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Biomedical subjects

K Tomiyoshi

Publications and source records attributed to K Tomiyoshi.

At least 19 recordsLinked to original sources
PubMed2003

Gliomatosis cerebri evaluated by 18Falpha-methyl tyrosine positron-emission tomography.

Gliomatosis cerebri is a rare condition in which an infiltrative glial neoplasm spreads through the brain with preservation of the underlying structure. CT and MRI show diffuse abnormal density or signal, without mass effect, and because these findings are nonspecific, it is difficult to make a definitive diagnosis. Our purpose was to assess the usefulness of a new tumour-detecting amino acid tracer for positron-emission tomography (PET), L-[3-(18)F] alpha-methyl tyrosine (FMT), in patients with gliomatosis cerebri. We performed FMT PET, fluorodeoxyglucose FDG PET and MRI eight patients with gliomatosis cerebri and six with non-neoplastic disease, whose MRI also showed diffuse high signal on T2-weighted images. Standardised uptake (SUV) of FMT and FDG in the area of gliomatosis was obtained and the tumour-to-normal cortex (T/N) ratio of this was compared. The tumours were shown on FMT PET as areas of increased uptake, except in one patient with severe intracranial hypertension. There were significant differences between the SUV of FMT and the T/N ratio of FMT in patients and in controls (both P<0.01), and between the T/N ratio of FMT and FDG in patients ( P<0.01). Increased uptake of FMT PET strongly suggests neoplasia. FMT PET is valuable for differentiating gliomatosis cerebri from non-neoplastic diseases showing similar diffuse high signal on T2-weighted images and little contrast enhancement.

Adult↗
PubMed2001

Usefulness of dual-head coincidence gamma camera with thick NaI crystals for nuclear oncology: comparison with dedicated PET camera and conventional gamma camera with thin NaI crystals.

AIM: A comparative study of the images obtained with a dual-head coincidence gamma camera with thick NaI crystals (19 mm), a dedicated PET camera with BGO crystals and a conventional gamma camera with thin NaI crystals (9.5 mm) was conducted to clarify the clinical feasibility of a dual-head coincidence gamma camera with thick NaI crystals. METHODS: FDG images of 27 patients with malignant tumors were obtained by means of a dual-head coincidence gamma camera with thick NaI crystal and a dedicated PET camera with BGO crystals. The images of bone scintigraphy in 10 cancer patients obtained with the dual-head coincidence gamma camera were compared with those taken by a conventional dual-head gamma camera with thin NaI crystals. RESULTS: Patient-basis sensitivity in 27 patients with neoplasms and lesion-basis sensitivity of the dual-head coincidence gamma camera and the dedicated PET camera were 74.1% and 85.2% (n.s.), 66.7% and 72.2% (n.s.), respectively. The tumor to background FDG uptake ratio derived from the coincidence gamma camera was significantly lower than that derived from the dedicated PET camera (mean +/- s.d.; 3.48 +/- 3.77 vs. 8.12 +/- 8.92, p < 0.0001), but the tumor to background FDG uptake ratio obtained with both methods correlated well (r = 0.84, p < 0.001). Similar whole body bone scans were obtained with the dual-head coincidence gamma camera and the conventional dual-head gamma camera in all 10 patients. CONCLUSION: These results suggest that the dual-head coincidence gamma camera with thick NaI crystals has potentially high clinical applicability for community hospitals.

Adult↗
PubMed2001

Nuclear imaging of bone tumors: FDG-PET.

Positron emission tomography (PET) has become a very useful adjunct to anatomic imaging techniques, because it can provide an in vivo method for quantifying functional metabolism in normal and diseased tissues. Clinical trials with [(18)F] 2-deoxy-2-fluoro-D-glucose (FDG), the most commonly used radiolabeled tracer for PET imaging, has demonstrated increased accumulation of FDG in cancer tissue. FDG-PET is now widely used for the detection, differentiation, grading, staging, and monitoring of various neoplasms. However, the significance of FDG-PET in such evaluations of primary bone tumors and tumor-like lesions has not been extensively elucidated. In this article, we present recent advances in FDG-PET studies for evaluating primary bone tumors and tumor-like lesions.

Bone Neoplasms↗
PubMed2001

Detection of malignant tumors: whole-body PET with fluorine 18 alpha-methyl tyrosine versus FDG--preliminary study.

PURPOSE: To compare the diagnostic potential of whole-body positron emission tomography (PET) with fluorine 18 alpha-methyl tyrosine (FMT) with that of whole-body PET with 2-[fluorine 18]fluoro-2-deoxy-D-glucose (FDG). MATERIALS AND METHODS: Nineteen patients with or suspected of having malignant tumors and five healthy volunteers underwent whole-body PET with FMT and FDG. RESULTS: In comparison with FDG uptake, FMT uptake was significantly less in the brain, heart, lung, liver, and spine. On a lesion-by-lesion basis, the sensitivity of whole-body FMT PET for depicting malignant tumors was inferior to that of whole-body FDG PET, but this difference was not statistically significant (74% [26 of 35 lesions] vs 91% [32 of 35 lesions], P >.05). The positive predictive value of FMT PET was superior to that of FDG PET (87% [26 of 30 lesions] vs 63% [32 of 51 lesions], P <.001). The difference in uptake between benign and malignant lesions was significant with FMT PET (mean +/- SD, 1.64 +/- 0.96 vs 0.79 +/- 0.23; P <.001) but not with FDG PET (5.02 +/- 3.56 vs 4.02 +/- 2.90, P >.05). CONCLUSION: Whole-body FMT PET is clinically useful in the diagnosis of malignant tumors and may be effective in the depiction of primary and metastatic lesions in the cardiac region or in the brain.

Adult↗
PubMed2000

PET imaging of musculoskeletal tumours with fluorine-18 alpha-methyltyrosine: comparison with fluorine-18 fluorodeoxyglucose PET.

Fluorine-18 labelled alpha-methyltyrosine (FMT) was developed for positron emission tomography (PET) imaging, and its potential for clinical application in patients with brain tumours has been demonstrated. This is the first trial to compare FMT with 18F-fluoro-2-deoxy-D-glucose (FDG) for the evaluation of musculoskeletal tumours. Seventy-five patients were examined with both FMT- and FDG-PET within a 2-week period. Imaging findings were visually inspected in conjunction with computed tomography and/or magnetic resonance imaging, and standardized uptake values (SUVs) for both FMT and FDG in lesions were also generated and compared with histological findings. A significant correlation between FMT and FDG SUVs was found for all lesions (r=0.769, P<0.0001), and mean values for malignant tumours were significantly higher than those for benign lesions in both FMT- and FDG-PET. The diagnostic sensitivities and specificities for malignancy were 72.7% and 84.9%, respectively, using FMT with a cut-off SUV of 1.2, and 72.7% and 66.0%, respectively, using FDG with a cut-off SUV of 1.9. The resultant accuracy with FMT was 81.3%, higher than that for FDG (68.0%), and the difference with respect to specificity was significant (chi2cal=5.0625, P<0.05). On the other hand, while a significant correlation was found between malignant tumour grade and SUV with both FMT- (rho=0.656) and FDG-PET (rho=0.815), only the latter demonstrated significant differences among grades I, II and III. FMT and FDG for PET appear equally effective at detecting musculoskeletal tumours. In evaluating musculoskeletal tumours, FMT may be superior to FDG in the differentiation between benign and malignant tumours, while FDG may be the better choice for non-invasive malignancy grading.

Adolescent↗
PubMed2000

Tritium in [15O]water, its identification and removal.

The present investigation was undertaken to identify the long-lived radionuclide and its chemical forms existing in [15O]water which was synthesized from 15O produced by the nuclear reaction 14N(d,n)15O, and to develop a method for its removal to facilitate radioactive waste disposal. The long-lived nuclide was identified as tritium based on a comparison of its physical half-life and the energy spectrum of beta-rays with those of tritium. The major chemical form of tritium in the target gas was estimated to be molecular hydrogen. The tritium radioactivity was completely removed without a serious loss occurring to the yield of [15O]water by passing the irradiated target gas over a heated palladium catalyst followed by a calcium chloride column before the final synthesis of the [15O]water. This provided a practical way of removing tritium from the [15O]water.

Cesium Radioisotopes↗
PubMed1999

Performance stability of SHR-2000 high resolution PET for animal research.

The performance of a high resolution positron emission tomography (PET) system SHR-2000 for animal studies was re-evaluated six years after its installation. The system employs a detector array consisting of BGO crystals that are 1.7 mm (transaxially) by 10 mm (axially) by 30 mm (deep). A block detector, which is a position-sensitive photomultiplier tube (PMT) coupled to 4 arrays of BGO crystals has been adopted to the system. There are 15 block detectors positioned to form a 35 cm diameter ring with a field of view (FOV) of 17 cm by 4.6 cm axially, giving the system a 7 slice imaging capability. For six year workload in spatial resolution (FWHM), there were approximately a 2.6% increase at tangential FOV and a 7.5% increase at radial FOV. In axial resolution (FWHM) there was almost no change. The count rate loss for the true count rate increased 1.3% at 200 kBq/ ml. The average slice sensitivity showed a decrease of approximately 4.1%, and in scatters it showed an increase of approximately 1.4%. In animal experiments, the bones of guinea pigs were clearly identified with 18F fluoride ion. These experiments show that after a six year workload, the system also maintains good performance and has good stability.

Animals↗
PubMed1999

Metabolic studies of [18F-alpha-methyl]tyrosine in mice bearing colorectal carcinoma LS-180.

Brain and tumor uptake of [18F-alpha-methyl]tyrosine (18F-AMT) and the incorporation into each of four fractions (lipid, RNA, DNA and protein) were investigated in mice bearing LS180 colorectal carcinoma. Homogenized tissues were analyzed by the fractionation method into an acid-soluble fraction (ASF) and an acid-precipitable fraction (APF). The APF was further investigated to assess the incorporation of 18F-AMT into each fraction. Incorporation into four fractions of brain and tumor at 60 min post-injection was 20 and 12%, respectively; 10% of the activity was incorporated to lipid in brain and 5% in tumor. There was 5, 2 and 2% incorporation with RNA, DNA and protein, respectively. Metabolites in ASF were analyzed by high-performance liquid chromatography and thin-layer chromatography. There was only one radioactive peak, which corresponded to 18F-AMT. The incorporation of 18F-AMT into lipid was twice that of 18F-AMT in tumor. The uptake of 18F-AMT in tissues was rapid and accomplished before 30 min, and then slowly diffused in blood. These results implied that 18F-AMT was metabolized to protein to only a small extent and trapped as intact 18F-AMT in cells up to 60 min. We conclude that 18F-AMT is a promising tracer for tumor imaging and quantification of the transport rate using two-compartment models.

Animals↗
PubMed1999

Biodistribution studies of the 186Re complex of 3-amino-1-hydroxypropylidene-1,1-bisphosphonic acid in mice.

Preliminary studies of 186Re-labelled 3-amino-1-hydroxypropylidene-1, 1-bisphosphonic acid (APD) were performed to determine its potential for bone pain palliation, and as a treatment for increased bone resorption. The synthesis of 186Re-APD was carried out by reduction of 186Re-perrhenate in the presence of SnCl2. The APD kit, comprising 2.5 mg of APD, 2.5 mg of gentisic acid and 1 mg of Sn++ as SnCl2 2H2O, was prepared in-house. The APD was labelled with 186Re and injected intravenously into normal mice. Mice were subsequently sacrificed at 1, 3, 24, 48, 72, 168 and 240 h post-injection. The greatest accumulation of 186Re-labelled APD was found in bone, resulting in bone-to-blood ratios of 25, 35, 65, 100, 151, 181 and 189, respectively. 186Re-APD showed high uptake in bone, and relatively low uptake in soft tissue, suggesting that 186Re-APD is a potential agent for bone therapy.

Animals↗
PubMed1999

Accuracy of standardized uptake value measured by simultaneous emission and transmission scanning in PET oncology.

We assessed the accuracy of the standardized uptake value (SUV) measured by simultaneous emission and transmission scanning in cancer patients using FDG positron emission tomography (PET). Conventional, independent emission (E)/transmission (T) scans and simultaneous E/T scans were conducted consecutively in 30 patients who underwent FDG PET examinations. The SUVs of 35 mass lesions and 34 selected normal tissues were derived from the independent E/T scan and simultaneous E/T scan. Experimental studies using a cylindrical phantom were also conducted to evaluate the accuracy and reproducibility of the SUV derived from a simultaneous E/T scan. The SUVs of 18F solution in the phantom were estimated to be approximately 1, with high reproducibility in the range of total counts observed in the clinical examinations. There were no significant differences in the SUVs in 35 tumours derived from simultaneous E/T scans and those derived from independent scans, and there was a strong positive correlation between the two (r = 0.99, P < 0.01). There were also no significant differences in the SUVs in 34 normal tissue regions derived from simultaneous E/T scans and those derived from independent scans. In conclusion, simultaneous E/T scanning with FDG in patients with malignant tumours is a valid method, since the SUV derived from the simultaneous scan is accurate and reproducible.

Algorithms↗
PubMed1999

18F alpha-methyl tyrosine PET studies in patients with brain tumors.

UNLABELLED: We have developed 18F-labeled alpha-methyl tyrosine (FMT) for PET imaging. The aim of this study was to evaluate the clinical application potential of FMT for patients with brain tumors. METHODS: Eleven healthy volunteers and 20 patients with brain tumors were injected with 185 MBq (5 mCi) FMT. In 3 healthy volunteers, whole-body imaging and urinary and plasma analysis were conducted for the assessment of the biodistribution of FMT. The normal range of cortical standardized uptake value (SUV) as a reference for comparing tumor SUV of FMT was estimated by using PET data obtained at 30 min postinjection in 8 healthy volunteers. Dynamic PET scans were conducted for 100 min in 4 healthy volunteers and for 30 min in 15 patients with brain tumors. The 10-min static images in another 4 volunteers and all patients were obtained at 30 min postinjection. In 13 patients, FMT uptake in the brain tumor was compared with 18F-fluorodeoxyglucose (FDG). Tumor-to-normal cortex count (T/N) ratio and tumor-to-white matter count (T/W) ratio and SUVs of brain tumors were determined on FMT and FDG PET images. RESULTS: Approximately 1480 MBq (40 mCi) FMT were produced in one radiosynthesis. Percentage injected dose (%ID) of FMT in the brain ranged from 2.8% to 4.9%, and approximately 50%ID of FMT was excreted in urine during 60 min postinjection, of which 86.6% was unmetabolized FMT. A faint physiological brain uptake with SUV of 1.61 +/- 0.32 (mean +/- SD, n = 8) was observed in healthy volunteers. Tumor SUV of FMT ranged from 1.2 to 8.2, with mean value of 2.83 +/- 1.57 (n = 23), which was significantly higher than that of the cortical area in healthy volunteers (P < 0.01). T/N and T/W ratios of FMT were significantly higher than those of FDG (2.53 +/- 1.31 versus 1.32 +/- 1.46, P < 0.001; 3.99 +/- 2.10 versus 1.39 +/- 0.65, P < 0.0001, respectively). CONCLUSION: FMT, like other radiolabeled amino acids, can provide high-contrast PET images of brain tumors.

Adolescent↗
PubMed1998

In vitro effect of contrast agents during immunoradiometric assay for tumour-associated antigens.

The aim of this study was to investigate if contrast agents interfere with the performance of an immunoradiometric assay (IRMA) in vitro for serum tumour-associated antigen. Each of five carcinoembryonic antigen (CEA)-positive sera, CA-130-positive sera and tissue polypeptide antigen (TPA)-positive sera was mixed with six contrast agents: Ioversol 350, Iopamidol 370, Iomeprol 300, Iomeprol 400, Iohexol 300 and Gadopenteic acid in 50:50, 50:20, 50:5.0, 50:1.0, 50:0.5 and 50:0.1 microl proportions. Following IRMA, the interference of binding rates in each mixture was calculated, and the serum concentrations of CEA, CA-130 and TPA were estimated and compared with the originals. All contrast agents used were able to inhibit the binding rate with IRMA and the inhibition rates were in proportion to the amount of contrast agent. The detection of serum concentrations of CEA, CA-130 and TPA was significantly inhibited in the mixtures with more than 5.0 microl of contrast agent in all cases. Apart from Iomeprol 400, there was no significant inhibition of detection at the lowest concentrations of contrast agents. Iomeprol 400 was the strongest inhibitor and Gadopenteic acid the weakest inhibitor for each IRMA of the contrast agents employed. In conclusion, our results demonstrate that contrast agents may reduce the immunoreaction of antibody and antigen and lead to in vitro inhibition during immunoassays. It would be unwise to perform any plasma/serum immunoassay on a sample collected within 24 h of the administration of contrast agent considering the pharmacokinetics.

Aged↗
PubMed1998

Biodistribution studies on L-3-[fluorine-18]fluoro-alpha-methyl tyrosine: a potential tumor-detecting agent.

UNLABELLED: Iodine-123-alpha-methyl tyrosine has proven to be a promising SPECT agent for imaging amino acid uptake in tumors. We developed L-[3-(18)F]-alpha-methyl tyrosine (FMT) for PET studies. The aim of this study was to investigate its potential use as a tumor-detecting agent by using tumor-bearing mice. METHODS: We investigated the biodistribution in normal BALB/C mice and BALB/cA nude mice bearing human rectal cancer cell line (LS180) until 120 min postinjection. FMT tumor uptake at 60 min postinjection in mice with LS180 rectal cancer, RPM11788 B-cell lymphoma and MCF7 mammary cell carcinoma was assessed, and the results were compared with 18F-fluoro-2-deoxy-D-glucose (FDG) tumor uptake. The effect of competitive inhibition of large neutral amino acid transport system using unlabeled L-alanine was also investigated. RESULTS: The amount of FMT in blood fell to 1.05%ID/20 g at 60 min postinjection, whereas that in the pancreas was 15.2%ID/20 g, resulting in a high pancreas-to-blood ratio of 14.5. In other organs, initial uptake peaked at 5 min postinjection and then declined with time. In LS180 tumor-bearing mice, peak FMT uptake in tumor was observed at 60 min postinjection. Tumor-to-blood and tumor-to-muscle ratios ranged from 1.60 to 2.94 and from 2.79 to 3.25 over the 120-min observation period. Tumor uptake of FMT was clearly reduced by inhibition of the amino acid transport system. In mice with LS180 and MCF7 tumors, FMT tumor uptake at 60 min postinjection was significantly higher than FDG tumor uptake, whereas in RPM11788 lymphoma, uptake of FDG was significantly higher than FMT tumor uptake. Tumor-to-blood ratios of FMT in mice with LS180, RPMI1788 and MCF7 tumor at 60 min postinjection were 1.82, 5.88 and 3.56, respectively. CONCLUSION: FMT, like other fluorinated amino acids, may become a promising tumor-detecting agent for PET, assuming that efficient methods of radiosynthesis are developed.

Amino Acids↗
PubMed1998

Analysis of muscle bioenergetic metabolism in rabbit leg lengthening.

The effect of lengthening on muscle metabolism was measured and correlated to the percent lengthening at early and late time points. Using the rabbit tibial lengthening model, the authors examined the effects of lengthening on the tibialis anterior muscle using phosphorus-31 magnetic resonance spectroscopy. Thirty-six rabbits were divided into five groups, four groups by percent lengthening (0%, 15%, 20%, and 25%), with each group divided into subgroups of early (end distraction) and late (12 weeks after end distraction), and the fifth group using the opposite untreated leg as control. Several parameters measuring metabolism of muscle using phosphorus-31 magnetic resonance spectroscopy analysis were compared. No changes occurred to 15% lengthening, but significant decreases were measured at 20% and 25% lengthening. After a 25% lengthening, the decreased metabolism persisted at 12 weeks after distraction, indicating the possibility of permanent damage. After 20% lengthening, the same parameters improved but never to normal levels. The authors conclude that lengthening to 15% is safe for muscle, but 20% to 25% lengthening may result in permanent metabolic damage. The current study also suggests that phosphorus-31 magnetic resonance spectroscopy may provide a viable clinical method for evaluating muscle damage during lengthening.

Adenosine Triphosphate↗
PubMed1998

In vivo comparison of PET and SPECT radiopharmaceuticals in detecting breast cancer.

UNLABELLED: Various radiopharmaceuticals for breast cancer detection have been used for scintimammography and PET. However, few comparative studies have described the uptake of radiopharmaceuticals as a method of detecting breast cancer. The aim of this study was to assess the radiopharmaceuticals for breast cancer imaging in experimental mice implanted with breast cancer cells. METHODS: Six radiopharmaceuticals were studied: three for PET [18F-fluorodeoxyglucose (FDG), L-18F-alpha-methyltyrosine (FMT) and 11C-methionine (C-Met)] and three for scintimammography [99mTc-tetrofosmin (TF), 99mTc-sestamibi (MIBI) and 201Tl-chloride (Tl)]. Biodistributions of six different tracers in mice implanted with MCF-7 breast cancer cells were studied 1 and 3 hr after injection. RESULTS: Tumor uptake 1 hr after injection was FMT = C-Met > FDG = TF > MIBI = Tl. Thallium-201-chloride showed the highest tumor-to-blood ratio (T/B) among all radiopharmaceuticals because of its fast clearance from circulation. The T/B of the six radionuclides used in this study ranged from 1.26 for C-Met to 12.83 for Tl. Tumor-to-muscle ratio (T/M) revealed FMT = C-Met > FDG > MIBI > TF = Tl. The T/M ranged from 0.20 for TF to 2.29 for FMT. Tumor-to-lung ratio (T/L) varied from 0.45 for TF to 2.41 for FMT. FMT revealed the highest T/L of all six radiopharmaceuticals. CONCLUSION: Among radiopharmaceuticals for PET, FMT seemed to be suitable in detecting MCF-7 tumor; whereas for scintimammography, MIBI, TF and Tl appeared to have almost the same detectability of MCF-7 tumor. The results of this study strongly suggest that FMT may have a potential in breast cancer imaging.

Animals↗
PubMed1997

Preparation of yttrium-90-labeled human macroaggregated albumin for regional radiotherapy.

Human macroaggregated albumin (MAA), which is currently labeled with technetium-99m (99mTc) and 99mTc-MAA, is used clinically as a pulmonary perfusion agent and was directly labeled with yttrium-90 (90Y)-acetate. This study evaluated whether 90Y-MAA could be potential radiotherapeutic agent for regional radiotherapy against malignant tumors. MAA suspended in 0.1 M sodium acetate buffer, pH 5.8, was incubated with 90Y-acetate and purified in order to get rid of unstable binding of 90Y by electrophoresis. The radiochemical purity of 90Y-MAA in normal human serum was estimated by an agarose electrophoresis method and was more than 94% over 168 h in vitro. Following the intratumoral administration of 90Y-MAA, the time course of tumor radioactivity and the biodistribution in nude mice bearing human neuroblastoma were investigated up to 168 h. More than 93% of the radioactivity of the injected dose was found on the subcutaneous tumor over 168 h. The bone radioactivity was shown as 0.06 +/- 0.03% injection dose/gram tissue (% ID/g) (n = 5) at 24 h, 0.73 +/- 0.20% ID/g at 72 h, 0.92 +/- 0.16% ID/g at 120 h, and 2.51 +/- 0.59% ID/g at 168 h. A slight increase in radioactivity was noted in the liver, kidneys, and spleen over the 168-h periods. In conclusion, 90Y-MAA may be a potential agent for regional radiotherapy (brachytherapy) because of the sufficient persistence in the tumor following an intratumoral administration.

Albumins↗
PubMed1997

Synthesis of isomers of 18F-labelled amino acid radiopharmaceutical: position 2- and 3-L-18F-alpha-methyltyrosine using a separation and purification system.

To diagnose cancers with radiolabelled amino acid using positron emission tomography, we have constructed a separation and purification system for the production of L-18F-alpha-methyltyrosine (L-18FAmT). This system could provide radioprotection and consistent production of L-18FAmT. L-18FAmT was synthesized and purified and the efficiency of the system was examined. The radiochemical yield of L-18FAmT was 20.3 +/- 5.1% (n = 5) based on the radioactivity trapped in the reaction vessel. The radiochemical purity was greater than 99.4 +/- 0.3% (n = 5). The radiochemical stability in phosphate-buffered saline and human plasma was examined and little decomposition was observed by HPLC analysis. Our results indicate that the separation and purification system gave simple and quick synthesis of L-18FAmT with a large reduction in radiation exposure and consistent production of L-18FAmT.

Amino Acids↗