Measurement of regional cerebral blood flow with123I-IMP using one-point venous blood sampling and causality analysis: Evaluation by comparison with conventional continuous arterial blood sampling

OBJECTIVE: Arterial input function represents the delivery of intravascular tracer to the brain. The optimal setting of this function is essential for measuring regional cerebral blood flow (rCBF) based on the microsphere model using N-isopropyl-4-[123I]iodoamphetamine (123I-IMP), in which the arterial 123I-IMP concentration (integral value) during the initial 5 min is usually applied. We developed a novel method in which the arterial 123I-IMP concentration is estimated from that in venous blood samples. METHODS: Brain perfusion SPECT with 123I-IMP was performed in 110 patients with disorders of the central nervous system. A causality analysis determined the relationship between various SPECT parameters and the ratio of the octanol-extracted arterial radioactivity concentration during the first 5 min (Caoct) to the octanol-extracted venous radioactivity concentration at 27 min after an intravenous injection of 123I-IMP (Cvoct). The Caoct/Cvoct value was estimated using various SPECT parameters and compared with the directly measured value. RESULTS: The measured and estimated values of Caoct/ Cvoct (r = 0.856, n = 50) closely correlated when the following 7 parameters were included in the regression formula: radioactivity concentration in venous blood sampled at 27 min (Cv), Cvoct, Cvoct/Cv, and 4 parameters related to cerebral tissue accumulation that were measured using a four-head gamma camera 5 and 28 min after 123I-IMP injection. Furthermore, the rCBF values obtained using the input function estimated by this method also closely correlated with the rCBF values measured using the continuous arterial blood sampling (r = 0.912, n = 180). CONCLUSION: These results suggest that this method would serve as a convenient and less invasive method of rCBF measurement in the clinical setting.     

Double-injection method for sequentially measuring cerebral blood flow with N-isopropyl-(123I)p-iodoamphetamine

We investigated the accuracy of a double-injection method for sequentially measuring cerebral blood flow (CBF) with N-isopropyl-(123I)p-iodoamphetamine (IMP) in simulation studies based on patient data and in clinical studies. The unidirectional clearance of IMP from the blood to the brain (K1; nearly equal to CBF) in the first and second sessions was calculated by means of a microsphere model. The K1 values in the first session (K1I) were calculated from Cb(5)/Int_CaI, where Cb(5) and Int_CaI are values for brain radioactivity 5 min after the first injection and for arterial blood radioactivity obtained by 5-min continuous sampling. The K1 values in the second session (K1II) were calculated by means of the following four methods. Method 1: [Cb(tz + 5) - Cb(tz)]/[Int_CaII - Ca(tz) x 5], where Cb(tz+5) and Cb(tz) are the brain radioactivity levels 5 min after the second injection and at the time the second session was started (tz), respectively. Int_CaII and Ca(tz) are the arterial blood radioactivity levels obtained by 5-min continuous sampling after the second injection and at tz, respectively. Method 2: [Cb(tz + 5) - Cb(tz)]/[Int_CaI x R], where R is the injection dose ratio. Method 3: [Cb(tz + 5) - Cb(tz) x exp(- K1I x 5/lambda)]/Int_CaII, where lambda is the population averaged partition coefficient. Method 4: same as Method 3 except that K1I was replaced by K1II obtained by means of Method 2. Theoretically, Method 4 appeared to be the best of the four methods. The change in K1 during the second session obtained by Method 1 or 2 largely depended on R and tz, whereas Method 3 or 4 yielded a more reliable estimate than Method 1 or 2, without largely depending on R and tz. Since Method 2 was somewhat superior to other methods in terms of noninvasiveness and simplicity, it also had the potential for routine clinical use. The reproducibility of two sequential measurements of K1 was investigated with clinical data obtained without any intervention. The response of CBF to acetazolamide challenge was also assessed by the above four methods. The knowledge gained by this study may assist in selecting a method for sequentially measuring CBF with a double injection of IMP.     

Database of normal human cerebral blood flow measured by SPECT: II. Quantification of I-123-IMP studies with ARG method and effects of partial volume correction

The limited spatial resolution of SPECT causes a partial volume effect (PVE) and can lead to the significant underestimation of regional tracer concentration in the small structures surrounded by a low tracer concentration, such as the cortical gray matter of an atrophied brain. The aim of the present study was to determine, using 123I-IMP and SPECT, normal CBF of elderly subjects with and without PVE correction (PVC), and to determine regional differences in the effect of PVC and their association with the regional tissue fraction of the brain. METHODS: Quantitative CBF SPECT using 123I-IMP was performed in 33 healthy elderly subjects (18 males, 15 females, 54-74 years old) using the autoradiographic method. We corrected CBF for PVE using segmented MR images, and analyzed quantitative CBF and regional differences in the effect of PVC using tissue fractions of gray matter (GM) and white matter (WM) in regions of interest (ROIs) placed on the cortical and subcortical GM regions and deep WM regions. RESULTS: The mean CBF in GM-ROIs were 31.7 +/- 6.6 and 41.0 +/- 8.1 ml/100 g/min for males and females, and in WM-ROIs, 18.2 +/- 0.7 and 22.9 +/- 0.8 ml/100 g/min for males and females, respectively. The mean CBF in GM-ROIs after PVC were 50.9 +/- 12.8 and 65.8 +/- 16.1 ml/100 g/min for males and females, respectively. There were statistically significant differences in the effect of PVC among ROIs, but not between genders. The effect of PVC was small in the cerebellum and parahippocampal gyrus, and it was large in the superior frontal gyrus, superior parietal lobule and precentral gyrus. CONCLUSION: Quantitative CBF in GM recovered significantly, but did not reach values as high as those obtained by invasive methods or in the H2(15)O PET study that used PVC. There were significant regional differences in the effect of PVC, which were considered to result from regional differences in GM tissue fraction, which is more reduced in the frontoparietal regions in the atrophied brain of the elderly.     

A method to quantitate cerebral blood flow using a rotating gamma camera and iodine-123 iodoamphetamine with one blood sampling

A method has been developed to quantitate regional cerebral blood blow (rCBF) using iodine-123-labelled N-isopropyl-p-iodoamphetamine (IMP). This technique requires only two single-photon emission tomography (SPET) scans and one blood sample. Based on a two-compartment model, radioactivity concentrations in the brain for each scan time (early: t _e ; delayed: td) aredescribed as: % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaam4qamaaBa% aaleaacaWG0baabeaakmaabmaabaGaamiDamaaBaaaleaacaWGLbaa% beaaaOGaayjkaiaawMcaaiabg2da9iaadAgacqWIpM+zcaWGdbWaaS% baaSqaaiaadggaaeqaaOWaaeWaaeaacaWG0bWaaSbaaSqaaiaadwga% aeqaaaGccaGLOaGaayzkaaGaey4LIqSaamyzamaalaaabaGaamOzaa% qaaiaadAfadaWgaaWcbaGaamizaaqabaaaaOGaamiDamaaBaaaleaa% caWGLbaabeaaaaa!4D64!\[C_t \left( {t_e } \right) = fC_a \left( {t_e } \right) \otimes e\frac{f}{{V_d }}t_e \] and % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaam4qamaaBa% aaleaacaWG0baabeaakmaabmaabaGaamiDamaaBaaaleaacaWGKbaa% beaaaOGaayjkaiaawMcaaiabg2da9iaadAgacqWIpM+zcaWGdbWaaS% baaSqaaiaadggaaeqaaOWaaeWaaeaacaWG0bWaaSbaaSqaaiaadsga% aeqaaaGccaGLOaGaayzkaaGaey4LIqSaamyzamaalaaabaGaamOzaa% qaaiaadAfadaWgaaWcbaGaamizaaqabaaaaOGaamiDamaaBaaaleaa% caWGKbaabeaaaaa!4D61!\[C_t \left( {t_d } \right) = fC_a \left( {t_d } \right) \otimes e\frac{f}{{V_d }}t_d \] respectively, where denotes the convolution integral; C _a (t), the arterial input function; f rCBF; and V _d , the regional distribution volume of IMP. Calculation of the ratio of the above two equations and a table look-up procedure yield a unique pair of rCBF and V _d for each region of interest (ROI). A standard input function has been generated by combining the input functions from 12 independent studies prior to this work to avoid frequent arterial blood sampling, and one blood sample is taken at 10 min following IMP administration for calibration of the standard arterial input function. This calibration time was determined such that the integration of the first 40 min of the calibrated, combined input function agreed best with those from 12 individual input functions (the difference was 5.3% on average). This method was applied to eight subjects (two normals and six patients with cerebral infarction), and yielded rCBF values which agreed well with those obtained by a positron emission tomography H₂ ¹⁵O autoradiography method. This method was also found to provide rCBF values that were consistent with those obtained by the non-linear least squares fitting technique and those obtained by conventional microsphere model analysis. The optimum SPET scan times were found to be 40 and 180 min for the early and delayed scans, respectively. These scan times allow the use of a conventional rotating gamma camera for clinical purposes. V _d values ranged between 10 and 40 ml/g depending on the pathological condition, thereby suggesting the importance of measuring V _d for each ROI. In conclusion, optimization of the blood sampling time and the scanning time enabled quantitative measurement of rCBF with two SPET scans and one blood sample.     

A comparative study of simple methods to quantify cerebral blood flow with acetazolamide challenge by using iodine-123-IMP SPECT with one-point arterial sampling

The aim of this study was to compare the accuracy of simplified methods for quantifying rCBF with acetazolamide challenge by using 123I-N-isopropyl-p-iodoamphetamine (IMP) and SPECT with one-point arterial sampling. After acetazolamide administration we quantified rCBF in 12 subjects by the following three methods: (a) the modified microsphere method, (b) the IMP-autoradiographic (ARG) method based on a two-compartment one-parameter model, and (c) the simplified method based on a two-compartment two-parameter model (functional IMP method). The accuracy of these methods was validated by comparing rCBF values with those obtained by the standard method: the super-early microsphere method with continuous withdrawal of arterial blood. On analyzing rCBF in each flow range (0-0.25, 0.25-0.5, 0.5-0.75 and more than 0.75 ml/g/min), rCBF values obtained by both methods (a) and (c) showed significant correlations (p < 0.01) with those obtained by the standard method in every range, but rCBF values obtained by method (b) did not significantly correlated in the high flow range (0.5-0.75 and more than 0.75 ml/g/min). Method (c) was found to be the most accurate, even though it needs two serial SPECT scans. When requiring one SPECT scan, method (a) was considered to be superior to method (b) because of its accuracy, especially in high flow regions loaded with acetazolamide.     

Correct localization of epileptogenic focus with 1-123 iomazenil cerebral benzodiazepine receptor imaging: a case report of temporal lobe epilepsy with discordant ictal cerebral blood flow SPECT

A 26-year-old female with intractable epileptic seizures was studied with I-123 iomazenil cerebral benzodiazepine receptor, I-123 IMP inter-ictal and Tc-99m ECD ictal cerebral blood flow SPECT. The ictal cerebral blood flow SPECT indicated the location of the seizures to be in the left temporal lobe, where increased regional cerebral blood flow was noted in marked contrast to the inter-ictal SPECT. Ictal electroencephalograms (EEGs) recorded with scalp and sphenoidal electrodes also suggested the left temporal lobe as the location of the seizures. On I-123 iomazenil SPECT, however, decreased benzodiazepine receptor density was demonstrated in the right temporal lobe. MRI showed mild atrophy and abnormal signal intensity in the right temporal lobe. Ictal EEGs recorded with intracranial electrodes revealed that abnormal electrical activity of the brain always emerged from the right temporal lobe and then propagated to the contralateral side. Based on the findings of intracranial EEGs, partial resection of the right anterior temporal lobe including hippocampus was performed. After the surgery, no seizure occurred. Pathological examination of the surgical specimens revealed hippocampal sclerosis. This case suggested that cerebral benzodiazepine receptor imaging with I-123 iomazenil can be helpful for correct localization of epileptogenic foci.     

Changes in regional cerebral blood flow in irradiated regions and normal brain after stereotactic radiosurgery

OBJECTIVE: To elucidate the radiation effect on the normal brain after stereotactic radiosurgery (SRS), we evaluated the change in regional cerebral blood flow (CBF) in targeted and extra-targeted areas according to the radiation dose given. METHODS: Thirteen patients who underwent SRS for brain tumors or arteriovenous malformations were included in this study. Maximum radiation doses to the lesion ranged from 24 to 37 Gy. Mean and regional CBF were measured by 99mTc-HMPAO scintigraphy with graphic analysis, performed at before, 2 weeks and 3 months (5 patients) after SRS. Under the co-registration with the CT with superimposed isodose distribution, ROIs were set on target (37-20 Gy), peri-target (20-5 Gy) and out-of-field (5-2 Gy and less than 2 Gy) areas on the quantitative SPECT images. RESULTS: Significant reductions in mean CBF (by 7%) and regional CBF in the peri-target areas (by 5-7%) and out-of-field areas (by 6-22%) were recognized at 2 weeks and 3 months after SRS. Regional CBF in the target and peri-target areas did not significantly change, presumably because there was little or no normal tissue in these areas. CONCLUSION: These results suggest that subclinical regional CBF reduction occurs after SRS in the normal brain in out-of-field of radiation.     

A new method to estimate rCBF using IMP and SPECT without any blood sampling

We developed and evaluated a method to measure rCBF without any blood sampling by using iodine- 123 IMP and SPECT. An integral of arterial input function, the integral taken from the value 0 to T of the variable Ca(t)dt, can be expressed as TC(T)/CO, where TC(T) is radioactivity delivered to the body in T minutes and CO is cardiac output. If T is acceptably small, rCBF can be determined by means of a microsphere model analysis with IMP as Cb(T)/(TC(T)/CO), where Cb(T) is cerebral radioactivity at T minutes. We derived TC(T) and CO from a chest dynamic scan. The method was applied to 45 patients who underwent rCBF studies (58 studies) with arterial blood sampling (ABS). Data from the chest scan were analyzed in comparison with ABS data in the first 28 studies, and equations for correction yielding an accurate TC(T)/CO were derived. The validity of the proposed method was evaluated in the subsequent 30 studies. The method yielded rCBF (rCBF-test) which agreed well with rCBF obtained by a two-compartment model analysis of dynamic SPECT and ABS data (rCBF-ref) with the mean and SD of differences between rCBF-test and rCBF-ref being 1.0 and 2.7 ml/100 g/min, respectively. In eleven subjects who underwent more than two studies, a percentage change in rCBF-test between the studies also closely approximated that of rCBF-ref (y = 1.11 x + 2.63, r = 0.92). The method can be used with acceptable reliability to measure rCBF without any blood sampling.     

Evaluation of crossed cerebellar diaschisis in 30 patients with major cerebral artery occlusion by means of quantitative I-123 IMP SPECT

Quantitative crossed cerebellar diaschisis (CCD) and the correlation with a reduction in supratentorial regional cerebral blood flow (rCBF) and cerebrovascular reserve capacity (CVR) were investigated in clinically stable patients with major cerebral artery occlusion by the iodine-123-N-isopropyl-p-iodoamphetamine (I-123 IMP) single photon emission computed tomography (SPECT) method. Thirty patients with major cerebral artery occlusion underwent SPECT by the I-123 IMP autoradiographic method. Regional CBF was measured in the cerebral hemisphere, frontal and parietal lobes, temporo-parietal lobe, and cerebellum both at rest and after administration of acetazolamide. Eighteen of 30 patients (60%) had CCD. CCD was significantly related to magnetic resonance imaging evidence of infarction. Quantitative CCD was 17% and the CVR in the cerebellum was preserved in patients with CCD. There was a significant difference in CBF and CVR between the affected and normal sides in all regions of interest in the patients without CCD [CBF (ml/100 g/min): hemisphere (H), normal side (N): 31.4 +/- 6.8, affected side (A): 27.5 +/- 7.4; p < 0.05. CVR: H, N: 0.56 +/- 0.38, A: 0.42 +/- 0.18; p < 0.01]. CCD is common in patients with major cerebral artery occlusion, and quantitative I-123 IMP SPECT is helpful in detecting CCD in clinically stable patients with occlusion of major cerebral arteries.     

Semiquantifying regional cerebral blood flow by 123I-amphetamine (IMP) SPECT in cerebrovascular disorders: Correlations with CBF indices by 133Xe inhalation method

To examine the capacity of detecting regional cerebral blood flow (rCBF) disturbances in stroke, measurements with ¹³³Xe inhalation and ¹²³I-amphetamine (IMP) SPECT were performed within 1–2 days in 19 patients. IMP SPECT images in transverse sections consisting of outer and inner areas were correlated with 32 regions of ¹³³Xe rCBF. ¹³³Xe rCBF was assessed by ISI, CBF₁₅, and F₁. Inter hemispheric ratio correlation showed outer IMP uptake correlated better with ¹³³Xe CBF indices than the inner one. With higher ratios of ¹³³Xe rCBF, IMP uptake ratios were variable, suggesting less usefulness of this parameter in evaluation of mild ischemia. Values of IMP in outer regional hypo and hyperemic areas correlated better with those of ¹³³Xe rCBF than the inner ones. In regional ratios of hypo and hyperemic areas from hemispheric mean, outer IMP uptake correlated with ¹³³Xe CBF indices, reflecting regional disturbances of fast clearing tissue perfusion. Regression lines between ratios in ¹³³Xe CBF and IMP uptake were located below one to one correlation, and dissociated more for hyperemic regions. IMP SPECT correlated better with ¹³³Xe rCBF for tissues with reduced perfusion but underestimated hyperemic regions as measured with the ¹³³Xe method. The data suggest outer cerebral IMP uptake evaluated by SPECT could reflect flow disturbances in the brain cortex.This paper was presented in part at the XIIIth International Salzburg Conference on Cerebral Vascular Disease, on Sept. 25–27, 1986, in Salzburg, Austria, and at the XIIIth International Symposium on Cerebral Blood Flow and Metabolism, on June 21–25, 1987, in Montreal, CanadaRecipient of a Research Fellowship from the Alexander-von-Humboldt-Foundation, Federal Republic of Germany; Present address: Second Department of Internal Medicine, Kagawa Medical University, 1750-1 Ikenobe, Miki-cho, 761-07 Kagawa, Japan     

Evaluation of cerebral perfusion in patients with neuropsychiatric systemic lupus erythematosus using <Superscript>123</Superscript>I-IMP SPECT

Objective In the course of systemic lupus erythematosus (SLE), central nervous system (CNS) complications occur at a high frequency. An accurate diagnosis of CNS lupus, differentiated from secondary CNS involvement, is difficult. CNS lupus is indicative of advancing primary disease and is treated by steroid pulse therapy or increased dosage of steroids. In contrast, if symptoms are caused by secondary CNS complications, it is possible to observe or treat these complications using symptomatic therapy. We examined whether quantitative cerebral blood flow (CBF) measured using cerebral perfusion single photon emission computed tomography (SPECT) can be used to differentiate CNS lupus from secondary CNS involvement. Methods We divided 18 SLE patients with CNS symptoms into a CNS lupus group and a non-CNS lupus group, and then compared the mean cerebral blood flow (mCBF) of each group of patients. SPECT was performed with N-isopropyl-p-[¹²³I] iodoamphetamine (IMP), with quantitation carried out by table look-up and autoradiographic methods. Results The mCBF of both groups was decreased; however, the mCBF of patients with CNS lupus was significantly lower than that of non-CNS lupus patients. Conclusion Quantitative CBF may provide a useful tool to distinguish CNS lupus from non-CNS lupus.     

99mTc-MIBI pinhole SPECT in primary hyperparathyroidism: comparison with conventional SPECT, planar scintigraphy and ultrasonography

Purpose A pinhole collimator is routinely used to increase the resolution of scintigraphy. This prospective study was conducted to determine the interest of ^99mTc-MIBI pinhole single-photon emission computed tomography (SPECT) for the preoperative localisation of parathyroid lesions in primary hyperparathyroidism. Methods All patients underwent a neck ultrasonography (US), and ^99mTc-MIBI planar images and two consecutive SPECT with a parallel (C-SPECT) and a pinhole collimator (P-SPECT). P-SPECT was performed with a tilted detector equipped with a pinhole collimator and reconstructed with a dedicated OSEM algorithm. A diagnostic confidence score (CS) was assigned to each procedure considering intensity and extra-thyroidal location of suspected lesions: 0 = negative, 1 = doubtful, 2 = moderately positive, 3 = positive. The results of these preoperative localisation studies were compared with surgical, pathological and 6-month biological findings. Results Fifty-one patients cured after surgery were included. Surgery revealed 55 lesions (median weight 0.5 g, 11 in ectopy). Sensitivities of US, planar imaging, C-SPECT and P-SPECT were, respectively, 51, 76, 82 and 87%. Nine glands were only detected by tomography and five glands only by P-SPECT. planar scans and P-SPECT were complementary and, when combined together, showed the highest sensitivity (93%). Compared with planar imaging and C-SPECT, P-SPECT increased CS for 42 and 53% of lesions, respectively, and contributed to markedly reduce the number of uncertain results. Conclusions A combination of planar scintigraphy and P-SPECT appears to be a highly accurate preoperative imaging procedure in primary hyperparathyroidism.     

Regional cerebral blood flow measured with N-isopropyl-p-[123I]iodoamphetamine single-photon emission tomography in patients with Joseph disease

Regional cerebral blood flow (rCBF) was measured in five Japanese patients who were clinically diagnosed as having Joseph disease, also called Machado-Joseph disease or Azorean disease, using N-isopropyl p-[¹²³I]iodoamphetamine (IMP) and single-photon emission tomography (SPET). Cerebellar atrophy was evaluated by a five-step rating scale as defined on X-ray computed tomography (X-CT). Compared with ten age-matched normal controls (mean cerebellar CBF ± SD: 66.9 ± 6.6 ml/100 g/min), rCBF in patients with Joseph disease was significantly decreased in the cerebellum (mean ± SD: 50.2 ± 7.3 m1/100 g/min). No significant relationship, however, was found between the decrease in rCBF in the cerebellum and the degree of cerebellar atrophy on X-CT. rCBF in the cerebellum was minimally decreased in one patient who had severe cerebellar atrophy and in two patients with moderate atrophy. These data may support the findings that Purkinje cells in the cerebellum are almost normal in Joseph disease, and that the granular and molecular layers remain intact in spite of cortical atrophy of the cerebellum. It is concluded that [¹²³I]-IMP SPET is able to identify pathological and metabolic changes in the cerebellum that do not appear on X-CT or magnetic resonance imaging, and thus is useful for the diagnosis of Joseph disease. Correspondence to: N. Takahashi     

Regional cerebral blood flow in patients with sickle cell disease: study with single photon emission computed tomography

Objective Neurological complications have been reported in patients with sickle-cell disease (SCD) using positron emission tomography (PET), magnetic resonance imaging (MRI), and computed tomography (CT), but not with single photon emission computed tomography (SPECT). The objective of this study was to investigate brain perfusion in the patients with SCD using SPECT after technetium-99m hexamethylpropylene amine oxime (^99mTc-HMPAO), was administered and compare the findings with those of demography, physical examination, MRI and hematological profile. Methods The study involved 21 patients (12 males, 9 females, age at study 8–45 years) who were known to be having SCD for a duration of at least 5 years. The patients were not in acute crisis and had normal neurological assessments with no known history of stroke or transient ischemic episode or previous abnormal CT or MRI brain scan, and were right-handed. The brain SPECT was performed after intravenous injection of 740 MBq (20 mCi) ^99mTc-HMPAO in adults or an appropriate dose in pediatric patients. The scans were visually interpreted by two nuclear medicine physicians and a decision was reached by consensus. An MRI done 3 months later was interpreted by a radiologist. The demographic data and hematological profile were obtained from the medical records of the patients. Results Of the 21 patients, 7 (age 11–22 years) had brain perfusion deficit mostly in the frontal lobe either alone or in combination with temporal and/or parietal lobe. The MRI was abnormal in 2 patients. The brain perfusion deficit was not associated with the demographic data of the patients or hematological profiles. Conclusions The findings show that SPECT was useful in detecting brain perfusion deficit in SCD patients, and such an early detection may be clinically useful in the subsequent follow-up of such patients, since it is known that cerebral perfusion deficit can lead to silent infarct and/or overt stroke, and affect cognitive skills.     

Proposal of blood volume-corrected model for quantification of regional cerebral blood flow with H2 15O-PET and its application to AVF

Purpose It is generally assumed that vascular tracer activity is negligible in the quantification of regional cerebral blood flow (rCBF) with H₂¹⁵O and positron emission tomography (PET) under normal conditions. We attempted to surpass the assumption of abnormal vascular conditions where the vascular tracer activity is significant by introducing the vascular component into the model. Materials and methods H₂¹⁵O-dynamic and C¹⁵O PET scans were performed in an arteriovenous fistula (AVF) patient. Time–activity curves of regions of interest (ROIs) were analyzed with nonlinear least-square approximation to estimate the rCBF and fractional arterial blood volume (v_a) simultaneously with the proposed model and the standard model. Results The proposed model curve showed a fit to the time–activity curve of H₂¹⁵O at an ROI containing an enlarged vascular space induced by the AVF. The relation between the estimated v_a and CBV obtained with C¹⁵O-PET revealed that the ratio of v_a to CBV was approximately 0.23. The estimated rCBF with the proposed model in nonlesion ROIs corresponded to those of the standard model, with the estimated V_d 0.94 ml/ml. Conclusion The results supported the hypothesis that the blood volume-corrected model is applicable to the quantification of rCBF in a region with abnormal vascular structure. Furthermore, one of the advantages of the model is the feasibility of simultaneous estimation of the rCBF and arterial blood volume with dynamic-H₂¹⁵O PET scans.     

Semiquantitative assessment of regional cerebral perfusion using 99mTc HM-PAO and emission tomography

A method for the relative quantification of ^99mTc-HM-PAO distribution in brain SPECT is described. The method, applied in 12 normal volunteers and 150 patients suffering from different cerebral diseases, uses circumferential profiles to quantify the relative radionuclide distribution in the brain tomograms as an angular function with the origin at the center of the brain slice.Abnormal ^99mTc-HM-PAO distribution is evaluated by comparing the count content of symmetrical selected parts of the profile curve and comparing each patient's profile with the corresponding limits of normal ones, determined from the pooled profiles of 12 normal subjects.This computerized method allows an accurate, reproducible and objective assessment of the relative HM-PAO distribution in the brain.     

The preparation of 11C-labelled fluoromethane for the study of regional cerebral blood flow using positron emission tomography

Fluoromethane, previously labelled with ¹⁸F and used as a tracer in the measurement of regional cerebral blood flow, was ¹¹C-labelled by the reaction of ¹¹C-methyl iodide with tetraethylammonium fluoride. Sufficient quantities of radiotracer were prepared with a minimum amount of handling from 15 min target irradiations in the ¹⁴N(p, ) ¹¹C reaction. Total synthesis time was 25 min from end-of-bombardment, allowing serial blood flow measurements 30 min apart. The use of ¹¹C-fluoromethane as a cerebral blood flow tracer in positron emission tomography is discussed.     

SPECT局部脑血流显像在皮质下梗死伴半侧空间忽略患者的应用

目的　探讨皮质下梗死所致半侧空间忽略与脑血流改变部位、范围及程度间的关系。方法　对 30例临床确诊为单侧皮质下梗死的右利手患者行SPECT局部脑血流 (rCBF)显像 ,判定rCBF改变的部位、范围及程度。结果　经忽略组合试验证实有半侧空间忽略表现的 2 1例皮质下梗死患者 ,SPECT显像示rCBF降低部位多累及大脑皮质功能区 (χ2 =7 91,P <0 0 0 5 )。最多见于额叶 ,其次是顶叶、颞叶和枕叶。最明显的部位是颞顶枕交界处。病灶区rCBF及rCBF降低百分比与忽略评分的r分别为 - 0 4 4和 0 31。病灶的范围、数量与忽略程度间呈显著正相关 (r分别为 0 74和 0 72 )。结论皮层下梗死所致忽略多累及皮质功能区。多部位联合损伤易出现忽略且程度更严重。     

Noninvasive measurements of regional cerebral blood flow using technetium-99m hexamethylprophylene amine oxime

The previously reported method for quantitative measurements of whole-brain or hemispheric-brain perfusion using technetium-99m hexamethylpropylene amine oxime (HMPAO) radionuclide angiography is now further developed so that regional cerebral blood flow (rCBF) can be measured. Lassen's correction algorithm is used for the linearization of a curve-linear relationship between the radioactivity in the brain and blood flow as seen with single-photon emission tomography (SPET) images. In this algorithm, the cerebral hemisphere was chosen as the reference region and the correction factor was adapted to rCBF in the reference region. This new method of measuring CBF from SPET has been validated in 33 normal subjects and 22 patients with cerebrovascular disease. Regional CBF values in 20 brain regions of the normal subjects were in good agreement with reported values measured by other methods. Regional CBF in the frontal cortex was greater than that in the temporal, parietal or occipital cortex for the entire age range. This hyperfrontal perfusion tended to be less pronounced with advancing age. Seventeen patients with unilateral brain infarction showed significantly lower rCBF than normal subjects. The infarct core showed a low rCBF value of 11.1 ml/ 100 g/min on average. An increase in rCBF after acetazolamide administration was observed and mesured with this method in five patients with unilateral occlusive vascular pathology. These results suggest that this non-invasive method (without any blood sampling) permits the routine measurement of rCBF from HMPAO SPET tomograms of blood flow. Correspondence to: H. Matsuda     

学龄期癫(癎)患儿SPECT局部脑血流显像和认知功能的关系

目的探讨学龄期癫癎患儿 SPECT 局部脑血流(rCBF)显像的特征和认知功能状况及其关系。方法对32例学龄期原发性强直和(或)阵挛发作(GTCS)癫癎患儿进行 SPECT 脑显像及认知功能测试,两者进行相关性分析,并与12例正常儿童进行认知功能比较.结果①32例学龄期原发性癫癎患儿 SPECT 脑显像30例异常,定位率为93.8%,其中29例50个部位 rCBF 减少,rCBF 降低百分比为(21.07±7.09)%;1例2个部位 rCBF 增高,rCBF 增高百分比为(32.22±4.31)%,有92.3%的病灶集中在额、颞、顶、枕叶。②学龄期癫癎患儿言语智商(VIQ)、操作智商(PIQ)和总智商(FIQ)明显低于正常儿童,并存在一定的认知偏异,具有 VIQ>PIQ 倾向:③SPECT 脑显像检出癫癎患儿的病灶个数与认知测试 VIQ、PIQ 和 FIQ 呈负相关,相关系数分别为-0.543(P=0.002)、-0.469(P=0.009)、-0.578(P=.001);病灶范围与 VIQ、PIQ 和 FIQ 呈负相关,相关系数分别为-0.560(P=0.003)、-0.142(P=0.016)、-0.582(P=0.001);病灶区 rCBF 降低和增高百分比与认知测试各智商相关性不显著。结论 SPECT rCBF 显像对儿童原发性癫癎有较高的定位诊断价值;学龄期癫癎患儿存在不同程度的认知障碍,其认知功能减低与病灶的个数和范围呈负相关。