A new radiopharmaceutical for the cerebral dopaminergic presynaptic function: 6-radioiodinated L-meta-tyrosine.

Geometric isomers of radioiodinated L-meta-tyrosine, 6-[I-125]iodo-and 4-[1-125]iodo-L-meta-tyrosine (6-I-L-mTyr, 4-I-L-mTyr) were separated by high-performance liquid chromatography . Both 6-I- and 4-I-L-mTyr had high energy-dependent brain accumulation. 6-I- and 4-I-L-mTyr were also metabolically stable and were rapidly excreted through the urine. 6-I-L-mTyr had a predilection for the cerebral aromatic L-amino acid decarboxylase (DOPA decarboxylase), the final enzyme of dopamine biosynthesis. 6-Radioiodinated L-mTyr is a new radiopharmaceutical that can be both useful in assessing cerebral amino acid transport mechanism and quantifying metabolically active DOPA decarboxylase.

Comparative study of regional cerebral blood flow images by SPECT using xenon-133, iodine-123 IMP, and technetium-99m HM-PAO.

Regional cerebral blood flow (rCBF) was measured by single photon emission computed tomography (SPECT) using 133Xe, N-isopropyl-p-[123I]iodoamphetamine ([123I]IMP) and [99mTc] hexamethylpropyleneamine oxime ([99mTc]HM-PAO) in 24 patients with cerebrovascular diseases. The greatest advantage of 133Xe SPECT was to be able to provide absolute rCBF values without arterial sampling. However, its image quality was very poor. Iodine-123 IMP SPECT provided rCBF images of higher quality and it had good correlation to 133Xe SPECT. Iodine-123 IMP SPECT provided the best images to detect mild ischemic lesions. It could detect obstructive or stenotic changes of large cerebral arteries very well except for a moderate stenosis of internal carotid artery. Technetium-99m HM-PAO SPECT also provided very good rCBF images and it had good correlation to 133Xe SPECT. However, the count-density ratios for the ischemic lesions to the contralateral presumed normal areas of [99mTc] HM-PAO SPECT were significantly higher than those of [123I]IMP SPECT.

Critical cerebral blood flow thresholds studied by SPECT using xenon-133 and iodine-123 iodoamphetamine.

Regional cerebral blood flow (rCBF) was assessed in patients with cerebrovascular diseases (CVD) by single photon emission computed tomography (SPECT) using 133Xe and N-isopropyl-p-[123I]iodoamphetamine ([123I]IMP). The purpose of this study was to determine the infarcted and symptomatic blood flow thresholds of cerebral cortex by SPECT. In the 133Xe inhalation method rCBF was calculated by employing the Celsis modification of the Kanno and Lassen algorithm. In the [123I]IMP SPECT quantitation was obtained by counting-rate ratio for the low flow lesion to the contralateral homologous region which was presumed to be normal (Lesion/Normal ratio, L/N ratio). The infarcted and symptomatic blood flow thresholds by 133Xe SPECT was 19-23 and 33-36 ml/100 g/min, respectively. While, those of L/N ratio in the [123I]IMP SPECT were 39-48 and 65-72%, respectively. There was a significant correlation between the ischemic degrees evaluated by 133Xe and [123I]IMP SPECT studies.

Dynamic SPECT with technetium-99m HM-PAO in meningiomas--a comparison with iodine-123 IMP.

Technetium-99m hexamethylpropyleneamine oxime ([99mTc]HM-PAO) has recently been introduced as an alternative to N-isopropyl-p-[123I]iodoamphetamine ([123I]IMP) for measurement of regional cerebral blood flow. This study compares dynamic SPECT studies using the two tracers in seven patients with meningiomas. Regions of interest were placed over the lesion and contralateral homologous presumed normal area. The counting-rate ratio for the lesion to the contralateral homologous area (L/N ratio) was then calculated in the first image. L/N ratios of [99mTc]HM-PAO single photon emission computed tomography (SPECT) were lower than those of [123I])IMP SPECT, particularly in hypervascular meningiomas. Furthermore, time-activity curves showed that the washout of [99mTc]HM-PAO in the tumors was very slow or incomplete, preventing an accurate assessment of vascularity of meningiomas with [99mTc]HM-PAO, as is generally possible with [123I]IMP.

Dynamic SPECT with iodine-123 IMP in meningiomas.

Dynamic studies of single photon emission computed tomography (SPECT) were performed with intravenous administration of N-isopropyl-p-[123I]iodoamphetamine ([123I]IMP) in 12 patients with meningiomas. Their vascularities were also assessed by angiography. Regions of interest (ROIs) were placed over the lesion and the contralateral presumed normal area, the symmetrical one if possible. Time-activity curves (TACs) were then constructed and the counting-rate ratio for the lesion to the contralateral presumed normal area (L/N ratio) was calculated in the first image of the dynamic SPECT. TACs were classified into three types: type I, an initial high uptake and rapid washout type, type II, an initial high uptake and slow washout one, and type III, an initial low uptake one. L/N ratios of angioblastic meningiomas were over 300%, while those of many fibroblastic ones were under 100%, at most 105%. We compared L/N ratios with angiographic vascularities and histologic types and conclude that dynamic SPECT with [123I]IMP is the examination of choice for evaluating the vascularity of lesions.

Diagnosis of diffuse hepatocellular diseases using SPECT.

In the scintigraphic diagnosis of diffuse hepatocellular diseases, increased splenic uptake of colloids and splenomegaly are helpful signs. To quantify these patterns, the volume and activity of liver and spleen were measured by using single photon emission computed tomography (SPECT). The spleen-to-liver (S/L) ratios in volume and activity that were calculated from SPECT images were estimated in normal individuals and in patients with diffuse hepatocellular diseases. The maximum normal limits of S/L ratios of volume, activity, and activity/volume were predicted as 0.19, 0.087, and 0.72 (mean +/- 2 s.d.). Twenty-two of twenty-three patients (96%) with liver cirrhosis had at least two elevated S/L ratios, and three elevated S/L ratios could clearly differentiate the patient with liver cirrhosis from normal individuals. On the other hand, only six patients (32%) with chronic hepatitis had elevation of any S/L ratio. Abnormal S/L ratios of activity/volume in the range from 0.72 to 1.05 were not obvious on planar or SPECT images.

High-resolution SPECT to assess hippocampal perfusion in neuropsychiatric diseases.

UNLABELLED: The purpose of this study is to clarify the changes of hippocampal perfusion in neuropsychiatric diseases, including dementia, compared with control subjects, and to correlate hippocampal perfusion with the dementia rating scale and the severity of memory disturbance in patients with these diseases. METHODS: A total of 45 right-handed patients were investigated (13 with dementia of Alzheimer type, 6 with multi-infarct dementia, 4 with progressive dementia with motor neuron disease (MND), 3 with transient global amnesia, 5 with other diseases and 14 control subjects). Regional cerebral blood flow (rCBF) in the parietal cortex and hippocampus was evaluated by high-resolution SPECT technique with HMPAO in all subjects. RESULTS: The rCBF measurements in the bilateral parietal cortices and hippocampus were lower in dementia of Alzheimer type and multi-infarct dementia patients than in controls. Hypoperfusion in the hippocampus was a more sensitive marker than hypoperfusion in the parietal cortex in diagnosing dementia of Alzheimer type. Hippocampal hypoperfusion was observed in demented patients regardless of etiology and in patients having memory disturbance without dementia, such as transient global amnesia. Finally, hippocampal hypoperfusion reflected the severity of dementia and memory disturbance regardless of etiology. CONCLUSION: The rCBF image with high-resolution SPECT system may be useful in assessing the extent of dementia and memory disturbance in patients with neuropsychiatric diseases.

Crossed cerebellar diaschisis: analysis of iodine-123-IMP SPECT imaging.

UNLABELLED: The aim of this study was to review the etiology of CCD and study factors that affect the development and manifestation of CCD. METHODS: Three hundred and eleven patients with supratentorial lesions were evaluated for the presence of CCD with SPECT and 123I-IMP. In representative cases, continuous arterial blood sampling was done and rCBF was calculated using Kuhl's method. RESULTS: IMP-SPECT detected an abnormality in 206 patients, of whom 30 had CCD. Of CCD patients, 27 had more than single lobe involvement, 17 had motor impairment, 8 of 11 had rCBF of less than 29.1 +/- 10.9 ml/100 g/min. There was also a significant difference in rCBF between non-CCD and CCD cases. CONCLUSION: Although CCD can also occur with dementia (mixed or vascular type), it is more common with multilobar lesions. It is also associated with the presence of motor impairment but not related to its severity. It is more likely to develop, however, if rCBF is less than 29.1 +/- 10.9 ml/100 g/min regardless of etiology.

The utility of cerebral blood flow imaging in patients with the unique syndrome of progressive dementia with motor neuron disease.

Two patients presenting with progressive dementia coupled with motor neuron disease underwent brain SPECT using N-isopropyl-p iodine-123-iodoamphetamine [( 123I]IMP). The characteristic clinical features of progressive dementia and motor neuron disease were noted. IMP SPECT also revealed reduced uptake in the bilateral frontal and temporal regions, with no reduction of uptake in the parietal, parietal-occipital regions. We conclude that IMP SPECT has potential for the evaluation of progressive dementia with motor neuron disease.

Thallium-201 SPECT for predicting histological types of meningiomas.

Early and delayed 201Tl SPECT studies were performed on 13 patients with intracranial meningiomas, which were classified in three groups according to their histological types: meningothelial (n = 7); transitional and fibroblastic (n = 3); and malignant types (n = 3). The early uptake indices (UI, ratios of average counts/pixel in the lesion to those of the contralateral area on early images) were relatively high in all types: meningothelial meningiomas, 5.75 +/- 2.16 (mean +/- s.d.); transitional and fibroblastic meningiomas, 4.69 +/- 0.54; and malignant meningiomas, 7.10 +/- 3.72. There were no statistical differences in relation to histological type. The delayed uptake indices were 2.65 +/- 0.89, 3.37 +/- 1.02, and 5.16 +/- 1.62, respectively. Statistically, the delayed UI of meningothelial meningiomas were lower than those of malignant types (p < 0.05). The retention indices (RI, ratios of delayed to early UI) were 0.48 +/- 0.08, 0.79 +/- 0.16, and 0.84 +/- 0.16, respectively. The RI of the meningothelial type were also statistically lower than those of the other two groups (p < 0.05). There were no statistically significant differences between transitional plus fibroblastic types and malignant meningiomas. We conclude that 201Tl exhibits early high accumulations in all types of meningiomas, but its retention rates probably differ according to histological types, and a high retention index is predictive of the malignant potential in a meningioma.

Cerebral perfusion imaging evaluates pharmacologic treatment of unilateral moyamoya disease.

Unilateral Moyamoya disease presents as unilateral stenosis or obstruction of the supraclinoid internal carotid artery, which causes cerebral hypoperfusion resulting in seizures or TIA-like attacks. In severe cases, surgical treatment is performed with superficial temporal artery-middle cerebral artery anastomosis. In mild cases, conservative management is the treatment of choice. Flunarizine is a calcium ion anti-blocking agent, whose primary effect is that the cerebral vessels have been used for the treatment of postcerebrovascular disorders. Recently, it has been suggested that flunarizine could be used to treat Moyamoya disease. This report documents the efficacy of flunarizine to improve regional cerebral perfusion in Moyamoya disease.

Cerebral blood flow study in patients with moyamoya disease evaluated by IMP SPECT.

UNLABELLED: We studied the usefulness of IMP SPECT with acetazolamide in 16 patients with moyamoya disease. Cerebral angiography was performed for all patients who were classified in three grades according to their angiographic stages. METHODS: Techniques used included ring-type emission computed tomography with a minicomputer system. Patients received 111 MBq of 123I-IMP and SPECT images were obtained 20 min postinjection. Nine patients were studied using iodoamphetamine (IMP) SPECT with and without acetazolamide. IMP SPECT with acetazolamide was performed 20 min after each injection of 1 g of acetazolamide. RESULTS: Low perfusion areas in the upper and lower frontal, parietal and temporal regions in grades 2 and 3 using IMP SPECT were observed. The mean cerebral-to-cerebellar activity ratios (C/C ratio) of six regions (upper and lower frontal, temporal, parietal occipital and basal ganglia) in grades 1, 2 and 3 were 0.96 to 1.06, 0.91 to 0.96 and 0.76 to 0.88, respectively. CONCLUSION: Our results indicate that measurement of regional cerebral blood flow (rCBF) elucidates cerebral hemodynamic factors, including the reactivity of cerebral vessels which cannot be detected angiographically in patients with moyamoya disease, and that the acetazolamide test is useful for detecting cerebral blood flow reserve. The test can be used to detect disease progress prospectively.

Acetazolamide challenge and technetium-99m-ECD versus iodine-123-IMP SPECT in chronic occlusive cerebrovascular disease.

UNLABELLED: We compared the acetazolamide challenge test using 99mTc-ECD SPECT and 123I-IMP SPECT images in patients with chronic occlusive cerebrovascular disease. We also evaluated the usefulness of linearization correction for acetazolamide challenge test of 99mTc-ECD SPECT. METHODS: Twenty patients with unilateral chronic occlusive cerebrovascular disease (10 patients had middle cerebral arterial lesion and 10 had internal carotid lesion) were included in the study. Split-dose (a dose fractioning was 1:2), and sequential SPECT technique was used for 99mTc-ECD SPECT studies while only acetazolamide challenge test studies for 123I-IMP SPECT were performed. Permeability surface area product model (PS model) and back-diffusion model (Lassen's correction) were used for linearization correction of acetazolamide challenge with 99mTc-ECD SPECT. RESULTS: Six of 16 patients with reduced vasodilatory capacity in 123I-IMP SPECT were underestimated by 99mTc-ECD SPECT acetazolamide challenge test. Relative ECD uptake normalized by cerebellar uptake compared with IMP uptake showed a nonlinear relationship, indicating relatively less uptake in high flow range. The underestimations of limited vasodilatory capacity observed in 99mTc-ECD SPECT without linearization correction was modified by linearization algorithm. However, the effect of correction based on PS model was superior than that of Lassen's correction. The corrected 99mTc-ECD uptake ratio, based on PS model, and IMP uptake ratio demonstrated a better linear relationship than that of Lassen's correction. CONCLUSION: Technetium-99m ECD SPECT corrected based on the PS model is a better method of linearization for evaluating cerebrovascular reserve using acetazolamide challenge.

Technetium-99m-sestamibi scintigraphy compared with thallium-201 in evaluation of thyroid tumors.

UNLABELLED: Technetium-99m methoxyisobutylisonitrile (MIBI) is a myocardial perfusion imaging agent that has been reported to effectively localize in various tumors (e.g., lung and thyroid carcinomas and osteogenic sarcoma). To determine its usefulness in thyroid tumors, we compared 99mTc-MIBI with 201TI imaging. METHOD: We evaluated 25 patients with thyroid tumors (papillary carcinoma in 11, follicular carcinoma in 2, follicular adenoma in 7, adenomatous goiter in 5). Fifteen metastatic lesions from differentiated thyroid carcinomas were also evaluated. Early (10 min after injection) and delayed images (120 min after injection) were obtained for both 99mTc-MIBI and 201TI scintigraphy. RESULTS: The early images showed very similar findings for both 99mTc-MIBI and 201TI. However, the delayed images showed that malignant tumors tended to retain more tracer agent than benign nodules. Marked retention was in 61.5% (8 of 13) of 201TI images and 53.8% (7 of 13) of 99mTc-MIBI images. For metastatic lesions from thyroid carcinomas, the findings for 99mTc-MIBI imaging were nearly identical to those for 201TI imaging. A slight difference in clarity was seen that may have been due to the effect of the 99mTc. CONCLUSION: Although 99mTc-MIBI scintigraphy does not have particularly good results in differentiating malignant from benign thyroid tumors, it may be useful in evaluating metastases or predicting recurrence because of its better imaging characteristics.

Regional cerebral blood flow study with 123I-IMP in patients with degenerative dementia.

Regional cerebral blood flow was evaluated by single-photon emission CT (SPECT) with 123I-N-isopropyl-p-iodoamphetamine (123I-IMP) in 11 patients with dementia of the Alzheimer type, three patients with progressive dementia and motor neuron disease, and eight healthy control subjects. Regional blood flow measurements in the bilateral frontal, parietal association, and temporal cortices were lower in the Alzheimer dementia patients than in controls. Flow deficits in the parietal association cortex were demonstrated in all patients with Alzheimer-type dementia; these deficits were correlated with the severity of disease. Lateral hemispheric asymmetry was seen in nine of 11 patients with Alzheimer-type dementia. In all three patients with progressive dementia and motor neuron disease, flow deficits were demonstrated in the bilateral frontal and temporal cortices, but no flow deficits were seen in the parietal association cortex. Brain SPECT with 123I-IMP may be useful in the differential diagnosis and evaluation of the severity of degenerative dementia.

MR imaging in patients with primary thyroid lymphoma.

The authors describe two patients with thyroid lymphoma and Hashimoto thyroiditis; T1- and T2-weighted MR sequences were used. In one patient, the region of lymphoma showed a different signal intensity on T2 images; in the other patient, the signal level was identical to the Hashimoto disease. In sum, the processes could not be significantly differentiated using MR.

Detection of recurrent thyroid cancer: MR versus thallium-201 scintigraphy.

PURPOSE: To compare MR with thallium-201 scintigraphy in the follow-up of patients who have undergone thyroidectomy and modified radical neck dissection for differentiated thyroid cancer. METHODS: Both MR imaging and 201Tl scintigraphy were performed in 39 patients after surgery for differentiated thyroid cancer. Ten patients did not have recurrence; 29 patients had 51 recurrent tumors in the neck and mediastinum. RESULTS: Among 51 tumor sites, 39 sites of recurrence were detected by MR and 24 were detected by 201Tl scintigraphy. The true-positive rate, false-negative rate, true-negative rate, and false-positive rate in detecting recurrent thyroid cancer were 76.5, 23.5, 100, and 0%, respectively, for MR and 47.1, 52.9, 100, and 0%, respectively, for 201Tl scintigraphy. MR was more sensitive than 201Tl scintigraphy in detecting recurrent tumors (especially small metastatic nodes). On T2-weighted MR images, recurrent tumor was characterized by high signal intensity. Scarring in the postoperative thyroid bed was characterized by low signal intensity on both T1- and T2-weighted images. Abnormal accumulation of 201Tl in the postoperative thyroid bed was not observed. CONCLUSIONS: Although both MR images and 201Tl scintigraphy were effective in distinguishing recurrent tumor from postoperative fibrous tissue, MR images were more sensitive than 201Tl scintigraphy in detecting recurrent tumors. These results suggest that MR imaging is more useful than 201Tl scintigraphy in the follow-up evaluation of patients after neck surgery for differentiated thyroid cancer.

Susceptibility-weighted MR for evaluation of vasodilatory capacity with acetazolamide challenge.

PURPOSE: To investigate cerebral vasodilatory capacity by acetazolamide challenge in healthy subjects and in patients with chronic occlusive cerebrovascular disease by using susceptibility-weighted gradient-echo MR imaging. METHODS: Eight patients with chronic occlusive cerebrovascular disease and four healthy volunteers were studied with susceptibility-weighted MR imaging before and after intravenous administration of 1000 mg of acetazolamide. Signal intensities were measured as a function of time in several regions of interest defined on anatomic images. In all patients with chronic occlusive cerebrovascular disease, acetazolamide challenge and resting regional cerebral blood flow were also evaluated with single-photon emission CT (SPECT). RESULTS: In healthy volunteers, signal intensities began to increase 3 to 4 minutes after acetazolamide administration, with a continuous increase during the subsequent 10 minutes. The effect lasted for approximately 45 minutes after administration. In patients with chronic occlusive cerebrovascular disease, signal changes on susceptibility-weighted MR images of occluded areas with normal vasodilatory capacity on SPECT images did not differ from signal changes of nonocclusive areas. In those patients with changes that reflected diminished vasodilatory capacity, the MR images showed a lower percentage of signal changes after acetazolamide administration than those in normally perfused areas. CONCLUSION: Susceptibility-weighted MR imaging offers an alternative method for estimating vasodilatory capacity.

Evaluation of absorption kinetics of orally administered theophylline in rats based on gastrointestinal transit monitoring by gamma scintigraphy.

The gastrointestinal (GI) transit and absorption of orally administered theophylline, a highly absorbable drug without presystemic elimination, were investigated under fasted and fed conditions using three rats in a crossover study. To evaluate the GI transit rate for each segment in vivo, a noninvasive technique, gamma scintigraphy, was employed using a nonabsorbable compound, (99m)Tc-labeled diethylenetriamine pentaacetic acid (DTPA). Using a gamma scintigraphic technique it is possible to simultaneously evaluate the GI transit and absorption of orally administered drug in the same individual. Theophylline was simultaneously administered along with [(99m)Tc]DTPA to animals in the fasted and fed states. Each GI transit pattern, simulated using the GI transit-kinetic model with a lag time factor, was well fitted to the experimental data. Gastric emptying rate varied in each study, even under the same experimental condition. The GI transit pattern for each segment was highly variable, especially in animals in the fed state. This inconsistency in transit pattern was mainly due to the variability in gastric emptying, which was much slower in animals in the fed compared with the fasted state. However, in spite of a large variability of GI transit kinetics, the plasma concentration-time curves of theophylline were well predicted by the GI transit-absorption model using the individual GI transit parameters obtained in the study. The absorption rate of theophylline was considerably reduced in animals in the fed state, because of the reduction of gastric emptying rate. Analysis using GI transit-absorption model and gamma scintigraphic technique made it possible to estimate the variable absorption kinetics regulated by GI transit with huge variability.

Optimal positioning for CT examinations of the skull base. Experimental and clinical studies.

To evaluate the most appropriate CT angles for the skull base, four adult phantom skulls of various shapes were examined by CT. 15 osseous sites in each skull base were selected and the optimum angle for their delineation was determined. Using Reid's base line (0 degree), many sites could be imaged best at angles up to +20 degrees, and +10 degrees was found to be optimum. Examinations of patients using OM-line as a reference disclosed imaging rates in excess of 70% for sites other than the hypoglossal canal, the optic canal and foramen rotundum, which are in horizontal planes.