Clinical application of 3D arterial spin-labeled brain perfusion imaging for Alzheimer disease: comparison with brain perfusion SPECT

BACKGROUND AND PURPOSE

Alzheimer disease is the most common neurodegenerative disorder with dementia, and a practical and economic biomarker for diagnosis of Alzheimer disease is needed. Three-dimensional arterial spin-labeling, with its high signal-to-noise ratio, enables measurement of cerebral blood flow precisely without any extrinsic tracers. We evaluated the performance of 3D arterial spin-labeling compared with SPECT, and demonstrated the 3D arterial spin-labeled imaging characteristics in the diagnosis of Alzheimer disease.

MATERIALS AND METHODS

This study included 68 patients with clinically suspected Alzheimer disease who underwent both 3D arterial spin-labeling and SPECT imaging. Two readers independently assessed both images. Kendall W coefficients of concordance (K) were computed, and receiver operating characteristic analyses were performed for each reader. The differences between the images in regional perfusion distribution were evaluated by means of statistical parametric mapping, and the incidence of hypoperfusion of the cerebral watershed area, referred to as "borderzone sign" in the 3D arterial spin-labeled images, was determined.

RESULTS

Readers showed K = 0.82/0.73 for SPECT/3D arterial spin-labeled imaging, and the respective areas under the receiver operating characteristic curve were 0.82/0.69 for reader 1 and 0.80/0.69 for reader 2. Statistical parametric mapping showed that the perisylvian and medial parieto-occipital perfusion in the arterial spin-labeled images was significantly higher than that in the SPECT images. Borderzone sign was observed on 3D arterial spin-labeling in 70% of patients misdiagnosed with Alzheimer disease.

CONCLUSIONS

The diagnostic performance of 3D arterial spin-labeling and SPECT for Alzheimer disease was almost equivalent. Three-dimensional arterial spin-labeled imaging was more influenced by hemodynamic factors than was SPECT imaging.

Benzylidene anabaseines act as high-affinity agonists for insect nicotinic acetylcholine receptors

Benzylidene anabaseines are agonists selective for vertebrate alpha7-nicotinic acetylcholine receptor (nAChR), while they exhibit antagonist activity toward vertebrate alpha4beta2-nAChR. To investigate the effects of benzylidene anabaseines on insect nAChRs, we performed [3H]epibatidine-binding assays and neurophysiological experiments using American cockroach (Periplaneta americana) nerve-cord preparations. Of the six compounds tested, 3-benzylideneanabaseine (BA) and 6'-chloro-3-benzylideneanabaseine (CBA) displayed the highest potency in the binding assays, with K(i)s of 35.0 and 21.2nM, respectively. The introduction of a nitro group at the 4-position of the phenyl group led to a decrease in affinity by two orders of magnitude, while that of a chlorine atom at the 6'-position had little effect on affinity. In neurophysiological experiments, BA at 3.3 microg/ml increased the spike frequency observed with the nerve preparation, as observed with nicotine at 16.6 microg/ml. These findings suggest that benzylidene anabaseines act as high-affinity agonists in P. americana nAChRs and that they might therefore prove useful as probes for insect nAChRs.

Inhibition of human parainfluenza virus type 1 sialidase by analogs of 2-deoxy-2,3-didehydro-N-acetylneuraminic acid

Eleven novel analogs of 2-deoxy-2,3-didehydro-N-acetylneuraminic acid (Neu5Ac2en) modified at the C-4 and C-9 positions were designed and tested for their ability to inhibit sialidase of human parainfluenza virus type 1 (hPIV-1). The analogs modified by the cyanomethyl, amidinomethyl, and thiocarbamoylmethyl groups at the C-4 position exhibited potent inhibition against hPIV-1 sialidase compared with Neu5Ac2en. The most effective compound was thiocarbamoylmethyl analog (4-O-thiocarbamoylmethyl-Neu5Ac2en). The activity of 4-O-thiocarbamoylmethyl-Neu5Ac2en causing 50% enzyme inhibition at a concentration of approximately 1.0x10(-5) M was 30-fold larger than Neu5Ac2en. While, the analogs of Neu5Ac2en modified by the azido and N-acetyl groups at the C-9 showed a decrease in inhibition of sialidase compared with the 9-hydroxy analogs. In addition, 4-O-thiocarbamoylmethyl-Neu5Ac2en strongly inhibited hPIV-1 infections of Lewis lung carcinoma-monkey kidney cells in comparison with Neu5Ac2en. The present findings would provide useful information for the development of anti-human parainfluenza virus compounds.

[MR angiography of hemodialysis access fistula: evaluation before PTA procedure]

We evaluated the feasibility of MR angiography for hemodialysis fistula. Eleven patients with suspected stenosis or occlusion of an autogenous hemodialysis fistula in the forearm underwent MRA. MRA was obtained using both the 3D-PC method and 3D gadolinium contrast-enhanced (CE) method with a knee coil. The two methods were compared with DSA in seven patients. CE-MRA clearly demonstrated the entire dialysis fistula. However, signals of the stenotic area are effaced in PC-MRA. The diameter of the vessels evaluated in the CE-MRA was well correlated with angiography. CE-MRA demonstrated smaller collateral vessels more clearly than PC-MRA. CE-MRA provided useful information before the PTA procedure.

Transient increase in cerebral blood flow in a patient with Sturge-Weber syndrome

We report the case of an infant with Sturge-Weber syndrome whose regional cerebral blood flow (rCBF) showed an increase and a subsequent decrease. As compared with simultaneous CT and MR findings, we speculate that the transient increase in rCBF reflects the neuronal reaction to hypoxia caused by congestion.

Regional cerebral blood flow and glucose utilization in spontaneously epileptic EL mice

The dynamics of the relative regional cerebral blood flow (rCBF) and regional glucose utilization (rGU) were examined in spontaneously epileptic EL mice in the interictal, ictal and postictal states, using autoradiography with 125I-N-isopropyl-p-iodoamphetamine (IMP) and 14C-2-deoxyglucose (DG), respectively.

METHODS

EL mice were used in the study, which have previously been used as a model of the idiopathic human epilepsy. EL mice develop secondary generalized tonic-clonic convulsions, and ddY and EL(o) mice, which do not experience seizures, were used as controls. IMP and DG, respectively, were injected in EL mice in the interictal, ictal and postictal states. We examined the relative rCBF and rGU from the obtained autoradiograms of mouse brain sections.

RESULTS

No significant changes in the relative rCBF were obtained in the hippocampus in the course of epileptic seizures. In contrast, significant increases in the relative rGU were observed in the hippocampus in the ictal and early postictal states. The dissociation between the dynamics of the rCBF and rGU were found in the event of epileptic seizures of EL mice.

CONCLUSION

The flow metabolism dissociation in the ictal and early postictal states is of both conceptual and practical interest, while the reason for the dissociation of rCBF from the rGU in epileptics seizures remains to be established. Our results emphasize the importance of estimating both cerebral perfusion and glucose metabolism in epilepsy.

[Local cerebral blood flow and glucose metabolism during seizure in spontaneously epileptic El Mice]

Local cerebral blood flow and glucose metabolism were examined in spontaneously epileptic El mice using autoradiography with 125I-IMP and 14C-DG in the interictal phase and during seizure. El (+) mice that developed generalized tonic-clonic convulsions and El (-) mice that received no stimulation and had no history of epileptic seizures were examined. The seizure non-susceptible, maternal strain ddY mice were used as control. Uptake ratios for IMP and DG in mouse brain were calculated using the autoradiographic density. In the interictal phase, the pattern of local cerebral blood flow of El (+) mice was similar to that of ddY and El (-) mice, and glucose metabolism in the hippocampus was higher in El (+) mice than in El (-) and ddY mice, but flow and metabolism were nearly matched. During seizure, no significant changed blood flow and increased glucose metabolism in the hippocampus, the epileptic focus, and no markedly changed blood flow and depressed glucose metabolism in other brain regions were observed and considered to be flow-metabolism uncoupling. These observations have never been reported in clinical or experimental studies of epilepsy. Seizures did not cause large regional differences in cerebral blood flow. Therefore, only glucose metabolism is useful for detection of the focus of secondary generalized seizures in El mice, and appeared possibly to be related to the pathophysiology of secondary generalized epilepsy in El mice.

[Assessment of bone mineralization of hemodialyzed patients with SPA and DPA--different effect of PTX with the site]

We analyzed the bone changes at each site of secondary hyperparathyroidism (2 degrees HPT) on hemodialyzed patients using both single photon absorptiometry (SPA) and dual photon absorptiometry (DPA). The subjects were 35 hemodialysis patients (12 male, 24 female) with 2 degrees HPT. The bone mineral densities (BMD) of 1/3 radius, head, total body and 3rd lumbar spine were measured before and after parathyroidectomy (PTX). Before PTX, the BMD of 2 degrees HPT patients were lower than the normal range of all sites, especially at the radius which mainly consisted of cortical bone. After PTX, the BMD at all sites increased especially in the head. The BMD of the radius also continued to increased up two years after PTX, but it was not as increased as the BMD of head. The BMD of the lumbar spine which consisted of cancellous bone mainly increased after PTX for one year and decreased thereafter. This decrease was influenced by age. There was a difference with the site of BMD after PTX. The determination of changes of BMD of head and radius was considered useful for the judgment of treatment.

[A case of peritoneal metastasis from retroperitoneal yolk sac tumor diagnosed by 67Ga-scan and 18F-FDG-PET]

Yolk sac tumor is one of the histological types of germ cell tumors. Primary retroperitoneal germ cell tumors are extremely rare neoplasms. We report a case of peritoneal metastasis after resection of a primary retroperitoneal germ cell tumor. The peritoneal metastases were detected by 67Ga-scan when CT did not suggest metastatic lesions while the level of alphafetoprotein was still elevated. The 67Ga-scan showed multiple hot spots in the abdomen and pelvis 72 hours after intravenous injection of the tracer and no changes were observed in serial scan taken 6 hours after the first scan. These findings were strongly suggested the dissemination of the malignant tumors. A PET study with 18F-fluorodeoxyglucose was performed and showed extensive uptake in the intraabdominal and intrapelvic cavity. It was also useful for understanding the extension and distribution of the peritoneal metastatic lesions. The sites of the accumulation of 18F-fluorodeoxyglucose corresponded to the results found in postmortem.

[Usefulness of 99mTc-PMT SPECT and 18F-FDG PET in diagnosing orbital metastasis of hepatocellular carcinoma]

We reported a case in which 99mTc-PMT scintigraphy was useful in diagnosing orbital metastasis of HCC. The case involved a 70 y.o. male, who had undergone nine transcatheter arterial embolizations over two years because of HCC and who had a past history of gastric cancer. The patient had complained of headache and visual disturbance for two months. Cranial CT and MRI studies showed a large homogeneous mass with remarkable bone destruction in the right lateral orbital wall. Because AFP was elevated, orbital metastasis of HCC was suspected, and 99mTc-PMT scanning was performed. On the planar and SPECT images, very high uptake was found in the right orbital tumor. The FDG-PET study showed remarkable hypermetabolism in the medial portion of tumor and follow-up MRI revealed that the tumor had expanded and invaded to the medial side of the orbit. 99mTc-PMT scanning was critical in diagnosing this case of orbital metastasis, and FDG-PET imaging was useful in determining the most active portion of the tumor.

[A case of mesenteric panniculitis: comparing the findings of 67Ga scintigraphy with pathological results]

We report a case of mesenteric panniculitis where we compared the findings of 67Ga-citrate (Ga) scintigraphy with pathological results. The patients, a 75-year-old man, was hospitalized for examination of low abdominal mass. After hospitalization he developed high CRP levels. A Ba enema revealed serrated intestinal walls and a thick fat density, the margins of which were distinct, as judged from abdominal CT scans. Therefore we suspected a mesenteric panniculitis. Since the patient did not improve under conservative treatment for three months, surgery was performed a day after Ga scintigraphy which showed the abnormal uptake in the abdominal mass, which was removed. The radioactivity of several tissue slices from the resected specimen containing the affected part which had been described inflammatory in the pathological examination showed very high radioactivity. This disease is usually diagnosed from the typical findings of Ba enema and CT scan. But, when an extraordinary abdominal accumulation presents, one should think of performing a Ga scan as an additional diagnostic parameter.

[Evaluation of renal function by factor analysis using 99mTc-MAG3]

The kinetics of 99mTc-mercapto-acetyltriglycine (MAG3), a new renal scintigraphic agent, was studied by factor analysis in patients with chronic renal disorders, and its application to assessment of the renal function was evaluated. Data were collected for 30 minutes from immediately after intravenous injection of MAG3 at 370 MBq, the first pass image and serial renal scintigrams were obtained, and factor analysis was attempted simultaneously. Since most of MAG3 is excreted via the kidney during the first pass, factor analysis was performed. Two factors reflecting renal parenchymal components and pelvic components could be separated in 8 (Cre < or = 2.9 mg/dl) of 10 patients, and they corresponded with respective segmental renograms. In the remaining 2 (Cre > or = 3.0 mg/dl), separation was impossible by 2-factor analysis, and 3-factor analysis was needed. Factor analysis is considered to allow objective evaluation of renal function without setting the ROI.