[Central type benzodiazepine receptor and cerebral blood flow in experimental chronic brain infarction--evaluation using a double-tracer autoradiography technique]

Double tracer autoradiography was performed to measure regional cerebral blood flow (rCBF) and the binding of central type benzodiazepine receptors (BZR) in infarction by means of permanent occlusion of the unilateral middle cerebral arteries (MCA) in rat. Iodine-125 Iomazenil and 99mTc-HMPAO was used to label BZR and rCBF respectively. In the chronic phase of infarction 21 to 28 days after occlusion (5 rats), rCBF in the left MCA territory was decreased to 62% of the sham control (4 rats), while BZR was more decreased to 45% of the control. In remote areas from the MCA lesion, the ipsilateral thalamus showed 28% decrease of BZR as compared to the control, though the decrease of rCBF was not significant. Iomazenil distribution may represent neuron density or BZR density on a neuron, since central type BZR is reported to be located on neurons. These results suggest that central type BZR imaging is more useful tool for the evaluation of brain tissue viability and transneuronal degeneration than rCBF imaging in brain infarction.

[Quantitative analysis of brain perfusion using radionuclide angiography with 99mTc-HMPAO]

A noninvasive simple method for quantitative radionuclide angiography with 99mTc-dl-hexamethyl propylene amine oxime (99mTc-HMPAO). The method of graphical analysis was employed for the evaluation of the unidirectional influx constant (Ku) from the blood to the brain for the tracer. The Ku values were standardized to represent objective and comparable values, brain perfusion indices (BPI), among studied subjects by setting the ratio of ROIbrain size to ROIaorta size to 10. The mean +/- SD of the whole-brain BPI values for the 41 normal controls was 11.15 +/- 2.61, and biphasic reduction with advancing age was observed. The mean of the whole-brain BPI of 7.95 with SD of 2.35 in 103 patients with cerebrovascular disorders was significantly lower than that in normal controls. The right to left ratio of BPI showed wider dynamic range than that of the total counts of SPECT. This technique is quite easy to apply as an adjunct to SPECT and may be helpful in the quantitative evaluation of brain perfusion in routine clinical studies.

Noninvasive measurements of regional cerebral blood flow using technetium-99m hexamethylpropylene 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 alpha 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 measured 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.

123I-labelled BMIPP fatty acid myocardial scintigraphy in patients with hypertropic cardiomyopathy: SPECT comparison with stress 201Tl

123I-labelled 15-(p-iodophenyl)-3-(R,S)-methylpentadecanoic acid (BMIPP) myocardial single photon emission computed tomography (SPECT) was performed in 17 patients with hypertrophic cardiomyopathy, and was compared with 201Tl exercise stress myocardial perfusion SPECT images. Fourteen patients showed asymmetrical hypertrophy, and three demonstrated apical hypertrophy. SPECT was performed 20 min and 3 h after injection of 111 MBq 123I-BMIPP at rest. Exercise stress 201Tl SPECT was performed at 10 min and 3 h after injection and was compared with BMIPP imaging. In 13 patients BMIPP accumulation in the hypertrophied area in the 20 min image was lower than that of 3 h 201Tl uptake. Interestingly, six patients demonstrated 201Tl redistribution in the region where the uncoupling of BMIPP uptake at 20 min and 201Tl accumulation at 3 h after exercise was observed. These findings suggest that impaired fatty acid metabolism or utilization in hypertrophic myocardium and ischaemia or impaired coronary flow reserve may be one of the causes of the abnormality of fatty acid accumulation.

Quantitative assessment of regional cerebral blood flow with 123I-IMP in normal adult subjects

Quantitative assessment of regional cerebral blood flow (rCBF) in the bilateral cerebral and cerebellar cortices was performed in 22 normal adult subjects consisting of an early twenties group (5 men and 9 women, 20-22 years) and middle age group (3 men and 5 women, 41-52 years), using single photon emission computed tomography (SPECT) with N-isopropyl-(iodine 123) p-iodoamphetamine. Absolute rCBF values in each region in the 22 subjects ranged from 46 to 102 ml/100 g/min (mean 69.1, standard deviation 13.7 ml/100 g/min). The absolute rCBF values were significantly higher in women than in men, and in the early twenties group than in the middle age group. In addition, based on each absolute rCBF value, the interhemispheric asymmetry, anterior to posterior ratio and cerebellar to frontal ratio in rCBF were calculated. These results may be useful as indexes for detecting organic and functional brain abnormalities in various neuropsychiatric diseases.

Probable cerebellar abnormality on 123I-IMP SPECT scans in epileptic patients with long-term high-dose phenytoin therapy. Based on observation of multiple cases

Quantitative assessment of regional cerebral blood flow (rCBF) in the bilateral cerebral and cerebellar cortices was performed in 13 epileptic patients receiving long-term high-dose phenytoin (PHT) therapy, using single photon emission computed tomography (SPECT) with N-isopropyl-(iodine 123) p-iodoamphetamine. In 4 of the 13 patients, both the cerebellar to frontal rCBF ratio and cerebellar to cerebral rCBF ratio showed low values as compared with those in 22 normal subjects matched for sex and age, probably reflecting abnormal relative cerebellar hypoperfusion. None of the 4 patients showed any abnormal findings on X-ray computed tomography or magnetic resonance brain imaging. The patients with a history of acute PHT intoxication tended to show the abnormal relative cerebellar hypoperfusion. These results suggest the utility of SPECT scans for early detection of cerebellar abnormalities known to be often present in epileptic patients, and imply a risk of long-term high-dose PHT therapy.

Efficacy of sulthiame (Ospolot) on motor partial seizure status during sleep in a patient with motor cortex epilepsy

An 18-year-old female patient with a particular form of intractable motor cortex epilepsy, in which motor partial seizure status occurred only during sleep every night, was reported focusing on the drastic efficacy of sulthiame on the seizure status. Moreover, the present study demonstrated that single photon emission computed tomography (SPECT) and pulse oximetry examinations, both of which were performed in the ictal state, were useful for the regional diagnosis of the epileptic focus and observations of the seizure frequency, respectively. The therapeutic effect, epileptic picture and clinical examinations described here appear to be relatively rare in the literature, and therefore, this case report may be of clinical significance.

High resolution Tc-99m HMPAO SPECT in a patient with transient global amnesia

This is a report of a patient who underwent high-resolution brain perfusion SPECT studies during and after an episode of transient global amnesia. During the attack, SPECT imaging showed increased perfusion in the left medial temporal region involving the amygdala and hippocampus. After recovery from amnesia, a follow-up SPECT examination showed slightly decreased perfusion in this region. These findings support the hypothesis that transient global amnesia is associated with transient hyperperfusion in the medial temporal brain structures, and confirm the utility of high-resolution SPECT imaging for the evaluation of the fine details of functional brain anatomy.

Visualization of the thymus with therapeutic doses of radioiodine in patients with thyroid cancer

Two cases of papillary carcinoma of the thyroid are presented in which whole-body scans following therapeutic doses of iodine-131 revealed intense anterior mediastinal uptake. In both cases, the mediastinal uptake was absent from scans obtained after removal of the entire thymus. Histologically, the resected thymus glands showed hyperplasia and contained neither thyroid tissue nor metastatic foci of thyroid carcinoma. We therefore concluded that anterior mediastinal uptake of radioiodine may be caused by hyperplasia of the thymus.

Diffuse cerebral hypoperfusion in epileptic patients observed from quantitative assessment with single photon emission computed tomography using N-isopropyl-(iodine-123)-p-iodoamphetamine

Quantitative assessment of regional cerebral blood flow (rCBF) in the bilateral cerebral and cerebellar cortices was performed in 15 epileptic adult patients receiving chronic high-dose antiepileptic drug therapy and 22 normal volunteers matched for sex and age, using single photon emission computed tomography with N-isopropyl-(iodine-123)-p-iodoamphetamine. The entire averaged rCBF value in the epileptic patients, i.e. 52.8 +/- 13.7 ml/10 g/min (range: 25-78 ml/100 g/min), was significantly lower as compared with that in the normal subjects, i.e. 69.1 +/- 14.2 ml/100 g/min (range: 46-102 ml/100 g/min). Six of the 15 patients showed absolute rCBF values less than the minimum of the normal range, i.e. 46 ml/100 g/min, in all or most of the measured brain tissues. There was a significant correlation between the diffuse cerebral hypoperfusion and simultaneous ingestion of phenytoin and phenobarbital. The possible effects of antiepileptic drugs on rCBF are discussed.

Probable cerebellar abnormality on N-isopropyl-(iodine-123)-p-iodoamphetamine single photon emission computed tomography scans in an epileptic patient receiving long-term high-dose phenytoin therapy

Quantitative assessment of regional cerebral blood flow (rCBF) was performed in a 22-year-old man with intractable temporal lobe epilepsy on long-term high-dose phenytoin (PHT) therapy, using single photon emission computed tomography (SPECT) with N-isopropyl-(iodine-123)-p-iodoamphetamine. In all the SPECT scans repeated three times with changes in the PHT dose, absolute rCBF values were lower in most of the cerebral and cerebellar regions measured, as compared with 5 normal subjects matched for sex and age, and 22 normal subjects including the 5 men. Both the cerebellar to frontal rCBF ratio and cerebellar to cerebral rCBF ratio in the patient persistently showed low values, probably reflecting abnormal relative cerebellar hypoperfusion, whereas X-ray computed tomography and magnetic resonance brain imaging showed no abnormal findings. However, this probable cerebellar abnormality on SPECT was to some degree reversible with decreases in the PHT dose. These results suggest the utility of SPECT scans for early detection of cerebellar abnormalities known to be often present in epileptic patients, and imply a risk of long-term high-dose PHT therapy.

[Assessment of congenital heart disease by a thallium-201 SPECT study in children: accuracy of estimated right to left ventricular pressure ratio]

The characteristics of correlation between the right-to-left ventricular systolic pressure ratios (RVp/LVp) and the thallium-201 right-to-left ventricular (201Tl R/L) count ratios was investigated in children with various congenital heart diseases. High-resolution three-headed SPECT system equipped with either parallel-hole or fan-beam collimators was used. In a total of 102 patients, the correlation between RVp/LVp and 201Tl R/L average count ratios was good in both planar (r = 0.89, p = 0.0001) and SPECT studies (r = 0.80, p = 0.0001). Quantitative analysis of myocardial uptake by SPECT demonstrated the characteristic pattern of each disease as well as the differences in the right ventricular overload types. When the linear regression analysis was performed in each heart disease, ventricular septal defect showed most excellent correlation. Complex heart anomalies also showed positive correlation (r = 0.51, p = 0.05) with RVp/LVp, and it can be used to estimate right ventricular pressure. After surgical treatment of tetralogy of Fallot and pulmonary stenosis, the decrease of 201Tl R/L count ratio was in accordance with improvement of right ventricular overload. We conclude that 201Tl SPECT study can be a good indicator for estimation of right ventricular pressure.

Tc-99m HMPAO-labeled leukocytes for hematopoietic marrow imaging. Comparison with In-111 chloride

The current study was initiated to define whether Tc-99m leukocyte imaging, compared to In-111 chloride imaging, could provide additional information on the hematopoietic activity of the bone marrow in diffuse hematologic disorders. A total of 11 patients with hematologic disorders were studied both with Tc-99m leukocytes and In-111 chloride. One patient with myelofibrosis showed disparate tracer distribution in the bone marrow between the two; Tc-99m leukocyte uptake in the central marrow was highly decreased, whereas In-111 chloride showed expanded marrow. The disparate results of granuloid hypoplasia and erythroid hyperplasia obtained by bone marrow biopsy and aspiration in this patient were thought to give an explanation for the radionuclide findings. The remaining 10 patients showed similar tracer distribution in the marrow, and the observation of hematopoietic cellularity confirmed by bone marrow biopsy and aspiration correlated well with the radionuclide findings. These results demonstrate that Tc-99m leukocytes may be a potential imaging agent for evaluating hematopoietic activity in the bone marrow, in particular granulopoietic activity.

An autonomously functioning thyroid carcinoma associated with euthyroid Graves' disease

A 39-yr-old man with an autonomously functioning thyroid carcinoma is presented. Only 17 similar cases have been reported in the literature. The patient had unilateral Graves' ophthalmopathy. He was euthyroid as reflected by normal TSH concentration, whereas the results of a T3 suppression test established the presence of autonomous thyroid function. A thyroid scan with (123)I revealed a hot nodule corresponding to the location of a papillary carcinoma and remained substantially unchanged after T3 administration. The hyperfunction of the carcinoma itself was clearly confirmed by the intense concentration of (131)I within the tumor on microautoradiograms. While a hot nodule on radioiodine scan is unlikely to be malignant, the possibility of carcinoma should not be overlooked.

Discordant hepatic uptake of Tc-99m NGA and Tc-99m PMT in a patient with hepatoma

The authors report discordant hepatic uptake of Tc-99m NGA and Tc-99m PMT in a patient with hepatoma. Tc-99m PMT uptake was delayed and Tc-99m NGA concentrated in another area, thereby demonstrating that the uptake mechanisms for Tc-99m NGA and Tc-99m PMT are different. Tc-99m NGA imaging may be useful in characterizing the focal hepatic lesion of Tc-99m IDA or Tc-99m PMT concentration.

Acute subendocardial infarction with diffuse intense Tc-99m PYP uptake and minimal Tl-201 abnormality

Tc-99m PYP scintigraphy performed on a patient with severe anterior chest pain showed diffuse intense uptake with central decreased activity corresponding to the left ventricular cavity. Tl-201 myocardial perfusion scintigraphy at rest revealed a minimal perfusion abnormality with decreased apical uptake in the lateral view. Because of these findings, diffuse subendocardial infarction was suggested.

High-resolution cardiac SPET study using fanbeam collimators in infants

High-resolution three-headed single photon emission computed tomography (SPET) equipped with fan-beam collimators was applied to myocardial perfusion imaging in infants aged from 1 to 11 months (n = 5). A tabletop designed specifically for infants was fixed on the SPET couch to reduce the radius of camera rotation to 13.2 cm. Significant improvement in resolution was achieved with the fan-beam collimators compared to parallel-hole high-resolution collimators. With the administration of approximately 37 MBq (26-44 MBq) 201Tl, 5 min acquisition time was possible for SPET imaging, which provided good image quality in all patients. Thus, a smaller administration dose is possible within a practical short acquisition time. High-resolution fan-beam SPET imaging can be a routine diagnostic method for heart disease in newborn babies and infants.

Acetazolamide effect on vascular response in areas with diaschisis as measured by Tc-99m HMPAO brain SPECT

The effects of acetazolamide (Diamox) on vascular response were investigated in areas with intrahemispheric thalamic diaschisis and crossed cerebellar diaschisis using consecutive Tc-99m HMPAO brain SPECT studies before and after Diamox administration. All six patients with thalamic diaschisis and five of eight patients with crossed cerebellar diaschisis at baseline showed significantly augmented perfusion after Diamox administration in the affected thalamus and cerebellum compared with that in the contralateral unaffected areas. These results suggest more dilatation of the arterioles in areas with diaschisis after Diamox administration than in areas without diaschisis. Diamox may produce relative luxury perfusion in areas with diaschisis.

[Evaluation of the internal mammary nodes by lymphoscintigraphy and ultrasonography in patients with breast cancer]

The efficacy of lymphoscintigraphy and ultrasonography was evaluated in the detection of internal mammary lymph node (IMN) metastases in patients with breast cancer. On histological examination of IMN, 10 patients had metastases (positive group) and 47 did not (negative group). On lymphoscintigraphy, lack of uptake in the parasternal region of the affected side was classified as abnormal. The frequency of this abnormal finding was not significantly different between both groups. On sonography, the thickness of the sonolucent internal mammary area was measured. The thickness of the affected side was 6 mm or more in two patients of the positive group and only one of the negative group. A thickness of over 6 mm on the affected side was statistically significant (p less than 0.05). The difference in thickness between the affected side and the healthy side was 3 mm or more in four patients of the positive group, and was less than 3 mm in all patients of the negative group. A difference in thickness of more than 3 mm between the two sides was extremely significant (p less than 0.001). In conclusion, sonography is valuable in detecting IMN metastases, while lymphoscintigraphy is not useful. Sonography is recommended as an efficient diagnostic modality for IMN metastases.

A simulation of dynamic SPECT using radiopharmaceuticals with rapid clearance

Data acquisition in SPECT assumes that there is no change in radionuclide distribution during data collection. However, this assumption is not valid in radiopharmaceuticals with rapid temporal changes in radioactivity. Artifacts and quantitative errors are studied using phantom studies, mathematical models, and clinical myocardial data. Projection data of each model were sequentially multiplied by weighting coefficients that varied mono-exponentially with time, and the SPECT images were reconstructed. A long data acquisition time in comparison to the clearance of the tracer can be a significant cause of artifact. When the myocardial septum-to-lateral count ratio is used as an index of distortion, a shorter acquisition time than the effective half-life of the tracer is required to reduce the error of the septum-to-lateral count ratio to within 10%. Since 180 degrees rotation acquisition causes artifacts depending on the direction of rotation, 360 degrees acquisition is preferable. Continuous repetitive rotation acquisition is a suitable method for dynamic SPECT to reduce quantitative errors and artifacts.

[The utility of quantitative 99mTc-GSA liver scintigraphy in the evaluation of hepatic functional reserve: comparison with 99mTc-PMT and 99mTc-Sn colloid]

Using data from 17 patients with liver cirrhosis and 3 patients with fatty liver, we have compared the utility of 3 hepatic imaging agents in the evaluation of hepatic functional reserve. Evaluated here were 99mTc-galactosyl human serum albumin (GSA) which is a new ligand for hepatic binding protein, 99mTc-N-pyridoxyl-5-methyl tryptophan (PMT) of a hepatobiliary agent, and 99mTc-Sn colloid. In each patient, we performed these 3 imaging studies within a week and also examined hepatic function tests (indocyanine green test, hepaplastin test, choline-esterase, etc). In each imaging study, serial images and dynamic data were obtained after the injection of 99mTc-GSA (185 MBq/3 mg), 99mTc-PMT (185 MBq), or 99mTc-Sn colloid (185 MBq). Using the obtained dynamic data, we analyzed the liver kinetics of the 3 agents based on 1 compartment model with 3 parameters (hepatic clearance, hepatic excretion rate, non-specific volume of distribution). From fitting the liver and heart data to this model, three unknown parameters were determined. Patlak plot was also applied in order to estimate liver uptake rate. Both curve fitting and Patlak plot could determine appropriate parameters in every study. In 99mTc-GSA, a nonlinear 3 compartment model was also applied in order to estimate hepatic blood flow, liver receptor density, and affinity of receptor-GSA binding separately. Using the obtained parameters, we analyzed the correlations between the parameters and the results of hepatic function tests. In all of the parameters, those obtained from 99mTc-GSA imaging showed the most significant statistical correlation with the results of hepatic function tests. From the present results, 99mTc-GSA imaging was concluded to be the best for evaluation of hepatic functional reserve.

Esophageal clearance scintigraphy, in diabetic patients--a preliminary study

The aim of this preliminary study was to evaluate the predictive value of esophageal clearance scintigraphy (ECS) in the diagnosis of esophageal autonomic neuropathy in diabetic patients without any esophageal symptoms. A single swallow ECS was performed in 12 diabetic patients and 15 normal volunteers, and esophageal transit time (ETT) and esophageal (Es) T 1/2 values were calculated. ETT and Es T 1/2 were found to be significantly prolonged in the diabetic group (p less than 0.01 and p less than 0.05, respectively). In this preliminary study, our results strongly suggest that ECS may be an important noninvasive diagnostic tool in the evaluation of diabetic patients with asymptomatic esophageal autonomic neuropathy.

Technetium-99m p-iodophenethyldiaminodithiol (DADT-IPE): potential brain perfusion imaging agent for SPECT

A new ligand, an N-p-iodophenethyl diaminodithiol (DADT-IPE), an anlog of N-isopropyl-p-iodoamphetamine (IMP), was synthesized and subsequently complexed with 99mTc, using stannous chloride as a reducing agent. Two complexes (a and b) were separated from 99mTc-DADT-IPE by high performance liquid chromatography (HPLC). Competitive inhibition studies showed that the IC50 value of DADT-IPE (70 microM) was similar to that of IMP (49 microM). Biodistribution studies of one of the complexes [99mTc-DADT-IPE(a)] in rats showed that 0.65% of the injected dose of the tracer remained in the brain at 5 min after intravenous injection, with 0.53% of the dose remaining in the brain at 60 min post-injection, whereas the corresponding values for the other complex [99mTc-DADT-IPE(b)] were 0.34% dose in the brain at 5 min and 0.28% dose in the brain at 60 min post-injection. The half-life for clearance of 99mTc-DADT-IPE(a) from rat brain was found to be more than 5 h. These results suggested that 99mTc-DADT-IPE(a) has characteristics which are suitable for cerebral perfusion imaging.

[Myocardial perfusion and clearance of 99mTc teboroxime assessed by SPECT]

99mTc teboroxime is a new myocardial imaging agent that has characteristics of high accumulation in the heart and rapid clearance. We performed tomographic teboroxime study and compared the findings with that of 201Tl. Myocardial teboroxime clearance was calculated by dynamic single photon emission computed tomography (SPECT) using continuous repetitive rotation acquisition method. Teboroxime SPECT image was reconstructed by the three-minute data started from 4 minutes after injection. In 45 myocardial regions (15 patients), complete agreement between 201Tl and 99mTc teboroxime was obtained in 33 regions (73%), when the findings were classified as normal, ischemia and infarction. Significant delay in clearance was seen in the region of coronary stenosis (greater than or equal to 75%) compared with that in the control region (p = 0.0087 at rest, and p = 0.0385 at peak exercise by paired T test). Septum-to-lateral ratios of the clearance and myocardial initial count showed positive correlation (r = 0.743). Further clinical application of this radiopharmaceutical is expected as a new myocardial imaging agent.