High uptake of L-3-[123I]iodo-α-methyl tyrosine in pilocytic astrocytomas

Despite a favourable prognosis, pilocytic astrocytomas may exhibit signs of malignancy on various neuroimaging modalities. This retrospective analysis was conducted to determine whether scintigraphic features of malignancy are also found on single-photon emission tomography (SPET) using L-3-[¹²³I]iodo-!-methyl tyrosine (IMT) as a tracer. Twenty patients with pilocytic astrocytomas were retrospectively selected from a large series of patients referred for the evaluation of primary or recurrent brain tumours. IMT SPET was performed in 16 patients, positron emission tomography (PET) using 2-[¹⁸F]fluoro-2-deoxy-D-glucose (FDG) was available in 10 of the patients and SPET using technetium-99m tetrofosmin or thallium-201 had been performed in 11. Image analysis was performed using standard protocols to determine how many patients exceeded the respective thresholds of malignancy. Features of malignancy were found in 7/16 IMT SPET studies, in 7/10 FDG PET studies and in 7/11 of the residual SPET investigations. A significant correlation of tumour size and IMT uptake in primary pilocytic astrocytomas indicated partial volume effects to partly account for the differential uptake behaviour (n=10, r=0.87, P<0.05). Differences in IMT uptake in primaries (1.7ǂ.6, n=10) and in recurrent tumours (2.3ǂ.7, n=6) did not attain statistical significance. IMT SPET results indicative of malignancy are regularly found in pilocytic astrocytomas, despite their good prognosis. No uptake may be detected in largely cystic or in small tumours.     

Kinetics of 3-[123I]iodo-l-α-methyltyrosine transport in rat C6 glioma cells

3-[¹²³I]Iodo-l-α-methyltyrosine (¹²³I-IMT) is used for the diagnosis and monitoring of brain tumours by means of single-photon emission tomography (SPET). To date, little has been known about the system for the transport of ¹²³I-IMT into brain tumour cells. It is assumed that ¹²³I-IMT is transported by a specific carrier for large, neutral amino acids (L-system). In this study, rat C6 glioma cells were used to characterize the uptake system of ¹²³I-IMT and to investigate its precise kinetics. The time course of ¹²³I-IMT uptake into the cells was examined for a range of 1–60 min. ¹²³I-IMT uptake rates with varying concentrations of ¹²³I-IMT (2.5–50 μM) in the medium were quantified to assess the kinetic parameters of ¹²³I-IMT transport. Furthermore, competition of ¹²³I-IMT with other amino acids was investigated to identify the distinct transport systems involved in ¹²³I-IMT uptake. ¹²³I-IMT uptake into C6 glioma cells was linear for approximately 10 min and reached a steady-state level within 30 min. The analysis of the rate of uptake of ¹²³I-IMT at different concentrations was concordant with the predominance of a single uptake system. The apparent Michaelis constant (K _m) of ¹²³I-IMT was 26.2±1.9 μM, and the maximum transport velocity (V _max) was 35.4±1.7 nmol/mg protein per 10 min. 77%±10% of ¹²³I-IMT transport was sodium independent and 23%±3% was sodium dependent. Competitive inhibition of ¹²³I-IMT uptake by 2-aminobicyclo[2.2.1]heptane-2-carboxylic acid, α-(methylamino)isobutyric acid and naturally occurring amino acids revealed a major ¹²³I-IMT transport via the sodium-independent system L (72%) and a minor uptake via the sodium-dependent system B^0,+ (17%). Our results show that ¹²³I-IMT transport into C6 glioma cells is principally mediated by the L-system and to a minor extent by the B^0,+-system. The kinetic parameters of ¹²³I-IMT uptake are in the range of those of naturally occurring amino acids. Received 20 October 1998 and in revised form 25 May 1999     

Evaluation of l-3-[123I]iodo-α-methyltyrosine SPET and [18F]fluorodeoxyglucose PET in the detection and grading of recurrences in patients pretreated for gliomas at follow-up: a comparative study with stereotactic biopsy

. Based on the results of stereotactic biopsy, we evaluated in a prospective fashion the efficiency of l-3-[¹²³I]iodo-α-methyltyrosine-single-photon emission tomography (SPET) and [¹⁸F]fluorodeoxyglucose (FDG) positron emission tomography (PET) in the detection and grading of recurrences in patients previously treated for gliomas. The patient population comprised 30 individuals, nine with astrocytomas of grade II, ten with astrocytomas of grade IV, three with oligoastrocytomas of grade II, six with oligodendrogliomas of grade II and two with anaplastic oligodendrogliomas of grade III) suspected of recurrence and scheduled for further treatment. IMT SPET data were acquired using either by dual-or a triple-headed SPET camera, Multispect 2/3. FDG uptake was measured with an ECAT ART PET camera. Two independent observers classified PET and SPET images as positive or negative for tumour tissue. Uptake of FDG and IMT was evaluated visually and, in the case of IMT, also quantitatively by calculating the ratios between tracer accumulation in the lesion and the unaffected contralateral regions of reference using the region of interest (ROI) technique. The PET and SPET results were compared with the histopathological findings obtained either by stereotactic biopsy or in one case by open surgery. Glucose metabolism and amino acid uptake of recurrences of brain tumours as assessed by FDG-PET and IMT-SPET correlated highly with the histopathological findings. Based on the histopathological data, FDG-PET and IMT-SPET findings confirmed recurrence in all cases of high-grade gliomas (IV). A difference could be demonstrated in low-grade (II–III) tumour recurrences. True-positive IMT-SPET results were found in 86% of grade III and 75% of grade II recurrences, whereas FDG-PET yielded a sensitivity of 71% in tumours of grade III and 50% in those of grade II. With respect to the grade of malignancy of brain tumours at recurrence, IMT-SPET, in contrast to FDG-PET, does not permit adequate in vivo grading of non-mixed brain tumours of astrocytic or oligodendroglial origin. However, in this study FDG-PET did not permit discrimination between upgrading of low-grade oligoastrocytomas (II) into anaplastic oligodendrogliomas (III) and upgrading into glioblastomas (IV) The results of this study indicate that FDG-PET and IMT-SPET are equivalent to stereotactic biopsy in their ability to identify high-grade tumours at recurrence. IMT-SPET proved to be superior to FDG-PET in confirming low-grade recurrences. In the case of suspected progression of the grade of malignancy in ordinary gliomas, FDG-PET correlated significantly with the histopathological grading, whereas IMT-SPET did not. However, tumour grading by FDG-PET has a limitation in mixed brain tumours in that it is not possible to discriminate between progression of the oligo- versus the astrocytic tumour entity. In this case histopathological evaluation of the tumour grade remains necessary. Received 6 August and in revised form 2 November 1998     

Differential kinetics of [123I]β-CIT binding to dopamine and serotonin transporters

Iodine-123-labelled 3-(4-iodophenyl)tropane-2-carboxylic acid ([¹²³I]-CIT) labels both the dopamine transporter (DAT) and the serotonin transporter (5-HTT) and this ligand is able to clarify pathological changes in both dopaminergic and serotonergic systems. However, the differential kinetics of -CIT binding to DAT and 5-HTT has not been clarified fully. In this study we examined time-activity curves of [¹²³I]-CIT in individual regions in the rat brain. Using cerebellum as the reference region,k ₃ andk ₄ values were estimated by a two-compartment kinetic analysis. In the striatum, the kinetics was slowest among all brain areas. In this area specific binding reached its peak 4 h after the injection. In the hypothalamus, specific binding reached its peak 1 h after the injection and its amount did not change until 4 h after the injection. In the occipital cortex, the binding and washout of the ligand were fastest among all brain regions. Estimatedk ₃ values were 0.040±0.003 in the striatum, 0.019±0.002 in the hypothalamus and 0.082±0.011 in the occipital cortex (min^–t, mean ±SD). Estimatedk ₄ values were 0.0034±0.0005 in the striatum, 0.0071±0.0009 in the hypothalamus and 0.083±0.013 in the occipital cortex (min^–1, mean ±SD). Therefore binding kinetics of [¹²³I]-CIT in the region rich in DAT is apparently different from that in the region rich in 5-HTT. These results will provide fundamental data to image both DAT and 5-HTT in one series of examinations with [¹²³I]-CIT.     

Radioiododemercuration: a simple synthesis of 5-[123/125/127I]iodo-2′-deoxyuridine

Through the use of iododemercuration, 5-[^123/125I]iodo-2′-deoxyuridine was synthesized rapidly and with high radiochemical purity from 5-chloromercuri-2′-deoxyuridine. The synthesis of radioiodinated 2′-deoxyuridine was achieved in one step in the presence of Iodogen in 50% yield after isolation by reverse phase high performance column chromatography. The radiochemical purity was greater than 99%. The ease and rapidity of both preparation and isolation of no-carrier-added 5-[^123/125I]iodo-2′-deoxyuridine, as well as the absence of any starting material, suggests that radiohalodemercuration may be the method of choice for this and structurally similar compounds.     

Simple production of 77Br− and 123I− and their use in the labelling of [77Br]BrUdR and [123I]IUdR

Excitation functions for ⁷⁷Kr- and ¹²³Xe-production via the similar reactions Br(p,xn)⁷⁷Kr and¹²⁷I(p,5n)¹²³Xe, as well as their main radionuclide impurities (⁷⁶Kr, ⁷⁹Kr, ¹²¹Xe, ¹²²Xe, and ¹²⁵Xe), were studied in the proton energy ranges, 20–80 MeV (⁷⁷Kr) and 40–100 MeV (¹²³Xe). Thin targets (2–3 MeV) of NaBr and NaI were used and irradiated in the internal beam of the Uppsala synchrocyclotron. A simple technique of separating the radioactive gases from target was used. Optimal production conditions of ⁷⁷Br⁻ and ¹²³I⁻ were considered. A simple labelling technique of [⁷⁷Br]BrUdR and [¹²³I]IUdR is presented.     

Uptake of 3-[125I]iodo-α-methyl-l-tyrosine into colon cancer DLD-1 cells: characterization and inhibitory effect of natural amino acids and amino acid-like drugs

IntroductionWe examined 3-[¹²³I]iodo-α-methyl-l-tyrosine ([¹²³I]IMT) uptake and inhibition by amino acids and amino acid-like drugs in the human DLD-1 colon cancer cell line, to discuss correlation between the inhibition effect and structure.MethodsExpression of relevant neutral amino acid transporters was examined by real-time PCR with DLD-1 cells. The time course of [¹²⁵I]IMT uptake, contributions of transport systems, concentration dependence and inhibition effects by amino acids and amino acid-like drugs (1 mM) on [¹²⁵I]IMT uptake were examined.ResultsExpression of system L (4F2hc, LAT1 and LAT2), system A (ATA1, ATA2) and system ASC (ASCT1) was strongly detected; system L (LAT3, LAT4) and MCT8 were weakly detected; and B⁰AT was not detected. [¹²⁵I]IMT uptake in DLD-1 cells involved Na⁺-independent system L primarily and Na⁺-dependent system(s). Uptake of [¹²⁵I]IMT in Na⁺-free buffer followed Michaelis–Menten kinetics, with a K_m of 78 μM and V_max of 333 pmol/10⁶ cells per minute. Neutral d- and l-amino acids with branched or aromatic large side chains inhibited [¹²⁵I]IMT uptake. Tyrosine analogues, tryptophan analogues, l-phenylalanine and p-halogeno-l-phenylalanines, and gamma amino acids [including 3,4-dihydroxy-l-phenylalanine (l-DOPA), dl-threo-β-(3,4-dihydroxyphenyl)serine (DOPS), 4-[bis(2-chloroethyl)amino]-l-phenylalanine and 1-(aminomethyl)-cyclohexaneacetic acid] strongly inhibited [¹²⁵I]IMT uptake, but l-tyrosine methyl ester and R(+)/S(?)-baclofen weakly inhibited uptake. The substrates of system ASC and A did not inhibit [¹²⁵I]IMT uptake except l-serine and d/l-cysteine.Conclusions[¹²⁵I]IMT uptake in DLD-1 cells involves mostly LAT1 and its substrates' (including amino acid-like drugs derived from tyrosine, tryptophan and phenylalanine) affinity to transport via LAT1. Whether transport of gamma amino acid analogues is involved in LAT1 depends on the structure of the group corresponding to the amino acid residue. Beta-hydroxylation may confer reduction of transport affinity of tyrosine analogues via LAT1.     

No-carrier-added radiosynthesis of [123I]HIPDM: N,N,N′-trimethyl-N′-(2-hydroxy-3-methyl-5-[123I]iodobenzyl)-1,3-propanediamine

The multi-millicurie production of the SPECT radiopharmaceutical N,N,N′-trimethyl-N′-(2-hydroxy-3-methyl-5-[¹²³I]iodobenzyl)-1,3-propanediamine ([¹²³I]HIPDM) in high specific activity is described. Using no-carrier-added electrophilic iododeprotonation reactions and HPLC purification, [¹²³I]HIPDM can be isolated in 70–76% radiochemical yield and specific activity >2000 Ci/mmol within an overall preparation time of 75 min. This methodology is readily adapted to the clinical setting, and eliminates the need for co-injection of macroscopic HIPDM in SPECT imaging procedures.     

Synthesis of 2-[123I and 124I]-iodoisonicotinic acid hydrazide—potential radiotracers for tuberculosis

The radiochemical syntheses of methyl 2-[¹²³I]-iodoisonicotinate, 2-[¹²³I]-iodoisonicotinic acid hydrazide and 2-[¹²⁴I]-iodoisonicotinic acid hydrazide was accomplished. Iodine-123 was incorporated in the methyl ester molecule by an exchange reaction in glacial acetic acid. The average efficiency of iodine exchange reaction was (92.6 ± 4.5)%. This radiotracer was extracted with ether and the solvent was evaporated. The residue was re-dissolved in anhydrous ethanol and treated with hydrazine under anhydrous conditions to obtain 2-[¹²³I]-iodoisonicotinic acid hydrazide. The overall radiochemical yield was 69%. Biodistribution data of both radio-tracers in male Sprague-Dawley rats were collected. This is the first report of SPECT radiopharmaceuticals which may be useful for differential diagnosis of intracranial masses (tuberculoma vs glioma), and CNS tuberculosis in immunosuppressed subjects.     

Intra-individual comparison of p-[<Superscript>123</Superscript>I]-iodo-L-phenylalanine and L-3-[<Superscript>123</Superscript>I]-iodo-α-methyl-tyrosine for SPECT imaging of gliomas

Objectives Radioactive amino-acids accumulate in gliomas even with an intact blood-brain-barrier. L-3-[¹²³I]-iodo-α-methyl-tyrosine (IMT) is well established for SPECT imaging of gliomas. Recently, we introduced p-[¹²³I]-iodo-L-phenylalanine (IPA) for the characterisation of brain lesions. This study compares both tracers in glioma patients. Methods Eleven patients with gliomas (1 WHO grade 1, 5 grade 2, 1 grade 3, 2 grade 4 gliomas, 1 unconfirmed upgrading and 1 post-therapeutic non-neoplastic lesion) underwent SPECT imaging with IPA (early and delayed acquisitions at 30 min and 3 h) and IMT (early only). Maximum tumour-to-brain ratios (TBR) were calculated using region-of-interest analysis to assess uptake of IMT and IPA. Imaging results were compared to histopathological findings. Results Early TBRs of IMT and IPA were strongly correlated (r = 0.828, p = 0.002). TBRs were higher for IMT than IPA (1.95±0.50 versus 1.79±0.42; p < 0.05), but independent from tumour cell density (p > 0.1). Visual interpretation by different observers was more concordant for IMT-SPECT than IPA-SPECT (kappa 1.0 versus 0.774). No differences in early TBRs were observed between low-grade and high-grade gliomas for IMT (1.97±0.53 versus 2.21±0.44, p > 0.5) or IPA (1.70±0.23 versus 2.21±0.56, p = 0.167) with a trend to higher TBRs in low-grade tumours for IMT (p = 0.093). In contrast to the known wash-out of IMT, we observed persistent accumulation of IPA in gliomas. Conclusions IPA shows lower TBRs than IMT, especially in low-grade tumours, so IMT should be preferred for the delineation of low-grade gliomas by SPECT imaging. Due to its prolonged retention, however, IPA remains promising for therapeutic use in gliomas after labelling with I-131. This work was supported by a grant from the “Deutsche Krebshilfe” (70-3024-He 1).     

Comparison of [123I]ß-CIT and [123I]IPCIT as single-photon emission tomography radiotracers for the dopamine transporter in nonhuman primates

Single-photon emission tomographic (SPET) imaging with the radiotracer [¹²³I]2-carbomethoxy-3-(4-iodophenyl)tropane ([¹²³I]-CIT) has been reported to be a useful in vivo measure of dopamine (DA) transporters. However, in addition to its high DA transporter affinity,-CIT also binds with high affinity to serotonin (5-HT) transporters. 2-Carboisopropoxy-3-(4-iodophenyl)tropane (IPCIT) has been demonstrated by in vitro studies to have higher selectivity for the DA transporter. We compared [¹²³I]-CIT and [¹²³I]IPCIT SPET imaging and plasma metabolite analyses in baboons to evaluate the potential advantages of [¹²³I]IPCIT for quantitative in vivo measurements of DA transporter densities. Both tracers had low levels (2% of total plasma¹²³I activity) of lipophilic radiolabeled metabolites at 420 min. [¹²³I]IPCIT had significantly higher binding to plasma proteins. The average percent free (nonprotein bound) [¹²³I]-CIT and [¹²³I]IPCIT were 52%±7% and 14%±6%, respectively. Region of interest uptake data were normalized by injected dose and body weight. Consistent with the high density of 5-HT transporters in the midbrain and the lower 5-HT transporter affinity of IPCIT, the normalized peak specific midbrain uptake of [¹²³I]-CIT (1.7±0.5) was higher than that of [¹²³I]IPCIT (0.4±0.2). Consistent with its greater lipophilicity, [¹²³I]IPCIT had higher nonspecific uptake, such that normalized cerebellar uptake of [¹²³I]IPCIT was about twice that of [¹²³I]-CIT. The ratio of specific to nonspecific uptake in striatum was greater for [¹²³I]-CIT compared to [¹²³I]IPCIT; however, striatal binding potentials and distribution volumes were not significantly different. In conclusion, [¹²³I]IPCIT demonstrated in vivo a higher DA transporter selectivity and higher level of nonspecific uptake.     

Diagnosis of maxillofacial tumor withl-3-[18F]-fluoro-α-methyltyrosine (FMT) PET: a comparative study with FDG-PET

OBJECTIVES: To compare L-3-[18F]-fluoro-a-methyltyrosine (FMT)-positron emission tomography (PET) and 2-[18F]-fluoro-2-deoxy-D-glucose (FDG)-PET in the differential diagnosis of maxillofacial tumors. METHODS: This study included 36 patients (16 males, 20 females; 31-90 years old) with untreated malignant tumors (34 squamous cell carcinoma, one mucoepidermoid carcinoma, one rhabdomyosarcoma) and seven patients (five males, two females; 32-81 years old) with benign lesions. In all patients, both FMT-PET and FDG-PET were performed within two weeks before biopsy or treatment of the lesions. To evaluate the diagnostic usefulness of FMT-PET and FDG-PET, visual interpretation and semiquantitative analysis were performed. PET images were rated according to the contrast of tumor uptake as compared with background, and were statistically analyzed. As a semiquantitative analysis, standardized uptake values (SUV) of the primary tumors were measured, and the SUV data were analyzed using receiver operating characteristic (ROC) curves. Results: The mean SUV of the malignant lesions were significantly higher than those of the benign lesions in both FMT-PET (2.62 +/- 1.58 vs. 1.20 +/- 0.30, p < 0.01) and FDG-PET (9.17 +/- 5.06 vs. 3.14 +/- 1.34, p < 0.01). A positive correlation (r = 0.567, p < 0.0001, n = 46) was noted between FMT and FDG. ROC analysis revealed that there was no statistically significant difference in SUVs between FMT and FDG for differentiating malignant tumors. In 27 of 36 patients, FMT-PET had better contrast of malignant tumor visualization to the surrounding normal structures by visual assessment (p < 0.005, binomial proportion test). CONCLUSIONS: Differential diagnosis of FMT-PET based on the uptake in maxillofacial tumors is equivalent to FDG-PET. However, the contrast of FMT uptake between maxillofacial tumors and the surrounding normal structures is higher than that of FDG, indicating the possibility of accurate diagnosis of maxillofacial tumors by FMT-PET.     

美国药典论坛收载的碘[^131I／^123I]苄胍注射液

介绍了美国药典论坛收载的碘「＾１３１Ｉ／＾１２３Ｉ」苄注射液标准。     

The stereoisomers of 17α-[123I]iodovinyloestradiol and its 11α-methoxy derivative evaluated for their oestrogen receptor binding in human MCF-7 cells and rat uterus,and their distribution in immature rats

We studied the potential of both stereoisomers of 17-[¹²³I]iodovinyloestradiol (E- andZ-[¹²³I]IVE) and of 11-methoxy-17-[¹²³I]iodovinyloestradiol (E-andZ-[¹²³I]MIVE) as suitable radioligands for the imaging of oestrogen receptor(ER)-positive human breast tumours. The 17-[¹²³I]iodovinyloestradiols were prepared stereospecifically by oxidative radio-iododestannylation of the corresponding 17-tri-n-butylstannylvi-nyloestradiol precursors. Competitive binding studies were performed in order to determine the relative binding affinity (RBA) of the unlabelled 17-iodovinyloes-tradiols for the ER in both human MCF-7 breast tumour cells and rat uterine tissue, compared with that of diethylstilboestrol (DES). Target tissue uptake, retention and uptake selectivity of their¹²³I-labelled analogues were studied in immature female rats. All four 17-iodovi-nyloestradiols showed high affinity for the ER in human MCF-7 cells, as well as rat uterus. Their RBA for the ER showed the following order of decreasing potency: RBA of DES >Z-IVE >Z-MIVE >E-MIVE E-IVE. Neither of these 17-iodovinyloestradiols showed any significant binding to the sex hormone binding globulin in human plasma. The biodistribution studies showed ER-mediated uptake in the uterus, ovaries and pituitary, that ofE- andZ-[¹²³I]MIVE being higher than that ofE- andZ-[¹²³I]IVE. High target-to-non-target tissue uptake ratios, especially at longer periods after injection (up to 24 h), were exhibited by both isomers of [¹²³I]MIVE. The uterus-to-blood uptake ratio was higher for^E-[¹²³I]MIVE. However, the uterus-to-fat uptake ratio appeared to be higher for theZ-isomer of [¹²³I]MIVE, especially at 24 h after injection. Metabolic properties and temperature effects, which play a more important role in vivo, probably cause the discrepancies seen between in vitro and in vivo binding results. On the basis of their in vitro binding properties and in vivo distribution characteristics we conclude thatE- andZ-[¹²³I]MIVE could be suitable radioligands for the diagnostic imaging of ER in human breast cancer. Therefore, further studies with these radioligands in mature normal and tumour-bearing rats are warranted.     

Relationship between striatal [123I]β-CIT binding and four major clinical signs in Parkinson’s disease

We investigated the correlation between clinical severity and striatal [123I]-CIT binding in 12 patients with Parkinson's Disease (PD: 6 men and 6 women, age: 65 +/- 7 years, Hoehn & Yahr stage: 1 to 3). The clinical severity of PD patients was measured with the Unified Parkinson's Disease Rating Scale (UPDRS) after withdrawal of antiparkinsonian medication at least 12 hours before assessment. [123I]beta-CIT binding in the caudate and putamen was measured at 3 hours [V'3 (day 1)], and at 24 hours [V'3 (day 2)) after tracer injection with small square ROIs. The specific striatal uptake index (day 2) was calculated with large square ROIs that encompassed the whole striatum. The best correlation (r = -0.82, p < 0.0012) was between putamenal V'3 (day 2) and the motor UPDRS scores. When the motor UPDRS scores were divided into four subscales, bradykinesia was the only sign that correlated significantly with putamenal V'3 (day 2) (r = -0.81, p < 0.002). [123I]beta-CIT SPECT is a useful marker of disease severity in PD with potential utility in the serial monitoring of disease progression.     

The dosimetry of iodine-123 labelled 2β-carbomethoxy-3β-(4-iodophenyl)tropane

This report documents the radiation dosimetry of iodine-123 labelled 2-carbomethoxy-3-(4-iodophenyl)tropane [¹²³I]-CIT in humans. The mean absorbed doses for various organs and the effective dose equivalent were estimated from whole-body scans, blood samples and single-photon emission tomography scans acquired up to 22 h after the injection of a known amount of tracer. The basal ganglia, the liver and the lower large intestinal wall received the highest mean absorbed doses of 0.270 mGy/MBq, 0.038 mGy/MBq and 0.034 mGy/MBq, respectively. The effective dose equivalent for adults was estimated using 11 organs and the ICRP-87 radiation dose model and was 0.031 mSv/MBq. The radiation dose to the basal ganglia limits the maximum injected activity of [¹²³I]-CIT to 185 MBq for a single study.     

[P-CH_3-~3H]-梭曼的合成

本文合成了〔P-CH_3-~3H〕-1,2,2-三甲基丙氧基甲膦酰氟(〔=P-CH_3-~3H〕-梭曼).放射比度1.4ci/mmol,放射化学纯度95%以上.