Favorable biodistribution of99mTc-ECD for brain SPECT comparing with123I-IMP using alternative body scan

In order to evaluate the lung and brain uptake of 99mTc ethyl cysteinate dimer (99mTc-ECD) and N-isopropyl-p-[123I]-iodoamphetamine (123I-IMP), alternative body scans were carried out in 15 cases of cerebrovascular disease. The biodistribution of 99mTc-ECD was 5.5 +/- 0.7%, 3.8 +/- 0.7% in the brain; 13.1 +/- 3.7%, 2.2 +/- 1.2%, in the lung at 15 min and at 4 hours, respectively, whereas that of 123I-IMP was 3.9 +/- 1.4%, 5.0 +/- 1.0% in the brain; 32.2 +/- 7.6%, 12.7 +/- 3.3%, in the lung at 15 min and at 4 hours, respectively. 99mTc-ECD accumulated in comparatively high amounts in the brain but remained low in the lung in the early image compared to 123I-IMP. However there was a high inverse correlation between brain and lung uptake of 123I-IMP (r = -0.82), but not of 99mTc-ECD (r = -0.18). We concluded that 99mTc-ECD had a better biodistribution in terms of low lung accumulation than 123I-IMP in brain SPECT.     

Single photon emission computed tomography (SPECT) using 99mTc-hexamethyl propyleneamine oxime in patients with ischemic cerebral diseases: comparative study of N-isopropyl-p-[123I]-iodoamphetamine and 99mTc-DTPA SPECT

In order to confirm the diagnosis and clarify the pathophysiology in the ischemic lesions in brain, 99mTc-PAO SPECT was performed in 42 patients with ischemic cerebral diseases, and the findings on 99mTc-PAO SPECT were compared with those on 123I-IMP or 99mTc-DTPA SPECT, and on X-CT. Furthermore, count ratio of ischemic lesion to normal contralateral region (I/N) was used for the evaluation of the detectability in the lesions on 99mTc-PAO or 123I-IMP SPECT, and less than 0.95 of I/N ratio was defined as the decreased accumulation. The detectability of ischemic lesion in brain with 99mTc-PAO SPECT was 80%, which was superior to that (60%) of LDA on X-CT. Especially, 99mTc-PAO SPECT was useful in cases which were examined early after the onset of the attack. On the other hand, 123I-IMP SPECT showed the best result (88%) in the detectability, and furthermore I/N ratio on 123I-IMP SPECT was lower than that on 99mTc-PAO SPECT. In the delayed phase on 123I-IMP SPECT the redistribution was observed in 30%, while on 99mTc-PAO SPECT it was done in none of them. The accumulation of 99mTc-DTPA in brain was found in 6 of 14 cases (43%), and 2 cases among them also showed the accumulation of 99mTc-PAO in the ischemic lesion. In such cases the destruction of BBB might be considered as the cause of the accumulation of 99mTc-PAO. Thus, 99mTc-PAO SPECT was thought to be useful method in clinical studies of the ischemic cerebral diseases.     

Usefulness of 99mTc-ECD SPECT in diseases of the central nerve system: special reference to a comparison with 123I-IMP and 99mTc-HM-PAO SPECT]

The usefulness of a new cerebral perfusion imaging radiopharmaceutical, 99mTc-ethyl cysteinate dimer (ECD), was clinically evaluated. The subjects of this study were 14 patients with neurological disorders including 10 patients with cerebral infarction and 4 patients with other diseases. A total of 15 examinations was performed. 99mTc-HM-PAO or 123I-IMP SPECTs were performed simultaneously, and the findings from those examinations were compared with 99mTc-ECD. As to the count ratio of lesions to normal area (L/N), the L/N ratio in severe ischemic patients was lower in 99mTc-ECD than in 99mTc-HM-PAO or 123I-IMP. In mild ischemic patients, on the other hand, the L/N ratio was the lowest in 123I-IMP. When the relationship between rCBFs obtained from 123I-IMP and the values of L/N in 99mTc-ECD or 99mTc-HM-PAO was compared, the values of L/N in 99mTc-ECD or 99mTc-HM-PAO were found to have decreased linearity with increasing rCBF. In a patient showing luxury perfusion, the accumulation pattern of 99mTc-ECD was different from that of the other two radiopharmaceuticals, and focal defect was revealed in 99mTc-ECD SPECT. On the dynamic SPECT of 99mTc-ECD in a patient with meningioma, the tumor showed a change from high to low perfusion with the passage of time. This finding indicated that care should be taken in the evaluation of accumulation of 99mTc-ECD. Therefore, 99mTc-ECD was found to be useful as a cerebral perfusion agent. In addition, as accumulation of 99mTc-ECD might somehow reflect metabolism in some cases, further careful investigation of many cases should be carried out.     

"Luxury perfusion" with 99mTc-HMPAO and 123I-IMP SPECT imaging during the subacute phase of stroke

To compare the merits of 123I-isopropyl-iodoamphetamine (123I-IMP) and 99mTc-HMPAO in showing abnormal brain uptake distribution during cerebral ischemia, we studied ten patients during the subacute phase of their stroke, a period where metabolism and blood flow are frequently uncoupled. SPECT imaging was performed using both radiopharmaceuticals in the 10 patients from 48 h to 4 weeks after onset of symptoms. Two patients out of the 10 had similar defects with 123I-IMP and 99mTc-HMPAO SPECT, the location of the defects corresponding to the area of infarction observed on CT. Six patients had normal 99mTc-HMPAO SPECT and abnormal 123I-IMP SPECT with defects in the area of infarction shown by CT. The remaining 2 patients had hyperactive abnormalities on 99mTc-HMPAO in areas corresponding to defects on the 123I-IMP images. Two of the patients with SPECT mismatches were studied again more than 1 month after onset. On reexamination, 99mTc-HMPAO SPECT which was previously normal or hyperactive became hypoactive with a focal area of decreased activity corresponding to the defect on 123I-IMP. Crossed cerebellar diaschisis was found in 7 patients with 99mTc-HMPAO and was absent for both 123I-IMP and 99mTc-HMPAO in 3. We suggest that SPECT with 99mTc-HMPAO could show transient hyperemia not demonstrated by 123I-IMP whereas in some cases cerebral infarction would be more difficult to demonstrate with 99mTc-HMPAO than with 123I-IMP. SPECT with both tracers is recommended to follow the evolution of strokes in terms of regional cerebral blood flow and tissue metabolism.     

SPECT images after intravenous injection of 99mTc-DTPA in lung tumors--comparison with delayed 123I-IMP lung scintigraphy

The aim of this study was to assess the efficacy of SPECT imaging of the thorax with 99mTc-DTPA, which accumulates at sites of increased capillary permeability and expanded extracellular space, by comparing it with delayed 123I-IMP lung scintigraphy. We have previously reported that increased uptake on delayed 123I-IMP lung scintigraphy was associated with atelectasis and inflammation. Thirteen patients with lung cancer (4 with atelectasis and 3 with pleurisy), one patient with malignant lymphoma complicated by pneumonia and pleurisy, and one patient with pneumonia were studied. 99mTc-DTPA scintigraphy was performed twice, 20-160 minutes and 2-4 hours after the intravenous administration of 370 MBq of 99mTc-DTPA. 123I-IMP scintigraphy was performed 24 hours after the intravenous injection of 111 MBq of 123I-IMP. SPECT images were obtained with both types of scintigraphy. 99mTc-DTPA scintigraphy was compared with 123I-IMP scintigraphy for its ability to detect atelectasis and pneumonia. All patients showed increased accumulation corresponding to the lesions on both 123I-IMP and 99mTc-DTPA scintigraphy. 123I-IMP scintigraphy showed a defect corresponding to the tumor with increased accumulation around the tumor, whereas 99mTc-DTPA scintigraphy showed accumulation corresponding to the tumor. Ten of 11 tumors showed accumulation of an intensity equal to that of the soft tissue of the chest wall on 20-60 min 99mTc-DTPA images. The 2-4 hr images showed that 99mTc-DTPA leaked from the periphery of the tumor toward its center. All the patients with pleurisy showed increased accumulation in effusion on 2-4 hr 99mTc-DTPA scintigraphy.(ABSTRACT TRUNCATED AT 250 WORDS)     

Development of a simple method for the washout correction of 123I-IMP SPECT and its application to a quantitative rCBF method

We have developed a simple method to correct the washout of tracer from the brain based on the two-compartment model in brain early SPECT using N-isopropyl-p-[123I]iodoamphetamine (123I-IMP). This correction was applied to a new quantitative method of regional cerebral blood flow (rCBF) in combination with the microsphere method by continuous arterial sampling previously reported. Data acquisition of 123I-IMP early SPECT was started from 35 min after 123I-IMP i.v. injection, and the time activity curve of whole brain on anterior head planar images was monitored immediately after 123I-IMP i.v. injection for the correction of washout of tracer from the brain. The usefulness of this method was evaluated in 12 patients with various brain diseases by comparison with the results obtained from the super-early SPECT at 7-10 min after 123I-IMP i.v. injection. The washout rates in cases of early SPECT corrected by this method ranged from 16.91% to 39.34% with a mean +/- SD of 27.72 +/- 5.44%. The contrast of hypo- to hyperperfusion regions on early SPECT was improved by the correction of the washout, and its intracerebral distribution was similar to the simultaneously obtained super-early SPECT images. These results indicated that the present correction method for the washout was useful for more correct quantification of rCBF.     

Brain single-photon emission CT studies using 99mTc-HMPAO and 99mTc-ECD early after recanalization by local intraarterial thrombolysis in patients with acute embolic middle cerebral artery occlusion

BACKGROUND AND PURPOSE: The brain distribution of 9mTc-hexamethylpropyleneamine oxime (HMPAO) correlates with regional brain perfusion, whereas 99mTc-ethyl cysteinate dimer (ECD) reflects not only perfusion but also the metabolic status of brain tissue. We compared 99mTc-ECD single-photon emission CT (SPECT) with 99mTc-HMPAO SPECT early after recanalization by local intraarterial thrombolysis (LIT) in patients with acute embolic middle cerebral artery occlusion. We also assessed the predictive value of 99mTc-HMPAO and 99mTc-ECD SPECT for the development of ischemic brain damage. METHODS: 99mTc-HMPAO and consecutive 99mTc-ECD SPECT studies were performed in 15 patients within 3 hours of LIT. The two SPECT studies were obtained independently using a subtraction technique. SPECT evaluation was performed using semiquantitative region-of-interest analysis. Noninfarction, infarction, and hemorrhage were identified by follow-up CT or MR imaging. RESULTS: Forty-five lesions were identified (21 noninfarctions, 19 infarctions, and five hemorrhages). Regardless of 99mTc-HMPAO SPECT findings, lesions showing isoactivity (count rate densities of 0.9 to 1.1 as compared with the contralateral side) on 99mTc-ECD SPECT were salvaged. Lesions with hypoactivity (values < 0.9) on 99mTc-ECD SPECT developed irreversible brain damage. Hemorrhage appeared in lesions with both hyperactivity (values > 1.1) on 99mTc-HMPAO SPECT and hypoactivity on 99mTc-ECD SPECT. CONCLUSION: The brain distribution of 99mTc-ECD in a reperfused area identified by 99mTc-HMPAO SPECT early after recanalization of acute ischemic stroke is dependent on cerebral tissue viability. By combining 99mTc-ECD and 99mTc-HMPAO SPECT, performed within the first few hours of LIT, it is possible to identify patients at risk for hemorrhagic transformation reliably.     

The diagnostic value of 123I-IMP SPECT in non-Hodgkin's lymphoma of the central nervous system.

N-isopropyl-p-[123I]iodoamphetamine (IMP) SPECT is of low diagnostic value in patients with brain tumors, because brain tumors are visualized as uptake defects. Some reports have described non-Hodgkin's lymphoma of the central nervous system (CNS) as showing high uptake on delayed 123I-IMP SPECT images, suggesting its usefulness in diagnosing CNS lymphoma. In this study, we investigated the clinical value of 123I-IMP SPECT as a diagnostic tool for CNS lymphoma. METHODS: Ninety-six patients with brain tumors, including 12 patients with CNS lymphoma, underwent 123I-IMP SPECT. Eleven patients had primary CNS lymphoma, and 1 had a parenchymal brain metastasis from a breast lymphoma. The total number of lesions was 18, 14 of which were in the cerebral parenchyma, 3 in the brain stem, and 1 in the ventricle. Early SPECT images were initiated 15-30 min after intravenous injection of 111 MBq 123I-IMP, and delayed images were collected 4 h later. SPECT images were visually analyzed with a color-grading scale. Tumor-to-normal activity ratio (T/N) and tumor-to-cerebellum activity ratio (T/C) were calculated for both early and delayed images for semiquantitative analysis. RESULTS: By visual estimation, more than a 3-cm3 volume of CNS lymphoma was detected as an obvious focus of increased accumulation on delayed images. All other brain tumors tested appeared as decreased accumulation on delayed images. T/Ns and T/Cs on delayed images of CNS lymphomas, including tumors less than 3 cm3 in volume, were 1.48+/-0.42 and 1.08+/-0.16, respectively. These ratios in patients with glioma (0.30+/-0.05 and 0.31+/-0.07 respectively) or meningioma (0.34+/-0.10 and 0.41+/-0.17, respectively) showed a significant difference from those in patients with CNS lymphoma (P < 0.0005). CONCLUSION: 123I-IMP SPECT is a helpful tool for diagnosing CNS lymphoma.     

“Luxury perfusion” with99mTc-HMPAO and123I-IMP SPECT imaging during the subacute phase of stroke

To compare the merits of¹²³I-isopropyl-iodoam-phetamine (¹²³I-IMP) and^99mTc-HMPAO in showing abnormal brain uptake distribution during cerebral ischemia, we studied ten patients during the subacute phase of their stroke, a period where metabolism and blood flow are frequently uncoupled. SPECT imaging was performed using both radiopharmaceuticals in the 10 patients from 48 h to 4 weeks after onset of symptoms. Two patients out of the 10 had similar defects with¹²³I-IMP and^99mTc-HMPAO SPECT, the location of the defects corresponding to the area of infarction observed on CT. Six patients had normal^99mTc-HMPAO SPECT and abnormal¹²³I-IMP SPECT with defects in the area of infarction shown by CT. The remaining 2 patients had hyperactive abnormalities on^99mTc-HMPAO in areas corresponding to defects on the¹²³I-IMP images. Two of the patients with SPECT mismatches were studied again more than 1 month after onset. On reexamination,^99mTc-HMPAO SPECT which was previously normal or hyperactive became hypoactive with a focal area of decreased activity corresponding to the defect on¹²³I-IMP. Crossed cerebellar diaschisis was found in 7 patients with^99mTc-HMPAO and was absent for both¹²³I-IMP and^99mTc-HMPAO in 3. We suggest that SPECT with⁹⁹mTc-HMPAO could show transient hyperemia not demonstrated by¹²³I-IMP whereas in some cases cerebral infarction would be more difficult to demonstrate with^99mTc-HMPAO than with¹²³I-IMP. SPECT with both tracers is recommended to follow the evolution of strokes in terms of regional cerebral blood flow and tissue metabolism.     

Brain PET and technetium-99m-ECD SPECT imaging in Lhermitte-Duclos disease

Two patients with Lhermitte-Duclos disease were evaluated by brain positron emission tomography (PET) and technetium-99m-ethyl cysteinate dimer (99mTc-ECD) single-photon emission computed tomography (SPECT). In the lesions in both patients, hyperperfusion was detected on cerebral blood flow images obtained by PET, and hyperactivity by standard 99mTc-ECD SPECT. Dynamic 99mTc-ECD SPECT images demonstrated a plateau of activity in each lesion. These findings suggest that lesions in Lhermitte-Duclos disease have a retention mechanism for 99mTc-ECD equivalent to that of normal neural tissue.     

Evaluation of time dependency of the acetazolamide effect on cerebral hemodynamics as measured by 99mTc-ECD single-photon emission computed tomography

PURPOSE: Kuwabara et al. have examined the cerebral artery dilation with acetazolamide (ACZ) challenge test using PET. And, they reported that ACZ reaction came out time dependently. We have developed a unique SPECT's method using Technetium-99m ethyl cysteinate dimer (99mTc-ECD) to verify the results obtained by Kuwabara et al. METHOD: 1000 MBq of 99mTc-ECD was exactly divided into three syringes. Each of which was intravenous infused (i.v.) at rest, 7.5, and 20 minutes after ACZ administration. Data collection was started using dynamic SPECT immediately after 99mTc-ECD i.v. at rest. Using necessary data only, SPECT images representing each of the three 99mTc-ECD i.v. was reconstructed. SPECT counts were obtained by the ROI method from each images to calculate relative CBF from rest to 7.5 and 20 minutes after ACZ administration. RESULT: The 18 hemispheres of nine patients in the negative control group in whom ACZ was not loaded. CBF was stable during the three evaluation. The measurement error our method was estimated as small. The 18 hemispheres of nine patients in the positive control group who has normal vasodilatory reserve, CBF was increased by 26.2 +/- 8.1% at 7.5 minutes and 29.3 +/- 13.1% at 20 minutes after ACZ administration. Seven patients with and chronic stage unilateral internal carotid artery severe stenosis and/or occlusion were evaluated as the test group. Case of unaffected side, CBF was increased by 17.6 +/- 6.9% at 7.5 minutes and 24.8 +/- 11.3% 20 minutes after ACZ administration. And, increase rate of CBF in the affected side was 2.8 +/- 1.6% at 7.5 minutes and 17.3 +/- 5.0% at 20 minutes after ACZ administration. In the affected side, timing of the maximum CBF increase caused by ACZ was remarkably delayed. CONCLUSION: Our method based on 99mTc-ECD SPECT also revealed delayed cerebral artery dilation in the affected side. It was suggested that ACZ reaction came out time dependently, as reported by Kuwabara et al.     

Metabolism of 99mTc-ethylcysteinate dimer in infarcted brain tissue of rats.

Brain SPECT with 99mTc-ethylcysteinate dimer (99mTc-ECD) reveals a subacute cerebral infarct as a hypoactive area, even in the presence of postischemic hyperperfusion. The brain retention of 99mTc-ECD depends on hydrophilic conversion mediated by enzymes, and impaired enzymatic trapping is hypothesized to depress the retention efficiency in the infarcted region. The aim of this study was to determine whether the metabolic rate of 99mTc-ECD is actually reduced in infarcted brain tissue. METHODS: In 50 mmol/L phosphate buffer (pH 7.4), 99mTc-ECD was incubated for 30 min with homogenates of rat brain tissue with and without triphenyltetrazolium chloride (TTC) staining. The ratio of polar products was determined by thin-layer chromatography as a function of incubation time, and metabolic rates were obtained. Permanent focal ischemia was induced by occlusion of the right middle cerebral artery (MCA) in rats. The brain was removed 24 h after MCA occlusion, and the infarcted area was defined by TTC staining. The metabolic rate of 99mTc-ECD was determined in homogenates of infarcted tissue, contralateral noninfarcted tissue, and tissue sampled from sham-operated rats. The infarct volume was measured by direct and indirect methods to assess volume expansion caused by edema, and the metabolic rate in infarcted tissue was corrected for the effect of edema. RESULTS: TTC staining had no effect on the metabolic rate of 99mTc-ECD. The metabolic rates in the infarcted tissue were 0.222%/min +/- 0.054%/min and 0.285%/min +/- 0.064%/min before and after correction for edema, respectively. These rates were significantly lower than those in the contralateral noninfarcted tissue (0.426%/min +/- 0.028%/min) and the tissue sampled from the sham-operated rats (0.439%/min +/- 0.031%/min). No substantial difference in rates was observed between the contralateral tissue and the tissue from the sham-operated rats. CONCLUSION: The results of this study showed that infarction decreases the activity of enzymes that mediate the hydrophilic conversion of 99mTc-ECD in the brain and suggest that reduced metabolic activity is related to decreased accumulation of 99mTc-ECD in hyperperfused infarcts.     

Usefulness of 99mTc ethyl cysteinate dimer brain SPECT to detect abnormal regional cerebral blood flow in patients with acute carbon monoxide poisoning

99mTc ethyl cysteinate dimer (99mTc-ECD) brain single photon emission computed tomography (SPECT) was used to detect abnormal regional cerebral blood flow (rCBF) in patients with acute carbon monoxide (CO) poisoning. Ten patients with acute CO poisoning and no past histories of psychoneurological disorders were enrolled in this study. After oxygen treatment, all of the 10 patients were investigated using 99mTc-ECD brain SPECT and brain computed tomography (CT) scan. Brain CT scan findings were normal in all of the 10 patients. 99mTc-ECD brain SPECT showed the hypoperfusion lesions of the basal ganglia and brain cortex in five and seven patients, respectively. Only three of the 10 patients had normal 99mTc-ECD brain SPECT findings. This study suggests that, in comparison with brain CT scan, 99mTc-ECD brain SPECT is a better tool for the early detection of hypoperfusion brain lesions in acute CO poisoning in patients with normal brain CT findings.     

Development of “super rapid dynamic SPECT,” and analysis of retention process of<Superscript>99m</Superscript>Tc-ECD in ischemie lesions: Comparative study with<Superscript>133</Superscript>Xe SPECT

To analyze the retention process of technetium-99m ethyl cysteinate dimer (99mTc-ECD) in normal and ischemic lesions, we developed a super rapid dynamic SPECT system based on the CERASPECT (DSI, Inc., Waltham, MA, USA). The system made it possible to take a SPECT series every 2 seconds. Each SPECT series contains a maximum of 16 slices (6.6 mm slice interval) in a matrix size of 32 x 32. The sensitivity of this system is 175 kcps/MBq/ml/cm slice thickness, and resolution is 12 mm FWHM at the center of a 20 cm(phi) water phantom. Using the super rapid SPECT system, the kinetic behavior of the 99mTc-ECD during retention in normal and ischemic lesions was analyzed. Twenty patients with ischemic lesions that were clearly demonstrated by 133Xe-rCBF (regional cerebral blood flow) SPECT but unclear on static 99mTc-ECD SPECT were examined. For the dynamic SPECT, 700 MBq of 99mTc-ECD was injected intravenously, and dynamic SPECT data were acquired every 2 seconds during a 90-second period. The serial dynamic SPECT and time-activity curves at some lesions with reduced rCBF and at the contralateral normal brain were analyzed. These dynamic SPECT data were compared with conventional static 99mTc-ECD SPECT and quantitative 133Xe-rCBF SPECT. All of mildly or moderately reduced rCBF lesions on the 133Xe-rCBF SPECT were recognized as low activity regions only at the early phase (during about 2-20 sec or less), with the lesions then gradually vanishing. These lesions were not recognized on the conventional static SPECT taken after the dynamic study. The time-activity curve at the reduced rCBF lesion was lower than that of contralateral normal brain at the early phase, and overtook the activity in the normal region with a gradual increase. The early phase images of 99mTc-ECD SPECT within 20 seconds by the super rapid dynamic SPECT were very useful to the same extent as the 133Xe-rCBF SPECT for detecting mild or moderate ischemic lesions. This study suggests that esterase activity, participating in the ECD retention mechanism, may be tolerable to mild or moderate ischemia. This tolerance may be the main cause of the nonlinear relationship between ECD accumulation and cerebral blood flow.     

Blood flow measurement of brain tumor by 123I-IMP using 3-heads rotating gamma camera SPECT]

Using 3-heads rotating gamma camera SPECT system, regional blood flow was measured from the super-early image obtained 4 to 6 minutes after the intravenous injection of 123I-IMP on 11 patients with various brain tumors. Two cases of olfactory groove meningioma and malignant astrocytoma showed significantly high 123I-IMP uptake by the lesion visualized by MRI compared to the uptake by normal brain cortex on super-early image but 123I-IMP uptake by the tumor decreased on early image. In both cases, blood flow of the tumor measured from super-early image showed values much higher than those of normal brain cortex. It was thought that usual correction method based on early image did not correctly represent the blood flow of the lesion but that the present method based on super-early image could show the increase of blood flow of the tumor.     

Phase I clinical study of 99mTc-ECD]

A phase I clinical study of 99mTc-L,L-ethyl cysteinate dimer (99mTc-ECD) was carried out in 3 normal volunteers. There was no significant change in vital signs and laboratory parameters attributing to the radiopharmaceutical. 99mTc-ECD was rapidly taken up by the brain, reaching the maximum peak activity within 1 min after the injection and remained relatively constant over several hours. The brain uptake of 99mTc-ECD at 5 min was 5.4 +/- 0.5% which decreased to 5.0 +/- 0.3% by 65 min. 99mTc-ECD cleared rapidly from other organs. The primary excretion route was through the kidneys. Cumulative 99mTc activity in the urine at 90 min and 24 hr were 60.2 +/- 7.3% and 88.5 +/- 10.3%, respectively. The critical organ was the bladder wall with an estimated radiation dose of 0.073 mGy/MBq, which was acceptable value. Clear SPECT images were obtained at 30, 90 and 150 min postinjection. In conclusion, 99mTc-ECD is a safe and promising radiopharmaceutical for the evaluation of regional cerebral blood flow.     

Double-tracer SPECT in patients with AIDS encephalopathy: a comparison of 123I-IMP with 99Tcm-HMPAO.

Single photon emission computed tomography (SPECT) using N-isopropyl-p-(123I)iodoamphetamine (123I-IMP) and 99Tcm-hexamethylpropyleneamine oxime (99Tcm-HMPAO) was performed in 25 patients with different clinical stages of AIDS encephalopathy. The average interval between the two examinations was 7 days. In 15 of the 25 cases (60%) 99Tcm-HMPAO scans were different from 123I-IMP scans. Uptake defects of different extent were observed in 8 of 25 cases (32%), of different extent and different location in 3 of 25 cases (12%) and of identical extent but of different location in 4 of 25 cases (16%). Differences in the uptake patterns of 123I-IMP and 99Tcm-HMPAO with regard to extent and/or location were more commonly shown in patients with early acquired immunodeficiency syndrome (AIDS) encephalopathy (P = 0.0372). In this group, 99Tcm-HMPAO showed uptake defects of greater extent more frequently than did 123I-IMP (P = 0.0156). Our data indicate different brain uptake mechanisms of 123I-IMP and 99Tcm-HMPAO in early and advanced AIDS encephalopathy.     

Visualization of the motor activation area using SPECT in neurosurgical patients with lesions near the central sulcus.

The purpose of this study was to visualize the motor area related to finger movement and a fist-making task using SPECT in patients with lesions near the central sulcus. METHODS: Eleven patients (9 with a brain tumor, 1 with cerebral infarction, and 1 with an arteriovenous malformation) were investigated. The first intravenous injection of 99mTc-ethyl cysteinate dimer (ECD) for the motor activation SPECT images was administered 2 min after completion of the fist-making task with the hand contralateral to the brain lesion. The movement was stopped 2 min after injection, and activation SPECT was performed. After the scan, the second dose of 99mTc-ECD was injected into resting patients, and a second set of SPECT images was acquired. The first set of images was subtracted from the second set to obtain control images. Regions of interest were set bilaterally on the sensorimotor hand area; the supplementary motor area; the frontal, temporal, and occipital lobes; and the cerebellar hemispheres. The results of activation SPECT were expressed as positive or negative for a high-count area, and the regional percentage change for activation images relative to resting images was calculated. RESULTS: Visual assessment of activation images was positive in 9 patients for the sensorimotor hand area and 7 patients for the supplementary motor area. The regional percentage change between activation and resting images for the high-count areas was 19.7% for the sensorimotor hand area and 18.2% for the supplementary motor area. Both values were significantly higher than those for other areas (P<0.05). CONCLUSION: Motor activation SPECT using a 99mTc-ECD split-dose method is easy to perform and may be helpful for presurgical visualization and identification of the sensorimotor hand area or the supplementary motor area.     

Low efficacy of 18F-FDG PET for detection of uveal malignant melanoma compared with 123I-IMP SPECT.

Earlier investigations showed that N-isopropyl-p-123I-iodoamphetamine SPECT (123I-IMP SPECT) is useful for the diagnosis of uveal malignant melanoma, whereas the feasibility and usefulness of 18F-FDG PET in uveal malignant melanoma have not yet been established. We compared the usefulness of 123I-IMP SPECT and 18F-FDG PET for the detection of uveal malignant melanoma on the same subjects. METHODS: Nineteen patients (10 men, 9 women) with suspected uveal malignant melanoma were examined by 123I-IMP SPECT. Thirteen of them were also examined by 18F-FDG PET. 123I-IMP SPECT was performed at 15 min or at 3 and 24 h after intravenous administration of 123I-IMP. RESULTS: In 12 of 19 study patients, 123I-IMP SPECT obtained at 24 h after intravenous administration of 123I-IMP delineated an area of increased uptake in the site corresponding to the ocular tumor. All of the ocular tumors in the 12 123I-IMP SPECT-positive patients were confirmed histopathologically and clinically to be uveal malignant melanoma. The other 7 123I-IMP-SPECT-negative patients have been monitored under the diagnosis of choroidal nevus, choroidal hemangioma, hyperplasia of the pigment epithelium of the retina, or idiopathic inflammatory lesions without any complications. In a total of 13 patients examined by 18F-FDG PET, 9 of whom were 123I-IMP SPECT positive and 4 were negative, only 1 patient showed abnormal uptake of 18F-FDG PET in the site corresponding to the ocular tumor. Therefore, 8 of 9 patients with uveal malignant melanoma showed false-negative results in 18F-FDG PET. The 18F-FDG PET-positive patient with uveal malignant melanoma had the largest tumor mass with a short diameter of 12 mm, a long diameter of 17 mm, and a height of 7 mm. In the other 8 18F-FDG PET-negative patients, the tumors had a dimension of 11 x 13 x 7 mm or less. CONCLUSION: 123I-IMP SPECT is a sensitive and accurate method for the detection of uveal malignant melanoma, whereas the efficacy of 18F-FDG PET for this purpose is low because of a high incidence of false-negative results. 123I-IMP SPECT is far more superior in comparison with 18F-FDG PET in detecting uveal malignant melanoma.     

Usefulness of 123I-IMP SPECT in patients with epilepsy

N-isopropyl-p-[123I]iodoamphetamine(123I-IMP)SPECT and electroencephalography (EEG) were evaluated in 21 epileptic patients at interictal stage. The findings of 123I-IMP were compared with those of clinical symptoms and EEG. In 11 cases (85%) of 13 patients with the partial seizure, and 6 cases (75%) of 8 patients with the generalized seizure had focal decreased perfusion of 123I-IMP. The mean number of focal decreased perfusion areas were 3.2 locations 1 case. There were no cases that was observed focal increased perfusion. Focal decreased perfusion area of 123I-IMP SPECT findings agreed with the focuses those were inferred from clinical findings in 8 cases (62%) out of 13 patients with the partial seizure, did not agree in 3 cases (23%) and did not detected in 2 cases (15%). Overall abnormality of 123I-IMP SPECT was observed in 17 cases (81%) out of 21 patients, on the other hand abnormality of EEG was observed in 12 cases (57%). 123I-IMP SPECT may provide useful information for evaluating foci in patients with epilepsy.