Experimental study on 123I-IMP kinetics in irradiated lung of rabbit]

Radiation-induced alteration of intra-pulmonary kinetics of 123I-IMP was investigated in 11 rabbits received a 50 Gy dose of radiation to the hemithorax. In all of these rabbits examined during 3-17 weeks following the irradiation, an abnormal accumulation was seen in the irradiated lung on the delayed image obtained 60 minutes after the injection of 123I-IMP. The time-activity curves in the irradiated lung following the injection had shallower downslopes of both the initial fast phase and the following slow phase than those of non-irradiated lung, and finally 123I-IMP uptake of the irradiated lung exceeded that of the normal lung. Chest radiographies all of 11 rabbits showed no abnormal shadow and histological studies in 6 of them revealed a relatively slight change or injury of the irradiated lung during 3-17 weeks. These results indicate that this agent may be useful for detecting and assessing relatively early and slight lung injury induced by irradiation.     

Compartment analysis of 123I-IMP brain SPECT

To clarify the kinetics of N-isopropyl [123I]p-iodoamphetamine (IMP) in the brain, 2-compartment analysis was applied for brain SPECT with 57-minute dynamic scan in 9 subjects. The model consisted of blood component and brain tissue component. Two transfer rate constants were defined; k1 showed the rate from the blood to the brain tissue, and k2 was that of back diffusion. The late scan was performed 210 minutes after the tracer injection. Suitable k values best fitting to the dynamic data were determined for all regions of interest. Predicted regional cerebral activity at 210 minutes using 57-minute dynamic data was well agreed with measured activity. These showed the kinetics of IMP in the brain was well described by the 2-compartment model. The partition coefficient (k1/k2 ratio) was as large as about 35, and almost constant in the various brain structures including hypoperfused areas. These findings indicated that the initial IMP images reflected the reasonable CBF distribution, which gave relatively reliable CBF values even if using microsphere model.     

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.     

Prolonged lung retention of123I-IMP in pulmonary fibrosis

We compared radiographic findings and the retention of N-isopropyl- p[123I]-iodoamphetamine (123I-IMP) in 23 patients with pulmonary fibrosis. During the 30 minutes following a rapid injection of 55.5 MBq of 123I-IMP into the antecubital vein, the image of regional activity was stored. After this, 185 MBq of 99mTc-MAA was injected and its image was stored to determine the region of interest. The half time (T1/2) of 123I-IMP release from the lung was calculated in each pixel between 10 and 25 minutes after the injection. Chest roentgenograms were taken, and the lung field was divided into 6 portions (right upper, middle and lower, and left upper, middle and lower). A quantitative score was assigned to the radiographic finding (X-ray score). The T1/2 values in the above patients were longer than the T1/2 values in normal subjects. Prolonged T1/2 values were observed in the lung fields which had high X-ray scores. The X-ray scores and the T1/2 values in corresponding areas had a positive relation.     

Prolonged lung retention of 123I-IMP in pulmonary disease

The accumulation of venously injected 123I-IMP in the lung was studied. Between 30 and 50 min after the injection of the 1.5 mCi 123I-IMP, the concentration of 123I-IMP in the broncho-alveolar lavage fluid were much higher than in the blood. It was considered that 123I-IMP was transported into the alveolar spaces and was absorbed by the alveolar cells. The half time (T1/2) of the 123I-IMP release from the lung between 10 and 25 min immediately after the injection was calculated. In normal subjects the T1/2 ranged between 25 and 44 min and was prolonged in subjects with pulmonary fibrosis, sarcoidosis, and allergic alveolitis. It was considered that the retention of 123I-IMP was related not only to the endothelial cells, but also to the alveolar cells. It was considered that the analysis of the lung release of 123I-IMP forms a new lung dysfunction index.     

Prolonged lung retention of 123I-IMP in pulmonary disease

The accumulation of venously injected ¹²³I-IMP in the lung was studied. Between 30 and 50 min after the injection of the 1.5 mCi ¹²³I-IMP, the concentration of ¹²³I-IMP in the broncho-alveolar lavage fluid were much higher than in the blood. It was considered that ¹²³I-IMP was transported into the alveolar spaces and was absorbed by the alveolar cells. The half time (T _1/2) of the ¹²³I-IMP release from the lung between 10 and 25 min immediately after the injection was calculated. In normal subjects the T _1/2 ranged between 25 and 44 min and was prolonged in subjects with pulmonary fibrosis, sarcoidosis, and allergic alveolitis. It was considered that the retention of ¹²³I-IMP was related not only to the endothelial cells, but also to the alveolar cells. It was considered that the analysis of the lung release of ¹²³I-IMP forms a new lung dysfunction index.     

Remote effects in cerebral infarction--123I-IMP SPECT study

We studied the remote effects in 29 patients with middle cerebral artery territory infarction by using single photon emission computed tomography (SPECT) with N-isopropyl-p-[123I]iodoamphetamine. SPECT demonstrated a reduction in blood flow in the cerebellar hemisphere contralateral to the cerebral infarct, the cortex ipsilateral to the subcortical infarct, the visual cortex distal to the optic radiation lesion, and the thalamus ipsilateral to the cortical infarct. In addition to transient neuronal depression identified with diaschisis, our results indicated that persistent phenomena were apparently involved in these remote effects. The degenerative processes might be related to irreversible effects in remote areas. Clinical symptoms corresponding to the areas of hypoperfusion remote from infarcted lesions were not necessarily present.     

Experimental study on the mechanism of the intrapulmonary kinetics of 123I-IMP in a balloon occluded bronchus in rabbits

To investigate the mechanism of intrapulmonary kinetics of N-isopropyl-p-123I-iodoamphetamine (123I-IMP), we performed lung scanning with 123I-IMP in 13 rabbits in which a unilateral bronchus was occluded by a balloon catheter. In 9 rabbits, on the delayed distribution images, an abnormal accumulation of 123I-IMP was detected in the hypoperfusion area of the peripheral lung field of the occluded bronchus, which was detected on lung perfusion images with 99mTc-MAA. Comparison of early (a summation image during 20 seconds immediately after injection) and delayed (a summation image from 70 to 90 minutes after injection) distribution images confirmed that during this period, 123I-IMP accumulated in the area of reduced distribution of 123I-IMP. Moreover, at the site of abnormal accumulation, washout of 123I-IMP from the lung was delayed compared with that in the normal lung field. We find this experimental study is similar to the results in 63 clinical cases, which we have reported previously, and confirm that pulmonary arterial perfusion, especially hypoperfusion, influences the intrapulmonary kinetics of 123I-IMP.     

Clinical evaluation of Parkinson's disease using 123I-IMP SPECT

N-isopropyl-p[123I]iodoamphetamine (123I-IMP) SPECT and regional cerebral blood flow (rCBF) studies were performed in 20 patients with Parkinson's disease (PD) and 8 normal subjects. RCBF was measured by the arterial blood sampling method which used the microsphere model. We analyzed seven factors which might be related to the rCBF in PD, i.e., age, stage, duration of the disease, cerebral atrophy, severity of dementia, laterality of symptoms and motor disability score (MDS; the degree of akinesia, rigidity, tremor, gait disturbance, freezing and pulsion sign). Compared with normal subjects, global CBF (supratentorial mean rCBF) was reduced 21.8% in PD. In particular, rCBF in the basal ganglia and that of frontal cortex were reduced 25.3%, 24.8%, respectively. Distribution patterns of rCBF in PD were almost as same as those in normals except for cerebellum. The reduction of both rCBFs in the basal ganglia and parietal cortex significantly correlated with MDS (p less than 0.05, respectively). Especially, akinesia was closely correlated to the reduction of rCBF in the parietal cortex (p less than 0.02). Moreover, we observed a significant relationship between cerebral atrophy and reduction of rCBF in each region except for cerebellum. However, there was no significant correlation between the severity of dementia and reduction of rCBF, even in the frontal cortex or parietal cortex. These data show that the severity of dementia in PD may be connected with other factors except for rCBF. 123I-IMP SPECT study is a useful method for clinical evaluation of PD.     

123I-IMP clearance of the lung with diffuse lung disease

N-isopropyl-I-123-p-iodoamphetamine (123I-IMP) is taken up by the capillary endothelial cells during the first pulmonary pass and is released from the lung. To evaluate the effect of the 123I-IMP retention on diffuse lung disease, we studied prolonged 123I-IMP clearance from lung in 5 non-smoking control volunteers and 15 patients with various diffuse lung diseases. The time-activity curve for 60 min after the injection of 111 MBq of 123I-IMP was described as follows: C(t) = A1e-k1t + A2e-k1t (A1, A2: intercepts; K1, K2: slopes of the exponential components). 123I-IMP clearance was delayed in the patient group and K2 was significantly lower. There was a significant correlation between K2 and Ga-computer activity index on the 67Ga scintigraphy in the patient group. K2 was also correlated with %Dlco on the pulmonary function test. Our study suggests that the delayed clearance and retention of 123I-IMP in the diseased lung are influenced by the pathological activity in the lung lesion.     

A case of increased 123I-IMP uptake in adenocarcinoma of the lung

It has been reported that delayed 123I-IMP lung scintigraphy shows a defect corresponding to the tumor with increased accumulation around the tumor, and that an increased accumulation is associated with atelectasis and inflammation. We presented a case of increased uptake of 123I-IMP in lung cancer. None of the other reported case of increased uptake in lung cancer, to our knowledge, occurred. A 55-year-old man had a 6 cm mass in the lower lobe of the right lung. Cytologic examination with a small curette diagnosed the case as an adenocarcinoma. The 123I-IMP scintigraphy was performed 24 hours after intravenous injection of 111 MBq of 123I-IMP. The 123I-IMP SPECT lung images showed an area of increased 123I-IMP concentration corresponding to the tumor mass. The patient's subsequent course was characterized by massive pleural effusion caused by extensive invasion to the pleura despite chemotherapy. He died about 2 months after the 123I-IMP scintigraphy. The right lung removed at necropsy confirmed that the area of high 123I-IMP concentration corresponded to the mass, which proved a poorly differentiated adenocarcinoma. One should note that there is an unusual case with high 123I-IMP uptake in lung cancer.     

123I-IMP SPET in the diagnosis of primary central nervous system lymphoma

We reviewed N-isopropyl-p-[123I]iodoamphetamine (123I-IMP) single-photon emission tomography (SPET) images of brain tumours and assessed the usefulness of 123I-IMP SPET for the diagnosis of primary central nervous system (CNS) lymphoma. We analysed 52 tumours that showed enhancement on magnetic resonance imaging: 11 malignant lymphomas, 3 anaplastic astrocytomas, 17 glioblastomas, 12 meningiomas, 4 metastatic brain tumours and 5 other brain tumours. 123I-IMP uptake in the tumours on early (15-min) and delayed (4-h) scans was visually classified as high, moderate or low as compared with the contralateral brain cortex. Early and delayed 123I-IMP uptake ratios comparing tumours with contralateral brain cortex (T/N ratio) were also calculated. In malignant lymphomas, the visual uptake of 123I-IMP was moderate to high on the delayed scans. The delayed T/N ratios were significantly higher than the early ratios (P<0.05) and all lymphomas, with the exception of one small one, had delayed ratios greater than 0.9. In non-lymphomatous tumours, the visual uptake of 123I-IMP was low on the delayed scans. The delayed T/N ratios were significantly lower than the early ratios (P<0.01) and all non-lymphomatous tumours had delayed ratios of less than 0.8. The T/N ratios of lymphomas were significantly higher than those of non-lymphomatous tumours on both early and delayed scans (P<0.0001). These results suggest that 123I-IMP SPET may be a useful tool in the differential diagnosis of primary CNS lymphoma.     

123I-IMP SPET in the diagnosis of primary central nervous system lymphoma

We reviewed N-isopropyl-p-[¹²³I]iodoamphetamine (¹²³I-IMP) single-photon emission tomography (SPET) images of brain tumours and assessed the usefulness of ¹²³I-IMP SPET for the diagnosis of primary central nervous system (CNS) lymphoma. We analysed 52 tumours that showed enhancement on magnetic resonance imaging: 11 malignant lymphomas, 3 anaplastic astrocytomas, 17 glioblastomas, 12 meningiomas, 4 metastatic brain tumours and 5 other brain tumours. ¹²³I-IMP uptake in the tumours on early (15-min) and delayed (4-h) scans was visually classified as high, moderate or low as compared with the contralateral brain cortex. Early and delayed ¹²³I-IMP uptake ratios comparing tumours with contralateral brain cortex (T/N ratio) were also calculated. In malignant lymphomas, the visual uptake of ¹²³I-IMP was moderate to high on the delayed scans. The delayed T/N ratios were significantly higher than the early ratios (P<0.05) and all lymphomas, with the exception of one small one, had delayed ratios greater than 0.9. In non-lymphomatous tumours, the visual uptake of ¹²³I-IMP was low on the delayed scans. The delayed T/N ratios were significantly lower than the early ratios (P<0.01) and all non-lymphomatous tumours had delayed ratios of less than 0.8. The T/N ratios of lymphomas were significantly higher than those of non-lymphomatous tumours on both early and delayed scans (P<0.0001). These results suggest that ¹²³I-IMP SPET may be a useful tool in the differential diagnosis of primary CNS lymphoma.     

Three-dimensional surface display of brain perfusion with123I-IMP in Parkinson's disease

We reconstructed three-dimensional (3D) surface images from single-photon emission computed tomography (SPECT) data using N-isopropyl-p[¹²³I]-iodoamphetamine (¹²³I-IMP) in 27 patients with Parkinson's disease and 11 normal control subjects. The 3D reconstruction was performed using distance-shaded methods at threshold levels with an interval of 5% from 45–80%. Any area of decreased perfusion at each threshold level was visualised as a defect area by the algorithm. In nondemented patients with Parkinson's disease, perfusion defects were frequently found in the parietal cortex at a threshold value of 65%. In demented patients, perfusion defects were frequently seen at thresholds of 45–65%, and were more marked in the temporal and parietal cortex bilaterally. This suggests that dementia in Parkinson's disease is related to a reduction of perfusion in the temporoparietal cortex.     

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.     

Evaluation of the lung uptake of 123I-IMP by bronchoalveolar lavage

A 67-year-old female with radiation pneumonitis in the right upper lobe underwent lung scanning and bronchoalveolar lavage 4 hours after the intravenous injection of 123I-IMP. The lung scanning showed increased accumulation of 123I-IMP, corresponding with the area of radiation pneumonitis. The ratios of radioactivities of the cellular and noncellular components in the bronchoalveolar lavage fluid to that of the serum, were 27.0 and 0.39, respectively. Our results suggest that 123I-IMP or its metabolites are transported through alveolo-capillary barrier and taken up by free cells in the alveolar space after 123I-IMP has been bound to nonspecific receptor sites in the endothelial cell in the capillary lumen.     

Developmental changes in normal images of 123I-IMP brain SPECT in young children

In an attempt to determine the normal evolution of N-isopropyl p-I-123-iodoamphetamine (123I-IMP) single photon emission computed tomography (SPECT), we selected 12 children (an age range of 1 month-3 year) who were diagnosed as normal in follow-up between 6 month-3 year by neurological examination, X-ray computed tomography, electroencephalography and 123I-IMP SPECT in our 78 cases. SPECT of the brain was performed 30 minutes after intravenous administration of 74 MBq (2 mCi) 123I-IMP using a rotating gamma camera equipped with a 30-degree slant-hole collimator. In neonates, a predominant activity was observed in the basal ganglia and thalamus, with only slight parietal and occipital activity. Frontal cortex was barely recognizable. Under 1 year, cortical activity was gradually increased and clearly visible. After 1 year, SPECT images were similar to those of adult. In conclusion there was an important modification of the regional perfusion pattern in relation to brain maturation.     

Preliminary study of patients with vertigo and dizziness using 123I-IMP

To study the application of cerebral blood flow scintigraphy with 123I-IMP for the evaluation of central dizziness, the difference in 123I-IMP accumulation between the right and left cerebellar hemispheres was determined as an asymmetry index (A.I.) in 8 normal subjects and compared with A.I. from patients with central dizziness. According to estimated lesions, 123I-IMP findings were compared with CT findings. The normal subjects had A.I. of 5.8 +/- 2.1%, whereas 36 patients with central dizziness had A.I. of 12.7 +/- 7.5%. On the basis of an A.I. of 8% or more as an abnormal finding on IMP scintigraphy, 11 of the 14 patients with estimated lesions of cerebellar hemispheres and 16 of the 20 with those of the whole cerebellum including the vermis were evaluated to have had abnormalities. Seven of 11 with estimated lesions of the brainstem and 4 of 5 with vertebrobasilar arterial insufficiency were evaluated to have had abnormalities. The findings of 123I-IMP cerebral blood flow scintigraphy were in good agreement with clinical symptoms in patients with central dizziness with estimated lesions of the cerebellar hemispheres, suggesting the possibility that this method is more useful than CT.