On-line [11C]methylation using [11C]methyl iodide for the automated preparation of 11C-radiopharmaceuticals

A novel method for the efficient preparation of ¹¹C-radiopharmaceuticals by on-line [¹¹C]methylation using [¹¹C]methyl iodide has been developed and applied to a rapid, convenient automated system. [¹¹C]Methyl iodide is first trapped in a short column, containing an adsorber and coated substrate, which is connected to an HPLC injector. DMF is then introduced. Alternatively the substrate is added with the DMF. A whole reaction mixture can be easily injected onto an HPLC column for purification by switching the injector valve immediately after the reaction. Thus, radiochemical yields in the preparation of ¹¹C-labeled doxepin, benztropine, cyproheptadine and N-methylspiperone have been improved remarkably and the synthetic procedure simplified.     

Localization of melanoma with radiolabelled monoclonal antibody fragments and iodoamphetamine

In two melanoma patients, metastases accumulated both ^99mTc-labelled monoclonal anti-tumor F(ab)₂ fragments and N-isopropyl-p-(¹²³I)-iodoamphetamine. Small metastatic deposits were localized only by labelled antibody, for which a higher target-to-nontarget ratio was observed than for radioiodoamphetamine, indicating that immunoscintigraphy may be the more sensitive method. In these two patients positive immunohistochemical staining for the antibody used was observed, whereas in a third patient, with no concentration of labelled antibody, the staining result was negative showing the specificity of the immunoscintigraphy findings. It is possible that the accumulation of radio-iodoamphetamine is due to binding to melanin but this is not certain as tissue samples from one of the two patients with positive scintigrams did not contain stainable melanin.     

Localization of melanoma with radiolabelled monoclonal antibody fragments and iodoamphetamine

In two melanoma patients, metastases accumulated both 99mTc-labelled monoclonal anti-tumor F(ab')2 fragments and N-isopropyl-p-(123I)-iodoamphetamine. Small metastatic deposits were localized only by labelled antibody, for which a higher target-to-nontarget ratio was observed than for radioiodoamphetamine, indicating that immunoscintigraphy may be the more sensitive method. In these two patients positive immunohistochemical staining for the antibody used was observed, whereas in a third patient, with no concentration of labelled antibody, the staining result was negative showing the specificity of the immunoscintigraphy findings. It is possible that the accumulation of radio-iodoamphetamine is due to binding to melanin but this is not certain as tissue samples from one of the two patients with positive scintigrams did not contain stainable melanin.     

Localization of parathyroid adenomas using 11C-methionine positron emission tomography

BACKGROUND AND AIM: In symptomatic hyperparathyroidism, pre-surgical localization of the suspected site of adenoma is desirable. All widely available techniques may have difficulty in localizing the site. The aim of this study was to determine whether 11C-methionine positron emission tomography (PET) could accurately localize parathyroid adenomas in patients in whom conventional imaging had failed. PATIENTS AND METHODS: Fifty-one patients presenting with hyperparathyroidism, and in whom other imaging techniques had failed to definitely identify the site of adenoma, were reviewed retrospectively after 11C-methionine PET scanning. Patients were followed up by surgical histology, or clinically if surgery was not performed. RESULTS: 11C-Methionine PET scanning was found to have a sensitivity of 83%, a specificity of 100% and an accuracy of 88% in successfully locating parathyroid adenomas. Most false negatives were due to adenomas in the lower mediastinum that was outside the area of scanning. CONCLUSIONS: 11C-Methionine PET is a reliable and highly accurate technique for localizing parathyroid adenomas in patients in whom conventional imaging techniques have failed. It is necessary to image to the level of the lower mediastinum.     

原发鼻腔恶性黑色素瘤11例临床分析

目的观察鼻腔原发性恶性黑色素瘤的临床特点,以帮助临床诊断和治疗。方法对1992—2007年12月间诊治的鼻腔原发性恶性黑色素瘤11例临床资料进行回顾性分析。结果 11例中,肿瘤多位于鼻腔外侧壁和鼻中隔,其中中鼻道5例,鼻中隔4例,中鼻甲1例,下鼻甲1例,肿瘤呈黑色或紫褐色8例,呈结节状或菜花状,淡红色表面光滑如息肉状3例;肿瘤触之易出血。结论本病临床少见,易误诊,应与鼻腔癌、血管瘤、鼻息肉相鉴别。对鼻腔发现的黑色或紫褐色肿物,触之易出血者可作该病的临床诊断,而不必取活检,以免促进肿瘤转移。     

Uptake of 123I-5-iodo-2-thiouracil, a possible radiopharmaceutical for noninvasive detection of ocular melanoma, in melanotic and amelanotic melanomas in hamsters

The uptake of 123I-5-iodo-2-thiouracil in melanotic and amelanotic melanoma implanted in Syrian golden hamsters was studied. A selective accumulation was found in the tumours. Uptake of 123ITU in melanotic melanomas was 4 to 5 times the uptake in amelanotic ones. For both tumours high ratios of tumours versus non-tumour were found. The high accumulation of 123ITU in both kinds of tumours and the high tumour versus non-tumour ratios suggest that 123ITU may be a promising radiopharmaceutical for the detection of ocular melanoma.     

Tumor imaging with carbon-11 labeled alpha-aminoisobutyric acid (AIB) in a patient with advanced malignant melanoma

A 29 year-old-man presenting with advanced metastatic malignant melanoma was successfully imaged using carbon-11 (11C) labeled alpha-aminoisobutyric acid (AIB), a synthetic, non-metabolized amino acid transported into viable cells by the A-type, or alanine-preferring, amino acid transport system. Tumor located in the hilum of the lung was well visualized with 11C-AIB prior to chemotherapy. A gallium image with liver subtraction using 99mTc-sulfur colloid demonstrated regions of increased activity in liver which correlated with regions of increased activity on the 11C-AIB liver image.     

Tumor imaging with carbon-11 labeled alpha-aminoisobutyric acid (AIB) in a patient with advanced malignant melanoma

A 29 year-old-man presenting with advanced metastatic malignant melanoma was successfully imaged using carbon-11 (¹¹C) labeled alpha-aminoisobutyric acid (AIB), a synthetic, non-metabolized amino acid transported into viable cells by the A-type, or alanine-preferring, amino acid transport system. Tumor located in the hilum of the lung was well visualized with ¹¹C-AIB prior to chemotherapy. A gallium image with liver subtraction using ^99mTc-sulfur colloid demonstrated regions of increased activity in liver which correlated with regions of increased activity on the ¹¹C-AIB liver image.     

Rapid imaging of human melanoma xenografts using an scFv fragment of the human monoclonal antibody H11 labelled with 111In

H11 is a human IgM monoclonal antibody which recognizes a novel tumour-associated antigen expressed on melanoma, glioma, breast cancer, colon cancer, prostate cancer, lung cancer and B-cell lymphoma. In this study, a recombinant single-chain Fv (scFv) fragment of H11 labelled with 111In was investigated for tumour imaging in athymic mice implanted subcutaneously with A-375 human melanoma xenografts. H11 scFv was derivatized with diethylenetriaminepentaacetic acid (DTPA) for labelling with 111In. The immunoreactivity of DTPA-H11 scFv against A-375 cells in vitro ranged from 23% to 36%. 111In-DTPA-H11 scFv was rapidly eliminated from the blood and most normal tissues (except the kidneys) reaching maximum tumour/blood ratios of 12:1 at 48 h post-injection. Tumours were imaged as early as 40 min after injection. The kidneys accumulated the highest concentration of radioactivity (up to 185% injected dose/g). Tumour uptake was 1-3% injected dose/g. The whole-body radiation absorbed dose predicted for administration of 185 MBq of 111In-DTPA-H11 scFv to humans was 37 mSv. The radiation absorbed dose estimates for the kidneys, spleen and intestines were 405 mSv, 698 mSv and 412 mSv, respectively. The results of this preclinical study and a concurrent phase I trial suggest a promising role for H11 scFv for tumour imaging.     

Fluorodeoxyglucose-PET in the management of malignant melanoma

FDG-PET is of limited use in patients with early-stage disease without nodal or distant metastases (stage I-II), because sentinel node biopsy is much more sensitive in detecting microscopic lymph node metastases. Because of the high tumor-to-background ratio, FDG-PET can highlight metastases at unusual sites that are easily missed with conventional imaging modalities. PET has been shown to have a strong role in detecting metastatic disease. FDG-PET is more sensitive than CT for detecting metastatic lesions in skin, lymph nodes, and abdomen, but CT is equivalent to or more sensitive than FDG-PET for detecting small pulmonary lesions. FDG-PET identifies the location and number of metastatic lesions in stage III and IV disease and therefore is important for surgical planning. Most of the false-negative FDG-PET results are caused by micrometastases and lesion smaller than 10 mm. Postsurgical inflammation, other inflammatory lesions, and some benign tumors cause some false-positive FDG-PET results.     

Immunoscintigraphy in the diagnosis of choroid melanoma

This study was aimed at evaluating the role of 99mTc-labelled anti-melanoma antibodies as in vivo tumor markers in the diagnosis of uveal melanomas. Usually, neither conventional semeiological techniques nor more recent diagnostic imaging methods allow a differential diagnosis to be made of benign and malignant intra-ocular tumors. Immunoscintigraphy was employed to examine 9 patients with monolateral reduction of sight, and photopsy. All patients were previously submitted to funduscopy, fluorescein angiography, and US. Four hours after iv injection of 370 MBq of 99mTc F(ab1)2, we obtained 500,000-count images of skull, abdomen, and thorax, with a computerized gamma camera equipped with a general-purpose collimator. A SPET of the head followed the conventional examination. Our first results seem promising enough for further study to be carried out to assess immunoscintigraphy specificity in the diagnosis of uveal melanoma.     

The metabolism of radiohafnium in marmosets and hamsters

The whole body retention of 181Hf was studied in marmosets (Callithrex jacchus) and found to be closely similar to that in rats and Chinese hamsters. Limited tissue distribution studies suggest a higher uptake in liver and much lower deposition in skin and muscle in the marmoset as compared to the rat or Chinese hamster. Studies in Chinese hamsters showed that treatment with the chelating agent diethylenetriaminepentaacetic acid resulted in only a small reduction in the whole body retention of 181Hf. The absorption of orally administered 181Hf, in various chemical forms, was found to be between 0.04 and 0.13% of the ingested dose and was unaffected by age between 5 and 21 months but was increased by fasting. The measured absorption of 181Hf in Chinese hamsters and in rats was similar to that of plutonium suggesting that radiohafnium could be used as a surrogate for plutonium for selected studies in human volunteers.