10 control subjects) without a major arterial lesion (54.7% +/- 16.4%; p < 0.01). Among the Group D patients, the patients with Type A infarcts showed a significantly lower perfusion reserve compared with those with Type B infarcts (p < 0.05). CONCLUSION: Patients with deep WS infarcts, especially Type A infarcts, showed severe hemodynamic impairment, whereas patients with cortical WS infarcts showed preserved perfusion reserve which appeared to be secondary to the embolism. The mechanism of development of WS infarcts is multifactorial, and distinguishing among these WS infarcts and from other types of infarct is important, because different pathogenic mechanisms require different therapeutic strategies.