Katsumi Ishii

Regional Cerebral Blood Volume and Hematocrit Measured in Normal Human Volunteers by Single-Photon Emission Computed Tomography

Single-photon emission computed tomography (SPECT) was used for the measurement of regional cerebral blood volume (CBV) and hematocrit (Hct) in normal healthy human volunteers (mean age 30 ± 8 years). Regional cerebral red blood cell (RBC) volume and plasma volume were determined separately and their responses to carbon dioxide were investigated. Ten right-handed healthy volunteers were the subjects studied. SPECT scans were performed following intravenous injection of the RBC tracer (99mTc-labeled RBC) and plasma tracer (99mTc-labeled human serum albumin) with an interval of 48 h. Regional cerebral Hct was calculated as the regional ratio between RBC and plasma volumes and then was used for calculating CBV. Mean regional CBV in the resting state was 4.81 ± 0.37 ml/100 g brain, significantly greater in the left hemisphere compared with the right by 3.8% (p < 0.01). Mean regional RBC volumes (1.50 ± 0.09 ml/100 g brain) were less than mean regional plasma volumes (3.34 ± 0.28 ml/100 g brain), and mean regional cerebral Hcts were 31.3 ± 1.8%, which was 75.9 ± 2.1% of the large-vessel Hct. During 5% CO2 inhalation, increases in plasma volume (2.48 ± 0.82%/mmHg Paco2) were significantly greater than for RBC volume (1.46 ± 0.48%/mmHg Paco2). Consequently, the cerebral-to-large-vessel Hct ratio was reduced to 72.4 ± 2.2%. Results emphasize the importance of cerebral Hct for the measurement of CBV and indicate that regional cerebral Hcts are not constant when shifted from one physiological state to another.

Bilateral crossed cerebello-cerebral diaschisis and mutism after surgery for cerebellar medulloblastoma

A 7-year-old boy developed mutism after surgery for cerebellar medulloblastoma. Postoperative magnetic resonance imaging (MRI) whowed atrophy of the cerebellar vermis and both cerebellar hemispheres, predominantly on the right side. Single photon emission computed tomography (SPECT) with technetium-99m-ethyl cysteinate dimer (Tc-99m ECD) revealed decreased cerebral blood flow (CBF) in the bilateral thalami, bilateral medial frontal lobes, and left temporal lobe in addition to the cerebellar vermis and both cerebellar hemispheres when mutism was manifest, indicating the existence of bilateral crossed cerebello-cerebral diaschisis (BCCCD). Circulatory disturbance in both cerebellar hemispheres secondary to tumor resection probably caused BCCCD in both cerebral hemispheres, predominantly in the left, via the dentatothalamocortical pathway (DTCP). With recovery of his mutism, CBF increased in the right thalamus, bilateral medial frontal lobes and left temporal lobe. Thus BCCCD was improved, with only a slight decrease in CBF still persisting in the left thalamus. The mechanism of mutism may have involved damage to the cerebellar vermis (the site of incision at operation), the left dentate nucleus (heavily infiltrated by the tumor) and the right dentate nucleus of the cerebellum (affected by circulatory disturbance secondary to acute postoperative edema). The SPECT findings suggested that mutism was associated with BCCCD-induced cerebral circulatory and metabolic hypofunction in the supplementary motor area mediated via the DTCP.

Regional cerebral blood flow during an attack of vertebrobasilar insufficiency.

Using technetium-99m-labeled hexamethylpropyleneamineoxime [( 99mTc]HM-PAO) and single-photon emission computed tomography, we measured changes in regional cerebral blood flow in a 58-year-old man during an attack of vertebrobasilar insufficiency. Angiography demonstrated compression of the left vertebral artery by the osteophytes of cervical spondylosis when the patient turned his head to the left. Measured in the orthostatic position while turning his head to the left during a typical attack of vertebrobasilar insufficiency, regional cerebral blood flow was significantly reduced in the left cerebellum and the right occipital region. Our study illustrates the capability of [99mTc]HM-PAO single-photon emission computed tomography to measure transient reductions in regional cerebral blood flow and to relate these changes to the pathophysiology of vertebrobasilar insufficiency.

Transient seizure activity demonstrated by Tc-99m HMPAO SPECT and diffusion-weighted MR imaging

Cerebral perfusion single photon emission computed tomography (SPECT) has been used to confirm the localization of the epileptic focus and the evaluation of seizure. Recently, diffusion-weighted MR imaging (DWI) has been recognized for evaluation of seizure activity. We describe a case of transient seizure activity demonstrated by Tc-99m HMPAO SPECT and DWI. This patient was a 61-year-old woman with a 10-month history of right middle cerebral artery (MCA) infarction who had a generalized seizure during MRI. DWI immediately after seizure showed transient hyperintensity in the right frontal gray matter and the white matter, and these apparent diffusion coefficients (ADC) were transiently decreased. This transient hyperintensity on DWI corresponded to transient hyperperfusion identifying the epileptic focus on interictal Tc-99m HMPAO SPECT. Transient sustained seizure activity might cause these changes on DWI and SPECT. It was considered that interictal Tc-99m HMPAO SPECT showed the delayed hyperperfusion caused by excitatory neuronal overaction and DWI showed cytotoxic edema seizure-induced by energy failure of the membrane-bound Na/K-ATPase pump.

Interictal crossed cerebellar hyperperfusion on Tc-99m ECD SPECT

Crossed cerebellar hyperperfusion (CCH) in epilepsy is a rare condition that is observed on ictal cerebral perfusion SPECT. The mechanism of CCH assumes that hyperperfusion in the epileptic foci of the unilateral supratentorium causes hyperperfusion secondary to the corticopontocerebellar pathway (CPCP)-mediated remote effect in the contralateral cerebellar hemisphere. This phenomenon is similar to that of crossed cerebellar diaschisis (CCD). In this report we demonstrated interictal CCH in a patient with epilepsy in technetium-99m-ethyl cysteinate dimer (Tc-99m ECD) SPECT of the brain. To the best of our knowledge, interictal CCH has not been reported in the literature. This is the first report to describe the phenomenon with interictal Tc-99m ECD SPECT.

Increased accumulations of AMsopropyl-p-[123I]-iodoamphetamine related to tumefactive multiple sclerosis

We present a 21-year-old woman with tumefactive multiple sclerosis (MS) that exhibited a rapidly progressive course. There were multiple tumor-mimicking contrast-enhance lesions with surrounding edema and mass effect on magnetic resonance imaging. Both early and delayed brain single photon emission computed tomography (SPECT) withN-isopropyl-p-[123I]-iodoamphetamine demonstrated increased accumulations of the tracer and a high retention on the lesions. The SPECT findings represent a diagnostic pitfall for distinguishing MS from malignant brain tumors in patients with intracranial tumor-like lesions.

Satigrel, a New Antiplatelet Agent, Inhibits Platelet Accumulation in Prosthetic Arterial Grafts

BACKGROUND Early and late vascular obstruction are both related to platelet adhesion and aggregation in the grafts. We assessed the effect of satigrel, a new oral antiplatelet agent, on the accumulation of indium-labeled platelets in knitted Dacron grafts inserted proximal to the femoral artery. METHODS Nine patients with arteriosclerosis obliterans receiving grafts were treated with satigrel, and 10 others were enrolled as untreated controls. Scintigraphy was performed in postoperative weeks 2 and 4, and the ratio of the scintillation count of the graft to that of the native artery was calculated to assess platelet accumulation. RESULTS In both weeks 2 and 4, the ratio was significantly smaller in the satigrel group than in the control group for the whole graft, the proximal anastomosis, and the distal anastomosis. CONCLUSIONS Satigrel significantly inhibited platelet accumulation in vascular grafts and thus may be useful for preventing postoperative graft occlusion.

Noninvasive evaluation of the magnitude of aortic and mitral regurgitation by means of Doppler two-dimensional echocardiography

Using transmitral flow velocity and left ventricular ejection flow velocity, we measured left ventricular inflow volume (LVIV) and left ventricular outflow volume (LVOV) by pulsed Doppler echocardiography in 73 patients who had mitral valve regurgitation (MR), aortic valve regurgitation (AR), or no valvular regurgitation. Doppler-determined regurgitant volume (DOPRV), Doppler-determined regurgitant fraction (DOPRF), total stoke volume, and forward stroke volume were calculated to compare the severity assessed by angiographic scoring and the regurgitant fraction determined by radionuclide angiography (RIRF). In 17 patients with MR, LVIV (84.4 +/- 20.4 ml) was significantly greater (p less than 0.01) than LVOV (52.5 +/- 15.7 ml). LVOV, which is equivalent to forward stroke volume, was lower in patients with MR (52.2 +/- 15.7 ml) than in normal subjects (67.0 +/- 15.7 ml). In 15 patients with AR, LVOV (121.7 +/- 61.1 ml) was significantly greater (p less than 0.01) than LVIV (75.1 +/- 28.1 ml) and LVOV, which is equivalent to total stroke volume, was greater in patients with AR (121.7 +/- 61.1 ml) than in normal subjects (64.0 +/- 14.4 ml). DOPRF correlated with RIRF (r = 0.79, p less than 0.01, n = 11). DOPRV (mild: 10.5 +/- 8.5 ml; moderate: 28.8 +/- 13.6 ml; severe: 74.5 +/- 36.7 ml) and DOPRF (mild: 13.7% +/- 11.5%; moderate: 33.1% +/- 14.2%; severe: 52.6% +/- 15.3%) increased markedly with the severity of regurgitation as assessed by cineangiography. In AR, total stroke volume influenced both forward stroke volume and regurgitant volume, and in MR, regurgitant volume influenced both total stroke volume and forward stroke volume. Total stroke volume in AR and regurgitant volume in MR may play a key role in valvular regurgitation.

Radioimaging of Malignant Melanoma Xenografts in Nude Mice Using 111In-labeled Monoclonal Antibody against Human Malignant Melanoma

By using 111In‐labeled monoclonal antibody (ZME‐018) against human malignant melanoma, we examined its usefulness in radioimmunodetection of human melanoma xenografts in nude mice. Two human malignant melanoma cell lines were used in this study, KHm‐1/4; and KHm‐3/ps. KHm‐1/4 cells express melanoma‐associated antigen which is reactive with ZME‐018, whereas KHm‐3/ps cells do not. ZME‐018 was conjugated with DTPA (diethylene triamine pentaacetic acid) first; then the conjugate was labeled with 111In. After these procedures, labeled ZME‐018 retained its binding activity against KHm‐1/4 cells in vitro.