[So-called carcinosarcoma of the lung: A case report]

A 50-year-old male was admitted to our hospital because of an abnormal shadow in chest X-ray films. The diagnosis of adenocarcinoma was obtained by transbronchial brushing cytology. Right lower lobectomy with hilar and mediastinal lymph node dissection was performed. Histological examinations of the resected specimen showed that the tumor was composed predominantly of spindle-shaped cells containing scattered islands of moderately differentiated adenocarcinoma. Immunohistochemically, the spindle cells were positively stained by vimentin, keratin and epithelial membrane antigen, suggesting sarcomatous transformation of adenocarcinoma cells.

Grade II astrocytoma visualized by technetium-99m-ECD SPECT

We present a case of primary brain tumor demonstrating increased uptake of 99mTc-ECD. Astrocytoma (Grade II) showed significantly increased cerebral blood perfusion on dynamic images and homogeneously increased uptake on static images with 99mTc-ECD brain SPECT. There seems to be some difference in perfusion and mechanism of tumor uptake among the cerebral blood flow imaging agents (99mTc-ECD, 99mTc-HMPAO and [123I]-IMP) and 201TI-chloride.

A "changing stripe sign" in serial pulmonary perfusion imaging

A stripe sign in pulmonary perfusion imaging is reported to be predictive of the absence of pulmonary embolism in the specific area of the stripe sign, and generally does not change on serial pulmonary perfusion imaging. The authors present the case of a patient with a stripe sign that disappeared on serial perfusion imaging without a ventilation abnormality. A "changing stripe sign" may raise suspicion for the possible existence of acute pulmonary embolism.

Multitracer study on uptake and excretion of trace elements in rats

The multitracer technique was first applied to the investigation of the uptake and excretion behaviour of trace elements in rats. A multitracer solution, prepared by irradiation of a gold target with a 14N-beam from the RIKEN Ring Cyclotron, was orally administered to male Wistar rats. The uptake and excretion rates of 23 elements, Be, Mn, Co, Zn, As, Rb, Sr, Y, Zr, Ce, Pm, Eu, Gd, Tb, Er, Tm, Yb, Lu, Hf, W, Re, Ir and Pt, were simultaneously determined under strictly identical experimental conditions. For some of the elements, the results obtained were consistent with previous reports on uptake and excretion of the elements in animals. For the other elements, unique behaviour was revealed for the first time as described in the present work. These results show that the multitracer technique has excellent reliability and versatility for a comparative study of the uptake and excretion of many different elements in animals.

[Assessment of clinical utility of 111In-DTPA-IgG scintigraphy in the detection of inflammation/infection--a report of multicenter phase II clinical trials]

A Phase II clinical study was performed in patients with strongly suspected focal sites of inflammation/infection to investigate clinical utility of 111In-DTPA-IgG. Neither adverse effects nor abnormal laboratory changes were noted in the all cases. Out of 59 patients, the clinical utility was evaluated in 56 patients with a total of 67 suspicious sites (19 in thorax, 13 in abdomen and pelvis, 30 in musculoskeletal system, and 5 in other regions). True positive results were obtained in 100% of lesions in the thorax (13/13) and the musculoskeletal system (26/26). There were three false negative and five false positive results. Overall sensitivity and specificity was 94.0% and 70.6%, respectively. Most of the true positive scintigram with the best image quality was acquired at Day 1 or Day 2 post-injection. A dose of 80 MBq was considered to be a practical dose for imaging. Our study indicates that 111In-DTPA-IgG is a safe and promising imaging agent for the detection of inflammation/infection, and that it is reasonable to proceed with Phase III studies to further evaluate clinical utility of the agent.

Specificity and affinity of 26 monoclonal antibodies against the CA 125 antigen: first report from the ISOBM TD-1 workshop. International Society for Oncodevelopmental Biology and Medicine

The specificity of 26 monoclonal antibodies against the CA 125 antigen was investigated in two phases of the ISOBM TD-1 workshop. The binding specificity was studied using CA 125 immunoextracted by specific antibodies immobilized on various solid phases, or on the surface of human cell lines. Immunometric assays using all possible antibody combinations were used to study the topography of antibody binding sites on the antigen. We conclude that the CA 125 antigen carries only two major antigenic domains, which classifies the antibodies as OC125-like (group A) or M11-like (group B). One antibody, OV 197, showed binding specificity related to some of the OC125-like antibodies, but was classified into a separate group C. The OC125-like group of antibodies has four subgroups with different binding specificities. These are A1 = OC 125 and K 95, A2 = K 93, A3 = B43.13, and A4 = ZS 33, B27.1 and CCD 247. Binding of nonlabelled OC 125 or K 95 to CA 125 caused a marked increase in binding of labelled OV 197 to the complex. This conformational change was not observed with any other antibody combinations. Antibody B43.13 could form immunometric assay combinations particularly with antibodies of subgroup A4, indicating that the B43.13 epitope is in the periphery of the binding area of OC125-like antibodies. The M11-like group of antibodies is more homogenous with strong cross-inhibition between most antibodies. Only one antibody, ZR 38, would form an immunoassay combination with other M11-like antibodies and thus represents a distinct subgroup. The main group of M11-like antibodies are M 11, ZR 45, MA602-6, K 91, OV 185, K 101, K 90, K 96, K 97, K 102, CCD 242, 145-9, and 130-22. Antibody OV 197 binds to a domain designated C and is unique, as stated above. Antibody pairs from any two of the three groups may be used in immunometric assays. Three antibodies were not studied by complete cross-inhibition due to low affinity (OV 198 and K 100) or lack of material (MA602-1). OV 198 and K 100 are most likely OC125-like and MA602-1 is M11-like. Antibody affinity was estimated with labelled antigen in solution or with antigen absorbed on microtiter wells. Western blot analysis showed staining both in the stacking gel and corresponding to a molecule of 200 kDa. There was a marked difference between the antibodies in their ability to bind to CA 125 immobilized on a membrane. Strongest binding was observed with the M11-like antibodies, particularly M 11, K 96, K 97, MA602-6, 145-9. Antibodies belonging to the subgroup A4 were the only OC 125-like antibodies which reacted well with CA 125 in Western analysis. Digestion of CA 125 with proteolytic enzymes showed it to be particularly sensitive to trypsin cleavage. However, no low molecular weight fragments with preserved immunoreactivity were found.

Inflammation-seeking scintigraphy with radiolabeled biotinylated polyclonal IgG followed by the injection of avidin chase

We tried to apply the avidin chasing system to the inflammation-seeking scintigraphy using radiolabeled nonspecific polyclonal IgG. We studied the pharmacokinetics of technetium-99m and iodine-125-labeled biotinylated murine polyclonal IgG followed by an avidin chase injection in model mice with inflammatory foci. Avidin chase decreased the circulating radioactivity of 99mTc and 125I, which was a major problem for inflammation-seeking scintigraphy using radiolabeled nonspecific polyclonal IgG, to 9.3% and 19.3% of that without an avidin chase injection, respectively. Inflammation-seeking scintigraphy with the aforementioned method would be better than that with conventional method.

Neoplastic transformation of normal rat embryo fibroblasts by a mutated p53 and an activated ras oncogene induces parathyroid hormone-related peptide gene expression and causes hypercalcemia in nude mice

Parathyroid hormone-related peptide (PTHRP) is a 141-amino acid protein identified in various carcinomas associated with humoral hypercalcemia of malignancy (HHM). Although the causal role of PTHRP in HHM syndrome has been established, the molecular and cellular mechanism by which PTHRP gene is overexpressed in certain malignancies remains unknown. We have demonstrated in the present study that PTHRP secretion was markedly induced concomitantly with the formation of transformed foci after normal rat embryo fibroblasts (REFs) were co-transfected with an activated ras (ras) and a mutated form of p53 (p53-mt) genes. In either ras- or p53-mt-transfected (nontransformed) cells, only modest or barely detectable secretion of PTHRP was observed, respectively. Northern blot analysis revealed that PTHRP mRNA was markedly induced in fully transformed cells 11 days after transfection with both ras and p53-mt genes. Inhibition of RNA synthesis with actinomycin D resulted in almost complete disappearance of PTHRP mRNA at 2-3 h, suggesting a transcriptional mechanism. Transient transfection experiments revealed that PTHRP promoter activity was induced in ras + p53-mt transfectants. REFs transformed by ras and p53-mt genes and thereby induced to secrete PTHRP in vitro produced aggressively growing tumors associated with HHM syndrome when injected into nude mice. These results suggest that activation of PTHRP gene is closely related to malignant transformation of normal mammalian cells and that ras and p53 may be important regulators of PTHRP gene transcription. The transfection-focus formation system of REFs should provide an excellent model to study the molecular and cellular mechanism underlying concomitant overexpression of PTHRP gene with carcinogenesis.

Presurgical diagnosis of a primary carcinoid tumor of the thymus with MIBG

A primary carcinoid tumor of the thymus showing ectopic ACTH syndrome was evaluated scintigraphically with four radiopharmaceuticals and a fluorescence method. Iodine-123-MIBG and 201Tl-Cl scintigraphy clearly demonstrated the tumor. Gallium-67-citrate and 99mTc(V)-DMSA showed no tumor uptake. The fluorescence method confirmed numerous storage granules of norepinephrine. Iodine-123-MIBG scintigraphy could be useful in the presurgical diagnosis of carcinoid tumors of the thymus.

[Biological features determining the chemosensitivity of gastric cancer]

We analysed the relationship between several biological properties of gastric cancers and their chemosensitivity determined by MTT assay. Higher chemosensitivity was associated with poor differentiation, aneuploidy, and higher proliferative activity. Lymph node metastasis was more chemosensitive than primary lesion, while liver metastasis was less. Gastric cancer expressing multidrug-resistance associated protein (MRP) showed lower sensitivity to several anticancer drugs, including adriamycin and etoposide. p53 status and susceptibility to apoptosis were also associated with chemosensitivity. Thus, chemosensitivity of clinical gastric cancer might be increased if these characters can be modified by some new biologic therapy.

[Response-oriented salvage chemotherapy with mitoxantrone, etoposide and enocitabine for previously treated acute myeloid leukemia. Tohoku Leukemia Study Group]

Twenty-two patients with previously treated acute myeloid leukemia (AML) received salvage chemotherapy with mitoxantrone, 5 mg/m2/d on days 1 to 3, etoposide, 70 mg/m2/d on days 1 to 5, and enocitabine, 170 mg/m2/d on days 1 to 7 (BHAC-ME). Additional mitoxantrone, etoposide (both for up to 2 days) and enocitabine (for up to 7 days) were given if the bone marrow obtained on day 8 was not severely hypoplastic. Mitoxantrone and etoposide had been previously administered in 14 and 15 patients, respectively. Seven patients had primary resistance; 14 patients had first relapse (4 early and 10 late): and 2 patients had second relapse. Overall, seven patients (31%) achieved a complete remission; 7/14 with first relapse, and 0/8 with primary resistance or second relapse. Four patients, 3 with primary resistance and 1 with first relapse, died of infectious complication in aplasia. First relapse patients who had been previously treated both with mitoxantrone and etoposide, had a lower CR rate than the other first relapse patients [2/8 (25%) vs 5/6 (86%)], although patient characteristics such as duration of first CR, initial karyotype, and performance status, were similar between the two groups. We conclude that response-oriented BHAC-ME regimen is still active in first relapse AML patients unless they have received both mitoxantrone and etoposide previously.

Chemical modification of metallic implant surfaces with biofunctional proteins (Part 1). Molecular structure and biological activity of a modified NiTi alloy surface

Human plasma fibronectin (pFN), an adhesive protein, was covalently immobilized onto an alkylaminosilane derivative of a NiTi substrate with glutaraldehyde through Schiff's base formation. The surface at different stages of the modification was characterized by X-ray photoelectron spectroscopy (XPS), and the amount of immobilized pFN was determined by a fluorometric method. The spreading behavior of human gingival fibroblasts was examined on the modified surface. The XPS spectra suggested that gamma-aminopropyltriethoxysilane (gamma-APS) was bonded to the surface through metallosiloxane bonds (Ti-O-Si) formed via a condensation reaction between the silanol end of gamma-APS and the surface hydroxyl group, with a highly cross-linked siloxane network formed after heat treatment of the silanized surface at 100 degrees C. The pFN was immobilized at the surface density of 1.1 micrograms.cm-2, and significantly promoted fibroblast spreading, suggesting that this chemical modification offers an effective means of controlling metal/cell interactions. These results may contribute to the development of bioactive metallic implants.

Chemical modification of metallic implant surfaces with biofunctional proteins (Part 2). Corrosion resistance of a chemically modified NiTi alloy

The corrosion resistance of a NiTi alloy, chemically modified with a human plasma fibronectin (pFN) using an aminosilane and a glutaraldehyde, was examined by electrochemical techniques in a 0.9% NaCl solution and a cell culture medium containing serum. The role of serum proteins in influencing the passive behavior of the alloy was extensively studied by anodic polarization and X-ray photoelectron spectroscopy (XPS). The passive current density increased in the presence of serum proteins. The enhanced dissolution of the passive film appears to be a consequence of quick adsorption of the serum proteins and the subsequent formation of metal ion-protein complexes on the film surface. With the chemical modification, the corrosion rate was reduced by approximately 50% in both solutions due to a highly cross-linked siloxane network formed on the alloy surface. This network layer limited the diffusion of dissolved oxygen, metal ions, and biological molecules involved in the corrosion reactions.

Magnetic resonance imaging study of the brain in aged volunteers: T2 high intensity lesions and higher order cortical function

The aims of the present study were to clarify the findings of magnetic resonance imaging (MRI) in the aging brain, and to relate the MRI findings to higher order cortical function. A total of 118 healthy aged volunteers (41 men, 77 women) underwent cranial MRI electroencephalography (EEG), Benton visual retention test (BVRT) and interview. The subjects had no past history or clinical evidence of cerebrovascular disorder, head trauma or dementia and were living at home without any difficulty. The majority of the subjects have participated in this series of studies since 1982. Using a 1.5 T superconductive MR instrument, T1-weighted, proton density and T2-weighted images were obtained. The MRI data were rated visually by regarding 12 items according to fixed criteria. T2 high signal intensity (T2HSI) lesions were found in 69.5% of subjects, the prevalence of which increased with age. T2HSI lesions were most frequently found in the basal ganglia (61.9%), followed by the thalamus (39.0%), parietal lobe (37.0%), temporal lobe (12.7%) and pons (8.5%). Among these lesions, lacunar infarction showed low signal intensity in T1-weighted images and was found in 24.6% of subjects, the prevalence also increasing with age. These findings, including brain atrophy determined according to similar criteria, were correlated closely with the subjects' age. The results of BVRT showed a close relation with T2HSI, suggesting that T2HSI may influence cognitive function. When the subjects were classified according to the presence of T2HSI, lacunar infarction and EEG abnormalities, brain atrophy was significantly milder in a group of subjects with T2HSI(-), lacunar infarction(-) and normal EEG than in the other groups. This suggests that changes seemingly representing physiological aging may be promoted by another pathological which also exerts influences on higher order cerebral function.

Inflammatory involvement of the hypophysis in Tolosa-Hunt syndrome

We report a case of painful ophthalmoplegia (Tolosa-Hunt syndrome), which was complicated with diabetes insipidus (DI) and pituitary-adrenal axis hypofunction. A 42-year-old man hospitalized for left orbital pain and impairment of left cranial nerves III, IV, V, VI, developed diabetes insipidus during the corticosteroid treatment. Neuroimaging studies disclosed a thickened, highly contrast-enhanced pituitary stalk, swollen pituitary gland and widened left cavernous sinus up to the superior orbital fissure, which were accompanied by diabetes insipidus and hypofunction of the pituitary-adrenal axis. These were indicative of an extension of granulomatous inflammation of the cavernous sinus to the pituitary portal system and the gland itself.

[Phase 3 multicenter clinical study of 111In-DTPA-D-octreotide (MP-1727) in patients with gastrointestinal hormone producing tumors]

A phase 3 multicenter clinical study was performed to investigate the efficacy, safety and usefulness of MP-1727, a novel tumor imaging agent which binds to somatostatin receptors, in 23 patients with gastrointestinal hormone producing tumor. The efficacy was graded effective or very effective in 16 cases (76.2%) out of 21 cases who could be evaluated. Positive predictive accuracy was 77.8% (7/9) for carcinoids, 100% (5/5) for gastrinomas and 40.0% (2/5) for insulinomas. In three cases, tumor lesions which had been unknown were detected by MP-1727 scintigraphy. The consistent ratio between scintigraphically positive sites and preinjection localizations was 82.0% (41/50 sites) in total. Although adverse drug reactions were observed in two cases, the safety was graded 'not problematic at all' in all of 23 cases. These results show that MP-1727 is a very useful radiopharmaceutical for detection and localization of gastrointestinal hormone producing tumors.

Alterations of effector cell molecule expression on neutrophils in granulocyte colony-stimulating factor-producing tumour

A 68-year-old man was diagnosed as having a granulocyte colony-stimulating factor (G-CSF)-producing mediastinal tumour. Mediastinotomy was performed, and thereafter the elevated leucocyte count and serum G-CSF concentration returned to the normal range. The surface expression of effector cell molecules on neutrophils was serially examined. Before operation, the expression of FcRI and CR1 was increased but the expression of FcRIII and L-selectin was reduced in the patient. The altered expression of these molecules returned to the normal levels after operation. These findings suggest that G-CSF produced by the tumour modulated neutrophil effector cell molecule expression in the patient.

Binding of vitamin D to low-density-lipoprotein (LDL) and LDL receptor-mediated pathway into cells

The present study was undertaken to identify serum components other than vitamin D-binding proteins that bind to 1,25(OH)2 D3, and its analog. The binding rate of 1,25(OH)2 D3, 22-oxa-1,25(OH)2D3 (OCT) or 25(OH) D3 to total lipoprotein(TLP) represented 16.7%, 4.65%, and 3.11% of total counts added, respectively. Polyacrylamide gel electrophoresis of the TLP revealed that 1,25(OH)2 D3 and OCT were associated with LDL. The binding studies of OCT-bound LDL to the fibroblasts showed specific pathway to the cells mediated by LDL-receptor. These findings may have important implications in understanding the mechanisms of the diverse biological actions of 1,25(OH)2 D3 and in designing a novel delivery system for vitamin D analogs.

Origin of posterior pituitary high intensity on T1-weighted magnetic resonance imaging. Immunohistochemical, electron microscopic, and magnetic resonance studies of posterior pituitary lobe of dehydrated rabbits

RATIONALE AND OBJECTIVES

To investigate the origin of posterior pituitary high intensity (PPHI) seen on T1-weighted magnetic resonance (MR) images.

METHODS

Six rabbits, including four rabbits deprived of drinking water for 4 days and two control rabbits, were examined by MR imaging. Plasma vasopressin levels were sequentially measured by radioimmunoassay. Pituitary glands were immunostained with guinea pig anti-rabbit vasopressin antibody, and ultrathin sections of Epon/Araldite-embedded specimens were observed with a transmission electron microscope.

RESULTS

In control rabbits, PPHI was noted on T1-weighted MR images, and the posterior pituitary lobe was positively immunostained with anti-vasopressin antibody. At the ultrastructural level, nerve terminals contained numerous neurosecretory granules bearing vasopressin. Conversely, plasma vasopressin levels gradually increased and PPHI was absent in 4-day dehydrated rabbits. The posterior lobe was scarcely stained with anti-vasopressin antibody, and neurosecretory granules were rarely observed. However, a number of small dispersed vesicles, possibly derived from the fragmentation of neurosecretory granule envelopes, were seen in the nerve terminal.

CONCLUSIONS

Posterior pituitary high signal seen on T1-weighted MR images is attributed to neurosecretory granules bearing vasopressin.

Synthesis and preliminary evaluation of [11C]KF15372, a selective adenosine A1 antagonist

As a radioligand for mapping the presynaptic adenosine A1 receptors in the central nervous system by PET, [1-propyl-11C]8-dicyclopropylmethyl-1,3-dipropylxanthine ([11C]KF15372), a selective adenosine A1 antagonist, was prepared by the reaction of 8-dicyclopropylmethyl-3-propylxanthine and [11C]propyl iodide with decay-corrected radiochemical yield of 5% based on the [11C]propyl iodide, radiochemical purity of > 99%, sp. at. of 10-56 GBq/mumol and preparation time of 45-55 min. Another 11C-labeled A1 antagonist with much lower affinity for the A1 receptors, 7-[11C]methyl-KF15372 ([11C]KF17109), was also prepared using [11C]methyl iodide with a decay-corrected radiochemical yield of > 50%. In mice, the brain uptake of [11C]KF15372 (1.91% ID/g at 5 min) decreased gradually with time. Carrier KF15372 competitively reduced the brain uptake to a level (43% of the control) comparable to the brain uptake of [11C]KF17109. On the other hand, an A2 antagonist 3,7-dimethyl-1-propargylxanthine showed no effect on the brain uptake of [11C]KF15372. The results show that [11C]KF15372 has potential as a PET radioligand for mapping the adenosine A1 receptors and that [11C]KF17109 may be a reference compound reflecting the non-specific uptake of the [11C]KF15372.

[Medical image transmission via communication satellite: evaluation of bone scintigraphy]

As compared with terrestrial circuits, the communication satellite possesses superior characteristics such as wide area coverage, broadcasting, high capacity, and robustness to disasters. Utilizing the narrow band channel (64 kbps) of the geostationary satellite JCSAT1 located at the altitude of 36,000 km above the equator, the authors investigated satellite-relayed medical images by video signals, with bone scintigraphy as a model. Each bone scintigraphy was taken by a handy-video camera, digitalized and transmitted from faculty of technology located at 25 kilometers apart from our department. Clear bone scintigraphy was obtained via satellite, as seen on the view box. Eight nuclear physicians evaluated 20 cases of bone scintigraphy. ROC (Receiver Operating Characteristic) analysis was performed between the scintigraphies on view box and via satellite by the rating method. The area under the ROC curve was 91.6 +/- 2.6% via satellite, and 93.2 +/- 2.4% on the view box and there was no significant difference between them. These results suggest that the satellite communication is very useful and effective system to send nuclear imagings to distant institutes.

[Current status of nuclear oncology in Japan]

The most commonly used radionuclides for cancer patients in Japan have been still 67Ga and 201T1 chloride. In addition to the diagnosis of lung cancer and thyroid tumor, 201T1 is recently applied to patients with brain tumor, bone and soft tissue tumor and parathynoid adenoma. Comparing to Nuclear Cardiology and Brain Nuclear Medicine, where many new radiopharmaceuticals have been developed, there are few new drugs in Nuclear Oncology. In other words, new radiopharmaceuticals are expected to be developed for the diagnosis and/or therapy of cancer. In addition to 131I for thyroid cancer, new radiopharmaceuticals such as 111In-octreotide and 99mTc(V)-DMSA have been clinically employed. In spite of strong expectation, radiolabeled monoclonal antibodies have not been clinically used in Japan. However, the technique of humanized antibodies has been established and in U.S.A., 131I-labeled antibodies are reported to be effective for the treatment of malignant lymphoma. 89Sr is useful for the relief of bone pain caused by the bone metastasis. New findings that SPECT of 18F-FDG, a positron emitter, has been revealed to have a great potential in the management of cancer patients, will give a great impact on Nuclear Oncology.

Repeating the avidin "chase" markedly improved the biodistribution of radiolabelled biotinylated antibodies and promoted the excretion of additional background radioactivity

Immunoscintigraphy using radiolabelled biotinylated monoclonal antibodies followed by infusion of avidin as a "chase" has been recently reported to improve the biodistribution for both immunoscintigraphy and radioimmunotherapy. In this study the circulating protein-bound and avidin-binding fractions of radiolabelled biotinylated antibodies were determined serially after injection of an avidin "chase", and the effect of repeating the avidin chase was also studied. Nude mice bearing KT005 human osteogenic sarcoma were injected with radiolabelled biotinylated antitumour monoclonal antibody (OST7). After injection of an avidin chase, the protein-bound and avidin-binding fractions in plasma were determined serially using the trichloroacetate method and avidin-Sepharose gel. The biodistribution of radiolabelled biotinylated OST7 was compared after single and double avidin chases with no chase. At 6 h after the first avidin chase in mice injected with radioiodinated and technetium-labelled biotinylated OST7, 67.7% and 67.8%, respectively, of the plasma radioactivity was available for binding to avidin and was cleared from the circulation. Reinjection of avidin decreased the plasma radioactivity and improved the biodistribution of the radiolabelled biotinylated antibodies. Repeating the avidin chase markedly improved the biodistribution of the radioiodine-labelled biotinylated antibody when compared with the use of a single avidin chase. This new method for radioimmunotherapy is sure to protect the critical organs from radiation injury without decreasing the therapeutic effect.

[Unilateral effective renal plasma flow measurement using one-compartment analysis of 99mTc-MAG3 and gamma-camera renography]

The aim of this study was to establish a simple and accurate procedure to calculate the unilateral effective renal plasma flow (ERPF) using 99mTc-MAG3 gamma-camera renographyl. Eleven patients with urological disorders were studied with 99mTc-MAG3 to calculate the renal uptake ratio (RUR), which was defined as the ratio of absorption-corrected renal counts within 1-2 min after intravenous injection to injection radioactivity measured with a gamma-camera. We assumed that 99mTc-MAG3 was distributed in the circulation, moved from the circulation to the kidneys, and was excreted solely from the kidneys. We thus adopted an one-compartment model to calculate 99mTc-MAG3 clearance (CLMAG) using RUR. Sequential p-aminohippurate (PAH) clearance study was performed as a gold standard in all the patients to compare CLMAG and PAH clearance. Obtained CLMAG correlated well with PAH clearance, and this one-compartment model seemed appropriate for describing CLMAG. Unilateral ERPF was accurately measured within two minutes after the intravenous injection of 99mTc-MAG3 in conjunction with the renal imaging study. This procedure is simple and reliable, and requires no blood or urine sampling.